Imidazo[4,5-d]pyridazine compounds and conjugates thereof, their preparation, and their therapeutic applications

Abstract

The present invention relates to a compound of formula (I) A-L1-RCG1 (I) wherein A is of formula (A), R1 is H, an optionally substituted alkyl, alkenyl, alkynyl, R2 is halogen, alkyl; alkenyl; alkynyl; alkylthio; alkylthioalkyl; alkyl-S(O)-; alkyl-S(O2)-; alkyl-S(O)-alkyl-; alkyl-S(O2)-alkyl-; alkoxy; alkoxyalkyl; haloalkoxyalkyl; cycloalkyl-O-alkyl; alkyl-NH- alkyl; (alkyl)2-N-alkyl; alkyl-NH; and (alkyl)2N; R3 is deuterium; H, alkyl; alkenyl; alkynyl; alkylthio; -OR6, -NR7R8, heterocycloalkyl, heteroaryl, aryl, cycloalkyl; L1 is a linker, RCG1 is a reactive chemical group. The present invention also relates to a compound of formula A- L1-G-BA (II) wherein G is the product of reaction between RCG1 and a reactive group RCG2 and BA is a binding agent, a pharmaceutical composition comprising it and its therapeutic uses, for instance for treating cancer.

Description

[0001] IMIDAZO[4,5-d]PYRIDAZINE COMPOUNDS AND CONJUGATES THEREOF, THEIR PREPARATION, AND THEIR THERAPEUTIC APPLICATIONS

[0002] FIELD OF THE INVENTION

[0003] The present disclosure relates to new imidazo[4,5-d]pyridazine compounds (also named payloads), to new imidazo[4,5-d]pyridazine conjugates, to pharmaceutical compositions comprising these conjugates and to their therapeutic uses, for instance as TLR7 and / or 8 agonists. The present disclosure also relates to processes for preparing these pay loads and conjugates.

[0004] BACKGROUND OF THE INVENTION

[0005] Over the last decade, immunotherapy, mainly immune checkpoint inhibitor (ICI) has led to impressive clinical responses in patients. However, the percentage of ICI- responding patients remains low. It is noteworthy that ICI efficacy correlates with an “inflamed” tumor microenvironment (TME) and patients with “non-inflamed” tumors tend to respond poorly to ICI.

[0006] Therapeutic activation of TLR (Toll-like Receptor) such as TLR7 and / or 8 shows potential for immunotherapy, by converting non-inflamed or poorly inflamed tumors into immunologically inflamed tumors and (re)initiating T-cell mediated anti-tumor immune response. The innate immune system contains several families of germline-encoded pattern recognition receptors (PRRs), including Toll-like receptors (TLRs). These receptors recognize danger signals from either released intra-cellular components termed damage- associated molecular pattern (DAMP) or microbial components termed pathogen-associated molecular patterns (PAMPs). The PAMPs are highly conserved molecular structures on a wide range of pathogens such as viruses, fungi, bacteria, and parasites. TLR7 and TLR8 are both located within endo-lysosomes and play an important role in the immune response during viral infection by their ability to recognize single stranded RNA PAMPs, as well as synthetic small molecules. Their stimulation leads to intracellular signaling and downstream activation of genes coding, among others for co- stimulatory molecules, pro-inflammatory cytokines and type I interferons. The activation of TLR such as TLR7 and / or TLR8, by an agonist can induce secretion of type I interferons such as IFNα and IFNβ, tumor necrosis factor (TNFα) and interleukins such as IL6, IL12, which are important actors in the initiation of innate and adaptative immunity. For example, the activation of TLR7 may preferentially stimulate immune stimulating cytokines release such as IFNα and IP10 whereas the activation of TLR8 may preferentially stimulate pro-inflammatory cytokines release such as IL6 and TNFα. The secretion of these cytokines, associated with the expression of co- stimulatory molecules, are known to induce the maturation of dendritic cells, monocytes and macrophages, facilitating the presentation of antigen and the stimulation of the adaptive immune response. Various small molecules agonists of TLR7 (commonly named TLR7 agonists) and / or agonists of TLR8 (commonly named TLR8 agonists) have already been described as potent antitumoral compounds. For example, imidazoquinoline compounds such as Imiquimod (R-837, a TLR7 agonist) and Resiquimod (R-848, also named R848, a TLR7 and 8 agonist, as named TLR7 / 8 agonist) are developed for local administrations (topical and / or intratumoral) due to tolerability issues in systemic administration. Current intra-tumoral delivery approaches demonstrate poor tumor retention, limiting anti-tumor benefit and promoting treatment-related adverse events. For example, the Seven and Eight BDB-001, an intravenously administered TLR7 / 8 agonist in combination with Pembrolizumab in advanced solid tumors, shows activities but also treatment-related adverse events in around 78% of the enrolled patients under monotherapy (Journal of Clinical Oncology 2021 39:15_suppl, 2512-2512). TLR7 and / or 8 agonists conjugated to antibody for intravenous tumor-targeted delivery have recently been described. Some conjugates have been under development and discontinued mainly due to not favorable therapeutical index or toxicity. WO2018 / 009916 discloses imidazoquinoline or imidazopyrimidine compounds as TLR7 and / or 8 agonists for immunoconjugates. BDC-1001, an imidazoquinoline TLR7 / 8 agonist conjugated to an anti-Her2 antibody with a non-cleavable linker showed a safe profile with biomarkers consistent with the mechanism of action in phase 1 but has been discontinued in phase 2 due to low efficacy. WO2023 / 057564 discloses imidazoquinoline R848 conjugates with non- cleavable linkers. All disclosed ADCs (antibody-drug conjugates), especially a R848 agonist conjugated to an anti-CEACAM5 antibody with a PEG24 linker (Tusamitamab-R848 ADC, also named in the present disclosure Tusa-R848), have been discontinued in pre-clinical stage due to a narrow therapeutic index. The formula of Tusa-R848 is as follows: WO2017 / 072662 discloses pyrrolo-pyrimidine compounds as TLR7 agonists for immunoconjugates. NJH395 (a TLR7 agonist conjugated to an anti-HER2 antibody) has been discontinued in Phase 1 for toxicity reasons (low grade CRS, meningitis / gism, hepatotoxicity). SBT-6050 (a TLR8 agonist conjugated to an anti-HER2 antibody) and SBT- 6290 (a TLR8 agonist conjugated to an anti-Nectin4 antibody) have been also stopped in phase 1 for toxicity (low grade CRS, hypotension). Therefore, there remains a need for new immunotherapies based on TLR7 and / or 8 agonists with less adverse - events and / or better therapeutic index for the treatment of diseases, in particular cancer. The purpose of the disclosure is to provide new immune-stimulating compounds suitable for systemic delivery, well tolerated and presenting less adverse-effects. The present disclosure describes new TLR7 and / or 8 payloads compounds suitable for conjugation with an antibody and immunostimulant-conjugates thereof. The present disclosure describes also immunostimulant-conjugate with a particular cytokine profile. SUMMARY OF THE INVENTION The present disclosure relates to a compound (also named payload or compound / payload in the present text) of formula (I) or a pharmaceutically acceptable salt thereof: A-L1-RCG1 (I) wherein: - A is a drug unit of formula (A) wherein: R1 represents: - a hydrogen atom, or - a group selected from: a) - a (C1-C6)alkyl- group; - a hydroxy-(C1-C6)alkyl- group; - a NH2-(C1-C6)alkyl- group; - a NH-(C1-C6)alkyl-(C1-C6)alkyl- group; - a N((C1-C6)alkyl)2-(C1-C6)alkyl- group; - a (C2-C6)alkenyl- group; - a (C2-C6)alkynyl- group; b) - a phenyl(C1-C6)alkyl- group being unsubstituted or substituted by at least one substituent selected from: b1) - a (C1-C6)alkoxy- group; b2) - a hydroxyl group; b3) a -C(O)-H group; and b4) - a (C1-C6)alkyl- group being unsubstituted or substituted by at least one substituent selected from: b4.1) - a hydroxyl group; and b4.2) - a -NR4R5 group wherein R4 and R5, being independently from each other selected from: b4.2.1) - a hydrogen atom; b4.2.2) - a (C1-C16)alkyl- group; b4.2.3) - a CH3-[O-(CH2)2]n- group with n being an integer from 1 to 30, a (C1-C6)alkoxy(C1-C6)alkyl- group, or a (C1-C6)alkoxy(C1-C6)alkoxy(C1-C6)alkyl- group; b4.2.4) - a (C1-C6)alkyl-S(O2)- group; b4.2.5) - a (C1-C6)alkyl-NH-C(O)- group; b4.2.6) - a (C1-C16)alkyl-C(O)- group; b4.2.7) - a (C1-C16)alkyl-O-C(O)- group; b4.2.8) - a CH3-[O-(CH2)2]n-C(O)- group with n being an integer from 1 to 30; b4.2.9) - a (C3-C10)cycloalkyl- group being unsubstituted or substituted by at least one substituent selected from: - a hydroxyl group; and - a (C1-C6)alkyl- group; or b4.2.10) - a (C3-C10)membered heterocycloalkyl- group comprising from one to four heteroatoms selected from oxygen, nitrogen, sulfur, -S(O)- and -SO2-; b4.2.11) - a phenyl-C(O)- group; b4.2.12) - a (C1-C6)alkoxy-phenyl-(C1-C6)alkyl-O-C(O)- group; b4.2.13) - a (C1-C16)alkyl-C(O)-NH-phenyl-(C1-C6)alkyl-O-C(O)- group; b4.2.14) - a (C1-C16)alkyl-O-C(O)-(C1-C6)alkyl- group; or R4and R5form together with the nitrogen atom to which they are attached a (C3-C10)membered heterocycloalkyl- group comprising one to four heteroatoms selected from oxygen, nitrogen and sulfur, said (C3-C10)membered heterocycloalkyl- group being unsubstituted or substituted by at least one substituent selected from a (C1-C6)alkyl- group, and a CH3-[O-(CH2)2]n- group with n being an integer from 1 to 30; c) - a (C3-C10)cycloalkyl(C1-C6)alkyl- group being unsubstituted or substituted by at least one substituent selected from -NH2and a NH2-(C1-C6)alkyl- group; d) - a (C3-C10)membered heterocycloalkyl(C1-C6)alkyl- group comprising one to four heteroatoms selected from oxygen, nitrogen, and sulfur, said heterocycloalkyl group being unsubstituted or substituted by at least one substituent selected from a (C1-C6)alkyl- group and a CH3-[O-(CH2)2]n- group with n being an integer from 1 to 30; and e) - a (C5-C10)membered heteroaryl(C1-C6)alkyl- group comprising one to four heteroatoms selected from oxygen, nitrogen, and sulfur, said heteroaryl being unsubstituted or substituted by at least one substituent selected from: - a (C1-C6)alkyl- group; - a NH2-(C1-C6)alkyl- group and - a cyano group; f) - a (C3-C10)membered heterocycloalkyl-NH-(C1-C16)alkyl- group, said heterocycloalkyl group comprising one to four heteroatoms selected from oxygen, nitrogen, S(O), SO2and sulfur; g) - a (C3-C10)membered heterocycloalkyl-N(C(O)-(C1-C6)alkyl)-(C1-C16)alkyl- group, said heterocycloalkyl group comprising one to four heteroatoms selected from oxygen, nitrogen, S(O), SO2 and sulfur; R2 represents a halogen atom, or a group selected from: - a (C1-C6)alkyl- group; - a (C2-C6)alkenyl- group; - a (C2-C6)alkynyl- group; - a (C1-C6)alkylthio- group; - a (C1-C6)alkylthio(C1-C6)alkyl- group; - a (C1-C6)alkyl-S(O)- group; - a (C1-C6)alkyl-S(O2)- group; - a (C1-C6)alkyl-S(O)-(C1-C6)alkyl- group; - a (C1-C6)alkyl-S(O2)-(C1-C6)alkyl- group; - a (C1-C6)alkoxy- group; - a (C1-C6)alkoxy(C1-C6)alkyl- group; - a (C1-C6)haloalkoxy(C1-C6)alkyl- group; - a (C3-C5)cycloalkyl-O-(C1-C6)alkyl- group; - a (C1-C6)alkyl-NH-(C1-C6)alkyl- group; - a ((C1-C6)alkyl)2-N-(C1-C6)alkyl- group; - a (C1-C6)alkyl-NH- group; and - a ((C1-C6)alkyl)2N- group; R3 represents: - a deuterium atom; - a hydrogen atom or a group selected from: a) - a (C1-C6)alkyl- group; - a (C2-C6)alkenyl- group; - a (C2-C6)alkynyl- group; and -a (C1-C6)alkylthio- group; b) - a -OR6group wherein R6is selected from: - a hydrogen atom; - a (C1-C6)alkyl- group; - a CH3-[O-(CH2)2]n- group with n being an integer from 1 to 30; - a (C2-C6)alkenyl- group; - a (C2-C6)alkynyl- group; - a (C3-C10)cycloalkyl- group; - a phenyl group; - a phenyl(C1-C6)alkyl- group; and - a (C3-C10)membered heterocycloalkyl- group comprising one to four heteroatoms selected from oxygen, nitrogen, sulfur, -S(=O)- and -S(=O)2-; c) - a -NR7R8 group wherein R7 and R8 being, independently from each other, selected from: - a hydrogen atom; - a CH3-[O-(CH2)2]n- with n being an integer from 1 to 30; - a (C1-C6)alkyl- group unsubstituted or substituted by - a (C5-C10)membered heteroaryl group comprising one to four heteroatoms selected from oxygen, nitrogen and sulfur; or - a phenyl group being unsubstituted or substituted by at least one substituent selected from: - a cyano group and - a NR9R10-(C1-C6)alkyl- group wherein: R9 and R10 being, independently from each other, selected from: - a hydrogen atom; - a (C1-C6)alkyl- group; - a CH3-[O-(CH2)2]n- with n being an integer from 1 to 30, or R9 and R10 together form with the nitrogen atom to which they are attached a (C3-C10)membered heterocycloalkyl- group comprising one to four heteroatoms selected from oxygen, nitrogen, and sulfur, said (C3-C10)membered heterocycloalkyl group being unsubstituted or substituted by at least one substituent selected from a (C1-C6)alkyl- group, and a CH3-[O-(CH2)2]n- group with n being an integer from 1 to 30; or R7and R8form together with the nitrogen atom to which they are attached a (C3-C10)membered heterocycloalkyl- group comprising one to four heteroatoms selected from oxygen, nitrogen, and sulfur, said heterocycloalkyl group being unsubstituted or substituted by at least one substituent selected from: - a phenyl group and - a hydroxy(C1-C6)alkyl-phenyl- group; d) - a (C3-C10)membered heterocycloalkyl- group comprising one to four heteroatoms selected from oxygen, nitrogen and sulfur; e) - a (C5-C10)membered heteroaryl- group comprising one to four heteroatoms selected from oxygen, nitrogen, and sulfur, said (C5-C10)membered heteroaryl- group being unsubstituted or substituted by at least one (C1-C6)alkyl- group; f) - a (C6-C10)membered aryl- group; and g) - a (C3-C10)cycloalkyl- group; - L1 represents a linker; and - RCG1 represents a reactive chemical group that is reactive towards a chemical group present on a binding agent, for instance on a protein, a polypeptide, a ligand, a peptide, an oligonucleotide or an oligosaccharide, for instance on a targeting agent for instance on a cell- binding agent such as an antibody such as a monoclonal antibody or a VHH antibody. The present disclosure further relates to a compound (also named conjugate or compound / conjugate in the present text) of formula (II) or a pharmaceutically acceptable salt thereof: A-L1-G-BA (II) wherein: A, and L1 are as defined in the present disclosure; BA represents a binding agent for instance a protein, a polypeptide, a ligand, a peptide, an oligonucleotide or an oligosaccharide, for instance BA is a targeting agent for instance a cell-binding agent such as an antibody, such as a monoclonal antibody or a VHH antibody; G represents the product of reaction between RCG1 as defined in the present disclosure and RCG2, a reactive group present on the binding agent, for instance G is selected from the group consisting of:

[0007] , for instance, the left side of the G groups being linked to the binding agent, for instance a protein, a polypeptide, a ligand, a peptide, an oligonucleotide or an oligosaccharide, for instance a targeting agent for instance a cell-binding agent such as an antibody (Ab) such as a monoclonal antibody or a VHH antibody, for instance an antibody (Ab), and the right side of the G groups being linked to L1, for instance G represents the following groups:

[0008] . The compounds of formulae (I) and (II) may be present as well under tautomer forms. Indeed, it is to be understood that the present disclosure encompasses all isomers of formulae (I) and (II) and their pharmaceutically acceptable derivatives, including all geometric, tautomeric and mixtures thereof. In the context of the present disclosure, the compounds of formula (I) include the compounds of formula (I1) and (I2) as defined in the present disclosure. In the context of the present disclosure, the compounds of formula (II) include the compounds of formula (II1) and (II2) as defined in the present disclosure. The compound / payload of formula (I) may exist in the form of bases or addition salts with acids or bases, in particular pharmaceutically acceptable salts. Pharmaceutically acceptable salts of the compound / payload of formula (I) do form part of the disclosure. The compound / payload of formula (I) may exist in the form of bases, acids, zwitterion or of addition salts with acids or bases. Such addition salts, bases, acids and zwitterion form part of the disclosure. Hence, the disclosure relates, inter alia, to the compound / payload of formula (I), or to pharmaceutically acceptable salts thereof. These salts may be prepared with pharmaceutically acceptable acids or bases, although the salts of other acids or bases useful, for example, for purifying or isolating the compound / payload of formula (I), also form part of the disclosure. The present disclosure also relates to processes for the preparation of the compounds / conjugates of formula (II) in accordance with the present disclosure. Thus, according to one specific embodiment, the disclosure relates to a process for preparing a compound / conjugate of formula (II) as defined in the present disclosure comprising at least the steps of: (i) placing in contact and leaving to react: - an, optionally buffered, aqueous solution of a binding agent for instance a protein, a polypeptide, a ligand, a peptide, an oligonucleotide or an oligosaccharide, for instance a targeting agent for instance a cell-binding agent such as an antibody (Ab) such as a monoclonal antibody or a VHH antibody, comprising a reactive RCG2 group, optionally modified by means of a modifying agent, and - a solution of a compound / payload of formula (I) as defined in the present disclosure, comprising a reactive RCG1 group, RCG1 groups of compound / payload of formula (I) being reactive towards the RCG2 groups of the binding agent for instance a protein, a polypeptide, a ligand, a peptide, an oligonucleotide or an oligosaccharide, for instance a targeting agent for instance a cell- binding agent such as an antibody (Ab) such as a monoclonal antibody or a VHH antibody to form the G group by a covalent bond and forming the compound / conjugate of formula (II); (ii) and then optionally separating the compound / conjugate of formula (II) formed in step (i) from the unreacted compound / payload of formula (I) and / or from the unreacted binding agent for instance a protein, a polypeptide, a ligand, a peptide, an oligonucleotide or an oligosaccharide, for instance a targeting agent for instance a cell-binding agent such as an antibody (Ab) such as a monoclonal antibody or a VHH antibody and / or from any aggregates that may have been formed. Another subject matter of the instant disclosure is a compound / conjugate of formula (II) in accordance with the disclosure selected from the above and below definitions / lists, or a pharmaceutically acceptable salt thereof, for use as a medicine. Another subject matter of the instant disclosure is a compound / conjugate of formula (II) in accordance with the disclosure selected from the above and below definitions / lists, or a pharmaceutically acceptable salt thereof, for use in therapy, especially as a TLR7 and / or 8 agonists. Another subject matter of the instant disclosure is a compound / conjugate of formula (II) in accordance with the disclosure selected from the above and below definitions / lists, or a pharmaceutically acceptable salt thereof, for use to induce high amount of immune stimulating cytokines with low or no pro-inflammatory cytokines, for use to stimulate the cytokine induction of IFNα and IP10 with low or no stimulation of IL6 and TNFα, in particular wherein IFNα / TNFα ratio is higher than 1. Another subject matter of the instant disclosure is a compound / conjugate of formula (II) in accordance with the disclosure selected from the above and below definitions / lists, or a pharmaceutically acceptable salt thereof, for use in the prevention and / or treatment of a disease or a disorder that may benefit of an activation of the immune system for instance for use in the prevention and / or treatment of a cell-proliferative disease, a cancer, a chronic myelogenous, a hairy cell leukemia, a dermatological disease such as a skin lesion or a skin cancer (for example an external genital and perianal warts / condyloma acuminate, a genital herpes, an actinic keratosis, a basal cell carcinoma, a cutaneous T-cell lymphoma), an autoimmune disease, an inflammatory disease, a respiratory disease, a sepsis, an allergy (for example an allergic rhinitis or a respiratory allergy), an asthma, a graft rejection, a graft-versus-host disease, and an immunodeficiency, for instance in the prevention and / or in the treatment of cancers. Another subject matter of the instant disclosure is a compound / conjugate of formula (II) in accordance with the disclosure selected from the above and below definitions / lists, or a pharmaceutically acceptable salt thereof, for use in the prevention and / or treatment of a cancer. Another subject matter of the instant disclosure is a compound / conjugate of formula (II) in accordance with the disclosure selected from the above and below definitions / lists, or a pharmaceutically acceptable salt thereof, for use as anticancer agents. Another subject matter of the instant disclosure is a compound / conjugate of formula (II) in accordance with the disclosure selected from the above and below definitions / lists, or a pharmaceutically acceptable salt thereof, for use in an anti-tumoral vaccine. Another subject matter of the instant disclosure is a method of preventing and / or treating a disease or a disorder that may benefit of an activation of the immune system, for instance of preventing and / or treating a cell-proliferative disease, a cancer, a chronic myelogenous, a hairy cell leukemia, a dermatological disease such as a skin lesion or a skin cancer (for example an external genital and perianal warts / condyloma acuminate, a genital herpes, an actinic keratosis, a basal cell carcinoma, a cutaneous T-cell lymphoma), an autoimmune disease, an inflammatory disease, a respiratory disease, a sepsis, an allergy (for example an allergic rhinitis or a respiratory allergy), an asthma, a graft rejection, a graft- versus-host disease, and an immunodeficiency, which comprises administering to a subject in need thereof, for instance a human, a therapeutically effective amount of a compound / conjugate of formula (II) in accordance with the disclosure selected from the above and below definitions / lists, or a pharmaceutically acceptable salt thereof. The present disclosure also relates, in another aspect, to a method of preventing a disease or a disorder that may benefit of an activation of the immune system, for instance of preventing a cell-proliferative disease, a cancer, a chronic myelogenous, a hairy cell leukemia, a dermatological disease such as a skin lesion or a skin cancer (for example an external genital and perianal warts / condyloma acuminate, a genital herpes, an actinic keratosis, a basal cell carcinoma, a cutaneous T-cell lymphoma), an autoimmune disease, an inflammatory disease, a respiratory disease, a sepsis, an allergy (for example an allergic rhinitis or a respiratory allergy), an asthma, a graft rejection, a graft-versus-host disease, and an immunodeficiency, in a patient in need thereof, for instance a human, which comprises immunizing said patient with a vaccine comprising a compound / conjugate of formula (II) in accordance with the disclosure selected from the above and below definitions / lists, or a pharmaceutically acceptable salt thereof. The present disclosure also relates, in another aspect, to an anti-tumoral vaccine. The present disclosure further relates to the use of a compound / conjugate of formula (II) in accordance with the disclosure selected from the above and below definitions / lists, or a pharmaceutically acceptable salt thereof, for the manufacture of an antitumoral vaccine and / or of a medicament for preventing and / or treating a disease or a disorder that may benefit of an activation of the immune system, for instance for preventing and / or treating a cell-proliferative disease, a cancer, a chronic myelogenous, a hairy cell leukemia, a dermatological disease such as a skin lesion or a skin cancer (for example an external genital and perianal warts / condyloma acuminate, a genital herpes, an actinic keratosis, a basal cell carcinoma, a cutaneous T-cell lymphoma), an autoimmune disease, an inflammatory disease, a respiratory disease, a sepsis, an allergy (for example an allergic rhinitis or a respiratory allergy), an asthma, a graft rejection, a graft-versus-host disease, and an immunodeficiency, for instance a cancer. Another subject matter of the instant disclosure is a medicament comprising as active principle an effective dose of a compound / conjugate of formula (II) in accordance with the disclosure selected from the above and below definitions / lists, or a pharmaceutically acceptable salt thereof. Another subject matter of the instant disclosure is a medicament comprising a compound / conjugate of formula (II) in accordance with the disclosure selected from the above and below definitions / lists, or a pharmaceutically acceptable salt thereof. Another subject matter of the instant disclosure is a pharmaceutical composition comprising as active principle an effective dose of a compound / conjugate of formula (II) in accordance with the disclosure selected from the above and below definitions / lists, or a pharmaceutically acceptable salt thereof, and at least one pharmaceutically acceptable excipient. Another subject matter of the instant disclosure is a pharmaceutical composition comprising a compound / conjugate of formula (II) in accordance with the disclosure selected from the above and below definitions / lists, or a pharmaceutically acceptable salt thereof, and at least one pharmaceutically acceptable excipient. Definitions In the context of the present disclosure, the terms below have the following definitions unless otherwise mentioned throughout the instant specification: - a “halogen atom”: a fluorine, a chlorine, a bromine or an iodine atom, and for example a fluorine and a chlorine atom; - a “hydroxyl group”: a “-OH” group; - an “oxo group”: a “=O” group; - a nitro group: a “-NO2” group; - a “cyano group”: a “-C≡N” group; - a “(Cx-Cy)alkyl” group: a linear or branched saturated hydrocarbon-based aliphatic group comprising from x to y carbon atoms, for example from 1 to 6 carbon atoms, or from 1 to 16 carbon atoms. By way of examples, mention may be made of, but not limited to: methyl, ethyl, propyl, n-propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, hexyl, isohexyl, octyl, nonyl, decyl groups, and the like; - a “(Cx-Cy)alkenyl” group: a linear or branched hydrocarbon-based aliphatic group comprising at least one unsaturation (double bond) and comprising, from x to y carbon atoms (x being an integer of at least 2), for example from 2 to 6 carbon atoms. By way of examples, mention may be made of, but not limited to: ethenyl, propenyl, butenyl, pentenyl, hexenyl groups, and the like; - a “(Cx-Cy)alkynyl” goup: a linear or branched hydrocarbon-based aliphatic group comprising at least one triple bond and comprising from x to y carbon atoms (x being an integer of at least 2) for example from 2 to 6 carbon atoms. By way of examples, mention may be made of, but not limited to: ethynyl, propynyl, butynyl, pentynyl, hexynyl groups, and the like; - a “(Cx-Cy)alkoxy” group: an -O-alkyl group where the alkyl group is as previously defined. For example, a (C1-C6)alkoxy group. By way of examples, mention may be made of, (but not limited to: methoxy, ethoxy, propoxy, isopropoxy, linear, secondary or tertiary butoxy, isobutoxy, pentoxy, hexyloxy, heptyloxy, octyloxy, nonyloxy, decyloxy groups, and the like; -a “(Cx-Cy)haloalkoxy” group: an -O-alkyl group where the alkyl group is as previously defined and is further substituted by at least one halogen atom as previously defined. For example, a (C1-C6)haloalkoxy group. By way of examples, mention may be made of but not limited to: chloromethoxy, fluoromethoxy, dichloromethoxy, 2-fluoropropoxy groups, and the like; - a “(Cx-Cy)alkythio” group: an -S-alkyl group where the alkyl group is as previously defined. For example, a (C1-C6)alkylthio group. By way of examples, mention may be made of but not limited to: methylthio, ethylthio, propylthio, isopropylthio, linear, secondary or tertiary butylthio, isobutylthio, pentylthio, hexylthio, heptylthio, octylthio, nonylthio, decylthio groups, and the like; - a “(C3-C10)cycloalkyl” group or a “(C3-C5)cycloalkyl” group: a cyclic alkyl group comprising, unless otherwise mentioned, from 3 to 10 carbon atoms (noted “(C3- C10)cycloalkyl group”) or from 3 to 5 carbon atoms (noted “(C3-C5)cycloalkyl group”), saturated or partially unsaturated and unsubstituted or substituted. By way of examples, mention may be made of, but not limited to: cyclopropyl, cyclobutyl, cyclopentyl, cyclobutenyl, cyclopentenyl, cyclohexenyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl groups and the like; - a “(C3-C10)heterocycloalkyl” group: a monocyclic alkyl group comprising, unless otherwise mentioned, from 3 to 10 carbon atoms (noted “a (C3-C10) membered heterocycloalkyl group”) and comprising 1 to 4 heteroatoms selected from oxygen, nitrogen, sulfur , -S(O)-, and -SO2- (in other terms, one heteroatom replaces one carbon atom). Such heterocycloalkyl group may be saturated or partially saturated and unsubstituted or substituted. By way of examples of heterocycloalkyl groups, mention may be made of, but not limited to: piperazine, morpholino, pyrrolidine, tetrahydropyrane, thietane dioxide, piperidine, thiolane, thiolane oxide, thiolane dioxide, dihydrofurane, tetrahydrofurane, azetidine, oxetane, thietane, 2H-pyrrole, 1H-, 2H- or 3H-pyrroline, tetrahydrothiophene, oxadiazole and for example 1,3,4-oxadiazole or 1,3,5-oxadioazole, thiadiazole and for example 1,3,4-thiadiazole, isoxazoline, 2- or 3-pyrazoline, pyrroline, pyrazolidine, imidazoline, imidazolidine, thiazolidine, isooxazoline, isoxazolidine, dioxalane, oxathiazole, oxathiadiazole, dioxazole groups and the like; - a “(C5-C10)heteroaryl” group means: a cyclic aromatic group comprising from 5 to 10 carbon atoms and comprising from 1 and 4 heteroatoms selected from nitrogen, oxygen and sulfur (noted “a (C5-C10) membered heteroaryl group”) (in other terms, one heteroatom replaces one carbon atom). Such heteroaryl group may be unsubstituted or substituted. By way of examples of 5 to 10-membered heteroaryl groups, mention may be made of, but not limited to: pyridine, furan, pyrrole, thiophene, pyrazole, oxazole, isoxazole, triazole, tetrazole, oxadiazole, furazan, thiazole, isothiazole, thiadiazole, imidazole, pyrimidine, pyridazine, triazine groups and the like; - a “(C6-C10)aryl” group: a cyclic aromatic group comprising from 6 to 10 carbon atoms (noted “a (C6-C10) membered aryl group”). Such aryl group may be unsubstituted or substituted. By way of examples of 6 to 10-membered aryl groups, mention may be made of, but not limited to: phenyl, naphthyl groups, and the like; - a “deuterium atom” (D or2H) is a stable, non-radioactive isotope of hydrogen and has an atomic weight of 2.0144; - a “hydroxyl protecting group” means: Ethers, Silyl Ethers, Esters, carbonates, carbamates etc, such as Acetyl (Ac), Benzoyl (Bz), Benzyl (Bn), β-methoxyethoxymethyl ether (MEM), dimethoxytrityl, [bis-(4-methoxyphenyl)phenylmethyl] (DMT), methoxymethyl ether (MOM), methoxytrityl [(4-methoxyphenyl)diphenylmethyl] (MMT), p-methoxybenzyl ether (PMB), p-methoxyphenyl ether (PMP), methylthiomethyl ether, pivaloyl (Piv), tetrahydropyranyl (THP), tetrahydrofuran (THF), trityl (triphenylmethyl, Tr), silyl ether (for instance trimethylsilyl (TMS), tert-butyldimethylsilyl (TBDMS), tri-iso- propylsilyloxymethyl (TOM), and triisopropylsilyl (TIPS) ethers), methyl ethers, ethoxyethyl ethers (EE), for instance acetyl (Ac), benzyl (Bn), β-methoxyethoxymethyl ether (MEM), dimethoxytrityl, [bis-(4-methoxyphenyl)phenylmethyl] (DMT), p- methoxybenzyl ether (PMB), tetrahydropyranyl (THP), trityl (triphenylmethyl, Tr), trimethylsilyl (TMS), and tert-butyldimethylsilyl (TBDMS).(see the manual Greene’s protective groups in organic synthesis», P.G.M. WUTS and T.W. GREENE, fourth edition, 1807 Wiley 207, Wiley Interscience); - an “amino protecting group” means: carbamates, amides, alkyls, enamines, imides, imines, etc, such as carbobenzyloxy (Cbz) group, p-methoxybenzyl carbonyl (Moz or MeOZ) group, tert-butyloxycarbonyl (BOC) group, 9-fluorenylmethyloxycarbonyl (Fmoc) group, acetyl (Ac) group, benzoyl (Bz) group, benzyl (Bn) group, carbamate group, p- methoxyphenyl (PMP) group, tosyl (Ts) group, p-methoxybenzyl (PMB), 3,4- dimethoxybenzyl (DMPM), Troc (trichloroethyl chloroformate) group, other sulfonamides, for instance carbobenzyloxy (Cbz) group, tert-butyloxycarbonyl (BOC) group, 9- fluorenylmethyloxycarbonyl (Fmoc) group, acetyl (Ac) group, benzoyl (Bz) group, p- methoxybenzyl (PMB), 3,4-dimethoxybenzyl (DMPM), Troc (trichloroethyl chloroformate) group. (see the manual Greene’s protective groups in organic synthesis», P.G.M. WUTS and T.W. GREENE, fourth edition, 1807 Wiley 207, Wiley Interscience; - a “carboxylic acid protecting group” means : Esters, silyl esters, amides, hydrazides, etc such as methyl esters, benzyl esters, tert-butyl esters, allyl esters, esters of 2,6-disubstituted phenols (e.g. 2,6-dimethylphenol, 2,6-diisopropylphenol, 2,6-di-tert-butylphenol), silyl esters, orthoesters, oxazoline, for instance, methyl esters and benzyl esters. (see the manual Greene’s protective groups in organic synthesis», P.G.M. WUTS and T.W. GREENE, fourth edition, 1807 Wiley 207, Wiley Interscience); - an “aldehyde protecting group” or a ketone protecting group (also named carbonyl protecting groups) means: acetals and ketals, dithio acetals and ketals, substituted hydrazones, oximes, etc, such as acetals and ketals, acylals and dithianes. (see the manual Greene’s protective groups in organic synthesis», P.G.M. WUTS and T.W. GREENE, fourth edition, 1807 Wiley 207, Wiley Interscience); - a “leaving group” means: an atom or group of atoms that detaches from the main or residual part of a substrate during a reaction or elementary step of a reaction; - a “zwitterion” means: a globally neutral molecule with a positive and a negative electrical charge and having an acid group and a basic group; - “room temperature” (also named rt) in the present disclosure means a temperature ranging from 18°C to 30°C, for example from 18°C to 25°C; - A “self-immolative linker” or “self-immolative spacer” is a covalent assembly tailored to correlate the cleavage of two chemical bonds after activation of a protective part in a precursor (A.G. Gavriel et al., Polym. Chem. 2022, 13, 3188; A. Alouane et al., Angew. Chem. Int. Ed. 2015, 54, 7492 – 7509). For instance among the self-immolative linkers suitable for the present disclosure may be cited a *-C(O)-O-(CR14R15)-aryl-NR16-** group, *-C(O)-O-(CR14R15)-heteroaryl-NR16-** group, a *-C(O)-NR17-(C2-C6)alkyl-NR18-**, a *- C(O)-NR17-(C2-C6)alkyl-NR18-C(O)-O-CR15R14-aryl-NR16-** group, a *-C(O)-NR17-(C2- C6)alkyl-NR18-C(O)-O-CR15R14-heteroaryl-NR16-** group, a *-CR15R14-aryl-NR16-** group or a *-CR15R14-heteroaryl-NR16-** group, aryl being a (C6-C10) membered aryl group and heteroaryl being a (C5-C10) membered heteroaryl group comprising one to four heteroatoms selected from oxygen, nitrogen and sulfur, for instance a *-C(O)-O-CH2- phenyl-NH-** group, the single asterisk (*) indicating the site of covalent attachment to the A drug unit radical and the double asterisk (**) indicating the site of covalent attachment to the (AA)w radical; R14, R15, R16, R17and R18being a hydrogen atom or a (C1-C6)alkyl group; - “PEG”: polyethylene glygol, PEGn means, a -(CH2-CH2-O)nportion wherein n represents an integer from 1 to 30, for instance from 2 to 29, such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 26, 27, 28 and 29; - “TLR”: the terms "Toll-like receptor" and "TLR" refer to any member of a family of highly conserved mammalian proteins which recognize pathogen-associated molecular patterns and act as key signaling elements in innate immunity. TLR polypeptides share a characteristic structure that includes an extracellular domain that has leucine-rich repeats, a transmembrane domain, and an intracellular domain that is involved in TLR signaling; - “TLR7”: the terms "Toll-like receptor 7" and "TLR7" refer to nucleic acids or polypeptides sharing at least 70%; at least 80%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or more sequence identity to a publicly available TLR7 sequence, e.g., GenBank accession number AAZ99026 for human TLR7 polypeptide, or GenBank accession number AAK62676 for murine TLR7 polypeptide; - “TLR8”: the terms "Toll-like receptor 8" and "TLR8" refer to nucleic acids or polypeptides sharing at least 70%; at least 80%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or more sequence identity to a publicly available TLR8 sequence, e.g., GenBank accession number AAZ95441 for human TLR8 polypeptide, or GenBank accession number AAK62677 for murine TLR8 polypeptide; - “TLR agonist”: it is a substance that binds, directly or indirectly, to a TLR (e.g., TLR7 and / or TLR8) to induce TLR signaling. Any detectable difference in TLR signaling can indicate that an agonist stimulates or activates a TLR. Signaling differences can be manifested, for example, as changes in the expression of target genes, in the phosphorylation of signal transduction components, in the intracellular localization of downstream elements such as NF-kB, in the association of certain components (such as IRAK) with other proteins or intracellular structures, or in the biochemical activity of components such as kinases (such as MAPK). TLR7 agonists more effectively induces IFNα and IFN-regulated immune- stimulating cytokines such as IP10. TLR8 agonists more effectively induce pro- inflammatory cytokines related to NF-kB-pathway such as TNFα and IL6; - “Immune response”: An "immunological response" or "immune response" to an antigen or composition, as used herein, refers to the development in a subject of a humoral and / or cellular immune response to the antigen or composition; Immune responses include innate and adaptive immune responses. Innate immune responses are fast-acting responses that provide a first line of defense for the immune system. In contrast, adaptive immunity uses selection and clonal expansion of immune cells having somatically rearranged receptor genes (e.g., T- and B-cell receptors) that recognize antigens from a given pathogen or disorder (e.g., a tumor), thereby providing specificity and immunological memory. Innate immune responses, among their many effects, lead to a rapid burst of inflammatory cytokines and activation of antigen-presenting cells (APCs) such as macrophages and dendritic cells. To distinguish pathogens from self-components, the innate immune system uses a variety of relatively invariable receptors that detect signatures from pathogens, known as pathogen-associated molecular patterns, or PAMPs. The mechanism behind this potentiation of the immune responses has been reported to involve pattern- recognition receptors (PRRs), which are differentially expressed on a variety of immune cells, including neutrophils, monocytes, macrophages, dendritic cells, natural killer cells, B cells and some non-immune cells such as epithelial and endothelial cells. Engagement of PRRs leads to the activation of some of these cells and their secretion of cytokines and chemokines, as well as maturation and migration of other cells. In tandem, this creates an inflammatory environment that leads to the establishment of the adaptive immune response. PRRs include nonphagocytic receptors, such as Toll-like receptors (TLRs) and nucleotide- binding oligomerization domain (NOD) proteins, and receptors that induce phagocytosis, such as scavenger receptors, mannose receptors and β-glucan receptors. Dendritic cells are recognized as some of the most important cell types for initiating the priming of naive CD4+helper T (TH) cells and for inducing CD8+T cell differentiation into killer cells. TLR signaling has been reported to play an important role in determining the quality of these helper T cell responses, for instance, with the nature of the TLR signal determining the specific type of TH response that is observed (e.g., TH1 versus TH2 response). A combination of antibody (humoral) and cellular immunity are produced as part of a TH1 -type response, whereas a TH2-type response is predominantly an antibody response ; - A “humoral immune response” refers to an immune response mediated by antibody molecules, while a "cellular immune response" refers to an immune response mediated by T- lymphocytes and / or other white blood cells. One important aspect of cellular immunity involves an antigen-specific response by cytolytic T-cells ("CTLs"). CTLs have specificity for peptide antigens that are presented in association with proteins encoded by the major histocompatibility complex (MHC) and expressed on the surfaces of cells. CTLs help induce and promote the destruction of intracellular microbes, or the lysis of cells infected with such microbes. Another aspect of cellular immunity involves an antigen-specific response by helper T-cells. Helper T-cells act to help stimulate the function, and focus the activity of, nonspecific effector cells against cells displaying peptide antigens in association with MHC molecules on their surface. A "cellular immune response" also refers to the production of cytokines, chemokines and other such molecules produced by activated T-cells and / or other white blood cells, including those derived from CD4+and CD8+T-cells; - An “immune response” associated with TLR7 and / or TLR8 is an immune response which involves activation of TLR7 and / or TLR8 receptors. Activation of TLR7 and / or TLR8 receptors may be determined in vitro using methods such as those described in the Examples; - “Induce”: "Induce" and variations thereof refer to any measurable increase in cellular activity. Induction of an immune response may include, for example, an increase in the production of a cytokine, an activation, proliferation, or maturation of a population of immune cells, and / or other indicator of increased immune function; - A “binding agent”: a molecule with affinity for a biological target, such as a ligand, a protein, a polypeptide, an antibody such as a monoclonal antibody or a VHH antibody, a peptide, an oligonucleotide, an oligosaccharide for instance a targeting agent for instance a cell-binding agent. The function of the binding agent is to direct the biologically active compound, such as a TLR7 and / or 8 agonist compound towards the biological target; - A “cell binding agent”: Cell binding agents may be of any kind presently known, or that become known and includes peptides and non-peptides. The cell binding agent may be any compound that can bind a cell, either in a specific or non-specific manner. Generally, these can be antibodies (especially monoclonal antibodies), lymphokines, hormones, growth factors, vitamins, nutrient-transport molecules (such as transferrin), or any other cell binding molecule or substance. More specific examples of cell binding agents that can be used include: (a) polyclonal antibodies; (b) monoclonal antibodies; (c) fragments of antibodies such as Fab, Fab1, and F(ab')2, Fv (Parham, J. Immunol. 131:2895-2902 (1983); Spring et al. J. Immunol. 113:470-478 (1974); Nisonoff et al. Arch. Biochem. Biophys. 89:230-244 (I960)); (d) interferons (e.g. alpha, beta, gamma); (e) lymphokines such as IL2, IL3, IL4, IL6; (f) hormones such as insulin, TRH (thyrotropin releasing hormone), MSH (melanocyte- stimulating hormone), steroid hormones, such as androgens and estrogens; (g) growth factors and colony-stimulating factors such as EGF, TGFα, FGF, VEGF, G-CSF, M-CSF and GM-CSF (Burgess, Immunology Today 5:155-158 (1984)); or (h) transferrin (O'Keefe et al. J. Biol. Chem. 260:932-937 (1985)); and (i) vitamins, such as folate; - A “cell permeable” compound: A membrane permeability of a compound is evaluated using an in vitro model of passive, transcellular permeation called PAMPA (for Parallel artificial membrane permeability assay). This PAMPA assay allows to evaluate permeability over pH, from pH 6.5 to pH 7.4. A compound is considered as: “poorly or low permeable” with a PAMPA below 25; “moderate permeable” between 26 and 300; and “high permeable” above 300. A "non-cell permeable compound” is defined by a PAMPA below 25, as well as a differential activity in THP1 DUAL reporter cell assay between the free drug and the drug conjugated to a mAb: a non-cell permeable drug is not active at 500 nM as free drug and active at the nM range conjugated to a mAb; - A "targeting agent": a targeting agent refers to a structure that has a selective affinity for a target molecule relative to other non-target molecules. A targeting moiety binds to a target molecule. A targeting moiety may include, for example, an antibody, a peptide, a ligand, a receptor, or a binding portion thereof the target biological molecule may be a biological receptor or other structure of a cell such as a tumor antigen. A targeting moiety is often specific for a particular cell surface antigen, so as to target an immune-stimulatory compound to a target cell or disease site ; - An “antibody”: an antibody with affinity for a biological target, such as a monoclonal antibody. The function of the antibody is to direct the biologically active compound such as a TLR7 and / or 8 agonist compound towards the biological target. The antibody may be monoclonal, polyclonal or multispecific; it may also be an antibody fragment; it may also be a murine, chimeric, humanized or human antibody. An “antibody” may be a natural or conventional antibody in which two heavy chains are linked to each other by disulfide bonds and each heavy chain is linked to a light chain by a disulfide bond (also referred to as a “full- length antibody”). The terms “conventional (or full-length) antibody” refers both to an antibody comprising the signal peptide (or pro-peptide, if any), and to the mature form obtained upon secretion and proteolytic processing of the chain(s). There are two types of light chain, lambda (l) and kappa (k). There are five main heavy chain classes (or isotypes) which determine the functional activity of an antibody molecule: IgM, IgD, IgG, IgA and IgE. Each chain contains distinct sequence domains. The light chain includes two domains or regions, a variable domain (VL) and a constant domain (CL). The heavy chain includes four domains, a variable domain (VH) and three constant domains (CH1, CH2 and CH3, collectively referred to as CH). The variable regions of both light (VL) and heavy (VH) chains determine binding recognition and specificity to the antigen. The constant region domains of the light (CL) and heavy (CH) chains confer important biological properties such as antibody chain association, secretion, trans-placental mobility, complement binding, and binding to Fc receptors (FcR). The Fv fragment is the N-terminal part of the Fab fragment of an immunoglobulin and consists of the variable portions of one light chain and one heavy chain. The specificity of the antibody resides in the structural complementarity between the antibody combining site and the antigenic determinant. Antibody combining sites are made up of residues that are primarily from the hypervariable or complementarity determining regions (CDRs). Occasionally, residues from non-hypervariable or framework regions (FR) influence the overall domain structure and hence the combining site. CDRs refer to amino acid sequences which together define the binding affinity and specificity of the natural Fv region of a native immunoglobulin binding site. The light and heavy chains of an immunoglobulin each have three CDRs, designated CDR1-L, CDR2-L, CDR3-L and CDR1- H, CDR2-H, CDR3-H, respectively. A conventional antibody antigen-binding site, therefore, includes six CDRs, comprising the CDR set from each of a heavy and a light chain V region. As used herein, the term “antibody” denotes both conventional (full-length) antibodies and fragments thereof, as well as single domain antibodies and fragments thereof, such as variable heavy chain of single domain antibodies. Fragments of (conventional) antibodies typically comprise a portion of an intact antibody, such as the antigen binding region or variable region of the intact antibody and retain the biological function of the conventional antibody. Examples of such fragments include Fv, Fab, F(ab')2, Fab', dsFv, (dsFv)2, scFv, sc(Fv)2, VHH and diabodies; By convention the numbering of the variable constant region domains increases as they become more distal from the antigen binding site or amino-terminus of the immunoglobulin or antibody. The N-terminus of each heavy and light immunoglobulin chain is a variable region and at the C-terminus is a constant region; the CH3 and CLdomains actually comprise the carboxy-terminus of the heavy and light chain, respectively. Accordingly, the domains of a light chain immunoglobulin are arranged in a VL-CLorientation, while the domains of the heavy chain are arranged in the VH-CHl-hinge-CH2-CH3 orientation. Amino acid positions in a heavy chain constant region, including amino acid positions in the CH1, hinge, CH2, CH3, and CLdomains, may be numbered according to the Kabat index numbering system (see Kabat et al, in "Sequences of Proteins of Immunological Interest", U.S. Dept. Health and Human Services, 5th edition, 1991), the EU numbering (See Edelman, G.M. et al., Proc. Natl. Acad. USA, 63, 78-85 (1969). PMID: 5257969) or according to IMGT (See Lefranc, M.-P. et al., Dev. Comp. Immunol., 29, 185-203 (2005) PMID: 15572068 ). As used herein, the term " VH domain" includes the amino terminal variable domain of an immunoglobulin heavy chain, and the term " VLdomain" includes the amino terminal variable domain of an immunoglobulin light chain. As used herein, the term "CH1 domain" includes the first (most amino terminal) constant region domain of an immunoglobulin heavy chain that extends, e.g., from about positions 114-223 in the Kabat numbering system (EU positions 118-215). The CH1 domain is adjacent to the VH domain and amino terminal to the hinge region of an immunoglobulin heavy chain molecule, and does not form a part of the Fc region of an immunoglobulin heavy chain. As used herein, the term "hinge region" includes the portion of a heavy chain molecule that joins the CH1 domain to the CH2 domain. This hinge region comprises approximately 25 residues and is flexible, thus allowing the two N-terminal antigen binding regions to move independently. Hinge regions can be subdivided into three distinct domains: upper, middle, and lower hinge domains (Roux et al. J. Immunol. 1998, 161 :4083). As used herein, the term "CH2 domain" includes the portion of a heavy chain immunoglobulin molecule that extends, e.g., from about positions 244-360 in the Kabat numbering system (EU positions 231-340). The CH2 domain is unique in that it is not closely paired with another domain. Rather, two N-linked branched carbohydrate chains are interposed between the two CH2 domains of an intact native IgG molecule. In one embodiment, an antigen-binding protein of the current disclosure comprises a CH2 domain derived from an IgG1 molecule (e.g. a human IgG1 molecule). As used herein, the term "CH3 domain" includes the portion of a heavy chain immunoglobulin molecule that extends approximately 110 residues from N-terminus of the CH2 domain, e.g., from about positions 361-476 of the Kabat numbering system (EU positions 341 -445). The CH3 domain typically forms the C-terminal portion of the antibody. In some immunoglobulins, however, additional domains may extend from CH3domain to form the C-terminal portion of the molecule (e.g. the CH4 domain in the μ chain of IgM and the e chain of IgE). In one embodiment, an antigen-binding protein of the current disclosure comprises a CH3 domain derived from an IgG1 molecule (e.g. a human IgG1 molecule). As used herein, the term " CLdomain" includes the constant region domain of an immunoglobulin light chain that extends, e.g. from about Kabat position 107A-216. The CLdomain is adjacent to the VL domain. In one embodiment, an antigen-binding protein of the current disclosure comprises a CL domain derived from a kappa light chain (e.g., a human kappa light chain). As used herein, the positions are defined according to EU numbering. For example: A118 is at position 118 according to EU numbering, 114 according to Kabat numbering and 1 according to IMGT numbering; E152 is at position 152 according to EU numbering, 150 according to Kabat numbering and 35 according to IMGT numbering; K274 is at position 274 according to EU numbering, 187 according to Kabat numbering and 44 according to IMGT; K414 is at position 414 according to EU numbering, 145 according to Kabat numbering and 74 according to IMGT numbering; and K360 is at position 360 according to EU numbering, 383 according to Kabat numbering and 20 according to IMGT numbering; - “biological target”: an antigen (or group of antigens) for instance located at the surface of cancer cells or stromal cells associated with this tumor; these antigens may be, for example, a growth factor receptor, an oncogene product or a mutated “tumor suppressant” gene product, an angiogenesis-related molecule or an adhesion molecule or a receptor increased in tumor micro-environment; - A “conjugate”: an antibody-drug conjugate or ADC, i.e., a polypeptide such as an antibody (as defined above) to which is covalently attached via a linker at least one molecule of a TLR7 and / or 8 agonist. In the case of the present disclosure means compound of formulae (II), (II1) and (II2); - A “DAR” (drug-to-antibody ratio): a number of TLR7 and / or 8 agonists attached via a linker to an antibody. DAR may be an average number or a precise number depending on the conjugation technology used. The DAR may be an average or precise DAR between 2 to 10. Preferentially, the DAR may be 2, 4 or 8; - A “Fc receptor”: a protein at the surface of certain immune cells such as B lymphocytes, follicular dendritic cells, natural killer cells, macrophages, monocytes, neutrophils, eosinophils, basophils, human platelets, and mast cells and contributing to the protective functions of the immune system. It may recognize the Fc (fragment crystallizable) region of an antibody; - A “linker”: a group of atoms or a single bond that can covalently attach a compound / payload of formula (I) to a binding agent for instance a protein, a polypeptide, a ligand, a peptide, an oligonucleotide or an oligosaccharide, for instance a targeting agent for instance a cell-binding agent such as an antibody, such as a monoclonal antibody or a VHH antibody in order to form a compound / conjugate of formula (II); - A “peptidic linker”: a linker comprising amino acids; - A “PEGylated linker”: a linker comprising PEG as defined above; - A “payload”: a TLR7 and / or 8 agonist compound to which is covalently attached a linker. In the case of the present disclosure means compound of formulae (I), (I1) and (I2). - A “modifying agent”: chemical agent that is used to modify amino acid side chains of the antibody in order to introduce a reactive group; - A “reactive group”: a group of atoms that can promote or undergo a chemical reaction; - An “activated disulfide”: a group comprising at least one disulfide group prone to thiol- disulfide exchange as illustrated in Bioconjugate techniques, Second Edition by Greg T. Hermanson (ISBN (978-0-12-370501-3). By way of examples of activated disulfide, mention may be made of, but not limited to, ;- An “activated C≡C”: a group comprising at least one cycloalkyne C≡C bond as illustrated in Bioconjugate techniques, Second Edition by Greg T. Hermanson (ISBN (978-0-12- 370501-3). By way of examples of activated C≡C, mention may be made of, but not limited to a cyclooctyne moiety, for instance a DBCO-amine - A “cycloalkyne”: a monocyclic or polycyclic ring which comprises at least one C≡C bond, and from 3 to 16 carbon atoms and which can be unsubstituted or substituted; - A “heterocycloalkyne”: a cycloalkyne group as defined above which comprises at least one to six heteroatoms selected from oxygen, nitrogen and sulfur. BRIEF DESCRIPTION OF THE FIGURES Figure 1a represents a graph which shows a comparison of the production of IFNα between three examples in accordance with the present disclosure, that is to say Example 75, Example 103, and Example 105; and one comparative assay (reference) named unconjugated mAb (monoclonal antibody) also called naked mAb in the present text. This graph comprises thus four columns which correspond respectively from the left to the right to Example 75, Example 103, Example 105 and unconjugated mAb. The x-axis corresponds to the concentration of ADC in nanomolar (nM) and the y-axis corresponds to the concentration of IFNα in pg / ml (see Example C below). Figure 1b represents a graph which shows a comparison of the production of IP10 between three examples in accordance with the present disclosure, that is to say Example 75, Example 103, and Example 105; and one comparative assay (reference) named unconjugated mAb (monoclonal antibody) also called naked mAb in the present text. This graph comprises thus four columns which correspond respectively from the left to the right to Example 75, Example 103, Example 105 and unconjugated mAb. The x-axis corresponds to the concentration of ADC in nM and the y-axis corresponds to the concentration of IP10 in pg / ml (see Example C below). Figure 1c represents a graph which shows a comparison of the production of TNFα between three examples in accordance with the present disclosure, that is to say Example 75, Example 103, and Example 105; and one comparative assay (reference) named unconjugated mAb (monoclonal antibody) also called naked mAb in the present text. This graph comprises thus four columns which correspond respectively from the left to the right to Example 75, Example 103, Example 105 and unconjugated mAb. The x-axis corresponds to the concentration of ADC in nM and the y-axis corresponds to the concentration of TNFα in pg / ml (see Example C below). Figure 1d represents a graph which shows a comparison of the production of IL6 between three examples in accordance with the present disclosure, that is to say Example 75, Example 103, and Example 105; and one comparative assay (reference) named unconjugated mAb (monoclonal antibody) also called naked mAb in the present text. This graph comprises thus four columns which correspond respectively from the left to the right to Example 75, Example 103, Example 105 and unconjugated mAb. The x-axis corresponds to the concentration of ADC in nM and the y-axis corresponds to the concentration of IL6 in pg / ml (see Example C below). Figure 2 represents a graph which illustrates the evaluation of anti-tumoral activity. This graph comprises 11 (eleven) curves, namely 10 (ten) for 10 (ten) examples in accordance with the present disclosure and one for one comparative assay named Tusamitamab-R848 ADC. The x-axis corresponds to the concentration of the conjugates in nM and the y-axis corresponds to AUC (area under the curve) datas at 138 h (see Example D below). The 11 different curves are detailed below: The curve with the symbols corresponds to Tusamitamab-R848 ADC (also named in the present disclosure Tusa-R848). The curve with the symbols corresponds to Example 91. The curve with the symbols corresponds to Example 99. The curve with the symbols corresponds to Example 19. The curve with the symbols corresponds to Example 64. The curve with the symbols corresponds to Example 15. The curve with the symbols corresponds to Example 97. The curve with the symbols corresponds to Example 21. The curve with the symbols corresponds to Example 107. The curve with the symbols corresponds to Example 27. The curve with the symbols corresponds to Example 31. Abbreviations Ab: antibody; ACN, MeCN or CH3CN: acetonitrile; AcOH: acetic acid; ADC: antibody- drug conjugate; ADIBO: azadibenzocyclooctyne; Ala: alanine; AP-1: activator protein-1; AUC: area under the curve; CDCl3: deuterated chloroform; CEACAM5: cancer embryonic antigen cell adhesion molecule 5; CHCl3: chloroform; Cit: citrulline, CO2: carbon dioxide; conc.: concentrated; Cs2CO3: cesium carbonate; D2O: deuterium oxide; DAR: drug-to- antibody ratio; DBCO: dibenzylcyclooctyne; DC: dendritic cell; DCC: N,N′- dicyclohexylcarbodiimide; DCM: dichloromethane; DHAA: dehydroascorbic acid; DIEA or DIPEA: N,N-diisopropylethylamine; DIC: N,N′-diisopropylcarbodiimide; DMA: dimethylacetamide; DMAP: 4-dimethylaminopyridine; DMF: N,N-dimethylformamide; DMSO: dimethylsulfoxide; DPBS: Dulbecco's phosphate-buffered saline; DSC: N,N’- disuccinimidyl carbonate; DTT: dithiothreitol; EC50: effective concentration 50; EDC.HCl: 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride; EDCI: 1-ethyl-3-(3- dimethylaminopropyl)carbodiimide; EDTA: ethylenediaminetetraacetic acid; ELSD: evaporative light scattering detector; ES: electrospray; Et2O: diethyl ether; EtOAc: ethyl acetate; EtOH: ethanol; FBS: fetal bovine serum; Glu: glutamic acid; H2O: water; H2SO4: sulfuric acid; HATU: 1-[bis(dimethylamino)methylene]-1H-1,2,3-triazolo[4,5-b] pyridinium 3-oxide hexafluorophosphate; HBTU: (2-(1H-benzotriazol-1-yl)-1,1,3,3- tetramethyluronium hexafluorophosphate; HCl: hydrochloric acid; HEK: human embryonic kidney; HEPES: 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid; HIC: hydrophobic interaction chromatography; HOAt: 1-hydroxy-7-azabenzotriazole; HOBt: hydroxybenzotriazole; HPLC: high pressure liquid chromatography; HRMS: high resolution mass spectrometry; IEC: ion exchange chromatography; IFN: interferon; i.e.: “id est”, that is; IL: interleukin; IP10: interferon gamma-induced protein 10; iPr2O: diisopropyl ether; iPrOH: isopropanol; ISG: interferon-stimulated gene; KCl: potassium chloride; KD: dissociation constant; K2HPO4: dipotassium hydrogen phosphate; KH2PO4: potassium dihydrogen phosphate; LAR: linker-to-antibody ratio; LCMS: liquid chromatography mass spectrometry; LiOH: sodium hydroxide; mAb or MAb: monoclonal antibody; mCPBA : meta-chloroperoxybenzoic acid; MeOH: methanol; Me-THF or MeTHF: methyl tetrahydrofuran; MgSO4: magnesium sulfate; MS: mass spectrometry; MSD: Meso Scale Discovery; MTBE: methyl tert-butyl ether; N2: azote; NaCl: sodium chloride; NaH: sodium hydride; NaHCO3: sodium bicarbonate; Na2HPO4: disodium hydrogen phosphate; NaOH: sodium hydroxide; NaPi: sodium phosphate; Na2SO4: sodium sulfate; NBS: N- bromosuccinimide; nBuLi: n-butyllithium; NF-kB: nuclear factor kappa-light-chain- enhancer of activated B cells; NH2NH2.H2O: hydrazine hydrate; NH3: ammonia; NH4Cl: ammonium chloride; NH4OH: ammonium hydroxide; NHS: N-hydroxysuccinimide; NMP: N-methyl-2-pyrrolidone; NMR: nuclear magnetic resonance; NT: not tested; OD: optical density; PBMC: peripheral blood mononuclear cells; PBS: phosphate buffer saline; PDL1: Programmed death-ligand 1; PEG: polyethylene glycol; PEGn: polyethylene glycol comprising a number n (integer) of ethylene glycol units; PES: polyethersulfone; POCl3: phosphoryl chloride; PODS: phenyloxadiazolyl methylsulfone; PS: polysorbate; PTFE: polytetrafluoroethylene; PVDF: polyvinylidene fluoride; RP: reverse phase; RPMI: Roswell Park Memorial Institute; rt or RT: room temperature; sat.: saturated; SCX: Strong Cation Exchange; SEAP: Secreted Embryonic Alkaline Phosphatase; SEC: size exclusion chromatography; SFC: supercritical fluid chromatography; SOCl2: thionyl chloride; T: temperature; TAA: tumor-associated antigen; TCEP: tris(2-carboxyethyl)phosphine; TEA : triethylamine; TFA: trifluoroacetic acid; THF: tetrahydrofuran; TLC: thin-layer chromatography; TLR: Toll-like receptor; TMS: tetramethyl silane; tR: retention time; UPLC: ultra-performance liquid chromatography; UV: ultraviolet; Val: valine; ~ : about. DETAILED DESCRIPTION OF THE INVENTION The disclosure relates to a compound / payload of formula (I) or a pharmaceutically acceptable salt thereof: A-L1-RCG1 (I) wherein: - A is a drug unit of formula (A) wherein: R1 represents: - a hydrogen atom, or - a group selected from: a) - a (C1-C6)alkyl- group; - a hydroxy-(C1-C6)alkyl- group; - a NH2-(C1-C6)alkyl- group; - a NH-(C1-C6)alkyl-(C1-C6)alkyl- group;- a N((C1-C6)alkyl)2-(C1-C6)alkyl- group; - a (C2-C6)alkenyl- group; - a (C2-C6)alkynyl- group; b) - a phenyl(C1-C6)alkyl- group being unsubstituted or substituted by at least one substituent selected from: b1) - a (C1-C6)alkoxy- group; b2) - a hydroxyl group; b3) a -C(O)-H group; and b4) - a (C1-C6)alkyl- group being unsubstituted or substituted by at least one substituent selected from: b4.1) - a hydroxyl group; and b4.2) - a -NR4R5group wherein R4and R5, being independently from each other selected from: b4.2.1) - a hydrogen atom; b4.2.2) - a (C1-C16)alkyl- group; b4.2.3) - a CH3-[O-(CH2)2]n- group with n being an integer from 1 to 30, a (C1-C6)alkoxy(C1-C6)alkyl- group, or a (C1-C6)alkoxy(C1-C6)alkoxy(C1-C6)alkyl- group; b4.2.4) - a (C1-C6)alkyl-S(O2)- group; b4.2.5) - a (C1-C6)alkyl-NH-C(O)- group; b4.2.6) - a (C1-C16)alkyl-C(O)- group; b4.2.7) - a (C1-C16)alkyl-O-C(O)- group; b4.2.8) - a CH3-[O-(CH2)2]n-C(O)- group with n being an integer from 1 to 30; b4.2.9) - a (C3-C10)cycloalkyl- group being unsubstituted or substituted by at least one substituent selected from: - a hydroxyl group; and - a (C1-C6)alkyl- group; or b4.2.10) - a (C3-C10)membered heterocycloalkyl- group comprising from one to four heteroatoms selected from oxygen, nitrogen, sulfur, -S(O)- and -SO2-; b4.2.11) - a phenyl-C(O)- group; b4.2.12) - a (C1-C6)alkoxy-phenyl-(C1-C6)alkyl-O-C(O)- group; b4.2.13) - a (C1-C16)alkyl-C(O)-NH-phenyl-(C1-C6)alkyl-O-C(O)- group; b4.2.14) - a (C1-C16)alkyl-O-C(O)-(C1-C6)alkyl- group; or R4and R5form together with the nitrogen atom to which they are attached a (C3-C10)membered heterocycloalkyl- group comprising one to four heteroatoms selected from oxygen, nitrogen and sulfur, said (C3-C10)membered heterocycloalkyl- group being unsubstituted or substituted by at least one substituent selected from a (C1-C6)alkyl- group, and a CH3-[O-(CH2)2]n- group with n being an integer from 1 to 30; c) - a (C3-C10)cycloalkyl(C1-C6)alkyl- group being unsubstituted or substituted by at least one substituent selected from -NH2and a NH2-(C1-C6)alkyl- group; d) - a (C3-C10)membered heterocycloalkyl(C1-C6)alkyl- group comprising one to four heteroatoms selected from oxygen, nitrogen, and sulfur, said heterocycloalkyl group being unsubstituted or substituted by at least one substituent selected from a (C1-C6)alkyl- group and a CH3-[O-(CH2)2]n- group with n being an integer from 1 to 30; and e) - a (C5-C10)membered heteroaryl(C1-C6)alkyl- group comprising one to four heteroatoms selected from oxygen, nitrogen, and sulfur, said heteroaryl being unsubstituted or substituted by at least one substituent selected from: - a (C1-C6)alkyl- group; - a NH2-(C1-C6)alkyl- group and - a cyano group; f) - a (C3-C10)membered heterocycloalkyl-NH-(C1-C16)alkyl- group, said heterocycloalkyl group comprising one to four heteroatoms selected from oxygen, nitrogen, S(O), SO2and sulfur; g) - a (C3-C10)membered heterocycloalkyl-N(C(O)-(C1-C6)alkyl)-(C1-C16)alkyl- group, said heterocycloalkyl group comprising one to four heteroatoms selected from oxygen, nitrogen, S(O), SO2 and sulfur; R2 represents a halogen atom, or a group selected from: - a (C1-C6)alkyl- group; - a (C2-C6)alkenyl- group; - a (C2-C6)alkynyl- group; - a (C1-C6)alkylthio- group; - a (C1-C6)alkylthio(C1-C6)alkyl- group; - a (C1-C6)alkyl-S(O)- group; - a (C1-C6)alkyl-S(O2)- group; - a (C1-C6)alkyl-S(O)-(C1-C6)alkyl- group; - a (C1-C6)alkyl-S(O2)-(C1-C6)alkyl- group; - a (C1-C6)alkoxy- group; - a (C1-C6)alkoxy(C1-C6)alkyl- group; - a (C1-C6)haloalkoxy(C1-C6)alkyl- group; - a (C3-C5)cycloalkyl-O-(C1-C6)alkyl- group; - a (C1-C6)alkyl-NH-(C1-C6)alkyl- group; - a ((C1-C6)alkyl)2-N-(C1-C6)alkyl- group; - a (C1-C6)alkyl-NH- group; and - a ((C1-C6)alkyl)2N- group; R3 represents: - a deuterium atom; - a hydrogen atom or a group selected from: a) - a (C1-C6)alkyl- group; - a (C2-C6)alkenyl- group; - a (C2-C6)alkynyl- group; and -a (C1-C6)alkylthio- group; b) - a -OR6group wherein R6is selected from: - a hydrogen atom; - a (C1-C6)alkyl- group; - a CH3-[O-(CH2)2]n- group with n being an integer from 1 to 30; - a (C2-C6)alkenyl- group; - a (C2-C6)alkynyl- group; - a (C3-C10)cycloalkyl- group; - a phenyl group; - a phenyl(C1-C6)alkyl- group; and - a (C3-C10)membered heterocycloalkyl- group comprising one to four heteroatoms selected from oxygen, nitrogen, sulfur, -S(=O)- and -S(=O)2-; c) - a -NR7R8 group wherein R7 and R8 being, independently from each other, selected from: - a hydrogen atom; - a CH3-[O-(CH2)2]n- with n being an integer from 1 to 30; - a (C1-C6)alkyl- group unsubstituted or substituted by - a (C5-C10)membered heteroaryl group comprising one to four heteroatoms selected from oxygen, nitrogen and sulfur; or - a phenyl group being unsubstituted or substituted by at least one substituent selected from: - a cyano group and - a NR9R10-(C1-C6)alkyl- group wherein: R9 and R10 being, independently from each other, selected from: - a hydrogen atom; - a (C1-C6)alkyl- group; - a CH3-[O-(CH2)2]n- with n being an integer from 1 to 30, or R9 and R10 together form with the nitrogen atom to which they are attached a (C3-C10)membered heterocycloalkyl- group comprising one to four heteroatoms selected from oxygen, nitrogen, and sulfur, said (C3-C10)membered heterocycloalkyl group being unsubstituted or substituted by at least one substituent selected from a (C1-C6)alkyl- group, and a CH3-[O-(CH2)2]n- group with n being an integer from 1 to 30; or R7and R8form together with the nitrogen atom to which they are attached a (C3-C10)membered heterocycloalkyl- group comprising one to four heteroatoms selected from oxygen, nitrogen, and sulfur, said heterocycloalkyl group being unsubstituted or substituted by at least one substituent selected from: - a phenyl group and - a hydroxy(C1-C6)alkyl-phenyl- group; d) - a (C3-C10)membered heterocycloalkyl- group comprising one to four heteroatoms selected from oxygen, nitrogen and sulfur; e) - a (C5-C10)membered heteroaryl- group comprising one to four heteroatoms selected from oxygen, nitrogen, and sulfur, said (C5-C10)membered heteroaryl- group being unsubstituted or substituted by at least one (C1-C6)alkyl- group; f) - a (C6-C10)membered aryl- group; and g) - a (C3-C10)cycloalkyl- group; - L1 represents a linker; and - RCG1 represents a reactive chemical group that is reactive towards a chemical group present on a binding agent, for instance on a protein, a polypeptide, a ligand, a peptide, an oligonucleotide or an oligosaccharide, for instance on a targeting agent for instance on a cell- binding agent such as an antibody such as a monoclonal antibody or a VHH antibody. According to a particular embodiment, L1 represents a cleavable linker or a non-cleavable linker. According to one particular embodiment, L1 is a cleavable linker which is a peptidic linker. According to another particular embodiment, L1 is a non-cleavable linker which is a PEGylated linker. RCG1 is a reactive group chemical group which is well known by the skilled person in the art. RCG1 is a tool for conjugating and as it is not a limitative radical, its list has not to be limited or restricted. Examples of RCG1 that may be mentioned include: (i) a RaZa-C(=O)- reactive group for which: Zarepresents a single bond, -O- or -NH, such as -O-, and Ra represents a hydrogen atom, a -(C1-C6)alkyl group, a -(C3-C7)cycloalkyl group, a -(C2-C6)alkenyl group, a -(C6-C10)aryl group, a -(C5-C10)heteroaryl group comprising 4 to 9 carbon atoms and 1 to 4 heteroatom(s) selected from oxygen, nitrogen, and sulfur, or a -(C3-C7)heterocycloalkyl group comprising 2 to 6 carbon atoms and 1 to 4 heteroatom(s) selected from oxygen, nitrogen, sulfur, -S(O)- and -SO2-, said -(C6-C10)aryl group, -(C5-C10)heteroaryl group and / or -(C3-C7)heterocycloalkyl group being optionally substituted by 1 to 5 atoms / groups chosen from a halogen atom, such as a fluorine atom, a - (C1-C6)alkyl group, a -(C1-C6)alkoxy group, a hydroxyl group, an oxo group, a nitro group and a cyano group; or (ii) one of the following reactive groups: a maleimido O group; a substituted O group with R21 representing a hydrogen atom or a -(C1-C6)alkyl group, such as a methyl group; Cl-; N3-; HO-; HS-; an activated disulfide such as S S H or O2NN ; H2N-; HC≡C- or an activated C≡C such as a cyclooctyne group; an -O-alkyl hydroxylamine or a Pictet-Spengler reaction substrate such described in Agarwal P., et al., Bioconjugate Chem 2013, 24, 846-851, for instance RCG1is N3-, a maleimido group , a substituted maleimido group , a -COOH group, a phenyloxadiazolyl methylsulfone , . O N O For instance, RaZa- may represent HO-, CH3O-, CH2=CH-CH2O-, O (O-NHS), cation represents for example sodium, potassium or cesium or which GI represents at least one electroinductive group such as -NO2or a halogen atom, such as a fluorine atom (F). They may be, for example, the following groups: . Another type of RaZa-C(=O)- group is the following: . In particular, RCG1 is N3-, -COOH, or a maleimido group O . Among the compounds of formula (I) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which A is of formula (A1) or of formula (A2) in which: R1, R2 and R3 are as defined in the present disclosure; the single asterisk (*) indicates the site of covalent attachment to -L1-RCG1; R1* represents: - either a single bond, which means that -L1-RCG1 is directly linked to the nitrogen atom of the imidazo[4,5-d]pyridazine ring, - or a divalent radical formed from R1 as defined in the present disclosure, which means that -L1-RCG1 is linked to the nitrogen atom of the imidazo[4,5-d]pyridazine ring via R1; R3* represents: - either a single bond, which means that -L1-RCG1 is directly linked to the carbon atom of the imidazo[4,5-d]pyridazine ring, - or a divalent radical formed from R3as defined in the present disclosure, which means that -L1-RCG1 is linked to the carbon atom of the imidazo[4,5-d]pyridazine ring via R3. According to one particular embodiment, A is of formula (A1). According to another embodiment, A is of formula (A2). Thus, according to a particular embodiment, when R1* represents a single bond, the compounds of formula (I) or a pharmaceutically acceptable salt thereof in accordance with the present disclosure have the following formula (Ia): wherein R2, R3, L1 and RCG1 are as defined in the present disclosure. This means that in this particular embodiment, in the drug A, R1 is a hydrogen atom. According to another particular embodiment, when R1* represents a divalent radical formed from R1 as defined in the present disclosure, the compounds of formula (I) or a pharmaceutically acceptable salt thereof in accordance with the present disclosure have the following formula (Iaa): wherein R2, R3, L1 and RCG1 are as defined in the present disclosure and R1* is a divalent R1 as defined in the present disclosure. This means that in this particular embodiment, in the drug A, R1 is not a hydrogen atom. According to another particular embodiment, when R3* represents a single bond, the compounds of formula (I) or a pharmaceutically acceptable salt thereof in accordance with the present disclosure have the following formula (Ib): wherein R1, R2, L1 and RCG1 are as defined in the present disclosure. This means that in this particular embodiment, in the drug A, R3 is a hydrogen atom. According to another particular embodiment, when R3* represents a divalent radical formed from R3 as defined in the present disclosure, the compounds of formula (I) or a pharmaceutically acceptable salt thereof in accordance with the present disclosure have the following formula (Ibb): wherein R1, R2, L1 and RCG1 are as defined in the present disclosure and R3* is a divalent R3 as defined in the present disclosure. This means that in this particular embodiment, in the drug A, R3 is not a hydrogen atom. In the present disclosure, the symbol on the bond denotes a covalent attachment site. The drug A or a pharmaceutically acceptable salt thereof in accordance with the present disclosure which is comprised in the formula (I) and in the formula (II) of the present disclosure, as well as processes for their preparation and their therapeutic uses, for instance as Toll-like receptor 7 agonists and / or Toll-like receptor 8 agonists are described in PCT / EP2022 / 052387 (WO2022167438). As described in PCT / EP2022 / 052387 (WO2022167438), according to a particular embodiment, in the formula of drug A or a pharmaceutically acceptable salt thereof, at least one of R1, and R3may be other than a hydrogen atom. As described in PCT / EP2022 / 052387 (WO2022167438), according to another particular embodiment, in the formula of drug A or a pharmaceutically acceptable salt thereof, R1 and R3 may be simultaneously other than a hydrogen atom. Among the compounds of formula (A) which are described in PCT / EP2022 / 052387 (WO2022167438) and / or encompassed by claim 1 of PCT / EP2022 / 052387 (WO2022167438), mention may be made for instance of the following compounds: (1) 2-butyl-7-isopropoxy-1-(4-methoxybenzyl)-1H-imidazo[4,5-d]pyridazin-4- amine; (2) 2-butyl-N7-isopropyl-1-(4-methoxybenzyl)-1H-imidazo[4,5-d]pyridazin- 4,7-diamine; (3) 2-butyl-7-(isopropylthio)-1-(4-methoxybenzyl)-1H-imidazo[4,5- d]pyridazin-4-amine; (4) 2-butyl-1-(4-methoxybenzyl)-7-(2-methoxyethoxy)-1H-imidazo[4,5- d]pyridazin-4-amine; (5) 2-butyl-1-(4-methoxybenzyl)-7-propoxy-1H-imidazo[4,5-d]pyridazin-4- amine; (6) 7-(allyloxy)-2-butyl-1-(4-methoxybenzyl)-1H-imidazo[4,5-d]pyridazin-4- amine; (7) 7-(sec-butoxy)-2-butyl-1-(4-methoxybenzyl)-1H-imidazo[4,5-d]pyridazin- 4-amine; (8) 7-butoxy-2-butyl-1-(4-methoxybenzyl)-1H-imidazo[4,5-d]pyridazin-4- amine; (9) 2-butyl-7-(cyclopentyloxy)-1-(4-methoxybenzyl)-1H-imidazo[4,5-d] pyridazin-4-amine; (10) 2-butyl-1-(4-methoxybenzyl)-7-(pyrrolidin-1-yl)-1H-imidazo[4,5- d]pyridazin-4-amine; (11) 2-butyl-1-(4-methoxybenzyl)-7-(1-methyl-1H-pyrrol-3-yl)-1H- imidazo[4,5d] pyridazin-4-amine; (12) (E)-2-butyl-1-(4-methoxybenzyl)-7-(3-methylbut-1-en-1-yl)-1H- imidazo[4,5-d]pyridazin-4-amine; (13) 2-butyl-7-isopentyl-1-(4-methoxybenzyl)-1H-imidazo[4,5-d]pyridazin-4- amine; (14) 2-butyl-1-(4-methoxybenzyl)-7-(1H-pyrrol-3-yl)-1H-imidazo[4,5- d]pyridazin-4-amine; (15) 2-butyl-7-(cyclopent-1-en-1-yl)-1-(4-methoxybenzyl)-1H-imidazo[4,5- d]pyridazin-4-amine hydrochloride; (16) 2-butyl-7-cyclopentyl-1-(4-methoxybenzyl)-1H-imidazo[4,5-d]pyridazin- 4-amine; (17) 2-butyl-1-(4-methoxybenzyl)-7-(prop-1-en-2-yl)-1H-imidazo[4,5- d]pyridazin-4-amine; (18) 2-butyl-7-isopropyl-1-(4-methoxybenzyl)-1H-imidazo[4,5-d]pyridazin-4- amine; (19) 4-(aminomethyl)cyclohexyl)methyl)-2-butyl-7-isopropoxy-1H- imidazo[4,5-d]pyridazin-4-amine dihydrochloride; (20) 4-(aminomethyl)cyclohexyl)methyl)-2-butyl-7-isopropoxy-1H- imidazo[4,5-d]pyridazin-4-amine 2,2,2-trifluoroacetate; (21) 1-(4-(aminomethyl)benzyl)-2-butyl-7-isopropoxy-1H-imidazo[4,5- d] pyridazin-4-amine; (22) 1-(4-(aminomethyl)benzyl)-2-butyl-7-isopropoxy-1H-imidazo[4,5- d]pyridazin-4-amine 2,2,2-trifluoroacetate; (23) 1-(((1S,3R)-3-aminocyclohexyl)methyl)-2-butyl-7-isopropoxy-1H- imidazo[4,5-d]pyridazin-4-amine (and enantiomer); (24) 1-(4-amino-2-butyl-7-isopropoxy-1H-imidazo[4,5-d]pyridazin-1- yl)-2-methylpropan-2-ol; (25) Trans 1-(4-aminocyclohexyl)methyl)-2-butyl-7-isopropoxy-1H- imidazo[4,5-d]pyridazin-4-amine; (26) 1-((5-(aminomethyl)pyridin-2-yl)methyl)-2-butyl-7-isopropoxy-1H- imidazo[4,5-d]pyridazin-4-amine; (27) 6-((4-amino-2-butyl-7-isopropoxy-1H-imidazo[4,5-d]pyridazin-1- yl)methyl)nicotinonitrile; (28) N-(4-((4-amino-2-butyl-7-isopropoxy-1H-imidazo[4,5d]pyridazin- 1-yl)methyl)benzyl)acetamide; (29) N-(4-((4-amino-2-butyl-7-isopropoxy-1H-imidazo[4,5-d]pyridazin- 1-yl)methyl)benzyl)undecanamide; (30) N-(4-((4-amino-2-butyl-7-isopropoxy-1H-imidazo[4,5-d]pyridazin- 1-yl)methyl)benzyl)pentanamide; (31) N-(4-((4-amino-2-butyl-7-isopropoxy-1H-imidazo[4,5-d]pyridazin- 1-yl)methyl)benzyl)-3-(2-methoxyethoxy)propanamide; (32) 1-(((1S,3S)-3-aminocyclohexyl)methyl)-2-butyl-7-isopropoxy-1H- imidazo[4,5-]pyridazin-4-amine (and enantiomer); (33) 1-(3-(aminomethyl)benzyl)-2-butyl-7-isopropoxy-1H-imidazo[4,5- d]pyridazin-4-amine 2,2,2-trifluoroacetate; (34) 4-((4-amino-2-butyl-7-isopropoxy-1H-imidazo[4,5-d]pyridazin-1- yl)methyl)benzaldehyde; (35) (4-((4-amino-2-butyl-7-isopropoxy-1H-imidazo[4,5-d]pyridazin-1- yl)methyl)phenyl)methanol; (36) 2-butyl-1-(4-((cyclopropylamino)methyl)benzyl)-7-isopropoxy-1H- imidazo[4,5-d]pyridazin-4-amine; (37) 3-((4-((4-amino-2-butyl-7-isopropoxy-1H-imidazo[4,5-d]pyridazin- yl)methyl)benzyl)amino)thietane 1,1-dioxide; (38) N-(4-((4-amino-2-butyl-7-isopropoxy-1H-imidazo[4,5-d]pyridazin- 1-yl)methyl)benzyl)-N-(1,1-dioxidothietan-3-yl)acetamide; (39) 2-butyl-7-isopropoxy-1-(4-(((1-methylcyclobutyl)amino)methyl)benzyl)- 1H-imidazo[4,5-d]pyridazin-4-amine; (40) 2-butyl-7-isopropoxy-1-(4-(piperazin-1-ylmethyl)benzyl)-1H-imidazo[4,5- d]pyridazin-4-amine; (41) 2-butyl-N7,N7,1-trimethyl-1H-imidazo[4,5-d]pyridazin-4,7-diamine; (42) 2-butyl-1-methyl-7-(pyrrolidin-1-yl)-1H-imidazo[4,5-d]pyridazin-4- amine; (43) 2-butyl-N7-(4-((dimethylamino)methyl)benzyl)-N7,1-dimethyl-1H- imidazo[4,5-d]pyridazin-4,7-diamine; (44) 2-butyl-N7,1-dimethyl-N7-(4-(morpholinomethyl)benzyl)-1H- imidazo[4,5-d]pyridazine-4,7-diamine; (45) 4-(((4-amino-2-butyl-1-methyl-1H-imidazo[4,5-d]pyridazin-7- yl)(methyl)amino)methyl)benzonitrile; (46) N7-(4-(aminomethyl)benzyl)-2-butyl-N7,1-dimethyl-1H- imidazo[4,5-d]pyridazine-4,7-diamine; (47) 2-butyl-N7-(4-(((2-methoxyethyl)(methyl)amino)methyl)benzyl)- N7,1-dimethyl-1H-imidazo[4,5-d]pyridazine-4,7-diamine; (48) 2-butyl-7-ethoxy-1-(4-methoxybenzyl)-1H-imidazo[4,5- d]pyridazin-4-amine; (49) 2-butyl-1-(4-methoxybenzyl)-N7-(2-methoxyethyl)-1H- imidazo[4,5-d]pyridazine-4,7-diamine; (50) 2-butyl-7-methoxy-1-(4-methoxybenzyl)-1H-imidazo[4,5-d]pyridazin-4- amine; (51) 2-butyl-7-cyclohexyl-1-(4-methoxybenzyl)-1H-imidazo[4,5-d]pyridazin- 4-amine; (52) 7-(benzyloxy)-2-butyl-1-(4-methoxybenzyl)-1H-imidazo[4,5- d]pyridazin-4-amine; (53) 2-butyl-1-(4-methoxybenzyl)-N7-methyl-1H-imidazo[4,5- d]pyridazine-4,7-diamine; (54) (S)-2-butyl-1-(4-methoxybenzyl)-7-((tetrahydrofuran-3-yl)oxy)-1H- imidazo[4,5-d]pyridazin-4-amine; (55) 2-butyl-7-(furan-2-yl)-1-(4-methoxybenzyl)-1H-imidazo[4,5-d]pyridazine- 4-amine; (56) 2-butyl-1-(4-methoxybenzyl)-7-((tetrahydrofuran-3-yl)oxy)-1H- imidazo[4,5-d]pyridazin-4-amine; (57) 2-butyl-1-(4-methoxybenzyl)-7-((tetrahydro-2H-pyran-4-yl)oxy)- 1H-imidazo[4,5-d]pyridazin-4-amine; (58) 2-butyl-1-(4-methoxybenzyl)-7-((tetrahydrothiophen-3-yl)oxy)-1H- imidazo[4,5-d]pyridazin-4-amine; (59) 2-butyl-1-(4-methoxybenzyl)-7-(tetrahydrofuran-3-yl)-1H- imidazo[4,5-d]pyridazin-4-amine; (60) 2-butyl-1-(4-methoxybenzyl)-7-(2-methylprop-1-en-1-yl)-1H- imidazo[4,5-d]pyridazin-4-amine; (61) 2-butyl-7-isobutyl-1-(4-methoxybenzyl)-1H-imidazo[4,5- d]pyridazin-4-amine; (62) 2-butyl-1-(4-methoxybenzyl)-7-(thiophen-3-yl)-1H-imidazo[4,5- d]pyridazin-4-amine; (63) 2-butyl-1-(4-methoxybenzyl)-7-(thiophen-2-yl)-1H-imidazo[4,5- d]pyridazin-4-amine; (64) 2-butyl-1-(4-methoxybenzyl)-7-(1H-pyrrol-2-yl)-1H-imidazo[4,5- d]pyridazin-4-amine hydrochloride; (65) 3-((4-amino-2-butyl-1-(4-methoxybenzyl)-1H-imidazo[4,5-d]pyridazin-7- yl)oxy)tetrahydrothiophene 1-oxide isomer A; (66) 2-butyl-7-(cyclohex-1-en-1-yl)-1-(4-methoxybenzyl)-1H- imidazo[4,5-d]pyridazin-4-amine; (67) 2-butyl-7-(furan-3-yl)-1-(4-methoxybenzyl)-1H-imidazo[4,5-d]pyridazin- 4-amine; (68) 3-((4-amino-2-butyl-1-(4-methoxybenzyl)-1H-imidazo[4,5-d]pyridazin-7- yl)oxy)tetrahydrothiophene 1,1-dioxide; (69) 3-((4-amino-2-butyl-1-(4-methoxybenzyl)-1H-imidazo[4,5-d]pyridazin-7- yl)oxy)tetrahydrothiophene 1-oxide isomer B; (70) 2-butyl-1-(4-methoxybenzyl)-7-(1-methyl-1H-pyrrol-2-yl)-1H- imidazo[4,5-d]pyridazin-4-amine hydrochloride; (71) 2-butyl-1-(4-methoxybenzyl)-N7,N7-dimethyl-1H-imidazo[4,5- d]pyridazine-4,7-diamine; (72) 2-butyl-1-(4-methoxybenzyl)-7-phenoxy-1H-imidazo[4,5-d]pyridazin-4- amine; (73) 2-butyl-7-(2,5-dihydrofuran-3-yl)-1-(4-methoxybenzyl)-1H-imidazo[4,5- d]pyridazin-4-amine; (74) 2-butyl-7-isopropoxy-1-(pyridin-3-ylmethyl)-1H-imidazo[4,5- d]pyridazin-4-amine; (75) 2-butyl-7-isopropoxy-1-(pyridin-2-ylmethyl)-1H-imidazo[4,5- d]pyridazin-4-amine; (76) 2-butyl-7-isopropoxy-1-(pyridin-4-ylmethyl)-1H-imidazo[4,5- d]pyridazin-4-amine 2,2,2-trifluoroacetate; (77) 1-(5-aminopentyl)-2-butyl-7-isopropoxy-1H-imidazo[4,5-d]pyridazin-4- amine; (78) 2-butyl-7-isopropoxy-1-(2-(piperidin-4-yl)ethyl)-1H-imidazo[4,5- d]pyridazin-4-amine; (79) 2-butyl-7-isopropoxy-1-(2-(piperazin-1-yl)ethyl)-1H-imidazo[4,5- d]pyridazin-4-amine; (80) 1-benzyl-2-butyl-7-isopropoxy-1H-imidazo[4,5-d]pyridazin-4- amine hydrochloride; (81) 2-butyl-1-(cyclohexylmethyl)-7-isopropoxy-1H-imidazo[4,5-d]pyridazin- 4-amine hydrochloride; (82) 2-butyl-7-isopropoxy-1-(4-(((tetrahydro-2H-pyran-4- yl)amino)methyl)benzyl)-1H-imidazo[4,5-d]pyridazin-4-amine hydrochloride; (83) 2-butyl-7-isopropoxy-1-(4-((isopropylamino)methyl)benzyl)-1H- imidazo[4,5-d]pyridazin-4-amine dihydrochloride; (84) N-(4-((4-amino-2-butyl-7-isopropoxy-1H-imidazo[4,5-d]pyridazin- 1-yl)methyl)benzyl)heptanamide; (85) (4-(1-(4-amino-2-butyl-1-methyl-1H-imidazo[4,5-d]pyridazin-7- yl)pyrrolidin-3-yl)phenyl)methanol hydrochloride; (86) 2-butyl-7-isopropoxy-1-methyl-1H-imidazo[4,5-d]pyridazin-4-amine; (87) N7-(4-(aminomethyl)benzyl)-2-butyl-1-methyl-1H-imidazo[4,5- d]pyridazine-4,7-diamine; (88) 2-butyl-N7-isopropyl-1-methyl-1H-imidazo[4,5-d]pyridazine-4,7-diamine; (89) 2-butyl-1-methyl-7-(3-phenylpyrrolidin-1-yl)-1H-imidazo[4,5- d]pyridazin-4-amine; (90) N7-benzyl-2-butyl-N7,1-dimethyl-1H-imidazo[4,5-d]pyridazine- 4,7-diamine; (91) 2-butyl-1-methyl-N7-(4-((4-methylpiperazin-1-yl)methyl)benzyl)- 1H-imidazo[4,5-d]pyridazine-4,7-diamine; (92) 2-butyl-1-(4-methoxybenzyl)-7-phenyl-1H-imidazo[4,5- d]pyridazin-4-amine; (93) 4-amino-2-butyl-1-(4-methoxybenzyl)-1H-imidazo[4,5-d]pyridazin-7-ol; (94) 2-butyl-N7-(3-(furan-2-yl)propyl)-1-(4-methoxybenzyl)-1H-imidazo[4,5- d]pyridazine-4,7-diamine; (95) 2-butyl-1-(4-methoxybenzyl)-1H-imidazo[4,5-d]pyridazin-4-amine; (96) 2-butyl-1-(4-methoxybenzyl)-7-(1H-pyrazol-3-yl)-1H-imidazo[4,5- d]pyridazin-4-amine; (97) 2-butyl-1-(4-methoxybenzyl)-7-(1-methyl-1H-pyrazol-4-yl)-1H- imidazo[4,5-d]pyridazin-4-amine; (98) 2-butyl-N7-isopropyl-1H-imidazo[4,5-d]pyridazine-4,7-diamine; (99) 2-butyl-7-(isopropylthio)-1H-imidazo[4,5-d]pyridazin-4-amine; (100) (1R,3R)-3-((4-((4-amino-2-butyl-7-isopropoxy-1H-imidazo[4,5- d]pyridazin-1-yl)methyl)benzyl)amino)cyclobutan-1-ol dihydrochloride salt; (101) 2-butyl-7-isopropoxy-1-(4-(pyrrolidin-1-ylmethyl)benzyl)-1H- imidazo[4,5-d]pyridazin-4-amine; (102) 2-butyl-7-isopropoxy-1-(4-(morpholinomethyl)benzyl)-1H-imidazo[4,5- d]pyridazin-4-amine; (103) N-(4-((4-amino-2-butyl-7-isopropoxy-1H-imidazo[4,5-d]pyridazin-1- yl)methyl)benzyl)propionamide; (104) 2-butyl-7-isopropoxy-1-(4-(((2-methoxyethyl)amino)methyl)benzyl)-1H- imidazo[4,5-d]pyridazin-4-amine; (105) 2-butyl-4-isopropoxy-3-[[4-[[2-[2-[2-[2-[2-(2- methoxyethoxy)ethoxy]ethoxy]ethoxy]ethoxy]ethylamino]methyl]phenyl]methyl]imidazo[ 4,5-d]pyridazin-7-amine; (106) N-(4-((4-amino-2-butyl-7-isopropoxy-1H-imidazo[4,5-d]pyridazin-1- yl)methyl)benzyl)benzamide; (107) N-(4-((4-amino-2-butyl-7-isopropoxy-1H-imidazo[4,5-d]pyridazin-1- yl)methyl)benzyl)-3-methoxypropanamide; (108) 2-butyl-7-isopropoxy-1-(4-(((2-(2- methoxyethoxy)ethyl)amino)methyl)benzyl)-1H-imidazo[4,5-d]pyridazin-4-amine; (109) 2-butyl-1-(4-((hexylamino)methyl)benzyl)-7-isopropoxy-1H- imidazo[4,5-d]pyridazin-4-amine; (110) 2-butyl-1-(4-((decylamino)methyl)benzyl)-7-isopropoxy-1H- imidazo[4,5-d]pyridazin-4-amine; (111) ethyl (4-((4-amino-2-butyl-7-isopropoxy-1H-imidazo[4,5-d]pyridazin-1- yl)methyl)benzyl)carbamate; (112) 4-methoxybenzyl (4-((4-amino-2-butyl-7-isopropoxy-1H-imidazo[4,5- d]pyridazin-1-yl)methyl)benzyl)carbamate; (113) 1-(4-((4-amino-2-butyl-7-isopropoxy-1H-imidazo[4,5-d]pyridazin-1- yl)methyl)benzyl)-3-ethylurea; (114) 4-acetamidobenzyl (4-((4-amino-2-butyl-7-isopropoxy-1H-imidazo[4,5- d]pyridazin-1-yl)methyl)benzyl)carbamate; (115) N-(4-((4-amino-2-butyl-7-isopropoxy-1H-imidazo[4,5-d]pyridazin-1- yl)methyl)benzyl)methanesulfonamide; (116) 2-butyl-1-(4-((dimethylamino)methyl)benzyl)-7-isopropoxy-1H- imidazo[4,5-d]pyridazin-4-amine; (117) tert-butyl (4-((4-amino-2-butyl-7-isopropoxy-1H-imidazo[4,5- d]pyridazin-1-yl)methyl)benzyl)glycinate; (118) 2-butyl-7-isopropoxy-1-(4-((methylamino)methyl)benzyl)-1H- imidazo[4,5-d]pyridazin-4-amine; (119) tert-butyl 3-((4-((4-amino-2-butyl-7-isopropoxy-1H-imidazo[4,5- d]pyridazin-1-yl)methyl)benzyl)amino)propanoate; (120) 1-(4-(5,8,11-trioxa-2-azadodecyl)benzyl)-2-butyl-7-isopropoxy-1H- imidazo[4,5-d]pyridazin-4-amine; (121) 2-butyl-4-isopropoxy-3-[[4-[[2-[2-[2-(2- methoxyethoxy)ethoxy]ethoxy]ethylamino]methyl]phenyl]methyl]imidazo[4,5- d]pyridazin-7-amine; (122) 2-butyl-4-isopropoxy-3-[[4-[[2-[2-[2-[2-[2-[2-[2-(2- methoxyethoxy)ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethylamino]methyl]phenyl] methyl]imidazo[4,5-d]pyridazin-7-amine di2,2,2-trifluoroacetate; (123) 2-butyl-4-isopropoxy-3-[[4-[[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-(2- methoxyethoxy)ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethox y]ethylamino]methyl]phenyl]methyl]imidazo[4,5-d]pyridazin-7-amine di2,2,2- trifluoroacetate; (124) 2-butyl-7-isopropoxy-1-(3-((methylamino)methyl)benzyl)-1H- imidazo[4,5-d]pyridazin-4-amine; (125) 2-butyl-1-(3-((dimethylamino)methyl)benzyl)-7-isopropoxy-1H- imidazo[4,5-d]pyridazin-4-amine; (126) 2-butyl-1-(3-((cyclobutylamino)methyl)benzyl)-7-isopropoxy-1H- imidazo[4,5-d]pyridazin-4-amine dihydrochloride salt; (127) 2-butyl-1-(3-((cyclopropylamino)methyl)benzyl)-7-isopropoxy-1H- imidazo[4,5-d]pyridazin-4-amine dihydrochloride salt; (128) 2-butyl-7-isopropoxy-1-(3-((isopropylamino)methyl)benzyl)-1H- imidazo[4,5-d]pyridazin-4-amine dihydrochloride salt; (129) 3-((3-((4-amino-2-butyl-7-isopropoxy-1H-imidazo[4,5-d]pyridazin-1- yl)methyl)benzyl)amino)thietane 1,1-dioxide; (130) 2-butyl-7-isopropoxy-1-(3-(((1-methylcyclobutyl)amino)methyl)benzyl)- 1H-imidazo[4,5-d]pyridazin-4-amine dihydrochloride salt; (131) 2-butyl-7-isopropoxy-1-(3-(piperazin-1-ylmethyl)benzyl)-1H- imidazo[4,5-d]pyridazin-4-amine; (132) (E)-1-(4-(aminomethyl)benzyl)-2-butyl-7-(3-methylbut-1-en-1-yl)-1H- imidazo[4,5-d]pyridazin-4-amine; (133) 1-(4-(aminomethyl)benzyl)-2-butyl-7-isopentyl-1H-imidazo[4,5- d]pyridazin-4-amine; (134) 1-(4-(aminomethyl)benzyl)-2-butyl-7-(pyrrolidin-1-yl)-1H-imidazo[4,5- d]pyridazin-4-amine; (135) 1-(4-(aminomethyl)benzyl)-2-butyl-7-(1H-pyrrol-3-yl)-1H-imidazo[4,5- d]pyridazin-4-amine 2,2,2-trifluoroacetate; (137) 1-(((1R,4R)-4-(aminomethyl)cyclohexyl)methyl)-2-butyl-7-((E)-3- methylbut-1-en-1-yl)-1H-imidazo[4,5-d]pyridazin-4-amine (138) 1-(((1R,4R)-4-(aminomethyl)cyclohexyl)methyl)-2-butyl-7-isopentyl- 1H-imidazo[4,5-d]pyridazin-4-amine; (139) 1-(((1R,4R)-4-aminocyclohexyl)methyl)-2-butyl-7-((E)-3-methylbut-1- en-1-yl)-1H-imidazo[4,5-d]pyridazin-4-amine; (140) 1-(((1R,4R)-4-aminocyclohexyl)methyl)-2-butyl-7-isopentyl-1H- imidazo[4,5-d]pyridazin-4-amine; (141) 1-(((1R,4R)-4-aminocyclohexyl)methyl)-2-butyl-7-(1H-pyrrol-3-yl)-1H- imidazo[4,5-d]pyridazin-4-amine; (142) 1-(((1R,4R)-4-(aminomethyl)cyclohexyl)methyl)-2-butyl-7-(pyrrolidin- 1-yl)-1H-imidazo[4,5-d]pyridazin-4-amine; (143) 3-[(4-aminocyclohexyl)methyl]-2-butyl-4-pyrrolidin-1-yl-imidazo[4,5- d]pyridazin-7-amine; (144) 1-[[4-(aminomethyl)phenyl]methyl]-2-butyl-7-(2,5-dihydro-1H-pyrrol-3- yl)imidazo[4,5-d]pyridazin-4-amine; (145) 1-[[4-(aminomethyl)phenyl]methyl]-2-butyl-7-pyrrolidin-3-yl- imidazo[4,5-d]pyridazin-4-amine; (146) 3-(6-aminohexyl)-2-butyl-4-isopropoxy-imidazo[4,5-d]pyridazin-7- amine dihydrochloride salt; (147) 2-butyl-4-isopropoxy-3-[6-(tetrahydropyran-4- ylamino)hexyl]imidazo[4,5-d]pyridazin-7-amine dihydrochloride salt; (148) N-[6-(7-amino-2-butyl-4-isopropoxy-imidazo[4,5-d]pyridazin-3- yl)hexyl]-N-tetrahydropyran-4-yl-acetamide; (149) 3-(4-aminobutyl)-2-butyl-4-isopropoxy-imidazo[4,5-d]pyridazin-7-amine dihydrochloride salt; (150) 2-butyl-4-isopropoxy-3-[4-(tetrahydropyran-4- ylamino)butyl]imidazo[4,5-d]pyridazin-7-amine hydrochloride salt; (151) N-[4-(7-amino-2-butyl-4-isopropoxy-imidazo[4,5-d]pyridazin-3- yl)butyl]-N-tetrahydropyran-4-yl-acetamide; (152) 2-butyl-3-[4-[(1,1-dioxothietan-3-yl)amino]butyl]-4-isopropoxy- imidazo[4,5-d]pyridazin-7-amine; (153) N-[4-(7-amino-2-butyl-4-isopropoxy-imidazo[4,5-d]pyridazin-3- yl)butyl]-N-(1,1-dioxothietan-3-yl)acetamide; (154) 2-butyl-3-[6-[(1,1-dioxothietan-3-yl)amino]hexyl]-4-isopropoxy- imidazo[4,5-d]pyridazin-7-amine; (155) N-[6-(7-amino-2-butyl-4-isopropoxy-imidazo[4,5-d]pyridazin-3- yl)hexyl]-N-(1,1-dioxothietan-3-yl)acetamide hydrochloride salt; (156) 2-[(7-amino-2-butyl-4-isopropoxy-imidazo[4,5-d]pyridazin-3-yl)methyl]- 2-methyl-propane-1,3-diol hydrochloride salt; (157) 2-[(7-amino-2-butyl-4-isopropoxy-imidazo[4,5-d]pyridazin-3- yl)methyl]propane-1,3-diol hydrochloride salt; (158) 1-(4-(aminomethyl)benzyl)-7-isopropoxy-2-propyl-1H-imidazo[4,5- d]pyridazin-4-amine; (159) 1-(4-(aminomethyl)benzyl)-2-(ethoxymethyl)-7-isopropoxy-1H- imidazo[4,5-d]pyridazin-4-amine; (160) 1-(4-(aminomethyl)benzyl)-7-isopropoxy-2-methyl-1H-imidazo[4,5- d]pyridazin-4-amine; (161) 3-[[4-(aminomethyl)phenyl]methyl]-4-isopropoxy-2-propylsulfanyl- imidazo[4,5-d]pyridazin-7-amine; (162) 3-[[4-(aminomethyl)phenyl]methyl]-4-isopropoxy-2-propylsulfinyl- imidazo[4,5-d]pyridazin-7-amine; (163) 3-[[4-(aminomethyl)phenyl]methyl]-4-isopropoxy-N2-propyl- imidazo[4,5-d]pyridazine-2,7-diamine; (164) 3-[[4-(aminomethyl)phenyl]methyl]-2-(ethylaminomethyl)-4- isopropoxy-imidazo[4,5-d]pyridazin-7-amine; (165) 2-butyl-7-isopropoxy-1-(piperidin-4-ylmethyl)-1H-imidazo[4,5- d]pyridazin-4-amine; (166) 3-[[4-(1-amino-1-methyl-ethyl)phenyl]methyl]-2-butyl-4-isopropoxy- imidazo[4,5-d]pyridazin-7-amine; (167) 2-butyl-7-(2,5-dihydro-1H-pyrrol-3-yl)-1-methyl-imidazo[4,5- d]pyridazin-4-amine; (168) 2-butyl-3-methyl-4-piperazin-1-yl-imidazo[4,5-d]pyridazin-7-amine; or a pharmaceutically acceptable salt thereof. Among the compounds of formula (A), of formula (A1) or of formula (A2) that are subject matter of the present disclosure, a group of compounds is composed of the compounds wherein: R1 represents: - a (C1-C6)alkyl- group, in particular a methyl group; - a NH2-(C1-C6)alkyl- group, in particular a NH2-(CH2)5- group; - a phenyl(C1-C6)alkyl- group, in particular a phenyl-CH2- group, being unsubstituted or substituted by at least one substituent, in particular substituted on the phenyl ring by at least one substituent, for instance by one substituent, selected from: - a (C1-C6)alkyl- group, in particular a methyl group (or a -CH2- group if substituted) or an isopropyl group (or a -CH(CH3)2- group if substituted), being unsubstituted or substituted by at least one substituent, in particular by one substituent, selected from: - a -NR4R5group wherein R4and R5, being independently from each other selected from: a hydrogen atom and a (C1-C16)alkyl- group, in particular a methyl group, for instance -NR4R5is -NH2or -NH(CH3); or R4and R5form together with the nitrogen atom to which they are attached an unsubstituted (C3-C10)membered heterocycloalkyl- group comprising one to four heteroatoms selected from oxygen, nitrogen and sulfur, in particular an unsubstituted (C3-C10)membered heterocycloalkyl- group comprising two nitrogen atoms, for instance a piperazinyl group; or - a (C3-C10)cycloalkyl(C1-C6)alkyl- group, in particular a cyclohexyl-CH2- group, being unsubstituted or substituted, in particular substituted on the (C3-C10)cycloalkyl- group, by at least one substituent, in particular by one substituent, selected from -NH2and a NH2-(C1- C6)alkyl- group such as a NH2-CH2- group; R2 represents : - a (C1-C6)alkyl- group, in particular a -(CH2)3-CH3 group; - a (C1-C6)alkylthio- group, in particular a -S-(CH2)2-CH3 group; or - a (C1-C6)alkyl-NH- group, in particular a -NH-(CH2)2-CH3 group; and R3 represents : - a -OR6 group wherein R6 is a (C1-C6)alkyl- group, in particular a -O-isopropyl group (that is to say a -O-CH(CH3)2 group); - a -NR7R8group wherein R7and R8form together with the nitrogen atom to which they are attached a (C3-C10)membered heterocycloalkyl- group comprising one to four heteroatoms selected from oxygen, nitrogen, and sulfur, in particular comprising two nitrogen atoms, for instance a piperazinyl group; or - a (C3-C10)membered heterocycloalkyl- group comprising one to four heteroatoms selected from oxygen, nitrogen and sulfur, in particular one nitrogen atom or two nitrogen atoms, for instance a dihydropyrrolyl group such as a 2,5-dihydro-1H-pyrrolyl group, or a piperazinyl group. Among the compounds of formula (A), of formula (A1) or of formula (A2) that are subject matter of the present disclosure, a group of compounds is composed of the compounds for which the drug (or drug unit) A is a TLR7 agonist and in particular is selected from the group consisting of: ^(1) 2-butyl-7-isopropoxy-1-(4-methoxybenzyl)-1H-imidazo[4,5-d]pyridazin-4- amine; (2) 2-butyl-N7-isopropyl-1-(4-methoxybenzyl)-1H-imidazo[4,5-d]pyridazine- 4,7-diamine; (3) 2-butyl-7-(isopropylthio)-1-(4-methoxybenzyl)-1H-imidazo[4,5- d]pyridazin-4-amine; (4) 2-butyl-1-(4-methoxybenzyl)-7-(2-methoxyethoxy)-1H-imidazo[4,5- d]pyridazin-4-amine; (5) 2-butyl-1-(4-methoxybenzyl)-7-propoxy-1H-imidazo[4,5-d]pyridazin-4- amine; (6) 7-(allyloxy)-2-butyl-1-(4-methoxybenzyl)-1H-imidazo[4,5-d]pyridazin-4- amine; (7) 7-(sec-butoxy)-2-butyl-1-(4-methoxybenzyl)-1H-imidazo[4,5-d]pyridazin- 4-amine; (8) 7-butoxy-2-butyl-1-(4-methoxybenzyl)-1H-imidazo[4,5-d]pyridazin-4- amine; (9) 2-butyl-7-(cyclopentyloxy)-1-(4-methoxybenzyl)-1H-imidazo[4,5- d]pyridazin-4-amine; (10) 2-butyl-1-(4-methoxybenzyl)-7-(pyrrolidin-1-yl)-1H-imidazo[4,5- d]pyridazin-4-amine; (11) 2-butyl-1-(4-methoxybenzyl)-7-(1-methyl-1H-pyrrol-3-yl)-1H- imidazo[4,5d] pyridazin-4-amine; (12) (E)-2-butyl-1-(4-methoxybenzyl)-7-(3-methylbut-1-en-1-yl)-1H- imidazo[4,5-d]pyridazin-4-amine; (13) 2-butyl-7-isopentyl-1-(4-methoxybenzyl)-1H-imidazo[4,5-d]pyridazin-4- amine; (14) 2-butyl-1-(4-methoxybenzyl)-7-(1H-pyrrol-3-yl)-1H-imidazo[4,5- d]pyridazin-4-amine; (15) 2-butyl-7-(cyclopent-1-en-1-yl)-1-(4-methoxybenzyl)-1H-imidazo[4,5- d]pyridazin-4-amine hydrochloride; (16) 2-butyl-7-cyclopentyl-1-(4-methoxybenzyl)-1H-imidazo[4,5-d]pyridazin- 4-amine; (17) 2-butyl-1-(4-methoxybenzyl)-7-(prop-1-en-2-yl)-1H-imidazo[4,5- d]pyridazin-4-amine; (18) 2-butyl-7-isopropyl-1-(4-methoxybenzyl)-1H-imidazo[4,5-d]pyridazin-4- amine; (19) 4-(aminomethyl)cyclohexyl)methyl)-2-butyl-7-isopropoxy-1H- imidazo[4,5-d]pyridazin-4-amine dihydrochloride; (20) 4-(aminomethyl)cyclohexyl)methyl)-2-butyl-7-isopropoxy-1H- imidazo[4,5-d]pyridazin-4-amine 2,2,2-trifluoroacetate; (25) Trans 1-(4-aminocyclohexyl)methyl)-2-butyl-7-isopropoxy-1H- imidazo [4,5-d]pyridazin-4-amine; (26) 1-((5-(aminomethyl)pyridin-2-yl)methyl)-2-butyl-7-isopropoxy-1H- imidazo[4,5-d]pyridazin-4-amine; (27) 6-((4-amino-2-butyl-7-isopropoxy-1H-imidazo[4,5-d]pyridazin-1- yl)methyl)nicotinonitrile; (28) N-(4-((4-amino-2-butyl-7-isopropoxy-1H-imidazo[4,5d]pyridazin-1- yl)methyl)benzyl)acetamide; (29) N-(4-((4-amino-2-butyl-7-isopropoxy-1H-imidazo[4,5-d]pyridazin-1- yl)methyl)benzyl)undecanamide; (30) N-(4-((4-amino-2-butyl-7-isopropoxy-1H-imidazo[4,5-d]pyridazin-1- yl)methyl)benzyl)pentanamide; (31) N-(4-((4-amino-2-butyl-7-isopropoxy-1H-imidazo[4,5-d]pyridazin-1- yl)methyl)benzyl)-3-(2-methoxyethoxy)propenamide; (34) 4-((4-amino-2-butyl-7-isopropoxy-1H-imidazo[4,5-d]pyridazin-1- yl)methyl)benzaldehyde; (35) (4-((4-amino-2-butyl-7-isopropoxy-1H-imidazo[4,5-d]pyridazin-1- yl)methyl)phenyl)methanol; (37) 3-((4-((4-amino-2-butyl-7-isopropoxy-1H-imidazo[4,5-d]pyridazin- yl)methyl)benzyl)amino)thietane 1,1-dioxide; (48) 2-butyl-7-ethoxy-1-(4-methoxybenzyl)-1H-imidazo[4,5-d]pyridazin-4- amine; (49) 2-butyl-1-(4-methoxybenzyl)-N7-(2-methoxyethyl)-1H-imidazo[4,5- d]pyridazine-4,7-diamine; (50) 2-butyl-7-methoxy-1-(4-methoxybenzyl)-1H-imidazo[4,5-d]pyridazin-4- amine; (51) 2-butyl-7-cyclohexyl-1-(4-methoxybenzyl)-1H-imidazo[4,5-d]pyridazin- 4-amine; (52) 7-(benzyloxy)-2-butyl-1-(4-methoxybenzyl)-1H-imidazo[4,5-d]pyridazin- 4-amine; (53) 2-butyl-1-(4-methoxybenzyl)-N7-methyl-1H-imidazo[4,5-d]pyridazine- 4,7-diamine; (54) (S)-2-butyl-1-(4-methoxybenzyl)-7-((tetrahydrofuran-3-yl)oxy)-1H- imidazo[4,5-d]pyridazin-4-amine; (55) 2-butyl-7-(furan-2-yl)-1-(4-methoxybenzyl)-1H-imidazo[4,5-d]pyridazin- 4-amine; (56) 2-butyl-1-(4-methoxybenzyl)-7-((tetrahydrofuran-3-yl)oxy)-1H- imidazo[4,5-d]pyridazin-4-amine; (57) 2-butyl-1-(4-methoxybenzyl)-7-((tetrahydro-2H-pyran-4-yl)oxy)-1H- imidazo[4,5-d]pyridazin-4-amine; (58) 2-butyl-1-(4-methoxybenzyl)-7-((tetrahydrothiophen-3-yl)oxy)-1H- imidazo[4,5-d]pyridazin-4-amine; (59) 2-butyl-1-(4-methoxybenzyl)-7-(tetrahydrofuran-3-yl)-1H-imidazo[4,5- d]pyridazin-4-amine; (60) 2-butyl-1-(4-methoxybenzyl)-7-(2-methylprop-1-en-1-yl)-1H- imidazo[4,5-d]pyridazin-4-amine; (61) 2-butyl-7-isobutyl-1-(4-methoxybenzyl)-1H-imidazo[4,5-d]pyridazin-4- amine; (62) 2-butyl-1-(4-methoxybenzyl)-7-(thiophen-3-yl)-1H-imidazo[4,5- d]pyridazin-4-amine; (63) 2-butyl-1-(4-methoxybenzyl)-7-(thiophen-2-yl)-1H-imidazo[4,5- d]pyridazin-4-amine; (64) 2-butyl-1-(4-methoxybenzyl)-7-(1H-pyrrol-2-yl)-1H-imidazo[4,5- d]pyridazin-4-amine hydrochloride; (65) 3-((4-amino-2-butyl-1-(4-methoxybenzyl)-1H-imidazo[4,5-d]pyridazin-7- yl)oxy)tetrahydrothiophene 1-oxide isomer A; (66) 2-butyl-7-(cyclohex-1-en-1-yl)-1-(4-methoxybenzyl)-1H-imidazo[4,5- d]pyridazin-4-amine; (67) 2-butyl-7-(furan-3-yl)-1-(4-methoxybenzyl)-1H-imidazo[4,5-d]pyridazin- 4-amine; (68) 3-((4-amino-2-butyl-1-(4-methoxybenzyl)-1H-imidazo[4,5-d]pyridazin-7- yl)oxy)tetrahydrothiophene 1,1-dioxide; (69) 3-((4-amino-2-butyl-1-(4-methoxybenzyl)-1H-imidazo[4,5-d]pyridazin-7- yl)oxy)tetrahydrothiophene 1-oxide isomer B; (70) 2-butyl-1-(4-methoxybenzyl)-7-(1-methyl-1H-pyrrol-2-yl)-1H- imidazo[4,5-d]pyridazin-4-amine hydrochloride; (71) 2-butyl-1-(4-methoxybenzyl)-N7,N7-dimethyl-1H-imidazo[4,5- d]pyridazine-4,7-diamine; (72) 2-butyl-1-(4-methoxybenzyl)-7-phenoxy-1H-imidazo[4,5-d]pyridazin-4- amine; (73) 2-butyl-7-(2,5-dihydrofuran-3-yl)-1-(4-methoxybenzyl)-1H-imidazo[4,5- d]pyridazin-4-amine; (75) 2-butyl-7-isopropoxy-1-(pyridin-2-ylmethyl)-1H-imidazo[4,5-d]pyridazin- 4-amine; (76) 2-butyl-7-isopropoxy-1-(pyridin-4-ylmethyl)-1H-imidazo[4,5-d]pyridazin- 4-amine 2,2,2-trifluoroacetate; (77) 1-(5-aminopentyl)-2-butyl-7-isopropoxy-1H-imidazo[4,5-d]pyridazin-4- amine; (78) 2-butyl-7-isopropoxy-1-(2-(piperidin-4-yl)ethyl)-1H-imidazo[4,5- d]pyridazin-4-amine; (79) 2-butyl-7-isopropoxy-1-(2-(piperazin-1-yl)ethyl)-1H-imidazo[4,5- d]pyridazin-4-amine; (80) 1-benzyl-2-butyl-7-isopropoxy-1H-imidazo[4,5-d]pyridazin-4-amine hydrochloride; (81) 2-butyl-1-(cyclohexylmethyl)-7-isopropoxy-1H-imidazo[4,5-d]pyridazin- 4-amine hydrochloride; (87) N7-(4-(aminomethyl)benzyl)-2-butyl-1-methyl-1H-imidazo[4,5- d]pyridazine-4,7-diamine; (92) 2-butyl-1-(4-methoxybenzyl)-7-phenyl-1H-imidazo[4,5-d]pyridazin-4- amine; (94) 2-butyl-N7-(3-(furan-2-yl)propyl)-1-(4-methoxybenzyl)-1H-imidazo[4,5- d]pyridazine-4,7-diamine; (97) 2-butyl-1-(4-methoxybenzyl)-7-(1-methyl-1H-pyrazol-4-yl)-1H- imidazo[4,5-d]pyridazin-4-amine; and a pharmaceutically acceptable salt thereof. Among the compounds of formula (A), of formula (A1) or of formula (A2) that are subject matter of the present disclosure, a group of compounds is composed of the compounds for which the drug (or drug unit) A is a TLR7 / 8 agonist and in particular is selected from the group consisting of: (21) 1-(4-(aminomethyl)benzyl)-2-butyl-7-isopropoxy-1H-imidazo[4,5- d]pyridazin-4-amine; (22) 1-(4-(aminomethyl)benzyl)-2-butyl-7-isopropoxy-1H-imidazo[4,5- d]pyridazin-4-amine 2,2,2-trifluoroacetate; (23) 1-(((1S,3R)-3-aminocyclohexyl)methyl)-2-butyl-7-isopropoxy-1H- imidazo[4,5-d]pyridazin-4-amine (and enantiomer); (24) 1-(4-amino-2-butyl-7-isopropoxy-1H-imidazo[4,5-d]pyridazin-1-yl)-2- methylpropan-2-ol; (32) 1-(((1S,3S)-3-aminocyclohexyl)methyl)-2-butyl-7-isopropoxy-1H- imidazo[4,5-]pyridazin-4-amine (and enantiomer); (33) 1-(3-(aminomethyl)benzyl)-2-butyl-7-isopropoxy-1H-imidazo[4,5- d]pyridazin-4-amine 2,2,2-trifluoroacetate; (36) 2-butyl-1-(4-((cyclopropylamino)methyl)benzyl)-7-isopropoxy-1H- imidazo[4,5-d]pyridazin-4-amine; (39) 2-butyl-7-isopropoxy-1-(4-(((1-methylcyclobutyl)amino)methyl)benzyl)- 1H-imidazo[4,5-d]pyridazin-4-amine; (40) 2-butyl-7-isopropoxy-1-(4-(piperazin-1-ylmethyl)benzyl)-1H-imidazo[4,5- d]pyridazin-4-amine; (41) 2-butyl-N7,N7,1-trimethyl-1H-imidazo[4,5-d]pyridazine-4,7-diamine; (42) 2-butyl-1-methyl-7-(pyrrolidin-1-yl)-1H-imidazo[4,5-d]pyridazin-4- amine; (43) 2-butyl-N7-(4-((dimethylamino)methyl)benzyl)-N7,1-dimethyl-1H- imidazo[4,5-d]pyridazine-4,7-diamine; (44) 2-butyl-N7,1-dimethyl-N7-(4-(morpholinomethyl)benzyl)-1H- imidazo[4,5-d]pyridazine-4,7-diamine; (45) 4-(((4-amino-2-butyl-1-methyl-1H-imidazo[4,5-d]pyridazin-7- yl)(methyl)amino)methyl)benzonitrile; (46) N7-(4-(aminomethyl)benzyl)-2-butyl-N7,1-dimethyl-1H-imidazo[4,5- d]pyridazine-4,7-diamine; (47) 2-butyl-N7-(4-(((2-methoxyethyl)(methyl)amino)methyl)benzyl)-N7,1- dimethyl-1H-imidazo[4,5-d]pyridazine-4,7-diamine; (74) 2-butyl-7-isopropoxy-1-(pyridin-3-ylmethyl)-1H-imidazo[4,5-d]pyridazin- 4-amine; (82) 2-butyl-7-isopropoxy-1-(4-(((tetrahydro-2H-pyran-4- yl)amino)methyl)benzyl)-1H-imidazo[4,5-d]pyridazin-4-amine hydrochloride; (83) 2-butyl-7-isopropoxy-1-(4-((isopropylamino)methyl)benzyl)-1H- imidazo[4,5-d]pyridazin-4-amine dihydrochloride; (84) N-(4-((4-amino-2-butyl-7-isopropoxy-1H-imidazo[4,5-d]pyridazin-1- yl)methyl)benzyl)heptanamide; (85) (4-(1-(4-amino-2-butyl-1-methyl-1H-imidazo[4,5-d]pyridazin-7- yl)pyrrolidin-3-yl)phenyl)methanol hydrochloride; (86) 2-butyl-7-isopropoxy-1-methyl-1H-imidazo[4,5-d]pyridazin-4-amine; (88) 2-butyl-N7-isopropyl-1-methyl-1H-imidazo[4,5-d]pyridazine-4,7-diamine; (89) 2-butyl-1-methyl-7-(3-phenylpyrrolidin-1-yl)-1H-imidazo[4,5- d]pyridazin-4-amine; (90) N7-benzyl-2-butyl-N7,1-dimethyl-1H-imidazo[4,5-d]pyridazine-4,7- diamine; (91) 2-butyl-1-methyl-N7-(4-((4-methylpiperazin-1-yl)methyl)benzyl)-1H- imidazo[4,5-d]pyridazine-4,7-diamine; (95) 2-butyl-1-(4-methoxybenzyl)-1H-imidazo[4,5-d]pyridazin-4-amine; (98) 2-butyl-N7-isopropyl-1H-imidazo[4,5-d]pyridazine-4,7-diamine; (99) 2-butyl-7-(isopropylthio)-1H-imidazo[4,5-d]pyridazin-4-amine; (118) 2-butyl-7-isopropoxy-1-(4-((methylamino)methyl)benzyl)-1H- imidazo[4,5-d]pyridazin-4-amine; (161) 3-[[4-(aminomethyl)phenyl]methyl]-4-isopropoxy-2-propylsulfanyl- imidazo[4,5-d]pyridazin-7-amine; (163) 3-[[4-(aminomethyl)phenyl]methyl]-4-isopropoxy-N2-propyl- imidazo[4,5-d]pyridazine-2,7-diamine; (166) 3-[[4-(1-amino-1-methyl-ethyl)phenyl]methyl]-2-butyl-4-isopropoxy- imidazo[4,5-d]pyridazin-7-amine; (167) 2-butyl-7-(2,5-dihydro-1H-pyrrol-3-yl)-1-methyl-imidazo[4,5- d]pyridazin-4-amine; (168) 2-butyl-3-methyl-4-piperazin-1-yl-imidazo[4,5-d]pyridazin-7-amine; and a pharmaceutically acceptable salt thereof. Among the compounds of formula (A), of formula (A1) or of formula (A2) that are subject matters of the disclosure, a group of compounds is composed of the compounds for which the drug (or drug unit) A is selected from the group consisting of: ;

[0009] . Among the compounds of formula (A), of formula (A1) or of formula (A2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which A is selected from the group consisting of: ;

[0010] ; Among the compounds of formula (A), of formula (A1) or of formula (A2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which A is selected from the group consisting of:

[0011] . Among the compounds of formula (A), of formula (A1) or of formula (A2) that are subject matter of the present disclosure, a group of compounds is composed of the compounds for which the drug (or drug unit) A is further low or non – cell permeable, in particular the low or non - cell permeable drug unit A is defined by a PAMPA below 25. Among the compounds of formula (A), of formula (A1) or of formula (A2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which A is selected from the group consisting of:

[0012] . Among the compounds of formula (I) that are subject-matter of the present disclosure, a group of compounds is composed of the compounds wherein: A is of formula (A) in which: R1 represents: - a (C1-C6)alkyl- group, in particular a methyl group; - a NH2-(C1-C6)alkyl- group, in particular a NH2-(CH2)5- group; - a phenyl(C1-C6)alkyl- group, in particular a phenyl-CH2- group, being unsubstituted or substituted by at least one substituent, in particular substituted on the phenyl ring by at least one substituent, for instance by one substituent, selected from: - a (C1-C6)alkyl- group, in particular a methyl group (or a -CH2- group if substituted) or an isopropyl group (or a -CH(CH3)2- group if substituted), being unsubstituted or substituted by at least one substituent, in particular by one substituent, selected from: - a -NR4R5 group wherein R4 and R5, being independently from each other selected from: a hydrogen atom and a (C1-C16)alkyl- group, in particular a methyl group, for instance -NR4R5is -NH2or -NH(CH3); or R4and R5form together with the nitrogen atom to which they are attached an unsubstituted (C3-C10)membered heterocycloalkyl- group comprising one to four heteroatoms selected from oxygen, nitrogen and sulfur, in particular an unsubstituted (C3-C10)membered heterocycloalkyl- group comprising two nitrogen atoms, for instance a piperazinyl group; or - a (C3-C10)cycloalkyl(C1-C6)alkyl- group, in particular a cyclohexyl-CH2- group, being unsubstituted or substituted, in particular substituted on the (C3-C10)cycloalkyl- group, by at least one substituent, in particular by one substituent, selected from -NH2and a NH2-(C1- C6)alkyl- group such as a NH2-CH2- group; R2 represents : - a (C1-C6)alkyl- group, in particular a -(CH2)3-CH3group; - a (C1-C6)alkylthio- group, in particular a -S-(CH2)2-CH3 group; or - a (C1-C6)alkyl-NH- group, in particular a -NH-(CH2)2-CH3 group; and R3 represents : - a -OR6 group wherein R6 is a (C1-C6)alkyl- group, in particular a -O-isopropyl group (that is to say a -O-CH(CH3)2 group); - a -NR7R8group wherein R7and R8form together with the nitrogen atom to which they are attached a (C3-C10)membered heterocycloalkyl- group comprising one to four heteroatoms selected from oxygen, nitrogen, and sulfur, in particular comprising two nitrogen atoms, for instance a piperazinyl group; or - a (C3-C10)membered heterocycloalkyl- group comprising one to four heteroatoms selected from oxygen, nitrogen and sulfur, in particular one nitrogen atom or two nitrogen atoms, for instance a dihydropyrrolyl group such as a 2,5-dihydro-1H-pyrrolyl group, or a piperazinyl group; L1 represents: *-C(O)-O-CH2-para-phenyl-NH-Cit-Val-Glu-C(O)-(CH2)3-C(O)-NH-(CH2- CH2-O)3-(CH2)2-** ; *-C(O)-O-CH2-para-phenyl-NH-Ala-Val-Glu-C(O)-(CH2)3-C(O)-NH-(CH2- CH2-O)3-(CH2)2-**; *-Cit-Val-C(O)-(CH2-CH2-O)3-(CH2)2-NH-C(O)-(CH2)2-**; *-Cit-Val-C(O)-(CH2)3-C(O)-NH-(CH2-CH2-O)3-(CH2)2-**; *-Ala-Val-C(O)-(CH2)3-C(O)-NH-(CH2-CH2-O)3-(CH2)2-**; *-C(O)-O-CH2-para-phenyl-NH-Cit-Val-Glu-C(O)-(CH2)3-C(O)-NH-(CH2- CH2-O)3-(CH2)2-NH-C(O)-(CH2)2-** ; *-C(O)-O-CH2-para-phenyl-NH-Ala-Val-Glu--C(O)-(CH2)3-C(O)-NH-(CH2- CH2-O)3-(CH2)2-NH-C(O)-(CH2)2-**; *-Cit-Val-C(O)-(CH2)3-C(O)-NH-(CH2-CH2-O)3-(CH2)2-NH-C(O)-(CH2)2-**; *-Ala-Val-C(O)-(CH2)3-C(O)-NH-(CH2-CH2-O)3-(CH2)2-NH-C(O)-(CH2)2-**, *-C(O)-(CH2-CH2-O)24-CH2-CH2-**; *-(CH2-CH2-O)23-CH2-CH2-**; *-C(O)-(CH2-CH2-O)20-CH2-CH2-**; *-C(O)-(CH2-CH2-O)16-CH2-CH2-**; *-C(O)-(CH2-CH2-O)12-CH2-CH2-**; *-C(O)-(CH2-CH2-O)8-CH2-CH2-**; *-C(O)-C(CH3)2-CH2-O-(CH2-CH2-O)20-CH2-CH2-**; *-C(O)-O-(CH2-CH2-O)20-CH2-CH2-**; *-C(O)-(CH2-CH2-O)24-CH2-CH2-NH-C(O)-CH2-CH2-**; *-C(O)-(CH2-CH2-O)20-CH2-CH2-NH-C(O)-CH2-CH2-**; or *-C(O)-(CH2-CH2-O)12-CH2-CH2-NH-C(O)-CH2-CH2-**; the single asterisk (*) indicating the site of covalent attachment to the A drug unit radical and the double asterisk (**) indicating the site of covalent attachment to the -RCG1 group; and RCG1 is N 3-, a -COOH group, or a maleimido group . According to a particular embodiment, the compounds of formula (I) or a pharmaceutically acceptable salt thereof are chosen among compounds of formula (I1) and compounds of formula (I2): A-(La)m-(AA)w-(Lb)p-Lc-Ld’-RCG1 (I1) wherein: - A is as defined in formula (I); - La represents a self immolative linker, for instance a *-C(O)-O-(CR14R15)-aryl-NR16-** group, *-C(O)-O-(CR14R15)-heteroaryl-NR16-** group, a *-C(O)-NR17-(C2-C6)alkyl-NR18- **, a *-C(O)-NR17-(C2-C6)alkyl-NR18-C(O)-O-CR15R14-aryl-NR16-** group, a *-C(O)- NR17-(C2-C6)alkyl-NR18-C(O)-O-CR15R14-heteroaryl-NR16-** group, a *-CR15R14-aryl- NR16-** group or a *-CR15R14-heteroaryl-NR16-** group, aryl being a (C6-C10) membered aryl group and heteroaryl being a (C5-C10) membered heteroaryl group comprising one to four heteroatoms selected from oxygen, nitrogen and sulfur, for instance a *-C(O)-O-CH2- phenyl-NH-** group, the single asterisk (*) indicating the site of covalent attachment to the A drug unit radical and the double asterisk (**) indicating the site of covalent attachment to the (AA)w radical; R14, R15, R16, R17and R18being a hydrogen atom or a (C1-C6)alkyl group; group; - m represents an integer from 0 to 1; - (AA)w represents a sequence of w amino acids AA connected together via peptide bonds; w representing an integer ranging from 1 to 12, for instance from 1 to 6, such as 2 and 3; AA denoting a natural or unnatural amino acid, of configuration D or L, chosen from: alanine (Ala), β-alanine, γ-aminobutyric acid, 2-amino-2-cyclohexylacetic acid, 2-amino-2-phenylacetic acid, arginine (Arg), asparagine (Asn), aspartic acid (Asp), citrulline (Cit), cysteine (Cys), α,α-dimethyl- γ-aminobutyric acid, β,β-dimethyl-γ- aminobutyric acid, glutamine (Gln), glutamic acid (Glu), glycine (Gly), histidine (His), isoleucine (Ile), leucine (Leu), lysine (Lys), ε-acetyl-lysine (AcLys), methionine (Met), ornithine (Orn), phenylalanine (Phe), proline (Pro), serine (Ser), threonine (Thr), tryptophan (Trp), tyrosine (Tyr), and valine (Val), for instance valine (Val), citrulline (Cit), alanine (Ala), and glutamic acid (Glu) ; - Lb represents a spacer, for instance a *-C(O)-(C1-C6)alkyl-C(O)-NH-** group or a *-C(O)- ** group, such as a *-C(O)-(CH2)3-C(O)-NH-** group or a *-C(O)-** group, the single asterisk (*) indicating the site of covalent attachment to the (AA)w radical and the double asterisk (**) indicating the site of covalent attachment to the Lc radical; - p represents an integer from 0 to 1; - Lc represents a spacer, for instance a *–(CH2-CH2-O)n-** group in which n represents an integer from 2 to 12, for instance from 3 to 7, such as 3 and 4 , the single asterisk (*) indicating the site of covalent attachment to the Lb radical if present (that is to say if p is 1) or directly to the (AA)w radical if Lb is not present (that is to say if p is 0) and the double asterisk (**) indicating the site of covalent attachment to the Ld’ radical; - Ld’ represents a spacer, for instance a *-(C2-C6)alkyl-** group, a *-(C2-C6)alkyl-NH- C(O)-(C2-C6)alkyl-** group or a *-(C2-C6)alkyl-C(O)-NH-(C2-C6)alkyl-** group, such as a *–(CH2)2-** group, a *-(CH2)2-NH-C(O)-(CH2)2-** group or a *-(CH2)2-C(O)-NH-(CH2)2- ** group, the single asterisk (*) indicating the site of covalent attachment to the Lc radical and the double asterisk (**) indicating the site of covalent attachment to the RCG1 radical; and -RCG1 represents a reactive chemical group that is reactive towards a chemical group present on a binding agent, for instance on a protein, a polypeptide, a ligand, a peptide, an oligonucleotide or an oligosaccharide, for instance on a targeting agent for instance on a cell- binding agent such as an antibody such as a monoclonal antibody or a VHH antibody. - For instance, RCG1 represents: (i) a RaZa-C(=O)- reactive group for which: Zarepresents a single bond, -O- or -NH, such as -O-, and Ra represents a hydrogen atom, a -(C1-C6)alkyl group, a -(C3-C7)cycloalkyl group, a -(C2-C6)alkenyl group, a -(C6-C10)aryl group, a -(C5-C10)heteroaryl group comprising 4 to 9 carbon atoms and 1 to 4 heteroatom(s) selected from oxygen, nitrogen, and sulfur, or a -(C3-C7)heterocycloalkyl group comprising 2 to 6 carbon atoms and 1 to 4 heteroatom(s) selected from oxygen, nitrogen, sulfur, -S(O)- and -SO2-, said -(C6-C10)aryl group, -(C5-C10)heteroaryl group and / or -(C3-C7)heterocycloalkyl group being optionally substituted by 1 to 5 atoms / groups chosen from a halogen atom, such as a fluorine atom, a - (C1-C6)alkyl group, a -(C1-C6)alkoxy group, a hydroxyl group, an oxo group, a nitro group and a cyano group; or O N (ii) one of the following reactive groups: a maleimido O group; a substituted maleimido group such as ; a haloacetamido R21 O group with R21representing a hydrogen atom or a (C1-C6)alkyl group, such as a methyl group; Cl-; N3-; HO-; HS-; an activated disulfide such as ; H2N-; HC≡C- or an activated C≡C such as a cyclooctyne moiety for instance a DBCO- a group ; aOgroup; an O-alkyl hydroxylamine or a Pictet-Spengler reaction substrate for instance RCG1is N3-, a maleimido group O , a substituted maleimido group A-(P)o-L-Ld-RCG1 (I2) wherein - A is as defined in formula (I); - P represents a -C(O)- group, a -C(O)-O- group, a -S(O2)- group, a -C(O)-C(CH3)2-CH2-O- group, a -C(O)-NH- group, group, - o represents an integer from 0 to 1; - L represents a *–(CH2-CH2-O)n-** group in which n represents an integer from 1 to 30, for instance from 8 to 25, such as 8, 12, 16, 20, 23 and 24 , the single asterisk (*) indicating the site of covalent attachment to the P radical if present (that is to say if o is 1) or directly to the A radical if P is not present (that is to say if o is 0) and the double asterisk (**) indicating the site of covalent attachment to the Ld radical; - Ld represents a spacer, for instance a *-(C2-C6)alkyl-** group, a *-(C2-C6)alkyl-NH-C(O)- (C2-C6)alkyl-** group or a *-(C2-C6)alkyl-C(O)-NH-(C2-C6)alkyl-** group, such as a *– (CH2)2-** group, a *-(CH2)2-NH-C(O)-(CH2)2-** group or a *-(CH2)2-C(O)-NH-(CH2)2-** group, the single asterisk (*) indicating the site of covalent attachment to the L radical and the double asterisk (**) indicating the site of covalent attachment to the RCG1 radical; and - RCG1 represents a reactive chemical group that is reactive towards a chemical group present on a binding agent, for instance on a protein, a polypeptide, a ligand, a peptide, an oligonucleotide or an oligosaccharide, for instance on a targeting agent for instance on a cell- binding agent such as an antibody such as a monoclonal antibody or a VHH antibody. - For instance, RCG1 represents: (i) a RaZa-C(=O)- reactive group for which: Za represents a single bond, -O- or -NH, such as -O-, and Rarepresents a hydrogen atom, a -(C1-C6)alkyl group, a -(C3-C7)cycloalkyl group, a -(C2-C6)alkenyl group, a -(C6-C10)aryl group, a -(C5-C10)heteroaryl group comprising 4 to 9 carbon atoms and 1 to 4 heteroatom(s) selected from oxygen, nitrogen, and sulfur, or a -(C3-C7)heterocycloalkyl group comprising 2 to 6 carbon atoms and 1 to 4 heteroatom(s) selected from oxygen, nitrogen, sulfur, -S(O)- and -SO2-, said -(C6-C10)aryl group, -(C5-C10)heteroaryl group and / or -(C3-C7)heterocycloalkyl group being optionally substituted by 1 to 5 atoms / groups chosen from a halogen atom, such as a fluorine atom, a - (C1-C6)alkyl group, a -(C1-C6)alkoxy group, a hydroxyl group, an oxo group, a nitro group and a cyano group; or O N (ii) one of the following reactive groups: a maleimido O group; a substituted maleimido group such as ; a haloacetamido R21 N Cl, Br or I O group with R21representing a hydrogen atom or a (C1-C6)alkyl group, such as a methyl group; Cl-; N3-; HO-; HS-; an activated disulfide such as ; aOgroup ; aOgroup; an O-alkyl hydroxylamine or a Pictet-Spengler reaction substrate such for instance RCG1is N3-, a maleimido group , a substituted maleimido group Among the compounds of formula (I1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which A is of formula (A1) or of formula (A2) in which: R1, R2 and R3 are as defined in the present disclosure; the single asterisk (*) indicates the site of covalent attachment to -(La)m-(AA)w-(Lb)p-Lc- Ld’-RCG1; R1* represents: - either a single bond, which means that -(La)m-(AA)w-(Lb)p-Lc-Ld’-RCG1 is directly linked to the nitrogen atom of the imidazo[4,5-d]pyridazine ring, - or a divalent radical formed from R1as defined in the present disclosure, which means that -(La)m-(AA)w-(Lb)p-Lc-Ld’-RCG1 is linked to the nitrogen atom of the imidazo[4,5-d]pyridazine ring via R1; R3* represents: - either a single bond, which means that -(La)m-(AA)w-(Lb)p-Lc-Ld’-RCG1 is directly linked to the carbon atom of the imidazo[4,5-d]pyridazine ring, - or a divalent radical formed from R3as defined in the present disclosure, which means that -(La)m-(AA)w-(Lb)p-Lc-Ld’-RCG1 is linked to the carbon atom of the imidazo[4,5-d]pyridazine ring via R3. According to one particular embodiment, A is of formula (A1). According to another embodiment, A is of formula (A2). Thus, according to a particular embodiment, when R1* represents a single bond, the compounds of formula (I1) or a pharmaceutically acceptable salt thereof in accordance with the present disclosure have the following formula (Ia1): wherein R2, R3, La, m, AA, w, Lb, p, Lc, Ld’ and RCG1 are as defined in the present disclosure. This means that in this particular embodiment, in the drug A, R1 is a hydrogen atom. According to another particular embodiment, when R1* represents a divalent radical formed from R1 as defined in the present disclosure, the compounds of formula (I1) or a pharmaceutically acceptable salt thereof in accordance with the present disclosure have the following formula (Iaa1):

[0013] wherein R2, R3, La, m, AA, w, Lb, p, Lc, Ld’ and RCG1 are as defined in the present disclosure and R1* is a divalent R1 as defined in the present disclosure. This means that in this particular embodiment, in the drug A, R1 is not a hydrogen atom. According to another particular embodiment, when R3* represents a single bond, the compounds of formula (I1) or a pharmaceutically acceptable salt thereof in accordance with the present disclosure have the following formula (Ib1): wherein R1, R2, La, m, AA, w, Lb, p, Lc, Ld’ and RCG1 are as defined in the present disclosure. This means that in this particular embodiment, in the drug A, R3 is a hydrogen atom. According to another particular embodiment, when R3* represents a divalent radical formed from R3 as defined in the present disclosure, the compounds of formula (I1) or a pharmaceutically acceptable salt thereof in accordance with the present disclosure have the following formula (Ibb1): wherein R1, R2, La, m, AA, w, Lb, p, Lc, Ld’ and RCG1 are as defined in the present disclosure and R3* is a divalent R3 as defined in the present disclosure. This means that in this particular embodiment, in the drug A, R3 is not a hydrogen atom. Among the compounds of formula (I1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which A is selected from the group consisting of: ;

[0014] . Among the compounds of formula (I1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which A is selected from the group consisting of:

[0015] . Among the compounds of formula (I1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which La is a self-immolative linker. Self immolative linkers are well known for the person of the art. La is a covalent assembly tailored to correlate the cleavage of two chemical bonds after activation of a protective part in a precursor. Thus, its list has not to be limited or restricted. For instance, La represents a *-C(O)-O-(CR14R15)-aryl-NR16-** group, *-C(O)-O- (CR14R15)-heteroaryl-NR16-** group, a *-C(O)-NR17-(C2-C6)alkyl-NR18-**, a *-C(O)-NR17-(C2-C6)alkyl-NR18-C(O)-O-CR15R14-aryl-NR16-** group, a *-C(O)-NR17-(C2-C6)alkyl- NR18-C(O)-O-CR15R14-heteroaryl-NR16-** group, a *-CR15R14-aryl-NR16-** group or a *- CR15R14-heteroaryl-NR16-** group, aryl being a (C6-C10) membered aryl group and heteroaryl being a (C5-C10) membered heteroaryl group comprising one to four heteroatoms selected from oxygen, nitrogen and sulfur, the single asterisk (*) indicating the site of covalent attachment to the A drug unit radical and the double asterisk (**) indicating the site of covalent attachment to the (AA)w radical, R14, R15, R16, R17and R18being a hydrogen atom or a (C1-C6)alkyl group. Among the compounds of formula (I1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which La represents a *-C(O)-O-CH2- phenyl-NH-** group, the single asterisk (*) indicating the site of covalent attachment to the A drug unit radical and the double asterisk (**) indicating the site of covalent attachment to the (AA)w radical. Among the compounds of formula (I1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which in (AA)w, w represents an integer from 1 to 6, and AA is chosen from valine (Val), citrulline (Cit), alanine (Ala), and glutamic acid (Glu). Among the compounds of formula (I1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which in (AA)w, w represents an integer 2 or 3, and AA is chosen from valine (Val), citrulline (Cit), alanine (Ala), and glutamic acid (Glu). For instance, the amino acid sequence (AA)w comprises a citrulline (Cit). For instance, the amino acid sequence (AA)w is chosen among Glu-Val-Cit; Glu-Val-Ala; Val-Cit or Val-Ala. For instance, when the amino acid sequence (AA)w is Glu-Val-Cit, the citrulline (Cit) is linked to La or to A (if La is absent, that is to say if m is 0) and the glutamic acid (Glu) is linked to Lb or to Lc (if Lb is absent, that is to say if p is 0). For instance, when the amino acid sequence (AA)w is Glu-Val-Ala, the alanine (Ala) is linked to La or to A (if La is absent, that is to say if m is 0) and the glutamic acid (Glu) is linked to Lb or to Lc (if Lb is absent, that is to say if p is 0). For instance, when the amino acid sequence (AA)w is Val-Cit, the citrulline (Cit) is linked to La or to A (if La is absent, that is to say if m is 0) and the valine (Val) is linked to Lb or to Lc (if Lb is absent, that is to say if p is 0). For instance, when the amino acid sequence (AA)w is Val-Ala, the alanine (Ala) is linked to La or to A (if La is absent, that is to say if m is 0) and the valine (Val) is linked to Lb or to Lc (if Lb is absent, that is to say if p is 0). For instance, the amino acid sequence (AA)w is Val-Cit. Among the compounds of formula (I1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which Lb represents a *-C(O)- (C1-C6)alkyl-C(O)-NH-** group or a *-C(O)-** group, the single asterisk (*) indicating the site of covalent attachment to the (AA)w radical and the double asterisk (**) indicating the site of covalent attachment to the Lc radical. Among the compounds of formula (I1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which Lb represents a *-C(O)- (CH2)3-C(O)-NH-** group or a *-C(O)-** group, the single asterisk (*) indicating the site of covalent attachment to the (AA)w radical and the double asterisk (**) indicating the site of covalent attachment to the Lc radical. Among the compounds of formula (I1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which Lc represents a *–(CH2- CH2-O)n-** group in which n represents an integer from 2 to 12, the single asterisk (*) indicating the site of covalent attachment to the Lb radical if present (that is to say if p is 1) or directly to the (AA)w radical if Lb is not present (that is to say if p is 0) and the double asterisk (**) indicating the site of covalent attachment to the Ld’ radical. Among the compounds of formula (I1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which Lc represents a *–(CH2- CH2-O)n-** group in which n represents an integer from 3 to 7, the single asterisk (*) indicating the site of covalent attachment to the Lb radical if present (that is to say if p is 1) or directly to the (AA)w radical if Lb is not present (that is to say if p is 0) and the double asterisk (**) indicating the site of covalent attachment to the Ld’ radical. Among the compounds of formula (I1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which Lc represents a *–(CH2- CH2-O)n-** group in which n represents an integer 3 or 4 , the single asterisk (*) indicating the site of covalent attachment to the Lb radical if present (that is to say if p is 1) or directly to the (AA)w radical if Lb is not present (that is to say if p is 0) and the double asterisk (**) indicating the site of covalent attachment to the Ld’ radical. Among the compounds of formula (I1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which Ld’ represents a *-(C2- C6)alkyl-** group, a *-(C2-C6)alkyl-NH-C(O)-(C2-C6)alkyl-** group or a *-(C2-C6)alkyl- C(O)-NH-(C2-C6)alkyl-** group, the single asterisk (*) indicating the site of covalent attachment to the Lc radical and the double asterisk (**) indicating the site of covalent attachment to the RCG1 radical. Among the compounds of formula (I1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which Ld’ represents a *–(CH2)2- ** group, a *-(CH2)2-NH-C(O)-(CH2)2-** group or a *-(CH2)2-C(O)-NH-(CH2)2-** group, the single asterisk (*) indicating the site of covalent attachment to the Lc radical and the double asterisk (**) indicating the site of covalent attachment to the RCG1 radical. Among the compounds of formula (I1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which m represents an integer 1. Among the compounds of formula (I1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which m represents 0. Among the compounds of formula (I1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which p represents an integer 1. Among the compounds of formula (I1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which p represents 0. Among the compounds of formula (I1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which RCG1 represents N3-, or a O N maleimido group O . Among the compounds of formula (I1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which when Ld’ represents a *-(C2-C6)alkyl-** group, the single asterisk (*) indicating the site of covalent attachment to the Lc radical and the double asterisk (**) indicating the site of covalent attachment to the RCG1 radical, then RCG1 represents N3-. Among the compounds of formula (I1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which when Ld’ represents a *-(C2-C6)alkyl-NH-C(O)-(C2-C6)alkyl-** group, the single asterisk (*) indicating the site of covalent attachment to the Lc radical and the double asterisk (**) indicating the site of covalent attachment to the RCG1 radical, then RCG1 represents a maleimido . Among the compounds of formula (I1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which when Ld’ represents a *-(CH2)2-** group, the single asterisk (*) indicating the site of covalent attachment to the Lc radical and the double asterisk (**) indicating the site of covalent attachment to the RCG1 radical, then RCG1 represents N3-. Among the compounds of formula (I1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which when Ld’ represents a *-(CH2)2-NH-C(O)-(CH2)2-** group, the single asterisk (*) indicating the site of covalent attachment to the Lc radical and the double asterisk (**) indicating the site of covalent attachment to the RCG1 radical, then RCG1 represents a maleimido group O . All these sub-groups taken alone or in combination are part of the present disclosure. According to a particular embodiment, the disclosure relates to a compound / payload of formula (I1) or a pharmaceutically acceptable salt thereof wherein A and RCG1 are as defined in the present disclosure, and La is *-C(O)-O-CH2-para-phenyl-NH**; m is 1; AA is selected from Ala, Val, Cit and Glu; w is 2 or 3; Lb is *-C(O)-(CH2)3-C(O)-NH-**; p is 1; Lc is *-(CH2-CH2-O)3-**; and Ld’ is *-(CH2)2-** or *-(CH2)2-NH-C(O)-(CH2)2-**. According to another particular embodiment, the disclosure relates to a compound / payload of formula (I1) or a pharmaceutically acceptable salt thereof wherein A and RCG1 are as defined in the present disclosure; m is 0; AA is selected from Ala, Val and Cit; w is 2; Lb is *-C(O)-(CH2)3-C(O)-NH-** or *-C(O)-**; p is 1; Lc is *-(CH2-CH2-O)3-**; and Ld’ is *-(CH2)2-** or *-(CH2)2-NH-C(O)-(CH2)2-**. According to another particular embodiment, the disclosure relates to a compound / payload of formula (I1) or a pharmaceutically acceptable salt thereof wherein the -(La)m-(AA)w-(Lb)p-Lc-Ld’- part is selected from the group consisting of: *-C(O)-O-CH2-para-phenyl-NH-Cit-Val-Glu-C(O)-(CH2)3-C(O)-NH-(CH2- CH2-O)3-(CH2)2-**; *-C(O)-O-CH2-para-phenyl-NH-Ala-Val-Glu-C(O)-(CH2)3-C(O)-NH-(CH2- CH2-O)3-(CH2)2-**; *-Cit-Val-C(O)-(CH2)3-C(O)-NH-(CH2-CH2-O)3-(CH2)2-**; *-Ala-Val-C(O)-(CH2)3-C(O)-NH-(CH2-CH2-O)3-(CH2)2-**; *-C(O)-O-CH2-para-phenyl-NH-Cit-Val-Glu-C(O)-(CH2)3-C(O)-NH-(CH2- CH2-O)3-(CH2)2-NH-C(O)-(CH2)2-**; *-C(O)-O-CH2-para-phenyl-NH-Ala-Val-Glu--C(O)-(CH2)3-C(O)-NH-(CH2- CH2-O)3-(CH2)2-NH-C(O)-(CH2)2-**; *-Cit-Val-C(O)-(CH2)3-C(O)-NH-(CH2-CH2-O)3-(CH2)2-NH-C(O)-(CH2)2-**; *-Ala-Val-C(O)-(CH2)3-C(O)-NH-(CH2-CH2-O)3-(CH2)2-NH-C(O)-(CH2)2-**, and *-Cit-Val-C(O)-(CH2-CH2-O)3-(CH2)2-NH-C(O)-(CH2)2-**, the single asterisk (*) indicating the site of covalent attachment to the A drug unit radical and the double asterisk (**) indicating the site of covalent attachment to the RCG1 radical. Among the compounds of formula (I1) that are subject-matter of the present disclosure, a group of compounds is composed of the compounds wherein: A is of formula (A) in which: R1 represents: - a (C1-C6)alkyl- group, in particular a methyl group; - a NH2-(C1-C6)alkyl- group, in particular a NH2-(CH2)5- group; - a phenyl(C1-C6)alkyl- group, in particular a phenyl-CH2- group, being unsubstituted or substituted by at least one substituent, in particular substituted on the phenyl ring by at least one substituent, for instance by one substituent, selected from: - a (C1-C6)alkyl- group, in particular a methyl group (or a -CH2- group if substituted) or an isopropyl group (or a -CH(CH3)2- group if substituted), being unsubstituted or substituted by at least one substituent, in particular by one substituent, selected from: - a -NR4R5group wherein R4and R5, being independently from each other selected from: a hydrogen atom and a (C1-C16)alkyl- group, in particular a methyl group, for instance -NR4R5 is -NH2 or -NH(CH3); or R4 and R5 form together with the nitrogen atom to which they are attached an unsubstituted (C3-C10)membered heterocycloalkyl- group comprising one to four heteroatoms selected from oxygen, nitrogen and sulfur, in particular an unsubstituted (C3-C10)membered heterocycloalkyl- group comprising two nitrogen atoms, for instance a piperazinyl group; or - a (C3-C10)cycloalkyl(C1-C6)alkyl- group, in particular a cyclohexyl-CH2- group, being unsubstituted or substituted, in particular substituted on the (C3-C10)cycloalkyl- group, by at least one substituent, in particular by one substituent, selected from -NH2 and a NH2-(C1- C6)alkyl- group such as a NH2-CH2- group; R2 represents : - a (C1-C6)alkyl- group, in particular a -(CH2)3-CH3 group; - a (C1-C6)alkylthio- group, in particular a -S-(CH2)2-CH3 group; or - a (C1-C6)alkyl-NH- group, in particular a -NH-(CH2)2-CH3group; and R3 represents : - a -OR6 group wherein R6 is a (C1-C6)alkyl- group, in particular a -O-isopropyl group (that is to say a -O-CH(CH3)2group); - a -NR7R8group wherein R7and R8form together with the nitrogen atom to which they are attached a (C3-C10)membered heterocycloalkyl- group comprising one to four heteroatoms selected from oxygen, nitrogen, and sulfur, in particular comprising two nitrogen atoms, for instance a piperazinyl group; or - a (C3-C10)membered heterocycloalkyl- group comprising one to four heteroatoms selected from oxygen, nitrogen and sulfur, in particular one nitrogen atom or two nitrogen atoms, for instance a dihydropyrrolyl group such as a 2,5-dihydro-1H-pyrrolyl group, or a piperazinyl group; *-(La)m-(AA)w-(Lb)p-Lc-Ld’-** represents: *-C(O)-O-CH2-para-phenyl-NH-Cit-Val-Glu-C(O)-(CH2)3-C(O)-NH-(CH2- CH2-O)3-(CH2)2-** ; *-C(O)-O-CH2-para-phenyl-NH-Ala-Val-Glu-C(O)-(CH2)3-C(O)-NH-(CH2- CH2-O)3-(CH2)2-**; *-Cit-Val-C(O)-(CH2-CH2-O)3-(CH2)2-NH-C(O)-(CH2)2-**; *-Cit-Val-C(O)-(CH2)3-C(O)-NH-(CH2-CH2-O)3-(CH2)2-**; *-Ala-Val-C(O)-(CH2)3-C(O)-NH-(CH2-CH2-O)3-(CH2)2-**; *-C(O)-O-CH2-para-phenyl-NH-Cit-Val-Glu-C(O)-(CH2)3-C(O)-NH-(CH2- CH2-O)3-(CH2)2-NH-C(O)-(CH2)2-** ; *-C(O)-O-CH2-para-phenyl-NH-Ala-Val-Glu--C(O)-(CH2)3-C(O)-NH-(CH2- CH2-O)3-(CH2)2-NH-C(O)-(CH2)2-**; *-Cit-Val-C(O)-(CH2)3-C(O)-NH-(CH2-CH2-O)3-(CH2)2-NH-C(O)-(CH2)2-**; or *-Ala-Val-C(O)-(CH2)3-C(O)-NH-(CH2-CH2-O)3-(CH2)2-NH-C(O)-(CH2)2-**, the single asterisk (*) indicating the site of covalent attachment to the A drug unit radical and the double asterisk (**) indicating the site of covalent attachment to the -RCG1 group; and RCG1 is N3-, or a maleimido group . Among the compounds of formula (I2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which A is of formula (A1) or of formula (A2): in which: R1, R2 and R3 are as defined in the present disclosure; the single asterisk (*) indicates the site of covalent attachment to –(P)o-L-Ld-RCG1; R1* represents: - either a single bond, which means that –(P)o-L-Ld-RCG1 is directly linked to the nitrogen atom of the imidazo[4,5-d]pyridazine ring, - or a divalent radical formed from R1as defined in the present disclosure, which means that –(P)o-L-Ld-RCG1 is linked to the nitrogen atom of the imidazo[4,5-d]pyridazine ring via R1; R3* represents: - either a single bond, which means that –(P)o-L-Ld-RCG1 is directly linked to the carbon atom of the imidazo[4,5-d]pyridazine ring, - or a divalent radical formed from R3as defined in the present disclosure, which means that –(P)o-L-Ld-RCG1 is linked to the carbon atom of the imidazo[4,5-d]pyridazine ring via R3. According to one particular embodiment, A is of formula (A1). According to another embodiment, A is of formula (A2). Thus, according to a particular embodiment, when R1* represents a single bond, the compounds of formula (I2) or a pharmaceutically acceptable salt thereof in accordance with the present disclosure have the following formula (Ia2): wherein R2, R3, P, o, L, Ld and RCG1 are as defined in the present disclosure. This means that in this particular embodiment, in the drug A, R1 is a hydrogen atom. According to another particular embodiment, when R1* represents a divalent radical formed from R1 as defined in the present disclosure, the compounds of formula (I2) or a pharmaceutically acceptable salt thereof in accordance with the present disclosure have the following formula (Iaa2): wherein R2, R3, P, o, L, Ld and RCG1 are as defined in the present disclosure and R1* is a divalent R1as defined in the present disclosure. This means that in this particular embodiment, in the drug A, R1 is not a hydrogen atom. According to another particular embodiment, when R3* represents a single bond, the compounds of formula (I2) or a pharmaceutically acceptable salt thereof in accordance with the present disclosure have the following formula (Ib2): wherein R1, R2, P, o, L, Ld and RCG1 are as defined in the present disclosure. This means that in this particular embodiment, in the drug A, R3 is a hydrogen atom. According to another particular embodiment, when R3* represents a divalent radical formed from R3 as defined in the present disclosure, the compounds of formula (I2) or a pharmaceutically acceptable salt thereof in accordance with the present disclosure have the following formula (Ibb2): wherein R1, R2, P, o, L, Ld and RCG1 are as defined in the present disclosure and R3* is a divalent R3as defined in the present disclosure. This means that in this particular embodiment, in the drug A, R3 is not a hydrogen atom. Among the compounds of formula (I2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which A is selected from the group consisting of: ;

[0016] . Among the compounds of formula (I2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which A is selected from the group consisting of:

[0017] . Among the compounds of formula (I2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which P is a -C(O)- group. Among the compounds of formula (I2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which P is a -C(O)-O- group. Among the compounds of formula (I2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which P is a -S(O2)- group. Among the compounds of formula (I2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which P is a -C(O)-C(CH3)2-CH2- O- group. Among the compounds of formula (I2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which P is a -C(O)-NH- group. Among the compounds of formula (I2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which P is a group. Among the compounds of formula (I2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which P is a group. Among the compounds of formula (I2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which o is 0. Among the compounds of formula (I2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which o is 1. Among the compounds of formula (I2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which L represents a *–(CH2- CH2-O)n-** group in which n represents an integer from 8 to 25, the single asterisk (*) indicating the site of covalent attachment to the P radical if present (that is to say if o is 1) or directly to the A radical if P is not present (that is to say if o is 0) and the double asterisk (**) indicating the site of covalent attachment to the Ld radical. Among the compounds of formula (I2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which L represents a *–(CH2- CH2-O)n-** group in which n represents 8, 12, 16, 20, 23 or 24, the single asterisk (*) indicating the site of covalent attachment to the P radical if present (that is to say if o is 1) or directly to the A radical if P is not present (that is to say if o is 0) and the double asterisk (**) indicating the site of covalent attachment to the Ld radical. Among the compounds of formula (I2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which Ld represents a *-(C2- C6)alkyl-** group, a *-(C2-C6)alkyl-NH-C(O)-(C2-C6)alkyl-** group or a *-(C2-C6)alkyl- C(O)-NH-(C2-C6)alkyl-** group, the single asterisk (*) indicating the site of covalent attachment to the L radical and the double asterisk (**) indicating the site of covalent attachment to the RCG1 radical. Among the compounds of formula (I2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which Ld represents a *–(CH2)2- ** group, a *-(CH2)2-NH-C(O)-(CH2)2-** group or a *-(CH2)2-C(O)-NH-(CH2)2-** group, the single asterisk (*) indicating the site of covalent attachment to the L radical and the double asterisk (**) indicating the site of covalent attachment to the RCG1 radical. Among the compounds of formula (I2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which RCG1 represents N3-, a -COOH group, or a maleimido group . Among the compounds of formula (I2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which when Ld represents a *-(C2-C6)alkyl-** group, the single asterisk (*) indicating the site of covalent attachment to the L radical and the double asterisk (**) indicating the site of covalent attachment to the RCG1 radical, then RCG1 represents N3-. Among the compounds of formula (I2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which when Ld represents a *-(C2-C6)alkyl-** group, the single asterisk (*) indicating the site of covalent attachment to the L radical and the double asterisk (**) indicating the site of covalent attachment to the RCG1 radical, then RCG1 represents -COOH. Among the compounds of formula (I2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which when Ld represents a *-(C2-C6)alkyl-NH-C(O)-(C2-C6)alkyl-** group, the single asterisk (*) indicating the site of covalent attachment to the L radical and the double asterisk (**) indicating the site of covalent attachment to the RCG1 radical, then RCG1 represents a maleimido . Among the compounds of formula (I2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which when Ld represents a *-(CH2)2-** group, the single asterisk (*) indicating the site of covalent attachment to the L radical and the double asterisk (**) indicating the site of covalent attachment to the RCG1 radical, then RCG1 represents N3-. Among the compounds of formula (I2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which when Ld represents a *-(CH2)2-** group, the single asterisk (*) indicating the site of covalent attachment to the L radical and the double asterisk (**) indicating the site of covalent attachment to the RCG1 radical, then RCG1 represents -COOH. Among the compounds of formula (I2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which when Ld represents a *-(CH2)2-NH-C(O)-(CH2)2-** group, the single asterisk (*) indicating the site of covalent attachment to the L radical and the double asterisk (**) indicating the site of covalent attachment to the RCG1 radical, then RCG1 represents a maleimido group . All these sub-groups taken alone or in combination are part of the present disclosure. According to a particular embodiment, the disclosure relates to a compound / payload of formula (I2) or a pharmaceutically acceptable salt thereof wherein the -(P)o-L-Ld- part is selected from the group consisting of: *-C(O)-(CH2-CH2-O)24-CH2-CH2-**; *-(CH2-CH2-O)23-CH2-CH2-**; *-C(O)-(CH2-CH2-O)20-CH2-CH2-**; *-C(O)-(CH2-CH2-O)16-CH2-CH2-**; *-C(O)-(CH2-CH2-O)12-CH2-CH2-**; *-C(O)-(CH2-CH2-O)8-CH2-CH2-**; *-C(O)-C(CH3)2-CH2-O-(CH2-CH2-O)20-CH2-CH2-**; *-C(O)-O-(CH2-CH2-O)20-CH2-CH2-**; *-C(O)-(CH2-CH2-O)24-CH2-CH2-NH-C(O)-CH2-CH2-**; *-C(O)-(CH2-CH2-O)20-CH2-CH2-NH-C(O)-CH2-CH2-**; and *-C(O)-(CH2-CH2-O)12-CH2-CH2-NH-C(O)-CH2-CH2-**; the single asterisk (*) indicating the site of covalent attachment to the A drug unit radical and the double asterisk (**) indicating the site of covalent attachment to the RCG1 radical. Among the compounds of formula (I2) that are subject-matter of the present disclosure, a group of compounds is composed of the compounds wherein: A is of formula (A) in which: R1 represents: - a (C1-C6)alkyl- group, in particular a methyl group; - a NH2-(C1-C6)alkyl- group, in particular a NH2-(CH2)5- group; - a phenyl(C1-C6)alkyl- group, in particular a phenyl-CH2- group, being unsubstituted or substituted by at least one substituent, in particular substituted on the phenyl ring by at least one substituent, for instance by one substituent, selected from: - a (C1-C6)alkyl- group, in particular a methyl group (or a -CH2- group if substituted) or an isopropyl group (or a -CH(CH3)2- group if substituted), being unsubstituted or substituted by at least one substituent, in particular by one substituent, selected from: - a -NR4R5group wherein R4and R5, being independently from each other selected from: a hydrogen atom and a (C1-C16)alkyl- group, in particular a methyl group, for instance -NR4R5 is -NH2 or -NH(CH3); or R4 and R5 form together with the nitrogen atom to which they are attached an unsubstituted (C3-C10)membered heterocycloalkyl- group comprising one to four heteroatoms selected from oxygen, nitrogen and sulfur, in particular an unsubstituted (C3-C10)membered heterocycloalkyl- group comprising two nitrogen atoms, for instance a piperazinyl group; or - a (C3-C10)cycloalkyl(C1-C6)alkyl- group, in particular a cyclohexyl-CH2- group, being unsubstituted or substituted, in particular substituted on the (C3-C10)cycloalkyl- group, by at least one substituent, in particular by one substituent, selected from -NH2and a NH2-(C1- C6)alkyl- group such as a NH2-CH2- group; R2 represents : - a (C1-C6)alkyl- group, in particular a -(CH2)3-CH3 group; - a (C1-C6)alkylthio- group, in particular a -S-(CH2)2-CH3group; or - a (C1-C6)alkyl-NH- group, in particular a -NH-(CH2)2-CH3group; and R3 represents : - a -OR6 group wherein R6 is a (C1-C6)alkyl- group, in particular a -O-isopropyl group (that is to say a -O-CH(CH3)2group); - a -NR7R8 group wherein R7 and R8 form together with the nitrogen atom to which they are attached a (C3-C10)membered heterocycloalkyl- group comprising one to four heteroatoms selected from oxygen, nitrogen, and sulfur, in particular comprising two nitrogen atoms, for instance a piperazinyl group; or - a (C3-C10)membered heterocycloalkyl- group comprising one to four heteroatoms selected from oxygen, nitrogen and sulfur, in particular one nitrogen atom or two nitrogen atoms, for instance a dihydropyrrolyl group such as a 2,5-dihydro-1H-pyrrolyl group, or a piperazinyl group; *-(P)o-L-Ld-** represents: *-C(O)-(CH2-CH2-O)24-CH2-CH2-**; *-(CH2-CH2-O)23-CH2-CH2-**; *-C(O)-(CH2-CH2-O)20-CH2-CH2-**; *-C(O)-(CH2-CH2-O)16-CH2-CH2-**; *-C(O)-(CH2-CH2-O)12-CH2-CH2-**; *-C(O)-(CH2-CH2-O)8-CH2-CH2-**; *-C(O)-C(CH3)2-CH2-O-(CH2-CH2-O)20-CH2-CH2-**; *-C(O)-O-(CH2-CH2-O)20-CH2-CH2-**; *-C(O)-(CH2-CH2-O)24-CH2-CH2-NH-C(O)-CH2-CH2-**; *-C(O)-(CH2-CH2-O)20-CH2-CH2-NH-C(O)-CH2-CH2-**; or *-C(O)-(CH2-CH2-O)12-CH2-CH2-NH-C(O)-CH2-CH2-**; the single asterisk (*) indicating the site of covalent attachment to the A drug unit radical and the double asterisk (**) indicating the site of covalent attachment to the -RCG1 group; and RCG1 is N3-, a -COOH group or a maleimido group . Among the compounds / payloads of formulae (I), (I1) or (I2) or a pharmaceutically acceptable salt thereof that are subject matter of the present disclosure, mention may be made for instance to the following compounds: ; ; ;

[0018]

[0019]

[0020] . Among the compounds / payloads of formulae (I), (I1) or (I2) or a pharmaceutically acceptable salt thereof that are subject matter of the present disclosure, mention may be made for instance to the following compounds: (P1) (4S)-5-[[(2S)-1-[[(2S)-1-[4-[[4-[[4-[(7-amino-2-butyl-4-propan-2- yloxyimidazo[4,5-d]pyridazin-3-yl)methyl]phenyl]methyl]piperazine-1-carbonyl] oxymethyl]anilino]-5-(carbamoylamino)-1-oxopentan-2-yl]amino]-3-methyl-1-oxobutan- 2-yl]amino]-4-[[5-[2-[2-[2-(2-azidoethoxy)ethoxy]ethoxy]ethylamino]-5-oxopentanoyl] amino]-5-oxopentanoic acid ; (P2) (4S)-5-[[(2S)-1-[[(2S)-1-[4-[[trans-4-[(7-amino-2-butyl-4-propan-2- yloxyimidazo[4,5-d]pyridazin-3-yl)methyl]cyclohexyl]methylcarbamoyloxymethyl] anilino]-5-(carbamoylamino)-1-oxopentan-2-yl]amino]-3-methyl-1-oxobutan-2-yl]amino]- 4-[[5-[2-[2-[2-(2-azidoethoxy)ethoxy]ethoxy]ethylamino]-5-oxopentanoyl]amino]-5- oxopentanoic acid ; (P3) (4S)-5-[[(2S)-1-[[(2S)-1-[4-[[4-[[4-[(7-amino-2-butyl-4-propan-2- yloxyimidazo[4,5-d]pyridazin-3-yl)methyl]phenyl]methyl]piperazine-1-carbonyl] oxymethyl]anilino]-1-oxopropan-2-yl]amino]-3-methyl-1-oxobutan-2-yl]amino]-4-[[5-[2- [2-[2-(2-azidoethoxy)ethoxy]ethoxy]ethylamino]-5-oxopentanoyl]amino]-5-oxopentanoic acid ; (P4) (4S)-5-[[(2S)-1-[[(2S)-1-[4-[[trans-4-[(7-amino-2-butyl-4-propan-2- yloxyimidazo[4,5-d]pyridazin-3-yl)methyl]cyclohexyl]methylcarbamoyloxymethyl] anilino]-1-oxopropan-2-yl]amino]-3-methyl-1-oxobutan-2-yl]amino]-4-[[5-[2-[2-[2-(2- azidoethoxy)ethoxy]ethoxy]ethylamino]-5-oxopentanoyl]amino]-5-oxopentanoic acid; (P5) N'-[(2S)-1-[[(2S)-1-[4-[[4-[(7-amino-2-butyl-4-propan-2-yloxyimidazo [4,5-d]pyridazin-3-yl)methyl]phenyl]methyl]piperazin-1-yl]-1-oxopropan-2-yl]amino]-3- methyl-1-oxobutan-2-yl]-N-[2-[2-[2-(2-azidoethoxy)ethoxy]ethoxy]ethyl]pentanediamide; (P6) N'-[(2S)-1-[[(2S)-1-[[trans-4-[(7-amino-2-butyl-4-propan-2-yloxyimidazo [4,5-d]pyridazin-3-yl)methyl]cyclohexyl]methylamino]-1-oxopropan-2-yl]amino]-3- methyl-1-oxobutan-2-yl]-N-[2-[2-[2-(2-azidoethoxy)ethoxy]ethoxy]ethyl]pentanediamide; (P7) N'-[(2S)-1-[[(2S)-1-[[trans-4-[(7-amino-2-butyl-4-propan-2-yloxyimidazo [4,5-d]pyridazin-3-yl)methyl]cyclohexyl]methylamino]-1-oxopropan-2-yl]amino]-3- methyl-1-oxobutan-2-yl]-N-[2-[2-[2-[2-[3-(2,5-dioxopyrrol-1-yl)propanoylamino]ethoxy] ethoxy]ethoxy]ethyl]pentanediamide; (P8) N'-[(2S)-1-[[(2S)-1-[4-[[4-[(7-amino-2-butyl-4-propan-2-yloxyimidazo [4,5-d]pyridazin-3-yl)methyl]phenyl]methyl]piperazin-1-yl]-5-(carbamoylamino)-1- oxopentan-2-yl]amino]-3-methyl-1-oxobutan-2-yl]-N-[2-[2-[2-(2-azidoethoxy)ethoxy] ethoxy]ethyl]pentanediamide; (P9) N'-[(2S)-1-[[(2S)-1-[[trans-4-[(7-amino-2-butyl-4-propan-2-yloxyimidazo [4,5-d]pyridazin-3-yl)methyl]cyclohexyl]methylamino]-5-(carbamoylamino)-1-oxopentan- 2-yl]amino]-3-methyl-1-oxobutan-2-yl]-N-[2-[2-[2-(2-azidoethoxy)ethoxy]ethoxy] ethyl]pentanediamide; (P10) N'-[(2S)-1-[[(2S)-1-[[trans-4-[(7-amino-2-butyl-4-propan-2- yloxyimidazo[4,5-d]pyridazin-3-yl)methyl]cyclohexyl]methylamino]-5- (carbamoylamino)-1-oxopentan-2-yl]amino]-3-methyl-1-oxobutan-2-yl]-N-[2-[2-[2-[2-[3- (2,5-dioxopyrrol-1-yl)propanoylamino]ethoxy]ethoxy]ethoxy]ethyl]pentanediamide,2,2,2- trifluoroacetic acid; (P11) 1-[4-[[4-[(7-amino-2-butyl-4-propan-2-yloxyimidazo[4,5-d]pyridazin-3- yl)methyl]phenyl]methyl]piperazin-1-yl]-3-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2- [2-[2-[2-[2-[2-[2-[2-(2-azidoethoxy)ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy ]ethoxy]ethoxy]ethoxy]ethoxy]propan-1-one; (P12) N-[[trans-4-[(7-amino-2-butyl-4-propan-2-yloxyimidazo[4,5-d] pyridazin-3-yl)methyl]cyclohexyl]methyl]-3-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2- [2-[2-[2-[2-[2-[2-[2-[2-(2-azidoethoxy)ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy ]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]propenamide; (P13) N-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2- [3-[4-[[4-[(7-amino-2-butyl-4-propan-2-yloxyimidazo[4,5-d]pyridazin-3-yl)methyl] phenyl]methyl]piperazin-1-yl]-3-oxopropoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy ]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethyl]-3-(2,5-dioxopyrrol-1-yl) propanamide, 2,2,2-trifluoroacetic acid; (P14) N-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[3-[[trans-4-[(7-amino-2-butyl-4- propan-2-yloxyimidazo[4,5-d]pyridazin-3-yl)methyl]cyclohexyl]methylamino]-3- oxopropoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]et hoxy]ethyl]-3-(2,5-dioxopyrrol-1-yl)propanamide, 2,2,2-trifluoroacetic acid; (P15) N-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[3-[[trans-4- [(7-amino-2-butyl-4-propan-2-yloxyimidazo[4,5-d]pyridazin-3-yl)methyl]cyclohexyl] methylamino]-3-oxopropoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethyl]- 3-(2,5-dioxopyrrol-1-yl)propanamide, 2,2,2-trifluoroacetic acid; (P16) N-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2- [3-[[trans-4-[(7-amino-2-butyl-4-propan-2-yloxyimidazo[4,5-d]pyridazin-3-yl)methyl] cyclohexyl]methylamino]-3-oxopropoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy ]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethyl]-3-(2,5-dioxopyrrol-1-yl)propanamide, 2,2,2- trifluoroacetic acid; (P17) 3-[[4-[[4-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2- [2-[2-(2-azidoethoxy)ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy ]ethoxy]ethyl]piperazin-1-yl]methyl]phenyl]methyl]-2-butyl-4-propan-2-yloxyimidazo [4,5-d]pyridazin-7-amine; (P18) 3-[[trans-4-[[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2- [2-[2-[2-(2-azidoethoxy)ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy ]ethoxy]ethoxy]ethylamino]methyl]cyclohexyl]methyl]-2-butyl-4-propan-2-yloxyimidazo [4,5-d]pyridazin-7-amine; (P19) N-[[trans-4-[(7-amino-2-butyl-4-isopropoxy-imidazo[4,5-d]pyridazin-3- yl)methyl]cyclohexyl]methyl]-3-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-(2- azidoethoxy)ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]et hoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]propenamide; (P20) N-[[trans-4-[(7-amino-2-butyl-4-isopropoxy-imidazo[4,5-d]pyridazin-3- yl)methyl]cyclohexyl]methyl]-3-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-(2- azidoethoxy)ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]et hoxy]ethoxy]ethoxy]ethoxy]ethoxy]propenamide; (P21) N-[[trans-4-[(7-amino-2-butyl-4-isopropoxy-imidazo[4,5-d]pyridazin-3- yl)methyl]cyclohexyl]methyl]-3-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-(2- azidoethoxy)ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]et hoxy]propenamide; (P22) 3-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[3-[[trans-4-[(7-amino-2-butyl-4- isopropoxy-imidazo[4,5-d]pyridazin-3-yl)methyl]cyclohexyl]methylamino]-3-oxo- propoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethox y]propanoic acid; (P23) N-[[trans-4-[(7-amino-2-butyl-4-isopropoxy-imidazo[4,5-d]pyridazin-3- yl)methyl]cyclohexyl]methyl]-3-[2-[2-[2-[2-[2-[2-[2-(2-azidoethoxy)ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]propenamide; (P24) ((4S)-5-[[(2S)-1-[[(2S)-1-[4-[[4-[(7-amino-2-butyl-4-propan-2- yloxyimidazo[4,5-d]pyridazin-3-yl)methyl]phenyl]methylcarbamoyloxymethyl]anilino]-5- (carbamoylamino)-1-oxopentan-2-yl]amino]-3-methyl-1-oxobutan-2-yl]amino]-4-[[5-[2- [2-[2-(2-azidoethoxy)ethoxy]ethoxy]ethylamino]-5-oxopentanoyl]amino]-5-oxopentanoic acid; (P25) (4S)-5-[[(2S)-1-[[(2S)-1-[4-[[4-[(7-amino-2-butyl-4-propan-2- yloxyimidazo[4,5-d]pyridazin-3-yl)methyl]cyclohexyl]carbamoyloxymethyl]anilino]-5- (carbamoylamino)-1-oxopentan-2-yl]amino]-3-methyl-1-oxobutan-2-yl]amino]-4-[[5-[2- [2-[2-(2-azidoethoxy)ethoxy]ethoxy]ethylamino]-5-oxopentanoyl]amino]-5-oxopentanoic acid; (P26) (4S)-5-[[(2S)-1-[[(2S)-1-[4-[[4-[(7-amino-2-butyl-4-propan-2- yloxyimidazo[4,5-d]pyridazin-3-yl)methyl]phenyl]methylcarbamoyloxymethyl]anilino]-1- oxopropan-2-yl]amino]-3-methyl-1-oxobutan-2-yl]amino]-4-[[5-[2-[2-[2-(2-azidoethoxy) ethoxy]ethoxy]ethylamino]-5-oxopentanoyl]amino]-5-oxopentanoic acid; (P27) (4S)-5-[[(2S)-1-[[(2S)-1-[4-[[4-[(7-amino-2-butyl-4-propan-2- yloxyimidazo[4,5-d]pyridazin-3-yl)methyl]cyclohexyl]carbamoyloxymethyl]anilino]-1- oxopropan-2-yl]amino]-3-methyl-1-oxobutan-2-yl]amino]-4-[[5-[2-[2-[2-(2-azidoethoxy) ethoxy]ethoxy]ethylamino]-5-oxopentanoyl]amino]-5-oxopentanoic acid; (P28) N'-[(2S)-1-[[(2S)-1-[[4-[(7-amino-2-butyl-4-propan-2-yloxyimidazo[4,5- d]pyridazin-3-yl)methyl]phenyl]methylamino]-1-oxopropan-2-yl]amino]-3-methyl-1- oxobutan-2-yl]-N-[2-[2-[2-(2-azidoethoxy)ethoxy]ethoxy]ethyl]pentanediamide; (P29) N'-[(2S)-1-[[(2S)-1-[[4-[(7-amino-2-butyl-4-propan-2-yloxyimidazo[4,5- d]pyridazin-3-yl)methyl]cyclohexyl]amino]-1-oxopropan-2-yl]amino]-3-methyl-1- oxobutan-2-yl]-N-[2-[2-[2-(2-azidoethoxy)ethoxy]ethoxy]ethyl]pentanediamide; (P30) N'-[(2S)-1-[[(2S)-1-[[4-[(7-amino-2-butyl-4-propan-2-yloxyimidazo[4,5- d]pyridazin-3-yl)methyl]phenyl]methylamino]-1-oxopropan-2-yl]amino]-3-methyl-1- oxobutan-2-yl]-N-[2-[2-[2-[2-[3-(2,5-dioxopyrrol-1-yl)propanoylamino]ethoxy]ethoxy] ethoxy]ethyl]pentanediamide; (P31) N'-[(2S)-1-[[(2S)-1-[[4-[(7-amino-2-butyl-4-propan-2-yloxyimidazo[4,5- d]pyridazin-3-yl)methyl]phenyl]methylamino]-5-(carbamoylamino)-1-oxopentan-2- yl]amino]-3-methyl-1-oxobutan-2-yl]-N-[2-[2-[2-(2-azidoethoxy)ethoxy]ethoxy]ethyl] pentanediamide; (P32) N'-[(2S)-1-[[(2S)-1-[[4-[(7-amino-2-butyl-4-propan-2-yloxyimidazo[4,5- d]pyridazin-3-yl)methyl]cyclohexyl]amino]-5-(carbamoylamino)-1-oxopentan-2- yl]amino]-3-methyl-1-oxobutan-2-yl]-N-[2-[2-[2-(2-azidoethoxy)ethoxy]ethoxy]ethyl] pentanediamide; 2,2,2-trifluoroacetate; (P33) N'-[(2S)-1-[[(2S)-1-[[4-[(7-amino-2-butyl-4-propan-2-yloxyimidazo[4,5- d]pyridazin-3-yl)methyl]phenyl]methylamino]-5-(carbamoylamino)-1-oxopentan-2- yl]amino]-3-methyl-1-oxobutan-2-yl]-N-[2-[2-[2-[2-[3-(2,5-dioxopyrrol-1-yl)propanoyl amino]ethoxy]ethoxy]ethoxy]ethyl]pentanediamide; 2,2,2-trifluoroacetate; (P34) N'-[(1S)-1-[[(1S)-1-[[4-[(7-amino-2-butyl-4-isopropoxy-imidazo[4,5- d]pyridazin-3-yl)methyl]cyclohexyl]carbamoyl]-4-ureido-butyl]carbamoyl]-2-methyl- propyl]-N-[2-[2-[2-[2-[3-(2,5-dioxopyrrol-1-yl)propanoylamino]ethoxy]ethoxy]ethoxy] ethyl]pentanediamide; 2,2,2-trifluoroacetic acid; (P35) (2S)-N-[[4-[(7-amino-2-butyl-4-isopropoxy-imidazo[4,5-d]pyridazin-3- yl)methyl]phenyl]methyl]-2-[[(2S)-2-[3-[2-[2-[2-[3-(2,5-dioxopyrrol-1-yl)propanoyl amino]ethoxy]ethoxy]ethoxy]propanoylamino]-3-methyl-butanoyl]amino]-5-ureido- pentanamide; 2,2,2-trifluoroacetic acid; (P36) (2S)-N-[[4-[[7-amino-4-isopropoxy-2-(propylamino)imidazo[4,5-d] pyridazin -3-yl]methyl]phenyl]methyl]-2-[[(2S)-2-[3-[2-[2-[2-[3-(2,5-dioxopyrrol-1- yl)propanoylamino]ethoxy]ethoxy]ethoxy]propanoylamino]-3-methyl-butanoyl]amino]-5- ureido-pentanamide; 2,2,2-trifluoroacetic acid; (P37) N'-[(1S)-1-[[(1S)-1-[3-(4-amino-2-butyl-1-methyl-imidazo[4,5-d] pyridazin-7-yl)-2,5-dihydropyrrole-1-carbonyl]-4-ureido-butyl]carbamoyl]-2-methyl- propyl]-N-[2-[2-[2-[2-[3-(2,5-dioxopyrrol-1-yl)propanoylamino]ethoxy]ethoxy]ethoxy] ethyl]pentanediamide; 2,2,2-trifluoroacetic acid; (P38) N'-[(1S)-1-[[(1S)-1-[4-(7-amino-2-butyl-3-methyl-imidazo[4,5-d] pyridazin-4-yl)piperazine-1-carbonyl]-4-ureido-butyl]carbamoyl]-2-methyl-propyl]-N-[2- [2-[2-[2-[3-(2,5-dioxopyrrol-1-yl)propanoylamino]ethoxy]ethoxy]ethoxy]ethyl] pentanediamide; 2,2,2-trifluoroacetic acid; (P39) (2S)-N-[5-(7-amino-2-butyl-4-isopropoxy-imidazo[4,5-d]pyridazin-3-yl) pentyl]-2-[[(2S)-2-[3-[2-[2-[2-[3-(2,5-dioxopyrrol-1-yl)propanoylamino]ethoxy]ethoxy] ethoxy]propanoylamino]-3-methyl-butanoyl]amino]-5-ureido-pentanamide, 2,2,2-trifluoro acetic acid; (P40) (2S)-N-[4-[(7-amino-2-butyl-4-isopropoxy-imidazo[4,5-d]pyridazin-3- yl)methyl]cyclohexyl]-2-[[(2S)-2-[3-[2-[2-[2-[3-(2,5-dioxopyrrol-1-yl)propanoylamino] ethoxy]ethoxy]ethoxy]propanoylamino]-3-methyl-butanoyl]amino]-5-ureido-pentanamide, 2,2,2-trifluoroacetic acid; (P41) N-[[4-[(7-amino-2-butyl-4-propan-2-yloxyimidazo[4,5-d]pyridazin-3- yl)methyl]phenyl]methyl]-3-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2- [2-[2-(2 azidoethoxy)ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy ]ethoxy]ethoxy]propanamide; (P42) N-[4-[(7-amino-2-butyl-4-propan-2-yloxyimidazo[4,5-d]pyridazin-3- yl)methyl]cyclohexyl]-3-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2- [2-(2-azidoethoxy)ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy ]ethoxy]ethoxy]propanamide; (P43) N-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[3-[[4-[(7- amino-2-butyl-4-propan-2-yloxyimidazo[4,5-d]pyridazin-3-yl)methyl]phenyl]methyl amino]-3-oxopropoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethyl]- 3-(2,5-dioxopyrrol-1-yl)propenamide; 2,2,2-trifluoroacetate; (P44) N-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[3-[[4-[(7- amino-4-isopropoxy-2-propylsulfanyl-imidazo[4,5-d]pyridazin-3-yl)methyl]phenyl] methylamino]-3-oxo-propoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy ]ethyl]-3-(2,5-dioxopyrrol-1-yl)propanamide; (P45) N-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2- [3-[[4-[(7-amino-2-butyl-4-propan-2-yloxyimidazo[4,5-d]pyridazin-3-yl)methyl]phenyl] methylamino]-3-oxopropoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy ]ethoxy]ethoxy]ethoxy]ethyl]-3-(2,5-dioxopyrrol-1-yl)propenamide,2,2,2-trifluoroacetic acid; (P46) 3-[[4-[[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2- [2-(2-azidoethoxy)ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy ]ethoxy]ethylamino]methyl]phenyl]methyl]-2-butyl-4-propan-2-yloxyimidazo[4,5-d] pyridazin-7-amine; (P47) N-[[4-[(7-amino-2-butyl-4-isopropoxy-imidazo[4,5-d]pyridazin-3- yl)methyl]phenyl]methyl]-3-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-(2- azidoethoxy)ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]propanamide; (P48) N-[[4-[(7-amino-2-butyl-4-isopropoxy-imidazo[4,5-d]pyridazin-3- yl)methyl]phenyl]methyl]-3-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-(2-azidoethoxy) ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy ]ethoxy]ethoxy]ethoxy]propanamide; (P49) N-[[4-[(7-amino-2-butyl-4-isopropoxy-imidazo[4,5-d]pyridazin-3- yl)methyl]phenyl]methyl]-3-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-(2-azidoethoxy)ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]propanamide; (P50) 3-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[3-[[4-[(7-amino-2-butyl-4- isopropoxy-imidazo[4,5-d]pyridazin-3-yl)methyl]phenyl]methylamino]-3-oxo-propoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy] propanoic acid; (P51) N-[[4-[(7-amino-2-butyl-4-isopropoxy-imidazo[4,5-d]pyridazin-3- yl)methyl]phenyl]methyl]-3-[2-[2-[2-[2-[2-[2-[2-(2-azidoethoxy)ethoxy]ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]propanamide; (P52) N-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[3-[[4-[(7-amino-2-butyl-4- isopropoxy-imidazo[4,5-d]pyridazin-3-yl)methyl]phenyl]methylamino]-3-oxo- propoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethox y]ethyl]-3-(2,5-dioxopyrrol-1-yl)propanamide; (P53) N-[1-[4-[(7-amino-2-butyl-4-isopropoxy-imidazo[4,5-d]pyridazin-3- yl)methyl]phenyl]-1-methyl-ethyl]-3-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2- [2-(2-azidoethoxy)ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]propanamide; (P54) N-[[4-[(7-amino-2-butyl-4-isopropoxy-imidazo[4,5-d]pyridazin-3- yl)methyl]phenyl]methyl]-3-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-(2- azidoethoxy)ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]-N-methyl- propanamide; (P55) N-[[4-[(7-amino-2-butyl-4-isopropoxy-imidazo[4,5-d]pyridazin-3- yl)methyl]phenyl]methyl]-3-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-(2- azidoethoxy)ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]-2,2-dimethyl- propanamide; (P56) N-[[4-[(7-amino-2-butyl-4-isopropoxy-imidazo[4,5-d]pyridazin-3- yl)methyl]phenyl]methyl]-1-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-(2- azidoethoxy)ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxymethyl]cyclopentaneca rboxamide; (P57) N-[[4-[(7-amino-2-butyl-4-isopropoxy-imidazo[4,5-d]pyridazin-3- yl)methyl]phenyl]methyl]-1-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-(2- azidoethoxy)ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxymethyl]cyclohexanecar boxamide; (P58) 2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-(2- azidoethoxy)ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethyl N-[[4-[(7-amino-2- butyl-4-isopropoxy-imidazo[4,5-d]pyridazin-3-yl)methyl]phenyl]methyl]carbamate; (P59) 1-[[4-[(7-amino-2-butyl-4-isopropoxy-imidazo[4,5-d]pyridazin-3- yl)methyl]phenyl]methyl]-3-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-(2- azidoethoxy)ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethyl]urea; or a pharmaceutically acceptable salt thereof. The compounds / payloads of formulae (I), (I1) or (I2) or a pharmaceutically acceptable salt thereof according to the present disclosure can be prepared according to any process known by the skilled person, and for instance by the following processes. Synthesis of the compounds / payloads of formulae (I) and (I1): - Synthesis of linkers a) Synthetic scheme of linker types 1 and 2

[0021] Linker 1 and 2 Scheme 1 In scheme 1, PG represents a carboxylic acid protecting group as defined in the present disclosure; n is as defined in the present disclosure; and R11 and R12 represent, independently of each other, the side chain of AA as defined in the present disclosure. b) Synthetic scheme of linker types 3 and 4 Linker 3 and 4 Scheme 2 In scheme 2, R11 and R12 represent, independently of each other, the side chain of AA as defined in the present disclosure; and n is as defined in the present disclosure. c) Synthetic scheme of linker types 5, 6 and 7 Linker 5, 6 and 7 Scheme 2a In scheme 2a, R13 and R14 represent, independently of each other, a -(C1-C6)alkyl group or alternatively R13 and R14 form together with the carbon atom to which they are attached a -(C3-C6)cycloalkyl group or a -(C3-C6)heterocycloalkyl group as defined in the present disclosure; and n is as defined in the present disclosure. d) Synthetic scheme of linker type 8 Linker 8 Scheme 2b In scheme 2b, n is as defined in the present disclosure. e) Synthetic scheme of linker type 9 Scheme 2c In scheme 2c, R11 and R12 represent, independently of each other, the side chain of AA as defined in the present disclosure; and n is as defined in the present disclosure. - Synthesis of Payloads Synthesis of the compounds / payloads of formulas (I) and (I1) a) Synthetic scheme of payloads with CL (cleavable) linker types 1 and 2

[0022] Scheme 3 In scheme 3, -R1*-NH2corresponds to -R1 as defined in the present disclosure provided that R1 comprises a NH2 group; R2 and R3 are as defined in the present disclosure; n is as defined in the present disclosure; R11 and R12 represent, independently of each other, the side chain of AA as defined in the present disclosure; and PG represents a carboxylic acid protecting group as defined in the present disclosure. b) Synthetic scheme of payloads with CL linker types 3 and 4

[0023] Scheme 4 In scheme 4, -R1*-NH2 corresponds to -R1 as defined in the present disclosure provided that R1 comprises a NH2 group; n is as defined in the present disclosure; R2 and R3 are as defined in the present disclosure; and R11 and R12 represent, independently of each other, the side chain of AA as defined in the present disclosure. c) Synthetic scheme of payloads with CL linker type 9 Scheme 4a In scheme 4a, -R1*-NH2 corresponds to -R1 as defined in the present disclosure provided that R1 comprises a NH2 group; n is as defined in the present disclosure; R2 and R3 are as defined in the present disclosure; and R11 and R12 represent, independently of each other, the side chain of AA as defined in the present disclosure. Scheme 4b In scheme 4b, -R3*-NH-R4 corresponds to -R3 as defined in the present disclosure provided that R3 comprises a -NH-R4 group, R4 being as defined in the present disclosure; n is as defined in the present disclosure; R1 and R2 are as defined in the present disclosure; and R11 and R12 represent, independently of each other, the side chain of AA as defined in the present disclosure. Synthesis of the compounds / payloads of formulas (I) and (I2): a) Synthetic scheme of payloads with NCL (non - cleavable) amide linkers Scheme 1’ In scheme 1’, -R1*-NH-R4 corresponds to -R1 as defined in the present disclosure, provided that -R1 comprises a -NH-R4 group, R4 being as defined in the present disclosure; n is as defined in the present disclosure; and R2 and R3 are as defined in the present disclosure. Scheme 1’a In scheme 1’a, -R1*-NH-R4 corresponds to -R1 as defined in the present disclosure, provided that -R1 comprises a -NH-R4 group, R4 being as defined in the present disclosure; n is as defined in the present disclosure; and R2 and R3 are as defined in the present disclosure. b) Synthetic scheme of payloads with NCL (non - cleavable) alkyl linkers Scheme 2’ In scheme 2’, -R1*-NH- corresponds to -R1 provided that R1 as defined in the present disclosure comprises a NH2 group; n is as defined in the present disclosure; R2 and R3 are as defined in the present disclosure; LG represents a leaving group as defined in the present disclosure; and PG represents an amino protecting group as defined in the present disclosure. Scheme 2’’ In scheme 2’’, -R1*-NH- corresponds to -R1 as defined in the present disclosure provided that R1 comprises a NH2group; n is as defined in the present disclosure; R2 and R3 are as defined in the present disclosure; and LG represents a leaving group as defined in the present disclosure. c) Synthetic scheme of payloads with NCL (non - cleavable) carbamate linkers Scheme 2’’a In scheme 2’’a, -R1*-NH2corresponds to -R1 as defined in the present disclosure, provided that -R1 comprises a -NH2 group; n is as defined in the present disclosure; and R2 and R3 are as defined in the present disclosure. d) Synthetic scheme of payloads with NCL (non-cleavable) urea linkers type 8 Scheme 2’’b In scheme 2’’b, -R1*-NH2 corresponds to -R1 as defined in the present disclosure, provided that -R1 comprises a -NH2group; n is as defined in the present disclosure; and R2 and R3 are as defined in the present disclosure. The specific compounds / payloads of formulae (I), (I1) and (I2) as defined in the present disclosure are indicated in Table 1 and Table 1’ (number, and formula) and are further detailed hereafter. In Table 2 and Table 2’, NMR, and liquid chromatography / mass spectra are also indicated. The NMR of Table 2 and Table 2’ is NMR Spectra (400 MHz, δ in ppm, DMSO-d6 or CDCl3) as defined in the Experimental part. The liquid chromatography / mass spectra (LC / MS) of Table 2 and Table 2’ were obtained according to one of the four methods described in the Experimental part. Table 1:

[0024] Table 1’ :

[0025] Table 2 :

[0026] Table 2’ :

[0027] The present disclosure further relates to a compound / conjugate of formula (II) or a pharmaceutically acceptable salt thereof: A-L1-G-BA (II) wherein: A, and L1 are as defined in the present disclosure; BA represents a binding agent for instance a protein, a polypeptide, a ligand, a peptide, an oligonucleotide or an oligosaccharide, for instance BA is a targeting agent for instance a cell-binding agent such as an antibody, such as a monoclonal antibody or a VHH antibody; G represents the product of reaction between RCG1 as defined in the present disclosure and RCG2, a reactive group present on the binding agent, for instance G is selected from the group consisting of : ; for instance, the left side of the G groups being linked to BA, for instance an antibody (Ab), and the right side of the G groups being linked to L1, for instance G represents the following groups:

[0028] According to a particular embodiment, L1 represents a cleavable linker or a non - cleavable linker. According to one particular embodiment, L1 is a cleavable linker which is a peptidic linker. According to another particular embodiment, L1 is a non-cleavable linker which is a PEGylated linker. Among the compounds of formula (II) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which A is of formula (A1) or of formula (A2) in which: R1, R2 and R3 are as defined in the present disclosure; the single asterisk (*) indicates the site of covalent attachment to -L1-G-BA; R1* represents: - either a single bond, which means that -L1-G-BA is directly linked to the nitrogen atom of the imidazo[4,5-d]pyridazine ring, - or a divalent radical formed from R1as defined in the present disclosure, which means that -L1-G-BA is linked to the nitrogen atom of the imidazo[4,5-d]pyridazine ring via R1; R3* represents: - either a single bond, which means that -L1-G-BA is directly linked to the carbon atom of the imidazo[4,5-d]pyridazine ring, - or a divalent radical formed from R3as defined in the present disclosure, which means that -L1-G-BA is linked to the carbon atom of the imidazo[4,5-d]pyridazine ring via R3. According to one particular embodiment, A is of formula (A1). According to another embodiment, A is of formula (A2). Thus, according to a particular embodiment, when R1* represents a single bond, the compounds of formula (II) or a pharmaceutically acceptable salt thereof in accordance with the present disclosure have the following formula (IIa): wherein R2, R3, L1, G and BA are as defined in the present disclosure. This means that in this particular embodiment, in the drug A, R1 is a hydrogen atom. According to another particular embodiment, when R1* represents a divalent radical formed from R1 as defined in the present disclosure, the compounds of formula (II) or a pharmaceutically acceptable salt thereof in accordance with the present disclosure have the following formula (IIaa): wherein R2, R3, L1, G and BA are as defined in the present disclosure and R1* is a divalent R1 as defined in the present disclosure. This means that in this particular embodiment, in the drug A, R1 is not a hydrogen atom. According to another particular embodiment, when R3* represents a single bond, the compounds of formula (II) or a pharmaceutically acceptable salt thereof in accordance with the present disclosure have the following formula (IIb): wherein R1, R2, L1, G and BA are as defined in the present disclosure. This means that in this particular embodiment, in the drug A, R3 is a hydrogen atom. According to another particular embodiment, when R3* represents a divalent radical formed from R3 as defined in the present disclosure, the compounds of formula (II) or a pharmaceutically acceptable salt thereof in accordance with the present disclosure have the following formula (IIbb): wherein R1, R2, L1, G and BA are as defined in the present disclosure and R3* is a divalent R3 as defined in the present disclosure. This means that in this particular embodiment, in the drug A, R3 is not a hydrogen atom. According to a particular embodiment, the binding agent BA represents an antibody Ab, for instance a monoclonal antibody or a VHH antibody. Among the compounds of formula (II) that are subject-matter of the present disclosure, a group of compounds is composed of the compounds wherein: A is of formula (A) in which: R1 represents: - a (C1-C6)alkyl- group, in particular a methyl group; - a NH2-(C1-C6)alkyl- group, in particular a NH2-(CH2)5- group; - a phenyl(C1-C6)alkyl- group, in particular a phenyl-CH2- group, being unsubstituted or substituted by at least one substituent, in particular substituted on the phenyl ring by at least one substituent, for instance by one substituent, selected from: - a (C1-C6)alkyl- group, in particular a methyl group (or a -CH2- group if substituted) or an isopropyl group (or a -CH(CH3)2- group if substituted), being unsubstituted or substituted by at least one substituent, in particular by one substituent, selected from: - a -NR4R5 group wherein R4 and R5, being independently from each other selected from: a hydrogen atom and a (C1-C16)alkyl- group, in particular a methyl group, for instance -NR4R5is -NH2or -NH(CH3); or R4and R5form together with the nitrogen atom to which they are attached an unsubstituted (C3-C10)membered heterocycloalkyl- group comprising one to four heteroatoms selected from oxygen, nitrogen and sulfur, in particular an unsubstituted (C3-C10)membered heterocycloalkyl- group comprising two nitrogen atoms, for instance a piperazinyl group; or - a (C3-C10)cycloalkyl(C1-C6)alkyl- group, in particular a cyclohexyl-CH2- group, being unsubstituted or substituted, in particular substituted on the (C3-C10)cycloalkyl- group, by at least one substituent, in particular by one substituent, selected from -NH2 and a NH2-(C1- C6)alkyl- group such as a NH2-CH2- group; R2 represents : - a (C1-C6)alkyl- group, in particular a -(CH2)3-CH3 group; - a (C1-C6)alkylthio- group, in particular a -S-(CH2)2-CH3 group; or - a (C1-C6)alkyl-NH- group, in particular a -NH-(CH2)2-CH3 group; and R3 represents : - a -OR6 group wherein R6 is a (C1-C6)alkyl- group, in particular a -O-isopropyl group (that is to say a -O-CH(CH3)2 group); - a -NR7R8group wherein R7and R8form together with the nitrogen atom to which they are attached a (C3-C10)membered heterocycloalkyl- group comprising one to four heteroatoms selected from oxygen, nitrogen, and sulfur, in particular comprising two nitrogen atoms, for instance a piperazinyl group; or - a (C3-C10)membered heterocycloalkyl- group comprising one to four heteroatoms selected from oxygen, nitrogen and sulfur, in particular one nitrogen atom or two nitrogen atoms, for instance a dihydropyrrolyl group such as a 2,5-dihydro-1H-pyrrolyl group, or a piperazinyl group; L1 represents: *-C(O)-O-CH2-para-phenyl-NH-Cit-Val-Glu-C(O)-(CH2)3-C(O)-NH-(CH2- CH2-O)3-(CH2)2-** ; *-C(O)-O-CH2-para-phenyl-NH-Ala-Val-Glu-C(O)-(CH2)3-C(O)-NH-(CH2- CH2-O)3-(CH2)2-**; *-Cit-Val-C(O)-(CH2-CH2-O)3-(CH2)2-NH-C(O)-(CH2)2-**; *-Cit-Val-C(O)-(CH2)3-C(O)-NH-(CH2-CH2-O)3-(CH2)2-**; *-Ala-Val-C(O)-(CH2)3-C(O)-NH-(CH2-CH2-O)3-(CH2)2-**; *-C(O)-O-CH2-para-phenyl-NH-Cit-Val-Glu-C(O)-(CH2)3-C(O)-NH-(CH2- CH2-O)3-(CH2)2-NH-C(O)-(CH2)2-** ; *-C(O)-O-CH2-para-phenyl-NH-Ala-Val-Glu--C(O)-(CH2)3-C(O)-NH-(CH2- CH2-O)3-(CH2)2-NH-C(O)-(CH2)2-**; *-Cit-Val-C(O)-(CH2)3-C(O)-NH-(CH2-CH2-O)3-(CH2)2-NH-C(O)-(CH2)2-**; *-Ala-Val-C(O)-(CH2)3-C(O)-NH-(CH2-CH2-O)3-(CH2)2-NH-C(O)-(CH2)2-**, *-C(O)-(CH2-CH2-O)24-CH2-CH2-**; *-(CH2-CH2-O)23-CH2-CH2-**; *-C(O)-(CH2-CH2-O)20-CH2-CH2-**; *-C(O)-(CH2-CH2-O)16-CH2-CH2-**; *-C(O)-(CH2-CH2-O)12-CH2-CH2-**; *-C(O)-(CH2-CH2-O)8-CH2-CH2-**; *-C(O)-C(CH3)2-CH2-O-(CH2-CH2-O)20-CH2-CH2-**; *-C(O)-O-(CH2-CH2-O)20-CH2-CH2-**; *-C(O)-(CH2-CH2-O)24-CH2-CH2-NH-C(O)-CH2-CH2-**; *-C(O)-(CH2-CH2-O)20-CH2-CH2-NH-C(O)-CH2-CH2-**; or *-C(O)-(CH2-CH2-O)12-CH2-CH2-NH-C(O)-CH2-CH2-**; the single asterisk (*) indicating the site of covalent attachment to the A drug unit radical and the double asterisk (**) indicating the site of covalent attachment to the G radical belonging to the -G-BA group; BA represents an antibody, such as a monoclonal antibody or a VHH antibody. According to a particular embodiment, the compounds of formula (II) or a pharmaceutically acceptable salt thereof are chosen among compounds of formula (II1) or of formula (II2): A-(La)m-(AA)w-(Lb)p-Lc-Ld’-G-BA (II1) wherein: A, La, m, (AA)w, AA, w, Lb, p, Lc, Ld’ and BA are as defined in the present disclosure; G represents the product of reaction between RCG1 as defined in the present disclosure and RCG2, a reactive group present on the binding agent, for instance G is selected from the group consisting of : ; for instance, the left side of the G groups being linked to BA and the right side of the G groups being linked to Ld’, for instance G represents the following groups:

[0029] , A-(P)o-L-Ld-G-BA (II2) wherein: A, P, o, L, Ld and BA are as defined in the present disclosure; G represents the product of reaction between RCG1 as defined in the present disclosure and RCG2, a reactive group present on the binding agent instance G is selected from the group consisting of: ;

[0030] ; for instance, the left side of the G groups being linked to BA and the right side of the G groups being linked to Ld, for instance G represents the following groups: . According to a particular embodiment, the binding agent BA is an antibody Ab such as a monoclonal antibody or a VHH antibody. Among the compounds of formula (II1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which A is of formula (A1) or of formula (A2) in which: R1, R2 and R3 are as defined in the present disclosure; the single asterisk (*) indicates the site of covalent attachment to -(La)m-(AA)w-(Lb)p-Lc- Ld’-G-BA; R1* represents: - either a single bond, which means that -(La)m-(AA)w-(Lb)p-Lc-Ld’-G-BA is directly linked to the nitrogen atom of the imidazo[4,5-d]pyridazine ring, - or a divalent radical formed from R1 as defined in the present disclosure, which means that -(La)m-(AA)w-(Lb)p-Lc-Ld’-G-BA is linked to the nitrogen atom of the imidazo[4,5-d]pyridazine ring via R1; R3* represents: - either a single bond, which means that -(La)m-(AA)w-(Lb)p-Lc-Ld’-G-BA is directly linked to the carbon atom of the imidazo[4,5-d]pyridazine ring, - or a divalent radical formed from R3as defined in the present disclosure, which means that -(La)m-(AA)w-(Lb)p-Lc-Ld’-G-BA is linked to the carbon atom of the imidazo[4,5-d]pyridazine ring via R3. According to one particular embodiment, A is of formula (A1). According to another embodiment, A is of formula (A2). Thus, according to a particular embodiment, when R1* represents a single bond, the compounds of formula (II1) or a pharmaceutically acceptable salt thereof in accordance with the present disclosure have the following formula (IIa1): wherein R2, R3, La, m, AA, w, Lb, p, Lc, Ld’, G and BA are as defined in the present disclosure. This means that in this particular embodiment, in the drug A, R1 is a hydrogen atom. According to another particular embodiment, when R1* represents a divalent radical formed from R1 as defined in the present disclosure, the compounds of formula (II1) or a pharmaceutically acceptable salt thereof in accordance with the present disclosure have the following formula (IIaa1): wherein R2, R3, La, m, AA, w, Lb, p, Lc, Ld’, G and BA are as defined in the present disclosure and R1* is a divalent R1 as defined in the present disclosure. This means that in this particular embodiment, in the drug A, R1 is not a hydrogen atom. According to another particular embodiment, when R3* represents a single bond, the compounds of formula (II1) or a pharmaceutically acceptable salt thereof in accordance with the present disclosure have the following formula (IIb1): wherein R1, R2, La, m, AA, w, Lb, p, Lc, Ld’, G and BA are as defined in the present disclosure. This means that in this particular embodiment, in the drug A, R3 is a hydrogen atom. According to another particular embodiment, when R3* represents a divalent radical formed from R3 as defined in the present disclosure, the compounds of formula (II1) or a pharmaceutically acceptable salt thereof in accordance with the present disclosure have the following formula (IIbb1): wherein R1, R2, La, m, AA, w, Lb, p, Lc, Ld’, G and BA are as defined in the present disclosure and R3* is a divalent R3 as defined in the present disclosure. This means that in this particular embodiment, in the drug A, R3 is not a hydrogen atom. Among the compounds of formula (II1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which A is selected from the group consisting of:

[0031] . Among the compounds of formula (II1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which A is selected from the group consisting of: ;

[0032] . Among the compounds of formula (II1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which La is a self-immolative linker. Self immolative linkers are well known for the person of the art. La is a covalent assembly tailored to correlate the cleavage of two chemical bonds after activation of a protective part in a precursor. Thus, its list has not to be limited or restricted. For instance, La represents a *-C(O)-O-(CR14R15)-aryl-NR16-** group, *-C(O)-O- (CR14R15)-heteroaryl-NR16-** group, a *-C(O)-NR17-(C2-C6)alkyl-NR18-**, a *-C(O)-NR17-(C2-C6)alkyl-NR18-C(O)-O-CR15R14-aryl-NR16-** group, a *-C(O)-NR17-(C2-C6)alkyl- NR18-C(O)-O-CR15R14-heteroaryl-NR16-** group, a *-CR15R14-aryl-NR16-** group or a *- CR15R14-heteroaryl-NR16-** group, aryl being a (C6-C10) membered aryl group and heteroaryl being a (C5-C10) membered heteroaryl group comprising one to four heteroatoms selected from oxygen, nitrogen and sulfur, the single asterisk (*) indicating the site of covalent attachment to the A drug unit radical and the double asterisk (**) indicating the site of covalent attachment to the (AA)w radical, R14, R15, R16, R17and R18being a hydrogen atom or a (C1-C6)alkyl group. Among the compounds of formula (II1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which La represents a *-C(O)-O-CH2- phenyl-NH-** group, the single asterisk (*) indicating the site of covalent attachment to the A drug unit radical and the double asterisk (**) indicating the site of covalent attachment to the (AA)w radical. Among the compounds of formula (II1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which in (AA)w, w represents an integer from 1 to 6, and AA is chosen from valine (Val), citrulline (Cit), alanine (Ala), and glutamic acid (Glu). Among the compounds of formula (II1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which in (AA)w, w represents an integer 2 or 3, and AA is chosen from valine (Val), citrulline (Cit), alanine (Ala), and glutamic acid (Glu). For instance, (AA)w comprises a Citrulline (Cit). For instance, (AA)w is chosen among Glu-Val-Cit; Glu-Val-Ala; Val-Cit or Val- Ala. For instance, when the amino acid sequence (AA)w is Glu-Val-Cit, the citrulline (Cit) is linked to La or to A (if La is absent, that is to say if m is 0) and the glutamic acid (Glu) is linked to Lb or to Lc (if Lb is absent, that is to say if p is 0). For instance, when the amino acid sequence (AA)w is Glu-Val-Ala, the alanine (Ala) is linked to La or to A (if La is absent, that is to say if m is 0) and the glutamic acid (Glu) is linked to Lb or to Lc (if Lb is absent, that is to say if p is 0). For instance, when the amino acid sequence (AA)w is Val-Cit, the citrulline (Cit) is linked to La or to A (if La is absent, that is to say if m is 0) and the valine (Val) is linked to Lb or to Lc (if Lb is absent, that is to say if p is 0). For instance, when the amino acid sequence (AA)w is Val-Ala, the alanine (Ala) is linked to La or to A (if La is absent, that is to say if m is 0) and the valine (Val) is linked to Lb or to Lc (if Lb is absent, that is to say if p is 0). For instance, (AA)w is Val-Cit. Among the compounds of formula (II1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which Lb represents a *-C(O)- (C1-C6)alkyl-C(O)-NH-** group or a *-C(O)-** group, the single asterisk (*) indicating the site of covalent attachment to the (AA)w radical and the double asterisk (**) indicating the site of covalent attachment to the Lc radical. Among the compounds of formula (II1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which Lb represents a *-C(O)- (CH2)3-C(O)-NH-** group or a *-C(O)-** group, the single asterisk (*) indicating the site of covalent attachment to the (AA)w radical and the double asterisk (**) indicating the site of covalent attachment to the Lc radical. Among the compounds of formula (II1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which Lc represents a *–(CH2- CH2-O)n-** group in which n represents an integer from 2 to 12, the single asterisk (*) indicating the site of covalent attachment to the Lb radical if present (that is to say if p is 1) or directly to the (AA)w radical if Lb is not present (that is to say if p is 0) and the double asterisk (**) indicating the site of covalent attachment to the Ld’ radical. Among the compounds of formula (II1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which Lc represents a *–(CH2- CH2-O)n-** group in which n represents an integer from 3 to 7, the single asterisk (*) indicating the site of covalent attachment to the Lb radical if present (that is to say if p is 1) or directly to the (AA)w radical if Lb is not present (that is to say if p is 0) and the double asterisk (**) indicating the site of covalent attachment to the Ld’ radical. Among the compounds of formula (II1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which Lc represents a *–(CH2- CH2-O)n-** group in which n represents an integer 3 or 4 , the single asterisk (*) indicating the site of covalent attachment to the Lb radical if present (that is to say if p is 1) or directly to the (AA)w radical if Lb is not present (that is to say if p is 0) and the double asterisk (**) indicating the site of covalent attachment to the Ld’ radical. Among the compounds of formula (II1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which Ld’ represents a *-(C2-C6)alkyl-** group, a *-(C2-C6)alkyl-NH-C(O)-(C2-C6)alkyl-** group or a *-(C2-C6)alkyl-C(O)-NH-(C2-C6)alkyl-** group, the single asterisk (*) indicating the site of covalent attachment to the Lc radical and the double asterisk (**) indicating the site of covalent attachment to the G group belonging to the -G-BA radical. Among the compounds of formula (II1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which Ld’ represents a *-(CH2)2-** group, a *-(CH2)2-NH-C(O)-(CH2)2-** group or a *-(CH2)2-C(O)-NH-(CH2)2-** group, the single asterisk (*) indicating the site of covalent attachment to the Lc radical and the double asterisk (**) indicating the site of covalent attachment to the G group belonging to the -G-BA radical. Among the compounds of formula (II1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which m represents an integer 1. Among the compounds of formula (II1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which m represents 0. Among the compounds of formula (II1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which p represents an integer 1. Among the compounds of formula (II1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which p represents 0. Among the compounds of formula (II1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which G is selected from the group consisting of: ;

[0033] , the left side of the G groups being linked to BA and the right side of the G groups being linked to Ld’. Among the compounds of formula (II1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which G is selected from the group consisting of: , the left side of the G groups being linked to BA and the right side of the G groups being linked to Ld’. Among the compounds of formula (II1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which G is selected from the group consisting of: , the left side of the G groups being linked to BA and the right side of the G groups being linked to Ld’. Among the compounds of formula (II1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which when Ld’ represents a *-(C2-C6)alkyl-** group, the single asterisk (*) indicating the site of covalent attachment to the Lc radical and the double asterisk (**) indicating the site of covalent attachment to the G group belonging to the -G-BA radical, then G is , the left side of the G groups being linked to BA and the right side of the G groups being linked to Ld’. Among the compounds of formula (II1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which when Ld’ represents a *-(C2-C6)alkyl-NH-C(O)-(C2-C6)alkyl-** group, the single asterisk (*) indicating the site of covalent attachment to the Lc radical and the double asterisk (**) indicating the site of covalent attachment to the G group belonging to the -G-BA radical, then , the left side of the G groups being linked to BA and the right side of the G groups being linked to Ld’. Among the compounds of formula (II1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which when Ld’ represents a *-(CH2)2-** group, the single asterisk (*) indicating the site of covalent attachment to the Lc radical and the double asterisk (**) indicating the site of covalent attachment to the G group belonging to the -G-BA radical, then G is , the left side of the G groups being linked to BA and the right side of the G groups being linked to Ld’. Among the compounds of formula (II1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which when Ld’ represents a *-(CH2)2-NH-C(O)-(CH2)2-** group, the single asterisk (*) indicating the site of covalent attachment to the Lc radical and the double asterisk (**) indicating the site of covalent attachment to the G group belonging to the -G-BA radical, then , the left side of the G groups being linked to BA and the right side of the G groups being linked to Ld’. Among the compounds of formula (II1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which BA is an antibody Ab. Among the compounds of formula (II1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which Ab is a monoclonal antibody, for instance tusamitamab, and avelumab variants. Among the compounds of formula (II1) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which Ab is a VHH antibody. All these sub-groups taken alone or in combination are part of the present disclosure. According to a particular embodiment, the disclosure relates to a compound / conjugate of formula (II1) or a pharmaceutically acceptable salt thereof wherein A, G and BA are as defined in the present disclosure; and La is *-C(O)-O-CH2-para-phenyl-NH**; m is 1; AA is selected from Ala, Val, Cit and Glu; w is 2 or 3; Lb is *-C(O)-(CH2)3-C(O)-NH-**; p is 1; Lc is *-(CH2-CH2-O)3-**; and Ld’ is *-(CH2)2-** or *-(CH2)2-NH-C(O)-(CH2)2-**. According to another particular embodiment, the disclosure relates to a compound / conjugate of formula (II1) or a pharmaceutically acceptable salt thereof wherein: A, G and BA are as defined in the present disclosure; m is 0; AA is selected from Ala, Val and Cit; w is 2; Lb is *-C(O)-(CH2)3-C(O)-NH-** or *-C(O)-*; p is 1; Lc is *-(CH2-CH2-O)3-**; and Ld’ is *-(CH2)2-** or *-(CH2)2-NH-C(O)-(CH2)2-**. According to another particular embodiment, the disclosure relates to a compound / conjugate of formula (II1) or a pharmaceutically acceptable salt thereof wherein the -(La)m-(AA)w-(Lb)p-Lc-Ld’- part is selected from the group consisting of: *-C(O)-O-CH2-para-phenyl-NH-Cit-Val-Glu-C(O)-(CH2)3-C(O)-NH-(CH2- CH2-O)3-(CH2)2-** ; *-C(O)-O-CH2-para-phenyl-NH-Ala-Val-Glu-C(O)-(CH2)3-C(O)-NH-(CH2- CH2-O)3-(CH2)2-**; *-Cit-Val-C(O)-(CH2)3-C(O)-NH-(CH2-CH2-O)3-(CH2)2-**; *-Ala-Val-C(O)-(CH2)3-C(O)-NH-(CH2-CH2-O)3-(CH2)2-**; *-C(O)-O-CH2-para-phenyl-NH-Cit-Val-Glu-C(O)-(CH2)3-C(O)-NH-(CH2- CH2-O)3-(CH2)2-NH-C(O)-(CH2)2-** ; *-C(O)-O-CH2-para-phenyl-NH-Ala-Val-Glu-C(O)-(CH2)3-C(O)-NH-(CH2- CH2-O)3-(CH2)2-NH-C(O)-(CH2)2-**; *-Cit-Val-C(O)-(CH2)3-C(O)-NH-(CH2-CH2-O)3-(CH2)2-NH-C(O)-(CH2)2-**; *-Ala-Val-C(O)-(CH2)3-C(O)-NH-(CH2-CH2-O)3-(CH2)2-NH-C(O)-(CH2)2-**; and *-Cit-Val-C(O)-(CH2-CH2-O)3-(CH2)2-NH-C(O)-(CH2)2-**, the single asterisk (*) indicating the site of covalent attachment to the A drug unit radical and the double asterisk (**) indicating the site of covalent attachment to the G radical belonging to the -G-BA group. Among the compounds of formula (II1) that are subject-matter of the present disclosure, a group of compounds is composed of the compounds wherein: A is of formula (A) in which: R1 represents: - a (C1-C6)alkyl- group, in particular a methyl group; - a NH2-(C1-C6)alkyl- group, in particular a NH2-(CH2)5- group; - a phenyl(C1-C6)alkyl- group, in particular a phenyl-CH2- group, being unsubstituted or substituted by at least one substituent, in particular substituted on the phenyl ring by at least one substituent, for instance by one substituent, selected from: - a (C1-C6)alkyl- group, in particular a methyl group (or a -CH2- group if substituted) or an isopropyl group (or a -CH(CH3)2- group if substituted), being unsubstituted or substituted by at least one substituent, in particular by one substituent, selected from: - a -NR4R5group wherein R4and R5, being independently from each other selected from: a hydrogen atom and a (C1-C16)alkyl- group, in particular a methyl group, for instance -NR4R5 is -NH2 or -NH(CH3); or R4 and R5 form together with the nitrogen atom to which they are attached an unsubstituted (C3-C10)membered heterocycloalkyl- group comprising one to four heteroatoms selected from oxygen, nitrogen and sulfur, in particular an unsubstituted (C3-C10)membered heterocycloalkyl- group comprising two nitrogen atoms, for instance a piperazinyl group; or - a (C3-C10)cycloalkyl(C1-C6)alkyl- group, in particular a cyclohexyl-CH2- group, being unsubstituted or substituted, in particular substituted on the (C3-C10)cycloalkyl- group, by at least one substituent, in particular by one substituent, selected from -NH2and a NH2-(C1- C6)alkyl- group such as a NH2-CH2- group; R2 represents : - a (C1-C6)alkyl- group, in particular a -(CH2)3-CH3 group; - a (C1-C6)alkylthio- group, in particular a -S-(CH2)2-CH3group; or - a (C1-C6)alkyl-NH- group, in particular a -NH-(CH2)2-CH3group; and R3 represents : - a -OR6 group wherein R6 is a (C1-C6)alkyl- group, in particular a -O-isopropyl group (that is to say a -O-CH(CH3)2group); - a -NR7R8 group wherein R7 and R8 form together with the nitrogen atom to which they are attached a (C3-C10)membered heterocycloalkyl- group comprising one to four heteroatoms selected from oxygen, nitrogen, and sulfur, in particular comprising two nitrogen atoms, for instance a piperazinyl group; or - a (C3-C10)membered heterocycloalkyl- group comprising one to four heteroatoms selected from oxygen, nitrogen and sulfur, in particular one nitrogen atom or two nitrogen atoms, for instance a dihydropyrrolyl group such as a 2,5-dihydro-1H-pyrrolyl group, or a piperazinyl group; *-(La)m-(AA)w-(Lb)p-Lc-Ld’-** represents: *-C(O)-O-CH2-para-phenyl-NH-Cit-Val-Glu-C(O)-(CH2)3-C(O)-NH-(CH2- CH2-O)3-(CH2)2-** ; *-C(O)-O-CH2-para-phenyl-NH-Ala-Val-Glu-C(O)-(CH2)3-C(O)-NH-(CH2- CH2-O)3-(CH2)2-**; *-Cit-Val-C(O)-(CH2-CH2-O)3-(CH2)2-NH-C(O)-(CH2)2-**; *-Cit-Val-C(O)-(CH2)3-C(O)-NH-(CH2-CH2-O)3-(CH2)2-**; *-Ala-Val-C(O)-(CH2)3-C(O)-NH-(CH2-CH2-O)3-(CH2)2-**; *-C(O)-O-CH2-para-phenyl-NH-Cit-Val-Glu-C(O)-(CH2)3-C(O)-NH-(CH2- CH2-O)3-(CH2)2-NH-C(O)-(CH2)2-** ; *-C(O)-O-CH2-para-phenyl-NH-Ala-Val-Glu--C(O)-(CH2)3-C(O)-NH-(CH2- CH2-O)3-(CH2)2-NH-C(O)-(CH2)2-**; *-Cit-Val-C(O)-(CH2)3-C(O)-NH-(CH2-CH2-O)3-(CH2)2-NH-C(O)-(CH2)2-**; or *-Ala-Val-C(O)-(CH2)3-C(O)-NH-(CH2-CH2-O)3-(CH2)2-NH-C(O)-(CH2)2-**, the single asterisk (*) indicating the site of covalent attachment to the A drug unit radical and the double asterisk (**) indicating the site of covalent attachment to the G radical belonging to the -G-BA group; BA represents an antibody, such as a monoclonal antibody or a VHH antibody. Among the compounds of formula (II2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which A is of formula (A1) or of formula (A2) in which: R1, R2 and R3 are as defined in the present disclosure; the single asterisk (*) indicates the site of covalent attachment to –(P)o-L-Ld-G-BA; R1* represents: - either a single bond, which means that –(P)o-L-Ld-G-BA is directly linked to the nitrogen atom of the imidazo[4,5-d]pyridazine ring, - or a divalent radical formed from R1as defined in the present disclosure, which means that –(P)o-L-Ld-G-BA is linked to the nitrogen atom of the imidazo[4,5-d]pyridazine ring via R1; R3* represents: - either a single bond, which means that –(P)o-L-Ld-G-BA is directly linked to the carbon atom of the imidazo[4,5-d]pyridazine ring, - or a divalent radical formed from R3as defined in the present disclosure, which means that –(P)o-L-Ld-G-BA is linked to the carbon atom of the imidazo[4,5-d]pyridazine ring via R3. According to one particular embodiment, A is of formula (A1). According to another embodiment, A is of formula (A2). Thus, according to a particular embodiment, when R1* represents a single bond, the compounds of formula (II2) or a pharmaceutically acceptable salt thereof in accordance with the present disclosure have the following formula (IIa2): wherein R2, R3, P, o, L, Ld, G and BA are as defined in the present disclosure. This means that in this particular embodiment, in the drug A, R1 is a hydrogen atom. According to another particular embodiment, when R1* represents a divalent radical formed from R1 as defined in the present disclosure, the compounds of formula (II2) or a pharmaceutically acceptable salt thereof in accordance with the present disclosure have the following formula (IIaa2): wherein R2, R3, P, o, L, Ld, G and BA are as defined in the present disclosure and R1* is a divalent R1as defined in the present disclosure. This means that in this particular embodiment, in the drug A, R1 is not a hydrogen atom. According to another particular embodiment, when R3* represents a single bond, the compounds of formula (II2) or a pharmaceutically acceptable salt thereof in accordance with the present disclosure have the following formula (IIb2): wherein R1, R2, P, o, L, Ld, G and BA are as defined in the present disclosure. This means that in this particular embodiment, in the drug A, R3 is a hydrogen atom. According to another particular embodiment, when R3* represents a divalent radical formed from R3 as defined in the present disclosure, the compounds of formula (II2) or a pharmaceutically acceptable salt thereof in accordance with the present disclosure have the following formula (IIbb2): wherein R1, R2, P, o, L, Ld, G and BA are as defined in the present disclosure and R3* is a divalent R3as defined in the present disclosure. This means that in this particular embodiment, in the drug A, R3 is not a hydrogen atom. Among the compounds of formula (II2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which A is selected from the group consisting of: ;

[0034] . Among the compounds of formula (II2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which A is selected from the group consisting of:

[0035] . Among the compounds of formula (II2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which P is a -C(O)- group. Among the compounds of formula (II2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which P is a -C(O)-O- group. Among the compounds of formula (II2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which P is a -S(O2)- group. Among the compounds of formula (II2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which P is a -C(O)-C(CH3)2-CH2- O- group. Among the compounds of formula (II2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which P is a -C(O)-NH- group. Among the compounds of formula (II2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which group. Among the compounds of formula (II2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which P is a group. Among the compounds of formula (II2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which o is 0. Among the compounds of formula (II2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which o is 1. Among the compounds of formula (II2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which L represents a *–(CH2- CH2-O)n-** group in which n represents an integer from 8 to 25, the single asterisk (*) indicating the site of covalent attachment to the P radical if present (that is to say if o is 1) or directly to the A radical if P is not present (that is to say if o is 0) and the double asterisk (**) indicating the site of covalent attachment to the Ld radical. Among the compounds of formula (II2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which L represents a *–(CH2- CH2-O)n-** group in which n represents 8, 12, 16, 20, 23 or 24, the single asterisk (*) indicating the site of covalent attachment to the P radical if present (that is to say if o is 1) or directly to the A radical if P is not present (that is to say if o is 0) and the double asterisk (**) indicating the site of covalent attachment to the Ld radical. Among the compounds of formula (II2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which Ld represents a *-(C2- C6)alkyl-** group, a *-(C2-C6)alkyl-NH-C(O)-(C2-C6)alkyl-** group or a *-(C2-C6)alkyl- C(O)-NH-(C2-C6)alkyl-** group, the single asterisk (*) indicating the site of covalent attachment to the L radical and the double asterisk (**) indicating the site of covalent attachment to the G group belonging to the -G-BA radical. Among the compounds of formula (II2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which Ld represents a *–(CH2)2- ** group, a *-(CH2)2-NH-C(O)-(CH2)2-** group or a *-(CH2)2-C(O)-NH-(CH2)2-** group, the single asterisk (*) indicating the site of covalent attachment to the L radical and the double asterisk (**) indicating the site of covalent attachment to the G group belonging to the -G-BA radical. Among the compounds of formula (II2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which G is selected from the group consisting of: ; the left side of the G groups being linked to BA and the right side of the G groups being linked to Ld. Among the compounds of formula (II2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which G is selected from the group consisting of: ; Among the compounds of formula (II2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which G is selected from the group consisting of: . Among the compounds of formula (II2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which when Ld represents a *-(C2-C6)alkyl-** group, the single asterisk (*) indicating the site of covalent attachment to the L radical and the double asterisk (**) indicating the site of covalent attachment to the G group belonging to the -G-BA radical, then G is , the left side of the G groups being linked to BA and the right side of the G groups being linked to Ld. Among the compounds of formula (II2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which when Ld represents a *-(C2-C6)alkyl-** group, the single asterisk (*) indicating the site of covalent attachment to the L radical and the double asterisk (**) indicating the site of covalent attachment to the G group belonging to the -G-BA radical, then , the right side of the G groups being linked to BA and the left side of the G groups being linked to Ld. Among the compounds of formula (II2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which when Ld represents a *-(C2-C6)alkyl-NH-C(O)-(C2-C6)alkyl-** group, the single asterisk (*) indicating the site of covalent attachment to the L radical and the double asterisk (**) indicating the site of covalent attachment to the G group belonging to the -G-BA radical, then , the left side of the G groups being linked to BA and the right side of the G groups being linked to Ld. Among the compounds of formula (II2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which when Ld represents a *-(CH2)2-** group, the single asterisk (*) indicating the site of covalent attachment to the L radical and the double asterisk (**) indicating the site of covalent attachment to the G group belonging to the -G-BA radical, then , the left side of the G groups being linked to BA and the right side of the G groups being linked to Ld. Among the compounds of formula (II2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which when Ld represents a *-(CH2)2-** group, the single asterisk (*) indicating the site of covalent attachment to the L radical and the double asterisk (**) indicating the site of covalent attachment to the G group belonging to the -G-BA radical, then the right side of the G groups being linked to BA and the left side of the G groups being linked to Ld. Among the compounds of formula (II2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which when Ld represents a *- (CH2)2-NH-C(O)-(CH2)2-** group, the single asterisk (*) indicating the site of covalent attachment to the L radical and the double asterisk (**) indicating the site of covalent attachment to the G group belonging to the -G-BA radical, then , the left side of the G groups being linked to BA and the right side of the G groups being linked to Ld. Among the compounds of formula (II2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which BA is an antibody Ab. Among the compounds of formula (II2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which BA is a monoclonal antibody, for instance tusamitamab (CAS [2349294-95-5]) and avelumab variants. Among the compounds of formula (II2) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which BA is a VHH antibody. All these sub-groups taken alone or in combination are part of the present disclosure. According to a particular embodiment, the disclosure relates to a compound / conjugate of formula (II2) or a pharmaceutically acceptable salt thereof wherein the -(P)o-L-Ld- part is selected from the group consisting of: *-C(O)-(CH2-CH2-O)24-CH2-CH2-**; *-(CH2-CH2-O)23-CH2-CH2-**; *-C(O)-(CH2-CH2-O)20-CH2-CH2-**; *-C(O)-(CH2-CH2-O)16-CH2-CH2-**; *-C(O)-(CH2-CH2-O)12-CH2-CH2-**; *-C(O)-(CH2-CH2-O)8-CH2-CH2-**; *-C(O)-C(CH3)2-CH2-O-(CH2-CH2-O)20-CH2-CH2-**; *-C(O)-O-(CH2-CH2-O)20-CH2-CH2-**;

[0036] *-C(O)-(CH2-CH2-O)24-CH2-CH2-NH-C(O)-CH2-CH2-**; *-C(O)-(CH2-CH2-O)20-CH2-CH2-NH-C(O)-CH2-CH2-**; and *-C(O)-(CH2-CH2-O)12-CH2-CH2-NH-C(O)-CH2-CH2-**; the single asterisk (*) indicating the site of covalent attachment to the A drug unit radical and the double asterisk (**) indicating the site of covalent attachment to the G radical belonging to the -G-BA group. Among the compounds of formula (II2) that are subject-matter of the present disclosure, a group of compounds is composed of the compounds wherein: A is of formula (A) in which: R1 represents: - a (C1-C6)alkyl- group, in particular a methyl group; - a NH2-(C1-C6)alkyl- group, in particular a NH2-(CH2)5- group; - a phenyl(C1-C6)alkyl- group, in particular a phenyl-CH2- group, being unsubstituted or substituted by at least one substituent, in particular substituted on the phenyl ring by at least one substituent, for instance by one substituent, selected from: - a (C1-C6)alkyl- group, in particular a methyl group (or a -CH2- group if substituted) or an isopropyl group (or a -CH(CH3)2- group if substituted), being unsubstituted or substituted by at least one substituent, in particular by one substituent, selected from: - a -NR4R5 group wherein R4 and R5, being independently from each other selected from: a hydrogen atom and a (C1-C16)alkyl- group, in particular a methyl group, for instance -NR4R5 is -NH2 or -NH(CH3); or R4 and R5 form together with the nitrogen atom to which they are attached an unsubstituted (C3-C10)membered heterocycloalkyl- group comprising one to four heteroatoms selected from oxygen, nitrogen and sulfur, in particular an unsubstituted (C3-C10)membered heterocycloalkyl- group comprising two nitrogen atoms, for instance a piperazinyl group; or - a (C3-C10)cycloalkyl(C1-C6)alkyl- group, in particular a cyclohexyl-CH2- group, being unsubstituted or substituted, in particular substituted on the (C3-C10)cycloalkyl- group, by at least one substituent, in particular by one substituent, selected from -NH2and a NH2-(C1- C6)alkyl- group such as a NH2-CH2- group; R2 represents : - a (C1-C6)alkyl- group, in particular a -(CH2)3-CH3group; - a (C1-C6)alkylthio- group, in particular a -S-(CH2)2-CH3group; or - a (C1-C6)alkyl-NH- group, in particular a -NH-(CH2)2-CH3 group; and R3 represents : - a -OR6group wherein R6is a (C1-C6)alkyl- group, in particular a -O-isopropyl group (that is to say a -O-CH(CH3)2 group); - a -NR7R8 group wherein R7 and R8 form together with the nitrogen atom to which they are attached a (C3-C10)membered heterocycloalkyl- group comprising one to four heteroatoms selected from oxygen, nitrogen, and sulfur, in particular comprising two nitrogen atoms, for instance a piperazinyl group; or - a (C3-C10)membered heterocycloalkyl- group comprising one to four heteroatoms selected from oxygen, nitrogen and sulfur, in particular one nitrogen atom or two nitrogen atoms, for instance a dihydropyrrolyl group such as a 2,5-dihydro-1H-pyrrolyl group, or a piperazinyl group; *-(P)o-L-Ld-** represents: *-C(O)-(CH2-CH2-O)24-CH2-CH2-**; *-(CH2-CH2-O)23-CH2-CH2-**; *-C(O)-(CH2-CH2-O)20-CH2-CH2-**; *-C(O)-(CH2-CH2-O)16-CH2-CH2-**; *-C(O)-(CH2-CH2-O)12-CH2-CH2-**; *-C(O)-(CH2-CH2-O)8-CH2-CH2-**; *-C(O)-C(CH3)2-CH2-O-(CH2-CH2-O)20-CH2-CH2-**; *-C(O)-O-(CH2-CH2-O)20-CH2-CH2-**; *-C(O)-(CH2-CH2-O)24-CH2-CH2-NH-C(O)-CH2-CH2-**; *-C(O)-(CH2-CH2-O)20-CH2-CH2-NH-C(O)-CH2-CH2-**; or *-C(O)-(CH2-CH2-O)12-CH2-CH2-NH-C(O)-CH2-CH2-**; the single asterisk (*) indicating the site of covalent attachment to the A drug unit radical and the double asterisk (**) indicating the site of covalent attachment to the G radical belonging to the -G-BA group; BA represents an antibody, such as a monoclonal antibody or a VHH antibody. Among the compounds / conjugates of formulae (II), (II1) or (II2) that are subject matter of the present disclosure, mention may be made for instance to the following compounds:

[0037]

[0038]

[0039]

[0040] wherein Ab represents an antibody, for instance a monoclonal antibody or a VHH antibody.

[0041] Among the compounds of formulae (II), (III) and (112) that are subject matter of the disclosure, a group of compounds is composed of the compounds for which BA is a monoclonal antibody, for instance: Tusamitamab (CAS [2349294-95-5]), Avelumab_K76R-K100R, A velumab_K360C , Avelumab_LALA-K360C, 769_VarB_VH7 / VL2, p01_CEA_l_07, p01_CEA_l_07_A118C, p01_CEA_l_07_E152C, p01_CEA_l_07_K360C, p01_CEA_l_07_K414C, p07_CEA_3_50_VH 1_A 118C, p07_CEA_3_50_VHl_K360C, p07_CEA_3_50_VH 1_K414C, p01_CEA_1_07_A118C_K360C, p01_CEA_1_07_E152C_K360C, p01_CEA_1_07_K274C_K414C, p07_CEA_3_50_VH1_A118C_K360C, p07_CEA_3_50_VH1_K274C_K414C, In particular, among the compounds / conjugates of formulae (II), (II1) or (II2) or a pharmaceutically acceptable salt thereof that are subject matter of the present disclosure, mention may be made for instance to the following compounds: (c1) CEACAM5_Tusamitamab-P5 ADC (Example 13) (c2) PDL1_Avelumab_K76R-K100R-P5 ADC (Example 14) (c3) CEACAM5_Tusamitamab-P8 ADC (Example 15) (c4) PDL1_Avelumab_K76R-K100R-P8 ADC (Example 16) (c5) CEACAM5_Tusamitamab-P3 ADC (Example 17) (c6) PDL1_Avelumab_K76R_K100R-P3 ADC (Example 18) (c7) CEACAM5_Tusamitamab-Example 3 ADC (Example 19) (c8) PDL1_Avelumab_K76R_K100R-Example 3 ADC (Example 20) (c9) CEACAM5_Tusamitamab-Example 5 ADC (Example 21) (c10) PDL1_Avelumab_K76R_K100R-Example 5 ADC (Example 22) (c11) PDL1_Avelumab_K360C-Example 6 ADC (Example 23) (c12) PDL1_Avelumab_LALA_K360C-Example 6 ADC (Example 24) (c13) CEACAM5_Tusamitamab-Example 2 ADC (Example 25) (c14) PDL1_Avelumab_K76R_K100R-Exemple 2 ADC (Example 26) (c15) CEACAM5_Tusamitamab-Example 7 ADC (Example 27) (c16) PDL1_Avelumab_K76R_K100R-Example 7 ADC (Example 28) (c17) CEACAM5_Tusamitamab-Example 11b ADC (Example 29) (c18) PDL1_Avelumab_K76R_K100R- Example 11b ADC (Example 30) (c19) CEACAM5_Tusamitamab-Example 8 ADC (Example 31) (c20) PDL1_Avelumab_K76R_K100R-Example 8 ADC (Example 32) (c21) PDL1_Avelumab_K360C-P16 ADC (Example 33) (c22) PDL1_Avelumab_K360C-Example 10 ADC (Example 34) (c23) PDL1_Avelumab_LALA_K360C-Example 10 ADC (Example 35) (c24) PDL1_Avelumab_ K360C-P14 ADC (Example 36) (c25) PDL1_Avelumab_LALA_K360C-P14 ADC (Example 37) (c26) PDL1_Avelumab_K76R_K100R-Example 12 ADC (Example 38) (c27) CEACAM5_Tusamitamab-Example 11a ADC (Example 39) (c28) PDL1_Avelumab_K76R_K100R-Example 11a ADC (Example 40) (c29) CEACAM5_Tusamitamab-Example 43 ADC (Example 62) (c30) PDL1_Avelumab_K76R_K100R-Example 43 ADC (Example 63) (c31) CEACAM5_Tusamitamab-Example 45 ADC (Example 64) (c32) CEACAM5_769_VarB_VH7 / VL2-Example 45 ADC (Example 65) (c33) CEACAM5_p01_CEA_1_07-Example 45 ADC (Example 66) (c34) PDL1_Avelumab_K76R_K100R-Example 45 ADC (Example 67) (c35) CEACAM5_p01_CEA_1_07-Example 46 ADC (DAR4) (Example 68) (c36) CEACAM5_p01_CEA_1_07-Example 46 ADC (DAR8) (Example 69) (c37) CEACAM5_p01_CEA_1_07_A118C-Example 46 ADC (Example 70) (c38) CEACAM5_p01_CEA_1_07_E152C-Example 46 ADC (Example 71) (c39) CEACAM5_p01_CEA_1_07_K360C-Example 46 ADC (Example 72) (c40) CEACAM5_p01_CEA_1_07_K414C-Example 46 ADC (Example 73) (c41) CEACAM5_p07_CEA_3_50_VH1_A118C-Example 46 ADC (Example 74) (c42) CEACAM5_p07_CEA_3_50_VH1_K360C-Example 46 ADC (Example 75) (c43) CEACAM5_p07_CEA_3_50_VH1_K414C-Example 46 ADC (Example 76) (c44) CEACAM5_p01_CEA_1_07_A118C_K360C-Example 46 ADC (Example 77) (c45) CEACAM5_p01_CEA_1_07_E152C_K360C-Example 46 ADC (Example 78) (c46) CEACAM5_p01_CEA_1_07_K274C_K414C-Example 46 ADC (Example 79) (c47) CEACAM5_p07_CEA_3_50_VH1_A118C_K360C-Example 46 ADC (Example 80) (c48) CEACAM5_p07_CEA_3_50_VH1_K274C_K414C-Example 46 ADC (Example 81) (c49) PDL1_Avelumab_K360C-Example 46 ADC (Example 82) (c50) PDL1_Avelumab_LALA_K360C-Example 46 ADC (Example 83) (c51) CEACAM5_p01_CEA_1_07_K360C-Example 47 ADC (Example 84) (c52) CEACAM5_p01_CEA_1_07_K360C-P36 ADC (Example 85) (c53) PDL1_Avelumab_K360C-P36 ADC (Example 86) (c54) CEACAM5_p01_CEA_1_07_K360C-Example 48 ADC (Example 87) (c55) PDL1_Avelumab_K360C-Example 48 ADC (Example 88) (c56) CEACAM5_p01_CEA_1_07_K360C-Example 49 ADC (Example 89) (c57) PDL1_Avelumab_K360C-Example 49 ADC (Example 90) (c58) CEACAM5_Tusamitamab-Example 42 ADC (Example 91) (c59) PDL1_Avelumab_K76R_K100R-Example 42 ADC (Example 92) (c60) CEACAM5_Tusamitamab-Example 41 ADC (Example 93) (c61) PDL1_Avelumab_K76R_K100R-Example 41 ADC (Example 94) (c62) CEACAM5_Tusamitamab-P29 ADC (Example 95) (c63) PDL1_Avelumab_K76R_K100R-P29 ADC (Example 96) (c64) CEACAM5_Tusamitamab-P32 ADC (Example 97) (c65) PDL1_Avelumab_K76R_K100R-P32 ADC (Example 98) (c66) CEACAM5_Tusamitamab-P27 ADC (Example 99) (c67) PDL1_Avelumab_K76R_K100R-P27 ADC (Example 100) (c68) CEACAM5_Tusamitamab-P25 ADC (Example 101) (c69) PDL1_Avelumab_K76R_K100R-P25ADC (Example 102) (c70) CEACAM5_p07_CEA_3_50_VH1_K360C-P39 ADC (Example 103) (c71) CEACAM5_p07_CEA_3_50_VH1_A118C_K360C-P39 ADC (Example 104) (c72) CEACAM5_p07_CEA_3_50_VH1_K360C-P40 ADC (Example 105) (c73) CEACAM5_p07_CEA_3_50_VH1_A118C_K360C-P40 ADC (Example 106) (c74) CEACAM5_Tusamitamab-Example 50 ADC (Example 107) (c75) PDL1_Avelumab_K76R_K100R-Example 50 ADC (Example 108) (c76) PDL1_Avelumab_K360C-P45 ADC (Example 109) (c77) CEACAM5_769_VarB_VH7 / VL2-P47 ADC (Example 110) (c78) CEACAM5_p01_CEA_1_07-P47 ADC (Example 111) (c79) CEACAM5_p01_CEA_1_07-Example 51 ADC (DAR4) (Example 112) (c80) CEACAM5_p01_CEA_1_07-Example 51 ADC (DAR8) (Example 113) (c81) PDL1_Avelumab_K360C-Example 51 ADC (Example 114) (c82) PDL1_Avelumab_LALA_K360C-Example 51 ADC (Example 115) (c83) CEACAM5_p01_CEA_1_07_A118C-Example 51 ADC (Example 116) (c84) CEACAM5_p01_CEA_1_07_E152C-Example 51 ADC (Example 117) (c85) CEACAM5_p01_CEA_1_07_K360C-Example 51 ADC (Example 118) (c86) CEACAM5_p01_CEA_1_07_K414C-Example 51 ADC (Example 119) (c87) CEACAM5_p01_CEA_1_07_A118C_K360C-Example 51 ADC (Example 120) (c88) CEACAM5_p01_CEA_1_07_E152C_K360C-Example 51 ADC (Example 121) (c89) CEACAM5_p01_CEA_1_07_K274C_K414C-Example 51 ADC (Example 122) (c90) CEACAM5_Tusamitamab-Example 57 ADC (Example 123) (c91) CEACAM5_Tusamitamab-Example 58 ADC (Example 124) (c92) CEACAM5_Tusamitamab-Example 59 ADC (Example 125) (c93) CEACAM5_Tusamitamab-Example 60 ADC (Example 126) (c94) CEACAM5_Tusamitamab-Example 61 ADC (Example 127) (c95) PDL1_Avelumab_K360C-P52 ADC (Example 128) (c96) PDL1_Avelumab_LALA_K360C-P52 ADC (Example 129) (c97) PDL1_Avelumab_K76R_K100R-Example 54 ADC (Example 130) (c98) CEACAM5_Tusamitamab-Example 53 ADC (Example 131) (c99) PDL1_Avelumab_K76R_K100R-Example 53 ADC (Example 132) (c100) CEACAM5_Tusamitamab-Example 55 ADC (Example 133) (c101) CEACAM5_Tusamitamab-Example 56 ADC (Example 134) (c102) PDL1_Avelumab_K360C-Example 52 ADC (Example 135) (c103) CEACAM5_Tusamitamab-P42 ADC (Example 136) (c104) PDL1_Avelumab_K76R_K100R- P42 ADC (Example 137) The compounds / conjugates of formulae (II), (II1) and (II2) or a pharmaceutically acceptable salt thereof according to the present disclosure can be prepared according to any process known by the skilled person, and for instance by the following processes. Processes are also detailed in the experimental part of the present disclosure. The compound / conjugate of formulae (II), (II1) and (II2) may be prepared by (i) placing in contact and leaving to react: - an, optionally buffered, aqueous solution of a binding agent as defined in the present disclosure for instance of an antibody Ab, comprising a reactive RCG2 group, optionally modified by means of a modifying agent, and - a solution of a compound / payload of formula (I), (I1) or (I2) as defined in the present disclosure, comprising a reactive RCG1 group; RCG1 groups of the compounds / payloads of formula (I), (I1) or (I2) being reactive towards RCG2 groups of the binding agent as defined in the present disclosure for instance of the antibody to form the G group by a covalent bond and forming compounds / conjugates of formula (II), (II1) or (II2); (ii) and then optionally separating the compound of formula (II), (II1) or (II2) formed in step (i) from the unreacted compound of formula (I), (I1) or (I2) and / or from the unreacted antibody and / or from any aggregates that may have been formed. Examples of RCG2, present on the binding agent as defined in the present disclosure for instance of the antibody, that may be mentioned include (Garnett M.C., et al., Advanced Drug Delivery Reviews 2001, 53, 171-216): (i) a ε-amino group (ε-NH2group) borne by the side chain of a lysine residue that is present at the surface of the binding agent as defined in the present disclosure for instance of the antibody; (ii) an α-amino group (α-NH2 group) of an N-terminal amino acid of a heavy chain or a light chain of the binding agent as defined in the present disclosure for instance of the antibody; (iii) the saccharide groups of the hinge region; (iv) a thiol (a -SH group) of a cysteine residue generated by reducing an intra-chain disulfide bond of the binding agent as defined in the present disclosure for instance of the antibody or a -SH group of an engineered cysteine residue of the binding agent as defined in the present disclosure for instance of the antibody; (v) an amide group (a -C(O)NH2group) borne by the side chains of a glutamine residue that is present at the surface of the binding agent as defined in the present disclosure for instance of the antibody; (vi) an aldehyde group (a -C(O)H group) introduced using formylglycine generating enzyme; and (vii) RCG2 group, optionally introduced by means of a modifying agent. According to a particular embodiment, in the compounds of formula (II), (II1) or (II2) as defined in the present disclosure, RCG2 is a reactive group of a cysteine engineered amino acid residue of an antibody. For instance, in the compounds of formula (II), (II1) or (II2) as defined in the present disclosure, the cysteine engineered amino acid residue is at least one position according to the numbering of the EU numbering index, selected from an interchain cysteine, 118, 152, 360, 274, 414 of the heavy chain constant (CH) domain, in particular the cysteine engineered amino acid residue is at position 360 of the heavy chain constant (CH) domain according to the numbering of the EU numbering index. More recently, other site-specific conjugation approaches have been considered, for instance the introduction of cysteines by mutation (Junutula J.R., et al., Nature Biotechnology 2008, 26, 925-932), the introduction of unnatural amino acids allowing other types of chemistry (Axup J.Y., et al., PNAS 2012, 109, 40, 16101-16106) or the conjugation on antibody glycans (Zhou Q., et al., Bioconjugate Chem. 2014, 25, 510-520). Use of cysteine bridging dibromomaleimides (Behrens C.R., et al., Mol. Pharmaceutics 2015, 3986-3998) and bis- sulfone reagents (Bryant P., et al., Mol. Pharmaceutics 2015, 1872-1879) in order to cross- link antibodies have also been described and could be applied to the present disclosure. Another approach for site-specific modifications of antibodies is based on enzymatic conjugation using for example bacterial transglutaminase (Jeger S., et al., Angew. Chem. Int. Ed. 2010, 49, 9995-9997; Strop P., et al., Chem. Biol. 2013, 20, 161-167) or formylglycine generating enzyme (Hudak J.E., et al., Angew. Chem. Int. Ed. 2012, 51, 4161-4165). For a review of site-specific conjugation strategies, see Agarwal P. and Bertozzi C.R., Bioconjugate Chem 2015, 26, 176-192. These conjugation technologies may also be applied to compounds / payloads of formula (I), (I1) or (I2) described in the present disclosure. It is also possible to chemically modify the binding agent as defined in the present disclosure for instance the antibody so as to introduce novel RCG2 reactive groups. Thus, it is well known to those skilled in the art how to modify a binding agent as defined in the present disclosure for instance an antibody with the aid of a modifying agent introducing for example activated disulfide, thiol, maleimido, haloacetamido, azido, alkyne or cycloalkyne groups (see especially WO2005 / 077090 page 14 and WO2011 / 001052). The modification makes it possible to improve the conjugation reaction and to use a wider variety of RCG1 groups, present on compound / payload of formula (I), (I1) or (I2). For instance, in the case where RCG1 is of the type (ii) above defined, that is to say one of the following reactive groups: a maleimido group; a substituted maleimido group I such group with R21 representing a hydrogen atom or a (C1-C6)alkyl group, such as a methyl group; Cl-; N3-; HO- ; HS-; an activated disulfide such activated C≡C such as a cyclooctyne moiety for instance a DBCO-amine ; a phenyloxadiazolyl methylsulfone group (PODS) hydroxylamine or a Pictet-Spengler reaction substrate such as , instance RCG1is N3-, a maleimido group , a substituted maleimido group

[0042] , it is possible to chemically modify the antibody using an adequate modifying agent or to introduce one or more unnatural amino acids so as to introduce the adequate RCG2 groups. For example: - when RCG1 represents a N-hydroxysuccinimidyl ester, RCG2 represents a -NH2 group; - when RCG1 represents a maleimido function, a haloacetamido function, a chorine atom or an activated disulfide function, RCG2 may be a -SH group; - when RCG1 represents a -N3 group, RCG2 may be a -C=CH function or an activated C=C function such as a cyclooctyne moiety; - when RCG1 represents a -OH group or -NH2group, RCG2 may be a carboxylic acid or amide function; - when RCG1 represents a -SH group, RCG2 may be a maleimido function, a haloacetamido function or an activated disulfide function; - when RCG1 represents a -C=CH function or an activated -C=C function, RCG2 may be a -N3 group; - when RCG1 represents a O-alkyl hydroxylamine function or a Pictet-Spengler reaction substrate, RCG2 may be an aldehyde or a ketone function. As indicated above, examples of G that may be mentioned include ; ; for instance, the left side of the G groups being linked to BA and the right side of the G groups being linked to L1. For instance, G represents the following groups: . • Synthesis of the modifying agents

[0043] Scheme 5 Step (i): coupling of dibenzocyclooctyne-amine to glutaric anhydride; Step (ii): activation of the carboxylic acid as an activated ester by treatment • with DSC in the presence of a base such as, for example, DIEA; or • with N-hydroxysulfosuccinimide sodium salt in the presence of a coupling reagent such as, for example, DCC; or • with 4-hydroxyphenyldimethylsulfonium methyl sulfate in the presence of a coupling reagent such as, for example, DIC; or • with 2,3,5,6-tetrafluoro-4-hydroxybenzenesulfonic acid sodium salt in the presence of a coupling reagent such as, for example, DIC. Scheme 5 depicted the synthesis starting with dibenzocyclooctyne-amine (CAS number [1255942-06-3]) but may also apply to other cyclooctyne-amines which are commercially available. It depicted the synthesis using glutaric anhydride but may also apply to succinic anhydride or alkyl diacids which are commercially available for n ranging from 3 to 10. Preparation of the compounds / conjugates of formula (II), (II1) and (II2): The compound / conjugates of formula (II), (II1) or (II2) or a pharmaceutically acceptable salt thereof of the present disclosure can be obtained via the process comprising at least the steps of: (i) placing in contact and leaving to react: - an, optionally buffered, aqueous solution of a binding agent as defined in the present disclosure for instance of an antibody Ab, comprising a reactive RCG2 group, optionally modified by means of a modifying agent, and - a solution of a compound / payload of formula (I), (I1) or (I2) as defined in the present disclosure, comprising a reactive RCG1 group, RCG1 groups of compound / payload of formula (I), (I1) or (I2) being reactive towards RCG2 groups of the binding agent as defined in the present disclosure for instance of the antibody to form the G groups by a covalent bond and forming compounds / conjugates of formula (II), (II1) or (II2). According to one variant for example, in step (ii) the compound / conjugate of formula (II), (II1) or (II2) from step (i) is separated from the unreacted compound / payload of formula (I), (I1) or (I2) from any aggregates formed, and / or any unreacted binding agent as defined in the present disclosure for instance any unreacted antibody. The function of the placing in contact is to react RCG1 groups and RCG2 groups in order to ensure attachment of the compound / payload of formula (I), (I1) or (I2) to the binding agent as defined in the present disclosure for instance to the antibody by formation of a covalent bond; such as: • when RCG1 represents a chlorine atom or a maleimido or haloacetamido group, the binding agent as defined in the present disclosure for instance the antibody may comprise thiol groups; • when RCG1 represents an azido group, the binding agent as defined in the present disclosure for instance the antibody may comprise a -C=CH moiety or an activated C≡C such as a cyclooctyne group; • when RCG1 represents a -NH2group, the reaction may take place on amide function of the antibody using an enzymatic catalysis, such as the amide groups borne by the side chains of glutamine (Gln) residues of a binding agent as defined in the present disclosure for instance an antibody. • when RCG1 represents a HC≡C- or an activated C≡C group such as a cyclooctyne moiety, the binding agent as defined in the present disclosure for instance the antibody may comprise azido groups. The term “aggregates” means associations that may form between two or more binding agents as defined in the present disclosure for instance two or more antibodies, the antibodies possibly having been modified by conjugation. Aggregates are liable to form under the influence of a wide variety of parameters such as a high concentration of binding agent as defined in the present disclosure for instance antibody in the solution, the pH of the solution, high shear forces, the number of grafted drugs and their hydrophobic nature, the temperature (see the references cited in the introduction of J. Membrane Sci. 2008, 318, 311–316), the influence of some of them, however, having not been clearly elucidated. In the case of proteins or antibodies, reference may be made to AAPS Journal, “Protein Aggregation and Bioprocessing” 2006, 8(3), E572-E579. The aggregate content may be determined via known techniques such as SEC (see in this respect Analytical Biochemistry 1993, 212 (2), 469-480). The aqueous solution of the binding agent as defined in the present disclosure for instance the antibody may be buffered with buffers for example, potassium phosphate or HEPES or a mixture of buffers such as buffers A, B, C, D and E described later. The buffer depends on the nature of the binding agent as defined in the present disclosure for instance the antibody. The compound / payload of formula (I), (I1) or (I2) is dissolved in a polar organic solvent such as DMSO or DMA. The reaction takes place at a temperature generally ranging from 20°C to 40°C. The reaction time may be ranging from 1 to 24 hours. The reaction between the binding agent as defined in the present disclosure for instance the antibody and the compound / payload of formula (I), (I1) or (I2) may be monitored by SEC with a refractometric and / or ultraviolet detector and / or HRMS in order to determine its degree of progress. If the degree of substitution is insufficient, the reaction can be left for longer and / or compound / payload of formula (I), (I1) or (I2) can be added. Reference may be made to the example section for further details regarding particular conditions. Particular embodiments are described in Examples 9 to 40. A person skilled in the art has at his disposal various chromatographic techniques for the separation of step (ii): the compound / conjugate of formula (II), (II1) or (II2) may be purified, for example, by steric exclusion chromatography (SEC), by adsorption chromatography (for instance ion exchange, IEC), by hydrophobic interaction chromatography (HIC), by affinity chromatography, by chromatography on mixed supports such as ceramic hydroxyapatite, or by HPLC. Purification by dialysis or diafiltration may also be used. After step (i) or (ii), the solution of the compound / conjugate of formula (II), (II1) or (II2) may undergo an ultrafiltration and / or diafiltration step (iii). After these steps, the compound / conjugate of formula (II), (II1) or (II2) in aqueous solution is thus obtained. The present disclosure also relates to compounds of formula (II), (II1) or (II2) that may be obtained via the process(es) in accordance with the present disclosure. As mentioned above, a “binding agent” represents a molecule with affinity for a biological target, such as a ligand, a protein, a polypeptide, an antibody such as a monoclonal antibody or a VHH antibody, a peptide, an oligonucleotide, an oligosaccharide for instance a targeting agent for instance a cell-binding agent. The function of the binding agent is to direct the biologically active compound, such as a TLR7 and / or 8 agonist compound towards the biological target. Cell-bin As mentioned above, cell binding agents may be of any kind presently known, or that become known and includes peptides and non-peptides. The cell binding agent may be any compound that can bind a cell, either in a specific or non-specific manner. Generally, these can be antibodies (especially monoclonal antibodies), lymphokines, hormones, growth factors, vitamins, nutrient-transport molecules (such as transferrin), or any other cell binding molecule or substance. More specific examples of cell binding agents that can be used include: (a) polyclonal antibodies; (b) monoclonal antibodies; (c) fragments of antibodies such as Fab, Fab1, and F(ab')2, Fv (Parham, J. Immunol. 131:2895-2902 (1983); Spring et al. J. Immunol. 113:470-478 (1974); Nisonoff et al. Arch. Biochem. Biophys. 89:230-244 (I960)); (d) interferons (e.g. alpha, beta, gamma); (e) lymphokines such as IL-2, IL-3, IL-4, IL-6; (f) hormones such as insulin, TRH (thyrotropin releasing hormone), MSH (melanocyte- stimulating hormone), steroid hormones, such as androgens and estrogens; (g) growth factors and colony-stimulating factors such as EGF, TGF-alpha, FGF, VEGF, G- CSF, M-CSF and GM-CSF (Burgess, Immunology Today 5:155-158 (1984)); or (h) transferrin (O'Keefe et al. J. Biol. Chem. 260:932-937 (1985)); and (i) vitamins, such as folate. According to a particular embodiment, the binding agent (also named BA in the present text) can be an antibody (also named Ab in the present text), for instance a monoclonal antibody or a VHH antibody. The antibody can be a monoclonal antibody selected from the group consisting of a murine, chimeric, a humanized and a human antibody. In one embodiment, the antibody is a monospecific antibody, i.e., an antibody specifically binding to one single target. Alternatively, it might be a multispecific antibody. In one embodiment, the antibody is an IgG antibody, for instance an IgG1, an IgG2, an IgG3 or an IgG4 antibody. The antibody according to the disclosure specifically binds to a target, thereby directing the compound / conjugate of formula (II), (II1) or (II2) towards said target. As used herein, “specifically binds” or “binds specifically to” or “binds to” or the like, means that an antibody or antigen-binding fragment thereof forms a complex with an antigen that is relatively stable under physiological conditions. Specific binding can be characterized by an equilibrium dissociation constant (KD) of at least about 1x10-8M or less (e.g., a smaller KD denotes a tighter binding). Methods for determining whether two molecules specifically bind are well known in the art and include, for example, equilibrium dialysis, surface plasmon resonance, and the like. As described herein, antibodies have been characterized, for example, by their specific binding to target and / or target antigen using surface plasmon resonance, e.g., BIACORE™. The target typically corresponds to a protein expressed at the cell surface, e.g. a protein expressed at the surface of tumor cells. In one embodiment, the target is the CEACAM5 receptor. The CEACAM5 receptor is a member of the carcinoembryonic antigen-related cell adhesion molecule (CEACAM) receptor family and is also referred to as “CEA cell adhesion molecule 5”, or “CD66e”. The antibody specifically binding to the CEACAM5 receptor might for instance correspond to one of the antibodies described in WO2014 / 079886 (US 9617345B2). In one embodiment, the target is the Programmed Cell Death Ligand 1 (PDL1). The Programmed Cell Death Ligand 1 is a is a trans-membrane protein that is considered to be a co-inhibitory factor of the immune response. The antibody specifically binding to PDL1 might for instance correspond to one of the antibodies described in WO2013 / 079174A1. The antibody may optionally be modified with a modifying agent so as to promote the attachment of the compound / payload of formula (I), (I1) or (I2) as previously described. The antibody may especially be monoclonal, polyclonal or multispecific. It may also be an antibody fragment. It may also be a murine, human, humanized or chimeric antibody. The antibodies used in the examples of the present disclosure are: • Tusamitamab (CAS [2349294-95-5]), an antibody against CEACAM5 receptor. The sequence of Tusamitamab (CAS [2349294-95-5]) is represented by SEQ ID NO: 88 (light chain of antibody Tusamitamab (CAS [2349294-95-5])) and by SEQ ID NO: 87 (heavy chain of antibody Tusamitamab (CAS [2349294-95-5])) following the procedure described in WO2014 / 079886 (US9617345B2). For the amino acid sequence of tusamitamab, it may also be referred to SEQ ID NO. 1 (light chain) and SEQ ID NO. 2 (heavy chain) disclosed herein after, • Avelumab_K76R-K100R, an antibody against PDL1. It corresponds to the antibody Avelumab (CAS [1537032-82-8]) in which Lys 76 and Lys 100 have been replaced by Arg. For the amino acid sequence of Avelumab_K76R-K100R, it may be referred to SEQ ID NO. 7 (light chain) and SEQ ID NO. 8 (heavy chain) disclosed herein after, • Avelumab_K360C, an antibody against PDL1. It corresponds to the antibody Avelumab (CAS [1537032-82-8]) in which Lys 360 has been replaced by Cys. For the amino acid sequence of Avelumab_K360C, it may be referred to SEQ ID NO. 5 (light chain) and SEQ ID NO. 6 (heavy chain) disclosed herein after, • Avelumab_LALA-K360C, an antibody against PDL1. It corresponds to the antibody Avelumab (CAS [1537032-82-8]) in which Lys 360 has been replaced by Cys and Leu 234 and Leu 235 have been replaced by Ala. For the amino acid sequence of Avelumab_LALA-K360C, it may be referred to SEQ ID NO.3 (light chain) and SEQ ID NO. 4 (heavy chain) disclosed herein after, • Anti-CEACAM5_hyb_769graft_VHg2-7_VLg2-2 also named anti- CEACAM5_769_VarB_VH7 / VL2, an antibody against CEACAM5 receptor. For the amino acid sequence of anti-CEACAM5_hyb_769graft_VHg2-7_VLg2-2, it may be referred to SEQ ID NO. 9 (light chain) and SEQ ID NO. 10 (heavy chain) disclosed herein after, • Anti-CEACAM5_p01_CEA-1_07_IgG1-dK, an antibody against CEACAM5 receptor. For the amino acid sequence of anti-CEACAM5_p01_CEA-1_07_IgG1- dK, it may be referred to SEQ ID NO. 11 (light chain) and SEQ ID NO. 12 (heavy chain) disclosed herein after, • Anti-CEACAM5_p01_CEA-1_07_IgG1_A118C_dK, an antibody against CEACAM5 receptor. It corresponds to the antibody anti-CEACAM5_p01_CEA- 1_07_IgG1-dK in which Ala 118 has been replaced by Cys. For the amino acid sequence of anti-CEACAM5_p01_CEA-1_07_IgG1_A118C_dK, it may be referred to SEQ ID NO. 13 (light chain) and SEQ ID NO. 14 (heavy chain) disclosed herein after, • Anti-CEACAM5_p01_CEA-1_07_IgG1_E152C_dK, an antibody against CEACAM5 receptor. It corresponds to the antibody anti-CEACAM5_p01_CEA- 1_07_IgG1-dK in which Glu 152 has been replaced by Cys. For the amino acid sequence of anti-CEACAM5_p01_CEA-1_07_IgG1_E152C_dK, it may be referred to SEQ ID NO. 15 (light chain) and SEQ ID NO. 16 (heavy chain) disclosed herein after, • Anti-CEACAM5_p01_CEA-1_07_IgG1_K360C_dK, an antibody against CEACAM5 receptor. It corresponds to the antibody anti-CEACAM5_p01_CEA- 1_07_IgG1-dK in which Lys 360 has been replaced by Cys. For the amino acid sequence of anti-CEACAM5_p01_CEA-1_07_IgG1_K360C_dK, it may be referred to SEQ ID NO. 17 (light chain) and SEQ ID NO. 18 (heavy chain) disclosed herein after, • Anti-CEACAM5_p01_CEA-1_07_IgG1_K414C_dK, an antibody against CEACAM5 receptor. It corresponds to the antibody anti-CEACAM5_p01_CEA- 1_07_IgG1-dK in which Lys 414 has been replaced by Cys. For the amino acid sequence of anti-CEACAM5_p01_CEA-1_07_IgG1_K414C_dK, it may be referred to SEQ ID NO. 19 (light chain) and SEQ ID NO. 20 (heavy chain) disclosed herein after, • Anti-CEACAM5_p07_CEA-3_50_IgG1_VH1_A1118C_dK, an antibody against CEACAM5 receptor. It corresponds to the antibody anti-CEACAM5_p07_CEA- 3_50_IgG1_VH1_dK in which Ala 118 has been replaced by Cys. For the amino acid sequence of anti-CEACAM5_p07_CEA-3_50_IgG1_VH1_A118C_dK, it may be referred to SEQ ID NO. 21 (light chain) and SEQ ID NO. 22 (heavy chain) disclosed herein after, • Anti-CEACAM5_p07_CEA-3_50_IgG1_VH1_K360C_dK, an antibody against CEACAM5 receptor. It corresponds to the antibody anti-CEACAM5_p07_CEA- 3_50_IgG1_VH1_dK in which Lys 360 has been replaced by Cys. For the amino acid sequence of anti-CEACAM5_p07_CEA-3_50_IgG1_VH1_K360C_dK, it may be referred to SEQ ID NO. 23 (light chain) and SEQ ID NO. 24 (heavy chain) disclosed herein after, • Anti-CEACAM5_p07_CEA-3_50_IgG1_VH1_K414C_dK, an antibody against CEACAM5 receptor. It corresponds to the antibody anti-CEACAM5_p07_CEA- 3_50_IgG1_VH1_dK in which Lys 414 has been replaced by Cys. For the amino acid sequence of anti-CEACAM5_p07_CEA-3_50_IgG1_VH1_K414C_dK, it may be referred to SEQ ID NO. 25 (light chain) and SEQ ID NO. 26 (heavy chain) disclosed herein after, • Anti-CEACAM5_p01_CEA-1_07_IgG1_A118C_K360C_dK, an antibody against CEACAM5 receptor. It corresponds to the antibody anti-CEACAM5_p01_CEA- 1_07_IgG1-dK in which Ala 118 and Lys 360 have been replaced by Cys. For the amino acid sequence of anti-CEACAM5_p01_CEA-1_07_IgG1_A118C_K360C_ dK, it may be referred to SEQ ID NO. 27 (light chain) and SEQ ID NO. 28 (heavy chain) disclosed herein after, • Anti-CEACAM5_p01_CEA-1_07_IgG1_E152C_K360C_dK, an antibody against CEACAM5 receptor. It corresponds to the antibody anti-CEACAM5_p01_CEA- 1_07_IgG1-dK in which Glu 152 and Lys 360 have been replaced by Cys. For the amino acid sequence of anti-CEACAM5_p01_CEA-1_07_IgG1_E152C_K360C_ dK, it may be referred to SEQ ID NO. 29 (light chain) and SEQ ID NO. 30 (heavy chain) disclosed herein after, • Anti-CEACAM5_p01_CEA-1_07_IgG1_K274C_K414C_dK, an antibody against CEACAM5 receptor. It corresponds to the antibody anti-CEACAM5_p01_CEA- 1_07_IgG1-dK in which Lys 274 and Lys 414 have been replaced by Cys. For the amino acid sequence of Anti-CEACAM5_p01_CEA-1_07_IgG1_K274C_K414C_ dK, it may be referred to SEQ ID NO. 31 (light chain) and SEQ ID NO. 32 (heavy chain) disclosed herein after, • Anti-CEACAM5_p07_CEA-3_50_IgG1_VH1_A118C_K360C_dK, an antibody against CEACAM5 receptor. It corresponds to the antibody anti- CEACAM5_p07_CEA-3_50_IgG1_VH1_dK in which Ala 118 and Lys 360 have been replaced by Cys. For the amino acid sequence of anti-CEACAM5_p07_CEA- 3_50_IgG1_VH1_A118C_K360C_dK, it may be referred to SEQ ID NO. 33 (light chain) and SEQ ID NO. 34 (heavy chain) disclosed herein after, • Anti-CEACAM5_p07_CEA-3_50_IgG1_VH1_K274C_K414C_dK, an antibody against CEACAM5 receptor. It corresponds to the antibody anti- CEACAM5_p07_CEA-3_50_IgG1_VH1_dK in which Lys 274 and Lys 414 have been replaced by Cys. For the amino acid sequence of anti-CEACAM5_p07_CEA- 3_50_IgG1_VH1_K274C_K414C_dK, it may be referred to SEQ ID NO. 35 (light chain) and SEQ ID NO. 36 (heavy chain) disclosed herein after. Compound / conjugate of formula (II), (II1) or (II2) (Conjugate): A compound / conjugate of formula (II), (II1) or (II2) generally comprises from about 1 to 10 compound / payload of formula (I), (I1) or (I2) covalently attached to the binding agent as defined in the present disclosure for instance the antibody (this is the degree of grafting or “drug-to-antibody ratio” or “DAR”). This number varies as a function of the nature of the binding agent as defined in the present disclosure for instance the antibody and of the compound / payload of formula (I), (I1) or (I2) and also of the operating conditions used in the conjugation process (for example the number of equivalents of compound / payload of formula (I), (I1) or (I2) relative to the binding agent as defined in the present disclosure for instance the antibody, the reaction time, the nature of the solvent and of any cosolvent). Placing of the binding agent as defined in the present disclosure for instance the antibody and the compound / payload of formula (I), (I1) or (I2) in contact leads to a mixture comprising several compounds / conjugates of formula (II), (II1) or (II2) that are individually distinguished from each other by different DARs; optionally the unreacted binding agent as defined in the present disclosure for instance the unreacted antibody; optionally aggregates. The DAR that is determined on the final solution thus corresponds to an average DAR. The DAR may be calculated from the deconvolution of the SEC-HRMS spectrum of the compound / conjugate of formula (II), (II1) or (II2). The DAR (HRMS) is for example greater than 0.5, for instance ranging from 1 to 10, such as ranging from 2 to 5. The compound / conjugate of formula (II), (II1) or (II2) may be used as an anticancer agent. Owing to the presence of the binding agent as defined in the present disclosure for instance the antibody, the compound / conjugate of formula (II), (II1) or (II2) is made highly selective towards tumor cells rather than healthy cells. This makes it possible to direct the compound / conjugate of formula (II), (II1) or (II2) in an environment similar thereto or directly therein. It is possible to treat solid or liquid cancers. The compound / conjugate of formula (II), (II1) or (II2) may be used alone or in combination with at least one other anticancer agent. The compound / conjugate of formula (II), (II1) or (II2) is formulated in the form of a buffered aqueous solution at a concentration generally ranging from 1 to 10 mg / mL. This solutionmay be injected in perfusion form per se or may be re-diluted to form a perfusion solution. The examples which follow describe the preparation of some compounds of formulae (I), (I1) or (I2) and (II), (II1) or (II2) in accordance with the disclosure. The numbers of the compounds exemplified below match those given above. All reactions are performed under inert atmosphere, unless otherwise stated. In the following examples, when the source of the starting products is not specified, it should be understood that said products are known compounds. EXAMPLES The examples which follow describe the preparation of certain compounds in accordance with the disclosure. These examples are not limitative, and merely illustrate the present disclosure. Materials and methods The progress of the synthetic reactions is monitored by TLC. The plates are made of glass and are coated with Merck 60 F254 silica gel. After elution, the plates are observed under ultraviolet light at 254 nm. The microwave reactions were performed using a Biotage Initiator 8 EXP microwave machine. The products were purified, when necessary, on a Biotage Isolera chromatograph or a Spot 2 chromatograph from Merck. The columns used are Merck 15-40 μm silica columns (2.5 g to 800 g). – Mass Spectrometry (LCMS) Method M: the spectra were acquired on an Agilent 1200 & 6110B; ionization: electrospray in positive mode (ES+). • Kinetex C1850 x 2.1 mm, 5 µm • Solvents: A: H2O+0.037 % (v / v) TFA B: ACN+0.018 % (v / v) TFA • Column temperature: 40°C • Flow rate: 1 mL / min • Gradient (5 min): from 5 to 95% B in 3 min; 1 min: 95% B; 1.50 min: 5% B Method M1: the spectra were acquired on a Waters UPLC-SQD; ionization: electrospray in positive and / or negative mode (ES+ / -). • Column ACQUITY CSH C18 – 1.7 µm – 2.1 x 50 mm • Solvents: A: H2O (0.1 % formic acid) B: CH3CN (0.1 % formic acid) • Column temperature: 50°C • Flow rate: 0.90 mL / min • Gradient (2.5 min): from 5 to 100% B in 1.8 min; 2.4 min: 100% B; 2.45 min: 5% B Method M2: the spectra were acquired on a Waters XEVO Q TOF; ionization: electrospray in positive mode (ES+). • Column ACQUITY CSH C18 – 1.7 µm – 2.1 x 100 mm • Solvents: A: H2O (0.1 % formic acid) B: CH3CN (0.1 % formic acid) • Column temperature: 45°C • Flow rate: 0.50 mL / min • Gradient (3 min): 0 to 0.3 min, 5% of B - 0.3 to 4 min, 5 to 100% of B - 4 to 4.6 min, 100% of B - 4.6 to 5.3 min, 5% of B Method N: the spectra were acquired on a Waters UPLC-SQD2; ionization: electrospray in positive and / or negative mode (ES+ / -). • Column ACQUITY CSH C18 - 1.7 µm - 2.1 x 50 mm • Solvents: A: H2O (0.1% formic acid) B: CH3CN (0.1% formic acid) • Column temperature: 60°C • Flow rate: 1 mL / min • Gradient (2.5 min): from 3 to 100% B in 2.1 min; 2.45 min: 100% B; 2.50 min: 3% B Method N1: the spectra were acquired on a Waters UPLC-SQD2; ionization: electrospray in positive and / or negative mode (ES+ / -). • Column ACQUITY CSH C18 - 1.7 µm - 2.1 x 50 mm • Solvents: A: H2O (0.1% formic acid) B: CH3CN (0.1% formic acid) • Column temperature: 60°C • Flow rate: 1 mL / min • Gradient (3 min): 0.1 min: 3% B; from 3 to 97% B in 2 min; 2.45 min: 97% B; 2.50 min: 3% B; 3 min: 3% B Method N2: the spectra were acquired on a Waters UPLC-SQD2; ionization: electrospray in positive and / or negative mode (ES+ / -). • Column ACQUITY CSH C18 - 1.7 µm - 2.1 x 30 mm • Solvents: A: H2O (0.1% formic acid) B: CH3CN (0.1% formic acid) • Column temperature: 50°C • Flow rate: 0.7 mL / min • Gradient (6 min): 0.3 min: 3% B; from 3 to 97% B in 4.7 min; 5 min: 100% B; 6 min: 3% B Method N3: the spectra were acquired on a Waters UPLC-SQD2; ionization: electrospray in positive and / or negative mode (ES+ / -). • Column ACQUITY CSH C18 - 1.7 µm - 2.1 x 30 mm • Solvents: A: H2O (0.1% formic acid) B: CH3CN (0.1% formic acid) • Column temperature: 50°C • Flow rate: 0.8 mL / min Gradient (5 min): 0.2 min: 5% B; from 5 to 98% B in 3.4 min; 3.7 min: 98% B; 4.10 min: 5% B; 5 min: 5% B Method N4: the spectra were acquired on a Waters UPLC-SQD; ionization: electrospray in positive and / or negative mode (ES+ / -). • Column ACQUITY CORTECS C18+ - 1,6 µm - 2,1 x 50 mm • Solvents: A: H2O (0.1% formic acid) B: CH3CN (0.1% formic acid) • Column temperature: 50°C • Flow rate: 1 mL / min Gradient (2 min): 0 to 1.5 min 5 to 99% of B - 1.5 to 1.9 min 99% of B - 1.9 to 1.95 min 99 to 5% of B - 1.95 to 2.15 Method N5: the spectra were acquired on a Waters UPLC-SQD2; ionization: electrospray in positive and / or negative mode (ES+ / -). • Column ACQUITY CSH C18 - 1.7 µm - 2.1 x 30 mm • Solvents: A: H2O (0.1% formic acid) B: CH3CN (0.1% formic acid) • Column temperature: 50°C • Flow rate: 0.7 mL / min Gradient (4 min): 0.18 min: 5% B; from 5 to 99% B in 3.02 min; 3.4 min: 99% B; 4 min: 5% B Method O: the spectra were acquired on a WATERS QUATTRO PREMIER; ionization: electrospray in positive and / or negative mode (ES+ / -) • Column ACQUITY MSS T3 - 1.8 µm - 2.1 x 50 mm • Solvents: A: H2O (0.1% formic acid) B: CH3CN (0.1% formic acid) • Column temperature: 55°C • Flow rate: 0.9 mL / min • Gradient (3.7 min): de 5 to 100% B in 3 min; 3.1 min: 5% B1H Nuclear Magnetic Resonance (NMR) The1H NMR spectra were recorded on a Brüker Avance and / or Varian G spectrometer (300 MHz, 400 MHz, 500 MHz, or 600 MHz) in deuterated DMSO. The chemical shifts are expressed in units (ppm) using tetramethyl silane (TMS) as internal reference. For the interpretation of the spectra, the following abbreviations were used: s = singlet, d = doublet, t = triplet, q = quartet, quint = quintet, sext = sextet, dd = doubled doublet, ddd = doublet of doubled doublets, m = multiplet, ax. = axial, equat. = equatorial. Reverse phase chromatography – high resolution mass spectrometry (RP-HRMS) The analyses were performed on an UPLC-XEVO-G2-XS-QTOF (Waters), an UPLC- XEVO-G2-S-QTOF (Waters) or an UPLC-XEVO-G3-QTOF (Waters). The reverse phase chromatographic analysis was performed using an Agilent BioHPLC PLR 5 µm column (2.1 x 50 mm) at 80°C with a flow rate of 0.5 mL / min and the following elution gradient: 5% B at 1 min, 50% B at 4 min, 50% B at 5 min, 5% B at 6 min, 5% B at 7 min (solvents: A: H2O (0.1% formic acid); B: CH3CN (0.1% formic acid)). The mass spectrometry was performed with electrospray ionization in positive mode (ES+). The mass spectra were deconvoluted with the Waters MaxEnt1 software. The observed molecular masses correspond respectively to the mass of the naked antibody, if present, and to the conjugation of 1 (D1), 2 (D2),… n (Dn) drugs on the antibody. When needed, preliminary ADC reduction was performed using the following conditions: ADC was treated with 1 / 10 (in volume) of a 0.5M TCEP solution in water and left for 30 min at RT before RP-HRMS analysis. In this case, the observed molecular masses correspond respectively to the mass of the naked light and heavy chains (LC and HC), if present, and to the conjugation of 1 (LC1, HC1), 2 (LC2, HC2)… n (LCn, HCn) drugs on the antibody. Analytical Size Exclusion Chromatography (SEC) The analysis was performed on a Hitachi Labchrom or a Thermo Vanquish LC system equipped with a photodiode array detector and a Tosoh Bioscience TSK-GEL SuperSW 4 μm (4.6 × 150 mm) column with a flow rate of 0.2 mL / min or a Tosoh Bioscience TSKgel G3000 SWXL 5 μm (7.8 × 300 mm) column with a flow rate of 0.5 mL / min and an isocratic elution of 15 minutes with a pH 7 buffer containing 0.2 M of KCl, 0.052 M of KH2PO4, 0.107 M of K2HPO4 and 20 % by volume of isopropanol. Buffers • DPBS: Na2HPO4 (8.10 mM), KH2PO4 (1.47 mM), NaCl (136.9 mM), KCl (2.67 mM) • Buffer A (pH 5.5): sodium acetate (20 mM), 10% (w / v) sucrose • Buffer B (pH 5.5): sodium acetate (20 mM), 5% (w / v) sucrose, 0.01% PS80 • Buffer C (pH 7.4): NaPi (10 mM), NaCl (140 mM) • Buffer D (pH 5.5): histidine (10 mM), 8% (w / v) sucrose • Buffer E (pH 6.5): histidine (10 mM), 10% (w / v) sucrose General methods used for the preparation of compounds / conjugates of formula (II), (II1) or (II2) (M1 to M4) • General method used for the preparation of mAb-DBCO using NHS ester (M1) M1: To a solution of antibody in an aqueous buffer eventually diluted with DPBS was added 1 N HEPES (composition varying from 94:6 to 100:0, in other terms from 0% to 6% HEPES (v / v)). The solution was treated with an excess (4 to 10 equivalents) of a solution at 2 to 20 mM of NHS ester DBCO linker in DMA or DMSO such that the final antibody concentration is 1-11 mg / mL and the percentage of DMA or DMSO in the aqueous buffer is 1-20%. After stirring at RT for 45 min to 3 hours, the mixture was analyzed by SEC HPLC and / or HRMS so as to determine the linker-to-antibody ratio (LAR) on the population of monomeric antibodies. If the LAR was found insufficient, the mixture was treated with a further excess of linker solution in DMA or DMSO for up to 2 additional hours at RT under stirring. • General method used for the preparation of compounds / conjugates of formula (II), (II1) or (II2) (M2 & M3) M2: A solution of mAb-DBCO in an aqueous buffer containing 1-20% DMA or DMSO (eventually diluted with DPBS) was treated with an excess (6 to 12 equivalents) of a solution at 10 to 20 mM of azido payload in DMA or DMSO such that the final antibody concentration is 1-4 mg / mL and the percentage of DMA or DMSO in the aqueous buffer is 2-20%. After overnight stirring at RT, the reaction mixture was analyzed by RP-HRMS to determine the DAR on the population of monomeric antibodies. The mixture was eventually concentrated by ultrafiltration with ultrafiltration spin column (Vivaspin®, PES membrane 50K, Sartorius) with DPBS buffer containing 20% of DMA. The mixture was then purified by gel filtration using a SuperdexTM200 pg matrix (HiLoad® 16 / 60 or 26 / 60 desalting column, GE Healthcare) pre-equilibrated in DPBS buffer containing up to 10-20 % of DMA. The fractions containing the monomeric conjugated antibody were pooled and eventually concentrated by ultrafiltration on spin columns (Vivaspin®: PES membrane 50K, Sartorius or Amicon® Ultra: Ultracel membrane, 50K, Millipore) to reach a concentration between 2 and 5 mg / mL. In some cases, the conjugate was formulated by gel filtration using a SephadexTMG25 matrix (NAP® or HitrapTMdesalting columns, GE Healthcare) pre- equilibrated with the final aqueous buffer A, buffer D or buffer E. The conjugate was finally sterile filtered (Millex®-SV 0.22µm, PVDF, Durapore®, Millipore). then assayed by UV spectrometry or SEC HPLC so as to measure the conjugate concentration, by SEC HPLC so as to determine the monomeric purity and by RP-HRMS so as to determine the DAR from the deconvolution of the mass spectrum of the conjugate. M3: A solution of mAb-DBCO in an aqueous buffer containing 1-20% DMA or DMSO (eventually diluted with DPBS) was treated with an excess (6 to 12 equivalents) of a solution at 10 to 20 mM of azido payload in DMA or DMSO such that the final antibody concentration is 1-4 mg / mL and the percentage of DMA or DMSO in the aqueous buffer is 2-20%.After overnight stirring at RT, the mixture was analyzed by RP-HRMS so as to determine the DAR on the population of monomeric antibodies. The mixture was purified by diafiltration with ultrafiltration spin columns (Vivaspin®: PES membrane 50K, Sartorius or Amicon® Ultra: Ultracel membrane, 50K, Millipore) then formulated using SephadexTMG25 matrix (HitrapTMdesalting GE Healthcare) pre-equilibrated with the final aqueous buffer A, buffer D or buffer E. Depending on the residual free drug content as assessed by HRMS, additional purification by diafiltration with final buffer was performed. The conjugate was finally sterile filtered (Millex®-SV 0.22 µm (PVDF, Durapore, Millipore)). The final conjugate was assayed by UV spectrometry or SEC HPLC to measure the conjugate concentration, by SEC-HPLC so as to determine the monomeric purity and by RP- HRMS to determine the DAR from the deconvolution of the mass spectrum of the conjugate. • General method used for the preparation of compounds / conjugates of formula (II), (II1) or (II2) using thiomAbs (M4) M4a: To a solution of thiomAb at 1-11 mg / mL in DPBS was added DTT (64 equiv of a 100- 300 mM solution in H2O or DPBS). The mixture was stirred at 37°C during 45 min to 1 h and then purified by gel filtration using a SephadexTMG25 matrix (NAP® or HiprepTM26 / 10 desalting columns, GE Healthcare) pre-equilibrated with DPBS buffer. To the solution of reduced thiomAb was added DHAA (14-15 equiv of a 25-100 mM solution in DPBS) and the reaction mixture was stirred at RT for 3 hours. M4b: after addition of DMA (10-20% v / v), the mixture was treated with an excess of maleimido compound (1.5 to 2 equiv per uncapped thiols of a 10 to 20 mM solution in DMA) such that the final antibody concentration is 1-4 mg / mL and the percentage of DMA in the aqueous buffer is ~10-20%. After overnight stirring at RT, the mixture was analyzed by RP- HRMS so as to determine the DAR on the population of monomeric antibodies. The mixture was concentrated by diafiltration with ultrafiltration spin columns (Vivaspin®: PES membrane 50K, Sartorius or Amicon® Ultra: Ultracel membrane, 50K, Millipore) before or after purification by gel filtration using a Superdex 200 pg matrix (HiLoad® 16 / 60 or 26 / 60 desalting column, GE Healthcare) pre-equilibrated in aqueous buffer such as DPBS containing 5 to 20 % of an organic solvent such as DMA or EtOH and then formulated by gel filtration using a SephadexTMG25 matrix (NAP® or HiprepTM26 / 10 desalting columns, GE Healthcare) pre-equilibrated with the final aqueous buffer A, buffer D or buffer E. Depending on the residual free drug content as assessed by HRMS, additional purification by diafiltration with final buffer was performed. The conjugate was finally sterile filtered (Millex®-SV 0.22 µm, PVDF, Durapore, Millipore). The conjugate was assayed by UV spectrometry or SEC HPLC so as to measure the conjugate concentration, by SEC-HPLC so as to determine the monomeric purity and by RP-HRMS so as to determine the DAR from the deconvolution of the mass spectrum of the conjugate. Preparation A) Preparation of TLR agonists All the following compounds were synthesized according to the protocols described below. Synthesis of intermediates Preparation 1: Intermediate (A) 2-butyl-1H-imidazole-4,5-dicarbonitrile A suspension of (Z)-2,3-diaminobut-2-enenitrile (45.0 g, 416 mmol) and 1,1,1- trimethoxypentane (67.5 g, 416 mmol) in MeCN (90 mL) was stirred in an oil bath and it was kept at 85°C for 6 h. The reaction mixture was then concentrated by evaporation under reduced pressure. The whole of this compound was dissolved in xylene (90 mL), and the resulting solution was stirred in an oil bath kept at 150°C for 8 h. The mixture was concentrated to give a residue, which was filtered, and washed with methylbenzene. Then the filter cake was dried to give the expected product. Intermediate (A) (63.0 g, 87% yield) was used in the next step without any purification.1H NMR (400 MHz, δ in ppm, CDCl3): 2.82 (t, J=7.6 Hz, 15.2 Hz ,2H); 1.72-1.80 (m, 2H); 1.36-1.45 (m, 2H); 0.93-0.97 (m, 3H) MS Method M: tR=1.019 min, m / z 175.1 (M+H)+Preparation 2: Intermediate (B) 2-butyl-1H-imidazole-4,5-dicarboxylic acid A solution of intermediate (A) (63.0 g, 362 mmol) in H2SO4 (284 mL) and H2O (126 mL) was stirred at 100°C for 8 h. By TLC one major new spot with lower polarity was observed. The pH of the solution was adjusted to 9-10 using 10% sodium hydroxide solution. The mixture was filtered, and the filter cake was concentrated to give the expected product which was used into the next step without further purification. Intermediate (B) (76.5 g, 99.7% yield) was obtained as a black brown solid.1H NMR (400 MHz, δ in ppm, DMSO-d6): 2.59 (t, J=7.6 Hz, 2H); 1.57-1.63 (m, 2H); 1.19- 1.28 (m, 2H); 1.27-1.33 (m, 2H); 0.86 (t, J=7.2 Hz, 14.8 Hz ,2H) MS Method M: tR=1.163 min, m / z 213.1 (M+H)+. Preparation 3: Intermediate (C) dimethyl 2-butyl-1H-imidazole-4,5-dicarboxylate To a mixture of intermediate (B) (76.5 g, 361 mmol) in MeOH (230 mL) was added SOCl2 (214 g, 1.80 mol, 131 mL) slowly and degassed and purged with N2 for 3 times, and then the mixture was stirred at 40-45°C for 12 h under N2atmosphere. The mixture was cooled and then poured slowly to chilled water (500 mL). It was neutralized by the addition of 10 % sodium hydroxide solution. Then the mixture was extracted with EtOAc (3 x 500 mL). The combined organic layers were washed with brine (1.00 L), dried over Na2SO4, filtered and concentrated under reduced pressure to give a residue. The crude product was used into the next step without further purification. Intermediate (C) (81.0 g, 93.5% yield) was obtained as a black brown solid.1H NMR (400 MHz, δ in ppm, DMSO-d6): 3.87 (s, 6H); 2.77 (t, J=8.0 Hz, 2H); 1.68-1.76 (m, 2H); 1.30-1.40 (m, 2H); 0.90 (t, J=7.6 Hz, 3H) Preparation 4: Intermediate (D) 2-butyl-5,6-dihydro-1H-imidazo[4,5-d]pyridazine-4,7- dione

[0044] A mixture of intermediate (C) (81.0 g, 337 mmol), NH2NH2.H2O (51.7 g, 1.01 mol, 50.2 mL, 98.0 % purity) in MeOH (243 mL) was degassed and purged with N2for 3 times, and then the mixture was stirred at 60°C for 1 h under N2atmosphere. The reaction mixture was filtered and washed with methanol. This material was suspended in water (1.00 L), heated to 85°C, and then rendered acidic by addition of conc. HCl (100 mL). After stirring for 12 h at 85°C, the mixture was cooled and the white product filtered with suction and washed with water. The crude product was used into the next step without further purification. Intermediate (D) (49.5 g, 70.5% yield) was obtained as an off-white solid. Preparation 5: Intermediate (E) 2-butyl-4,7-dichloro-1H-imidazo[4,5-d]pyridazine To a cooled solution of intermediate (D) (49.5 g, 238 mmol) in POCl3 (248 mL) was added N,N-dimethyl aniline (50 mL) and the reaction mixture was stirred at 110°C for 90 min. The reaction mixture was concentrated under reduced pressure to give a residue. The residue was poured into cold water (2.00 L) and adjusted pH to 7 with solid sodium bicarbonate and extracted with EtOAc (2 x 1 L). The combined organic layers were washed with brine (500 mL), dried over Na2SO4, filtered and concentrated under reduced pressure to give a residue. The residue in MTBE (200 mL) was stirred for 2 h. The suspension was filtered, and the filter cake was collected. Intermediate (E) (54.5 g, 92% yield) was obtained as a yellow solid.1H NMR (400 MHz, δ in ppm, CDCl3): 3.18 (t, J=7.6 Hz, 2H); 1.90-1.97 (m, 2H); 1.40-1.49 (m, 1H); 0.92 (t, J=7.2 Hz, 3H) MS Method M: tR= 2.161 min, m / z 245.0 (M+H)+. Preparation 6: Intermediate (L) 2-butyl-7-chloro-N,N-bis(2,4-dimethoxybenzyl)-1H- imidazo[4,5-d]pyridazin-4-amine To a solution of intermediate (E) (15 g, 61.20 mmol) in n-butanol (150 mL) was added DIPEA (107 mL, 612.63 mmol) and bis(2,4-dimethoxybenzyl)amine (7 g, 22.1 mmol). The reaction mixture was refluxed during 1 h. A further 5 g (15.8 mmol) of bis(2,4- dimethoxybenzyl)amine were added and the heating was continued for 1 h. This operation was repeated twice again (2 x 5 g, 31.5 mmol). The resulting mixture was heated overnight. After cooling to room temperature, the reaction mixture was concentrated under reduced pressure to remove most of n-butanol. The residue was diluted with DCM (500 mL), then washed with H2O (250 mL), brine (200 mL), dried over anhydrous MgSO4, filtered and the filtrate was concentrated under reduced pressure to give 38.8 g of crude product. The residue was purified by chromatography on a Merck cartridge (800 g of 15-40 μm silica) using as eluent DCM / acetone 96 / 4 to 90 / 10 to give intermediate (L) (12 g, 37% yield) as a pale- yellow solid.1H NMR (400MHz, δ in ppm, DMSO-d6): 0.85 (t, J=7.4 Hz, 3 H); 1.28 (m, 2 H); 1.68 (m, 2 H); 2.82 (t, J=7.6 Hz, 2 H); 3.72 (s, 12 H); 5.07 (s broad, 4 H); 6.39 (dd, J=2.4 & 8.4 Hz, 2 H); 6.54 (d, J=2.4 Hz, 2 H); 6.95 (d, J=8.4 Hz, 2 H); 13.35 (s broad, 1 H) MS method N: tR(min): 1.59; [M+H]+526 Preparation 7: Intermediate (M) 2-butyl-N,N-bis(2,4-dimethoxybenzyl)-7-isopropoxy- 1H-imidazo[4,5-d]pyridazin-4-amine. To a suspension of intermediate (L) (4 g, 7.60 mmol) in dioxane (30 mL) was added sodium isopropoxide (3.74 g, 45.62 mmol) and 2-propanol (30 mL, 1.05 mol). The mixture was heated at 170°C under 18 bars for 7 h. The reaction mixture was cooled and filtered, and the cake was washed with EtOAc (100 mL). The filtrate was concentrated under reduced pressure. The crude product was dissolved with EtOAc (150 mL) then washed with H2O (2 x 75 mL), brine (75 mL), dried over anhydrous MgSO4, filtered and the filtrate was concentrated under reduced pressure to give 4.37 g of product. The residue was purified by chromatography on a Merck cartridge (200 g of 15-40 μm silica) with an EtOAc / Heptane (55 / 45) elution. Intermediate (M) (2.11 g, 50% yield) was obtained as a white solid.1H NMR (400MHz, δ in ppm , DMSO-d6): 0.84 (t, J=7.4 Hz, 3 H); 1.26 (m, 2 H); 1.37 (d, J=6.2 Hz, 6 H); 1.66 (m, 2 H); 2.77 (t, J=7.6 Hz, 2 H); 3.70 (s, 6 H); 3.71 (s, 6 H); 5.00 (s broad, 4 H); 5.41 (sept, J=6.2 Hz, 1 H); 6.38 (dd, J=2.4 & 8.4 Hz, 2 H); 6.52 (d, J=2.4 Hz, 2 H); 6.94 (d, J=8.4 Hz, 2 H); 13.01 (s broad, 1 H) MS method N: tR (min): 1.58; [M+H]+550 Preparation 8: Intermediate (N) 7-chloro-N,N-bis(2,4-dimethoxybenzyl)-1H- imidazo[4,5-d]pyridazin-4-amine

[0045] To a 25 mL round bottom flask equipped with a magnetic stir and a reflux condenser, were added commercially available 4,7-dichloro-1H-imidazo[4,5-d]pyridazine (3 g, 15.87 mmol), n-butanol (30 mL) and DIPEA (27.79 mL, 158.73 mmol), resulting in a homogeneous solution. Bis(2,4-dimethoxybenzyl)amine (1.45 g, 4.48 mmol) was then added and the brown reaction mixture was heated at reflux for 1 h. 3 other portions of bis(2,4- dimethoxybenzyl)amine were added every hour ( t0 + 2 h: 1.5 g, 4.63 mmol; t0 + 3 h: 1.5 g, 4.63 mmol and t0 + 4 h: 1.09 g, 3.37 mmol). The mixture was heated at reflux for 92 h. It was cooled to rt and evaporated under vacuum to dryness. The remaining oil was dissolved in EtOAc (400 mL), transferred to a separating funnel and washed with water (3 x 100 mL). The aqueous phase was extracted with 100 mL EtOAc. The combined organic layer was washed with brine, dried over MgSO4, filtered and evaporated to dryness, to give 9.06 g of crude product. The crude material was purified by chromatography on a Merck cartridge (600 g of 15-40 μm silica) with CHCl3 / MeOH (97 / 3) elution, to afford 1.79 g (24% yield) of expected intermediate (N) as a yellow solid.1H NMR (400 MHz, δ in ppm, DMSO-d6): 3.72 (s, 12 H); 5.07 (br s, 4 H); 6.40 (dd, J=8, 3 Hz, 2 H); 6.54 (d, J=3 Hz, 2 H); 6.95 (d, J=8 Hz, 2 H); 8.40 (s, 1 H); 13.74 (br s, 1 H) MS method N: tR (min): 1.37, [M+H]+470 Preparation 9: Intermediate (R) N,N-bis(2,4-dimethoxybenzyl)-7-isopropoxy-1H- imidazo[4,5-d]pyridazin-4-amine

[0046] To a round bottom flask (50 mL), were added 7-chloro-N,N-bis(2,4-dimethoxybenzyl)-1H- imidazo[4,5-d]pyridazin-4-amine, intermediate (N) (1.44 g, 3.06 mmol), dioxane (16 mL) and isopropanol (16 mL). The resulting solution was transferred equally into 2 microwave tubes of 10-20 mL capacity, to each was added sodium isopropoxide (755 mg, 9.2 mmol). Both tubes were heated at 170°C for 8 h. The reaction mixtures were combined and diluted in EtOAc (100 mL). The organic solution was washed with water (50 mL), the aqueous phase was extracted with EtOAc (3 x 10 mL). The combined organic layer was washed with brine, dried over MgSO4, filtered and evaporated to dryness, to give 1.38 g of crude product, which was purified by chromatography on a Merck cartridge (150 g of 15-40 μm silica) with DCM / MeOH (99 / 1 to 98 / 2) elution, to afford 0.763 g (50% yield) of expected intermediate (R) as a white foam.1H NMR (400 MHz, δ in ppm, DMSO-d6):1.38 (d, J=6.2 Hz, 6 H); 3.71 (s, 12 H); 5.02 (br s, 4 H); 5.41 (m, 1 H); 6.40 (dd, J=8.4, 2.4 Hz, 2 H); 6.53 (d, J=2.4 Hz, 2 H); 6.95 (d, J=8.4 Hz, 2 H); 8.21 (br s, 1 H); 13.30-13.60 (br s, 1H) MS method N: tR(min): 1.29, [M+H]+494 Preparation 10: Intermediate (S) 2-butyl-N-[(2,4-dimethoxyphenyl)methyl]-4- isopropoxy-3H-imidazo[4,5-d]pyridazin-7-amine Step 1: 2-butyl-4-chloro-7-isopropoxy-1H-imidazo[4,5-d]pyridazine NaH (12.3 g, 307.3 mmol) was added at 0-5 °C to a mixture of i-PrOH (300 mL) under N2. The mixture was stirred at 0-5 °C for 30 min, then heated to 95-100 °C. To the reaction mixture was added dropwise a solution of 2-butyl-4,7-dichloro-1H-imidazo[4,5- d]pyridazine, Intermediate (E) (15 g, 61.5 mmol) in dioxane (150 mL) and the reaction was heated at 95-100 °C for a period of 12 h under N2. The residue was poured into cold water (2 V) and extracted with EtOAc (2 V x 3). The combined organic layers were washed with brine (2 V), dried over Na2SO4, filtered and concentrated under reduced pressure to give 16 g (97 % yield) of the expected compound.1H NMR (400 MHz, δ in ppm, DMSO-d6): 0.91 (t, J=7 Hz, 3 H); 1.35 (m, 8 H); 1.71 (m, 2 H); 2.72 (t, J=7.6 Hz, 2 H); 3.78 (m, 1 H); 5.49 (m, 1 H) Step 2: 2-butyl-N-[(2,4-dimethoxyphenyl)methyl]-4-isopropoxy-3H-imidazo[4,5- d]pyridazin-7-amine To a solution of 2-butyl-4-chloro-7-isopropoxy-1H-imidazo[4,5-d]pyridazine from Step 1 (12 g, 44.75 mmol) and (2,4-dimethoxyphenyl)methanamine (7.48 g, 44.75 mmol) in THF (240 mL) were added NaOtBu (10.75 g, 111.89 mmol) and tBuXPhos Pd G-3 (1 g, 1.34 mmol). The reaction mixture was stirred at 60-65 °C for 3 h then poured into cold water (2 V) and extracted with EtOAc (2 V x 3). The combined organic layers were washed with brine (2 V), dried over Na2SO4, filtered and concentrated under reduced pressure to give 11.1 g (62 % yield) of Intermediate (S).1H NMR (400 MHz, δ in ppm, DMSO-d6): 0.89 (t, J=7.2 Hz, 3 H); 1.32 (m, 8 H); 1.72 (m, 2 H); 2.82 (t, J=7.6 Hz, 2 H); 3.72 (s, 3 H); 3.78 (s, 3 H); 4.53 (d, J=4.8 Hz, 2H); 5.38 (m, 1 H), 6.43 (d, J=7.6, 1 H); 6.53 (s, 1H)); 7.14 (bs, 1 H) Preparation 11: Intermediate (T) 2-butyl-4-chloro-3-methyl-imidazo[4,5-d]pyridazin-7- amine Step1: 2-butyl-4,7-dichloro-3-methyl-imidazo[4,5-d]pyridazine To a solution of 2-butyl-4,7-dichloro-1H-imidazo[4,5-d]pyridazine, Intermediate (E) (5 g, 20.4 mmol) in acetone (65 mL) was added potassium carbonate (8.5 g, 61.20 mmol). After 30 min of stirring at rt methyl iodide (1.9 mL, 30.60 mmol) was added dropwise and the reaction mixture was stirred for 4 h. The solids were removed by filtration over a glass frit and the filtrate was concentrated to dryness. The residue was taken up in DCM (50 mL) and washed with water (2 x 40 mL) and brine (40 mL). The organic phase was collected, dried over MgSO4, filtered and concentrated to dryness to give a dark orange solid that was then triturated in isopropylic ether, collected by filtration and air dried. The expected product was obtained as a light pink solid (4.5 g, 85 % yield). MS method N1: tR (min): 1.38; [M+H]+258.9 Step2: 2-butyl-4-chloro-3-methyl-imidazo[4,5-d]pyridazin-7-amine A solution of 2-butyl-4,7-dichloro-3-methyl-imidazo[4,5-d]pyridazine from Step 1 (1.55 g, 5.98 mmol) was reacted with a solution of 35 % ammonia (30 mL) at 160 °C (36 bars of pression) for 3 h. The resulting suspension was concentrated to dryness, taken up in water (20 mL), stirred for 2 h, then further triturated in isopropylalcohol, filtered and air dried to give 533 mg (37 % yield) of Intermediate (T) as a beige solid. MS method N1: tR(min): 0.85; [M+H]+239.9 Synthesis of TLR agonists Example (TLR1): Preparation of 2-butyl-7-isopropoxy-1-(4-(piperazin-1- ylmethyl)benzyl)-1H-imidazo[4,5-d]pyridazin-4-amine Step 1: 4-((4-(bis(2,4-dimethoxybenzyl)amino)-2-butyl-7-isopropoxy-1H-imidazo[4,5- d]pyridazin-1-yl)methyl)benzaldehyde To a suspension of intermediate (M) (2.2 g, 3.12 mmol) in Me-THF (21 mL) was added 4- (bromomethyl)benzaldehyde (847 mg, 4.26 mmol) and Cs2CO3(1.32 g, 4.11 mmol)). The mixture was stirred at rt during 24 h. The mixture was poured into Me-THF (15 mL) then washed with H2O (15 mL), dried over anhydrous MgSO4, filtered and the filtrate was concentrated under reduced pressure to give 3 g of crude product, which was purified by chromatography on a Merck cartridge (150 g of 15-40 μm silica) with EtOAc / heptane (38 / 62) elution. Expected product (1.5 g, 71% yield) was obtained as a white solid.1H NMR (400 MHz, δ in ppm, DMSO-d6): 0.76 (t, J=7.4 Hz, 3 H); 1.13 (d, J=6.2 Hz, 6 H); 1.24 (m, 2 H); 1.56 (m, 2 H); 2.77 (t, J=7.5 Hz, 2 H); 3.71 (s, 12 H); 5.02 (s, 4 H); 5.26 (sept, J=6.2 Hz, 1 H); 5.69 (s, 2 H); 6.40 (dd, J=2.5 & 8.4 Hz, 2 H); 6.53 (d, J=2.5 Hz, 2 H); 6.99 (d, J=8.4 Hz, 2 H); 7.25 (d, J=8.3 Hz, 2 H); 7.89 (d, J=8.3 Hz, 2 H); 9.97 (s, 1 H) MS method N: tR(min): 1.66; [M+H]+668; ES- [2M-H+HCO2H]-: m / z 1379 Step 2: tert-butyl 4-(4-((4-(bis(2,4-dimethoxybenzyl)amino)-2-butyl-7-isopropoxy-1H- imidazo[4,5-d]pyridazin-1-yl)methyl)benzyl)piperazine-1-carboxylate To a solution of 4-((4-(bis(2,4-dimethoxybenzyl)amino)-2-butyl-7-isopropoxy-1H- imidazo[4,5-d]pyridazin-1-yl)methyl)benzaldehyde of Step 1 (200 mg, 0.30 mmol) in methanol (2.5 mL) was added 1-Boc-piperazine (85.38 mg, 0.45 mmol), acetic acid (34.29 µL, 0.60 mmol). The mixture was stirring at rt during 10 min and then sodium cyanoborohydride (28.23 mg, 0.45 mmol) was added. The stirring was continued at rt during 4.5 h. The reaction was poured into water and pH adjusted to 9 by addition of ammonia solution (35%). Then the mixture was extracted by EtOAc. The organic layer was dried over anhydrous MgSO4, filtered and concentrated under vacuum to give 0.45 g of oil. The expected crude product (289 mg) as white gum was used directly in the next step. Step 3: Example (TLR1) Preparation of 2-butyl-7-isopropoxy-1-(4-(piperazin-1- ylmethyl)benzyl)-1H-imidazo[4,5-d]pyridazin-4-amine To a solution of tert-butyl 4-(4-((4-(bis(2,4-dimethoxybenzyl)amino)-2-butyl-7- isopropoxy-1H-imidazo[4,5-d]pyridazin-1-yl)methyl)benzyl)piperazine-1-carboxylate of Step 2 (250 mg, 0.3 mmol) in DCM (6.3 mL) was added 2,2,2-trifluoroacetic acid (919.29 µL, 11.93 mmol). The mixture was stirred at rt for 24 h. The reaction was poured into DCM and washed with sodium hydroxide 1M. The organic layer was dried over anhydrous MgSO4, filtered and concentrated under vacuum to give 145 mg of crude product, which was purified by chromatography on a Merck cartridge (20 g of 15- 40 μm silica) with CH2Cl2 / MeOH / NH4OH (90 / 10 / 0.2) elution, to afford Example (TLR1) (45 mg, 35% yield) as a white solid.1H NMR (400 MHz, δ in ppm, DMSO-d6): 0.81 (t, J=7 Hz, 3 H); 1.17 (d, J=6 Hz, 6 H); 1.29 (dq, J=7 & 15 Hz, 2 H); 1.59 (quin, J=8 Hz, 2 H); 2.22 (s broad, 4 H); 2.63 (t, J=5 Hz, 4 H); 2.81 (t, J=7 Hz, 2 H); 3.36 (s, 2 H); 5.30 (spt, J=6 Hz, 1 H); 5.55 (s, 2 H); 5.94 (s, 2 H); 7.00 (d, J=8 Hz, 2 H); 7.24 (d, J=8 Hz, 2 H) MS method N: tR(min): 0.80; [M+H]+438 Example (TLR2): Preparation of 3-[[trans-4-(aminomethyl)cyclohexyl]methyl]-2-butyl-4- propan-2-yloxyimidazo[4,5-d]pyridazin-7-amine dihydrochloride Step 1:^tert-butyl (4-(trans-4-(bis(2,4-dimethoxybenzyl)amino)-2-butyl-7-isopropoxy-1H- imidazo[4,5-d]pyridazin-1-yl)methyl)cyclohexyl)methyl)carbamate To a suspension of 2-butyl-N,N-bis(2,4-dimethoxybenzyl)-7-isopropoxy-1H-imidazo[4,5- d]pyridazin-4-amine, intermediate (M) (1 g, 1.82 mmol) in Me-THF (20 mL) was added Cs2CO3 (1.78 g, 5.46 mmol). The mixture was^stirred^at rt for 30 min. Then tert-butyl n- ([(1R,4R)-4(bromomethyl)cyclohexyl]methyl)carbamate (879 mg, 2.73 mmol) in Me-THF (12 mL) was added. The mixture was stirred for 5 min at^rt then refluxing for 24 h. The reaction mixture was then diluted with EtOAc (150 mL), washed with water and brine, concentrated under reduced pressure to give 1.73 g of crude product, which was purified by chromatography on a Merck cartridge (70 g of 15-40^μm^silica) with a 0 / 100 to 50 / 50^EtOAc / heptane elution. Expected product (1.03 g, 73% yield) was obtained as a white solid.1H NMR (400 MHz, δ in ppm, DMSO-d6): 0.75 (m, 2 H); 0.83 (t, J=7 Hz, 3 H); 1.08 (m, 2 H); 1.24 to 1.40 (m, 18 H); 1.48 (d, J=12 Hz, 2 H); 1.58 to 1.81 (m, 5 H); 2.73 (t, J=6 Hz, 2 H); 2.77 (t, J=7 Hz, 2 H); 3.66 to 3.76 (m, 12 H); 4.10 (d, J=6 Hz, 2 H); 5.00 (broad s, 4 H); 5.37 (spt, J=6 Hz, 1 H); 6.39 (dd, J=2 & 8 Hz, 2 H); 6.52 (d, J=2 Hz, 2 H); 6.78 (t, J=6 Hz, 1 H); 6,96 (d, J=8 Hz, 2 H) MS method N: tR(min): 1.87; [M+H]+775 Step 2: Example^(TLR2) Preparation of 3-[[trans-4-(aminomethyl)cyclohexyl]methyl]-2- butyl-4-propan-2-yloxyimidazo[4,5-d]pyridazin-7-amine dihydrochloride To a solution of ^tert-butyl (4-(trans-4-(bis(2,4-dimethoxybenzyl)amino)-2-butyl-7- isopropoxy-1H-imidazo[4,5-d]pyridazin-1-yl)methyl)cyclohexyl)methyl)carbamate of Step 1 (1.03 g, 1.33 mmol) in DCM (6 mL) was added 2,2,2-trifluoroacetic acid (6 mL, 77.9 mmol) and 1,3-dimethoxybenzene (522 µL, 3.99 mmol). The mixture was^stirred^for 24 h at rt. The reaction was diluted with DCM (50^mL) and H2O (10 mL). The pH of the mixture was adjusted to pH 10-12 with 30% NaOH under stirring in an ice bath. The product was extracted with DCM (4 x 50 mL), the combined organic layers were washed with brine, dried over MgSO4, filtered and concentrated under reduced pressure to give 3.1 g of crude product. The residue was purified by chromatography on a Macherey Nagel cartridge (40 g of 15-40 µm diol silica) with 100 / / 0 to 50 / / 50 DCM- DCM / MeOH / H20(80 / 10 / 1) to give an oil. The oil was treated with iPr2O (10 mL), a white solid was filtered and washed with iPr2O (3 x 5 mL) dried in vacuo to give 617 mg of powder. 500 mg of this product was purified on a C18 Waters Xbridge column (19 x 150 mm 5 µm), eluted with ammonium bicarbonate 10 mM (pH 10) / acetonitrile to afford 188 mg of material, which was dissolved in HCl in MeOH (1.25N) and the mixture was evaporated under reduced pressure. The residue was then dissolved in water, filtrated over a 0.22 µm membrane, the filtrate was freeze - dried to give 190 mg (39.5%, yield) of Example (TLR2), under hydrochloric acid form (2 HCl).1H NMR (400 MHz, δ in ppm, DMSO-d6): 0.87 (q, J=13 Hz, 2 H); 0.94 (t, J=7 Hz, 3 H); 1.12 (q, J=13 Hz, 2 H); 1.33 to 1.48 (m, 8 H); 1.51 to 1.63 (m, 3 H); 1.66 to 1.92 (m, 5 H); 2.63 (t, J=6 Hz, 2 H); 2.93 (t, J=8 Hz, 2 H); 4.21 (d, J=7 Hz, 2 H); 5.24 (quin, J=6 Hz, 1 H); 7.90 (s broad, 3 H); 8.57 (s broad, 2 H); 13.89 (s, 1 H) MS method N: tR(min): 0.83; [M+H]+375 Example (TLR3): Preparation of 1-(4-(aminomethyl)benzyl)-2-butyl-7-isopropoxy-1H- imidazo[4,5-d]pyridazin-4-amine Step 1: tert-butyl (4-((4-(bis(2,4-dimethoxybenzyl)amino)-2-butyl-7-isopropoxy-1H-imida zo[4,5-d]pyridazin-1-yl)methyl)benzyl)carbamate To a suspension of 2-butyl-N,N-bis(2,4-dimethoxybenzyl)-7-isopropoxy-1H-imidazo[4,5- d]pyridazin-4-amine, intermediate (M) (1 g, 1.82 mmol) in Me-THF (30 mL)^was added^Cs2CO3(1.78 g, 5.46 mmol). The mixture was^stirred 30 min^at^rt, tert-butyl 4- (bromomethyl)benzylcarbamate^(819 mg, 2.73 mmol)^was then added. The mixture was stirred at^rt for 16 h. The reaction mixture was diluted with 150 mL of Me-THF and washed with water and brine, dried over anhydrous MgSO4, filtered and the filtrate was concentrated under reduced pressure to give 1.73 g of crude product. The residue was purified by chromatography on a Merck cartridge (50 g of 15-40 µm silica) with 100 / 0 to 50 / 50 DCM- DCM / MeOH (90 / 10) elution. Expected product (1.34 g, 96 % yield) was obtained as a white foam.1H NMR (400 MHz, δ in ppm, DMSO-d6): 0.76 (t, J=7 Hz, 3 H); 1.21 (m, 8 H); 1.37 (s, 9 H); 1.55 (quin, J=7 Hz, 2 H); 2.74 (t, J=7 Hz, 2 H); 3.71 (s, 12 H); 4.07 (d, J=6 Hz, 2 H); 5.01 (s, 4 H); 5.31 (quin, J=6 Hz, 1 H); 5.55 (s, 2 H); 6.39 (dd, J=2 et & 8 Hz, 2 H); 6.52 (d, J=2 Hz, 2 H); 6.97 (d, J=8 Hz, 2 H); 7.03 (d, J=8 Hz, 2 H); 7.19 (d, J=8 Hz, 2 H); 7.34 (t, J=6 Hz, 1 H) MS method N: tR(min): 1.87; [M+H]+769 Step 2: Example (TLR3) Preparation of 1-(4-(aminomethyl)benzyl)-2-butyl-7-isopropoxy- 1H-imidazo[4,5-d]pyridazin-4-amine To a solution of tert-butyl (4-((4-(bis(2,4-dimethoxybenzyl)amino)-2-butyl-7-isopropoxy- 1H-imidazo[4,5-d]pyridazin-1-yl)methyl)benzyl)carbamate of Step 1 (684 mg, 0.889 mmol)^in DCM (10 mL) cooled in an ice bath were added 1,3-dimethoxybenzene (349 µL, 2.67 mmol) and 2,2,2-trifluoroacetic acid (10 mL, 129.8 mmol). After 15 min, the ice bath was removed, and the mixture was^stirred^16 h^at^rt.^The reaction mixture was diluted with DCM (100^mL) and H2O (50 mL), the aqueous phase was washed by DCM (2 x 50 mL). The pH of the aqueous layer was adjusted to pH 11 with 30% NaOH under stirring in an ice bath. The product was extracted with DCM (4 x 50 mL), the combined organic layer was dried over MgSO4, filtered and concentrated under reduced pressure to give 306 mg of crude product, which was purified by chromatography on a Macherey Nagel cartridge (26 g of 15-40 µm diol silica) with 100 / 0 to 0 / 100 DCM-DCM / MeOH (90 / 10) elution, to give 91 mg of purified compound, which was further purified on a C18 Waters Xbridge column (19 x 150 mm 5 µm), eluted with ammonium bicarbonate 10 mM (pH10) / MeCN elution to afford 64 mg (20% yield) of Example (TLR3).1H NMR (400 MHz, δ in ppm, DMSO-d6): 0.84 (t, J=7 Hz, 3 H); 1.21 (s, 3 H); 1.23 (s, 3 H); 1.33 (m, 2 H); 1.63 (m, 2 H); 1.97 (m, 2 H); 2.79 (d, J=15 Hz, 2 H); 3.66 (s, 2 H); 5.33 (spt, J=6 Hz, 1 H); 5.54 (s, 2 H); 5.91 (s, 2 H); 7.01 (d, J=8 Hz, 2 H); 7.28 (d, J=8 Hz, 2 H) MS method N: tR (min): 0.76; [M+H]+369 Example (TLR4): Preparation of 3-[[4-(aminomethyl)phenyl]methyl]-4-isopropoxy-2- propylsulfanyl-imidazo[4,5-d]pyridazin-7-amine Step 1: tert-butyl N-[[4-[[7-[bis[(2,4-dimethoxyphenyl)methyl]amino]-4-isopropoxy- imidazo[4,5-d]pyridazin-3-yl]methyl]phenyl]methyl]carbamate To a round-bottom flask were added N,N-bis[(2,4-dimethoxyphenyl)methyl]-4-isopropoxy- 3H-imidazo[4,5-d]pyridazin-7-amine, Intermediate (R) (450 mg, 0.91 mmol), MeTHF (6 mL), tert-butyl 4-(bromomethyl)benzylcarbamate (310 mg, 1.00 mmol) and Cs2CO3(891 mg, 2.74 mmol). The resulting mixture was stirred at rt for 2 h. The reaction was then diluted with EtOAc and washed with brine. The organic layer was separated, dried over MgSO4, filtered and evaporated to give a white foam. The crude material was purified by a silica gel column (80 g) using as solvent heptane / EtOAc (60 / 40) to give 0.52 g (80% yield) of a white solid.1H NMR (400 MHz, δ in ppm, DMSO-d6):1.28 (d, J=6.1 Hz, 6 H); 1.37 (s, 9 H); 3.70 (m, 12 H); 4.05 (m, 2 H); 4.98 (s, 4 H); 5.34 (sept, J=6.2 Hz, 1 H); 5.54 (s, 2 H); 6.39 (dd, J=8.3, 2.4 Hz, 2 H); 6.52 (d, J=2.4 Hz, 2 H); 6.94 (d, J=8.3 Hz, 2 H); 7.21 (m, 4 H); 7.33 (m, 1 H); 8.46 (s, 1 H) MS method N: tR(min): 1.57, [M+H]+713 Step 2: tert-butyl N-[[4-[[7-[bis[(2,4-dimethoxyphenyl)methyl]amino]-4-isopropoxy-2- propylsulfanyl-imidazo[4,5-d]pyridazin-3-yl]methyl]phenyl]methyl]carbamate To a Keller tricol equipped with magnetic stir, thermometer probe, under argon, were added tert-butyl N-[[4-[[7-[bis[(2,4-dimethoxyphenyl)methyl]amino]-4-isopropoxy-imidazo[4,5- d]pyridazin-3-yl]methyl]phenyl]methyl]carbamate of Step 1 (50 mg, 0.07 mmol), and anhydrous THF (1 mL). The homogenous solution was cooled to -30°C, to which was added n-BuLi (50 µL, 1.6 M in heptane, 0.077 mmol) and stirred at -30°C for 20 min, followed by addition of propyl disulfide (13 µL, 0.084 mmol). The reaction mixture was allowed to reach slowly rt and stirred for 2 h. It was then cooled again to -30°C, n-BuLi (100 µL, 1.6 M in heptane, 0.154 mmol) was added, the reaction mixture turned to red with some slight precipitation. It was stirred for 30 min and followed by addition of propyl disulfide (26 µL, 0.168 mmol). The reaction mixture was allowed to reach slowly rt and stirred overnight. 20 mL of water and 30 mL of EtOAc were then added and the crude media was transferred to a separating funnel. After separation of organic phase, the aqueous phase was extracted with EtOAc (2 x 30 mL). The combined organic phase was washed with brine, dried over MgSO4, filtered and evaporated to dryness to give 55 mg of crude product. The crude material was purified by a silica gel column (5 g, Merck) using as heptane / EtOAc (70 / 30) elution to give 0.015 g (28% yield) of a white gum.1H NMR (400 MHz, δ in ppm, DMSO-d6):0.76 (t, J=7.3 Hz, 3 H); 1.11 - 1.31 (m, 6 H); 1.37 (s, 9 H); 1.52 (sxt, J=7.3 Hz, 2 H); 3.06 (t, J=7.2 Hz, 2 H); 3.67 - 3.78 (m, 12 H); 4.07 (br d, J=6.1 Hz, 2 H); 4.97 (s, 4 H); 5.33 (m, 1 H); 5.41 (s, 2 H); 6.40 (dd, J=8.5, 2.2 Hz, 2 H); 6.53 (d, J=2.2 Hz, 2 H); 6.98 (d, J=8.5 Hz, 2 H); 7.12 (d, J=8.3 Hz, 2 H); 7.19 (d, J=8.3 Hz, 2 H); 7.33 (t, J=6.2 Hz, 1 H) MS method N: tR (min): 1.75, [M+H]+787 Step 3: Example^(TLR4) Preparation of 3-[[4-(aminomethyl)phenyl]methyl]-4- isopropoxy-2-propylsulfanyl-imidazo[4,5-d]pyridazin-7-amine To a solution of tert-butyl N-[[4-[[7-[bis[(2,4-dimethoxyphenyl)methyl]amino]-4- isopropoxy-2-propylsulfanyl-imidazo[4,5-d]pyridazin-3-yl]methyl]phenyl]methyl] carbamate of Step 2 (147 mg, 0.187 mmol) in DCM (1.5 mL) was added dropwise TFA (0.50 mL, 5.55 mmol). The mixture became pink and was stirred at rt for 5.5 h, then evaporated to dryness. The crude product was dissolved in MeOH with some purple precipitates which were filtered. The filtrate was loaded into a SCX cartridge (20 g, pre- washed with 10 ml of MeOH), the cartridge was eluted with MeOH (60 mL) and 2N MeOH- NH3. The ammoniacal methanolic solution was evaporated to dryness to give 56 mg of foam which was purified by a silica gel column (Merck, 10 g) using as eluent a mixture DCM / NH3-MeOH 7N (97 / 3) to give 22 mg (31% yield) of Example (TLR4) as a white solid.1H NMR (400 MHz, δ in ppm, DMSO-d6): 0.96 (t, J=7 Hz, 3 H); 1.25 (d, J=6 Hz, 6 H); 1.72 (sxt, J=7 Hz, 2 H); 2.06 - 2.30 (m, 2 H); 3.30 - 3.33 (m, 2 H); 3.67 (s, 2 H); 5.34 (quin, J=6 Hz, 1 H); 5.43 (s, 2 H); 5.91 (s, 2 H); 7.11 (d, J=1 Hz, 2 H); 7.29 (d, J=1 Hz, 2 H) MS method N: tR(min): 0.90, [M+H]+387 Example (TLR5): Preparation of 3-[[4-(aminomethyl)phenyl]methyl]-4-isopropoxy-N2- propyl-imidazo[4,5-d]pyridazine-2,7-diamine Step 1: tert-butyl N-[[4-[[7-[bis[(2,4-dimethoxyphenyl)methyl]amino]-2-bromo-4- isopropoxy-imidazo[4,5-d]pyridazin-3-yl]methyl]phenyl]methyl]carbamate To a -30°C solution of tert-butyl N-[[4-[[7-[bis[(2,4-dimethoxyphenyl)methyl]amino]-4- isopropoxy-imidazo[4,5-d]pyridazin-3-yl]methyl]phenyl]methyl]carbamate of Step 2 in Example (TLR4) (103 mg, 0.144 mmol) in dry THF (2 mL), under argon, was added a 2.5 M solution of n-BuLi in hexane (0.35 mL, 0.86 mmol). The mixture was kept 30 min at the same temperature then a solution of NBS (67.42 mg, 0.36 mmol) in dry THF (2 mL) was added. After the addition was completed, the mixture was left at rt. The reaction color turned to yellow / orange. The reaction was stopped after 2 h at rt. The reaction mixture was cooled at -10°C, added saturated solution of NH4Cl, and diluted with EtOAc. The organic solution was separated, washed with brine, dried over MgSO4, filtered and evaporated to give a yellow oil. The crude material was purified by a silica gel column using as eluent a mixture CHCl3 / acetone (96 / 4) to give 24.6 mg (21% yield) of the expected product, as a yellow solid.1H NMR (400 MHz, δ in ppm, DMSO-d6): 1.24 (d, J=6.0 Hz, 6 H); 1.37 (s, 9 H); 3.67 - 3.74 (m, 12 H); 4.08 (d, J=6.3 Hz, 2 H); 4.94 (s, 4 H); 5.33 (sept, J=6.1 Hz, 1 H); 5.56 (s, 2 H); 6.41 (dd, J=8.4, 2.4 Hz, 2 H); 6.53 (d, J=2.4 Hz, 2 H); 6.97 (d, J=8.4 Hz, 2 H); 7.12 (m, J=8.3 Hz, 2 H); 7.21 (m, J=8.3 Hz, 2 H); 7.31 (t, J=5.8 Hz, 1 H) MS method N: tR(min): 1.67, [M+H]+791 Step 2: tert-butyl N-[[4-[[7-[bis[(2,4-dimethoxyphenyl)methyl]amino]-4-isopropoxy-2- (propylamino)imidazo[4,5-d]pyridazin-3-yl]methyl]phenyl]methyl]carbamate A mixture of tert-butyl N-[[4-[[7-[bis[(2,4-dimethoxyphenyl)methyl]amino]-2-bromo-4- isopropoxy imidazo[4,5-d]pyridazin-3-yl]methyl]phenyl]methyl]carbamate of Step 1 (85.2 mg, 0.108 mmol), n-propylamine (1.44 mL) and DMF (0.02 mL) was heated at 100°C in the microwave for 2.5 h. The reaction mixture was diluted with EtOAc and washed with H2O. The organic layer was separated, dried over MgSO4, filtered and evaporated to give a white transparent oil. The crude material was purified by a silica gel column using as eluent a mixture DCM / iPrOH (98 / 2 to 96 / 4) to give 67 mg of the expected ...

Claims

CLAIMS 1. A compound of formula (I) or a pharmaceutically acceptable salt thereof: A-L1-RCG1 (I) wherein: - A is a drug unit of formula (A)wherein: R1 represents: - a hydrogen atom, or - a group selected from: a) - a (C1-C6)alkyl- group; - a hydroxy-(C1-C6)alkyl- group; - a NH2-(C1-C6)alkyl- group; - a NH-(C1-C6)alkyl-(C1-C6)alkyl- group;- a N((C1-C6)alkyl)2-(C1-C6)alkyl- group; - a (C2-C6)alkenyl- group; - a (C2-C6)alkynyl- group; b) - a phenyl(C1-C6)alkyl- group being unsubstituted or substituted by at least one substituent selected from: b1) - a (C1-C6)alkoxy- group; b2) - a hydroxyl group;b3) a -C(O)-H group; and b4) - a (C1-C6)alkyl- group being unsubstituted or substituted by at least one substituent selected from: b4.1) - a hydroxyl group; and b4.2) - a -NR4R5 group wherein R4 and R5, being independently from each other selected from: b4.2.1) - a hydrogen atom; b4.2.2) - a (C1-C16)alkyl- group; b4.2.3) - a CH3-[O-(CH2)2]n- group with n being an integer from 1 to 30, a (C1-C6)alkoxy(C1-C6)alkyl- group, or a (C1-C6)alkoxy(C1-C6)alkoxy(C1-C6)alkyl- group; b4.2.4) - a (C1-C6)alkyl-S(O2)- group; b4.2.5) - a (C1-C6)alkyl-NH-C(O)- group; b4.2.6) - a (C1-C16)alkyl-C(O)- group; b4.2.7) - a (C1-C16)alkyl-O-C(O)- group; b4.2.8) - a CH3-[O-(CH2)2]n-C(O)- group with n being an integer from 1 to 30; b4.2.9) - a (C3-C10)cycloalkyl- group being unsubstituted or substituted by at least one substituent selected from: - a hydroxyl group; and - a (C1-C6)alkyl- group; or b4.2.10) - a (C3-C10)membered heterocycloalkyl- group comprising from one to four heteroatoms selected from oxygen, nitrogen, sulfur, -S(O)- and -SO2-; b4.2.11) - a phenyl-C(O)- group; b4.2.12) - a (C1-C6)alkoxy-phenyl-(C1-C6)alkyl-O-C(O)- group; b4.2.13) - a (C1-C16)alkyl-C(O)-NH-phenyl-(C1-C6)alkyl-O-C(O)- group; b4.2.14) - a (C1-C16)alkyl-O-C(O)-(C1-C6)alkyl- group; or R4and R5form together with the nitrogen atom to which they are attached a (C3-C10)membered heterocycloalkyl- group comprising one to four heteroatoms selected from oxygen, nitrogen and sulfur, said (C3-C10)membered heterocycloalkyl- group being unsubstituted or substituted by at least one substituent selected from a (C1-C6)alkyl- group, and a CH3-[O-(CH2)2]n- group with n being an integer from 1 to 30;c) - a (C3-C10)cycloalkyl(C1-C6)alkyl- group being unsubstituted or substituted by at least one substituent selected from -NH2and a NH2-(C1-C6)alkyl- group; d) - a (C3-C10)membered heterocycloalkyl(C1-C6)alkyl- group comprising one to four heteroatoms selected from oxygen, nitrogen, and sulfur, said heterocycloalkyl group being unsubstituted or substituted by at least one substituent selected from a (C1-C6)alkyl- group and a CH3-[O-(CH2)2]n- group with n being an integer from 1 to 30; and e) - a (C5-C10)membered heteroaryl(C1-C6)alkyl- group comprising one to four heteroatoms selected from oxygen, nitrogen, and sulfur, said heteroaryl being unsubstituted or substituted by at least one substituent selected from: - a (C1-C6)alkyl- group; - a NH2-(C1-C6)alkyl- group and - a cyano group; f) - a (C3-C10)membered heterocycloalkyl-NH-(C1-C16)alkyl- group, said heterocycloalkyl group comprising one to four heteroatoms selected from oxygen, nitrogen, S(O), SO2 and sulfur; g) - a (C3-C10)membered heterocycloalkyl-N(C(O)-(C1-C6)alkyl)-(C1-C16)alkyl- group, said heterocycloalkyl group comprising one to four heteroatoms selected from oxygen, nitrogen, S(O), SO2and sulfur; R2 represents a halogen atom, or a group selected from: - a (C1-C6)alkyl- group; - a (C2-C6)alkenyl- group; - a (C2-C6)alkynyl- group; - a (C1-C6)alkylthio- group; - a (C1-C6)alkylthio(C1-C6)alkyl- group; - a (C1-C6)alkyl-S(O)- group;- a (C1-C6)alkyl-S(O2)- group; - a (C1-C6)alkyl-S(O)-(C1-C6)alkyl- group; - a (C1-C6)alkyl-S(O2)-(C1-C6)alkyl- group; - a (C1-C6)alkoxy- group; - a (C1-C6)alkoxy(C1-C6)alkyl- group; - a (C1-C6)haloalkoxy(C1-C6)alkyl- group; - a (C3-C5)cycloalkyl-O-(C1-C6)alkyl- group; - a (C1-C6)alkyl-NH-(C1-C6)alkyl- group; - a ((C1-C6)alkyl)2-N-(C1-C6)alkyl- group; - a (C1-C6)alkyl-NH- group; and - a ((C1-C6)alkyl)2N- group; R3 represents: - a deuterium atom; - a hydrogen atom or a group selected from: a) - a (C1-C6)alkyl- group; - a (C2-C6)alkenyl- group; - a (C2-C6)alkynyl- group; and -a (C1-C6)alkylthio- group; b) - a -OR6group wherein R6is selected from: - a hydrogen atom; - a (C1-C6)alkyl- group; - a CH3-[O-(CH2)2]n- group with n being an integer from 1 to 30; - a (C2-C6)alkenyl- group; - a (C2-C6)alkynyl- group; - a (C3-C10)cycloalkyl- group; - a phenyl group;- a phenyl(C1-C6)alkyl- group; and - a (C3-C10)membered heterocycloalkyl- group comprising one to four heteroatoms selected from oxygen, nitrogen, sulfur, -S(=O)- and -S(=O)2-; c) - a -NR7R8group wherein R7and R8being, independently from each other, selected from: - a hydrogen atom; - a CH3-[O-(CH2)2]n- with n being an integer from 1 to 30; - a (C1-C6)alkyl- group unsubstituted or substituted by - a (C5-C10)membered heteroaryl group comprising one to four heteroatoms selected from oxygen, nitrogen and sulfur; or - a phenyl group being unsubstituted or substituted by at least one substituent selected from: - a cyano group and - a NR9R10-(C1-C6)alkyl- group wherein: R9and R10being, independently from each other, selected from: - a hydrogen atom; - a (C1-C6)alkyl- group; - a CH3-[O-(CH2)2]n- with n being an integer from 1 to 30, or R9and R10together form with the nitrogen atom to which they are attached a (C3-C10)membered heterocycloalkyl- group comprising one to four heteroatoms selected from oxygen, nitrogen, and sulfur, said (C3-C10)membered heterocycloalkyl group being unsubstituted or substituted by at least one substituent selected from a (C1-C6)alkyl- group, and a CH3-[O-(CH2)2]n- group with n being an integer from 1 to 30; or R7and R8form together with the nitrogen atom to which they are attached a (C3-C10)membered heterocycloalkyl- group comprising one to four heteroatoms selected from oxygen, nitrogen, and sulfur, said heterocycloalkyl group being unsubstituted or substituted by at least one substituent selected from: - a phenyl group and- a hydroxy(C1-C6)alkyl-phenyl- group; d) - a (C3-C10)membered heterocycloalkyl- group comprising one to four heteroatoms selected from oxygen, nitrogen and sulfur; e) - a (C5-C10)membered heteroaryl- group comprising one to four heteroatoms selected from oxygen, nitrogen, and sulfur, said (C5-C10)membered heteroaryl- group being unsubstituted or substituted by at least one (C1-C6)alkyl- group; f) - a (C6-C10)membered aryl- group; and g) - a (C3-C10)cycloalkyl- group; - L1 represents a linker; and - RCG1 represents a reactive chemical group that is reactive towards a chemical group present on a binding agent, for instance on a protein, a polypeptide, a ligand, a peptide, an oligonucleotide or an oligosaccharide, for instance on a targeting agent for instance on a cell- binding agent such as an antibody such as a monoclonal antibody or a VHH antibody.

2. The compounds of formula (I) or a pharmaceutically acceptable salt thereof according to claim 1, wherein L1 represents a cleavable linker or a non - cleavable linker.

3. The compounds of formula (I) or a pharmaceutically acceptable salt thereof according to claim 1 or claim 2, wherein: - when L1 is a cleavable linker, it is a peptidic linker; or - when L1 is a non-cleavable linker, it is a PEGylated linker.

4. The compounds of formula (I) or a pharmaceutically acceptable salt thereof according to any one of claims 1 to 3, wherein RCG1 represents: (i) a RaZa-C(=O)- reactive group for which: Za represents a single bond, -O- or -NH, such as -O-, and Ra represents a hydrogen atom, a -(C1-C6)alkyl group, a -(C3-C7)cycloalkyl group, a -(C2-C6)alkenyl group, a -(C6-C10)aryl group, a -(C5-C10)heteroaryl group comprising 4 to 9 carbon atoms and 1 to 4 heteroatom(s) selected from oxygen, nitrogen, and sulfur, or a -(C3-C7)heterocycloalkyl group comprising 2 to 6 carbon atoms and 1 to 4 heteroatom(s) selected from oxygen, nitrogen, sulfur, -S(O)- and -SO2-, said -(C6-C10)aryl group, -(C5-C10)heteroaryl group and / or -(C3-C7)heterocycloalkyl group being optionally substituted by 1 to 5 atoms / groups chosen from a halogen atom, such as a fluorine atom, a - (C1-C6)alkyl group, a -(C1-C6)alkoxy group, a hydroxyl group, an oxo group, a nitro group and a cyano group; or O N (ii) one of the following reactive groups: a maleimido O group; asubstituted maleimido group such as O ; a haloacetamido R21 p with R21representing a hydrogen atom or a (C1-C6)alkyl group, roup; Cl-; N3-; HO-; HS-; an activated disulfide such as; H2N-; HC≡C- or an activated C≡C such as a cyclooctyne moiety;r reaction substrate such, for instance RCG1is N3-, a maleimido group, a substituted maleimido group5. The compounds of formula (I) or a pharmaceutically acceptable salt thereof according to claim 1, wherein A is of formula (A1) or of formula (A2)in which: R1, R2 and R3 are as defined in claim 1; the single asterisk (*) indicates the site of covalent attachment to -L1-RCG1; R1* represents: - either a single bond, which means that -L1-RCG1 is directly linked to the nitrogen atom of the imidazo[4,5-d]pyridazine ring, - or a divalent radical formed from R1as defined in the present disclosure, which means that -L1-RCG1 is linked to the nitrogen atom of the imidazo[4,5-d]pyridazine ring via R1; R3* represents: - either a single bond, which means that -L1-RCG1 is directly linked to the carbon atom of the imidazo[4,5-d]pyridazine ring, - or a divalent radical formed from R3as defined in the present disclosure, which means that -L1-RCG1 is linked to the carbon atom of the imidazo[4,5-d]pyridazine ring via R3.

6. The compounds of formula (I) or a pharmaceutically acceptable salt thereof according to claim 1, wherein A is chosen among:;.

7. The compounds of formula (I) or a pharmaceutically acceptable salt thereof according to any one of claims 1 to 6, wherein said compound is chosen among a compound of formula (I1) and a compound of formula (I2): A-(La)m-(AA)w-(Lb)p-Lc-Ld’-RCG1 (I1) wherein: - A is as defined in any one of claims 1, 5 and 6; - La represents a self immolative linker, for instance a *-C(O)-O-(CR14R15)-aryl-NR16-** group, *-C(O)-O-(CR14R15)-heteroaryl-NR16-** group, a *-C(O)-NR17-(C2-C6)alkyl-NR18- **, a *-C(O)-NR17-(C2-C6)alkyl-NR18-C(O)-O-CR15R14-aryl-NR16-** group, a *-C(O)- NR17-(C2-C6)alkyl-NR18-C(O)-O-CR15R14-heteroaryl-NR16-** group, a *-CR15R14-aryl- NR16-** group or a *-CR15R14-heteroaryl-NR16-** group, aryl being a (C6-C10) membered aryl group and heteroaryl being a (C5-C10) membered heteroaryl group comprising one to four heteroatoms selected from oxygen, nitrogen and sulfur, for instance a *-C(O)-O-CH2- phenyl-NH-** group, the single asterisk (*) indicating the site of covalent attachment to the A drug unit radical and the double asterisk (**) indicating the site of covalent attachment to the (AA)w radical; R14, R15, R16, R17 and R18 being a hydrogen atom or a (C1-C6)alkyl group;group; - m represents an integer from 0 to 1; - (AA)w represents a sequence of w amino acids AA connected together via peptide bonds; w representing an integer ranging from 1 to 12, for instance from 1 to 6, such as 2 and 3; AA denoting a natural or unnatural amino acid, of configuration D or L, chosen from: alanine (Ala), β-alanine, γ-aminobutyric acid, 2-amino-2-cyclohexylacetic acid, 2-amino-2-phenylacetic acid, arginine (Arg), asparagine (Asn), aspartic acid (Asp), citrulline (Cit), cysteine (Cys), α,α-dimethyl- γ-aminobutyric acid, β,β-dimethyl-γ- aminobutyric acid, glutamine (Gln), glutamic acid (Glu), glycine (Gly), histidine (His), isoleucine (Ile), leucine (Leu), lysine (Lys), ε-acetyl-lysine (AcLys), methionine (Met), ornithine (Orn), phenylalanine (Phe), proline (Pro), serine (Ser), threonine (Thr), tryptophan (Trp), tyrosine (Tyr), and valine (Val), for instance valine (Val), citrulline (Cit), alanine (Ala), and glutamic acid (Glu) ; - Lb represents a spacer, for instance a *-C(O)-(C1-C6)alkyl-C(O)-NH-** group or a *-C(O)- ** group, such as a *-C(O)-(CH2)3-C(O)-NH-** group or a *-C(O)-** group, the single asterisk (*) indicating the site of covalent attachment to the (AA)w radical and the double asterisk (**) indicating the site of covalent attachment to the Lc radical; - p represents an integer from 0 to 1; - Lc represents a spacer, for instance a *–(CH2-CH2-O)n-** group in which n represents an integer from 2 to 12, for instance from 3 to 7, such as 3 and 4 , the single asterisk (*) indicating the site of covalent attachment to the Lb radical if present (that is to say if p is 1) or directly to the (AA)w radical if Lb is not present (that is to say if p is 0) and the double asterisk (**) indicating the site of covalent attachment to the Ld’ radical; - Ld’ represents a spacer, for instance a *-(C2-C6)alkyl-** group, a *-(C2-C6)alkyl-NH- C(O)-(C2-C6)alkyl-** group or a *-(C2-C6)alkyl-C(O)-NH-(C2-C6)alkyl-** group, such as a*–(CH2)2-** group, a *-(CH2)2-NH-C(O)-(CH2)2-** group or a *-(CH2)2-C(O)-NH-(CH2)2- ** group, the single asterisk (*) indicating the site of covalent attachment to the Lc radical and the double asterisk (**) indicating the site of covalent attachment to the RCG1 radical; and - RCG1 is as defined in claim 1, for instance RCG1 represents: (i) a RaZa-C(=O)- reactive group for which: Zarepresents a single bond, -O- or -NH, such as -O-, and Ra represents a hydrogen atom, a -(C1-C6)alkyl group, a -(C3-C7)cycloalkyl group, a -(C2-C6)alkenyl group, a -(C6-C10)aryl group, a -(C5-C10)heteroaryl group comprising 4 to 9 carbon atoms and 1 to 4 heteroatom(s) selected from oxygen, nitrogen, and sulfur, or a -(C3-C7)heterocycloalkyl group comprising 2 to 6 carbon atoms and 1 to 4 heteroatom(s) selected from oxygen, nitrogen, sulfur, -S(O)- and -SO2-, said -(C6-C10)aryl group, -(C5-C10)heteroaryl group and / or -(C3-C7)heterocycloalkyl group being optionally substituted by 1 to 5 atoms / groups chosen from a halogen atom, such as a fluorine atom, a - (C1-C6)alkyl group, a -(C1-C6)alkoxy group, a hydroxyl group, an oxo group, a nitro group and a cyano group; or O N (ii) one of the following reactive groups: a maleimido O group; asubstituted maleimido group such as O ; a haloacetamido R21 p with R21representing a hydrogen atom or a (C1-C6)alkyl group, roup; Cl-; N3-; HO-; HS-; an activated disulfide such as; H2N-; HC≡C- or an activated C≡C such as a cyclooctyne moiety;r reaction substrate such, for instance RCG1 is N3-, a maleimido group, a substituted maleimido groupA-(P)o-L-Ld-RCG1 (I2) wherein - A is as defined in any one of claims 1, 5 and 6; - P represents a -C(O)- group, a -C(O)-O- group, a -S(O2)- group, a -C(O)-C(CH3)2-CH2-O- group, a -C(O)-NH- group,group,group;- o represents an integer from 0 to 1; - L represents a *–(CH2-CH2-O)n-** group in which n represents an integer from 1 to 30, for instance from 8 to 25, such as 8, 12, 16, 20, 23 and 24 , the single asterisk (*) indicating the site of covalent attachment to the P radical if present (that is to say if o is 1) or directly to the A radical if P is not present (that is to say if o is 0) and the double asterisk (**) indicating the site of covalent attachment to the Ld radical; - Ld represents a spacer, for instance a *-(C2-C6)alkyl-** group, a *-(C2-C6)alkyl-NH-C(O)- (C2-C6)alkyl-** group or a *-(C2-C6)alkyl-C(O)-NH-(C2-C6)alkyl-** group, such as a *– (CH2)2-** group, a *-(CH2)2-NH-C(O)-(CH2)2-** group or a *-(CH2)2-C(O)-NH-(CH2)2-** group, the single asterisk (*) indicating the site of covalent attachment to the L radical and the double asterisk (**) indicating the site of covalent attachment to the RCG1 radical; and - RCG1 is as defined in claim 1, for instance RCG1 represents: (i) a RaZa-C(=O)- reactive group for which: Za represents a single bond, -O- or -NH, such as -O-, and Rarepresents a hydrogen atom, a -(C1-C6)alkyl group, a -(C3-C7)cycloalkyl group, a -(C2-C6)alkenyl group, a -(C6-C10)aryl group, a -(C5-C10)heteroaryl group comprising 4 to 9 carbon atoms and 1 to 4 heteroatom(s) selected from oxygen, nitrogen, and sulfur, or a -(C3-C7)heterocycloalkyl group comprising 2 to 6 carbon atoms and 1 to 4 heteroatom(s) selected from oxygen, nitrogen, sulfur, -S(O)- and -SO2-, said -(C6-C10)aryl group, -(C5-C10)heteroaryl group and / or -(C3-C7)heterocycloalkyl group being optionally substituted by 1 to 5 atoms / groups chosen from a halogen atom, such as a fluorine atom, a - (C1-C6)alkyl group, a -(C1-C6)alkoxy group, a hydroxyl group, an oxo group, a nitro group and a cyano group; or (ii) one of the following reactive groups: a maleimidogroup; asubstituted maleimido group such as; a haloacetamido Cl, Br or Igroup with R21representing a hydrogen atom or a (C1-C6)alkyl group, such as a methyl group; Cl-; N3-; HO-; HS-; an activated disulfide such as; H2N-; HC≡C- or an activated C≡C such as a cyclooctyne moiety; aOgroup ; aOgroup; an O-alkyl hydroxylamine or a Pictet-Spengler reaction substrate such,for instance RCG1 is N3-, a maleimido group O , a substituted maleimido groupO , a COOH group, a phenyloxadiazolyl methylsulfone group8. The compounds of formula (I) or a pharmaceutically acceptable salt thereof according to any one of claims 1 to 7, wherein said compound is chosen among:; ;;;;; ;;5, wherein RCG1 is as defined in any one of claims 1, 4 and 7.

9. The compounds of formula (I) or a pharmaceutically acceptable salt thereof according to any one of claims 1 to 8, wherein said compound is chosen among (P1) (4S)-5-[[(2S)-1-[[(2S)-1-[4-[[4-[[4-[(7-amino-2-butyl-4-propan-2- yloxyimidazo[4,5-d]pyridazin-3-yl)methyl]phenyl]methyl]piperazine-1-carbonyl]oxymethyl]anilino]-5-(carbamoylamino)-1-oxopentan-2-yl]amino]-3-methyl-1-oxobutan- 2-yl]amino]-4-[[5-[2-[2-[2-(2-azidoethoxy)ethoxy]ethoxy]ethylamino]-5-oxopentanoyl] amino]-5-oxopentanoic acid ; (P2) (4S)-5-[[(2S)-1-[[(2S)-1-[4-[[trans-4-[(7-amino-2-butyl-4-propan-2- yloxyimidazo[4,5-d]pyridazin-3-yl)methyl]cyclohexyl]methylcarbamoyloxymethyl] anilino]-5-(carbamoylamino)-1-oxopentan-2-yl]amino]-3-methyl-1-oxobutan-2-yl]amino]- 4-[[5-[2-[2-[2-(2-azidoethoxy)ethoxy]ethoxy]ethylamino]-5-oxopentanoyl]amino]-5- oxopentanoic acid ; (P3) (4S)-5-[[(2S)-1-[[(2S)-1-[4-[[4-[[4-[(7-amino-2-butyl-4-propan-2- yloxyimidazo[4,5-d]pyridazin-3-yl)methyl]phenyl]methyl]piperazine-1-carbonyl] oxymethyl]anilino]-1-oxopropan-2-yl]amino]-3-methyl-1-oxobutan-2-yl]amino]-4-[[5-[2- [2-[2-(2-azidoethoxy)ethoxy]ethoxy]ethylamino]-5-oxopentanoyl]amino]-5-oxopentanoic acid ; (P4) (4S)-5-[[(2S)-1-[[(2S)-1-[4-[[trans-4-[(7-amino-2-butyl-4-propan-2- yloxyimidazo[4,5-d]pyridazin-3-yl)methyl]cyclohexyl]methylcarbamoyloxymethyl] anilino]-1-oxopropan-2-yl]amino]-3-methyl-1-oxobutan-2-yl]amino]-4-[[5-[2-[2-[2-(2- azidoethoxy)ethoxy]ethoxy]ethylamino]-5-oxopentanoyl]amino]-5-oxopentanoic acid ; (P5) N'-[(2S)-1-[[(2S)-1-[4-[[4-[(7-amino-2-butyl-4-propan-2-yloxyimidazo [4,5-d]pyridazin-3-yl)methyl]phenyl]methyl]piperazin-1-yl]-1-oxopropan-2-yl]amino]-3- methyl-1-oxobutan-2-yl]-N-[2-[2-[2-(2-azidoethoxy)ethoxy]ethoxy]ethyl]pentanediamide ; (P6) N'-[(2S)-1-[[(2S)-1-[[trans-4-[(7-amino-2-butyl-4-propan-2-yloxyimidazo [4,5-d]pyridazin-3-yl)methyl]cyclohexyl]methylamino]-1-oxopropan-2-yl]amino]-3- methyl-1-oxobutan-2-yl]-N-[2-[2-[2-(2-azidoethoxy)ethoxy]ethoxy]ethyl]pentanediamide; (P7) N'-[(2S)-1-[[(2S)-1-[[trans-4-[(7-amino-2-butyl-4-propan-2-yloxyimidazo [4,5-d]pyridazin-3-yl)methyl]cyclohexyl]methylamino]-1-oxopropan-2-yl]amino]-3- methyl-1-oxobutan-2-yl]-N-[2-[2-[2-[2-[3-(2,5-dioxopyrrol-1-yl)propanoylamino]ethoxy] ethoxy]ethoxy]ethyl]pentanediamide; (P8) N'-[(2S)-1-[[(2S)-1-[4-[[4-[(7-amino-2-butyl-4-propan-2-yloxyimidazo [4,5-d]pyridazin-3-yl)methyl]phenyl]methyl]piperazin-1-yl]-5-(carbamoylamino)-1- oxopentan-2-yl]amino]-3-methyl-1-oxobutan-2-yl]-N-[2-[2-[2-(2-azidoethoxy)ethoxy] ethoxy]ethyl]pentanediamide;(P9) N'-[(2S)-1-[[(2S)-1-[[trans-4-[(7-amino-2-butyl-4-propan-2-yloxyimidazo [4,5-d]pyridazin-3-yl)methyl]cyclohexyl]methylamino]-5-(carbamoylamino)-1-oxopentan- 2-yl]amino]-3-methyl-1-oxobutan-2-yl]-N-[2-[2-[2-(2-azidoethoxy)ethoxy]ethoxy] ethyl]pentanediamide; (P10) N'-[(2S)-1-[[(2S)-1-[[trans-4-[(7-amino-2-butyl-4-propan-2- yloxyimidazo[4,5-d]pyridazin-3-yl)methyl]cyclohexyl]methylamino]-5- (carbamoylamino)-1-oxopentan-2-yl]amino]-3-methyl-1-oxobutan-2-yl]-N-[2-[2-[2-[2-[3- (2,5-dioxopyrrol-1-yl)propanoylamino]ethoxy]ethoxy]ethoxy]ethyl]pentanediamide,2,2,2- trifluoroacetatic acid; (P11) 1-[4-[[4-[(7-amino-2-butyl-4-propan-2-yloxyimidazo[4,5-d]pyridazin-3- yl)methyl]phenyl]methyl]piperazin-1-yl]-3-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2- [2-[2-[2-[2-[2-[2-[2-(2-azidoethoxy)ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy ]ethoxy]ethoxy]ethoxy]ethoxy]propan-1-one ; (P12) N-[[trans-4-[(7-amino-2-butyl-4-propan-2-yloxyimidazo[4,5-d] pyridazin-3-yl)methyl]cyclohexyl]methyl]-3-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2- [2-[2-[2-[2-[2-[2-[2-[2-(2-azidoethoxy)ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy ]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]propenamide; (P13) N-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2- [3-[4-[[4-[(7-amino-2-butyl-4-propan-2-yloxyimidazo[4,5-d]pyridazin-3-yl)methyl] phenyl]methyl]piperazin-1-yl]-3-oxopropoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy ]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethyl]-3-(2,5-dioxopyrrol-1-yl) propanamide,2,2,2-trifluoroacetatic acid; (P14) N-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[3-[[trans-4-[(7-amino-2-butyl-4- propan-2-yloxyimidazo[4,5-d]pyridazin-3-yl)methyl]cyclohexyl]methylamino]-3- oxopropoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]et hoxy]ethyl]-3-(2,5-dioxopyrrol-1-yl)propanamide,2,2,2-trifluoroacetatic acid; (P15) N-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[3-[[trans-4- [(7-amino-2-butyl-4-propan-2-yloxyimidazo[4,5-d]pyridazin-3-yl)methyl]cyclohexyl] methylamino]-3-oxopropoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethyl]- 3-(2,5-dioxopyrrol-1-yl)propanamide,2,2,2-trifluoroacetatic acid; (P16) N-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2- [3-[[trans-4-[(7-amino-2-butyl-4-propan-2-yloxyimidazo[4,5-d]pyridazin-3-yl)methyl] cyclohexyl]methylamino]-3-oxopropoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy ]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethyl]-3-(2,5-dioxopyrrol-1-yl)propanamide,2,2,2- trifluoroacetatic acid; (P17) 3-[[4-[[4-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2- [2-[2-(2-azidoethoxy)ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy ]ethoxy]ethyl]piperazin-1-yl]methyl]phenyl]methyl]-2-butyl-4-propan-2-yloxyimidazo [4,5-d]pyridazin-7-amine ; (P18) 3-[[trans-4-[[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2- [2-[2-[2-(2-azidoethoxy)ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy ]ethoxy]ethoxy]ethylamino]methyl]cyclohexyl]methyl]-2-butyl-4-propan-2-yloxyimidazo [4,5-d]pyridazin-7-amine ; (P19) N-[[trans-4-[(7-amino-2-butyl-4-isopropoxy-imidazo[4,5-d]pyridazin-3- yl)methyl]cyclohexyl]methyl]-3-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-(2- azidoethoxy)ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]et hoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]propenamide; (P20) N-[[trans-4-[(7-amino-2-butyl-4-isopropoxy-imidazo[4,5-d]pyridazin-3- yl)methyl]cyclohexyl]methyl]-3-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-(2- azidoethoxy)ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]et hoxy]ethoxy]ethoxy]ethoxy]ethoxy]propenamide; (P21) N-[[trans-4-[(7-amino-2-butyl-4-isopropoxy-imidazo[4,5-d]pyridazin-3- yl)methyl]cyclohexyl]methyl]-3-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-(2- azidoethoxy)ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]et hoxy]propenamide; (P22) 3-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[3-[[trans-4-[(7-amino-2-butyl-4- isopropoxy-imidazo[4,5-d]pyridazin-3-yl)methyl]cyclohexyl]methylamino]-3-oxo-propoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethox y]propanoic acid; (P23) N-[[trans-4-[(7-amino-2-butyl-4-isopropoxy-imidazo[4,5-d]pyridazin-3- yl)methyl]cyclohexyl]methyl]-3-[2-[2-[2-[2-[2-[2-[2-(2-azidoethoxy)ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]propenamide; (P24) ((4S)-5-[[(2S)-1-[[(2S)-1-[4-[[4-[(7-amino-2-butyl-4-propan-2- yloxyimidazo[4,5-d]pyridazin-3-yl)methyl]phenyl]methylcarbamoyloxymethyl]anilino]-5- (carbamoylamino)-1-oxopentan-2-yl]amino]-3-methyl-1-oxobutan-2-yl]amino]-4-[[5-[2- [2-[2-(2-azidoethoxy)ethoxy]ethoxy]ethylamino]-5-oxopentanoyl]amino]-5-oxopentanoic acid; (P25) (4S)-5-[[(2S)-1-[[(2S)-1-[4-[[4-[(7-amino-2-butyl-4-propan-2- yloxyimidazo[4,5-d]pyridazin-3-yl)methyl]cyclohexyl]carbamoyloxymethyl]anilino]-5- (carbamoylamino)-1-oxopentan-2-yl]amino]-3-methyl-1-oxobutan-2-yl]amino]-4-[[5-[2- [2-[2-(2-azidoethoxy)ethoxy]ethoxy]ethylamino]-5-oxopentanoyl]amino]-5-oxopentanoic acid; (P26) (4S)-5-[[(2S)-1-[[(2S)-1-[4-[[4-[(7-amino-2-butyl-4-propan-2- yloxyimidazo[4,5-d]pyridazin-3-yl)methyl]phenyl]methylcarbamoyloxymethyl]anilino]-1- oxopropan-2-yl]amino]-3-methyl-1-oxobutan-2-yl]amino]-4-[[5-[2-[2-[2-(2-azidoethoxy) ethoxy]ethoxy]ethylamino]-5-oxopentanoyl]amino]-5-oxopentanoic acid; (P27) (4S)-5-[[(2S)-1-[[(2S)-1-[4-[[4-[(7-amino-2-butyl-4-propan-2- yloxyimidazo[4,5-d]pyridazin-3-yl)methyl]cyclohexyl]carbamoyloxymethyl]anilino]-1- oxopropan-2-yl]amino]-3-methyl-1-oxobutan-2-yl]amino]-4-[[5-[2-[2-[2-(2-azidoethoxy) ethoxy]ethoxy]ethylamino]-5-oxopentanoyl]amino]-5-oxopentanoic acid; (P28) N'-[(2S)-1-[[(2S)-1-[[4-[(7-amino-2-butyl-4-propan-2-yloxyimidazo[4,5- d]pyridazin-3-yl)methyl]phenyl]methylamino]-1-oxopropan-2-yl]amino]-3-methyl-1- oxobutan-2-yl]-N-[2-[2-[2-(2-azidoethoxy)ethoxy]ethoxy]ethyl]pentanediamide; (P29) N'-[(2S)-1-[[(2S)-1-[[4-[(7-amino-2-butyl-4-propan-2-yloxyimidazo[4,5- d]pyridazin-3-yl)methyl]cyclohexyl]amino]-1-oxopropan-2-yl]amino]-3-methyl-1- oxobutan-2-yl]-N-[2-[2-[2-(2-azidoethoxy)ethoxy]ethoxy]ethyl]pentanediamide; (P30) N'-[(2S)-1-[[(2S)-1-[[4-[(7-amino-2-butyl-4-propan-2-yloxyimidazo[4,5- d]pyridazin-3-yl)methyl]phenyl]methylamino]-1-oxopropan-2-yl]amino]-3-methyl-1-oxobutan-2-yl]-N-[2-[2-[2-[2-[3-(2,5-dioxopyrrol-1-yl)propanoylamino]ethoxy]ethoxy] ethoxy]ethyl]pentanediamide; (P31) N'-[(2S)-1-[[(2S)-1-[[4-[(7-amino-2-butyl-4-propan-2-yloxyimidazo[4,5- d]pyridazin-3-yl)methyl]phenyl]methylamino]-5-(carbamoylamino)-1-oxopentan-2- yl]amino]-3-methyl-1-oxobutan-2-yl]-N-[2-[2-[2-(2-azidoethoxy)ethoxy]ethoxy]ethyl] pentanediamide; (P32) N'-[(2S)-1-[[(2S)-1-[[4-[(7-amino-2-butyl-4-propan-2-yloxyimidazo[4,5- d]pyridazin-3-yl)methyl]cyclohexyl]amino]-5-(carbamoylamino)-1-oxopentan-2- yl]amino]-3-methyl-1-oxobutan-2-yl]-N-[2-[2-[2-(2-azidoethoxy)ethoxy]ethoxy]ethyl] pentanediamide; 2,2,2-trifluoroacetate; (P33) N'-[(2S)-1-[[(2S)-1-[[4-[(7-amino-2-butyl-4-propan-2-yloxyimidazo[4,5- d]pyridazin-3-yl)methyl]phenyl]methylamino]-5-(carbamoylamino)-1-oxopentan-2- yl]amino]-3-methyl-1-oxobutan-2-yl]-N-[2-[2-[2-[2-[3-(2,5-dioxopyrrol-1-yl)propanoyl amino]ethoxy]ethoxy]ethoxy]ethyl]pentanediamide; 2,2,2-trifluoroacetate; (P34) N'-[(1S)-1-[[(1S)-1-[[4-[(7-amino-2-butyl-4-isopropoxy-imidazo[4,5- d]pyridazin-3-yl)methyl]cyclohexyl]carbamoyl]-4-ureido-butyl]carbamoyl]-2-methyl- propyl]-N-[2-[2-[2-[2-[3-(2,5-dioxopyrrol-1-yl)propanoylamino]ethoxy]ethoxy]ethoxy] ethyl]pentanediamide,2,2,2-trifluoroacetic acid; (P35) (2S)-N-[[4-[(7-amino-2-butyl-4-isopropoxy-imidazo[4,5-d]pyridazin-3- yl)methyl]phenyl]methyl]-2-[[(2S)-2-[3-[2-[2-[2-[3-(2,5-dioxopyrrol-1-yl)propanoyl amino]ethoxy]ethoxy]ethoxy]propanoylamino]-3-methyl-butanoyl]amino]-5-ureido- pentanamide,2,2,2-trifluoroacetic acid; (P36) (2S)-N-[[4-[[7-amino-4-isopropoxy-2-(propylamino)imidazo[4,5-d] pyridazin -3-yl]methyl]phenyl]methyl]-2-[[(2S)-2-[3-[2-[2-[2-[3-(2,5-dioxopyrrol-1- yl)propanoylamino]ethoxy]ethoxy]ethoxy]propanoylamino]-3-methyl-butanoyl]amino]-5- ureido-pentanamide, 2,2,2-trifluoroacetic acid; (P37) N'-[(1S)-1-[[(1S)-1-[3-(4-amino-2-butyl-1-methyl-imidazo[4,5-d] pyridazin-7-yl)-2,5-dihydropyrrole-1-carbonyl]-4-ureido-butyl]carbamoyl]-2-methyl- propyl]-N-[2-[2-[2-[2-[3-(2,5-dioxopyrrol-1-yl)propanoylamino]ethoxy]ethoxy]ethoxy] ethyl]pentanediamide,2,2,2-trifluoroacetic acid; (P38) N'-[(1S)-1-[[(1S)-1-[4-(7-amino-2-butyl-3-methyl-imidazo[4,5-d] pyridazin-4-yl)piperazine-1-carbonyl]-4-ureido-butyl]carbamoyl]-2-methyl-propyl]-N-[2-[2-[2-[2-[3-(2,5-dioxopyrrol-1-yl)propanoylamino]ethoxy]ethoxy]ethoxy]ethyl] pentanediamide,2,2,2-trifluoroacetic acid; (P39) (2S)-N-[5-(7-amino-2-butyl-4-isopropoxy-imidazo[4,5-d]pyridazin-3-yl) pentyl]-2-[[(2S)-2-[3-[2-[2-[2-[3-(2,5-dioxopyrrol-1-yl)propanoylamino]ethoxy]ethoxy] ethoxy]propanoylamino]-3-methyl-butanoyl]amino]-5-ureido-pentanamide,2,2,2-trifluoro acetic acid; (P40) (2S)-N-[4-[(7-amino-2-butyl-4-isopropoxy-imidazo[4,5-d]pyridazin-3- yl)methyl]cyclohexyl]-2-[[(2S)-2-[3-[2-[2-[2-[3-(2,5-dioxopyrrol-1-yl)propanoylamino] ethoxy]ethoxy]ethoxy]propanoylamino]-3-methyl-butanoyl]amino]-5-ureido- pentanamide,2,2,2-trifluoroacetic acid; (P41) N-[[4-[(7-amino-2-butyl-4-propan-2-yloxyimidazo[4,5-d]pyridazin-3- yl)methyl]phenyl]methyl]-3-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2- [2-[2-(2 azidoethoxy)ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy ]ethoxy]ethoxy]propanamide; (P42) N-[4-[(7-amino-2-butyl-4-propan-2-yloxyimidazo[4,5-d]pyridazin-3- yl)methyl]cyclohexyl]-3-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2- [2-(2-azidoethoxy)ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy ]ethoxy]ethoxy]propanamide; (P43) N-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[3-[[4-[(7- amino-2-butyl-4-propan-2-yloxyimidazo[4,5-d]pyridazin-3-yl)methyl]phenyl]methyl amino]-3-oxopropoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethyl]- 3-(2,5-dioxopyrrol-1-yl)propenamide,2,2,2-trifluoroacetic acid; (P44) N-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[3-[[4-[(7- amino-4-isopropoxy-2-propylsulfanyl-imidazo[4,5-d]pyridazin-3-yl)methyl]phenyl] methylamino]-3-oxo-propoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy ]ethyl]-3-(2,5-dioxopyrrol-1-yl)propanamide; (P45) N-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2- [3-[[4-[(7-amino-2-butyl-4-propan-2-yloxyimidazo[4,5-d]pyridazin-3-yl)methyl]phenyl]methylamino]-3-oxopropoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy ]ethoxy]ethoxy]ethoxy]ethyl]-3-(2,5-dioxopyrrol-1-yl)propenamide,2,2,2-trifluoroacetic acid; (P46) 3-[[4-[[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2- [2-(2-azidoethoxy)ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy ]ethoxy]ethylamino]methyl]phenyl]methyl]-2-butyl-4-propan-2-yloxyimidazo[4,5-d] pyridazin-7-amine; (P47) N-[[4-[(7-amino-2-butyl-4-isopropoxy-imidazo[4,5-d]pyridazin-3- yl)methyl]phenyl]methyl]-3-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-(2- azidoethoxy)ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]propanamide; (P48) N-[[4-[(7-amino-2-butyl-4-isopropoxy-imidazo[4,5-d]pyridazin-3- yl)methyl]phenyl]methyl]-3-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-(2-azidoethoxy) ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy ]ethoxy]ethoxy]ethoxy]propanamide; (P49) N-[[4-[(7-amino-2-butyl-4-isopropoxy-imidazo[4,5-d]pyridazin-3- yl)methyl]phenyl]methyl]-3-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-(2-azidoethoxy)ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]propanamide; (P50) 3-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[3-[[4-[(7-amino-2-butyl-4- isopropoxy-imidazo[4,5-d]pyridazin-3-yl)methyl]phenyl]methylamino]-3-oxo-propoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy] propanoic acid; (P51) N-[[4-[(7-amino-2-butyl-4-isopropoxy-imidazo[4,5-d]pyridazin-3- yl)methyl]phenyl]methyl]-3-[2-[2-[2-[2-[2-[2-[2-(2-azidoethoxy)ethoxy]ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]propanamide; (P52) N-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[3-[[4-[(7-amino-2-butyl-4- isopropoxy-imidazo[4,5-d]pyridazin-3-yl)methyl]phenyl]methylamino]-3-oxo- propoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethox y]ethyl]-3-(2,5-dioxopyrrol-1-yl)propanamide;(P53) N-[1-[4-[(7-amino-2-butyl-4-isopropoxy-imidazo[4,5-d]pyridazin-3- yl)methyl]phenyl]-1-methyl-ethyl]-3-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2- [2-(2-azidoethoxy)ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]propanamide; (P54) N-[[4-[(7-amino-2-butyl-4-isopropoxy-imidazo[4,5-d]pyridazin-3- yl)methyl]phenyl]methyl]-3-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-(2- azidoethoxy)ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]-N-methyl- propanamide; (P55) N-[[4-[(7-amino-2-butyl-4-isopropoxy-imidazo[4,5-d]pyridazin-3- yl)methyl]phenyl]methyl]-3-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-(2- azidoethoxy)ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]-2,2-dimethyl- propanamide; (P56) N-[[4-[(7-amino-2-butyl-4-isopropoxy-imidazo[4,5-d]pyridazin-3- yl)methyl]phenyl]methyl]-1-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-(2- azidoethoxy)ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxymethyl]cyclopentaneca rboxamide; (P57) N-[[4-[(7-amino-2-butyl-4-isopropoxy-imidazo[4,5-d]pyridazin-3- yl)methyl]phenyl]methyl]-1-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-(2- azidoethoxy)ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxymethyl]cyclohexanecar boxamide; (P58) 2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-(2- azidoethoxy)ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethyl N-[[4-[(7-amino-2- butyl-4-isopropoxy-imidazo[4,5-d]pyridazin-3-yl)methyl]phenyl]methyl]carbamate; and (P59) 1-[[4-[(7-amino-2-butyl-4-isopropoxy-imidazo[4,5-d]pyridazin-3- yl)methyl]phenyl]methyl]-3-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[2-(2- azidoethoxy)ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy] ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethyl]urea.

10. A compound of formula (II) or a pharmaceutically acceptable salt thereof: A-L1-G-BA (II) wherein: A is as defined in anyone of claims 1, 5, and 6 and L1 is as defined in anyone of claims 1, 2, 3, and 5; BA represents a binding agent for instance a protein, a polypeptide, a ligand, a peptide, an oligonucleotide or an oligosaccharide, for instance BA is a targeting agent for instance a cell-binding agent such as an antibody, such as a monoclonal antibody or a VHH antibody; G represents the product of reaction between RCG1 as defined in anyone of claims 1 and 4 and RCG2, a reactive group present on the binding agent, for instance G is selected from the group consisting of : ;for instance, the left side of the G groups being linked to the binding agent BA, for instance an antibody (Ab), and the right side of the G groups being linked to L1, for.

11. The compounds of formula (II) or a pharmaceutically acceptable salt thereof according to claim 10, wherein said compound is chosen among a compound of formula (II1) and a compound of formula (II2): A-(La)m-(AA)w-(Lb)p-Lc-Ld’-G-BA (II1) wherein: A is as defined in any one of claims 1, 5 and 6, La, m, (AA)w, AA, w, Lb, p, Lc and Ld’ are as defined in claim 7, and BA is as defined in claim 10; G represents the product of reaction between RCG1 as defined in claim 1 or claim 4 and RCG2, a reactive group present on the binding agent as defined in claim 10 for instance an antibody, for instance G is selected from the group consisting of :;;for instance, the left side of the G groups being linked to BA and the right side of the G groups being linked to Ld’, for instance G represents the following groups:A-(P)o-L-Ld-G-BA (II2) wherein:A is as defined in any one of claims 1, 5 and 6, and P, o, L and Ld are as defined in claim 7, and BA is as defined in claim 10; G represents the product of reaction between RCG1 as defined in claim 1 or in claim 4 and RCG2, a reactive group present on the binding agent as defined in claim 10 for instance an antibody, for instance G is selected from the group consisting of: ;for instance, the left side of the G groups being linked to BA and the right side of the G groups being linked to Ld, for instance G represents the following groups:.

12. The compound of formula (II) or a pharmaceutically acceptable salt thereof according to claim 10 or 11, wherein the binding agent BA is an antibody Ab, for instance a monoclonal antibody or a VHH antibody.

13. The compound of formula (II) or a pharmaceutically acceptable salt thereof according to any one of claims 10 to 12, wherein: - when L1 is -(La)m-(AA)w-(Lb)p-Lc-Ld’-, L1 is selected from the group consisting of: *-C(O)-O-CH2-para-phenyl-NH-Cit-Val-Glu-C(O)-(CH2)3-C(O)-NH-(CH2- CH2-O)3-(CH2)2-** ; *-C(O)-O-CH2-para-phenyl-NH-Ala-Val-Glu-C(O)-(CH2)3-C(O)-NH-(CH2- CH2-O)3-(CH2)2-**; *-Cit-Val-C(O)-(CH2-CH2-O)3-(CH2)2-NH-C(O)-(CH2)2-**; *-Cit-Val-C(O)-(CH2)3-C(O)-NH-(CH2-CH2-O)3-(CH2)2-**; *-Ala-Val-C(O)-(CH2)3-C(O)-NH-(CH2-CH2-O)3-(CH2)2-**; *-C(O)-O-CH2-para-phenyl-NH-Cit-Val-Glu-C(O)-(CH2)3-C(O)-NH-(CH2- CH2-O)3-(CH2)2-NH-C(O)-(CH2)2-** ; *-C(O)-O-CH2-para-phenyl-NH-Ala-Val-Glu--C(O)-(CH2)3-C(O)-NH-(CH2- CH2-O)3-(CH2)2-NH-C(O)-(CH2)2-**;*-Cit-Val-C(O)-(CH2)3-C(O)-NH-(CH2-CH2-O)3-(CH2)2-NH-C(O)-(CH2)2-**; *-Ala-Val-C(O)-(CH2)3-C(O)-NH-(CH2-CH2-O)3-(CH2)2-NH-C(O)-(CH2)2-**, the single asterisk (*) indicating the site of covalent attachment to the A drug unit radical and the double asterisk (**) indicating the site of covalent attachment to the G radical belonging to the -G-BA group; or - when L1 is -(P)o-L-Ld-, L1 is selected from the group consisting of: *-C(O)-(CH2-CH2-O)24-CH2-CH2-**; *-(CH2-CH2-O)23-CH2-CH2-**; *-C(O)-(CH2-CH2-O)20-CH2-CH2-**; *-C(O)-(CH2-CH2-O)16-CH2-CH2-**; *-C(O)-(CH2-CH2-O)12-CH2-CH2-**; *-C(O)-(CH2-CH2-O)8-CH2-CH2-**; *-C(O)-C(CH3)2-CH2-O-(CH2-CH2-O)20-CH2-CH2-**; *-C(O)-O-(CH2-CH2-O)20-CH2-CH2-**;*-C(O)-(CH2-CH2-O)24-CH2-CH2-NH-C(O)-CH2-CH2-**; *-C(O)-(CH2-CH2-O)20-CH2-CH2-NH-C(O)-CH2-CH2-**; and *-C(O)-(CH2-CH2-O)12-CH2-CH2-NH-C(O)-CH2-CH2-**; the single asterisk (*) indicating the site of covalent attachment to the A drug unit radical and the double asterisk (**) indicating the site of covalent attachment to the G radical belonging to the -G-BA group.

14. The compound of formula (II) or a pharmaceutically acceptable salt thereof according to any one of claims 10 to 12, wherein said compound is chosen among:£LV;;;, wherein Ab represents an antibody, for instance a monoclonal antibody or a VHH antibody.

15. The compound of formula (II) or a pharmaceutically acceptable salt thereof according to any one of claims 10 to 12, wherein RCG2 is selected from the group consisting of: (i) a ε-amino group (ε-NH2 group) borne by the side chain of a lysine residue that is present at the surface of the binding agent as defined in claim 10 for instance of the antibody; (ii) an α-amino group (α-NH2 group) of an N-terminal amino acid of a heavy chain or a light chain of the binding agent as defined in claim 10 for instance of the antibody; (iii) the saccharide groups of the hinge region; (iv) a thiol (a -SH group) of a cysteine residue generated by reducing an intra-chain disulfide bond of the binding agent as defined in claim 10 for instance of the antibody or a -SH group of an engineered cysteine residue of the binding agent as defined in claim 10 for instance of the antibody; (v) an amide group (a -C(O)NH2 group) borne by the side chains of a glutamine residue that is present at the surface of the binding agent as defined in claim 10 for instance of the antibody; (vi) an aldehyde group (a -C(O)H group) introduced using formylglycine generating enzyme; and(vii) RCG2 group, optionally introduced by means of a modifying agent.

16. The compound of formula (II) or a pharmaceutically acceptable salt thereof according to any one of claims 10 to 15, wherein- when RCG1 represents a N-hydroxysuccinimidyl ester, RCG2 represents a -Nth group;- when RCG1 represents a maleimido function, a haloacetamido function, a chlorine atom or an activated disulfide function, RCG2 represents a -SH group;- when RCG1 represents a -N3 group, RCG2 represents a HOC- or an activated C=C function such as a cyclooctyne moiety;- when RCG1 represents a -OH or -NH2 group, RCG2 represents a carboxylic acid or amide function;- when RCG1 represents a -SH group, RCG2 represents a maleimido function, a haloacetamido function or an activated disulfide function;- when RCG1 represents a HOC- function or an activated C=C function, RCG2 represents a -N3 group;- when RCG1 represents a O-alkyl hydroxylamine function or a Pictet-Spengler reaction substrate, RCG2 represents an aldehyde or a ketone function.

17. The compounds of formula (I) according to any one of claims 1 to 9 or the compounds of formula (II) according to any one of claims 10 to 16, wherein the drug unit A of formula (A) as defined in claim 1 or claim 6, or of formula (Al) or of formula (A2) as defined in claim 5 or claim 6 is a TLR7 agonist.

18. The compounds of formula (I) according to any one of claims 1 to 9 or the compounds of formula (II) according to any one of claims 10 to 16, wherein the drug unit A of formula (A) as defined in claim 1 or claim 6, or of formula (Al) or of formula (A2) as defined in claim 5 or claim 6 is a TLR7 / 8 agonist.

19. The compounds of formula (I) according to any one of claims 1 to 9, 17 and 18, or of formula (II) according to any one of claims 10 to 18, wherein the drug unit A is further low or non - cell permeable.

20. The compounds of formula (I) or of formula (II) according to claim 19, wherein the low or non - cell permeable drug unit A is defined by a PAMPA below 25.

21. The compounds of formula (II) according to claim 7 or of formula (III) according to claim 11, wherein the amino acid sequence (AA)w comprises a citrulline.

22. The compounds of formula (II) or of formula (III) according to claim 21, wherein the amino acid sequence (AA)w is Val-Cit.

23. The compounds of formula (II), (III) or (112) according to any one of claims 10 to 22, wherein RCG2 is a reactive group of a cysteine engineered amino acid residue of an antibody.

24. The compounds of formula (II), (III) or (112) according to claim 23, wherein the cysteine engineered amino acid residue is at least one position according to the numbering of the EU numbering index, selected from an interchain cysteine, 118, 152, 360, 274, 414 of the heavy chain constant (CH) domain.

25. The compounds of formula (II), (III) or (112) according to claim 24, wherein the cysteine engineered amino acid residue is at position 360 of the heavy chain constant (CH) domain according to the numbering of the EU numbering index.

26. A pharmaceutical composition comprising a compound of formula (II), (III) or (112) according to any one of claims 10 to 25, and at least one pharmaceutically acceptable excipient.

27. A compound of formula (II), (III) or (112) according to any one of claims 10 to 25, for use as a medicine.

28. A compound of formula (II), (III) or (112) according to any one of claims 10 to 25, for use to induce high amount of immune stimulating cytokines with low or no pro- inflammatory cytokines.

29. A compound of formula (II), (III) or (112) according to any one of claims 10 to 25, for use to stimulate the cytokine induction of IFNa and IP 10 with low or no stimulation of IL6 and TNFa.

30. A compound of formula (II), (III) or (112) according to claim 29, wherein IFNa / TNFa ratio is higher than 1.

31. A compound of formula (II), (III) or (112) according to any one of claims 10 to 25, for use in the prevention and / or in the treatment of a disease or a disorder that may benefit of an activation of the immune system, for instance for use in the prevention and / or treatment of a cell-proliferative disease, a cancer, a chronic myelogenous, a hairy cell leukemia, a dermatological disease such as a skin lesion or a skin cancer for example an external genital and perianal warts / condyloma acuminate, a genital herpes, an actinic keratosis, a basal cell carcinoma, or a cutaneous T-cell lymphoma, an autoimmune disease, an inflammatory disease, a respiratory disease, a sepsis, an allergy for example an allergic rhinitis or a respiratory allergy, an asthma, a graft rejection, a graft-versus-host disease, and an immunodeficiency, for instance in the prevention and / or in the treatment of cancers.

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