Cleavable conjugates of transthyretin ligand and uses thereof

Abstract

Provided herein are conjugates of formula (I) or a pharmaceutically acceptable salt thereof, wherein T, L, LB, E, and D1 are as defined elsewhere herein. Also provided are methods of preparing compound of formula (I).

Description

[0001] Attorney Docket No. 330272000240CLEAVABLE CONJUGATES OF TRANSTHYRETIN LIGAND AND USES THEREOF CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Application No.63 / 572,081filed March 29, 2024, and U.S. Provisional Application No. 63 / 748,386 filed January 22,2025, the entire contents of each of which are incorporated herein by reference.FIELD OF THE INVENTION Aspects of the invention generally relate to a delivery system for active agents havinga ligand (binder) that is selective for transthyretin (TTR) in the serum of a subject; and acleavable linker configured for operatively attaching the ligand covalently to a drug toincrease the plasma circulation time and duration of the drug in the serum. BACKGROUND OF THE INVENTION The poor pharmacokinetic profile of many drugs represents a major challenge in theircontinued development. This problem, in particular, has limited the ability of drugs to reachtheir tremendous therapeutic potential. In particular, the half-life of many drugs in the bloodserum of a subject is of serious concern. Short half-life of a drug is usually due to (i)enzymatic degradation by serum proteases and / or (ii) fast renal clearance due to themolecular weight cutoff for peptides and proteins to be cleared through glomerular filtrationbeing relatively high at approximately 30 kilodaltons. Those of skill in the art recognize thatthe short in vivo half-life of numerous drug candidates has limited their clinical potential byincreasing the size and frequencies of doses needed to achieve the desired results, for example. Accordingly, the art will appreciate having a delivery system that (i) improves the duration of action and plasma circulation of active drugs; (ii) avoids steric hindrance problems that affect binding affinity and potency of the active agents; (iii) avoids the renal tubular vacuolation caused by PEGylation; (iv) avoids the generation of antibodies that create immune response problems; and (v) has low manufacturing costs. BRIEF SUMMARY OF THE INVENTION It has been surprisingly discovered that the duration of action (DOA) of a drug can besignificantly extended by covalently attaching the drug to a ligand that is selective fortransthyretin (TTR) through a cleavable linker. Accordingly, the disclosure relates to aAttorney Docket No. 330272000240fundamentally new prodrug approach for enhancing the plasma circulation and DOA of drugswithout affecting their biological activity.In one aspect, provided herein is a conjugate of formula (I): (I) or a pharmaceutically acceptable salt thereof, wherein: Tis a ligand selective for transthyretin TTR;L is a linker; LBis absent or a click product formed via a Click reaction between a first Click handle and a second click handle; E is a cleavable ester; and D1is a drug moiety. In some embodiments, the cleavable ester moiety (E) of the conjugate of formula (I) comprises an aromatic ring. In some embodiments, the aromatic ring can be optionally substituted with one or more substituents as set forth herein. In some embodiments, para- amino benzoic acid (PABA) is used as a basic building block for forming an ester with a drug. In some embodiments, para-hydroxybenzoic benzoic acid (PHBA) is used as a basicbuilding block for forming an ester with a drug moiety. In some embodiments, substitutedPABA is used as a basic building block for forming an ester with a drug. In someembodiments, the aromatic ester group (e.g., PABA or PHBA) of the conjugate of formula (I)is hydrolyzed to a greater extent by carboxylesterase 2 (CES2) than by carboxylesterase 1(CES1). In some embodiments, the aromatic ester group (e.g., PABA or PHBA) of theconjugate of formula (I) is hydrolyzed by CES2 but only to a minimal extent by CES1. Insome embodiments, the aromatic ester group (e.g., PABA) of the conjugate of formula (I) isfully resistant to CES1. Surprisingly, in some embodiments, it has been discovered that the TTR ligand influences the extent of hydrolysis and carboxylesterase selectivity of aromatic ester groups (e.g., PABA or PHBA groups) in the conjugate. For instance, in certain embodiments, TTRligands (binders) of a conjugate of formula (I) are capable of increasing CES2 selectivity toconjugates of formula (I). Such CES2 selectivity provides for a more controlled or extendedAttorney Docket No. 330272000240release of the drug from the conjugate. Additionally, the rate of hydrolysis can be effectivelytuned (e.g., increased or decreased) by particular substitutions on the aromatic ester group (e.g., PABA or PHBA group) of the conjugate. In some embodiments, the conjugate of formula (I) includes the following ester moiety: wherein represents the point of attachment to L or LB. In some embodiments, the conjugate of formula (I) includes the following ester moiety: wherein represents the point of attachment to L or LB, R1x is H, F, Cl, NO2, CF3, or OMe,and R1yis H or Me. In some embodiments, R1xis H or Me and R1yis H, F, Cl, Br, NO2, CF3, Me, or OMe. In some embodiments, R1xis H and R1yis Me. In some embodiments, the conjugate of formula (I) includes the following ester moiety:Attorney Docket No. 330272000240 wherein represents the point of attachment to L or LB. In some embodiments, the conjugate of formula (I) includes the following ester moiety: wherein represents the point of attachment to L or LB. In some embodiments, the conjugate of formula (I) includes the following ester moiety: wherein represents the point of attachment to L or LB, R1x is H, F, Cl, NO2, CF3, or OMe,and R1yis H or Me. In some embodiments, R1xis H or Me and R1yis H, F, Cl, Br, NO2, CF3, Me, or OMe. In some embodiments, R1xis H and R1yis Me. In some embodiments, the ligand selective for transthyretin TTR (T) is a compound ofFormula (E)Attorney Docket No. 330272000240 or a pharmaceutically acceptable salt thereof, wherein the variables R1, R2, R3, Ra, Rb, X anda are defined herein. In some embodiments, a conjugate of formula (I) comprises a ligand offormula (E) and the aromatic ester group (e.g., PABA or PHBA). In some embodiments, thecompound of formula (E) increases CES2 selectivity to aromatic ester group (e.g., PABA orPHBA) in vivo. In one embodiment, provided herein is a conjugate of formula (II): or a pharmaceutically acceptable salt thereof, wherein: each R1is independently halo or C1-4alkyl; m is 0, 1, 2, or 3; R2is H or C1-4alkyl;X1 is -O- or -NRx-;n is 0, 1, 2, 3, or 4 R3is H or C1-4alkyl; R4is H or C1-4alkyl;Attorney Docket No. 330272000240R5is H or C1-4alkyl; Rxis H or C1-4alkyl; L is a linker; Y1is a bond or C1-4alkylene; Y2is NR6, O or S; R6is H or C1-4alkyl;each R7 is independently selected from the group consisting of hydrogen, halogen atoms(e.g., Cl, Br or F), NO2, CF3, OMe, O(C1-4alkyl), hydroxy, -OCF3, -NH2, -NHC1-4alkyl, - N(C1-4 alkyl)2, -CONH2, -CONHC1-4 alkyl, -CON(C1-4 alkyl)2, -NHCOC1-4 alkyl, C1-6 alkyl,C1-6 alkoxy and C3-6 cycloalkyl;p is 0, 1, 2, or 3; andD1 is a drug moiety.Any embodiments provided herein of a conjugate of formula (I) or formula (II), orpharmaceutically acceptable salts thereof, apply where applicable to any other formuladetailed herein, the same as if each and every embodiment were specifically and individually listed. Thus, it is understood and described that each embodiment provided herein of aconjugate of formula (I) or formula (II) apply to conjugates of formulas (III)-(XII) or (III’)-(VIII’), or variations thereof, or pharmaceutically acceptable salts thereof, the same as if eachand every embodiment were specifically and individually listed. It is also understood anddescribed that all such embodiments may be used in any of the pharmaceutical compositions, methods, kits, uses, or other aspects detailed herein. In one aspect, provided herein are methods of increasing the plasma circulation timeand DOA of a drug, said method comprising administering to a subject (e.g., a humanpatient) a therapeutically effective amount of a conjugate of the disclosure (e.g., conjugate offormula (I) or formula (II)). In some embodiments, administering the conjugate of thedisclosure (e.g., conjugate of formula (I) or formula (II)) reduces the immunogenicity of theactive agent relative to administering the drug alone in free form (nonconjugated form).In some embodiments, a conjugate of the disclosure is administered parenterally to asubject in need thereof. For instance, a conjugate of the disclosure can be administeredAttorney Docket No. 330272000240subcutaneously, intravenously, intramuscularly or intrathecally. In other embodiments, the conjugates of the disclosure are administered orally. In some embodiments where a conjugate of the disclosure is administered subcutaneously, the conjugates form a depot in the subcutaneous tissue. In some such embodiments, the solubility of the conjugate at physiological pH is less than the solubility of the unconjugated drug at physiological pH. As a result, the slow dissolution of the conjugate relative to the unconjugated drug slows the release of the drug into the systemic circulation, hence extending the duration of action of the drug. Subsequent binding of the conjugate toTTR in the systemic circulation further extends the duration of action of the drug. As shownin Example 11, in some embodiments, the ability of the conjugates to form depots at attributed to the zwitterionic nature of the conjugates at physiological pH. In some embodiments, despite a reduction of the solubility of the conjugate relative to the unconjugated drug, the conjugate is rapidly absorbed, resulting in a fast onset of action. Accordingly, conjugates of the disclosure provide drugs with both rapid onset and extended duration of action. Conjugates of the disclosure, particularly conjugates of formula (II), show enhancedadsorption from tissue, particularly subcutaneous tissue, owing, in part, to the balancedhydrophilicity of the TTR selective ligand. Following adsorption from tissue (e.g.,subcutaneous tissue), reversible binding of the TTR selective ligand of the conjugate resultsin significantly extended duration of action of the active agent. As set forth herein, cleavageof the linker between the TTR selective ligand and the active agent results in release of theactive agent, hence allowing the active agent to exert its pharmacological effect. Moreover, it has been discovered that release of the active agent can be effectively controlled by proper selection of a cleavable moiety in the conjugate. For instance, particularester moieties, as described herein, hydrolyze slowly following administration, therebyreleasing the active agent in a controlled manner for an extended period of time. The slower hydrolysis and the high degree of binding to TTR effectively extend the plasma circulation time and duration of action (DOA). Therefore, the conjugates of the disclosure manifest several beneficial properties for a new prodrug approach. The balanced hydrophilicity of the conjugates allows for rapid adsorption into the blood from the tissue, the binding of TTR extends the plasma circulation time, and the cleavable moiety allows for modulation of release of the drug. The desired rateAttorney Docket No. 330272000240of release of a particular active drug from a conjugate of the disclosure will vary from oneactive agent to another.In some embodiments, D1is a peptide. As shown in the examples, conjugates of the disclosure comprising peptides as the active drug display markedly increased half-life duration of action relative to the free peptide drug, hence enabling reduced dosing of the peptide drugs. In some embodiments, the peptide is RGK-MCA. In some embodiments, the peptide is Neurotensin. In some embodiments, the peptide is Gonadotropin-releasing hormone (GnRH). In some embodiments, the peptide is GIP (1-42), human peptide. In someembodiments, the peptide is D6-GnRH. In some embodiments, the peptide is insulin. Insome embodiments, the peptide is teriparatide. In some embodiments, the peptide iscalcitronin salmon. In some embodiments, the peptide is ipamorelin. In some embodiments, the peptide is vasopressin. In some embodiments, the peptide is glucagon. In some embodiments, the peptide is aclerastide. In some embodiments, the peptide is goserelin. In some embodiments, the peptide is leuprolide. In some embodiments, the peptide is teriparatide. In some embodiments, the peptide is lixisenatide. In some embodiments, the peptide is desmopressin. In some embodiments, the peptide is oxytocin. In some embodiments, the peptide is corticotropin. In some embodiments, the peptide is sermorelin. In some embodiments, the peptide is bremelanotide. In some embodiments, the peptide is abaloparatide. In some embodiments, the peptide is deslorelin. In some embodiments, the peptide drug is a glucagon-like-peptide-1 (GLP-1) receptor agonist used to treat obesity and / or diabetes. In some such embodiments the peptide drug is semaglutide, liraglutide, dulaglutide, albiglutide, or exenatide. Owing to the dramatic extension of duration of action of peptide drugs when incorporated into the conjugates of the disclosure, the GLP-1 agonist conjugates can be administered on a reduced dosing schedule, such as once weekly, once biweekly, once every three weeks, or once monthly. In some embodiments, the peptide drug is a glucagon-like-peptide-1 (GLP-1) and GIP(glucose-dependent insulinotropic polypeptide) receptor agonist used to treat obesity and / ordiabetes. In some such embodiments, the peptide drug is tirzepatide. Owing to the dramatic extension of duration of action of peptide drugs when incorporated into the conjugates of the disclosure, the GLP-1 / GIP agonist conjugates can be administered on a reduced dosing schedule, such as once weekly, once biweekly, once every three weeks, or once monthly.Attorney Docket No. 330272000240In some embodiments, the peptide is an endogenous opioid peptide. In some such embodiments, the peptide is endomorphin-1 or endomorphin-2. In other embodiments, the peptide is dermorphin. In some embodiments, the active drug (D1) delivered by a conjugate of the disclosure is a small molecule, a nucleotide, an oligonucleotide, a polynucleotide, an amino acid, anoligopeptide, a polypeptides, or a protein. Active drugs, include. can include, but are notlimited to, antiproliferatives, antineoplastics, antimitotics, anti-inflammatories, antiplatelets, anticoagulants, antifibrins, antithrombins, antibiotics, antiallergics, antioxidants. In some embodiments, D1 is a peptide, an oligopeptide, a polypeptide, a protein, anantibody, an oligonucleotide, a polynucleotide, a virus-like particle, a small molecule, anoligosaccharide, or an imaging agent. In some embodiments, D1is a protein. In some embodiments, D1is an antibody. In some embodiments, D1 is a cytokine. In some embodiments, the cytokine isInterleukin-2 (IL-2). In some embodiments, the cytokine is mutated IL-2, such as a cytokine described in US 9,206,943. In some embodiments, the cytokine is Interleukin-15 (IL-15). Insome embodiments, the cytokine is mutated IL-15. In one such embodiment, the IL-15 is IL-15[N27D]. In some embodiments, the cytokine is Interleukin-7 (IL-7). In some embodiments, the cytokine is Interleukin-9 (IL-9). In some embodiments, the cytokine is Interleukin-10 (IL-10). In some embodiments, the cytokine is Interleukin-21 (IL-21). In some embodiments, the cytokine is Interleukin-10 (IL-10). In some embodiments, D1 is an anti-cancer agent. In some such embodiments, D1 isSN-38. In some such embodiments, D1 is monomethyl auristatin E. In some suchembodiments, D1 is capecitabine. In some such embodiments, D1 is irinotecan. In some suchembodiments, D1 is trifluridine. In some such embodiments, D1 is doxorubicin. In somesuch embodiments, D1 is docetaxel. In some such embodiments, D1 is infigratinib.In some embodiments, D1 is an opioid antagonist. In some embodiments, the opioidantagonist is naloxone, nalmefene, naltrexone, methylnaltrexone, nalbuphine, or nalorphine. In some embodiments, D1 is an opioid agonist. In some embodiments, the opioidagonist is morphine, oxycodone, hydromorphone, or methadone.Attorney Docket No. 330272000240In some embodiments, following the administration of a conjugate of the disclosure (e.g., a conjugate of formula (I) or formula (II)), the plasma circulation and the duration ofaction (DOA) of the drug is at least 12 hours. In some such embodiments, following theadministration of a conjugate the disclosure (e.g., a conjugate of formula (I) or formula (II)), the DOA of the drug is at least 20 hours. In some such embodiments, following theadministration of a conjugate of the disclosure, the DOA of drug is at least 96 hours. In someembodiments, following the administration of a conjugate of the disclosure, the DOA of thedrug is at least 1 week. In some embodiments, following the administration of a conjugate ofthe disclosure, the DOA of the drug is at least 2 weeks. In some embodiments, following theadministration of a conjugate of the disclosure, the DOA of the drug is at least 1 month.In some embodiments, the conjugates disclosed herein can provide a controlled and / orextended release of a drug. In some such embodiments, slow release of the drug from theconjugate can be administered safely. In some embodiments, a conjugate of the disclosure is administered subcutaneously toa human subject at a dose of from about 0.005 mg / kg to about 40 mg / kg. In someembodiments. a conjugate of the disclosure is administered subcutaneously to a humansubject at a dose of from about 0.01 mg / kg to about 40 mg / kg. In some embodiments. aconjugate of the disclosure is administered subcutaneously to a human subject at a dose offrom about 10 mg / kg to about 40 mg / kg. In some embodiments. a conjugate of the disclosureis administered subcutaneously to a human subject at a dose of from about 10 mg / kg to about20 mg / kg.BRIEF DESCRIPTION OF FIGURES Fig. 1 shows that prodrugs of the disclosure bind selectively to TTR in human plasmaand release naloxone, other drugs, and peptides in rat plasma. Fig. 1a, Chemical structures ofnaloxone, AG10-L, and prodrugs. AG10-L-E1-Naloxone is an alkyl ester prodrug. AG10-L-E2-Naloxone is a PABA aryl ester prodrug. C12-E2-Naloxone is a control fatty acid-conjugated PABA aryl ester prodrug. A number of other PABA-based prodrugs of smallmolecules and peptides are shown. Fig. 1b, Aqueous solubility of compounds (incubated at100 μM) in potassium phosphate buffer (pH 7.4) and Log D7.4 values of test compounds atphysiological pH of 7.4 in potassium phosphate buffer (pH 7.4) and n-octanol. Fig. 1c,Binding affinity of compounds to purified human TTR in buffer was evaluated usingfluorescence polarization assay. Compounds were tested at concentration range of 0.01 μM toAttorney Docket No. 33027200024020 μM). The IC50 values were used to calculate the binding constant (Kd) using the Cheng–Prusoff equation. Data represent the mean ± s.d. (n = 3 independent replicates). Fig. 1d,Evaluation of the binding selectivity of compounds (tested at 10 μM) for TTR in humanserum (concentration ~5 μM). The modification of TTR in human serum by covalent FPEprobe was monitored for 6 h in the presence of FPE probe alone (DMSO) or probe and TTRligands. Ligands that display lower fluorescence of FPE probe have higher binding selectivityto TTR. Fig. 1e, The 3 hr readings, relative to probe alone, were used to calculate the percentoccupancy. Data represent the mean ± s.d. (n = 4 independent replicates). Fig. 1f, Plasmastability of prodrugs AG10-L-E1-Naloxone, AG10-L-E2-Naloxone, and C12-E2-Naloxone(tested at 5 μM) in human and Fig. 1g, rat plasma. The concentration remaining in respectivemedia was determined at the indicated timepoints using HPLC. Bar graphs represent themean of % compound remaining ± s.d. (n = 3 independent replicates).Fig. 2 shows that AG10-L-E2-Naloxone is bioactivated by CES2 enzyme hydrolysis.Fig. 2a, Chemical structures of AG10-L-E2-Naloxone and its hydrolysis products, AG10-L-E2-COOH and naloxone. Fig. 2b, Docking study of AG10-L-E2-Naloxone to both humanTTR (pdb id: 4HIQ)6and mouse CES2 enzyme (pdb id: 8AXC). The linker length for AG10-L-E2-Naloxone (~29 Å) is long enough to allow AG10-L-E2-Naloxone to bind to both CES2and TTR simultaneously. Fig. 2c, AG10-L-E2-Naloxone is hydrolyzed by purified CES2 inbuffer but not with CES1. Fig. 2d, Metabolic bioactivation of AG10-L-E2-Naloxone in livermicrosomes from human (HLM), rat (RLM), and monkey (MLM). HLM effectively produced naloxone from AG10-L-E2-Naloxone. The selective CES2 inhibitor, loperamide, significantly decreased the amount of naloxone released while there was no effect of the CES1 inhibitor, digitonin. The concentration of naloxone released from AG10-L-E2-Naloxone in HLM, MLM, and RLM was determined using validated LC-MS / MS method.Fig. 2e, Stability of AG10-L-E2-Naloxone (tested at 5 μM) in rat plasma in the absence andpresence of CES2 inhibitor, loperamide, and CES1 inhibitor, digitonin. Fig. 2f, Stability ofAG10-L-E2-Naloxone (tested at 5 μM) in monkey plasma (no CES1 or CES2 in plasma) andrabbit plasma (high abundance of CES1 and CES2 in plasma). The concentration remainingin respective media was determined at the indicated timepoints using HPLC. Bar graphs forFig. 2c through Fig. 2f represent the mean of % compound remaining ± s.d. (n = 3independent replicates).Fig. 3 shows pharmacokinetic / Pharmacodynamic evaluation of AG10-L-E2-Naloxonein rats. Fig. 3a, A single subcutaneous (s.c.) injection of 15 µmol kg-1 of test compoundAttorney Docket No. 330272000240(equivalent to 5 mg kg-1 of naloxone and 15.8 mg kg-1 of AG10-L-E2-Naloxone) wereadministered to male Sprague Dawley rats (n = 3 for each group). The concentration of thetest compounds in plasma was determined at different time points and expressed as means ±s.d. of three biological replicates. Fig. 3b, Concentration of brain and Fig. 3c, cerebrospinalfluid (CSF) naloxone (freely administered) and naloxone released from AG10-L-E2-Naloxone. Male Sprague Dawley rats (n = 3 for each group) were dosed with a singlesubcutaneous (s.c.) injection of 15 µmol kg-1 of test compound (equivalent to 5 mg kg-1 ofnaloxone and 15.8 mg kg-1 of AG10-L-E2-Naloxone). The concentration of naloxone in braintissue and CSF measured at 10 min and 30 min after dosing. Bar graphs show the respectivemean ±s.d. of three biological replicates. Fig. 3d, Mortality data for morphine overdose andrescue by antagonists in male Sprague Dawley rats (n = 9 biological replicates for eachgroup). Dosing schedule of morphine (s.c. doses of 100 mg kg-1 at 0 hr and 50 mg kg-1 at 6 hr)and antagonists (naloxone and AG10-L1-E2-Naloxone; 15 µmol kg-1; single s.c. dose at 5min). Fig.3e, Mortality data for fentanyl overdose and rescue by antagonists in male SpragueDawley rats (n = 8 biological replicates for each group). Dosing schedule of fentanyl (s.c.doses of 3 mg kg-1 at 0 hr and 3 mg kg-1 at 6 hr) and antagonists (naloxone and AG10-L1-E2-Naloxone; 15 µmol kg-1; single s.c. dose at 5 min). Fig. 3f through Fig. 3i, Reversal offentanyl OIRD in male Sprague Dawley rats (n= 6 per group) by naloxone, AG10-L-E1-Naloxone, and AG10-L-E2-Naloxone, and C12-E2-Naloxone (15 µmol kg-1; single s.c. dosesat 1 min). Fig. 3f, Dosing schedule of fentanyl and antagonists. Reversal of OIRD isrepresented by Minute Volume relative to control (Minute Volume of rats before fentanylinjection was considered to be the baseline). Minute Volume (mean ± s.d.; n= 6 biologicalreplicates per group) is plotted as a function of time after Fig. 3g, first dose of fentanyl andantagonists, Fig. 3h, second fentanyl dose after 6 hr, and Fig. 3i, third fentanyl dose after 24hr. Animals were monitored in plethysmography chamber for 90 min after each fentanyldose. Data were analyzed using the GraphPad Prism V9.3.1.471 software (La Jolla, CA, USA). Fig. 4 shows reversal of fentanyl OIRD by naloxone, nalmefene, and AG10-L-E2-Naloxone. Fig. 4a. A single subcutaneous (s.c.) injection of 60 µmol kg-1 of test compound(equivalent to 20 mg kg-1 of naloxone and 63 mg kg-1 of AG10-L-E2-Naloxone) wereadministered to male Sprague Dawley rats (n = 3 for each group). The concentration of thetest compounds in plasma was determined at different time points and expressed as means ±s.d. of three biological replicates. Fig. 4b, Dosing schedule of fentanyl and antagonists (60µmol kg-1). Reversal of OIRD is represented by Minute Volume relative to control (MinuteAttorney Docket No. 330272000240Volume of rats before fentanyl injection was considered to be the baseline). Minute Volume(mean ± s.d.; n= 6 biological replicates per group) is plotted as a function of time after Fig.4c, first dose of fentanyl and antagonists, Fig. 4d, second fentanyl dose after 6 hr, and Fig.4e, third fentanyl dose after 24 hr. Animals were monitored in plethysmography chamber for90 min after each fentanyl dose. Fig. 4f, A single intravenous (i.v.) injection of 60 µmol kg-1of test compound (equivalent to 20 mg kg-1 of naloxone and 63 mg kg-1 of AG10-L-E2-Naloxone) were administered to male Sprague Dawley rats (n = 3 for each group). Theconcentration of the test compounds in plasma was determined at different time points andexpressed as means ± s.d. of three biological replicates. Fig. 4g through Fig. 4i, Reversal offentanyl induced OIRD by intravenously (i.v.) administered naloxone and AG10-L-E2-Naloxone. Minute Volume (mean ± s.d.; n= 6 biological replicates per group) is plotted as afunction of time after Fig. 4g, First dose of fentanyl (3 mg kg-1; i.v. dose) was followed byantagonist (60 µmol kg-1; single i.v. dose) after 1 min. Fig. 4h, second dose of fentanyl (1.5mg kg-1; i.v. dose). Fig. 4i, third dose of fentanyl (1.5 mg kg-1; i.v. dose). Animals weremonitored in plethysmography chamber for 90 min after each fentanyl dose. Theplethysmography data were analyzed as described above in Fig. 3f through Fig. 3i.Fig. 5 shows preclinical evaluation and pharmacokinetic study of AG10-L-E2-Naloxone in monkey. Fig. 5a through Fig. 5d, Evaluating the efficacy of a mixture of AG10-L-E2-Naloxone and low dose of free naloxone against fentanyl induced OIRD in rats. Asingle s.c. dose combination of AG10-L-E2-Naloxone (60 µmol kg-1; equivalent to 63 mg kg-1) and naloxone (3 µmol kg-1; equivalent to 1 mg kg-1) resulted in excellent efficacy data withfull reversals of OIRD after all three fentanyl doses. Minute Volume (mean ± s.d.; n= 6biological replicates per group). Fig. 5e through Fig. 5g, Evaluating the potential of usingAG10-L-E2-Naloxone as a prophylactic agent against fentanyl in rats. Rats were first dosedwith AG10-L-E2-Naloxone (60 µmol kg-1) or naloxone (15 µmol kg-1 and 60 µmol kg-1).After 6 hr, the rats were challenged with a single dose of fentanyl (1.5 mg kg-1; s.c. dose).Minute Volume (mean ± s.d.; n= 6 biological replicates per group). The plethysmographydata were analyzed as described above in Fig. 3f through Fig. 3i. Fig. 5h, Effect of AG10-L-E2-Naloxone (60 µmol kg-1; s.c. dose) administration on body weight of rats over four weeks.Three groups of rats were used. Group one was treated with a vehicle. Group two was treatedwith AG10-L-E2-Naloxone (60 µmol kg-1). Group three was treated with fentanyl followedby AG10-L-E2-Naloxone (60 µmol kg-1) and then doses of fentanyl at 6 hr and 24 hr. Bodyweigh represent mean ± s.d. (n= 6 biological replicates per group). Fig. 5i through Fig. 5k,Assessment of the cytotoxicity of AG10-L-E2-Naloxone and its metabolite, AG10-L-E2-Attorney Docket No. 330272000240COOH (at 100 μM), on a number of cell lines using the MTT assay after 72 hr. Doxorubicinwas used as a positive control (at 10 μM). Fig.5i, HeLa; cervical cancer cell line. Fig.5j,Hep3B; human hepatoma cell line. Fig. 5k, MCF7; breast cancer cell line. Each bar showsmean ± s.d. (n= 4 independent replicates). Fig. 5l, A single subcutaneous (s.c.) injection ofAG10-L-E2-Naloxone (30 µmol kg-1; equivalent to 31 mg kg-1of) was administered to threemale cynomolgus monkey. The concentration of the AG10-L-E2-Naloxone and naloxonereleased from AG10-L-E2-Naloxone in plasma for each monkey was determined at differenttime points and expressed as means ± s.d. of three biological replicates. Fig. 6 shows calculated pKa values and predicted ionization for, AG10-L-E2-Naloxone (Fig, 6a), AG10-L-E2-COOH (Fig, 6b), and AG10-L-E2-Ethyl (Fig, 6c) in water(acidic ph ~3.5 obtained by dissolving the HCl salts of these conjugates in water) andphysiological pH (7.4).Fig.7 shows docking study of AG10-L-E2-Naloxone and known CES2 selective prodrug esters with CES2 and CES1. The mouse CES2 enzyme (pdb id: 8AXC)1catalytic triad residues S230, E347, and H459 are represented as black sticks. Zoom in highlighting the distance between the nucleophilic S230 and the carbonyl ester of AG10-L-E2-Naloxone is 2.9 Å. The distance between S230 and the carbonyl ester of prodrugs irinotecan, procaine, and molnupiravir is 3.3 Å, 3.1 Å, and 3.5 Å, respectively. Docking of prodrugs with CES1 (pdb id: 1MX9)2showed longer distance of 9.2 Å, 6.8 Å, and 4.8 Å for irinotecan, procaine, and molnupiravir, respectively. Docking studies showed no binding of AG10-L-E2-Naloxone to CES1. Fig.8 shows chemical structures and stability of newly synthesized aryl-basednaloxone prodrugs. Fig. 8a, Chemical structures of newly synthesized aryl-based naloxoneprodrugs; BA-Naloxone, Boc-PABA-Naloxone, PABA-Naloxone and known CES2 selectiveprodrugs. Stability of prodrugs in Fig. 8b and Fig. 8c human plasma (tested at 100 μM), andFigs. 8d-i, rat plasma. Stability of compounds (tested at 100 μM) in rat plasma wasperformed in the absence and presence of CES2 inhibitor, loperamide, and CES1 inhibitor, digitonin. The known CES2 selective substrates procaine (local anesthetic), molnupiravir (COVID-19 therapeutic), and irinotecan (anticancer drug) were included for comparison. The acyl moieties of the esters are shown in red color. The concentration remaining in respective media was determined at the indicated time points using HPLC. Bar graphs represent theAttorney Docket No. 330272000240mean of % compound remaining ± s.d. (n = 3 independent replicates). Statistical differenceswere determined using two-way ANOVA (mixed model) followed by Tukey’s post hoc test. Fig. 9 shows evaluations of the effect of TTR on the in vitro pharmacokinetics ofAG10-L-E2-Naloxone. Fig.9a, Stability of AG10-L-E2-Naloxone (tested at 5 μM) in rat plasma in the absence and presence of the selective TTR ligand, AG10 (10 μM). Fig.9b, Metabolic bioactivation of AG10-L-E2-Naloxone (5 μM) in human liver microsomes (HLM),with and without human TTR (5 μM). Fig. 9c, Evaluating the effect of AG10-L-E2-Naloxone’s (5 μM) binding to human TTR (5 μM) in buffer using rapid equilibrium dialysiswith molecular weight cut-off (MWCO) of 8 kDa. Bar graphs for Figs. 9a-c represent themean of % compound remaining / bound ± s.d. (n = 3 independent replicates). Statisticaldifferences were determined using two-way ANOVA (mixed model) followed by Holm- Šídák test for a, b, and one-way ANOVA followed by Tukey’s post hoc test for c. For a,F(2,8) = 62.29, (*P  < 0.0001 compared to AG10-L-E2-Naloxone). For b, F(1,4) =223.4, ( *P  < 0.0001 compared to AG10-L-E2-Naloxone). For c, F(2,6) = 3216, ( *P < 0.0001 compared to AG10-L-E2-Naloxone with no TTR or AG10). Fig. 10 shows evaluation of the blood brain barrier penetration of AG10-L-E2-Naloxone and AG10-L-E2-COOH. Fig.10a, The brain concentration to plasma concentration ratio and Fig.10b, CSF to plasma concentration ratio of AG10-L-E2- Naloxone, AG10-L-E2-COOH, naloxone from AG10-L-E2-Naloxone, and freelyadministered naloxone. Male Sprague Dawley rats (n = 3 for each group) were dosed with asingle s.c. injection of 15 µmol kg-1of test compound (equivalent to 5 mg kg-1of naloxone and 15.8 mg kg-1of AG10-L-E2-Naloxone). Bar graphs show the respective mean ±s.d. of three biological replicates. Statistical differences were determined using two-way ANOVAfollowed by Holm-Šídák test (*P < 0.0001 compared to naloxone). For the brain to plasmaratio experiment F(1,4) = 59.34, P < 0.0001 and for the CSF to plasma ratio experiment F(1,4) = 35.87, P < 0.0001. Fig. 11 shows pharmacodynamic evaluation of repeated doses of AG10-L-E2-Naloxone in rats. Mortality data for fentanyl overdose and rescue by multiple small doses ofnaloxone in male Sprague Dawley rats (n = 8 biological replicates for each group). Dosing schedule of fentanyl (s.c. doses of 3 mg kg-1at 0 hr and 3 mg kg-1at 6 hr). Group1 (red line): dosed with vehicle. Group 2 (gray line): first dosed with a single s.c. dose of 3 µmol kg-1of naloxone (equivalent to 1 mg kg-1) 5 min after the first fentanyl dose followed by five smallerAttorney Docket No. 330272000240doses of naloxone (0.6 µmol kg-1of naloxone per dose; equivalent to 0.2 mg kg-1per dose) at 1.5, 2.5, 3.5, 4.5, and 5.5 hr. Group 3 (blue line): first dosed with a single s.c. dose of 3 µmol kg-1of naloxone (equivalent to 1 mg kg-1) 5 min after the first fentanyl dose followed by ten smaller doses of naloxone (0.6 µmol kg-1of naloxone per dose; equivalent to 0.2 mg kg-1perdose) at 1.5, 2.5, 3.5, 4.5, 5.5., 6.5, 7.5, 8.5, 9.5, and 10.5 hr. Statistical differences weredetermined using Log-rank (Mantel-Cox) test followed by Bonferroni correction method for multiple comparisons, Bonferroni-corrected α= 0.016. *P < 0.0001 compared to vehicle and **P < 0.0026 compared to vehicle. Fig. 12 shows comparison of the pharmacokinetic profiles of the low and high dosesof s.c. administered naloxone for up to 6 hr. The naloxone pharmacokinetic profiles (data from Fig.3a and 5a) show that the higher naloxone dose (20 mg kg-1, s.c.) has a slower clearance rate between 0.5 and 2 hr compared to the 5 mg kg-1dose, likely due to temporary saturation of clearance pathways. After 2 hr, both doses exhibit similar clearance rates and linear kinetics, indicating limited tissue redistribution effects at the higher dose. Fig. 13 shows reversal of intravenously (i.v.) administered fentanyl OIRD in maleSprague Dawley rats by multiple small doses of naloxone or AG10-L-E2-Naloxone. Fig.13a, Dosing schedule of fentanyl and antagonists. Naloxone (0.6 µmol kg-1per i.v. dose; equivalent to 0.2 mg kg-1) was administered within 1 min of the first fentanyl dose (3 mg kg-1; i.v. dose) followed by five small i.v. doses at 2, 3, 4, 5, 6 hr followed by a second dose offentanyl (1.5 mg kg-1; i.v. dose) at 6 hr (n= 6 per group). AG10-L-E2-Naloxone (15 µmol kg-1per i.v. dose; equivalent to 5 mg kg-1) was administered within 1 min of the first fentanyl dose (3 mg kg-1; i.v. dose) followed by one dose at 4 hr. The second dose of fentanyl (1.5 mg kg-1; i.v. dose) was administered at 6 hr. Reversal of OIRD is represented by Minute Volume relative to baseline (Minute Volume of rats before fentanyl injection was considered to be thebaseline). Minute Volume (mean ± s.d.; n= 6 biological replicates per group) is plotted as afunction of time after Fig.13b, first dose of fentanyl and antagonists, Fig.13c, second fentanyl dose after 6 hr. Animals were monitored in plethysmography chamber for 90 min after each fentanyl dose. Data were analyzed using the GraphPad Prism V9.3.1.471 software (La Jolla, CA, USA). A priori analysis revealed that to achieve a statistical power of 0.8 with alpha equal to 0.05, given our experimental s.d. values, the number of animals per group must be at least 3. The power analysis was performed by G*Power software (version 3.0.10). Statistical difference was determined using two-way ANOVA repeated measures followed by the Tukey’s post hoc test. Significant differences were determined at (#) P < 0.05.Attorney Docket No. 330272000240Figs. 14a-e show the results of rat plasma stability assays for AG10-L-E2-naloxone,AG10-L-PHBA-E-naloxone, PEG linker-E2-naloxone, AG10-short-L-E2-naloxone, and AG10-L-meta-amino-E-naloxone, respectively. Fig.15 shows the results of human plasma stability assays for AG10-L-E2-naloxone, AG10-L-PHBA-E-naloxone, PEG linker-E2-naloxone, AG10-short-L-E2-naloxone, and AG10-L-meta-amino-E-naloxone. Figs.16a-f show the results rat plasma stability assays for AG10-L-E2-paracetamol, AG10-L-E2-propofol, AG10-L-E2-estrone, AG10-L-E2-endomorphin-2, AG10-L-E2-Tyr- Ala, and AG10-L-E2-Dermorphin respectively. Fig.17 shows the results of human plasma stability assays for AG10-L-E2- paracetamol, AG10-L-E2-propofol, AG10-L-E2-estrone, AG10-L-E2-endomorphin-2, AG10-L-E2-Tyr-Ala, and AG10-L-E2-Dermorphin. DETAILED DESCRIPTION OF THE INVENTION Here we developed a fundamentally new prodrug approach for enhancing the DOA ofdrugs without affecting their biological activity. Our approach involves conjugating the drugthrough an ester moiety to a selective TTR ligand. The approach described herein can be used for a variety of drug moieties, including small molecules, peptides and proteins. Using selective TTR ligands, as set forth herein, to harness endogenous TTR represents a major advantage for a new prodrug approach. TTR is a 55 kDa homo-tetrameric protein that is mainly secreted from the liver into the blood and has a circulation half-life of approximately2 days. The main function of TTR in humans (concentration in plasma ~5 μM) is to transportholo-retinol binding protein (RBP bound to retinol or vitamin A) in blood. Using orthogonal sites to those of holo-RBP, TTR acts as a backup carrier of thyroxine (<1% thyroxine bound). Our approach has several unique features that would make it ideal for controlling the release and extending the DOA of drugs. First, the prodrugs are capable of binding to TTR, which could extend their DOA to 2 days or more. Second, the prodrugs have balanced hydrophilicity which is critical for rapid absorption from the subcutaneous tissue to provide sufficient concentration of antidote for effective rescue. Third, the balanced hydrophilicity, small size, and ease of synthesis of our conjugates (we are not using polymers) would make itideal for subcutaneous (s.c.) administration, which has the advantages of ease ofadministration and at the same time would provide extension of duration of prodrugsAttorney Docket No. 330272000240compared to the intravenous route. Fourth, the modular approach would allow us to generateprodrugs with tunable hydrolysis rates that can be applied for rescue, protection (prophylaxes), or both. DEFINITIONS “Individual” or “subject” refers to mammals and includes humans and non-human mammals. Examples of individuals include, but are not limited to, mice, rats, hamsters, guinea pigs, pigs, rabbits, cats, dogs, goats, sheep, cows, monkeys, and humans. In some embodiments, individual or subject refers to a human. As used herein, “about” a parameter or value includes and describes that parameter or value per se. For example, “about X” includes and describes X per se. “Treatment” or “treating” is an approach for obtaining beneficial or desired results including clinical results. Beneficial or desired results may include one or more of the following: decreasing one or more symptom resulting from the disease or condition; diminishing the extent of the disease or condition; slowing or arresting the development of one or more symptom associated with the disease or condition (e.g., stabilizing the disease or condition, preventing or delaying the worsening or progression of the disease or condition); and relieving the disease, such as by causing the regression of clinical symptoms (e.g., ameliorating the disease state, enhancing the effect of another medication, delaying the progression of the disease, increasing the quality of life, and / or prolonging survival). As used herein, “delaying” development of a disease or condition means to defer, hinder, slow, retard, stabilize and / or postpone development of the disease or condition. Thisdelay can be of varying lengths of time, depending on the history of the disease and / orindividual being treated. As is evident to one skilled in the art, a sufficient or significant delay can, in effect, encompass prevention, in that the individual does not develop the disease or condition. As used herein, the term “therapeutically effective amount” or “effective amount” intends such amount of a compound of the disclosure or a pharmaceutically salt thereof sufficient to effect treatment when administered to an individual. As is understood in the art, an effective amount may be in one or more doses, e.g., a single dose or multiple doses may be required to achieve the desired treatment endpoint. An effective amount may be considered in the context of administering one or more therapeutic agents, and a single agent may beAttorney Docket No. 330272000240considered to be given in an effective amount if, in conjunction with one or more other agents, a desirable or beneficial result may be or is achieved. As used herein, “unit dosage form” refers to physically discrete units, suitable as unit dosages, each unit containing a predetermined quantity of active ingredient, or compound, which may be in a pharmaceutically acceptable carrier. As used herein, by “pharmaceutically acceptable” is meant a material that is not biologically or otherwise undesirable, e.g., the material may be incorporated into a pharmaceutical composition administered to an individual without causing significant undesirable biological effects. As used herein, the term “half-life” can be used to refer to lose half of its activity, for example, its pharmacologic, physiologic, or radiologic activity. The term “half-life” can be used interchangeably with the terms “biological half-life” or “terminal half-life”. In some embodiments, the half-life of a substance is the time it takes for a substance, for example, a metabolite, drug, signaling molecule, radioactive nuclide, or other substance, to lose half ofits pharmacologic, physiologic, or radiologic activity. In some embodiments, the term half-life can be used to refer to the body's cleansing through the function of kidneys and liver in addition to excretion functions to eliminate a substance from the body. In some embodiments, the term “half-life” can be used to refer to the time it takes for the blood plasma concentration of a substance to halve (plasma half-life) its steady-state. As used herein, the term “linker”, “linkage” and “linking group” refers to a chemical linking moiety that connects two groups and has a backbone of 50 atoms or less in length. In some embodiments, the linker or linkage may be a covalent bond that connects two groups, or a chemical moiety having a chain of between 1 and 50 atoms in length, between 2 and 20 atoms in length, between 3 and 30 atoms in length, between 4 and 40 atoms in length,between 10 and 50 atoms in length, between 10 and 30 atoms in length, between 12 and 26atoms in length, between 14 and 30 atoms in length, or any range therein in amounts of 1 atom in length. For example, a linker or a portion of a linker can have a length that is 1, 2, 3, 4, 5, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 45, or 50 carbon atoms in length, where the linker may be linear, branched, cyclic, or a single atom. In some embodiments, the linker may be 10 angstroms, 11 angstroms, 12 angstroms, 13 angstroms, 14 angstroms, 15 angstroms, 16 angstroms, 17 angstroms, 18 angstroms, 19 angstroms, 20 angstroms, 22 angstroms, 23 angstroms, 24 angstroms, 25 angstroms, 26 angstroms, 27Attorney Docket No. 330272000240angstroms, 28 angstroms, 29 angstroms, 30 angstroms, 32 angstroms, 34 angstroms, 36 angstroms, 38 angstroms, 40 angstroms, 45 angstroms, 50 angstroms, or any amount therein in increments of 1 angstrom, in length. In some embodiments, one, two, three, four or five or more carbon atoms of a linker backbone may be optionally substituted with a sulfur, nitrogen or oxygen heteroatom. The bonds between backbone atoms may be saturated or unsaturated, usually not more than one, two, or three unsaturated bonds will be present in a linker backbone. The linker may include one or more substituent groups, for example with an alkyl, aryl or alkenyl group. A linker may include, without limitations, oligo(ethylene glycol); ethers, thioethers, tertiary amines, alkyls, which may be straight or branched, e.g., methyl, ethyl, n-propyl, 1-methylethyl (iso-propyl), n-butyl, n-pentyl, 1,1-dimethylethyl (t-butyl), and the like. The linker backbone may include a cyclic group, for example, an aryl, a heterocycleor a cycloalkyl group, where 2 or more atoms, e.g., 2, 3 or 4 atoms, of the cyclic group areincluded in the backbone. A linker may be cleavable or non-cleavable. The linking moiety may be conjugated to the TTR ligand and Y using any convenient functional groups (carboxylic acids, amines, alcohols, carbamates, esters, amide, ethers, thioethers, maleimides, and the like), and linking chemistries. For example, conjugation chemistry described by G. T. Hermanson (“Bioconjugate Techniques”, Academic Press, Second Edition, 2008) may be readily adapted for use in preparing the subject heterobifunctional compounds and is hereby incorporated herein by reference in its entirety. The term “alkyl”, as used herein, refers to an unbranched or branched saturated univalent hydrocarbon chain. As used herein, alkyl has 1-20 carbons (i.e., C1-20alkyl), 1-16 carbons (i.e., C1-16alkyl), 1-12 carbons (i.e., C1-12alkyl), 1-10 carbons (i.e., C1-10alkyl), 1-8 carbons (i.e., C1-8alkyl), 1-6 carbons (i.e., C1-6alkyl), 1-4 carbons (i.e., C1-4alkyl), or 1-3 carbons (i.e., C1-3alkyl). Examples of alkyl groups include, but are not limited to, methyl, ethyl, propyl, iso-propyl, n-butyl, sec-butyl, iso-butyl, tert-butyl, pentyl, 2-pentyl, iso-pentyl, neo-pentyl, hexyl, 2-hexyl, 3-hexyl, and 3-methylpentyl. When an alkyl residue having a specific number of carbons is named by chemical name or molecular formula, all positional isomers having that number of carbon atoms may be encompassed—for example, “butyl” includes n-butyl, sec-butyl, iso-butyl, and tert-butyl; and “propyl” includes n-propyl and iso- propyl. Certain commonly used alternative names may be used and will be understood by those of ordinary skill in the art. For instance, a divalent group, such as a divalent “alkyl” group, may be referred to as an “alkylene”.Attorney Docket No. 330272000240The term “alkenyl”, as used herein, refers to a branched or unbranched univalent hydrocarbon chain comprising at least one carbon-carbon double bond. As used herein, alkenyl has 2-20 carbons (i.e., C2-20alkenyl), 2-16 carbons (i.e., C2-16alkenyl), 2-12 carbons (i.e., C2-12alkenyl), 2-10 carbons (i.e., C2-10alkenyl), 2-8 carbons (i.e., C2-8alkenyl), 2-6 carbons (i.e., C2-6alkenyl), 2-4 carbons (i.e., C2-4alkenyl), or 2-3 carbons (i.e., C2-3alkenyl). Examples of alkenyl include, but are not limited to, ethenyl, prop-1-enyl, prop-2-enyl 1,2- butadienyl, and 1,3-butadienyl. When an alkenyl residue having a specific number of carbons is named by chemical name or molecular formula, all positional isomers having that number of carbon atoms may be encompassed—for example, “propenyl” includes prop-1- enyl and prop-2-enyl. Certain commonly used alternative names may be used and will be understood by those of ordinary skill in the art. For instance, a divalent group, such as a divalent “alkenyl” group, may be referred to as an “alkenylene”. The term “alkynyl”, as used herein, refers to a branched or unbranched univalent hydrocarbon chain comprising at least one carbon-carbon triple bond. As used herein, alkynyl has 2-20 carbons (i.e., C2-20alkynyl), 2-16 carbons (i.e., C2-16alkynyl), 2-12 carbons (i.e., C2-12alkynyl), 2-10 carbons (i.e., C2-10alkynyl), 2-8 carbons (i.e., C2-8alkynyl), 2-6 carbons (i.e., C2-6alkynyl), 2-4 carbons (i.e., C2-4alkynyl), or 2-3 carbons (i.e., C2-3alkynyl). Examples of alkynyl include, but are not limited to, ethynyl, prop-1-ynyl, prop-2-ynyl, but-1- ynyl, but-2-ynyl, and but-3-ynyl. When an alkynyl residue having a specific number of carbons is named by chemical name or molecular formula, all positional isomers having that number of carbon atoms may be encompassed—for example, “propynyl” includes prop-1- ynyl and prop-2-ynyl. Certain commonly used alternative names may be used and will be understood by those of ordinary skill in the art. For instance, a divalent group, such as a divalent “alkynyl” group, may be referred to as an “alkynylene”. The term “alkoxy”, as used herein, refers to an -O-alkyl moiety. Examples of alkoxy groups include, but are not limited to, methoxy, ethoxy, n-propoxy, iso-propoxy, n-butoxy, tert-butoxy, sec-butoxy, n-pentoxy, n-hexoxy, and 1,2-dimethylbutoxy. The term “aryl”, as used herein, refers to a fully unsaturated carbocyclic ring moiety. The term “aryl” encompasses monocyclic and polycyclic fused-ring moieties. As used herein, aryl encompasses ring moieties comprising, for example, 6 to 20 annular carbon atoms (i.e., C6-20aryl), 6 to 16 annular carbon atoms (i.e., C6-16aryl), 6 to 12 annular carbonAttorney Docket No. 330272000240atoms (i.e., C6-12aryl), or 6 to 10 annular carbon atoms (i.e., C6-10aryl). Examples of aryl moieties include, but are not limited to, phenyl, naphthyl, fluorenyl, and anthryl. The term “cycloalkyl”, as used herein, refers to a saturated or partially unsaturated carbocyclic ring moiety. The term “cycloalkyl” encompasses monocyclic and polycyclic ring moieties, wherein the polycyclic moieties may be fused, branched, or spiro. Cycloalkyl includes cycloalkenyl groups, wherein the ring moiety comprises at least one annular double bond. Cycloalkyl includes any polycyclic carbocyclic ring moiety comprising at least one non-aromatic ring, regardless of the point of attachment to the remainder of the molecule. As used herein, cycloalkyl includes rings comprising, for example, 3 to 20 annular carbon atoms (i.e., a C3-20cycloalkyl), 3 to 16 annular carbon atoms (i.e., a C3-16cycloalkyl), 3 to 12 annular carbon atoms (i.e., a C3-12cycloalkyl), 3 to 10 annular carbon atoms (i.e., a C3-10cycloalkyl), 3 to 8 annular carbon atoms (i.e., a C3-8cycloalkyl), 3 to 6 annular carbon atoms (i.e., a C3-6cycloalkyl), or 3 to 5 annular carbon atoms (i.e., a C3-5cycloalkyl). Monocyclic cycloalkyl ring moieties include, for example, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl. Polycyclic groups include, for example, bicyclo[2.2.1]heptanyl, bicyclo[2.2.2]octanyl, adamantyl, norbonyl, decalinyl, 7,7-dimethyl -bicyclo [2.2.1]heptanyl, and the like. Still further, cycloalkyl also includes spiro cycloalkyl ring moieties, for example, spiro[2.5]octanyl, spiro[4.5]decanyl, or spiro [5.5]undecanyl. The term “halo”, as used herein, refers to atoms occupying groups VIIA of The Periodic Table and includes fluorine (fluoro), chlorine (chloro), bromine (bromo), and iodine (iodo). Additionally, terms such as “haloalkyl” are meant to include monohaloalkyl and polyhaloalkyl. For example, the term “C1-4haloalkyl” is mean to include trifluoromethyl, 2,2,2-trifluoroethyl, 4-chlorobutyl, 3-bromopropyl, difluoromethyl, and the like. The term “heteroaryl”, as used herein, refers to an aromatic (fully unsaturated) ringmoiety that comprises one or more annular heteroatoms independently selected from the group consisting of nitrogen, oxygen, and sulfur. The term “heteroaryl” includes both monocyclic and polycyclic fused-ring moieties. As used herein, a heteroaryl comprises, forexample, 5 to 20 annular atoms (i.e., a 5- to 20-membered heteroaryl), 5 to 16 annular atoms(i.e., a 5- to 16-membered heteroaryl), 5 to 12 annular atoms (i.e., a 5- to 12-memberedheteroaryl), 5 to 10 annular atoms (i.e., a 5- to 10-membered heteroaryl), 5 to 8 annular atoms(i.e., a 5- to 8-membered heteroaryl), or 5 to 6 annular atoms (i.e., a 5- to 6-memberedheteroaryl). Any monocyclic or polycyclic aromatic ring moiety comprising one or moreAttorney Docket No. 330272000240annular heteroatoms is considered a heteroaryl, regardless of the point of attachment to the remainder of the molecule (i.e., the heteroaryl moiety may be attached to the remainder of the molecule through any annular carbon or any annular heteroatom of the heteroaryl moiety). Examples of heteroaryl groups include, but are not limited to, oxazolyl, thiazolyl, pyridinyl, pyrimidinyl, and pyridazinyl. The term “heterocyclyl”, as used herein, refers to a saturated or partially unsaturated cyclic moiety that encompasses one or more annular heteroatoms independently selected from the group consisting of nitrogen, oxygen, and sulfur. The term “heterocyclyl” includes both monocyclic and polycyclic ring moieties, wherein the polycyclic ring moieties may be fused, bridged, or spiro. Any non-aromatic monocyclic or polycyclic ring moiety comprising at least one annular heteroatom is considered a heterocyclyl, regardless of the point of attachment to the remainder of the molecule (i.e., the heterocyclyl moiety may be attached to the remainder of the molecule through any annular carbon or any annular heteroatom of the heterocyclyl moiety). Further, the term heterocyclyl is intended to encompass any polycyclic ring moiety comprising at least one annular heteroatom wherein the polycyclic ring moiety comprises at least one non-aromatic ring, regardless of the point of attachment to the remainder of the molecule. As used herein, a heterocyclyl comprises, for example, 3 to 20annular atoms (i.e., a 3- to 20-membered heterocyclyl), 3 to 16 annular atoms (i.e., a 3- to 16-membered heterocyclyl), 3 to 12 annular atoms (i.e., a 3- to 12-membered heterocyclyl), 3 to10 annular atoms (i.e., a 3- to 10-membered heterocyclyl), 3 to 8 annular atoms (i.e., a 3- to8-membered heterocyclyl), 3 to 6 annular atoms (i.e., a 3- to 6-membered heterocyclyl), 3 to5 annular atoms (i.e., a 3- to 5-membered heterocyclyl), 5 to 8 annular atoms (i.e., a 5- to 8-membered heterocyclyl), or 5 to 6 annular atoms (i.e., a 5- to 6-membered heterocyclyl).Examples of heterocyclyl groups include, e.g., azetidinyl, piperidinyl, piperazinyl,pyrrolidinyl, pyrazolidinyl, thiazolidinyl, tetrahydrofuryl, or tetrahydropyranyl. Examples ofspiro heterocyclyl rings include, but are not limited to, bicyclic and tricyclic ring systems, such as oxabicyclo[2.2.2]octanyl, 2-oxa-7-azaspiro[3.5]nonanyl, 2-oxa-6- azaspiro[3.4]octanyl, and 6-oxa-1-azaspiro[3.3]heptanyl. Examples of fused heterocyclyl rings include, but are not limited to, 5,6,7,8-tetrahydropyrido[4,3-d]pyrimidinyl, 6,7-dihydro- 5H-pyrrolo[3,4-d]pyrimidinyl, 5,7-dihydrofuro[3,4-d]pyrimidinyl, and 5,7-dihydrothieno[3,4-d]pyrimidinyl, where the heterocyclyl can be bound via either ring of the fused system.The term “oxo”, as used herein, refers to a =O moiety.Attorney Docket No. 330272000240The terms “optional” and “optionally”, as used herein, mean that the subsequently described event or circumstance may or may not occur and that the description includes instances where the event or circumstance occurs and instances where it does not. Accordingly, the term “optionally substituted” infers that any one or more (e.g., 1, 2, 1 to 5, 1 to 3, 1 to 2, etc.) hydrogen atoms on the designated atom or moiety or group may be replaced or not replaced by an atom or moiety or group other than hydrogen. By way of illustration and not limitation, the phrase “methyl optionally substituted with one or more chloro” encompasses -CH3, -CH2Cl, -CHCl2, and -CCl3 moieties. It is understood that aspects and embodiments described herein as “comprising” include “consisting of” and “consisting essentially of” embodiments. The term “pharmaceutically acceptable salt”, as used herein, of a given compound refers to salts that retain the biological effectiveness and properties of the given compound and which are not biologically or otherwise undesirable. “Pharmaceutically acceptable salts” include, for example, salts with inorganic acids, and salts with an organic acid. In addition, if the compounds described herein are obtained as an acid addition salt, the free base can be obtained by basifying a solution of the acid salt. Conversely, if the product is a free base, an addition salt, particularly a pharmaceutically acceptable addition salt, may be produced by dissolving the free base in a suitable organic solvent and treating the solution with an acid, in accordance with conventional procedures for preparing acid addition salts from base compounds. See, e.g., Handbook of Pharmaceutical Salts Properties, Selection, and Use, International Union of Pure and Applied Chemistry, John Wiley & Sons (2008), which isincorporated herein by reference in its entirety. Those skilled in the art will recognize varioussynthetic methodologies that may be used to prepare nontoxic pharmaceutically acceptable addition salts. Pharmaceutically acceptable acid addition salts may be prepared from inorganic or organic acids. Salts derived from inorganic acids include, e.g., hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, phosphoric acid, and the like. Salts derived from organic acids include, e.g., acetic acid, propionic acid, gluconic acid, glycolic acid, pyruvic acid, oxalic acid, malic acid, malonic acid, succinic acid, maleic acid, fumaric acid, tartaric acid, citric acid, benzoic acid, cinnamic acid, mandelic acid, methanesulfonic acid, ethanesulfonic acid, p-toluene-sulfonic acid, salicylic acid, trifluoroacetic acid, and the like. Likewise, pharmaceutically acceptable base addition salts can be prepared from inorganic or organic bases. Salts derived from inorganic bases include, by way of example only, sodium, potassium, lithium, aluminum, ammonium, calcium, and magnesium salts. Salts derivedAttorney Docket No. 330272000240from organic bases include, but are not limited to, salts of primary, secondary, and tertiary amines. Specific examples of suitable amines include, by way of example only, isopropylamine, trimethyl amine, diethyl amine, tri(iso-propyl) amine, tri(n-propyl) amine, ethanolamine, 2-dimethylaminoethanol, piperazine, piperidine, morpholine, N- ethylpiperidine, and the like. Some of the compounds provided herein may exist as tautomers. Tautomers are inequilibrium with one another. By way of illustration, amide containing compounds may exist in equilibrium with imidic acid tautomers. Regardless of which tautomer is shown and regardless of the nature of the equilibrium among tautomers, the compounds of this disclosure are understood by one of ordinary skill in the art to comprise both amide and imidic acid tautomers. Thus, for example, amide-containing compounds are understood to include their imidic acid tautomers. Likewise, imidic-acid containing compounds are understood to include their amide tautomers. The compounds of the present disclosure, or their pharmaceutically acceptable salts, may include an asymmetric center and may thus give rise to enantiomers, diastereomers, and other stereoisomeric forms that may be defined, in terms of absolute stereochemistry, as (R)-or (S)- (or as (D)- or (L)- for amino acids). The present disclosure is meant to include allsuch possible isomers, as well as their racemic and optically pure forms and mixtures thereofin any ratio. Optically active (+) and (-), (R)- and (S)-, or (D)- and (L)- isomers may beprepared using chiral synthons or chiral reagents, or may be resolved using conventional techniques, for example, chromatography and / or fractional crystallization. Conventional techniques for the preparation / isolation of individual enantiomers include chiral synthesis from a suitable optically pure precursor or the resolution of the racemate (or the racemate of a salt or derivative) using, for example, chiral high pressure liquid chromatography (HPLC), and chiral supercritical fluid chromatography (SFC). When the compounds described herein contain olefinic double bonds or other centers of geometric asymmetry, unless specified otherwise, it is intended that the present disclosure includes both E and Z geometric isomers.Likewise, cis- and trans- are used in their conventional sense to describe relative spatialrelationships. CONJUGATES In one aspect, provided herein is a conjugate of formula (I):Attorney Docket No. 330272000240(I) or a pharmaceutically acceptable salt thereof, wherein: Tis a ligand selective for transthyretin TTR;L is a linker; LBis absent or a click product formed via a Click reaction between a first Click handle and a second click handle; E is a cleavable ester; and D1is a drug moiety. In some embodiments, the linker (L) has a size of from about 10 Å to about 40 Å. In some embodiments, the linker (L) has a size of from about 10 Å to about 40 Å. In some embodiments, the linker (L) has a size of from about 15 Å to about 30 Å. In some embodiments, the linker (L) has a size of from about 20 Å to about 30 Å. In some embodiments, the linker (L) has a size of about 20 Å. In some embodiments, the linker (L)has a size of about 25 Å. In some embodiments, the linker (L) has a size of about 30 Å.In some embodiments, the linker (L) and click product (LB) taken together have a size of about 10 Å to about 50 Å. In some embodiments, the linker (L) and click product (LB) taken together have a size of from about 15 Å to about 45 Å. In some embodiments, the linker (L) and click product (LB) taken together have a size of from about 25 Å to about 40 Å. In some embodiments, the linker (L) and click product (LB) taken together have a size of about 20 Å. In some embodiments, the linker (L) and click product (LB) taken together have a size of about 25 Å. In some embodiments, the linker (L) and click product (LB) taken together have a size of about 30 Å. In some embodiments, the linker (L) and click product (LB) taken together have a size of about 35 Å. In some embodiments, the linker (L) and click product (LB) taken together have a size of about 40 Å. In some embodiments, LBis the Click product of: (i) a copper-catalyzed reaction between an azide and an alkyne; (ii) a reaction between an azide and dibenzocyclooctene (DBCO);Attorney Docket No. 330272000240(iii) an inverse electron demand Diels-alder cycloaddition (IEDDA) between a trans- cyclooctene (TCO) moiety and a tetrazine ring, or (iv) a Staudinger reaction between an azide and a phosphine. In some embodiments, the first click handle and the second click handle used to form click product LBcan be any suitable click chemistry pair (e.g., Azide-DBCO, Azide-BCN, Tz-TCO, meTz-TCO, etc.). In some embodiments, the click product can be formed using a copper-catalyzed click reaction. One such copper-catalyzed click reaction is a Huisgen 1,3- dipolar cycloaddition (CuAAC) between an azide and an alkyne (see, e.g., Tornøe et al., J.Org. Chem. 2002, 67 (9), 3057-3064 and Rostovtsev et al., Angew. Chem. Int. Ed. 2002, 41(14), 2596-2599). In some embodiments, the click product is a triazole moiety. In some embodiments, the click product can be formed using a biorthogonal chemistry approach. In some embodiments, the click product LBcan be formed from any suitable inverse electron demand Diels-Alder reaction. In some embodiments, the click product can be formed from an inverse electron demand Diels-Alder reaction between a trans-cyclooctene (TCO) moiety on the first or second click handle and a tetrazine (Tz) ring on the first or second clickhandle (see, e.g., Selvaraj et al., Curr. Opin. Chem. Biol. 2013, 17 (5), 753-760 and Rossin etal., Bioconjugate Chem.2013, 24 (7), 1210-1217). In some embodiments, the first click handle comprises a tetrazine ring and the second click handle comprises a TCO moiety. In some embodiments, the tetrazine ring is unsubstituted. In some such embodiments, the tetrazine ring is methyltetrazine. In some embodiments, the tetrazine ring is a 6-methyl substituted tetrazine. In some embodiments, the click product is a dihydropyridazine moiety. In some embodiments, the click product LBis a triazine moiety. In some embodiments, the conjugate of formula (I) comprises one of the following moieties: , wherein X2 is -CH2-, -NRx-, -S- or -O-, wherein Rx is defined aselsewhere herein. In some embodiments, the conjugate comprises the moiety . In some embodiments, the conjugate comprises the moiety .Attorney Docket No. 330272000240In some embodiments, L is C4-20alkylene, wherein the C4-20alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, -NRx-, and -S-, wherein L1ais halo, C1-6alkyl, or C1-6alkyl substituted by halo, and wherein Rxis H or C1-6alkyl optionally substituted by halo. In some embodiments, L is C10-20alkylene, wherein the C10-20alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, -NH-, -N(CH3)-, and -S-. In some embodiments, L is C10-15alkylene, wherein the C10-15alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, -NH-, and -N(CH3)-. In some embodiments, L is C5-10alkylene, wherein the C5-10alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, and -NH-. In some embodiments, L comprises the moiety . In some embodiments, L comprises the moiety . the Attorney Docket No.330272000240 some embodiments, L comprises the comprises the moiety . In some embodiments, L Attorney Docket No. 330272000240 . In some embodiments, L-LBcomprises the moiety embodiments, L-LBcomprises the moiety some embodiments, L-LBcomprises the moietyAttorney Docket No. 330272000240 In some embodiments, L-LBcomprises the moiety In some embodiments, the conjugate of formula (I) comprises the moiety

[0002] Attorney Docket No. 330272000240 Ring A is C6-10aryl or 5- to 10-membered heteroaryl, whereinthe C6-10aryl or 5- to 10-membered heteroaryl is optionally substituted with one ormore R7, wherein each R7 is independently selected from the group consisting ofhydrogen, halogen atoms (e.g., Cl, Br or F), hydroxy, -OCF3, -NH2, -NO2, -NHC1-4alkyl, -N(C1-4 alkyl)2, -CONH2, -CONHC1-4 alkyl, -CON(C1-4 alkyl)2, -NHCOC1-4 alkyl, C1-6 alkyl, C1-6 alkoxy and C3-6 cycloalkyl and indicates the point of attachment to the linker (L or L-LB). In some embodiments, Ring A is an optionally substituted 5- to 10-memberedheteroaryl. Examples of heteroaryl rings include, but are not limited to, azetidinyl, pyrazyl, pyrrolyl, imidazolyl, pyrazolyl, pyridyl, pyrimidyl, pyridazyl, indolizyl, isoindolyl, indolyl, dihydroindolyl, indazolyl, purinyl, quinolizinyl, isoquinolinyl, quinolinyl, phthalazinyl, naphthylpyridinyl, quinoxalinyl, quinazolinyl, cinnolinyl, pteridinyl, carbazolyl, carbolinyl, phenanthridinyl, acridinyl, phenanthrolinyl, isothiazolyl, phenazinyl, isoxazolyl, phenoxazinyl, phenothiazinyl, imidazolidinyl, imidazolinyl, piperidinyl, piperazinyl, indolinyl, phthalimidyl, 1,2,3,4-tetrahydroisoquinolinyl, 4,5,6,7-tetrahydrobenzo[b]thiophenyl, thiazolyl, thiazolidinyl, thiophenyl, benzo[b]thiophenyl, morpholinyl, thiomorpholinyl, 1,1-dioxothiomorpholinyl, piperidinyl, pyrrolidinyl, and tetrahydrofuranyl. In some embodiments, Ring A is selected from the groupconsisting of phenyl, pyridyl, pyrimidinyl, oxazolyl, pyrazolyl, and thiazolyl, wherein thephenyl, pyridyl, pyrimidinyl, oxazolyl, pyrazolyl, or thiazolyl is optionally substituted withone or more C1-6alkyl, C1-6alkoxy, hydroxy, halo, -NH2, -NHC1-4alkyl, -N(C1-4alkyl)2, -Attorney Docket No. 330272000240CONH2, -CONHC1-4 alkyl, -CON(C1-4 alkyl)2, -NHCOC1-4 alkyl, C3-6 cycloalkyl, or -NO2,wherein the C1-6 alkyl or C1-6 alkoxy is optionally substituted by one or more halo. In someembodiments, Ring A is selected from the group consisting of phenyl, pyridyl, and pyrimidinyl, wherein the phenyl, pyridyl, and pyrimidinyl is optionally substituted with one or more C1-6alkyl, C1-6alkoxy, hydroxy, halo, -NH2, -NHC1-4alkyl, -N(C1-4alkyl)2, -CONH2, -CONHC1-4alkyl, -CON(C1-4alkyl)2, -NHCOC1-4alkyl, C3-6cycloalkyl, or nitro, wherein the C1-6 alkyl or C1-6 alkoxy is optionally substituted by one or more halo. In some embodiments, Ring A is a phenyl group or a substituted phenyl group. In some such embodiments, Ring A is substituted with a methyl group, methoxy group, halo group (e.g., Cl, Br, F or I), nitro group, or CF3group. In some embodiments, the conjugate of formula (I) comprises the moiety is In some embodiments, the conjugate of formula (I) comprises the moiety is In some embodiments, the conjugate of formula (I) comprises the moiety Attorney Docket No. 330272000240 each R7 is independently selected from the group consisting of hydrogen, halogen atoms(e.g., Cl, Br or F), hydroxy, -OCF3, -NH2, -NHC1-4 alkyl, -N(C1-4 alkyl)2, -CONH2, - CONHC1-4 alkyl, -CON(C1-4 alkyl)2, -NHCOC1-4 alkyl, C1-6 alkyl, C1-6 alkoxy and C3-6 cycloalkyl, p is 0, 1, 2, or 3, and indicates the point of attachment to the linker (L or L-LB). In some embodiments, the conjugate of formula (I) comprises the moiety wherein:Ring A is C6-10aryl or 5- to 10-membered heteroaryl, whereinAttorney Docket No. 330272000240the C6-10aryl or 5- to 10-membered heteroaryl is optionally substituted with one ormore R7, wherein each R7 is independently selected from the group consisting ofhydrogen, halogen atoms (e.g., Cl, Br or F), hydroxy, -OCF3, -NH2, -NHC1-4alkyl, - N(C1-4 alkyl)2, -CONH2, -CONHC1-4 alkyl, -CON(C1-4 alkyl)2, -NHCOC1-4 alkyl, C1-6 alkyl, C1-6alkoxy and C3-6cycloalkyl; and indicates the point of attachment to the linker (L). In some embodiments, the conjugate of formula (I) comprises the moiety wherein each R7 is independently selected from the group consisting of hydrogen, halogenatoms (e.g., Cl, Br or F), hydroxy, -OCF3, -NH2, -NHC1-4alkyl, -N(C1-4alkyl)2, -CONH2, - CONHC1-4 alkyl, -CON(C1-4 alkyl)2, -NHCOC1-4 alkyl, C1-6 alkyl, C1-6 alkoxy and C3-6 cycloalkyl, p is 0, 1, 2, or 3, and indicates the point of attachment to the linker (L). In some embodiments, the conjugate of formula (I) comprises the moiety , In some embodiments, the conjugate of formula (I) comprises the moietyAttorney Docket No. 330272000240 , wherein each methylene group can be optionally substituted with halogen atoms (e.g., Cl, Br or F), hydroxy, -OCF3, -NH2, -NHC1-4 alkyl, -N(C1-4 alkyl)2, - CONH2, -CONHC1-4alkyl, -CON(C1-4alkyl)2, -NHCOC1-4alkyl, C1-6alkyl, C1-6alkoxy or C3-6cycloalkyl. In some embodiments, the conjugate of formula (I) comprises the moiety wherein each methylene group can be optionally substituted with halogen atoms (e.g., Cl, Br or F), hydroxy, -OCF3, -NH2, -NHC1-4 alkyl, -N(C1-4 alkyl)2, -CONH2, -CONHC1-4 alkyl, - CON(C1-4alkyl)2, -NHCOC1-4alkyl, C1-6alkyl, C1-6alkoxy or C3-6cycloalkyl. and wherein indicates the point of attachment to the linker (L or L-LB), wherein indicates the point of attachment to the linker (L). In some embodiments, the conjugate of formula (I) comprises the moiety linker (L). In some embodiments, D1is a peptide. In some embodiments, the peptide is RGK-MCA. In some embodiments, the peptide is Neurotensin. In some embodiments, the peptide is Gonadotropin-releasing hormone (GnRH). In some embodiments, the peptide is GIP (1-42), human peptide. In someAttorney Docket No. 330272000240embodiments, the peptide is D6-GnRH. In some embodiments, the peptide is insulin. Insome embodiments, the peptide is teriparatide. In some embodiments, the peptide iscalcitronin salmon. In some embodiments, the peptide is ipamorelin. In some embodiments, the peptide is vasopressin. In some embodiments, the peptide is glucagon. In some embodiments, the peptide is aclerastide. In some embodiments, the peptide is goserelin. In some embodiments, the peptide is leuprolide. In some embodiments, the peptide is teriparatide. In some embodiments, the peptide is lixisenatide. In some embodiments, the peptide is desmopressin. In some embodiments, the peptide is oxytocin. In someembodiments, the peptide is corticotropin. In some embodiments, the peptide is sermorelin.In some embodiments, the peptide is bremelanotide. In some embodiments, the peptide is abaloparatide. In some embodiments, the peptide is deslorelin. In some embodiments, the peptide drug is a glucagon-like-peptide-1 (GLP-1) receptor agonist used to trat obesity and / or diabetes. In some such embodiments the peptidedrug is semaglutide, liraglutide, dulaglutide, albiglutide, or exenatide. Owing to the dramaticextension of duration of action of peptide drugs when incorporated into the conjugates of the disclosure, the GLP-1 agonist conjugates can be administered on a reduced dosing schedule, such as once weekly, once biweekly, once every three weeks, or once monthly. In some embodiments, the peptide drug is a glucagon-like-peptide-1 (GLP-1) and GIP (glucose-dependent insulinotropic polypeptide receptor agonist used to trat obesity and / or diabetes. In some such embodiments, the peptide drug is tirzepatide. Owing to the dramatic extension of duration of action of peptide drugs when incorporated into the conjugates of the disclosure, the GLP-1 / GIP agonist conjugates can be administered on a reduced dosing schedule, such as once weekly, once biweekly, once every three weeks, or once monthly. In some embodiments, the peptide is an endogenous opioid peptide. In some such embodiments, the peptide is endomorphin-1 or endomorphin-2. In other embodiments, the peptide is dermorphin. In some embodiments, D1is a protein. In some embodiments, D1 is a cytokine. In some embodiments, the cytokine isInterleukin-2 (IL-2). In some embodiments, the cytokine is mutated IL-2, such as a cytokine described in US 9,206,943. In some embodiments, the cytokine is Interleukin-15 (IL-15). In some embodiments, the cytokine is mutated IL-15. In one such embodiment, the IL-15 is IL- 15[N27D]. In some embodiments, the cytokine is Interleukin-7 (IL-7). In someAttorney Docket No. 330272000240embodiments, the cytokine is Interleukin-9 (IL-9). In some embodiments, the cytokine is Interleukin-10 (IL-10). In some embodiments, the cytokine is Interleukin-21 (IL-21). In some embodiments, the cytokine is Interleukin-10 (IL-10). In some embodiments, D1is an anti-cancer agent. In some such embodiments, D1isSN-38. In some such embodiments, D1 is monomethyl auristatin E. In some suchembodiments, D1 is capecitabine. In some such embodiments, D1 is irinotecan. In some suchembodiments, D1 is trifluridine. In some such embodiments, D1 is doxorubicin. In somesuch embodiments, D1 is docetaxel. In some such embodiments, D1 is infigratinib.In some embodiments, D1 is an opioid antagonist. In some embodiments, the opioidantagonist is naloxone, nalmefene, naltrexone, methylnaltrexone, nalbuphine, or nalorphine. In some embodiments, D1 is an opioid agonist. In some embodiments, the opioidagonist is morphine, oxycodone, hydromorphone, or methadone. In some embodiments, T (a ligand selective for transthyretin TTR) has the structure of Compound (A): (A), or a pharmaceutically acceptable salt thereof, wherein: Xa, Xb and Xc are independently selected from C(R8a)(R8b), O, N-R8bor S; where R8aand R8bare independently selected from hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl, aryl, substituted aryl, alkoxy, aryloxy, hydroxyl, heterocyclic group, halogen, nitro, acyl, substituted acyl, carboxyl, alkoxycarbonyl, substituted alkoxycarbonyl, aminoacyl, substituted aminoacyl, amino, substituted amino, acylamino, substituted acylamino, and cyano; a ring is a 4 to 12-membered ring, in certain embodiments the 4 to 12-membered ring is an aromatic or heteroaromatic ring; Attorney Docket No.330272000240 each Y is independently selected from hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl, aryl, substituted aryl, alkoxy, aryloxy, hydroxyl, heterocyclic group, halogen, nitro, acyl, substituted acyl, carboxyl, alkoxycarbonyl, substituted alkoxycarbonyl, aminoacyl, substituted aminoacyl, amino, substituted amino, acylamino, substituted acylamino, sulfonamide, sulfonyl fluoride, thioester and cyano; c is an integer ranging from 0 to 5; and, B ring is a heterocyclic ring selected from the following (h1-h30):

[0003] Attorney Docket No.330272000240

[0004] Attorney Docket No. 330272000240 where R11-R16are independently selected from hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl, aryl, substituted aryl, alkoxy, aryloxy, hydroxyl, heterocyclic group, halogen, nitro, acyl, substituted acyl, carboxyl, alkoxycarbonyl, substituted alkoxycarbonyl, aminoacyl, substituted aminoacyl, amino, substituted amino, acylamino, substituted acylamino, and cyano; R17is selected from a hydroxyl, alkyl, amino, and alkyl amino; and at least one of R11-R16is the linking group to Xc. In some embodiments, T (a ligand selective for transthyretin TTR) has the structure of Compound (B): or a pharmaceutically acceptable salt thereof, wherein: n is an integer ranging from 0 to 8; R18, R19and R20are independently selected from hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl, aryl, substituted aryl, alkoxy, aryloxy, hydroxyl, heterocyclic group, halogen, nitro, acyl, substituted acyl, carboxyl, alkoxycarbonyl, substituted alkoxycarbonyl,Attorney Docket No. 330272000240aminoacyl, substituted aminoacyl, amino, substituted amino, acylamino, substituted acylamino, sulfonamide, sulfonyl fluoride, thioester and cyano; Xais C(R21)(R22), O, N-R22or S; where R21and R22are independently selected from hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl, aryl, substituted aryl, alkoxy, aryloxy, hydroxyl, heterocyclic group, halogen, nitro, acyl, substituted acyl, carboxyl, alkoxycarbonyl, substituted alkoxycarbonyl, aminoacyl, substituted aminoacyl, amino, substituted amino, acylamino, substituted acylamino, and cyano; A is a 5 to 12-membered ring, in certain embodiments the 5 to 12-membered ring is an aromatic or heteroaromatic ring; each Y is independently selected from hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl, aryl, substituted aryl, alkoxy, aryloxy, hydroxyl, heterocyclic group, halogen, nitro, acyl, substituted acyl, carboxyl, alkoxycarbonyl, substituted alkoxycarbonyl, aminoacyl, substituted aminoacyl, amino, substituted amino, acylamino, substituted acylamino, sulfonamide, sulfonyl fluoride, thioester and cyano; and, c is a number from zero to 5. In some embodiments, T (a ligand selective for transthyretin TTR) has the structure of Compound (C): or a pharmaceutically acceptable salt thereof, wherein: n is an integer ranging from 1 to 4; R23is a short chain alkyl having 1 to 4 carbon atoms; R24is hydrogen; R25is a short chain alkyl having 1 to 4 carbon atoms; Xa is C(R21)(R22), O, N-R22or S; where R21and R22are independently selected from hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl,Attorney Docket No. 330272000240substituted alkynyl, aryl, substituted aryl, alkoxy, aryloxy, hydroxyl, heterocyclic group, halogen, nitro, acyl, substituted acyl, carboxyl, alkoxycarbonyl, substituted alkoxycarbonyl, aminoacyl, substituted aminoacyl, amino, substituted amino, acylamino, substituted acylamino, andcyano; each Y is independently selected from hydrogen, halogen, acyl, substituted acyl, carboxyl, heterocyclic group, alkoxycarbonyl sulfonamide, sulfonyl fluoride, thioester and substituted alkoxycarbonyl; and c is 2. In some embodiments, the ligand of Compound (C) is a structure in which R23ismethyl and R24 is methyl; Xa is O; and Y is fluoro or carboxyl.In some embodiments, T (a ligand selective for transthyretin TTR) has the structure of Compound (D): or a pharmaceutically acceptable salt thereof, wherein: n is 1 to 8; R23, R24and R25are independently selected from hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl, aryl, substituted aryl, alkoxy, aryloxy, hydroxyl, heterocyclic group, halo, nitro, acyl, substituted acyl, carboxyl, alkoxycarbonyl, substituted alkoxycarbonyl, aminoacyl, substituted aminoacyl, amino, substituted amino, acylamino, substituted acylamino, and cyano; Xa is C(R21)(R22), O, N-R22or S; where R21and R22are independently selected from hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl, aryl, substituted aryl, alkoxy, aryloxy, hydroxyl, heterocyclic group, halogen, nitro, acyl, substituted acyl, carboxyl, alkoxycarbonyl, substituted alkoxycarbonyl, aminoacyl, substitutedAttorney Docket No. 330272000240aminoacyl, amino, substituted amino, acylamino, substituted acylamino, and cyano; Rais CHO, COOH, COOCH3, COOR6, CONR7R8, tetrazolyl, CONHOH, B(OH)2, CONHSO2Ar, CONHCH(R9)COOH, CF3, hydrogen, halogen, alkyl, substituted alkyl, acyl, substituted acyl, carboxyl, heterocyclic group, sulfonamide, sulfonyl fluoride, thioester, alkoxycarbonyl or substituted alkoxycarbonyl; Rbis CHO, COOH, COOCH3, COOR26, CONR27R28, tetrazolyl, CONHOH, B(OH)2, CONHSO2Ar, CONHCH(R29)COOH, CF3, hydrogen, halogen, alkyl, substituted alkyl, acyl, substituted acyl, carboxyl, heterocyclic group, sulfonamide, sulfonyl fluoride, thioester, alkoxycarbonyl or substituted alkoxycarbonyl; R26is alkyl, haloalkyl, cycloalkyl, or heterocyclyl; R27and R28are each independently hydrogen, alkyl, alkenyl, alkynyl, cycloalkyl, heterocyclyl, or heteroaryl; and, R29is the side chain of a naturally occurring α-amino carboxylic acid. In some embodiments, the ligand of Compound (D) is a structure in which Rbis selected from bromo, chloro and fluoro. In some embodiments, the ligand of Compound (D) is a structure of Compound (E): or a pharmaceutically acceptable salt thereof. In some embodiments, T (a ligand selective for transthyretin TTR) has the structure of Compound (F):Attorney Docket No. 330272000240 or a pharmaceutically acceptable salt thereof. In some embodiments, T (a ligand selective for transthyretin TTR) has the structure of Compound (G): or a pharmaceutically acceptable salt thereof, wherein Rais OH, CHO, COOH, CONH2, CONH(OH), COOR30, CONHR30; R30is straight of branched alkyl of 1-3 carbon atoms; In some embodiments, T (a ligand selective for transthyretin TTR) has the structure of Compound (H): or a pharmaceutically acceptable salt thereof.Attorney Docket No. 330272000240In some embodiments, T (a ligand selective for transthyretin TTR) has the structure of Compound (I): or a pharmaceutically acceptable salt thereof. In some embodiments, T (a ligand selective for transthyretin TTR) has the structure of Compound (K): or a pharmaceutically acceptable salt thereof. In some embodiments, T (a ligand selective for transthyretin TTR) has the structure of Compound (L): or a pharmaceutically acceptable salt thereof.Attorney Docket No. 330272000240In some embodiments, T (a ligand selective for transthyretin TTR) has the structure of Compound (M): or a pharmaceutically acceptable salt thereof. In some embodiments, T (a ligand selective for transthyretin TTR) has the structure of Compound (N): or a pharmaceutically acceptable salt thereof. In some embodiments, T (a ligand selective for transthyretin TTR) has the structure of Compound (O):Attorney Docket No. 330272000240 or a pharmaceutically acceptable salt thereof. In some embodiments, T (a ligand selective for transthyretin TTR) has the structure of Compound (P): or a pharmaceutically acceptable salt thereof. In some embodiments, T (a ligand selective for transthyretin TTR) has the structure of Compound (Q): or a pharmaceutically acceptable salt thereof.Attorney Docket No. 330272000240In some embodiments, T (a ligand selective for transthyretin TTR) has the structure of Compound (R): or a pharmaceutically acceptable salt thereof. In some embodiments, T (a ligand selective for transthyretin TTR) has the structure of Compound (S): or a pharmaceutically acceptable salt thereof. In some embodiments, T (a ligand selective for transthyretin TTR) has the structure of Compound (T):Attorney Docket No. 330272000240 or a pharmaceutically acceptable salt thereof. In some embodiments, T (a ligand selective for transthyretin TTR) has the structure ofCompound (U): or a pharmaceutically acceptable salt thereof. In some embodiments, T (a ligand selective for transthyretin TTR) has the structure of Compound (V): or a pharmaceutically acceptable salt thereof. In some embodiments, T (a ligand selective for transthyretin TTR) has the structure of Compound (W):Attorney Docket No. 330272000240 or a pharmaceutically acceptable salt thereof. In some embodiments, T (a ligand selective for transthyretin TTR) has the structure of Compound (Y): or a pharmaceutically acceptable salt thereof. In some embodiments of Compound (Y), the linker (L) is attached to the ligand meta at C16 to the carboxy carbon at C14, such as conjugate of formula (Ia):

[0005] Attorney Docket No. 330272000240 In some embodiments of Compound (Y), the linker (L) is attached to the ligand ortho at C15 to the carboxy carbon at C15, such as conjugate of formula (Ib): In some embodiments, T (a ligand selective for transthyretin TTR) has one of the following structures:Attorney Docket No. 330272000240 . In some embodiments, T (a ligand selective for transthyretin TTR) has one of the following structures: In some embodiments of a conjugate of formula (Ia) or formula (Ib), L is C4-20alkylene, wherein the C4-20alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, -NRx-, and -S-, wherein L1ais halo, C1-6alkyl, or C1-6alkyl substituted by halo. In some embodiments, L is C10-20alkylene, wherein the C10-20alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, -NH-, - N(CH3)-, and -S-. In some embodiments, L is C10-15alkylene, wherein the C10-15alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, -NH-, and -N(CH3)-. In some embodiments, L is C5-10alkylene, wherein the C5-10alkylene is optionally substituted with one or more L1a, and oneor more alkylene units is optionally replaced with a group selected from -O-, and -NH-.Attorney Docket No. 330272000240In some embodiments of formula (Ia) or formula (Ib), L comprises the moiety comprises the moiety . In some embodiments, L comprises the moiety . In some embodiments, L embodiments, L comprises the moiety .Attorney Docket No. 330272000240In some embodiments, L comprises the moiety . In some embodiments, L comprises the moiety embodiments, L comprises the moiety someembodiments, L comprises the moiety . In someembodiments, L comprises the moiety .In some embodiments, L-LBcomprises the moiety LBAttorney Docket No. 330272000240 embodiments, L-LBcomprises the moiety embodiments, L-LBcomprises the moiety . In some embodiments of formula (Ia) or formula (Ib), L-LBcomprises the moiety Attorney Docket No. 330272000240 In one embodiment, provided herein is a conjugate of formula (II’): or a pharmaceutically acceptable salt thereof, wherein: each R1is independently halo or C1-4alkyl;m is 0, 1, 2, or 3;R2is H or C1-4alkyl;X1 is -O- or -NRx-;n is 0, 1, 2, 3, or 4; R3is H or C1-4alkyl; R4is H or C1-4alkyl; R5is H or C1-4alkyl; Rxis H or C1-4alkyl;Attorney Docket No. 330272000240L is a linker; Y1is a bond or C1-4alkylene; Y2is NR6, O or S; R6is H or C1-4alkyl;each R7 is independently selected from the group consisting of hydrogen, halogen atoms(e.g., Cl, Br or F), NO2, CF3, OMe, O(C1-4 alkyl), hydroxy, -OCF3, -NH2, -NHC1-4 alkyl, - N(C1-4alkyl)2, -CONH2, -CONHC1-4alkyl, -CON(C1-4alkyl)2, -NHCOC1-4alkyl, C1-6alkyl, C1-6alkoxy and C3-6cycloalkyl; p is 0, 1, 2, or 3; and D1is a drug moiety. In one embodiment, provided herein is a conjugate of formula (II): or a pharmaceutically acceptable salt thereof, wherein: each R1is independently halo or C1-4alkyl;m is 0, 1, 2, or 3;R2is H or C1-4alkyl;X1 is -O- or -NRx-;n is 0, 1, 2, 3, or 4; R3is H or C1-4alkyl;Attorney Docket No. 330272000240R4is H or C1-4alkyl; R5is H or C1-4alkyl; Rxis H or C1-4alkyl; L is a linker; Y1is a bond or C1-4alkylene; Y2is NR6, O or S; R6is H or C1-4alkyl;each R7 is independently selected from the group consisting of hydrogen, halogen atoms(e.g., Cl, Br or F), NO2, CF3, OMe, O(C1-4 alkyl), hydroxy, -OCF3, -NH2, -NHC1-4 alkyl, -N(C1-4 alkyl)2, -CONH2, -CONHC1-4 alkyl, -CON(C1-4 alkyl)2, -NHCOC1-4 alkyl, C1-6 alkyl, C1-6alkoxy and C3-6cycloalkyl; p is 0, 1, 2, or 3; and D1is a drug moiety. In some embodiments, the conjugate of formula (II) has the formula (IIa): or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (II) has the formula (IIb):Attorney Docket No. 330272000240 or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (II) has the formula (IIc): or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (II) has the formula (IId):Attorney Docket No. 330272000240 or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (II) has the formula (IIe): or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (II) has the formula (IIf):Attorney Docket No. 330272000240 or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (II) has the formula (IIg): or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (II) has the formula (IIh):Attorney Docket No. 330272000240 or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (II) has the formula (IIi): or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (II’) has the formula (IIj):Attorney Docket No. 330272000240 or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (II’) has the formula (IIk): or a pharmaceutically acceptable salt thereof. In some embodiments of the conjugate of formula (II) or (II’), or any variationthereof, such as formula (IIa)-(IIk), R2is H or C1-2alkyl. In some embodiments, R2is H or - CH3. In some embodiments, R2is H. In some embodiments of the conjugate of formula (II) or (II’), or any variationthereof, such as formula (IIa)-(IIk), R3is H or C1-2alkyl. In some embodiments, R3is H or - CH3. In some embodiments, R3is H. In some embodiments of the conjugate of formula (II) or (II’), or any variationthereof, such as formula (IIa)-(IIk), R4is H or C1-2 alkyl. In some embodiments, R4is H or - CH3. In some embodiments, R4is -CH3.Attorney Docket No. 330272000240In some embodiments of the conjugate of formula (II) or (II’), or any variationthereof, such as formula (IIa)-(IIk), R5is H or C1-2alkyl. In some embodiments, R5is H or - CH3. In some embodiments, R5is -CH3. In some embodiments of the conjugate of formula (II) or (II’), or any variationthereof, such as formula (IIa)-(IIh), (IIj), or (IIk), n is 2 or 3. In some embodiments, n is 3.In some embodiments of the conjugate of formula (II) or (II’), or any variationthereof, such as formula (IIa)-(IIh), or (IIj), m is 0, 1, or 2. In some embodiments, m is 0 or 1.In some embodiments, m is 0. In some embodiments, m is 1. In some embodiments of the conjugate of formula (II) or (II’), or any variationthereof, such as formula (IIa)-(IIh), or (IIj), p is 0, 1, or 2. In some embodiments, p is 0 or 1.In some embodiments, p is 0. In some embodiments, p is 1. In some embodiments of the conjugate of formula (II) or (II’), or any variationthereof, such as formula (IIa)-(IIk), L is C4-20alkylene, wherein the C4-20alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, -NRx-, and -S-, wherein L1ais halo, C1-6alkyl, or C1-6alkyl substituted by halo. In some embodiments, L is C10-20alkylene, wherein the C10-20alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, -NH-, -N(CH3)-, and -S-. In some embodiments, L is C10-15alkylene, wherein the C10-15alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, -NH-, and -N(CH3)-. In some embodiments, L is C5-10alkylene, wherein the C5-10alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, and -NH-. In some embodiments of the conjugate of formula (II) or (II’), or any variationthereof, such as formula (IIa)-(IIi), L comprises the moiety some embodiments, L comprises the moiety Attorney Docket No.330272000240 some embodiments, L comprises the Attorney Docket No. 330272000240 . In some embodiments of a conjugate of formula (II) or (II’), or any variation thereof,such as formula (IIa)-(IIk), D1is a protein. In some embodiments, D1is a cytokine. In some embodiments, the cytokine is Interleukin-2 (IL-2). In some embodiments, the cytokine is mutated IL-2, such as a cytokine described in US 9,206,943. In some embodiments, the cytokine is Interleukin-15 (IL-15). In some embodiments, the cytokine is mutated IL-15. In one such embodiment, the IL-15 is IL-15[N27D]. In some embodiments, the cytokine is Interleukin-7 (IL-7). In some embodiments, the cytokine is Interleukin-9 (IL-9). In someembodiments, the cytokine is Interleukin-10 (IL-10). In some embodiments, the cytokine isInterleukin-21 (IL-21). In some embodiments, the cytokine is Interleukin-10 (IL-10). In some embodiments of a conjugate of formula (II) or (II’), or any variation thereof,such as formula (IIa)-(IIk), D1is an anti-cancer agent. In some such embodiments, D1is SN-38. In some such embodiments, D1 is monomethyl auristatin E. In some such embodiments,D1 is capecitabine. In some such embodiments, D1 is irinotecan. In some such embodiments,Attorney Docket No. 330272000240D1 is trifluridine. In some such embodiments, D1 is doxorubicin. In some suchembodiments, D1 is docetaxel. In some such embodiments, D1 is infigratinib.In some embodiments of a conjugate of formula (II) or (II’), or any variation thereof,such as formula (IIa)-(IIk), D1 is a peptide.In some embodiments, the peptide is RGK-MCA. In some embodiments, the peptide is Neurotensin. In some embodiments, the peptide is Gonadotropin-releasing hormone (GnRH). In some embodiments, the peptide is GIP (1-42), human peptide. In someembodiments, the peptide is D6-GnRH. In some embodiments, the peptide is insulin. Insome embodiments, the peptide is teriparatide. In some embodiments, the peptide iscalcitronin salmon. In some embodiments, the peptide is ipamorelin. In some embodiments, the peptide is vasopressin. In some embodiments, the peptide is glucagon. In some embodiments, the peptide is aclerastide. In some embodiments, the peptide is goserelin. In some embodiments, the peptide is leuprolide. In some embodiments, the peptide is teriparatide. In some embodiments, the peptide is lixisenatide. In some embodiments, the peptide is desmopressin. In some embodiments, the peptide is oxytocin. In some embodiments, the peptide is corticotropin. In some embodiments, the peptide is sermorelin. In some embodiments, the peptide is bremelanotide. In some embodiments, the peptide is abaloparatide. In some embodiments, the peptide is deslorelin. In some embodiments, the peptide drug is a glucagon-like-peptide-1 (GLP-1) receptor agonist used to trat obesity and / or diabetes. In some such embodiments the peptidedrug is semaglutide, liraglutide, dulaglutide, albiglutide, or exenatide. Owing to the dramaticextension of duration of action of peptide drugs when incorporated into the conjugates of the disclosure, the GLP-1 agonist conjugates can be administered on a reduced dosing schedule, such as once weekly, once biweekly, once every three weeks, or once monthly. In some embodiments, the peptide drug is a glucagon-like-peptide-1 (GLP-1) and GIP (glucose-dependent insulinotropic polypeptide receptor agonist used to trat obesity and / or diabetes. In some such embodiments, the peptide drug is tirzepatide. Owing to the dramatic extension of duration of action of peptide drugs when incorporated into the conjugates of the disclosure, the GLP-1 / GIP agonist conjugates can be administered on a reduced dosing schedule, such as once weekly, once biweekly, once every three weeks, or once monthly.Attorney Docket No. 330272000240In some embodiments, the peptide is an endogenous opioid peptide. In some such embodiments, the peptide is endomorphin-1 or endomorphin-2. In other embodiments, the peptide is dermorphin. In some embodiments of a conjugate of formula (II) or (II’), or any variation thereof,such as formula (IIa)-(IIk), D1 is an opioid antagonist. In some embodiments, the opioidantagonist is naloxone, nalmefene, naltrexone, methylnaltrexone, nalbuphine, or nalorphine. In some embodiments of a conjugate of formula (II) or (II’), or any variation thereof,such as formula (IIa)-(IIk), D1 is an opioid agonist. In some embodiments, the opioid agonistis morphine, oxycodone, hydromorphone, or methadone. In one embodiment, provided herein is a conjugate of formula (III’): or a pharmaceutically acceptable salt thereof, wherein: each R1is independently halo or C1-4alkyl; m is 0, 1, 2, or 3; R2is H or C1-4alkyl;X1 is -O- or -NRx-;n is 0, 1, 2, 3, or 4; R3is H or C1-4alkyl; R4is H or C1-4alkyl;Attorney Docket No. 330272000240R5is H or C1-4alkyl; Rxis H or C1-4alkyl; LAis C3-20alkylene, wherein the C3-20alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, - NRy-, and -S-; each L1ais halo, C1-6alkyl, or C1-6alkyl substituted by halo; each Ryis H or C1-4alkyl; LBis a click product formed via a Click reaction between a first Click handle and a second click handle; Y1is a bond or C1-4alkylene; Y2is NR6, O, or S; R6is H or C1-4alkyl;each R7 is independently selected from the group consisting of hydrogen, halogen atoms(e.g., Cl, Br or F), NO2, CF3, OMe, O(C1-4alkyl), hydroxy, -OCF3, -NH2, -NHC1-4alkyl, - N(C1-4 alkyl)2, -CONH2, -CONHC1-4 alkyl, -CON(C1-4 alkyl)2, -NHCOC1-4 alkyl, C1-6 alkyl, C1-6 alkoxy and C3-6 cycloalkyl; p is 0, 1, 2, or 3; and D1is a drug moiety. In one embodiment, provided herein is a conjugate of formula (III): Attorney Docket No. 330272000240or a pharmaceutically acceptable salt thereof, wherein: each R1is independently halo or C1-4alkyl; m is 0, 1, 2, or 3; R2is H or C1-4alkyl;X1 is -O- or -NRx-;n is 0, 1, 2, 3, or 4; R3is H or C1-4alkyl; R4is H or C1-4alkyl; R5is H or C1-4alkyl; Rxis H or C1-4alkyl; LAis C3-20alkylene, wherein the C3-20alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, - NRy-, and -S-; each L1ais halo, C1-6alkyl, or C1-6alkyl substituted by halo; each Ryis H or C1-4alkyl; LBis a click product formed via a Click reaction between a first Click handle and a second click handle; Y1is a bond or C1-4alkylene; Y2is NR6, O, or S; R6is H or C1-4alkyl;each R7 is independently selected from the group consisting of hydrogen, halogen atoms(e.g., Cl, Br or F), NO2, CF3, OMe, O(C1-4alkyl), hydroxy, -OCF3, -NH2, -NHC1-4alkyl, - N(C1-4 alkyl)2, -CONH2, -CONHC1-4 alkyl, -CON(C1-4 alkyl)2, -NHCOC1-4 alkyl, C1-6 alkyl, C1-6 alkoxy and C3-6 cycloalkyl; p is 0, 1, 2, or 3; and D1is a drug moiety. In some embodiments, the conjugate of formula (III) has the formula (IIIa):Attorney Docket No. 330272000240 In some embodiments, the conjugate of formula (III) has the formula (IIIb): or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (III) has the formula (IIIc):Attorney Docket No. 330272000240 In some embodiments, the conjugate of formula (III) has the formula (IIId): In some embodiments, the conjugate of formula (III) has the formula (IIIe):Attorney Docket No. 330272000240 or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (III) has the formula (IIIf): or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (III) has the formula (IIIg):Attorney Docket No. 330272000240 or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (III) has the formula (IIIh): In some embodiments, the conjugate of formula (III) has the formula (IIIi):Attorney Docket No. 330272000240 or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (III’) has the formula (IIIj): or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (III’) has the formula (IIIk):Attorney Docket No. 330272000240 or a pharmaceutically acceptable salt thereof. In some embodiments of the conjugate of formula (III) or (III’), or any variationthereof, such as formula (IIIa)-(IIIk), R2is H or C1-2 alkyl. In some embodiments, R2is H or - CH3. In some embodiments, R2is H. In some embodiments of the conjugate of formula (III) or (III’), or any variationthereof, such as formula (IIIa)-(IIIk), R3is H or C1-2 alkyl. In some embodiments, R3is H or - CH3. In some embodiments, R3is H. In some embodiments of the conjugate of formula (III) or (III’), or any variationthereof, such as formula (IIIa)-(IIIk), R4is H or C1-2 alkyl. In some embodiments, R4is H or - CH3. In some embodiments, R4is -CH3. In some embodiments of the conjugate of formula (III) or (III’), or any variationthereof, such as formula (IIIa)-(IIIk), R5is H or C1-2 alkyl. In some embodiments, R5is H or - CH3. In some embodiments, R5is -CH3. In some embodiments of the conjugate of formula (III) or (III’), or any variationthereof, such as formula (IIIa)-(IIIk), n is 2 or 3. In some embodiments, n is 3. In some embodiments of the conjugate of formula (III) or (III’), or any variationthereof, such as formula (IIIa)-(IIIj), m is 0, 1, or 2. In some embodiments, m is 0 or 1. In some embodiments, m is 0. In some embodiments, m is 1. In some embodiments of the conjugate of formula (III) or (III’), or any variationthereof, such as formulas (IIIa), (IIIb), or (IIId)-(IIIj), p is 0, 1, or 2. In some embodiments, p is 0 or 1. In some embodiments, p is 0. In some embodiments, p is 1.Attorney Docket No. 330272000240In some embodiments of a conjugate of formula (III) or (III’), or any variationthereof, such as formula (IIIa)-(IIIk), LAis C4-20alkylene, wherein the C4-20alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, -NRx-, and -S-, wherein L1ais halo, C1-6alkyl, or C1-6alkyl substituted by halo, and wherein Rxis H or C1-6alkyl optionally substituted by halo. In some embodiments, LAis C10-20alkylene, wherein the C10-20alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, -NH-, -N(CH3)-, and -S-. In some embodiments, LAis C10-15alkylene, wherein the C10-15alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, -NH-, and -N(CH3)-. In some embodiments, LAis C5-10alkylene, wherein the C5-10alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, and -NH-. In some embodiments of a conjugate of formula (III) or (III’), or any variationthereof, such as formula (IIIa)-(IIIk), LAcomprises the moiety some embodiments, LAcomprises the moiety . Attorney Docket No.330272000240 the moiety . In some embodiments, LAcomprises the Attorney Docket No. 330272000240 . In some embodiments of a conjugate of formula (III) or (III’), or any variationthereof, such as formula (IIIa)-(IIIk), the click product LBis a triazine moiety. In someembodiments, the conjugate of formula (III) or (III’), any of formula (IIIa)-(IIIi), comprisesone of the following moieties: , wherein X2 is -CH2-, -NRx-, -S- or -O-, wherein Rx is as definedelsewhere herein. In some embodiments, the conjugate comprises the moiety In some embodiments, the conjugate comprises the moiety . In some embodiments of a conjugate of formula (III) or (III’), or any variationthereof, such as formula (IIIa)-(IIIk), LA-LBcomprises the moiety . In some embodiments, LA-LBcomprises theAttorney Docket No. 330272000240 embodiments, LA-LBcomprises the moiety some embodiments, LA-LBcomprises the moiety . In some embodiments of a conjugate of formula (III) or (III’), or any variationthereof, such as formula (IIIa)-(IIIk), LA-LBcomprises the moiety Attorney Docket No. 330272000240 , wherein R9is H or C1-4 alky1, R10is H or C1-4 alky1, and Q is -CH2-, -O-, -S-, -NH-, or -N(C1-4alkyl)-. In some embodiments of a conjugate of formula (III) or (III’), or any variationthereof, such as formula (IIIa)-(IIIk), D1 is a protein. In some embodiments, D1 is a cytokine.In some embodiments, the cytokine is Interleukin-2 (IL-2). In some embodiments, the cytokine is mutated IL-2, such as a cytokine described in US 9,206,943. In some embodiments, the cytokine is Interleukin-15 (IL-15). In some embodiments, the cytokine is mutated IL-15. In one such embodiment, the IL-15 is IL-15[N27D]. In some embodiments, the cytokine is Interleukin-7 (IL-7). In some embodiments, the cytokine is Interleukin-9 (IL- 9). In some embodiments, the cytokine is Interleukin-10 (IL-10). In some embodiments, the cytokine is Interleukin-21 (IL-21). In some embodiments, the cytokine is Interleukin-10 (IL- 10). In some embodiments of a conjugate of formula (III) or (III’), or any variationthereof, such as formula (IIIa)-(IIIk), D1 is a peptide. In some embodiments, the peptide isRGK-MCA. In some embodiments, the peptide is Neurotensin. In some embodiments, the peptide is Gonadotropin-releasing hormone (GnRH). In some embodiments, the peptide is GIP (1-42), human peptide. In some embodiments, the peptide is D6-GnRH. In someembodiments, the peptide is insulin. In some embodiments, the peptide is teriparatide. Insome embodiments, the peptide is calcitronin salmon. In some embodiments, the peptide is ipamorelin. In some embodiments, the peptide is vasopressin. In some embodiments, the peptide is glucagon. In some embodiments, the peptide is aclerastide. In some embodiments, the peptide is goserelin. In some embodiments, the peptide is leuprolide. In some embodiments, the peptide is teriparatide. In some embodiments, the peptide is lixisenatide. In some embodiments, the peptide is desmopressin. In some embodiments, the peptide is oxytocin. In some embodiments, the peptide is corticotropin. In some embodiments, the peptide is sermorelin. In some embodiments, the peptide is bremelanotide. In some embodiments, the peptide is abaloparatide. In some embodiments, the peptide is deslorelin.Attorney Docket No. 330272000240In some embodiments, the peptide drug is a glucagon-like-peptide-1 (GLP-1) receptor agonist used to trat obesity and / or diabetes. In some such embodiments the peptidedrug is semaglutide, liraglutide, dulaglutide, albiglutide, or exenatide. Owing to the dramaticextension of duration of action of peptide drugs when incorporated into the conjugates of the disclosure, the GLP-1 agonist conjugates can be administered on a reduced dosing schedule, such as once weekly, once biweekly, once every three weeks, or once monthly. In some embodiments, the peptide drug is a glucagon-like-peptide-1 (GLP-1) and GIP (glucose-dependent insulinotropic polypeptide receptor agonist used to trat obesity and / or diabetes. In some such embodiments, the peptide drug is tirzepatide. Owing to the dramatic extension of duration of action of peptide drugs when incorporated into the conjugates of the disclosure, the GLP-1 / GIP agonist conjugates can be administered on a reduced dosing schedule, such as once weekly, once biweekly, once every three weeks, or once monthly. In some embodiments, the peptide is an endogenous opioid peptide. In some such embodiments, the peptide is endomorphin-1 or endomorphin-2. In other embodiments, the peptide is dermorphin. In some embodiments of a conjugate of formula (III) or (III’), or any variationthereof, such as formula (IIIa)-(IIIk), D1is an anti-cancer agent. In some such embodiments,D1 is SN-38. In some such embodiments, D1 is monomethyl auristatin E. In some suchembodiments, D1 is capecitabine. In some such embodiments, D1 is irinotecan. In some suchembodiments, D1 is trifluridine. In some such embodiments, D1 is doxorubicin. In somesuch embodiments, D1 is docetaxel. In some such embodiments, D1 is infigratinib.In some embodiments of a conjugate of formula (III) or (III’), or any variationthereof, such as formula (IIIa)-(IIIk), D1is an opioid antagonist. In some embodiments, the opioid antagonist is naloxone, nalmefene, naltrexone, methylnaltrexone, nalbuphine, or nalorphine. In some embodiments of a conjugate of formula (III) or (III’), or any variationthereof, such as formula (IIIa)-(IIIk), D1 is an opioid agonist. In some embodiments, theopioid agonist is morphine, oxycodone, hydromorphone, or methadone. In one embodiment, provided herein is a conjugate of formula (IV’): Attorney Docket No.330272000240 or a pharmaceutically acceptable salt thereof, wherein: each R1is independently halo or C1-4alkyl; m is 0, 1, 2, or 3; R2is H or C1-4alkyl; X1is -O- or -NRx-; n is 0, 1, 2, 3, or 4; R3is H or C1-4alkyl; R4is H or C1-4alkyl; R5is H or C1-4alkyl; Rxis H or C1-4alkyl; LAis C3-20alkylene, wherein the C3-20alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, - NRy-, and -S-; each L1ais halo, C1-6alkyl, or C1-6alkyl substituted by halo; each Ryis H or C1-4alkyl; LBis a click product formed via a Click reaction between a first Click handle and a second click handle;Attorney Docket No. 330272000240Y1is a bond or C1-4alkylene; Y2is NR6, O, or S; R6is H or C1-4alkyl;each R7 is independently selected from the group consisting of hydrogen, halogen atoms(e.g., Cl, Br or F), NO2, CF3, OMe, O(C1-4 alkyl), hydroxy, -OCF3, -NH2, -NHC1-4 alkyl, - N(C1-4alkyl)2, -CONH2, -CONHC1-4alkyl, -CON(C1-4alkyl)2, -NHCOC1-4alkyl, C1-6alkyl, C1-6alkoxy and C3-6cycloalkyl; p is 0, 1, 2, or 3; and D1is a drug moiety. In one embodiment, provided herein is a conjugate of formula (IV): or a pharmaceutically acceptable salt thereof, wherein: each R1is independently halo or C1-4alkyl; m is 0, 1, 2, or 3; R2is H or C1-4alkyl;X1 is -O- or -NRx-;n is 0, 1, 2, 3, or 4; R3is H or C1-4alkyl; R4is H or C1-4alkyl; R5is H or C1-4alkyl;Attorney Docket No. 330272000240Rxis H or C1-4alkyl; LAis C3-20alkylene, wherein the C3-20alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, - NRy-, and -S-; each L1ais halo, C1-6alkyl, or C1-6alkyl substituted by halo; each Ryis H or C1-4alkyl; LBis a click product formed via a Click reaction between a first Click handle and a second click handle; Y1is a bond or C1-4alkylene; Y2is NR6, O, or S; R6is H or C1-4alkyl;each R7 is independently selected from the group consisting of hydrogen, halogen atoms(e.g., Cl, Br or F), NO2, CF3, OMe, O(C1-4alkyl), hydroxy, -OCF3, -NH2, -NHC1-4alkyl, - N(C1-4alkyl)2, -CONH2, -CONHC1-4alkyl, -CON(C1-4alkyl)2, -NHCOC1-4alkyl, C1-6alkyl, C1-6 alkoxy and C3-6 cycloalkyl; p is 0, 1, 2, or 3; and D1is a drug moiety. In some embodiments, the conjugate of formula (IV) has the formula (IVa): or a pharmaceutically acceptable salt thereof.Attorney Docket No. 330272000240In some embodiments, the conjugate of formula (IV) has the formula (IVb): or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (IV) has the formula (IVc): or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (IV) has the formula (IVd):Attorney Docket No. 330272000240 or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (IV) has the formula (IVe): or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (IV) has the formula (IVf):Attorney Docket No. 330272000240 or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (IV) has the formula (IVg): In some embodiments, the conjugate of formula (IV) has the formula (IVh):Attorney Docket No. 330272000240 or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (IV) has the formula (IVi): or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (IV’) has the formula (IVj):Attorney Docket No. 330272000240 or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (IV’) has the formula (IVk): or a pharmaceutically acceptable salt thereof. In some embodiments of the conjugate of formula (IV) or (IV’), or any variationthereof, such as formula (IVa)-(IVk), R2is H or C1-2alkyl. In some embodiments, R2is H or - CH3. In some embodiments, R2is H. In some embodiments of the conjugate of formula (IV) or (IV’), or any variationthereof, such as formula (IVa)-(IVk), R3is H or C1-2alkyl. In some embodiments, R3is H or - CH3. In some embodiments, R3is H. In some embodiments of the conjugate of formula (IV) or (IV’), or any variationthereof, such as formula (IVa)-(IVk), R4is H or C1-2alkyl. In some embodiments, R4is H or - CH3. In some embodiments, R4is -CH3.Attorney Docket No. 330272000240In some embodiments of the conjugate of formula (IV) or (IV’), or any variationthereof, such as formula (IVa)-(IVk), R5is H or C1-2alkyl. In some embodiments, R5is H or - CH3. In some embodiments, R5is -CH3. In some embodiments of the conjugate of formula (IV) or (IV’), or any variationthereof, such as formula (IVa)-(IVk), n is 2 or 3. In some embodiments, n is 3. In some embodiments of the conjugate of formula (IV) or (IV’), or any variationthereof, such as formula (IVa)-(IVj), m is 0, 1, or 2. In some embodiments, m is 0 or 1. In some embodiments, m is 0. In some embodiments, m is 1. In some embodiments of the conjugate of formula (IV) or (IV’), or any variationthereof, such as formula (IVa)-(IVj), p is 0, 1, or 2. In some embodiments, p is 0 or 1. In some embodiments, p is 0. In some embodiments, p is 1. In some embodiments of a conjugate of formula (IV) or (IV’), or any variationthereof, such as formula (IVa)-(IVk), LAis C4-20alkylene, wherein the C4-20alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, -NRx-, and -S-, wherein L1ais halo, C1-6alkyl, or C1-6alkyl substituted by halo, and wherein Rxis H or C1-6alkyl optionally substituted by halo. In some embodiments, LAis C10-20alkylene, wherein the C10-20alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, -NH-, -N(CH3)-, and -S-. In some embodiments, LAis C10-15alkylene, wherein the C10-15alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, -NH-, and -N(CH3)-. In some embodiments, LAis C5-10alkylene, wherein the C5-10alkylene is optionally substitutedwith one or more L1a, and one or more alkylene units is optionally replaced with a groupselected from -O-, and -NH-. In some embodiments of a conjugate of formula (IV) or (IV’), or any variationthereof, such as formula (IVa)-(IVk), LAcomprises the moiety some embodiments, LAcomprises the moiety Attorney Docket No.330272000240 Acomprises the moiety Attorney Docket No. 330272000240 . . In some embodiments of a conjugate of formula (IV) or (IV’), or any variationthereof, such as formula (IVa)-(IVk), D1is a protein. In some embodiments, D1is a cytokine. In some embodiments, the cytokine is Interleukin-2 (IL-2). In some embodiments, the cytokine is mutated IL-2, such as a cytokine described in US 9,206,943. In some embodiments, the cytokine is Interleukin-15 (IL-15). In some embodiments, the cytokine is mutated IL-15. In one such embodiment, the IL-15 is IL-15[N27D]. In some embodiments, the cytokine is Interleukin-7 (IL-7). In some embodiments, the cytokine is Interleukin-9 (IL-9). In some embodiments, the cytokine is Interleukin-10 (IL-10). In some embodiments, thecytokine is Interleukin-21 (IL-21). In some embodiments, the cytokine is Interleukin-10 (IL- 10). In some embodiments of a conjugate of formula (IV) or (IV’), or any variationthereof, such as formula (IVa)-(IVk), D1is an anti-cancer agent. In some such embodiments,D1 is SN-38. In some such embodiments, D1 is monomethyl auristatin E. In some suchAttorney Docket No. 330272000240embodiments, D1 is capecitabine. In some such embodiments, D1 is irinotecan. In some suchembodiments, D1 is trifluridine. In some such embodiments, D1 is doxorubicin. In somesuch embodiments, D1 is docetaxel. In some such embodiments, D1 is infigratinib.In some embodiments of a conjugate of formula (IV) or (IV’), or any variationthereof, such as formula (IVa)-(IVk), D1is a peptide. In some embodiments, the peptide is RGK-MCA. In some embodiments, the peptide is Neurotensin. In some embodiments, the peptide is Gonadotropin-releasing hormone (GnRH). In some embodiments, the peptide is GIP (1-42), human peptide. In someembodiments, the peptide is D6-GnRH. In some embodiments, the peptide is insulin. Insome embodiments, the peptide is teriparatide. In some embodiments, the peptide iscalcitronin salmon. In some embodiments, the peptide is ipamorelin. In some embodiments, the peptide is vasopressin. In some embodiments, the peptide is glucagon. In some embodiments, the peptide is aclerastide. In some embodiments, the peptide is goserelin. In some embodiments, the peptide is leuprolide. In some embodiments, the peptide is teriparatide. In some embodiments, the peptide is lixisenatide. In some embodiments, the peptide is desmopressin. In some embodiments, the peptide is oxytocin. In some embodiments, the peptide is corticotropin. In some embodiments, the peptide is sermorelin. In some embodiments, the peptide is bremelanotide. In some embodiments, the peptide is abaloparatide. In some embodiments, the peptide is deslorelin. In some embodiments, the peptide drug is a glucagon-like-peptide-1 (GLP-1) receptor agonist used to trat obesity and / or diabetes. In some such embodiments the peptidedrug is semaglutide, liraglutide, dulaglutide, albiglutide, or exenatide. Owing to the dramaticextension of duration of action of peptide drugs when incorporated into the conjugates of the disclosure, the GLP-1 agonist conjugates can be administered on a reduced dosing schedule, such as once weekly, once biweekly, once every three weeks, or once monthly. In some embodiments, the peptide drug is a glucagon-like-peptide-1 (GLP-1) and GIP (glucose-dependent insulinotropic polypeptide receptor agonist used to trat obesity and / or diabetes. In some such embodiments, the peptide drug is tirzepatide. Owing to the dramatic extension of duration of action of peptide drugs when incorporated into the conjugates of the disclosure, the GLP-1 / GIP agonist conjugates can be administered on a reduced dosing schedule, such as once weekly, once biweekly, once every three weeks, or once monthly.Attorney Docket No. 330272000240In some embodiments, the peptide is an endogenous opioid peptide. In some such embodiments, the peptide is endomorphin-1 or endomorphin-2. In other embodiments, the peptide is dermorphin. In some embodiments of a conjugate of formula (IV) or (IV’), or any variationthereof, such as formula (IVa)-(IVk), D1 is an opioid antagonist. In some embodiments, theopioid antagonist is naloxone, nalmefene, naltrexone, methylnaltrexone, nalbuphine, or nalorphine. In some embodiments of a conjugate of formula (IV) or (IV’), or any variationthereof, such as formula (IVa)-(IVk), D1 is an opioid agonist. In some embodiments, theopioid agonist is morphine, oxycodone, hydromorphone, or methadone. In some embodiments, provided herein is a conjugate of formula (V’): or a pharmaceutically acceptable salt thereof, wherein: each R1is independently halo or C1-4alkyl; m is 0, 1, 2, or 3; R2is H or C1-4alkyl;X1 is -O- or -NRx-;n is 0, 1, 2, or 3; R3is H or C1-4alkyl; R4is H or C1-4alkyl;Attorney Docket No. 330272000240R5is H or C1-4alkyl; Rxis H or C1-4alkyl; LAis C3-20alkylene, wherein the C3-20alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, - NRy-, and -S-; each L1ais halo, C1-6alkyl, or C1-6alkyl substituted by halo; each Ryis H or C1-4alkyl; Y1is a bond or C1-4alkylene; Y2is NR6, O or S; R6is H or C1-4alkyl;each R7 is independently selected from the group consisting of hydrogen, halogen atoms(e.g., Cl, Br or F), hydroxy, -OCF3, -NH2, -NHC1-4 alkyl, -N(C1-4 alkyl)2, -CONH2, - CONHC1-4 alkyl, -CON(C1-4 alkyl)2, -NHCOC1-4 alkyl, C1-6 alkyl, C1-6 alkoxy and C3-6 cycloalkyl; p is 0, 1, 2, or 3; and D1is a drug moiety. In some embodiments, provided herein is a conjugate of formula (V): or a pharmaceutically acceptable salt thereof, wherein: each R1is independently halo or C1-4alkyl; m is 0, 1, 2, or 3;Attorney Docket No. 330272000240R2is H or C1-4alkyl;X1 is -O- or -NRx-;n is 0, 1, 2, or 3; R3is H or C1-4alkyl; R4is H or C1-4alkyl; R5is H or C1-4alkyl; Rxis H or C1-4alkyl; LAis C3-20alkylene, wherein the C3-20alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, - NRy-, and -S-; each L1ais halo, C1-6alkyl, or C1-6alkyl substituted by halo; each Ryis H or C1-4alkyl; Y1is a bond or C1-4alkylene; Y2is NR6, O or S; R6is H or C1-4alkyl;each R7 is independently selected from the group consisting of hydrogen, halogen atoms(e.g., Cl, Br or F), hydroxy, -OCF3, -NH2, -NHC1-4 alkyl, -N(C1-4 alkyl)2, -CONH2, - CONHC1-4 alkyl, -CON(C1-4 alkyl)2, -NHCOC1-4 alkyl, C1-6 alkyl, C1-6 alkoxy and C3-6 cycloalkyl; p is 0, 1, 2, or 3; and D1is a drug moiety. In some embodiments, the conjugate of formula (V) has the formula (Va):

[0006] Attorney Docket No. 330272000240 or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (V) has the formula (Vb): or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (V) has the formula (Vc):Attorney Docket No. 330272000240 or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (V) has the formula (Vd): or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (V) has the formula (Ve):Attorney Docket No. 330272000240 or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (V) has the formula (Vf): or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (V) has the formula (Vg):Attorney Docket No. 330272000240 or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (V’) has the formula (Vh): or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (V’) has the formula (Vi):

[0007] Attorney Docket No. 330272000240 or a pharmaceutically acceptable salt thereof. In some embodiments of the conjugate of formula (V) or (V’), or any variationthereof, such as formula (Va)-(Vi), R2is H or C1-2 alkyl. In some embodiments, R2is H or - CH3. In some embodiments, R2is H. In some embodiments of the conjugate of formula (V) or (V’), or any variationthereof, such as formula (Va)-(Vi), R3is H or C1-2 alkyl. In some embodiments, R3is H or - CH3. In some embodiments, R3is H. In some embodiments of the conjugate of formula (V) or (V’), or any variationthereof, such as formula (Va)-(Vi), R4is H or C1-2 alkyl. In some embodiments, R4is H or - CH3. In some embodiments, R4is -CH3. In some embodiments of the conjugate of formula (V) or (V’), or any variationthereof, such as formula (Va)-(Vi), R5is H or C1-2 alkyl. In some embodiments, R5is H or - CH3. In some embodiments, R5is -CH3. In some embodiments of the conjugate of formula (V) or (V’), or any variationthereof, such as formula (Va)-(Vi), n is 2 or 3. In some embodiments, n is 3. In some embodiments of the conjugate of formula (V) or (V’), or any variationthereof, such as formula (Va)-(Vh), m is 0, 1, or 2. In some embodiments, m is 0 or 1. In some embodiments, m is 0. In some embodiments, m is 1. In some embodiments of the conjugate of formula (V) or (V’), or any variationthereof, such as formula (Va)-(Vh), p is 0, 1, or 2. In some embodiments, p is 0 or 1. In some embodiments, p is 0. In some embodiments, p is 1. In some embodiments of a conjugate of formula (V) or (V’), or any variation thereof,such as formula (Va)-(Vi), LAis C4-20alkylene, wherein the C4-20alkylene is optionallyAttorney Docket No. 330272000240substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, -NRx-, and -S-, wherein L1ais halo, C1-6alkyl, or C1-6alkyl substituted by halo, and wherein Rxis H or C1-6alkyl optionally substituted by halo. In some embodiments, LAis C10-20alkylene, wherein the C10-20alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, -NH-, -N(CH3)-, and -S-. In some embodiments, LAis C10-15alkylene, wherein the C10-15alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, -NH-, and -N(CH3)-. In some embodiments, LAis C5-10alkylene, wherein the C5-10alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, and -NH-. In some embodiments of a conjugate of formula (V) or (V’), or any variation thereof,such as formula (Va)-(Vi), LAcomprises the moiety . In some embodiments, LAcomprises the moiety . the Attorney Docket No.330272000240 moiety . In some embodiments, LAcomprises the moiety . In some embodiments, LAcomprises the moiety . In some embodiments, LAcomprises the moiety . In some embodiments, LA .Attorney Docket No. 330272000240 . In some embodiments of a conjugate of formula (V) or (V’), or any variation thereof,such as formula (Va)-(Vi), D1is a protein. In some embodiments, D1is a cytokine. In some embodiments, the cytokine is Interleukin-2 (IL-2). In some embodiments, the cytokine is mutated IL-2, such as a cytokine described in US 9,206,943. In some embodiments, the cytokine is Interleukin-15 (IL-15). In some embodiments, the cytokine is mutated IL-15. In one such embodiment, the IL-15 is IL-15[N27D]. In some embodiments, the cytokine is Interleukin-7 (IL-7). In some embodiments, the cytokine is Interleukin-9 (IL-9). In some embodiments, the cytokine is Interleukin-10 (IL-10). In some embodiments, the cytokine is Interleukin-21 (IL-21). In some embodiments, the cytokine is Interleukin-10 (IL-10). In some embodiments of a conjugate of formula (V) or (V’), or any variation thereof,such as formula (Va)-(Vi), D1is an anti-cancer agent. In some such embodiments, D1is SN-38. In some such embodiments, D1 is monomethyl auristatin E. In some such embodiments,D1 is capecitabine. In some such embodiments, D1 is irinotecan. In some such embodiments,D1 is trifluridine. In some such embodiments, D1 is doxorubicin. In some suchembodiments, D1 is docetaxel. In some such embodiments, D1 is infigratinib.In some embodiments of a conjugate of formula (V) or (V’), or any variation thereof,such as formula (Va)-(Vi), D1 is a peptide.In some embodiments, the peptide is RGK-MCA. In some embodiments, the peptide is Neurotensin. In some embodiments, the peptide is Gonadotropin-releasing hormone (GnRH). In some embodiments, the peptide is GIP (1-42), human peptide. In someembodiments, the peptide is D6-GnRH. In some embodiments, the peptide is insulin. Insome embodiments, the peptide is teriparatide. In some embodiments, the peptide iscalcitronin salmon. In some embodiments, the peptide is ipamorelin. In some embodiments, the peptide is vasopressin. In some embodiments, the peptide is glucagon. In someAttorney Docket No. 330272000240embodiments, the peptide is aclerastide. In some embodiments, the peptide is goserelin. In some embodiments, the peptide is leuprolide. In some embodiments, the peptide is teriparatide. In some embodiments, the peptide is lixisenatide. In some embodiments, the peptide is desmopressin. In some embodiments, the peptide is oxytocin. In some embodiments, the peptide is corticotropin. In some embodiments, the peptide is sermorelin.In some embodiments, the peptide is bremelanotide. In some embodiments, the peptide isabaloparatide. In some embodiments, the peptide is deslorelin. In some embodiments, the peptide drug is a glucagon-like-peptide-1 (GLP-1) receptor agonist used to trat obesity and / or diabetes. In some such embodiments the peptidedrug is semaglutide, liraglutide, dulaglutide, albiglutide, or exenatide. Owing to the dramaticextension of duration of action of peptide drugs when incorporated into the conjugates of the disclosure, the GLP-1 agonist conjugates can be administered on a reduced dosing schedule, such as once weekly, once biweekly, once every three weeks, or once monthly. In some embodiments, the peptide drug is a glucagon-like-peptide-1 (GLP-1) and GIP (glucose-dependent insulinotropic polypeptide receptor agonist used to trat obesity and / or diabetes. In some such embodiments, the peptide drug is tirzepatide. Owing to the dramatic extension of duration of action of peptide drugs when incorporated into the conjugates of the disclosure, the GLP-1 / GIP agonist conjugates can be administered on a reduced dosing schedule, such as once weekly, once biweekly, once every three weeks, or once monthly. In some embodiments, the peptide is an endogenous opioid peptide. In some such embodiments, the peptide is endomorphin-1 or endomorphin-2. In other embodiments, the peptide is dermorphin. In some embodiments of a conjugate of formula (V) or (V’), or any variation thereof,such as formula (Va)-(Vi), D1 is an opioid antagonist. In some embodiments, the opioidantagonist is naloxone, nalmefene, naltrexone, methylnaltrexone, nalbuphine, or nalorphine. In some embodiments of a conjugate of formula (V) or (V’), or any variation thereof,such as formula (Va)-(Vi), D1 is an opioid agonist. In some embodiments, the opioid agonistis morphine, oxycodone, hydromorphone, or methadone. In some embodiments, provided herein is a conjugate of formula (VI’): Attorney Docket No.330272000240 or a pharmaceutically acceptable salt thereof, wherein: each R1is independently halo or C1-4alkyl; m is 0, 1, 2, or 3; R2is H or C1-4alkyl; X1is -O- or -NRx-; n is 0, 1, 2, or 3; R3is H or C1-4alkyl; R4is H or C1-4alkyl; R5is H or C1-4alkyl; Rxis H or C1-4alkyl; LAis C3-20alkylene, wherein the C3-20alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, - NRy-, and -S-; each L1ais halo, C1-6alkyl, or C1-6alkyl substituted by halo; each Ryis H or C1-4alkyl; Y1is a bond or C1-4alkylene; Y2is NR6, O or S; R6is H or C1-4alkyl;Attorney Docket No. 330272000240each R7 is independently selected from the group consisting of hydrogen, halogen atoms(e.g., Cl, Br or F), hydroxy, -OCF3, -NH2, -NHC1-4alkyl, -N(C1-4alkyl)2, -CONH2, - CONHC1-4alkyl, -CON(C1-4alkyl)2, -NHCOC1-4alkyl, C1-6alkyl, C1-6alkoxy and C3-6cycloalkyl; p is 0, 1, 2, or 3; and D1is a drug moiety. In some embodiments, provided herein is a conjugate of formula (VI): or a pharmaceutically acceptable salt thereof, wherein: each R1is independently halo or C1-4alkyl; m is 0, 1, 2, or 3; R2is H or C1-4alkyl;X1 is -O- or -NRx-;n is 0, 1, 2, or 3; R3is H or C1-4alkyl; R4is H or C1-4alkyl; R5is H or C1-4alkyl; Rxis H or C1-4alkyl; LAis C3-20alkylene, wherein the C3-20alkylene is optionally substituted with one or more L1a, andAttorney Docket No. 330272000240one or more alkylene units is optionally replaced with a group selected from -O-, - NRy-, and -S-; each L1ais halo, C1-6alkyl, or C1-6alkyl substituted by halo; each Ryis H or C1-4alkyl; Y1is a bond or C1-4alkylene; Y2is NR6, O or S; R6is H or C1-4alkyl;each R7 is independently selected from the group consisting of hydrogen, halogen atoms(e.g., Cl, Br or F), hydroxy, -OCF3, -NH2, -NHC1-4 alkyl, -N(C1-4 alkyl)2, -CONH2, - CONHC1-4 alkyl, -CON(C1-4 alkyl)2, -NHCOC1-4 alkyl, C1-6 alkyl, C1-6 alkoxy and C3-6 cycloalkyl; p is 0, 1, 2, or 3; and D1is a drug moiety. In some embodiments, the conjugate of formula (VI) has the formula (VIa): or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (VI) has the formula (VIb):Attorney Docket No. 330272000240 or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (VI) has the formula (VIc): or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (VI) has the formula (VId):

[0008] Attorney Docket No. 330272000240 or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (VI) has the formula (VIe): or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (VI) has the formula (VIf):Attorney Docket No. 330272000240 or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (VI’) has the formula (VIg): or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (VI’) has the formula (VIh):

[0009] Attorney Docket No. 330272000240 or a pharmaceutically acceptable salt thereof. In some embodiments of the conjugate of formula (VI) or (VI’), or any variationthereof, such as formula (VIa)-(VIh), R2is H or C1-2 alkyl. In some embodiments, R2is H or - CH3. In some embodiments, R2is H. In some embodiments of the conjugate of formula (VI) or (VI’), or any variationthereof, such as formula (VIa)-(VIh), R3is H or C1-2 alkyl. In some embodiments, R3is H or - CH3. In some embodiments, R3is H. In some embodiments of the conjugate of formula (VI) or (VI’), or any variationthereof, such as formula (VIa)-(VIh), R4is H or C1-2 alkyl. In some embodiments, R4is H or - CH3. In some embodiments, R4is -CH3. In some embodiments of the conjugate of formula (VI) or (VI’), or any variationthereof, such as formula (VIa)-(VIh), R5is H or C1-2 alkyl. In some embodiments, R5is H or - CH3. In some embodiments, R5is -CH3. In some embodiments of the conjugate of formula (VI) or (VI’), or any variationthereof, such as formula (VIa)-(VIh), n is 2 or 3. In some embodiments, n is 3. In some embodiments of the conjugate of formula (VI) or (VI’), or any variationthereof, such as formula (VIa)-(VIg), m is 0, 1, or 2. In some embodiments, m is 0 or 1. In some embodiments, m is 0. In some embodiments, m is 1. In some embodiments of the conjugate of formula (VI) or (VI’), or any variationthereof, such as formula (VIa)-(VIg), p is 0, 1, or 2. In some embodiments, p is 0 or 1. In some embodiments, p is 0. In some embodiments, p is 1.Attorney Docket No. 330272000240In some embodiments of a conjugate of formula (VI) or (VI’), or any variationthereof, such as formula (VIa)-(VIh), LAis C4-20alkylene, wherein the C4-20alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, -NRx-, and -S-, wherein L1ais halo, C1-6alkyl, or C1-6alkyl substituted by halo, and wherein Rxis H or C1-6alkyl optionally substituted by halo. In some embodiments, LAis C10-20alkylene, wherein the C10-20alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, -NH-, -N(CH3)-, and -S-. In some embodiments, LAis C10-15alkylene, wherein the C10-15alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, -NH-, and -N(CH3)-. In some embodiments, LAis C5-10alkylene, wherein the C5-10alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, and -NH-. In some embodiments of a conjugate of formula (VI) or (VI’), or any variationthereof, such as formula (VIa)-(VIh), LAcomprises the moiety some embodiments, LAcomprises the moiety . Attorney Docket No.330272000240 the moiety . In some embodiments, LAcomprises the Attorney Docket No. 330272000240 . In some embodiments of a conjugate of formula (VI) or (VI’), or any variationthereof, such as formula (VIa)-(VIh), D1 is a protein. In some embodiments, D1 is a cytokine.In some embodiments, the cytokine is Interleukin-2 (IL-2). In some embodiments, the cytokine is mutated IL-2, such as a cytokine described in US 9,206,943. In some embodiments, the cytokine is Interleukin-15 (IL-15). In some embodiments, the cytokine is mutated IL-15. In one such embodiment, the IL-15 is IL-15[N27D]. In some embodiments, the cytokine is Interleukin-7 (IL-7). In some embodiments, the cytokine is Interleukin-9 (IL- 9). In some embodiments, the cytokine is Interleukin-10 (IL-10). In some embodiments, the cytokine is Interleukin-21 (IL-21). In some embodiments, the cytokine is Interleukin-10 (IL- 10). In some embodiments of a conjugate of formula (VI) or (VI’), or any variationthereof, such as formula (VIa)-(VIh), D1is an anti-cancer agent. In some such embodiments,D1 is SN-38. In some such embodiments, D1 is monomethyl auristatin E. In some suchembodiments, D1 is capecitabine. In some such embodiments, D1 is irinotecan. In some suchembodiments, D1 is trifluridine. In some such embodiments, D1 is doxorubicin. In somesuch embodiments, D1 is docetaxel. In some such embodiments, D1 is infigratinib.In some embodiments of a conjugate of formula (VI) or (VI’), or any variationthereof, such as formula (VIa)-(VIh), D1 is a peptide.In some embodiments, the peptide is RGK-MCA. In some embodiments, the peptide is Neurotensin. In some embodiments, the peptide is Gonadotropin-releasing hormoneAttorney Docket No. 330272000240(GnRH). In some embodiments, the peptide is GIP (1-42), human peptide. In someembodiments, the peptide is D6-GnRH. In some embodiments, the peptide is insulin. Insome embodiments, the peptide is teriparatide. In some embodiments, the peptide iscalcitronin salmon. In some embodiments, the peptide is ipamorelin. In some embodiments, the peptide is vasopressin. In some embodiments, the peptide is glucagon. In some embodiments, the peptide is aclerastide. In some embodiments, the peptide is goserelin. In some embodiments, the peptide is leuprolide. In some embodiments, the peptide is teriparatide. In some embodiments, the peptide is lixisenatide. In some embodiments, the peptide is desmopressin. In some embodiments, the peptide is oxytocin. In some embodiments, the peptide is corticotropin. In some embodiments, the peptide is sermorelin. In some embodiments, the peptide is bremelanotide. In some embodiments, the peptide is abaloparatide. In some embodiments, the peptide is deslorelin. In some embodiments, the peptide drug is a glucagon-like-peptide-1 (GLP-1) receptor agonist used to trat obesity and / or diabetes. In some such embodiments the peptidedrug is semaglutide, liraglutide, dulaglutide, albiglutide, or exenatide. Owing to the dramaticextension of duration of action of peptide drugs when incorporated into the conjugates of the disclosure, the GLP-1 agonist conjugates can be administered on a reduced dosing schedule, such as once weekly, once biweekly, once every three weeks, or once monthly. In some embodiments, the peptide drug is a glucagon-like-peptide-1 (GLP-1) and GIP (glucose-dependent insulinotropic polypeptide receptor agonist used to trat obesity and / or diabetes. In some such embodiments, the peptide drug is tirzepatide. Owing to the dramatic extension of duration of action of peptide drugs when incorporated into the conjugates of the disclosure, the GLP-1 / GIP agonist conjugates can be administered on a reduced dosing schedule, such as once weekly, once biweekly, once every three weeks, or once monthly. In some embodiments, the peptide is an endogenous opioid peptide. In some such embodiments, the peptide is endomorphin-1 or endomorphin-2. In other embodiments, the peptide is dermorphin. In some embodiments of a conjugate of formula (VI) or (VI’), or any variationthereof, such as formula (VIa)-(VIh), D1 is a drug moiety. In some embodiments, the opioidantagonist is naloxone, nalmefene, naltrexone, methylnaltrexone, nalbuphrine, or nalirphine. In some embodiments, provided herein is a conjugate of formula (VII’): Attorney Docket No.330272000240 or a pharmaceutically acceptable salt thereof, wherein: each R1is independently halo or C1-4alkyl; m is 0, 1, 2, or 3; R2is H or C1-4alkyl; X1is -O- or -NRx-; n is 0, 1, 2, or 3; R3is H or C1-4alkyl; R4is H or C1-4alkyl; R5is H or C1-4alkyl; Rxis H or C1-4alkyl; Y1is a bond or C1-4alkylene; Y2is NR6, O or S; LBis a click product formed via a Click reaction between a first Click handle and a second click handle; R6is H or C1-4alkyl; each R7is independently selected from the group consisting of hydrogen, halogen atoms (e.g., Cl, Br or F), hydroxy, -OCF3, -NH2, -NHC1-4alkyl, -N(C1-4alkyl)2, -CONH2, -Attorney Docket No. 330272000240CONHC1-4 alkyl, -CON(C1-4 alkyl)2, -NHCOC1-4 alkyl, C1-6 alkyl, C1-6 alkoxy and C3-6 cycloalkyl; p is 0, 1, 2, or 3; r is 1, 2, 3, 4, 5, 6, or 7; s is 1, 2, 3, 4, 5, 6, or 7; and D1is a drug moiety. In some embodiments, provided herein is a conjugate of formula (VII): or a pharmaceutically acceptable salt thereof, wherein: each R1is independently halo or C1-4alkyl; m is 0, 1, 2, or 3; R2is H or C1-4alkyl;X1 is -O- or -NRx-;n is 0, 1, 2, or 3; R3is H or C1-4alkyl; R4is H or C1-4alkyl; R5is H or C1-4alkyl; Rxis H or C1-4alkyl;Attorney Docket No. 330272000240Y1is a bond or C1-4alkylene; Y2is NR6, O or S; LBis a click product formed via a Click reaction between a first Click handle and a second click handle; R6is H or C1-4alkyl;each R7 is independently selected from the group consisting of hydrogen, halogen atoms(e.g., Cl, Br or F), hydroxy, -OCF3, -NH2, -NHC1-4alkyl, -N(C1-4alkyl)2, -CONH2, - CONHC1-4 alkyl, -CON(C1-4 alkyl)2, -NHCOC1-4 alkyl, C1-6 alkyl, C1-6 alkoxy and C3-6 cycloalkyl; p is 0, 1, 2, or 3; r is 1, 2, 3, 4, 5, 6, or 7; s is 1, 2, 3, 4, 5, 6, or 7; and D1is a drug moiety. In some embodiments, the conjugate of formula (VII) has the formula (VIIa): or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (VII) has the formula (VIIb):Attorney Docket No. 330272000240 or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (VII) has the formula (VIIc): or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (VII’) has the formula (VIId):Attorney Docket No. 330272000240 or a pharmaceutically acceptable salt thereof. In some embodiments of the conjugate of formula (VII) or (VII’), or any variationthereof, such as formula (VIIa)-(VIId), R2is H or C1-2 alkyl. In some embodiments, R2is H or -CH3. In some embodiments, R2is H. In some embodiments of the conjugate of formula (VII) or (VII’), or any variationthereof, such as formula (VIIa)-(VIId), R3is H or C1-2alkyl. In some embodiments, R3is H or -CH3. In some embodiments, R3is H. In some embodiments of the conjugate of formula (VII) or (VII’), or any variationthereof, such as formula (VIIa)-(VIId), R4is H or C1-2alkyl. In some embodiments, R4is H or -CH3. In some embodiments, R4is -CH3. In some embodiments of the conjugate of formula (VII) or (VII’), or any variationthereof, such as formula (VIIa)-(VIId), R5is H or C1-2alkyl. In some embodiments, R5is H or -CH3. In some embodiments, R5is -CH3. In some embodiments of the conjugate of formula (VII) or (VII’), or any variationthereof, such as formula (VIIa)-(VIId), n is 2 or 3. In some embodiments, n is 3. In some embodiments of the conjugate of formula (VII) or (VII’), or any variationthereof, such as formula (VIIa)-(VIId), m is 0, 1, or 2. In some embodiments, m is 0 or 1. In some embodiments, m is 0. In some embodiments, m is 1. In some embodiments of the conjugate of formula (VII) or (VII’), or any variationthereof, such as formula (VIIa)-(VIId), p is 0, 1, or 2. In some embodiments, p is 0 or 1. In some embodiments, p is 0. In some embodiments, p is 1.Attorney Docket No. 330272000240In some embodiments of a conjugate of formula (VII) or (VII’), or any variationthereof, such as formula (VIIa)-(VIId), the click product LBis a triazine moiety. In someembodiments, the conjugate of formula (VII) or (VII’), any of formula (VIIa)-(VIId),comprises one of the following moieties: , wherein X2 is -CH2-, -NRx-, -S- or -O-, wherein Rx is as definedelsewhere herein. In some embodiments, the conjugate comprises the moiety . In some embodiments, the conjugate comprises the moiety . In some embodiments of a conjugate of formula (VII) or (VII’), or any variationthereof, such as formula (VIIa)-(VIId), LA-LBcomprises the moiety In some embodiments of a conjugate of formula (VII) or (VII’), In some embodimentsof a conjugate of formula (VII), or any variation thereof, such as formula (VIIa)-(VIId), D1is a protein. In some embodiments, D1is a cytokine. In some embodiments, the cytokine is Interleukin-2 (IL-2). In some embodiments, the cytokine is mutated IL-2, such as a cytokine described in US 9,206,943. In some embodiments, the cytokine is Interleukin-15 (IL-15). In some embodiments, the cytokine is mutated IL-15. In one such embodiment, the IL-15 is IL- 15[N27D]. In some embodiments, the cytokine is Interleukin-7 (IL-7). In someAttorney Docket No. 330272000240embodiments, the cytokine is Interleukin-9 (IL-9). In some embodiments, the cytokine is Interleukin-10 (IL-10). In some embodiments, the cytokine is Interleukin-21 (IL-21). In some embodiments, the cytokine is Interleukin-10 (IL-10). In some embodiments of a conjugate of formula (VII) or (VII’), or any variationthereof, such as formula (VIIa)-(VIId), D1is an anti-cancer agent. In some suchembodiments, D1 is SN-38. In some such embodiments, D1 is monomethyl auristatin E. Insome such embodiments, D1 is capecitabine. In some such embodiments, D1 is irinotecan. Insome such embodiments, D1 is trifluridine. In some such embodiments, D1 is doxorubicin.In some such embodiments, D1 is docetaxel. In some such embodiments, D1 is infigratinib.In some embodiments of a conjugate of formula (VII) or (VII’), or any variationthereof, such as formula (VIIa)-(VIId), D1 is a peptide.In some embodiments, the peptide is RGK-MCA. In some embodiments, the peptide is Neurotensin. In some embodiments, the peptide is Gonadotropin-releasing hormone (GnRH). In some embodiments, the peptide is GIP (1-42), human peptide. In someembodiments, the peptide is D6-GnRH. In some embodiments, the peptide is insulin. Insome embodiments, the peptide is teriparatide. In some embodiments, the peptide iscalcitronin salmon. In some embodiments, the peptide is ipamorelin. In some embodiments, the peptide is vasopressin. In some embodiments, the peptide is glucagon. In some embodiments, the peptide is aclerastide. In some embodiments, the peptide is goserelin. In some embodiments, the peptide is leuprolide. In some embodiments, the peptide is teriparatide. In some embodiments, the peptide is lixisenatide. In some embodiments, the peptide is desmopressin. In some embodiments, the peptide is oxytocin. In some embodiments, the peptide is corticotropin. In some embodiments, the peptide is sermorelin. In some embodiments, the peptide is bremelanotide. In some embodiments, the peptide is abaloparatide. In some embodiments, the peptide is deslorelin. In some embodiments, the peptide drug is a glucagon-like-peptide-1 (GLP-1) receptor agonist used to trat obesity and / or diabetes. In some such embodiments the peptidedrug is semaglutide, liraglutide, dulaglutide, albiglutide, or exenatide. Owing to the dramaticextension of duration of action of peptide drugs when incorporated into the conjugates of the disclosure, the GLP-1 agonist conjugates can be administered on a reduced dosing schedule, such as once weekly, once biweekly, once every three weeks, or once monthly.Attorney Docket No. 330272000240In some embodiments, the peptide drug is a glucagon-like-peptide-1 (GLP-1) and GIP (glucose-dependent insulinotropic polypeptide receptor agonist used to trat obesity and / or diabetes. In some such embodiments, the peptide drug is tirzepatide. Owing to the dramatic extension of duration of action of peptide drugs when incorporated into the conjugates of the disclosure, the GLP-1 / GIP agonist conjugates can be administered on a reduced dosing schedule, such as once weekly, once biweekly, once every three weeks, or once monthly. In some embodiments, the peptide is an endogenous opioid peptide. In some such embodiments, the peptide is endomorphin-1 or endomorphin-2. In other embodiments, the peptide is dermorphin. In some embodiments of a conjugate of formula (VII) or (VII’), or any variationthereof, such as formula (VIIa)-(VIId), D1 is an opioid antagonist. In some embodiments, theopioid antagonist is naloxone, nalmefene, naltrexone, methylnaltrexone, nalbuphine, or nalorphine. In some embodiments of a conjugate of formula (VII) or (VII’), or any variationthereof, such as formula (VIIa)-(VIId), D1 is an opioid agonist. In some embodiments, theopioid agonist is morphine, oxycodone, hydromorphone, or methadone. In some embodiments, provided herein is a conjugate of formula (VIII’): or a pharmaceutically acceptable salt thereof, wherein: each R1is independently halo or C1-4alkyl;Attorney Docket No. 330272000240m is 0, 1, 2, or 3; R2is H or C1-4alkyl;X1 is -O- or -NRx-;n is 0, 1, 2, or 3; R3is H or C1-4alkyl; R4is H or C1-4alkyl; R5is H or C1-4alkyl; Rxis H or C1-4alkyl; Y1is a bond or C1-4alkylene; Y2is NR6, O or S; LBis a click product formed via a Click reaction between a first Click handle and a second click handle; R6is H or C1-4alkyl;each R7 is independently selected from the group consisting of hydrogen, halogen atoms(e.g., Cl, Br or F), hydroxy, -OCF3, -NH2, -NHC1-4 alkyl, -N(C1-4 alkyl)2, -CONH2, - CONHC1-4alkyl, -CON(C1-4alkyl)2, -NHCOC1-4alkyl, C1-6alkyl, C1-6alkoxy and C3-6cycloalkyl; p is 0, 1, 2, or 3; r is 1, 2, 3, 4, 5, 6, or 7; s is 1, 2, 3, 4, 5, 6, or 7; t is 1, 2, 3, or 4; u is 1, 2, 3, or 4; and D1is a drug moiety. In some embodiments, provided herein is a conjugate of formula (VIII): Attorney Docket No.330272000240 or a pharmaceutically acceptable salt thereof, wherein: each R1is independently halo or C1-4alkyl; m is 0, 1, 2, or 3; R2is H or C1-4alkyl; X1is -O- or -NRx-; n is 0, 1, 2, or 3; R3is H or C1-4alkyl; R4is H or C1-4alkyl; R5is H or C1-4alkyl; Rxis H or C1-4alkyl; Y1is a bond or C1-4alkylene; Y2is NR6, O or S; LBis a click product formed via a Click reaction between a first Click handle and a second click handle; R6is H or C1-4alkyl; each R7is independently selected from the group consisting of hydrogen, halogen atoms (e.g., Cl, Br or F), hydroxy, -OCF3, -NH2, -NHC1-4alkyl, -N(C1-4alkyl)2, -CONH2, - CONHC1-4alkyl, -CON(C1-4alkyl)2, -NHCOC1-4alkyl, C1-6alkyl, C1-6alkoxy and C3-6cycloalkyl; p is 0, 1, 2, or 3;Attorney Docket No. 330272000240r is 1, 2, 3, 4, 5, 6, or 7; s is 1, 2, 3, 4, 5, 6, or 7; t is 1, 2, 3, or 4; u is 1, 2, 3, or 4; and D1is a drug moiety. In some embodiments, the conjugate of formula (VIII) has the formula (VIIIa): (VIIIa) or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (VIII) has the formula (VIIIb): (VIIIb)Attorney Docket No. 330272000240or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (VIII) has the formula (VIIIc): or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (VIII) has the formula (VIIId): (VIIId) or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (VIII) has the formula (VIIIe):Attorney Docket No. 330272000240 or a pharmaceutically acceptable salt thereof. In some embodiments, the conjugate of formula (VIII’) has the formula (VIIIf): (VIIIf) or a pharmaceutically acceptable salt thereof. In some embodiments of the conjugate of formula (VIII) or (VIII’), or any variationthereof, such as formula (VIIIa)-(VIIIf), R2is H or C1-2 alkyl. In some embodiments, R2is H or -CH3. In some embodiments, R2is H. In some embodiments of the conjugate of formula (VIII) or (VIII’), or any variationthereof, such as formula (VIIIa)-(VIIIf), R3is H or C1-2 alkyl. In some embodiments, R3is H or -CH3. In some embodiments, R3is H.Attorney Docket No. 330272000240In some embodiments of the conjugate of formula (VIII) or (VIII’), or any variationthereof, such as formula (VIIIa)-(VIIIf), R4is H or C1-2alkyl. In some embodiments, R4is H or -CH3. In some embodiments, R4is -CH3. In some embodiments of the conjugate of formula (VIII) or (VIII’), or any variationthereof, such as formula (VIIIa)-(VIIIf), R5is H or C1-2alkyl. In some embodiments, R5is H or -CH3. In some embodiments, R5is -CH3. In some embodiments of the conjugate of formula (VIII) or (VIII’), or any variationthereof, such as formula (VIIIa)-(VIIIf), n is 2 or 3. In some embodiments, n is 3. In some embodiments of the conjugate of formula (VIII) or (VIII’), or any variationthereof, such as formula (VIIIa)-(VIIIf), m is 0, 1, or 2. In some embodiments, m is 0 or 1. In some embodiments, m is 0. In some embodiments, m is 1. In some embodiments of the conjugate of formula (VIII) or (VIII’), or any variationthereof, such as formula (VIIIa), or (VIIIc)-(VIIIf), p is 0, 1, or 2. In some embodiments, p is 0 or 1. In some embodiments, p is 0. In some embodiments, p is 1. In some embodiments of a conjugate of formula (VIII) or (VIII’), or any variationthereof, such as formula (VIIIa)-(VIIIb), the click product LBis a triazine moiety. In some embodiments, the conjugate of formula (VIII), any of formula (VIIIa)-(VIIIb), comprises one of the following moieties: , wherein X2 is -CH2-, -NRx-, -S- or -O-, wherein Rx is as definedelsewhere herein. In some embodiments, the conjugate comprises the moiety . In some embodiments, the conjugate comprises the moiety . In some embodiments of a conjugate of formula (VIII) or (VIII’), or any variationthereof, such as formula (VIIIa)-(VIIIb), LA-LBcomprises the moietyAttorney Docket No. 330272000240 C1-4alky1, R10is H or C1-4alky1, and Q is -CH2-, -O-, -S-, -NH-, or -N(C1-4alkyl)-. In some embodiments of a conjugate of formula (VIII) or (VIII’), or any variationthereof, such as formula (VIIIa)-(VIIIf), D1 is a protein. In some embodiments, D1 is acytokine. In some embodiments, the cytokine is Interleukin-2 (IL-2). In some embodiments, the cytokine is mutated IL-2, such as a cytokine described in US 9,206,943. In some embodiments, the cytokine is Interleukin-15 (IL-15). In some embodiments, the cytokine is mutated IL-15. In one such embodiment, the IL-15 is IL-15[N27D]. In some embodiments, the cytokine is Interleukin-7 (IL-7). In some embodiments, the cytokine is Interleukin-9 (IL-9). In some embodiments, the cytokine is Interleukin-10 (IL-10). In some embodiments, thecytokine is Interleukin-21 (IL-21). In some embodiments, the cytokine is Interleukin-10 (IL- 10). In some embodiments of a conjugate of formula (VIII) or (VIII’), or any variationthereof, such as formula (VIIIa)-(VIIIf), D1is an anti-cancer agent. In some suchembodiments, D1 is SN-38. In some such embodiments, D1 is monomethyl auristatin E. Insome such embodiments, D1 is capecitabine. In some such embodiments, D1 is irinotecan. Insome such embodiments, D1 is trifluridine. In some such embodiments, D1 is doxorubicin.In some such embodiments, D1 is docetaxel. In some such embodiments, D1 is infigratinib.In some embodiments of a conjugate of formula (VIII) or (VIII’), or any variationthereof, such as formula (VIIIa)-(VIIIf), D1 is a peptide.In some embodiments, the peptide is RGK-MCA. In some embodiments, the peptide is Neurotensin. In some embodiments, the peptide is Gonadotropin-releasing hormone (GnRH). In some embodiments, the peptide is GIP (1-42), human peptide. In someAttorney Docket No. 330272000240embodiments, the peptide is D6-GnRH. In some embodiments, the peptide is insulin. Insome embodiments, the peptide is teriparatide. In some embodiments, the peptide iscalcitronin salmon. In some embodiments, the peptide is ipamorelin. In some embodiments, the peptide is vasopressin. In some embodiments, the peptide is glucagon. In some embodiments, the peptide is aclerastide. In some embodiments, the peptide is goserelin. In some embodiments, the peptide is leuprolide. In some embodiments, the peptide is teriparatide. In some embodiments, the peptide is lixisenatide. In some embodiments, the peptide is desmopressin. In some embodiments, the peptide is oxytocin. In someembodiments, the peptide is corticotropin. In some embodiments, the peptide is sermorelin.In some embodiments, the peptide is bremelanotide. In some embodiments, the peptide is abaloparatide. In some embodiments, the peptide is deslorelin. In some embodiments, the peptide drug is a glucagon-like-peptide-1 (GLP-1) receptor agonist used to trat obesity and / or diabetes. In some such embodiments the peptidedrug is semaglutide, liraglutide, dulaglutide, albiglutide, or exenatide. Owing to the dramaticextension of duration of action of peptide drugs when incorporated into the conjugates of the disclosure, the GLP-1 agonist conjugates can be administered on a reduced dosing schedule, such as once weekly, once biweekly, once every three weeks, or once monthly. In some embodiments, the peptide drug is a glucagon-like-peptide-1 (GLP-1) and GIP (glucose-dependent insulinotropic polypeptide receptor agonist used to trat obesity and / or diabetes. In some such embodiments, the peptide drug is tirzepatide. Owing to the dramatic extension of duration of action of peptide drugs when incorporated into the conjugates of the disclosure, the GLP-1 / GIP agonist conjugates can be administered on a reduced dosing schedule, such as once weekly, once biweekly, once every three weeks, or once monthly. In some embodiments, the peptide is an endogenous opioid peptide. In some such embodiments, the peptide is endomorphin-1 or endomorphin-2. In other embodiments, the peptide is dermorphin. In some embodiments of a conjugate of formula (VIII) or (VIII’), or any variationthereof, such as formula (VIIIa)-(VIIIf), D1 is an opioid antagonist. In some embodiments,the opioid antagonist is naloxone, nalmefene, naltrexone, methylnaltrexone, nalbuphine, or nalorphine.Attorney Docket No. 330272000240In some embodiments of a conjugate of formula (VIII) or (VIII’), or any variationthereof, such as formula (VIIIa)-(VIIIf), D1 is an opioid agonist. In some embodiments, theopioid agonist is morphine, oxycodone, hydromorphone, or methadone. In some embodiments, provided herein is a conjugate of formula (IX): or a pharmaceutically acceptable salt thereof, wherein: each R1is independently halo or C1-4alkyl; m is 0, 1, 2, or 3; R2is H or C1-4alkyl;X1 is -O- or -NRx-;n is 0, 1, 2, or 3; R3is H or C1-4alkyl; R4is H or C1-4alkyl; R5is H or C1-4alkyl; Rxis H or C1-4alkyl; L is a linker;Z1 is C1-6alkyl, C6-10aryl, or 5- to 10-membered heteroaryl, whereinthe C1-6alkyl is optionally substituted with one or more Z1a, and the C6-10aryl or 5- to 10-membered heteroaryl is optionally substituted with one ormore Z1b;Attorney Docket No. 330272000240each Z1aor Z1bis independently halo, C1-6alkoxy, or C1-6alkyl optionally substituted by halo; and D1is a drug moiety. In some embodiments of the conjugate of formula (IX), R2is H or C1-2 alkyl. In some embodiments, R2is H or -CH3. In some embodiments, R2is H. In some embodiments of the conjugate of formula (IX), R3is H or C1-2alkyl. In some embodiments, R3is H or -CH3. In some embodiments, R3is H. In some embodiments of the conjugate of formula (IX), R4is H or C1-2 alkyl. In some embodiments, R4is H or -CH3. In some embodiments, R4is -CH3. In some embodiments of the conjugate of formula (IX), R5is H or C1-2alkyl. In some embodiments, R5is H or -CH3. In some embodiments, R5is -CH3. In some embodiments of the conjugate of formula (IX), n is 2 or 3. In some embodiments, n is 3. In some embodiments of the conjugate of formula (IX), m is 0, 1, or 2. In some embodiments, m is 0 or 1. In some embodiments, m is 0. In some embodiments, m is 1. In some embodiments of the conjugate of formula (IX), L is C4-20alkylene, wherein the C4-20alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, -NRx-, and -S-, wherein L1ais halo, C1-6alkyl, or C1-6alkyl substituted by halo. In some embodiments, L is C10-20alkylene, wherein the C10-20alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, -NH-, -N(CH3)-, and -S-. In some embodiments, L is C10-15alkylene, wherein the C10-15alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, -NH-, and -N(CH3)-. In some embodiments, L is C5-10alkylene, wherein the C5-10alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, and -NH-. In some embodiments of the conjugate of formula (IX), L comprises the moiety . In some embodiments, L comprises the moiety Attorney Docket No.330272000240 . In some embodiments, L comprises the moiety . In some embodiments, L comprises the moiety . In some embodiments, L comprises the moiety . In some embodiments, L comprises the moiety Attorney Docket No. 330272000240 embodiments, L comprises the moiety embodiments, L comprises the moiety embodiments, L comprises the moiety embodiments, L comprises the moiety .In some embodiments of a conjugate of formula (IX), or any variation thereof, D1is a protein. In some embodiments, D1is a cytokine. In some embodiments, the cytokine is Interleukin-2 (IL-2). In some embodiments, the cytokine is mutated IL-2, such as a cytokine described in US 9,206,943. In some embodiments, the cytokine is Interleukin-15 (IL-15). In some embodiments, the cytokine is mutated IL-15. In one such embodiment, the IL-15 is IL- 15[N27D]. In some embodiments, the cytokine is Interleukin-7 (IL-7). In some embodiments, the cytokine is Interleukin-9 (IL-9). In some embodiments, the cytokine is Interleukin-10 (IL-10). In some embodiments, the cytokine is Interleukin-21 (IL-21). In some embodiments, the cytokine is Interleukin-10 (IL-10). In some embodiments of a conjugate of formula (IX), or any variation thereof, D1is an anti-cancer agent. In some such embodiments, D1is SN-38. In some such embodiments,D1 is monomethyl auristatin E. In some such embodiments, D1 is capecitabine. In some suchembodiments, D1 is irinotecan. In some such embodiments, D1 is trifluridine. In some suchAttorney Docket No. 330272000240embodiments, D1 is doxorubicin. In some such embodiments, D1 is docetaxel. In some suchembodiments, D1 is infigratinib.In some embodiments of a conjugate of formula (IX), or any variation thereof, D1 is apeptide. In some embodiments, the peptide is RGK-MCA. In some embodiments, the peptide is Neurotensin. In some embodiments, the peptide is Gonadotropin-releasing hormone (GnRH). In some embodiments, the peptide is GIP (1-42), human peptide. In someembodiments, the peptide is D6-GnRH. In some embodiments, the peptide is insulin. Insome embodiments, the peptide is teriparatide. In some embodiments, the peptide iscalcitronin salmon. In some embodiments, the peptide is ipamorelin. In some embodiments, the peptide is vasopressin. In some embodiments, the peptide is glucagon. In some embodiments, the peptide is aclerastide. In some embodiments, the peptide is goserelin. In some embodiments, the peptide is leuprolide. In some embodiments, the peptide is teriparatide. In some embodiments, the peptide is lixisenatide. In some embodiments, the peptide is desmopressin. In some embodiments, the peptide is oxytocin. In some embodiments, the peptide is corticotropin. In some embodiments, the peptide is sermorelin. In some embodiments, the peptide is bremelanotide. In some embodiments, the peptide is abaloparatide. In some embodiments, the peptide is deslorelin. In some embodiments, the peptide drug is a glucagon-like-peptide-1 (GLP-1) receptor agonist used to trat obesity and / or diabetes. In some such embodiments the peptidedrug is semaglutide, liraglutide, dulaglutide, albiglutide, or exenatide. Owing to the dramaticextension of duration of action of peptide drugs when incorporated into the conjugates of the disclosure, the GLP-1 agonist conjugates can be administered on a reduced dosing schedule, such as once weekly, once biweekly, once every three weeks, or once monthly. In some embodiments, the peptide drug is a glucagon-like-peptide-1 (GLP-1) and GIP (glucose-dependent insulinotropic polypeptide receptor agonist used to trat obesity and / or diabetes. In some such embodiments, the peptide drug is tirzepatide. Owing to the dramatic extension of duration of action of peptide drugs when incorporated into the conjugates of the disclosure, the GLP-1 / GIP agonist conjugates can be administered on a reduced dosing schedule, such as once weekly, once biweekly, once every three weeks, or once monthly.Attorney Docket No. 330272000240In some embodiments, the peptide is an endogenous opioid peptide. In some such embodiments, the peptide is endomorphin-1 or endomorphin-2. In other embodiments, the peptide is dermorphin. In some embodiments of a conjugate of formula (IX), or any variation thereof, D1 isan opioid antagonist. In some embodiments, the opioid antagonist is naloxone, nalmefene, naltrexone, methylnaltrexone, nalbuphine, or nalorphine. In some embodiments of a conjugate of formula (IX), or any variation thereof, D1 isan opioid agonist. In some embodiments, the opioid agonist is morphine, oxycodone,hydromorphone, or methadone. In some embodiments, provided herein is a conjugate of formula (X): or a pharmaceutically acceptable salt thereof, wherein: each R1is independently halo or C1-4alkyl; m is 0, 1, 2, or 3; R2is H or C1-4alkyl;X1 is -O- or -NRx-;n is 0, 1, 2, or 3; R3is H or C1-4alkyl; R4is H or C1-4alkyl;Attorney Docket No. 330272000240R5is H or C1-4alkyl; Rxis H or C1-4alkyl; LAis C3-20alkylene, wherein the C3-20alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, - NRy-, and -S-; each L1ais halo, C1-6alkyl, or C1-6alkyl substituted by halo; each Ryis H or C1-4alkyl; LBis a click product formed via a Click reaction between a first Click handle and a second click handle;Z1 is C1-6alkyl, C6-10aryl, or 5- to 10-membered heteroaryl, whereinthe C1-6alkyl is optionally substituted with one or more Z1a, and the C6-10aryl or 5- to 10-membered heteroaryl is optionally substituted with one ormore Z1b; each Z1aor Z1bis independently halo, C1-6alkoxy, or C1-6alkyl optionally substituted by halo; and D1is a drug moiety. In some embodiments of the conjugate of formula (X), R2is H or C1-2alkyl. In some embodiments, R2is H or -CH3. In some embodiments, R2is H. In some embodiments of the conjugate of formula (X), R3is H or C1-2 alkyl. In some embodiments, R3is H or -CH3. In some embodiments, R3is H. In some embodiments of the conjugate of formula (X), R4is H or C1-2 alkyl. In some embodiments, R4is H or -CH3. In some embodiments, R4is -CH3. In some embodiments of the conjugate of formula (X), R5is H or C1-2alkyl. In some embodiments, R5is H or -CH3. In some embodiments, R5is -CH3. In some embodiments of the conjugate of formula (X), n is 2 or 3. In some embodiments, n is 3. In some embodiments of the conjugate of formula (X), m is 0, 1, or 2. In some embodiments, m is 0 or 1. In some embodiments, m is 0. In some embodiments, m is 1.Attorney Docket No. 330272000240In some embodiments of a conjugate of formula (X), LAis C4-20alkylene, wherein the C4-20alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, -NRx-, and -S-, wherein L1ais halo, C1-6alkyl, or C1-6alkyl substituted by halo, and wherein Rxis H or C1-6alkyl optionally substituted by halo. In some embodiments, LAis C10-20alkylene, wherein the C10-20alkylene is optionallysubstituted with one or more L1a, and one or more alkylene units is optionally replaced with agroup selected from -O-, -NH-, -N(CH3)-, and -S-. In some embodiments, LAis C10- 15alkylene, wherein the C10-15alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, -NH-, and - N(CH3)-. In some embodiments, LAis C5-10alkylene, wherein the C5-10alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, and -NH-. In some embodiments of a conjugate of formula (X), LAcomprises the moiety . In some embodiments, LAcomprises the moiety comprises the moiety comprises the moiety Attorney Docket No.330272000240 embodiments, LAcomprises the moiety In some embodiments, LAcomprises the moiety . In some embodiments, LAcomprises the moiety embodiments, LAcomprises the moiety embodiments, LAcomprises the Attorney Docket No. 330272000240 In some embodiments of a conjugate of formula (X), the click product LBis a triazine moiety. In some embodiments, the conjugate of formula (X), comprises one of the following moieties: , wherein X2 is -CH2-, -NRx-, -S- or -O-, wherein Rx is as definedelsewhere herein. In some embodiments, the conjugate comprises the moiety . In some embodiments, the conjugate comprises the moiety . In some embodiments of a conjugate of formula (X), LA-LBcomprises the moiety Attorney Docket No. 330272000240In some embodiments of a conjugate of formula (X), or any variation thereof, D1is a protein. In some embodiments, D1is a cytokine. In some embodiments, the cytokine is Interleukin-2 (IL-2). In some embodiments, the cytokine is mutated IL-2, such as a cytokine described in US 9,206,943. In some embodiments, the cytokine is Interleukin-15 (IL-15). In some embodiments, the cytokine is mutated IL-15. In one such embodiment, the IL-15 is IL- 15[N27D]. In some embodiments, the cytokine is Interleukin-7 (IL-7). In some embodiments, the cytokine is Interleukin-9 (IL-9). In some embodiments, the cytokine is Interleukin-10 (IL-10). In some embodiments, the cytokine is Interleukin-21 (IL-21). In some embodiments, the cytokine is Interleukin-10 (IL-10). In some embodiments of a conjugate of formula (X), or any variation thereof, D1 is ananti-cancer agent. In some such embodiments, D1is SN-38. In some such embodiments, D1is monomethyl auristatin E. In some such embodiments, D1 is capecitabine. In some suchembodiments, D1 is irinotecan. In some such embodiments, D1 is trifluridine. In some suchembodiments, D1 is doxorubicin. In some such embodiments, D1 is docetaxel. In some suchembodiments, D1 is infigratinib.In some embodiments of a conjugate of formula (X), or any variation thereof, D1 is apeptide. In some embodiments, the peptide is RGK-MCA. In some embodiments, the peptide is Neurotensin. In some embodiments, the peptide is Gonadotropin-releasing hormone (GnRH). In some embodiments, the peptide is GIP (1-42), human peptide. In someembodiments, the peptide is D6-GnRH. In some embodiments, the peptide is insulin. Insome embodiments, the peptide is teriparatide. In some embodiments, the peptide iscalcitronin salmon. In some embodiments, the peptide is ipamorelin. In some embodiments, the peptide is vasopressin. In some embodiments, the peptide is glucagon. In some embodiments, the peptide is aclerastide. In some embodiments, the peptide is goserelin. In some embodiments, the peptide is leuprolide. In some embodiments, the peptide is teriparatide. In some embodiments, the peptide is lixisenatide. In some embodiments, the peptide is desmopressin. In some embodiments, the peptide is oxytocin. In some embodiments, the peptide is corticotropin. In some embodiments, the peptide is sermorelin. In some embodiments, the peptide is bremelanotide. In some embodiments, the peptide is abaloparatide. In some embodiments, the peptide is deslorelin.Attorney Docket No. 330272000240In some embodiments, the peptide drug is a glucagon-like-peptide-1 (GLP-1) receptor agonist used to trat obesity and / or diabetes. In some such embodiments the peptidedrug is semaglutide, liraglutide, dulaglutide, albiglutide, or exenatide. Owing to the dramaticextension of duration of action of peptide drugs when incorporated into the conjugates of the disclosure, the GLP-1 agonist conjugates can be administered on a reduced dosing schedule, such as once weekly, once biweekly, once every three weeks, or once monthly. In some embodiments, the peptide drug is a glucagon-like-peptide-1 (GLP-1) and GIP (glucose-dependent insulinotropic polypeptide receptor agonist used to trat obesity and / or diabetes. In some such embodiments, the peptide drug is tirzepatide. Owing to the dramatic extension of duration of action of peptide drugs when incorporated into the conjugates of the disclosure, the GLP-1 / GIP agonist conjugates can be administered on a reduced dosing schedule, such as once weekly, once biweekly, once every three weeks, or once monthly. In some embodiments, the peptide is an endogenous opioid peptide. In some such embodiments, the peptide is endomorphin-1 or endomorphin-2. In other embodiments, the peptide is dermorphin. In some embodiments of a conjugate of formula (X), or any variation thereof, D1 is anopioid antagonist. In some embodiments, the opioid antagonist is naloxone, nalmefene, naltrexone, methylnaltrexone, nalbuphine, or nalorphine. In some embodiments of a conjugate of formula (X), or any variation thereof, D1 is anopioid agonist. In some embodiments, the opioid agonist is morphine, oxycodone,hydromorphone, or methadone. In some embodiments, provided herein is a conjugate of formula (XI):

[0010] Attorney Docket No.330272000240 or a pharmaceutically acceptable salt thereof, wherein: each R1is independently halo or C1-4alkyl; m is 0, 1, 2, or 3; R2is H or C1-4alkyl; X1is -O- or -NRx-; n is 0, 1, 2, or 3; R3is H or C1-4alkyl; R4is H or C1-4alkyl; R5is H or C1-4alkyl; Rxis H or C1-4alkyl; LAis C3-20alkylene, wherein the C3-20alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, - NRy-, and -S-; each L1ais halo, C1-6alkyl, or C1-6alkyl substituted by halo; each Ryis H or C1-4alkyl; Z1is C1-6alkyl, C6-10aryl, or 5- to 10-membered heteroaryl, wherein the C1-6alkyl is optionally substituted with one or more Z1a, andAttorney Docket No. 330272000240the C6-10aryl or 5- to 10-membered heteroaryl is optionally substituted with one ormore Z1b; each Z1aor Z1bis independently halo, C1-6alkoxy, or C1-6alkyl optionally substituted by halo; and D1is a drug moiety. In some embodiments of the conjugate of formula (XI), R2is H or C1-2alkyl. In some embodiments, R2is H or -CH3. In some embodiments, R2is H. In some embodiments of the conjugate of formula (XI), R3is H or C1-2 alkyl. In some embodiments, R3is H or -CH3. In some embodiments, R3is H. In some embodiments of the conjugate of formula (XI), R4is H or C1-2alkyl. In some embodiments, R4is H or -CH3. In some embodiments, R4is -CH3. In some embodiments of the conjugate of formula (XI), R5is H or C1-2 alkyl. In some embodiments, R5is H or -CH3. In some embodiments, R5is -CH3. In some embodiments of the conjugate of formula (XI), n is 2 or 3. In some embodiments, n is 3. In some embodiments of the conjugate of formula (XI), m is 0, 1, or 2. In some embodiments, m is 0 or 1. In some embodiments, m is 0. In some embodiments, m is 1. In some embodiments of a conjugate of formula (XI), LAis C4-20alkylene, wherein the C4-20alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, -NRx-, and -S-, wherein L1ais halo, C1-6alkyl, or C1-6alkyl substituted by halo, and wherein Rxis H or C1-6alkyl optionally substituted by halo. In some embodiments, LAis C10-20alkylene, wherein the C10-20alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, -NH-, -N(CH3)-, and -S-. In some embodiments, LAis C10- 15alkylene, wherein the C10-15alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, -NH-, and - N(CH3)-. In some embodiments, LAis C5-10alkylene, wherein the C5-10alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, and -NH-.Attorney Docket No. 330272000240In some embodiments of a conjugate of formula (XI), LAcomprises the moiety embodiments, LAcomprises the Attorney Docket No. 330272000240In some embodiments, LA comprises the moiety . In someembodiments, LA comprises the moiety . In someembodiments, LA comprises the moiety . In someembodiments, LA comprises the moiety . In someembodiments, LA comprises the moiety . In someembodiments, LA comprises the moiety .In some embodiments of a conjugate of formula (XI), or any variation thereof, D1is a protein. In some embodiments, D1is a cytokine. In some embodiments, the cytokine is Interleukin-2 (IL-2). In some embodiments, the cytokine is mutated IL-2, such as a cytokine described in US 9,206,943. In some embodiments, the cytokine is Interleukin-15 (IL-15). In some embodiments, the cytokine is mutated IL-15. In one such embodiment, the IL-15 is IL- 15[N27D]. In some embodiments, the cytokine is Interleukin-7 (IL-7). In some embodiments, the cytokine is Interleukin-9 (IL-9). In some embodiments, the cytokine isAttorney Docket No. 330272000240Interleukin-10 (IL-10). In some embodiments, the cytokine is Interleukin-21 (IL-21). In some embodiments, the cytokine is Interleukin-10 (IL-10). In some embodiments of a conjugate of formula (XI), or any variation thereof, D1 isan anti-cancer agent. In some such embodiments, D1is SN-38. In some such embodiments,D1 is monomethyl auristatin E. In some such embodiments, D1 is capecitabine. In some suchembodiments, D1 is irinotecan. In some such embodiments, D1 is trifluridine. In some suchembodiments, D1 is doxorubicin. In some such embodiments, D1 is docetaxel. In some suchembodiments, D1 is infigratinib.In some embodiments of a conjugate of formula (XI), or any variation thereof, D1 is apeptide. In some embodiments, the peptide is RGK-MCA. In some embodiments, the peptide is Neurotensin. In some embodiments, the peptide is Gonadotropin-releasing hormone (GnRH). In some embodiments, the peptide is GIP (1-42), human peptide. In someembodiments, the peptide is D6-GnRH. In some embodiments, the peptide is insulin. Insome embodiments, the peptide is teriparatide. In some embodiments, the peptide iscalcitronin salmon. In some embodiments, the peptide is ipamorelin. In some embodiments, the peptide is vasopressin. In some embodiments, the peptide is glucagon. In some embodiments, the peptide is aclerastide. In some embodiments, the peptide is goserelin. In some embodiments, the peptide is leuprolide. In some embodiments, the peptide is teriparatide. In some embodiments, the peptide is lixisenatide. In some embodiments, the peptide is desmopressin. In some embodiments, the peptide is oxytocin. In some embodiments, the peptide is corticotropin. In some embodiments, the peptide is sermorelin. In some embodiments, the peptide is bremelanotide. In some embodiments, the peptide is abaloparatide. In some embodiments, the peptide is deslorelin. In some embodiments, the peptide drug is a glucagon-like-peptide-1 (GLP-1) receptor agonist used to trat obesity and / or diabetes. In some such embodiments the peptidedrug is semaglutide, liraglutide, dulaglutide, albiglutide, or exenatide. Owing to the dramaticextension of duration of action of peptide drugs when incorporated into the conjugates of the disclosure, the GLP-1 agonist conjugates can be administered on a reduced dosing schedule, such as once weekly, once biweekly, once every three weeks, or once monthly. In some embodiments, the peptide drug is a glucagon-like-peptide-1 (GLP-1) and GIP (glucose-dependent insulinotropic polypeptide receptor agonist used to trat obesity and / orAttorney Docket No. 330272000240diabetes. In some such embodiments, the peptide drug is tirzepatide. Owing to the dramatic extension of duration of action of peptide drugs when incorporated into the conjugates of thedisclosure, the GLP-1 / GIP agonist conjugates can be administered on a reduced dosingschedule, such as once weekly, once biweekly, once every three weeks, or once monthly. In some embodiments, the peptide is an endogenous opioid peptide. In some such embodiments, the peptide is endomorphin-1 or endomorphin-2. In other embodiments, the peptide is dermorphin. In some embodiments of a conjugate of formula (XI), or any variation thereof, D1 isan opioid antagonist. In some embodiments, the opioid antagonist is naloxone, nalmefene, naltrexone, methylnaltrexone, nalbuphine, or nalorphine. In some embodiments of a conjugate of formula (XI), or any variation thereof, D1 isan opioid agonist. In some embodiments, the opioid agonist is morphine, oxycodone,hydromorphone, or methadone. In some embodiments, provided herein is a conjugate with a structure as shown: wherein D1is a drug moiety. In some embodiments of a conjugate of formula (XII), D1 is a protein. In someembodiments, D1is a cytokine. In some embodiments, the cytokine is Interleukin-2 (IL-2). In some embodiments, the cytokine is mutated IL-2, such as a cytokine described in US 9,206,943. In some embodiments, the cytokine is Interleukin-15 (IL-15). In some embodiments, the cytokine is mutated IL-15. In one such embodiment, the IL-15 is IL- 15[N27D]. In some embodiments, the cytokine is Interleukin-7 (IL-7). In some embodiments, the cytokine is Interleukin-9 (IL-9). In some embodiments, the cytokine isAttorney Docket No. 330272000240Interleukin-10 (IL-10). In some embodiments, the cytokine is Interleukin-21 (IL-21). In some embodiments, the cytokine is Interleukin-10 (IL-10). In some embodiments of a conjugate of formula (XII), D1 is an anti-cancer agent. Insome such embodiments, D1 is SN-38. In some such embodiments, D1 is monomethylauristatin E. In some such embodiments, D1 is capecitabine. In some such embodiments, D1is irinotecan. In some such embodiments, D1 is trifluridine. In some such embodiments, D1is doxorubicin. In some such embodiments, D1 is docetaxel. In some such embodiments, D1is infigratinib.In some embodiments of a conjugate of formula (XII), D1 is a peptide.In some embodiments, the peptide is RGK-MCA. In some embodiments, the peptide is Neurotensin. In some embodiments, the peptide is Gonadotropin-releasing hormone (GnRH). In some embodiments, the peptide is GIP (1-42), human peptide. In someembodiments, the peptide is D6-GnRH. In some embodiments, the peptide is insulin. Insome embodiments, the peptide is teriparatide. In some embodiments, the peptide iscalcitronin salmon. In some embodiments, the peptide is ipamorelin. In some embodiments, the peptide is vasopressin. In some embodiments, the peptide is glucagon. In some embodiments, the peptide is aclerastide. In some embodiments, the peptide is goserelin. In some embodiments, the peptide is leuprolide. In some embodiments, the peptide is teriparatide. In some embodiments, the peptide is lixisenatide. In some embodiments, the peptide is desmopressin. In some embodiments, the peptide is oxytocin. In some embodiments, the peptide is corticotropin. In some embodiments, the peptide is sermorelin. In some embodiments, the peptide is bremelanotide. In some embodiments, the peptide is abaloparatide. In some embodiments, the peptide is deslorelin. In some embodiments, the peptide drug is a glucagon-like-peptide-1 (GLP-1) receptor agonist used to trat obesity and / or diabetes. In some such embodiments the peptidedrug is semaglutide, liraglutide, dulaglutide, albiglutide, or exenatide. Owing to the dramaticextension of duration of action of peptide drugs when incorporated into the conjugates of the disclosure, the GLP-1 agonist conjugates can be administered on a reduced dosing schedule, such as once weekly, once biweekly, once every three weeks, or once monthly. In some embodiments, the peptide drug is a glucagon-like-peptide-1 (GLP-1) and GIP (glucose-dependent insulinotropic polypeptide receptor agonist used to trat obesity and / or diabetes. In some such embodiments, the peptide drug is tirzepatide. Owing to the dramaticAttorney Docket No. 330272000240extension of duration of action of peptide drugs when incorporated into the conjugates of the disclosure, the GLP-1 / GIP agonist conjugates can be administered on a reduced dosingschedule, such as once weekly, once biweekly, once every three weeks, or once monthly.In some embodiments, the peptide is an endogenous opioid peptide. In some such embodiments, the peptide is endomorphin-1 or endomorphin-2. In other embodiments, the peptide is dermorphin. In some embodiments of a conjugate of formula (XII), D1is an opioid antagonist. In some embodiments, the opioid antagonist is naloxone, nalmefene, naltrexone, methylnaltrexone, nalbuphine, or nalorphine. In some embodiments of a conjugate of formula (XII), D1 is an opioid agonist. Insome embodiments, the opioid agonist is morphine, oxycodone, hydromorphone, ormethadone. In some embodiments, the conjugate is selected from the conjugates of Table A, or asalt thereof. In some embodiments, the conjugate is selected from the conjugates of Table A.Table A. Attorney Docket No.330272000240 Attorney Docket No.330272000240 Attorney Docket No. 330272000240 PHARMACEUTICAL COMPOSITIONS Provided herein are pharmaceutical compositions comprising one or more conjugatesof the disclosure (e.g., conjugate of formula (I)-(XII) or (II’)-(VIII’), or any variation orembodiment thereof, as described elsewhere herein, or a pharmaceutically acceptable salt of any of the foregoing. In some embodiments, provided herein is a pharmaceuticalcomposition comprising (i) a compound of any one of formula (I)-formula (XII) or (II’)-(VIII’), or any variation or embodiment thereof, as described elsewhere herein, or a pharmaceutically acceptable salt of any of the foregoing, and (ii) one or more pharmaceutically acceptable excipients. Suitable pharmaceutically acceptable excipients may include, for example, fillers, diluents, sterile aqueous solutions and various organic solvents, permeation enhancers, solubilizers, and adjuvants. Various substances may be embraced by the term excipient, including without limitation any substance used as a binder, disintegrant, coating, compression / encapsulation aid, cream or lotion, lubricant, solutions for parenteralAttorney Docket No. 330272000240administration, materials for chewable tablets, sweetener or flavoring, suspending / gelling agent, or wet granulation agent. Examples of suitable excipients are well-known to those skilled in the art. See, e.g., Handbook of Pharmaceutical Excipients, Pharmaceutical Press(2017), which is incorporated herein by reference in its entirety. Such compositions areprepared in a manner well known in the pharmaceutical art. See, e.g., Remington’s Pharmaceutical Sciences, Academic Press, 23rded. (2020), which is incorporated herein byreference in its entirety.METHODS OF TREATMENT In one aspect, provided herein are methods of increasing the plasma circulation time of an active agent, comprising covalently attaching an active agent to a binder of a plasmaprotein to form a conjugate of the disclosure (e.g., a conjugate of Formula (I)-(XII) or (II’)-(VIII’), or any variation thereof). In one aspect, provided herein are methods of increasing the in vivo half-life of anactive agent, comprising covalently attaching an active agent to a binder of a plasma proteinto form a conjugate of the disclosure (e.g., a conjugate of Formula (I)-(XII) or (II’)-(VIII’), orany variation thereof). In one aspect, provided herein are methods of increasing the duration of action (DOA)of an active agent, comprising covalently attaching an active agent to a binder of a plasmaprotein to form a conjugate of the disclosure. In one aspect, provided herein are methods reducing the immunogenicity of an activeagent in a subject, the methods comprising obtaining a delivery system having a ligand with(i) a high selectivity for a plasma protein endogenous to the subject, the molecular weight ofthe plasma protein ranging from about 30 kDa to about 80 kDa; (ii) a high binding affinity, Kd, of at least 10−6 M for the plasma protein; and, (iii) a molecular weight ranging fromabout 200 Da to about 2000 Da; and, a linker that ranges in length from about 10 angstromsto about 50 angstroms, or from 10 atoms to 50 atoms. The method also includes covalently attaching the delivery system to an active agent to create a conjugated active agent; and,administering the conjugated active agent to the subject; wherein, the plasma protein shieldsthe active agent from antibody generation in the subject after the administering. In one aspect, provided herein are methods of treating a disease, disorder, or conditioncomprising administering to an individual in need thereof a conjugate of the disclosure (e.g.,a conjugate of any one of formula (I)-formula (XII) or (II’)-(VIII’), or any variation orembodiment thereof, or a stereoisomer or tautomer thereof, or a pharmaceutically acceptableAttorney Docket No. 330272000240salt of any of the foregoing, or a pharmaceutical composition comprising a conjugate of the disclosure, or any variation or embodiment thereof, or a stereoisomer or tautomer thereof, or a pharmaceutically acceptable salt of any of the foregoing, and one or more pharmaceutically acceptable excipients. In some embodiments, a therapeutically effective amount of the compound is administered. In some embodiments, the half-life of the activity of the active agent (opioidantagonist or opioid agonist) can range from about 30 minutes to about 90 days whenadministered to a subject with the delivery systems provided herein. In some embodiments, the half-life of the activity of the active agent (opioid antagonist or opioid agonist) can range from about 30 minutes to about 30 days when administered to a subject with the delivery systems provided herein. For example, the half-life of the activity of the active agent can range from about 30 minutes to about 2 days when administered to a subject with a delivery system taught herein having a ligand that is highly selective for transthyretin, in some embodiments. Likewise, the half-life of the activity of the active agent can range from about 30 minutes to about 2 days when administered to a subject with a delivery system taught herein having a ligand that is highly selective for human serum albumin, in some embodiments. As such, in some embodiments the half-life of the activity of the active agent can be about 30 minutes, about 1 hour, about 2 hours, about 3 hours, about 4 hours, about 6 hours, about 8 hours, about 10 hours, about 12 hours, about 18 hours, about 24 hours, about 2 days, about 3 days, about 4 days, about 5 days, about 6 days, about 10 days, about 12 days, about 16 days, about 20 days, about 30 days, or any amount therein in increments of 1 hour, when administered to a subject with a delivery system taught herein. One of skill will appreciate that the half-life of the activity of an active agent that is administered to a subject using a delivery system taught herein can range from about 30 minutes to about 2 days, from about 1 hour to about 36 hours, from about 2 hours to about 20 hours, from about 2 hours to about 10 hours, from about 3 hours to about 30 hours, from about 3 hours to about 15 hours, from about 4 hours to about 40 hours, from about 4 hours to about 20 hours, from about 5 hours to about 50 hours, from about 5 hours to about 25 hours, or any range or any amount therein in increments of 1 hour. In one aspect, provided herein are methods of reducing the risk of recurrent respiratory depression, comprising administering to an individual in need thereof a conjugate of the disclosure prior to exposure to a drug.Attorney Docket No. 330272000240In one aspect, provided herein are methods of prophylaxis, comprising administering to an individual in need thereof a conjugate of the disclosure prior to exposure to a drug. In some embodiments, a conjugate of the disclosure is administered parenterally to a subject in need thereof. For instance, a conjugate of the disclosure can be administered subcutaneously, intravenously, intramuscularly or intrathecally. Conjugates of the disclosure, particularly conjugates of formula (II)-(XII) or (II’)-(VIII’), show enhanced adsorption from tissue, particularly subcutaneous tissue, owing, inpart, to the hydrophilicity of the TTR selective ligand. Following adsorption from tissue(e.g., subcutaneous tissue), reversible binding of the TTR selective ligand of the conjugateresults in significantly extended duration of action of the active agent. As set forth herein, cleavage of the linker between the TTR selective ligand and the active agent (opioid antagonist or opioid agonist) results in release of the active agent, hence allowing the active agent to exert its pharmacological effect. Moreover, it has been discovered that release of the active agent can be effectively controlled by proper selection of a cleavable moiety in the conjugate. For instance, particularester moieties (e.g., PABA or PHBA), as described herein, hydrolyze slowly followingadministration, thereby releasing the active agent in a controlled manner for an extended period of time. The slower hydrolysis and the high degree of binding to TTR effectivelyextend the plasma circulation time of the active agent.Therefore, the conjugates of the disclosure manifest several beneficial properties for a new prodrug approach. The balanced hydrophilicity of the conjugates allows for rapid adsorption into the blood from the tissue, the binding of TTR extends the half life, and the cleavable moiety allows for modulation of release of the drug. The desired rate of release of a particular active drug from a conjugate of the disclosure will vary from one active agent to another. In some embodiments, following the administration of a conjugate of the disclosure,the DOA of the drug is at least 12 hours. In some embodiments, following the administrationof a conjugate of the disclosure, the DOA of the drug is at least 20 hours. In someembodiments, following the administration of a conjugate of the disclosure, the DOA of thedrug is at least 24 hours. In some embodiments, following the administration of a conjugateof the disclosure, the DOA of the drug is at least 30 hours. In some such embodiments,following the administration of a conjugate of the disclosure, the DOA of the drug is at least40 hours. In some such embodiments, following the administration of a conjugate of thedisclosure, the DOA of the drug is at least 48 hours. In some such embodiments, followingAttorney Docket No. 330272000240the administration of a conjugate of the disclosure, the DOA of the drug is at least 72 hours.In some such embodiments, following the administration of a conjugate of the disclosure, theDOA of the drug is at least 96 hours. In some such embodiments, following theadministration of a conjugate of the disclosure, the DOA of the drug is at least 1 week. Insome such embodiments, following the administration of a conjugate of the disclosure, theDOA of the drug is at least 2 weeks. In some such embodiments, following theadministration of a conjugate of the disclosure, the DOA of the drug is at least 3 weeks. Insome such embodiments, following the administration of a conjugate of the disclosure, theDOA of the drug is at least 1 month. In some such embodiments, following theadministration of a conjugate of the disclosure, the DOA of the drug is from about 12 hoursto about 48 hours. In some such embodiments, following the administration of a conjugate ofthe disclosure, the DOA of the drug is from about 24 hours to about 48 hours. In someembodiments, following the administration of a conjugate of the disclosure, the DOA of thedrug is from about 48 hours to about 96 hours. In some embodiments, following theadministration of a conjugate of the disclosure, the DOA of the drug is from about 24 hoursto about 1 week. In some embodiments, following the administration of a conjugate of the disclosure,the plasma circulation of the drug is at least 12 hours. In some embodiments, following theadministration of a conjugate of the disclosure, the plasma circulation of the drug is at least20 hours. In some embodiments, following the administration of a conjugate of thedisclosure, the plasma circulation of the drug is at least 24 hours. In some embodiments,following the administration of a conjugate of the disclosure, the plasma circulation of thedrug is at least 30 hours. In some such embodiments, following the administration of aconjugate of the disclosure, the plasma circulation of the drug is at least 40 hours. In somesuch embodiments, following the administration of a conjugate of the disclosure, the plasmacirculation of the drug is at least 48 hours. In some such embodiments, following theadministration of a conjugate of the disclosure, the plasma circulation of the drug is at least72 hours. In some such embodiments, following the administration of a conjugate of thedisclosure, the plasma circulation of the drug is at least 96 hours. In some suchembodiments, following the administration of a conjugate of the disclosure, the plasmacirculation of the drug is at least 1 week. In some such embodiments, following theadministration of a conjugate of the disclosure, the plasma circulation of the drug is at least 2weeks. In some such embodiments, following the administration of a conjugate of thedisclosure, the plasma circulation of the drug is at least 3 weeks. In some such embodiments,Attorney Docket No. 330272000240following the administration of a conjugate of the disclosure, the plasma circulation of thedrug is at least 1 month. In some such embodiments, following the administration of aconjugate of the disclosure, the plasma circulation of the drug is from about 12 hours to about48 hours. In some such embodiments, following the administration of a conjugate of thedisclosure, the plasma circulation of the drug is from about 24 hours to about 48 hours. Insome embodiments, following the administration of a conjugate of the disclosure, the plasmacirculation of the drug is from about 48 hours to about 96 hours. In some embodiments,following the administration of a conjugate of the disclosure, the plasma circulation of thedrug is from about 24 hours to about 1 week.In some embodiments, the active drug (D1) delivered by a conjugate of the disclosure is a small molecule, a nucleotide, an oligonucleotide, a polynucleotide, an amino acid, anoligopeptide, a polypeptides, or a protein. Active drugs, include. can include, but are notlimited to, antiproliferatives, antineoplastics, antimitotics, anti-inflammatories, antiplatelets, anticoagulants, antifibrins, antithrombins, antibiotics, antiallergics, antioxidants. Antiproliferatives include, for example, actinomycin D, actinomycin IV, actinomycin I1, actinomycin X1, actinomycin C1, and dactinomycin (Cosmegen.RTM., Merck & Co., Inc.). Antineoplastics or antimitotics include, for example, paclitaxel (TAXOL, Bristol-MyersSquibb Co.), docetaxel (TAXOTERE, Aventis S.A.), methotrexate, irinotecan, SN-38,azathioprine, vincristine, vinblastine, fluorouracil, doxorubicin hydrochloride (ADRIAMYCIN, Pfizer, Inc.) and mitomycin (MUTAMYCIN, Bristol-Myers Squibb Co.), and any prodrugs, codrugs, metabolites, analogs, homologues, congeners, derivatives, salts and combinations thereof. Antiplatelets, anticoagulants, antifibrin, and antithrombins include, for example, sodium heparin, low molecular weight heparins, heparinoids, hirudin, argatroban, forskolin, vapiprost, prostacyclin and prostacyclin analogues, dextran, D-phe-pro- arg-chloromethylketone (synthetic antithrombin), dipyridamole, glycoprotein IIb / IIIa platelet membrane receptor antagonist antibody, recombinant hirudin, and thrombin inhibitors (ANGIOMAX, Biogen, Inc.), and any prodrugs, codrugs, metabolites, analogs, homologues, congeners, derivatives, salts and combinations thereof. Cytostatic or antiproliferative agents include, for example, angiopeptin, angiotensin converting enzyme inhibitors such as captopril (CAPOTEN and CAPOZIDE, Bristol-Myers Squibb Co.), cilazapril or lisinopril (PRINVIL and PRINZIDE, Merck & Co., Inc.); calcium channel blockers such as nifedipine; colchicines; fibroblast growth factor (FGF) antagonists, fish oil (omega 3-fatty acid); histamine antagonists; lovastatin (MEVACOR, Merck & Co., Inc.); monoclonal antibodies including, but not limited to, antibodies specific for Platelet-Derived Growth Factor (PDGF)Attorney Docket No. 330272000240receptors; nitroprusside; phosphodiesterase inhibitors; prostaglandin inhibitors; suramin; serotonin blockers; steroids; thioprotease inhibitors; PDGF antagonists including, but not limited to, triazolopyrimidine; and nitric oxide, and any prodrugs, codrugs, metabolites, analogs, homologues, congeners, derivatives, salts and combinations thereof. Antiallergic agents include, but are not limited to, pemirolast potassium (ALAMAST, Santen, Inc.), and any prodrugs, codrugs, metabolites, analogs, homologues, congeners, derivatives, salts and combinations thereof. In some embodiments, a conjugate of the disclosure can be administered in combination with a second drug. For instance, in some embodiments, a conjugate of the disclosure can be administer in combination with a second drug (D2) that is in unconjugated form. The second drug (D2) in unconjugated form can be the same of different than the drug (D1) of the conjugate. In some embodiments, both D1and D2are anti-cancer drugs. In some embodiments. a conjugate of the disclosure is administered subcutaneously toa human subject at a dose of from about 0.005 mg / kg to about 40 mg / kg. In someembodiments. a conjugate of the disclosure is administered subcutaneously to a humansubject at a dose of from about 0.01 mg / kg to about 40 mg / kg. In some embodiments. aconjugate of the disclosure is administered subcutaneously to a human subject at a dose offrom about 0.005 mg / kg to about 10 mg / kg. In some embodiments. a conjugate of thedisclosure is administered subcutaneously to a human subject at a dose of from about 0.1mg / kg to about 10 mg / kg. In some embodiments. a conjugate of the disclosure isadministered subcutaneously to a human subject at a dose of from about 0.5 mg / kg to about10 mg / kg. In some embodiments, a conjugate of the disclosure is administeredsubcutaneously to a human subject at a dose of from about 5 mg / kg to about 40 mg / kg. In some embodiments. a conjugate of the disclosure is administered subcutaneously to a human subject at a dose of from about 10 mg / kg to about 30 mg / kg. In some embodiments. a conjugate of the disclosure is administered subcutaneously to a human subject at a dose of from about 15 mg / kg to about 25 mg / kg. KITS The present disclosure further provides kits for carrying out the methods disclosedherein. The kits may comprise a conjugate of the disclosure or pharmaceutically acceptablesalt thereof as described herein and suitable packaging. The kits may comprise one or more containers comprising any compound described herein. In one aspect, a kit includes acompound of the disclosure or a pharmaceutically acceptable salt thereof, and a label and / orAttorney Docket No. 330272000240instructions for use of the compound in the treatment of a disease or disorder described herein. The kits may comprise a unit dosage form of the compound. Provided herein is a kit, comprising (i) a conjugate of the disclosure, or a stereoisomeror tautomer thereof, or a pharmaceutically acceptable salt of any of the foregoing, or apharmaceutical composition comprising a compound of formula (I), or any variation orembodiment thereof, or a stereoisomer or tautomer thereof, or a pharmaceutically acceptablesalt of any of the foregoing, and one or more pharmaceutically acceptable excipients and (ii)instructions for use in treating In some embodiments, the individual is a human. Articles of manufacture are also provided, wherein the article of manufacturecomprises a conjugate of the disclosure, or any variation or embodiment thereof, or astereoisomer or tautomer thereof, or a pharmaceutically acceptable salt of any of the foregoing, in a suitable container In some embodiments, the container may be a vial, jar, ampoule, preloaded syringe, or intravenous bag. METHODS OF PREPARING Provided herein are processes of preparing a conjugate of the disclosure, or anyvariation or embodiment thereof, or a pharmaceutically acceptable salt of any of theforegoing. The following synthetic methods, along with those that are detailed in theExamples, are merely illustrative of some of the methods by which the compounds of the present disclosure, or an embodiment or aspect thereof, can be synthesized. Various modifications to these synthetic reaction schemes can be made, as will be apparent to those ofordinary skill in the art. Although certain exemplary embodiments are depicted and describedherein, the compounds of the present disclosure, or any variation or embodiment thereof, may be prepared using appropriate starting materials according to the methods described generally herein and / or by methods available to one of ordinary skill in the art. When a specific stereoisomer, or an unspecified stereoisomer, or a mixture of stereoisomers is shown in the following general procedures, it is understood that similar chemical transformations can be performed on other specific stereoisomers, or an unspecified stereoisomer, or mixtures thereof. Representative examples of making conjugates of the disclosure are provided in Example 1. In some embodiments, a hydroxyl group of a drug moiety can be subjected to an esterification reaction using methods known in the art. In some embodiments, the reactive hydroxyl group is an alkyl hydroxyl group on a small molecule, peptide or protein. In someAttorney Docket No. 330272000240embodiments, the reactive hydroxyl group is a phenol hydroxyl group on a small molecule, peptide or protein. In some embodiments, a tyrosine residue of a peptide or protein serves as the site of esterification. In some embodiments, a serine residue on a peptide or protein serves as the site of esterification. Where specific reagents or solvents are specified for reactions in the general procedures, the skilled artisan will recognize that other reagents or solvents can be substituted as desired. EXAMPLES The following synthetic reaction schemes, which are detailed in the Examples, are merely illustrative of some of the methods by which the compounds of the present disclosure, or an embodiment or aspect thereof, can be synthesized. Various modifications to these synthetic reaction schemes can be made, as will be apparent to those of ordinary skill in the art. The starting materials and the intermediates of the synthetic reaction schemes can be isolated and purified if desired using conventional techniques, including, but not limited to, filtration, distillation, crystallization, chromatography, and the like. Such materials can be characterized using conventional means, including physical constants and spectral data. Although certain exemplary embodiments are depicted and described herein, the compounds of the present disclosure, or any variation or embodiment thereof, may be prepared using appropriate starting materials according to the methods described generally herein and / or by methods available to one of ordinary skill in the art. All publication, patent applications, patents, and other references mentioned herein are expressly incorporated by reference in their entireties, to the same extent as if each were incorporated by reference individually.Example 1: Synthesis and Characterization of Conjugates of the DisclosureMaterials and Methods Materials and reagents. Naloxone hydrochloride (#N285000) was purchased fromToronto Research Chemicals, Toronto, Ontario. Nalmefene hydrochloride (#408550) waspurchased from Tocris Bioscience™. Naloxone-D5100 µg / mL (#N-063) was purchased fromCerilliant. Morphine sulfate (CII) (#M1167) and Fentanyl citrate (CII) (#F1147) werepurchased from Spectrum Chemical Manufacturing Corporation. Digitonin (#D0540) andLoperamide hydrochloride (# L0154) were purchased from Fisher Scientific. Dodecyl azide(#A1887) was purchased from Synthonix. Prealbumin from human plasma (human TTR)Attorney Docket No. 330272000240(#P1742) and human serum (#H4522) were purchased from Sigma Aldrich. Innovative gradeUS origin rat plasma (#IGRTSDPLANAH), rabbit plasma (#IGRBPLANAH), monkey cynomolgus plasma (#IGMNCYPLANAH) and pooled human plasma (#IPLAWBNAH) were purchased from Innovative Research. XTreme 200 Mixed gender human livermicrosomes (#1910096), Male IGS SD rat liver microsomes (#2210274), Male cynomolgusmonkey liver microsomes (#2210248), and NADPH RapidStart Regeneration System forExtended Metabolism (#K5100-5) were purchased from Xenotech. Human carboxylesterase1 (CES1, #E0287-1VL) and carboxylesterase 2 (CES2, #C4749) were purchased from SigmaAldrich. RPMI-1640 Medium and minimum Eagle’s medium (HyClone, Utah, USA), fetalbovine serum (Gemini), penicillin / streptomycin (100 unit / mL and 100 µg / mL (Gibco, NY,USA) and L-Glutamine (Glutamax-100X, #35-050-061, Gibco, NY, USA) were bought fromthe companies mentioned in the parentheses. CellBIND® 96- well clear plates (#CLS3340-50EA) were purchased from Corning®. CellTiter 96 non-radioactive cell proliferation assaykit (#G4000, Promega, WI, USA) was used to perform the MTT (3-(4, 5-dimethylthiazol- 2-yl)-2, 5 diphenyltetrazolium bromide) assay for the test compounds in the cell lines.Chemical synthesis and HPLC purity analysis Chemistry general procedures. All reactions were carried out under an argon ornitrogen atmosphere using dry solvents under anhydrous conditions, unless otherwise noted. The solvents used were ACS grade from Fisher. Yields refer to chromatographically and spectroscopically (1H NMR and13C NMR) homogeneous materials, unless otherwise noted. Reagents were purchased from Aldrich and Fisher and used without further purification. Reactions were monitored by thin-layer chromatography (TLC) carried out on EMDMillipore® silica gel 60 plastic TLC plates coated with fluorescent indicator F254 TLC(#1.05735.0001), using UV light and iodine chamber as visualizing agents. Normal phaseflash column chromatography was carried out using Combi Flash® Rf+ Lumen instrument (Teledyne ISCO) with High Performance Silica Flash Column (RediSep® Rf+ Gold), and preparative thin-layer chromatography (PTLC) separations were carried out on Analtech® 2mm (60F-254) (#P02015).1H NMR and13C NMR spectra were recorded on a JEOL JNM−ECA 600 spectrometer and calibrated using residual undeuterated solvent as an internalreference. High-resolution mass spectra (HRMS) were performed at the mass spectrometryfacility at UC Berkley using electrospray ionization from solution. Coupling constants (J) were expressed in Hertz. Preparative HPLC method for purification of the synthesized compounds. Thepurification was performed on a Waters 150Q LC System w / PDA and FlexInject systemAttorney Docket No. 330272000240connected to a photodiode array detector operating between the UV ranges of 190-800 nm, using Waters Chromesope V2.1 software. The HPLC analysis was performed on an SunFire® Prep C18 OBD Column (19x250 mm, 5 μm) at ambient temperature upon injection of 5 mL of each sample to obtain the chromatogram at 310 nm UV absorbance. The mobile phase was composed of solvent A consisting of methanol-water (5:95, v / v) containing 0.1% trifluoroacetic acid and solvent B consisting of methanol-water (95:5, v / v) containing 0.1%trifluoroacetic acid and delivered at a flow of 20 mL min-1. The HPLC program was anisocratic gradient for the first 4 min at 0% solvent B followed by a linear increase from 0- 100% solvent B from 4-20 min followed by isocratic elution at 100% solvent B until 24 min followed by linearly going back down to 0% B at 26 min and then remaining at 0% solvent B for 4 min. Analytical HPLC method for evaluating the purity of the synthesizedcompounds. Detailed HPLC information of key compounds (traces, retention times, and % purity) are included below. The analysis of the key compounds’ purity (>95% for all compounds) was performed using C18 reverse-phase HPLC columns on Arc Premier Waters module HPLC system connected to a Waters 2998 photodiode array detector operating between the UV ranges of 190-800 nm and quantified using the Empower 3 software. TheHPLC analysis was performed on a Waters™ XBridge C18 column (4.6x250 mm, 5μm),eluting at 1 mL min-1, at ambient temperature upon injection of 20 μL of each sample toobtain the chromatogram at 310 nm UV absorbance. The mobile phase was composed ofsolvent A consisting of methanol-water (5:95, v / v) containing 0.1% ammonium hydroxide and solvent B consisting of methanol-water (95:5, v / v) containing 0.1% ammonium hydroxide. The HPLC program for the C18 column was a gradient method increasing linearly from 0-100 % solvent B at 0-20 min, followed by isocratic elution at 100% solvent B until 25min, going back down to 0% of B at 27 min, and then remaining at 0% of B for 3 min.General Procedure A. Preparation of naloxone free base. To a solution of naloxone hydrochloride (1 equivalent) in dichloromethane at ambient temperature, the tertiary amine base N,N-diisopropylethylamine (1.25 equivalents) is added. After stirring for a brief period (e.g., 5–10 minutes), the solvent is removed under reduced pressure to yield the corresponding free base of naloxone.General Procedure B. Synthesis of estersAttorney Docket No. 330272000240To the selected drug (D1), a solution of the selected carboxylic acid (1.2 eq.) and acatalytic amount of an acylation catalyst (e.g., 4-dimethylaminopyridine, 0.2 eq.) dissolved in dichloromethane was added under an inert atmosphere (e.g., N2 or argon). The reaction mixture was stirred for a short period to allow pre-activation, followed by the addition of a coupling reagent such as N,N'-dicyclohexylcarbodiimide (approximately 1 eq.). The reaction mixture was stirred at ambient temperature for an extended period (e.g., 12–24 hrs) to ensure complete conversion. The mixture was then filtered and the solvent was removed under reduced pressure. The crude product was purified using chromatographic techniques (e.g., flash column chromatography on silica gel using an appropriate gradient of ethyl acetate and hexane) to afford the target ester. The structure and purity of the product were confirmed using analytical methods such as nuclear magnetic resonance spectroscopy (NMR) and mass spectrometry (MS). General Procedure C. Copper(I)-Catalyzed Azide–Alkyne Cycloaddition (CuAAC). The click (CuAAC) coupling was carried out by coupling naloxone-alkyne / drug- alkyne (1.2 equivalent), azide-linker-AG10 / azide linker (1 equivalent), CuSO4.5H2O (0.5 equivalent), and sodium ascorbate (1.2 equivalent) in a mixture of tetrahydrofuran / water (2:1). The reaction mixture was stirred at room temperature overnight. The tetrahydrofuran and water were removed under reduced pressure. The residues were either purified by silicagel chromatography or were dissolved in methanol and purified by preparative reverse phaseHPLC to afford the desired product. General Procedure D. Removal of Boc protecting groups Boc-protected and conjugates and precursors were treated with a mixture ofdichloromethane / trifluoroacetic acid (3:1). The reaction mixture was stirred at room temperature for 2 hr under inert atmosphere. Next, ammonium hydroxide dissolved in water (28-36%) was added slowly dropwise along with methanol. This solution was then concentrated under reduced pressure and purified by preparative reverse phase HPLC to afford the desired products.Attorney Docket No. 330272000240General Procedure E. Fmoc peptide synthesis. Rink amide resin was first swollen in dichloromethane (DCM) to prepare it for peptide synthesis. The Fmoc protecting group was removed using 20% piperidine in DMF for 25 minutes, followed by thorough washing with DMF. Coupling was carried out by preactivating the Fmoc-protected amino acid (3 equivalents) with HBTU (3 equivalents) and DIPEA (6 equivalents) in DMF for 3 minutes before adding the mixture to the resin and agitating for 40 minutes. Coupling and Fmoc deprotection were monitored using the Kaiser test to ensure completion. Upon completion of the synthesis, global cleavage from the resin and removal of acid-labile protecting groups (such as t-Boc and t-Bu) were achieved using a cocktail of 95% trifluoroacetic acid (TFA), 2.5% water, and 2.5% triisopropylsilane (TIPS) for 2 hours at room temperature. The crude peptide / peptide ester conjugate was then precipitated with cold diethyl ether, collected by centrifugation, washed, and dried. The final product was purified using preparative HPLC. Synthesis of AG10-L-E2-Naloxone Scheme 1 shows a schematic of the synthesis of AG10-L-E2-Naloxone. Scheme 1. Synthesis of AG10-L-E2-Naloxone.Attorney Docket No. 330272000240ethyl 4-((tert-butoxycarbonyl)(prop-2-yn-1-yl)amino)benzoate (1). To a solutionof ethyl 4-(prop-2-yn-1-ylamino)benzoate (2 g, 9.84 mmol, 1 equiv), Di-tert-butyldicarbonate (2.6 g, 11.9 mmol, 1.2 equiv), 4-dimethylaminopyridine (0.24 g, 1.96 mmol, 0.2equiv), in dry tetrahydrofuran (12 mL) under a nitrogen atmosphere at room temperature, wasadded triethylamine (1.2 g, 1.64 mL, density of 0.73 g mL-1, 11.86 mmol, 1.2 equiv). Thereaction mixture is solution was stirred under overnight at 80οC. The reaction was allowed tocool to room temperature after which formic acid (906 mg, 0.742 mL, density of 1.22 g mL-1,19.68 mmol, 2 equiv) in 3 mL ethyl acetate was added dropwise into the stirring reactionvessel at room temperature. The solvent and excess formic acid were then dried underreduced pressure. The remaining residue was dissolved in ethyl acetate (30 mL), filtered, andthe solvent was removed under reduced pressure. The resulting residue was purified by flashcolumn chromatography (silica gel, 0-100% ethyl acetate / hexane) to afford compound 1(2.76 g, 92.4% isolated yield) as a clear yellow viscous liquid; 1H NMR (600 MHz, CDCl3) δ7.98 (d, 2H, J = 9), 7.38 (d, 2H, J = 9), 4.39 (s, 2H), 4.33 (q, 2H, J = 7.2), 2.24 (s, 1H), 1.44(s, 9H), 1.35 (t, 3H, J = 7.2); 13C-NMR (150 MHz, CDCl3) δ 166.12, 153.39, 146.16, 130.16,127.75, 125.23, 100.00, 81.83, 79.64, 72.22, 61.02, 39.49, 28.29, 14.40. HRMS (DART) m / z:calculated for C17H21NO4 [M+Na]+ 326.1363; found: 326.1364.(4aS,7aR,12bS)-3-allyl-4a-hydroxy-7-oxo-2,3,4,4a,5,6,7,7a-octahydro-1H-4,12- methanobenzofuro[3,2-e]isoquinolin-9-yl 4-((tert-butoxycarbonyl)(prop-2-yn-1-yl)amino)benzoate (2). To a stirring solution of 1 (2.76 g, 9.1 mmol, 1 equiv) in methanol(7.5 mL) at room temperature, was added Sodium Hydroxide (729 mg, 18.2 mmol, 2 equiv) in water (3.75 mL). This reaction mixture was stirred overnight at 50oC after which the water and methanol solvents were dried under reduced pressure. The remaining residue was re-dissolved with ethyl acetate (30 mL) containing formic acid (2.44 g, 2 mL, density of 1.22 gmL-1, 53 mmol), filtered, and the solvent was removed under reduced pressure. The resulting residue was purified by flash column chromatography (silica gel, 0-100% ethylacetate / hexane) to afford acid hydrolysis product of 1 (2.46 g) as a white powder which useddirectly in the next step. To a solution of Naloxone-hydrochloride (1.32 g, 3.63 mmol, 1equiv) in CH2Cl2(30 mL) at room temperature, was added N,N-Diisopropylethylamine (0.88g, 1.2 mL, density of 0.742 g mL-1, 4.5 mmol, 1.25 equiv) and stirred for five minutes. TheCH2Cl2 was then removed under reduced pressure leaving a dried residue. To this residue, asolution of acid hydrolysis product of 1 (1.2 g, 4.36 mmol, 1.2 equiv) and 4-dimethylaminopyridine (89 mg, 0.72 mmol, 0.2 equiv) dissolved in CH2Cl2(30 mL) at roomtemperature was added under nitrogen atmosphere. The reaction mixture was stirred for fiveAttorney Docket No. 330272000240minutes followed by the addition of N-N’-dicyclohexylcarboiimide (0.75 g, 3.63 mL, 3.63 mmol, 1 equiv) in a 1 M solution in anhydrous CH2Cl2under nitrogen atmosphere. The reaction mixture was stirred at room temperature for 48 hr after which it was filtered and excess CH2Cl2 was removed under reduced pressure. The resulting residue was purified by flash column chromatography (silica gel, 0-100% ethyl acetate / hexane) to afford compound 2 (1.5 g, 70% isolated yield) a white powder;1H NMR (600 MHz, CDCl3) δ 8.16 (d, 2H, J = 7.8), 7.44 (d, 2H, J = 8.4), 6.93 (d, 1H, J = 8.4), 6.71 (d, 1H, J = 8.4), 5.83-5.75 (m, 1H), 5.28-5.15 (m, 2H), 4.68 (s,1H), 4.41 (s,2H), 3.20-3.12 (m, 3H), 3.04-2.96 (m, 2H), 2.66-2.57 (m, 2H), 2.43-2.36 (m, 1H), 2.31-2.24 (m, 2H), 2.19-2.11 (m, 1H), 1.88-1.82 (m, 1H), 1.67-1.59 (m, 2H), 1.46 (s, 9H); 13C-NMR (150 MHz, CDCl3) δ 207.82, 163.73, 153.47, 148.11,146.93, 135.19, 132.86, 131.27, 130.52, 130.34, 126.30, 125.43, 123.20, 119.63, 118.44, 100.00, 90.78, 82.08, 79.62, 72.59, 70.24, 62.06, 57.70, 50.80, 43.38, 39.51, 36.25, 31.34,30.74, 28.42, 23.13; HRMS (DART) m / z: calculated for C34H36N2O7 [M+H]+ 585.2595;found: 585.2593. 3-((6-((2-(2-(2-(4-(((4-((((4aS,7aR,12bS)-3-allyl-4a-hydroxy-7-oxo- 2,3,4,4a,5,6,7,7a-octahydro-1H-4,12-methanobenzofuro[3,2-e]isoquinolin-9- yl)oxy)carbonyl)phenyl)amino)methyl)-1H-1,2,3-triazol-1- yl)ethoxy)ethoxy)ethyl)amino)hexyl)oxy)-5-(3-(3,5-dimethyl-1H-pyrazol-4-yl)propoxy)benzoic acid (AG10-L-E2-Naloxone). The click (CuAAC) coupling was carriedout by coupling compound 2 (561 mg, 0.96 mmol, 1.2 equiv), compound 3 (515 mg, 0.8mmol, 1 equiv; synthesized as reported earlier), CuSO4.5H2O (100 mg, 0.4 mmol, 0.5 equiv), and sodium ascorbate (190 mg, 0.96 mmol, 1.2 equiv) in a) 9 mL mixture of tetrahydrofuran / water (2:1). The reaction mixture was stirred at room temperature overnight.The tetrahydrofuran and water were removed under reduced pressure. The residue wasdissolved in water and extracted with CH2Cl2. The organic extracts were concentrated under reduced pressure and purified by flash column chromatography (silica gel, 0-100% CH2Cl2 / methanol) to afford the di-Boc protected AG10-L-E2-Naloxone intermediate which wasdirectly treated with a 4 mL mixture of CH2Cl2 / trifluoroacetic acid (3:1). The reactionmixture and stirred at room temperature for 2 hr under inert atmosphere. Next, ammoniumhydroxide dissolved in water (28-36%) was added slowly dropwise along with 3 mL of methanol until no hydrogen gas was seen to be forming. This solution was then concentrated under reduced pressure and purified by preparative reverse phase HPLC to afford AG10-L-E2-Naloxone (633 mg, 64% isolated yield) as a sticky solid; 1H NMR (600 MHz, CD3OD) δ7.84-7.79 (m, 3H), 7.03-6.99 (m, 2H), 6.95-6.87 (m, 1H), 6.84-6.76 (m, 1H), 6.65-6.60 (m,Attorney Docket No. 3302720002402H), 4.42 1H), 1H),1.94-m / z:m n 013,ecna brosb A Scheme 2. Synthesis of AG10-L-E2-COOH.3-((6-((2-(2-(2-(4-(((4-carboxyphenyl)amino)methyl)-1H-1,2,3-triazol-1- yl)ethoxy)ethoxy)ethyl)amino)hexyl)oxy)-5-(3-(3,5-dimethyl-1H-pyrazol-4- yl)propoxy)benzoic acid (AG10-L-E2-COOH). To a solution of AG10-L-E2-Naloxone(1000 mg, 0.97 mmol, 1 equiv) in methanol (4 mL), was added sodium hydroxide (77.6 mg,1.94 mmol, 2 equiv) in water (1 mL). The solution was stirred overnight at 50ºC. The solventwas then removed under reduced pressure. The remaining residue was purified by preparativeAttorney Docket No. 330272000240reverse phase HPLC to afford AG10-L-E2-COOH (420 mg, 60% isolated yield); HRMS(DART) m / z: calculated for C37H51N7O8 [M+H]+ 722.3872; found: 722.3869. Synthesis of C12-L-E2-Naloxone Scheme 3 shows a schematic of the synthesis of AG10-L-E2-COOH Scheme 3. Synthesis of C12-E2-Naloxone.(4aS,7aR,12bS)-3-allyl-4a-hydroxy-7-oxo-2,3,4,4a,5,6,7,7a-octahydro-1H-4,12- methanobenzofuro[3,2-e]isoquinolin-9-yl 4-(((1-dodecyl-1H-1,2,3-triazol-4- yl)methyl)amino)benzoate (C12-E2-Naloxone). The click (CuAAC) coupling was carriedreacting compound 2 (500 mg, 0.86 mmol, 1 equiv), Dodecyl azide (182 mg, 0.85 mmol, 1equiv), CuSO4.5H2O (106.7 mg, 0.425 mmol, 0.5 equiv), and sodium ascorbate (169.4 mg,0.855 mmol, 1 equiv) in a 3 mL mixture of THF / H2O (4:1). The reaction mixture was stirredat room temperature overnight. The solution was concentrated under reduced pressure. Theresidue was extracted by ethyl acetate. The organic extract was concentrated under reducedpressure to afford an intermediate and was used for the next step directly. Then, to a solutionof the intermediate, was added a mixture containing TFA and CH2Cl2, (1:4 ratio) (1 mL), andthe reaction mixture was stirred at room temperature for 2 hr. The solution was concentratedunder reduced pressure and purified by preparative HPLC to afford compound C12-E2- Naloxone. (255 mg, 43% yield over two steps);1H NMR (600 MHz, CD3OD) δ 7.87-7.78 (m, 3H), 6.94 (t, 1H, J = 8.4 ), 6.85-6.78 (m, 1H), 6.61 (s, 2H), 5.91-5.79 (m, 1H), 5.64-5.52 (m,Attorney Docket No. 3302720002402H), 4.82 (s, 1H), 4.58-4.34 (m, 1H), 4.27 (t, 2H, J = 7.2 ), 3.92-3.66 (m, 2H), 3.57-3.32 (m, 2H), 3.17-2.50 (m, 3H), 2.21-1.46 (m, 9H), 1.26-1.06 (m, 18H), 0.79 (t, 3H, J = 7.2);13C- NMR (150 MHz, CD3OD) δ 206.56, 164.97, 148.36, 133.63, 133.04, 131.95, 128.21, 127.65, 126.50, 125.52, 125.30, 124.27, 123.05, 120.21, 119.64, 111.58, 97.09, 93.49, 89.43, 69.73, 62.55, 55.47, 50.14, 49.02, 46.31, 33.42, 31.73, 29.89, 29.39, 29.19, 28.69, 27.59, 26.97,26.08, 25.41, 24.73, 22.93, 22.40, 13.12; HRMS (DART) m / z: calcd for C41H53N5O5 [M+H]+696.4119; found: 696.4121. Synthesis of AG10-L-E1-Naloxone Scheme 4 shows a schematic of the synthesis of AG10-L-E1-Naloxone Scheme 4. Synthesis of AG10-L-E1-Naloxone. 3-((6-((2-(2-(2-(4-(3-(((4aS,7aR,12bS)-3-allyl-4a-hydroxy-7-oxo-2,3,4,4a,5,6,7,7a- octahydro-1H-4,12-methanobenzofuro[3,2-e]isoquinolin-9-yl)oxy)-3-oxopropyl)-1H- 1,2,3-triazol-1-yl)ethoxy)ethoxy)ethyl)amino)hexyl)oxy)-5-(3-(3,5-dimethyl-1H-pyrazol- 4-yl)propoxy)benzoic acid (AG10-L-E1-Naloxone). To a solution of naloxonehydrochloride (500 mg, 1.374 mmol, 1 equiv) in CH2Cl2 (4 mL) at room temperature, wasadded N,N-Diisopropylethylamine ( 0.24 mL ,1.374 mmol, 1 equiv) and stirred for 10 min.The solution was concentrated under reduced pressure to afford naloxone, which was used Attorney Docket No.330272000240 directly in the next step.4-pentynoic acid (134.8 mg, 1.374 mmol, 1 equiv), DMAP (33.6 mg, 0.275 mmol, 0.2 equiv), was added to naloxone in CH2Cl2(3 ml) under argon atmosphere. DCC (0.46 ml, 2.748 mmol, 2 equiv) was then added to the solution under argon atmosphere and reaction was stirred overnight at room temperature. The reaction was purified by flash column chromatography (silica gel, 0-100% ethyl acetate / hexane) and the intermediate was used directly in the next step. The click (CuAAC) coupling was carried out by coupling the residue and de-Boc compound 3 (300 mg, 0.549 mmol, 1 equiv; reported earlier), CuSO4.5H2O (68.5 mg, 0.2745 mmol, 0.5 equiv), and sodium ascorbate (108.8 mg, 0.549 mmol, 1 equiv) in a 3 mL mixture of THF / H2O (4:1). The reaction mixture was stirred at room temperature overnight. The solution was concentrated under reduced pressure and purified by preparative HPLC to afford compound AG10-L-E1-Naloxone. (250 mg, 47% yield over two steps);1H NMR (600 MHz, DMSO-d6) δ 7.95 (s, 1H), 7.05-6.95 (m, 3H), 6.84 (d, 1H, J = 8.4), 6.72-6.68 (m, 1H), 5.95-5.87 (m, 1H), 5.62-5.54 (m, 2H), 5.11 (s, 1H), 4.52-4.46 (m, 2H), 4.03-3.91 (m, 5H), 3.86-3.76 (m, 3H), 3.65 (d, 1H, J = 6), 3.64-3.61 (m, 2H), 3.59-3.49 (m, 5H), 3.24-3.16 (m, 1H), 3.12-3.04 (m, 3H), 3.04-2.80 (m, 7H), 2.70-2.56 (m, 1H), 2.5 (s, 1H), 2.29-2.08 (m, 8H), 2.06-1.91 (m, 1H), 1.87-1.80 (m, 2H), 1.75-1.66 (m, 2H), 1.65-1.57 (m, 2H), 1.55-1.15 (m, 7H);13C-NMR (150 MHz, DMSO-d6) δ 206.93, 170.46, 167.45, 160.28, 158.82, 158.60, 147.92, 145.46, 133.38, 132.69, 129.15, 128.96, 128.14, 125.67, 124.18, 123.07, 120.70, 107.81, 106.19, 89.91, 70.13, 70.07, 69.91, 69.28, 68.15, 67.10, 66.14, 61.85, 55.63, 55.44, 49.81, 49.03, 47.38, 46.65, 46.06, 35.16, 33.41, 30.88, 29.49, 28.86, 27.79, 26.15, 25.81, 25.49, 23.38, 21.18, 18.73, 10.42. HRMS (DART) m / z: calcd for C51H67N7O11[M+H]+954.4971; found: 954.4971. MinutesAttorney Docket No. 330272000240Synthesis of AG10-Short-L-E2-Naloxone AG10-Short-L-E2-Naloxone was prepared according to General Procedure B using , followed by General Procedure D.Attorney Docket No. 330272000240Synthesis of AG10-L-E2-Propofol AG10-L-E2-Propofol was prepared according to General Procedure B using Synthesis of AG10-L-E2-Estrone AG10-L-E2-Estrone was prepared according to General Procedure B using Synthesis of AG10-L-E2-Tyr-AlaAttorney Docket No. 330272000240AG10-L-E2-Tyr-Ala was prepared according to General Procedure B using , followed by General Procedure D, followed by GeneralProcedure C using .Synthesis of AG10-L-E2-Endomorphin-2 Endomorphin-2 was prepared according to General Procedure B using , followed by General Procedure D, followed by General using endomorphin-2 and di-tert-butyl dicarbonate in the presence of triethylamine andDMAP in THF at about 80°C. Synthesis of AG10-L-E2-Dermorphin AG10-L-E2-Dermorphin was prepared according to General Procedure E. Scheme5 shows the synthesis of AG10-L-E2-Dermorphin.Attorney Docket No. 330272000240 Scheme 5. Synthesis of AG10-L-E2-Dermophin Analytical HPLC method. Test compounds were analyzed using Waters™ XBridgeC18 column (4.6x250 mm, 5 μm) on Arc Premier Waters module HPLC system connected toa Waters 2998 photodiode array detector operating between the UV ranges of 190-800 nm.HPLC analysis was performed using a gradient method increasing linearly from 0-100%solvent B in 25 min. The mobile phase was composed of solvent A consisting of methanol-water (5:95, v / v) containing 0.1% ammonium hydroxide and solvent B consisting of methanol-water (95:5, v / v) containing 0.1% ammonium hydroxide, at a flow rate of 1.0 mL min-1. Solubility of compounds in potassium phosphate buffer (pH 7.4). Stocks solutions(10 mM) of test compounds were prepared in DMSO and stored at -20°C. Compounds (200µM) were incubated in 50 mM potassium phosphate buffer (pH 7.4) at 37oC for 72 hr. Thesamples were vortexed, spun for 5 min at 12000 rpm, and supernatant was filtered. A samplealiquot (100 µL) was then removed and quenched by adding 200 µL of 0.1% formic acid inmethanol. The mixture was centrifuged again at 12000 rpm for 5 minutes. Clear supernatantwas then analyzed by analytical HPLC as described method. Calibration curves for prodrugsAttorney Docket No. 330272000240were generated by dissolving DMSO solution of test compounds in 0.1% formic acid inmethanol (concentrations at 200, 100, 50, 25, 12.5, and 6.25 µM) and then analyzed byHPLC. Calibration curves were used to quantitate the concentration of soluble testcompounds in the potassium phosphate buffer. Data represent the mean ± s.d. (n = 3independent replicates) and a representative HPLC trace is shown.Log D7.4 determination using shake-flask. An aqueous potassium phosphate buffer(10 mM, pH 7.4) solution has been prepared and then saturated with n-octanol. Likewise, n-octanol was saturated with the pH 7.4 potassium aqueous phosphate buffer. Both solutions have been heavily vortexed and then left resting to ensure complete separation of the two phases. The shake-flask experiments were carried out at room temperature. Once the phases have been prepared, 1 mL of 1-octanol and 1 mL of the aqueous potassium phosphate bufferare added to a glass vial. 20 µL of test compound stock solution (10 mM stock solution inDMSO; 100 µM final concentration in the pre-saturated mixture) is added and the vial is shaken for one hour at room temperature. After one hour, the layers were allowed to separate and aliquots (100 µL) of each of the n-octanol and aqueous buffer layers were processed byadding 200 µL of 0.1% formic acid in methanol. The mixture was centrifuged again at12,000 rpm for 5 minutes. Clear supernatant was then analyzed by analytical HPLC asdescribed method. Calibration curves were used to quantitate the concentration of testcompounds. Data represent the mean ± s.d. (n = 3 independent replicates).The following equation was used to calculate Log D7.4.&!'&(')*+),!' !- &! / 0!1'2 ,' !&)+'!30ℎ+5(!" #$.% = !"&!'&(')*+),!' !- &! / 0!1'2 ,' +61(!150ℎ+5(Example 2: Evaluation of Binding Affinities of Conjugates Evaluation of binding affinity of test compounds to TTR in buffer. The binding affinity of AG10-L, AG10-L-E2-COOH, AG10-L-E2-Naloxone, and AG10-L-E1-Naloxone to TTR in buffer was determined by their ability to displace FP probe from TTR using aFluorescence Polarization (FP) assay. Serial dilutions of compounds (0.010 µM to 20 µM)were added to a solution of FP-probe (50 nM) and TTR (300 nM) in assay buffer (PBS pH 7.4, 0.01% TritonX100, 1% DMSO in 25 μL final volumes) in a 384-well plate. The samples were allowed to equilibrate by agitation on a plate shaker for 20 minutes at room temperature. Fluorescence polarization (excitation λ 485 nm, emission λ 525 nm, cutoff λ 515 nm)Attorney Docket No. 330272000240measurements were taken using a SpectraMax M5 Microplate Reader (Molecular Devices). We used SoftMax® Pro software v5.4.1 (Molecular Devices, Inc.) to collect the fluorescence data. The IC50 values were obtained by fitting the data to the following equation [y = (A- D) / (1 + (x / C)^B) + D], where A = maximum FP signal, B = slope, C = apparent binding constant (Kapp), and D = minimum FP signal. The binding constant (Kd) values werecalculated using the Cheng–Prusoff equation from the IC50 values. Data represent the mean ±s.d. (n = 3 independent replicates).Evaluation of binding affinity and selectivity of test compounds to TTR inhuman Serum. The binding affinity and selectivity of AG10-L, AG10-L-E2-COOH, AG10-L-E2-Naloxone, and AG10-L-E1-Naloxone to TTR were determined by their ability tocompete with the binding of a fluorescent probe exclusion (FPE probe) binding to TTR inhuman serum. AG10 and Tafamidis were used as controls. An aliquot (98 μL) of humanserum was mixed with 1 μL of test compounds (1.0 mM stock solution in DMSO; 10 μM final concentration in serum) and 1 μL of FPE probe (0.36 mM stock solution in DMSO; 3.6 μM final concentration in serum). The fluorescence changes (λex = 328 nm and λem = 384 nm) were monitored every 15 min using a SpectraMax M5 microplate reader for 6 h at 25 °C.Data represent the mean ± s.d. (n = 4 independent replicates).Results: The binding affinity of prodrugs AG10-L-E1-Naloxone and AG10-L-E2-Naloxone were evaluated using fluorescence polarization (FP) binding assay (Kd= 394.3 nMand 258.8 nM) respectively; Fig. 1c). This binding affinity is similar to the binding affinity ofAG10-L and AG10-L-E2-COOH (Kd = 262.9 nM and 213 nM, respectively). We then evaluated the selectivity of prodrugs binding to TTR over > 4,000 other human serum proteins) using a well-established TTR serum fluorescent probe exclusion (FPE) selectivity assay. Our data showed that all test compounds maintained very good binding selectivity to TTR in human serum (~50 to 70% TTR occupancy) (Fig.3d,e). The performance of A AG10-L-E2-COOH 48.1% TTR occupancy) was similar to that of the TTR stabilizer, tafamidis (an approved drug for TTR amyloidosis; 49.2% TTR occupancy). Example 3: Stability Analysis Human and rat plasma stability assay of test compounds. Test compounds (5 μM)were incubated in human or rat plasma at 37°C. 100 μL plasma samples were analyzed at 0hr, 0.25 hr, 2 hr, 4 hr, and 24 hr. All the samples were processed by adding 200 μL ofquenching buffer (0.1% formic acid in methanol) followed by centrifuging at 15,000 rpm forAttorney Docket No. 3302720002405 minutes. The supernatant was kept in the -20°C freezer for 5 minutes and centrifuged again at 15,000 rpm for another 5 minutes. The supernatant was analyzed by analytical HPLC asdescribed method. Data represent the mean ± s.d. (n = 3 independent replicates).Results: We first evaluated the stability of the prodrugs in human plasma. AG10-L-E1-Naloxone was unstable (0% remaining after 1 min of serum incubation, Fig.1f), which fits with the instability of alkyl-based ester prodrugs. In contrast, the PABA-based esters (AG10-L-E2-Naloxone and C12-E2-Naloxone) were fully protected from hydrolysis in human plasma. While aryl-based esters are more stable than their alkyl counterparts, we were surprised by the full stability of these prodrugs in human plasma. Our modeling studies showed that the linker we used is long enough to extend the PABA ester of the TTR T4 binding pocket, which should in principle allow plasma esterase to target our prodrugs even if there are bound to TTR (Fig.2b). To investigate this observation, we evaluated the stability of the prodrugs in rat serum. As expected, the alkyl ester prodrug (AG10-L-E1-Naloxone)was hydrolyzed the fastest (0% remaining after 1 min of serum incubation) (Fig. 1g). Thestability was higher for the PABA ester, AG10-L-E2-Naloxone (60% remaining after 15 min and 3.8% remaining after 2 hr). The hydrolysis rate of C12-E2-Naloxone (34.2% remaining after 15 min and 0% remaining after 2 hr) was slightly faster than AG10-L1-E2-Naloxone. The disparity in prodrugs hydrolysis between human and rat plasma pointed to the carboxylesterase enzymes 1 and 2 (CES1 and CES2), which are present in rat plasma but absent in human plasma. Docking with TTR and CES2. In silico docking simulation of mouse Ces2c withAG10-L-E2-Nalxone was carried out using Dock6. Crystal structures of TTR (pdb id: 4HIQ)and Ces2c (pdb id: 8AXC) were obtained from RCSB.org protein data bank site. Thegeometry optimizations of AG10-L-E2-Nalxone were carried out at the B3LYP / 6-311G*level using Gaussian09. For Docking with TTR and Ces2c, AG10-L-E2-Nalxone was split into two, AG10-Linker and Naloxone-Linker. Geometry optimizations of both ligands with shorter linkers were carried out at the same B3LYP / 6-311G* level. Molden was used to analyze ligand geometries and to prepare ligand files for docking. UCSF Chimer program was for docking preparation of receptors and for analysis of docking results. AG10-LAand LB-E2-Nalxone are docked to TTR and Ces2c respectively. The docking complexes of TTR--- AG10-LA and Ces2c--- LB-E2-Nalxone are superimposed onto the optimized structure ofAG10-L-E2-Nalxone to see the possibility of forming a ternary complex of TTR- AG10-L-E2-Nalxone -Ces2c.Attorney Docket No. 330272000240 Example 4: Stability of Conjugates to Hydrolysis by Carboxylesterases Materials and Methods Metabolic Study of AG10-L-E2-Naloxone in recombinant humancarboxylesterases. The reaction mixture, consisting of CES1 (30 µg mL-1 or 100 µg mL-1) orCES2 (30 µg mL-1) in 50 mM potassium phosphate buffer was incubated for 5 min at 30oC.The reaction was initiated by adding AG10-L-E2-Naloxone at a final concentration of 5 µM(or DMSO as a negative control). After incubation, 100 μL samples from the reaction mixturewere quenched at 0 hr and 1 hr by adding 100 μL of quenching buffer (0.1% formic acid inmethanol) to the samples to terminate the reaction at each designated time point. Samples were then centrifuged at 12,000 rpm for 5 minutes at 4oC. Supernatants (150 μL) were further diluted by adding 75 μL of 0.1 % formic acid in water. Samples were stored at −20°C untilanalysis by HPLC as described above. Data represent the mean ± s.d. (n = 3 independentreplicates). Microsomal stability assay. 2 µL of AG10-L-E2-Naloxone Stock (1 mM in DMSO)were added to microcentrifuge tubes containing 3.2 µL acetonitrile and 194.8 µL potassiumphosphate buffer (50 mM, pH 7.4, containing 3 mM MgCl2). The assay tubes werepreincubated at 37°C for 10 min before liver microsomes addition. Human, monkey, or ratliver microsomes and NADPH regeneration solution (NADP, glucose-6-phosphate, andglucose-6-phosphate dehydrogenase; concentration of 2 mg mL-1 and 2 mM, 10 mM, and 2Unit mL-1, respectively) were added to potassium phosphate buffer (water replaced NADPHin negative control). The reaction mixtures were pre-warmed at 37°C for 10 min. TheNADPH was generated using the rapidSTART NADPH regenerating system (Xenotech), by adding 0.7 mL of high purity water to the frozen components in the RapidStart vial,vortexing, and then adding the activated RapidStart solution to the incubation. 200 µL of thisNADPH regeneration solution were added to each pre-incubated assay tube alreadycontaining 200 µL AG10-L-E2-Naloxone in phosphate buffer. The final reaction concentrations for AG10-L-E2-Naloxone, microsomes, NADP, glucose-6-phosphate, andAttorney Docket No. 330272000240glucose-6-phosphate dehydrogenase are 5 µM, 1 mg mL-1, 1 mM, 5 mM, and 1 Unit mL-1,respectively. The vials were incubated at 37°C. At 0 hr and 1 hr, 100 µL aliquots were takenand the microsomal reaction was terminated by addition of 100 µL of quenching buffer (0.1%formic acid in methanol containing 15 ng mL-1 Naloxone-D5 as the internal standard).Samples were centrifuged at 12,000 rpm for 5 min and supernatants (150 µL) were furtherdiluted by adding 75 µL of 0.1 % formic acid in water. Samples were stored at −20°C untilanalysis using validated LC-MS / MS method using Triple Quadrupole mass spectrometer(QQQ). Data represent the mean ± s.d. (n = 3 independent replicates).Microsomal stability assay with Loperamide, or Digitonin. The microsomal assay described above was also performed in HLMs in presence of Loperamide or Digitonin (final concentration 100 µM). Loperamide or Digitonin were added to the microsomal buffer before addition into the test compound. Rat plasma stability assay of AG10-L-E2-Naloxone in presence of CESinhibitors. Rat plasma was pre-incubated with either of CES2 inhibitor, loperamide (100µM), and CES1 inhibitor, digitonin (100 µM), or DMSO (negative control) for 5 minutes atroom temperature. After that, AG10-L-E2-Naloxone (5 μM) was added to the incubationmixtures. Samples were assayed at 0 hr, 0.5 hr, and 1 hr. All the samples were processed byadding 200 μL of quenching buffer (0.1% formic acid in methanol) followed by centrifugingat 15,000 rpm for 5 minutes. The supernatant was kept in the -20°C freezer for 5 minutes and centrifuged again at 15,000 rpm for another 5 min. The supernatant was analyzed byanalytical HPLC as described method. Data represent the mean ± s.d. (n = 3 independentreplicates). Monkey and rabbit plasma stability assay of AG10-L-E2-Naloxone. AG10-L-E2- Naloxone (5 μM) was incubated in monkey or rabbit plasma at 37°C.100 μL samples were analyzed at 0 hr and 24 hr. All the samples were processed by adding 200 μL of quenching buffer (0.1% formic acid in methanol) followed by centrifuging at 15,000 rpm for 5 minutes. The supernatant was kept in the -20°C freezer for 5 minutes and centrifuged again at 15,000 rpm for another 5 min. The supernatant was analyzed by analytical HPLC as describedmethod. Data represent the mean ± s.d. (n = 3 independent replicates).Results Carboxylesterase (CES) enzymes play a critical role in the hydrolytic inactivation ofmany clinically used ester drug and in the bioactivation of prodrugs. CES1 and CES2 are thetwo most significant forms of CESs in humans. Human CES1 plays a major role inbioactivation of many prodrugs, while CES2 plays a minor role. There is a marked speciesAttorney Docket No. 330272000240differences in the tissue distribution and catalytic activity of CESs, making human translationchallenging. CES1 is highly expressed in the liver, while CES2 is mainly found in the smallintestine, but also present in the colon, kidney, and liver (10-15 times lower protein levelsthan CES1). We investigated the potential of CES1 / CES2 role in the bioactivation of AG10-L-E2- Naloxone. C12-E2-Naloxone was insoluble in buffer (Fig.1b) which prohibited us from evaluating its CES selectivity. Our in vitro data with purified humans CESs clearly showed that AG10-L-E2-Naloxone is a specific substrate for CES2 (Fig.2c). The CES2 specificity for AG10-L-E2-Naloxone was very surprising since only a few prodrugs (e.g., procaine and irinotecan) are selectively bioactivated by CES2 (they are also bioactivated by CES1 and other plasma proteins). For example, in addition to liver CES2, procaine undergoes rapidhydrolysis by butyrylcholinesterase in human plasma. In contrast, the bioactivation ofirinotecan by CES2 is very slow (less than 2% of the dose is bioactivated by CES2). To further investigate the CES2 specificity and evaluate the potential translation to humans, we evaluated the metabolic bioactivation of AG10-L-E2-Naloxone in liver microsomes from human, rat, and monkey (Fig.2d). Human liver microsomes (HLM) effectively produced naloxone from AG10-L-E2-Naloxone. The selective CES2 inhibitor, loperamide, significantly decreased the amount of naloxone released while there was no effect of the CES1 inhibitor, digitonin. The amount of naloxone released from AG10-L-E2-Naloxone in the rat liver microsomes (RLM) was lower than that form HLM, mainly due to higher metabolism (de-alkylation by CYP) of naloxone released by RLM compared to HLM. The expression of CES enzymes in monkey and human is similar and therefore we evaluated the bioactivation of AG10-L-E2-Naloxone in monkey liver microsomes (MLM). The amount of naloxone released MLM was similar to HLM, suggesting that monkey could be a reasonable animal model evaluating AG10-L-E2-Naloxone. The specificity of CES2 for bioactivation of AG10-L-E2-Naloxone was also confirmed by performing the rat plasma stability with CES1 and CES2 inhibitors (Fig.2e). We also confirmed our results by evaluating the stability of AG10-L-E2-Naloxone in monkey plasma (no CES1 or CES2 in plasma; 100% stability after 24 hr) and rabbit plasma (high abundance of CES1 and CES2 in plasma; 0% remaining after 24 hr). While the crystal structure of human CES1 is available, the first crystal structure for aCES2 form mouse was recently reported as a potential ortholog of human CES2. The overallstructure of mouse CES2 resembles that of the human CES1 with differences in the access to the active site. We performed a docking study of AG10-L-E2-Naloxone with both humanAttorney Docket No. 330272000240CES1 and mouse CES2. There was no binding for AG10-L-E2-Naloxone in CES1. In contrast, AG10-L-E2-Naloxone fits very well in the active site of CES2 and the nucleophilic Serine (S230) is in close proximity to the carbonyl of the ester groups in AG10-L-E2- Naloxone (Fig.2b). This data represent the first docking experiment of a specific CES2 substrate with a CES2 enzyme. Insights form the binding mode and selectivity of CES2 for AG10-L-E2-Naloxone represent could be helpful in designing additional CES2 specific prodrugs. The lower concentration of liver CES2 in comparison to CES1 provides a unique CES2 bioactivation for AG10-L-E2-Naloxone. This could be advantageous to our controlled slow and continuous release of naloxone from AG10-L-E2-Naloxone (discussed below in the Example 10 monkey study). Example 5: Subcutaneous administration of AG10-L-E2-Naloxone to rats releasesnaloxone in an extended and controlled manner without spikes in plasma and brainconcentrationMaterials and MethodsEvaluation of subcutaneous and intravenous pharmacokinetic profile of AG10-L-E2-Naloxone and Naloxone in rats. Jugular vein cannulated male Sprague Dawley rats(225–250 g; 7-8 weeks old) from Charles River were used for both subcutaneous (s.c) and intravenous (i.v) pharmacokinetic (PK) studies. For the i.v pk study, each animal received one i.v bolus dose of either naloxone, or AG10-L-E2-Naloxone (60 µmol kg-1; equivalent to 20 mg kg-1naloxone) in 500 µL dosing solution (10% DMSO, 20% PEG, 70% H2O) followed by an injection of 200 µL sterile saline to flush the jugular vein cannula (n = 3 rats per group).200 µL blood samples were collected from each rat, via jugular vein cannula, in heparinized tubes at predetermined time points (0.033,0.25, 0.5, 1, 2, 4, 6, 8, 12, and 24 hr postdosing), and the volume was replaced with sterile normal saline. For the s.c pk study, 500 µL dosing solution (per 250 g rat) in the scruff area was administered of either naloxone 15 µmol kg-1or 60 µmol kg-1, AG10-L-E2-Naloxone 15 µmol kg-1or 60 µmol kg-1. In each of the four groups (n = 3 rats per group), blood samples were collected from each rat via jugular vein cannula, in heparinized tubes at predetermined time points (0.033, 0.25, 0.5, 1, 2, 4, 6, 8, 12, 24, 48, 72 and 96 h postdosing), and the same volume was replaced with sterile normal saline. The plasma samples were prepared directly after collection of blood by centrifugation at 1,500 g for 10 min at 4°C. Next, an aliquot of 50 µL plasma sample was precipitated with 2 volumes of extraction buffer (0.1% formic acid in methanol containing with 15 ng / mLnaloxone-D5). Samples were vortexed for 30 sec, and then kept at -20°C for 5 min. Then, theAttorney Docket No. 330272000240samples were centrifuged at 15,000 rpm for 5 min; the supernatant was collected and kept in the -20°C freezer for 5 min and centrifuged again at 15,000 rpm for another 5 min. The samples were analyzed on the same day of study using LC–MS / MS method using Triple Quadrupole mass spectrometer (QQQ) to quantitate the concentration of naloxone and AG10- L-E2-Naloxone in all groups. Sample preparation and LC-MS / MS analysis of the experimental compounds.Sample preparation. Stock solutions of naloxone (20 mM), and AG10-L-E2-Naloxone (10mM) were prepared in DMSO solution. The working solutions were prepared by serial dilution of the DMSO solution mentioned above. The calibration curve standards were prepared by spiking aliquots (1 µL) of each working solution to 49 µL blank rat plasma. Quality control (QC) samples prepared at low, medium, and high concentrations were extracted at the same time with the animal samples. An aliquot of 50 µL plasma was precipitated with 2 volumes of extraction buffer (0.1% formic acid in methanol containing with 15 ng mL-1naloxone-D5). The corresponding double blank samples were extracted with the extraction buffer without the internal standard i.e., 0.1% formic acid in methanol. The samples were processed same way described above. For the quantification of naloxone, 20 µL of samples were injected for LC-MS / MS analysis. A triple quadrupole mass spectrometer (QQQ) was used to quantitate the analytes in the plasma samples. The mobile phase was composed of solvent A (0.1% formic acid in water containing 0.5 mM ammonium formate.) and solvent B (0.1% formic acid in methanol), at a flow rate of 0.5 mL min-1. LC-MS / MSanalysis was performed on a WatersTM XBridge C18 (4.6x150 mm, 5 µm). The turbo sprayion source was set in the positive ionization mode. Fragmentation pattern and peak areas were used to identify and quantitate the test compounds, respectively. LC-MS / MS data were collected from Agilent masshunter software. Naloxone-D5 was used as the internal standard. The gas flow, nebulizer, sheath gas temperature, sheath gas flow, capillary voltage, nozzle voltage and gas temperature were set as 7 l / min, 30 psi, 250ºC, 12 l / min, 3500 V, 500 V and 300ºC. LC-MS / MS analysis was performed using a gradient method increasing linearly from 0-100% solvent B in 0-3 min, stayed at 100% solvent B for 5.5 min, then went down from 100-0% solvent B in 0.5 min and finally stayed at 0% solvent B for 1 min. The retention time for naloxone and naloxone-D5was 4.62 and 4.62 min respectively. The total run was 7 min. Based on the calibration curves for naloxone in plasma and the internal standard generated bythe LC−MS / MS analyst, mean ± s.d. concentrations of naloxone were determined. Sampleswere diluted when the concentration of the samples was outside the calibration curve range. The detailed mass spectrometer conditions for multiple reaction monitoring (MRM) of eachAttorney Docket No. 330272000240compound are listed in the Table below. The lower limit of quantitation (LLOQ) of naloxone was 1 nM. The linear ranges were calculated based on the regression analysis between theanalyte and internal standard peak area ratio and the analyte concentration. The accuracy wasbetween 80% and 120% in every case. Evaluation of the brain uptake of AG10-L-E2-Naloxone and Naloxone in rats. Jugular vein cannulated male Sprague Dawley rats were used for this study. Animals wererandomized in four treatment groups (n = 3 animals per group). Each animal received one s.c15 µmol kg-1dose of naloxone or AG10-L-E2-Naloxone, in 500 µL dosing solution (10% DMSO, 20% PEG400 and 70% sterile deionized water).10 and 30 min after the dosing, the rats were anesthetized with an intraperitoneal injection of 90 mg kg-1ketamine and 9 mg kg-1xylazine. The CSF samples were collected from the cisterna magna with a 22-gauge needle. The blood was collected from the aortic exsanguination with a 20-gauge needle followed by decapitation and brain collection. Sample preparation and LC-MS / MS analysis of theexperimental compounds. Sample preparation. The brain was immediately snapped frozen inthe liquid nitrogen. Plasma samples were processed and analyzed the same way as plasma samples described in the pharmacokinetic study. The CSF and brain samples were stored at - 80 °C for further analysis. Stock solutions of naloxone (20 mM), and AG10-E2-Naloxone (10 mM) were prepared in DMSO solution. The working solutions were prepared by serial dilution of the DMSO solution mentioned above. The calibration curve standards were prepared by spiking aliquots (1 µL) of each working solution to 49 µL artificial CSF (125 mM NaCl, 2.5 mM KCl, 1.26 mM CaCl2, and 1.18 mM MgCl2), or blank rat brain homogenate. Quality control (QC) samples prepared at low, medium, and high concentrations were extracted at the same time with the animal samples. Brain homogenate was prepared byhomogenizing the brain tissue with 2 volumes (w:v) of homogenizing solution (PBS buffer).An aliquot of 50 µL brain homogenate, or CSF sample was precipitated 2 volumes ofAttorney Docket No. 330272000240extraction buffer (methanol-water (95:5, v / v) containing 0.1% formic acid with 15 ng mL-1naloxone-D5). The corresponding double blank samples were extracted with the extraction buffer without the internal standard i.e., methanol-water (95:5, v / v) containing 0.1% formicacid. The CSF and brain homogenate samples were vortexed for 30 seconds, and then kept at-20°C for 5 minutes. Then, the samples were centrifuged at 15,000 rpm for 5 minutes; the supernatant was collected and kept in the -20°C freezer for 5 min and centrifuged again at 15,000 rpm for another 5 min. The samples were stored in -80°C for further analysis. LC- MS / MS analysis was also performed as described for the pharmacokinetic study of these molecules. The LLOQ of naloxone and AG10-L-E2-Naloxone in brain and CSF matrices is 1 nM. The ratio of the brain (ng g-1) versus plasma concentration (ng mL-1) is expressed as the percentage brain to plasma ratio. The ratio of the CSF (ng mL-1) versus plasma concentration (ng mL-1) is expressed as the percentage CSF to plasma ratio. Survival of rats after LD50 doses of Fentanyl or Morphine. Male Sprague Dawleyrats (225–250 g; 7-8 weeks old) were obtained from Charles River Laboratories. Rats wererandomly assigned to three groups (vehicle, naloxone, and AG10-L-E2-Naloxone). Rats firstreceived a s.c. dose of 100 mg kg-1 of morphine (n = 9 per group). After 5 min of morphinedose, rats were administered a single s.c. dose of vehicle (10% DMSO, 20% PEG400, and70% H2O), naloxone (15 µmol kg-1, equivalent to 5 mg kg-1), or AG10-L-E2-Naloxone (15µmol kg-1, equivalent to 15.8 mg kg-1). Naloxone and AG10-L-E2-Naloxone were dissolvedin the same vehicle dosing solution. Morphine was dissolved in water. Volume of injections for morphine and antagonists were 200 and 500 µL, respectively. Rats were then put back into their cages under routine conditions. The number of rats that died and their approximate time of death was recorded. After 6 hr of the first morphine dose, all rats that survivedreceived a second s.c. dose of 50 mg kg-1 morphine. Rats were placed back into their cagesand observed to record any death. The total number of rats that died was recorded and survival rate was calculated in each group. For the fentanyl mortality study, rats first received a s.c. dose 3 mg kg-1of fentanyl (n= 8 per group). After 5 min of fentanyl dose, rats were administered a single s.c. dose ofvehicle (10% DMSO, 20% PEG400, and 70% H2O), naloxone (15 µmol kg-1, equivalent to 5mg kg-1), or AG10-L-E2-Naloxone (15 µmol kg-1, equivalent to 15.8 mg kg-1). Naloxone andAG10-L-E2-Naloxone were dissolved in the same vehicle dosing solution. Fentanyl wasdissolved in water. Volume of injections for fentanyl and antagonists were 200 µL and 500µL, respectively. Rats were then put back into their cages under routine conditions. The number of rats that died and their approximate time of death was recorded. After 6 hr of theAttorney Docket No. 330272000240first morphine dose, all rats that survived received a second s.c. dose of 3 mg kg-1fentanyl. Rats were placed back into their cages and observed to record any death. The total number of rats that died was recorded and survival rate was calculated in each group. Reversal and prevention of fentanyl induced respiratory depression in rats. Theefficacy of antagonists to reverse fentanyl induced respiratory depression in rats was evaluated using whole body plethysmography apparatus from DSI Buxco (St. Paul, MN; withFinePointe software). Sprague-Dawley rats (225– 250 g; 7-8 weeks old) (n = 6 per group)were habituated for 30 min to the plethysmography chambers located inside sound- attenuating closed room under a continuous flow of fresh air (2.2 l / min). Rats were awake and free moving in the testing chamber and during the monitoring period. For baseline measurements, rat respiration was recorded for 20 min prior to injections. Rats were then removed from the chambers and sequentially treated with fentanyl (3 mg kg-1, single s.c. or i.v. dose) followed by a single s.c. or i.v. dose of antagonist one min later (15 µmol kg-1or 60 µmol kg-1). Rats were placed back in the chambers and the respiratory parameters were measured for 90 min. Rats were challenged with two additional s.c. or i.v. doses of fentanyl (1.5 mg kg-1each) at 6 hr and 24 hr post antagonist dosing. The respiratory parameters were measured for 90 min after each fentanyl injection. Rat ventilation was measured by recording changes in chamber pressure which is then processed and digitized. For each rat, the software calculated the average Tidal Volume (VT: milliliter per breath), Ventilatory Frequency (f: breaths per minute), and Minute Volume (VE= VT* f: milliliter per minute). Since it is the product of VT and f, Minute Volume was reported as it considered a quantifiable net physiological average that is scientifically relevant. Each rat’s baseline Minute Volume data were averaged and specified as 100% of baseline values. Minute Volume readings afterdosing were then normalized and reported for each rat in 5 min intervals based on thefollowing equation: Minute Volume (% of control baseline) = Minute Volume at specific time / Minute Volume baseline * 100. For the prophylactic administration of antagonist to counter fentanyl inducedrespiratory depression: rats (n = 6 per group) were habituated for 30 min to theplethysmography chambers, and the baseline measurements were recorded as described above. Rats received a single s.c. dose vehicle, naloxone (15 µmol kg-1and 60 µmol kg-1), or AG10-L-E2-Naloxone (60 µmol kg-1) and the respiratory parameters were measured for 90 min. After 6 hr, rats were challenged with single s.c. doses of fentanyl (1.5 mg kg-1) and were placed back in the plethysmography chambers. The respiratory parameters were measured for 90 min and the data were processed and reported as described above. The treatment doses forAttorney Docket No. 330272000240morphine and fentanyl were determined in preliminary studies and were also based on published literature. The dose of morphine used (100 mg kg-1) is within the reported LD50 of 64–140 mg kg-1for morphine in rats. For fentanyl, we used the reported value of 3 mg kg-1. These doses were confirmed in preliminary experiments where we started with lower doses of morphine and fentanyl without observing any lethality. The overdose studies with morphine and fentanyl were approved by the University of the Pacific’s IACUC. Preliminary evaluation of AG10-L-E2-Naloxone toxicity in rats. The in vivotoxicity of AG10-L-E2-Naloxone was evaluated in rats. Adult male Sprague-Dawley rats (Charles River), body weight ranging 225-250 g, were used for the study. Three groups of rats were used. Group one was treated with a 500 µL of vehicle (10% DMSO, 20% PEG and 70% H2O). Group two was treated with AG10-L-E2-Naloxone (60 µmol kg-1; s.c. dose) dissolved in 500 µL of vehicle. Group three was treated with fentanyl (3 mg kg-1; s.c. dose) followed by AG10-L-E2-Naloxone (60 µmol kg-1) and then two doses of fentanyl (1.5 mg kg-1; each s.c. dose) at 6 hr and 24 hr. The animal weights were monitored weekly for fourweeks. Body weigh represent mean ± s.d. (n= 6 biological replicates per group).Results AG10-L1-E2-Naloxone prevented mortality in rats after two doses of morphine or fentanyl We evaluated the pharmacokinetic (PK) properties of naloxone and AG10-L-E2- Naloxone in rats (Fig.3a). Both compounds (15 µmol kg-1equivalent to a naloxone dose of 5mg kg-1) were administered as single s.c. doses to rats and blood samples were withdrawnfrom a jugular vein cannula at pre-determined time points (ranging from 5 min to 72 hr) (Fig. 3a). Consistent with our hypothesis, the PK profiles of AG10-L-E2-Naloxone was markedlydifferent than naloxone. Both compounds were absorbed rapidly (naloxone was detected inplasma after 2 min of dosing free naloxone or AG10-L-E2-Naloxone) and Tmax was ~15 min. The Cmaxfor freely administered naloxone (1360 nM) was significantly higher than Cmaxfor naloxone released from AG10-L-E2-Naloxone (16.9 ± 2.1nM). However, while there was no measurable amount of free naloxone 4 hr after dosing, AG10-L-E2-Naloxone and its released naloxone were still present even after 72 hr (Fig.3a). The PK profile of naloxone displayed the typical spike profile (ranging from Cmax~1360 nM at 15 min to Cminof 34 nM at 4 hr). Strikingly, the release of naloxone from AG10-L-E2-Naloxone followed a flatter profile (ranging from Cmax ~17 nM at 15 min to Cmin of 2.4 nM at 72 hr), which we believe will be advantageous over the early concentration spike observed for naloxone (potentially causing withdrawal symptoms). Importantly, human data show that the Cmax for naloxone (3.5 nM forAttorney Docket No. 3302720002402 mg dose and 17 nM for 5 mg does dose check IM or SC dose) after s.c. dosing is ~10 nM. To our knowledge, this is the first example of PK profile that displayed this flat steady release of therapeutic molecule without the presence or burst effect or typical peaks and toughs observed with multiple doing. This data strongly support and validate our novel approach in which hydrophilicity of our prodrugs controls the release of these molecules from the subcutaneous tissue. This slow release in combination to TTR binding resulted a slow and steady plasma concentration of released of naloxone in rats. We then evaluated the blood–brain barrier (BBB) penetration for AG10-L-E2- Naloxone (5 mg / kg; s.c.) in rats (Fig.3b). The concentrations of naloxone released from AG10-L1-E2-Naloxone in brain (7.8 nM and 30.1 nM after 10 min and 30 min, respectively) were ~30 to 60-fold lower (after 10 min and 30 min, respectively) than those of freely administered naloxone (236.3 nM and 1721.7 nM after 10 min and 30 min, respectively). Similar data for both compounds were observed in the cerebrospinal fluid (CSF) (Fig.3c). This clearly shows that AG10-L1-E2-Naloxone releases a significant amount of naloxone that crosses the BBB. There was no detectable concentration of the parent AG10-L1-E2- Naloxone in the brain or CSF. These data support our hypothesis that the hydrophilicity and selective binding to TTR limit the ability of the AG10-conjugates to cross the BBB.. The percentage brain to plasma ratio for naloxone released from AG10-L1-E2-Naloxone (250.3%after 30 min,) and the CSF to plasma ratio (173.3% after 30 min) were very similar to that offreely administered naloxone. This is significantly higher than 2% (cut-off for BBB penetration; it is well established that molecules having < 2% of its plasma concentration in the brain or CSF are not considered to cross the BBB). We evaluated the potential of our prodrugs as antidotes for rescue against mortality by opioid overdose. Two opioid, morphine and fentanyl were evaluated. While the half-life (t1 / 2) of fentanyl (~7 hr) and morphine (2 to 3 hr) are relatively short, the duration of overdose could last for up to 24 hr for fentanyl and 120 hr for morphine (depending on the opioid dose that is often unknown). The treatment doses for morphine and fentanyl were determined in preliminary studies and were also based on published literature. The dose for morphine (100 mg kg-1) is within the reported LD50of 64–140 mg kg-1for morphine in rats. For fentanyl, weused the reported value of 3 mg kg-1. Three groups of rats (n= 9 per group) were dosed withmorphine (100 mg kg-1; single s.c. dose). after 5 min: group 1 was dosed with vehicle; group2 was dosed with naloxone (15 µmol kg-1, equivalent to 5 mg kg-1; single s.c. dose), andgroup 3 was dosed with molar equivalent dose of AG10-L-E2-Naloxone (15 µmol kg-1, equivalent to 15.8 mg kg-1; single s.c. dose). The 15 µmol kg-1doses for naloxone and AG10-Attorney Docket No. 330272000240L-E2-Naloxone chosen is higher than what has been used in the literature (1 mg kg-1, equivalent to 3 µmol kg-1;) to make sure that the respiratory depression of the morphine and fentanyl dose is almost completely reversed by the slower release of naloxone from our prodrugs. All control groups dosed with vehicle died after the first morphine dose, while naloxone and AG10-L-E2-Naloxone groups remained alive (Fig.3d). After 6 hr, a seconddose of morphine (50 mg kg-1; single s.c. dose) was administered to the naloxone and AG10-L-E2-Naloxone treated animals to mimic re-narcotization. All of the naloxone group was dead within 2 hr after the second morphine dose. Remarkably, all the AG10-L1-E2-Naloxone group were alive and remained alive for a few weeks after dosing. We also performed a similar experiment by challenging rats with two doses offentanyl (3 mg kg-1 each, s.c., at time = 0 hr and 6 hr; n = 8 per group) (Fig. 3e). Six rats inthe vehicle group died after the first fentanyl does and the remaining rats died after the second dose. In the naloxone groups, all 8 rats died after the second doss of fentanyl. Importantly, only one rat out of eight died in the AG10-L-E2-Naloxone treated group after the second dose of fentanyl (Fig.3e). The data clearly demonstrate the higher efficacy ofAG10-L1-E2-Naloxone vs. naloxone in lowering mortality in rats administered with two highfentanyl doses. Due to the urgent need to develop effective antidotes against fentanyl, the following studies will focus on evaluating our prodrugs against fentanyl overdose. Reversal of opioid-induced respiratory depression (OIRD) in rats Systemic side effects of opioid toxicity include life-threatening OIRD that can result in a potentially deadly outcome for the patient. OIRD is also a main obstacle for the safe administration of morphine for acute pain after injury or trauma during emergencies. OIRDcan be managed appropriately when monitored by trained medical personnel and whenappropriate equipment is available. However, this is difficult in emergency situations where these options are not available (e.g., battlefield environment or weaponized synthetic opioids). Although tolerance to respiratory depression develops with chronic dosing, its potential for mortality in opioid-naïve patients means that it is the side effect most feared by clinicians in post-surgical settings. We tested the ability of our prodrugs (15 µmol kg-1which is equivalent to 5 mg kg-1of naloxone; single s.c. dose, n = 6) to reverse the OIRD of highdose of fentanyl (LD50 of 3 mg kg-1; single s.c. dose) using non-invasive whole-bodyplethysmography (Figs.3f-i). After the first fentanyl dose (Fig.3g), no reversal of OIRD was observed with s.c. dosing of vehicle or the lipidated naloxone prodrug containing the PABA ester, C12-E2- Naloxone (despite hydrolysis in rat serum; Fig.1g). This is predicted since lipidation slowsAttorney Docket No. 330272000240the release of conjugates from s.c. tissue. We also had difficulty formulating C12-E2- Naloxone in the dosing vehicle, necessitating doubling the volume of the dosing vehicle. Two out of six rats in each of the vehicle and C12-E2-Naloxone treatment groups died after the first fentanyl dose, and therefore we did not proceed with testing the C12-E2-Naloxone prodrug. As expected, naloxone and the alkyl ester AG10-L-E1-Naloxone provided rapid reversal of OIRD after 10 min (demonstrated by rapid recovery in the Minute Volume; Fig. 3g). For AG10-L-E2-Naloxone, there was a gradual recovery in the Minute Volume of rats post dosing, but the Minute Volume did not reach levels close to those of normal rats (Minute Volume at 90 min was 52.5 ± 4.5% of control). To test the ability of prodrugs to prevent fentanyl-induced ventilatory depression after the initial reversal (i.e., analogous to re-narcotization), rats were challenged with a second dose of fentanyl (1.5 mg kg-1; single s.c. dose) 6 hr after dosing of naloxone or prodrugs (Fig. 3h). As expected, naloxone was not effective in reversing OIRD and four out of six rats in the naloxone group died after the second fentanyl dose. AG10-L-E1-Naloxone was also not effective (confirmed above by rat serum stability showing rapid hydrolysis of the alkyl ester; Fig.1g). AG10-L-E2-Naloxone was the only prodrug that displayed significant reversal of OIRD after the second dose of fentanyl at 6 hr (Fig.3h). After 24 hr of dosing of naloxone or prodrugs, rats were challenged with a third dose of fentanyl (1.5 mg kg-1; single s.c. dose). The higher efficacy of AG10-L-E2-Naloxone in preventing mortality and reversing OIRD was again demonstrated over naloxone and AG10-L-E1-Naloxone (one out of six rats in theAG10-L-E1-Naloxone group died after the third fentanyl dose) (Fig. 3i). The slow onset ofefficacy for AG10-L-E2-Naloxone suggested that the initial concentration of released naloxone from the prodrug needs to be enhanced to obtain effective rescue from the first fentanyl dose. However, this slow-release profile might be helpful in certain therapeutic application such as treating recovering form analgesia and neonates (discussed below) Example 6: AG10-L1-E2-Naloxone is more effective than naloxone and nalmefene in preventing re-narcotization by fentanyl Our data showed that low dose of AG10-L-E2-Naloxone was effective in reducing mortality after two doses of fentanyl (3 mg kg-1each dose). However, the plethysmography results (Fig.3g) suggested the need to increase the initial concentration of released naloxone. Therefore, we evaluated the pharmacokinetic profile of a higher dose of AG10-L-E2- Naloxone (4-fold higher; 60 µmol kg-1; equivalent to 63 mg kg-1) (Fig.4a). For this very high dose, the Cmaxfor freely administered naloxone (6498 ± 2.15 nM) was significantly higherAttorney Docket No. 330272000240than Cmax for naloxone released from AG10-L-E2-Naloxone (~30 nM, Fig.4a). In contrast to naloxone, and as observed for the lower dose, the release of naloxone from AG10-L-E2- Naloxone followed a similar flatter profile (ranging from Cmax~30 nM at 30 min to Cminof 15 nM at 96 hr). (very nice 96 hr to support monkey). We then tested the efficacy of AG10- L-E2-Naloxone at the higher dose (60 µmol kg-1; equivalent to 63 mg kg-1) (Figs.4b-e). Wealso included a very high dose of the two FDA-approved antidotes, naloxone (60 µmol kg-1;equivalent to 20 mg kg-1) and nalmefene (60 µmol kg-1; equivalent to 21 mg kg-1) as controls. After the first fentanyl dose, nalmefene was effective in reversing OIRD within 2 min of dosing (fits well with reported rapid absorption; Tmax~20 min) (Fig.4c). However, there was significant hyperventilation and some convulsion or seizure in rats dosed with nalmefene, which indicate the precipitation of opioid withdrawal symptoms.3 rats in the fentanyl control died. The efficacy of higher dose of AG10-L-E2-Naloxone (60 µmol kg-1, reversal within 20 min) was better than that for lower dose (15 µmol kg-1reversal within 50 min) (Fig.4c). After challenging the rats with a second fentanyl dose, nalmefene and AG10-L-E2-Naloxone were equally effective in reversing OIRD, which demonstrates the presence of effective levels of released naloxone after 6 hr of dosing AG10-L-E2-Naloxone (Fig.4d). The naloxone control was not effective in reversing OIRD after administering the second fentanyl dose (i.e., 6 hr after naloxone dosing; 2 rats in the naloxone control groups died). We then challenged the rats with a third dose of fentanyl after 24 hr of dosing the antagonist (to mimic re- narcotization) (Fig.4e). Remarkably, while nalmefene was not effective in reversing fentanyl-induced OIRD, AG10-L-E2-Naloxone effectively counteracted OIRD. This data demonstrate that we developed what we believe as the longest acting mu-opioid antagonist prodrug (could be effective as a reversal agent and potentially an ideal prophylactic agent). Example 7: High dose of naloxone does not provide additional efficacy vs lower dose The lack of correlation between the pharmacokinetics and pharmacodynamics profile of naloxone was surprising. Pharmacokinetics data show that there is a significant plasmaconcentration of free naloxone at 6 hr (25 nM), which is similar to that of naloxone releasedform AG10-L-E2-Naloxone (21 nM) (Fig.4a). However, rats treated with naloxone did not perform well in plethysmography experiments after the second fentanyl dose and two ratsdied despite the presence of sufficient naloxone in circulation (Fig 4a and 4d). This datasuggest that, in comparison to the low and sustained levels for naloxone from AG10-L-E2- Naloxone (Conc. at 15 min = 20 nM), the initial very high levels of naloxone (conc. at 15 minAttorney Docket No. 330272000240= 6498 nM) could indeed be harmful and may make the animals more vulnerable to the toxicity of the second fentanyl dose. To investigate this, we performed another experiment where both fentanyl and antagonist (naloxone and AG10-L-E2-Naloxone) were administered intravenously (60 µmolkg-1; equivalent to 20 mg kg-1, single i.v. dose) (Fig. 4f). Pharmacokinetics data show thatboth naloxone (conc. at 15 min = 20597 nM) and naloxone and AG10-L-E2-Naloxone (conc. at 15 min = 1599 nM) are very high at early timepoints after dosing. While both treatmentgroups reversed OIRD after the first fentanyl dose, there was significant hyperventilation inthe naloxone treated rats and the animals experienced severe convulsions / seizures. No hyperventilation or seizures was observed for the AG10-L-E2-Naloxone treated animals. Thepharmacokinetics data show that there is a significantly high plasma concentration for bothfree naloxone and naloxone released from AG10-L-E2-Naloxone at 6 hr (750 nM and 60 nM, respectively) and at 24 hr (395 nM and 44 nM, respectively) (Fig.4f). However, while AG10-L-E2-Naloxone was mildly active after the second fentanyl dose, neither treatment groups showed effective protection against OIRD after the second (6 hr) and third (24 hr) doses of fentanyl (Figs.4g-i). This data indicated that exposing rats to a very high doses of naloxone after fentanyl dosing might indeed cause some initial harm to the animals or cause changes in the mu / other receptors that make the animals less protected by naloxone at later timepoints. There were reports of pulmonary edema after high / rapid reversal. However, this warrants further investigation. Example 8: AG10-L1-E2-Naloxone is a potential preventive and prophylactic agent against fentanyl induced mortality and OIRD To compensate for the lower efficacy of AG10-L-E2-Naloxone in the first 30 min after dosing, we tested the feasibility of combining the prodrug with a small amount of free naloxone. A single s.c. dose combination of AG10-L-E2-Naloxone (60 µmol kg-1; equivalent to 63 mg kg-1) and naloxone (3 µmol kg-1; equivalent to 1 mg kg-1) resulted in excellent efficacy data with full reversals of OIRD after all three fentanyl doses (Figs.5a-d). Importantly, no rats experience severe hyperventilation or convulsion / seizure indicating low risk for AG10-L-E2-Naloxone to develop opioid-induced withdrawal symptoms. We finally explored the potential of using AG10-L-E2-Naloxone as a prophylactic agent against fentanyl (Figs.5e-g). Rats (n = 6 per treatment group) were first dosed with AG10-L-E2-Naloxone (60 µmol kg-1) or naloxone (15 µmol kg-1and 60 µmol kg-1). There was not change in the Minute Volume compared to vehicle treated animals. After 6 hr, theAttorney Docket No. 330272000240rats were challenged with a single dose of fentanyl (1.5 mg kg-1; s.c. dose). AG10-L-E2- Naloxone was the only antidote that resulted in significant protection for the rats against OIRD and all animals (n = 6) survived. In contrast, both naloxone doses were not effective in preventing OIRD or mortality (4 animals died in the vehicle group; 3 animals died in 15 µmol kg-1dose of naloxone; and 2 animals died in 60 µmol kg-1dose of naloxone). This datasupport the observation of low efficacy of higher doses of naloxone despite the presence of asignificant concentration of naloxone in circulation (Fig 4) and highlight the potential challenges of using higher doses on mu-opioid antagonist for counteracting fentanyl overdose.Example 9: Preclinical evaluation of AG10-L1-E2-Naloxone – Rat StudiesWe evaluated the effect of AG10-L-E2-Naloxone on the body weight of three groupsof rats (n = 6 per group). Group one was treated with a vehicle. Group two was treated withAG10-L-E2-Naloxone (60 µmol kg-1). Group three was treated with fentanyl followed by AG10-L-E2-Naloxone (60 µmol kg-1) and then doses of fentanyl at 6 hr and 24 hr (same protocol as above). Rats were observed for four weeks, and no signs of toxicity or mortality were observed. All animals gained the expected body weight throughout the whole study period and no significant differences were observed between the AG10-L-E1-Nalxone compared to vehicle treated group (Fig.5h). We also tested the effect of high concentration of AG10-L-E2-Naloxone (at 100 µM, which is 100-fold higher than Cmaxin rat of 0.8 µM) and its metabolite, AG10-L-E2-COOH, on viability and proliferation of three cell lines. Cell viability (MTT) assay was performed using CellTiter 96 Non-Radioactive Cell Proliferation Assay. HeLa and MCF-7 cells were cultured in RPMI-1640 medium supplemented with 10% fetal bovine serum,penicillin / streptomycin (100 unit mL-1 and 100 μg / mL-1, respectively), and 1% l-glutamineunder the humidified atmosphere of 5% CO2 and 95% air at 37°C. Hep3B was cultured inminimum Eagle’s medium with 10% FBS. The cells were grown to about 75% confluenceand seeded into 96-well plates at ∼5000 cells / well for HeLa and MCF-7 cells and at ∼8000 cells / well for Hep3B and then treated with naloxone, AG10-L-E2-Naloxone and AG10-L-E2- COOH (tested at 100 µM) or Doxorubicin (10 µM) as a positive control. Control cells were also treated with the appropriate concentration of the vehicle (DMSO). Cell viability was determined following the standard CellTiter 96 Non-Radioactive Cell Proliferation Assay protocol after 72 hr incubation at 37°C and 5% CO2.Attorney Docket No. 330272000240Both compounds showed no cytotoxic effects toward any of the cell lines that were tested (Fig 5i-k). We also confirmed that AG10-L-E2-COOH was stable in aqueous solution for at least two months at room temperature. Example 10: Preclinical evaluation of AG10-L1-E2-Naloxone –Monkey Studies Materials and Methods A single subcutaneous (s.c.) injection of AG10-L-E2-Naloxone (30 µmol kg-1;equivalent to 31 mg kg-1of) was administered to three male cynomolgus monkey. Theconcentration of the AG10-L-E2-Naloxone and naloxone released from AG10-L-E2-Naloxone in plasma for each monkey was determined at different time points and expressedas means ± s.d. of three biological replicates. Results To evaluate the potential for translating our data to human, we evaluated the pharmacokinetic profile of AG10-L-E2-Naloxone in non-human primates, cynomolgus monkey (n = 3) (Fig 5l). Monkey represented a potential model since it lacks CES enzymes in plasma (Fig.2f) and the release naloxone form AG10-L-E2-Naloxone in Monkey liver microsomes is similar to that of human (Fig.2d). Monkey was also used as a preclinical model to test the efficacy of antidotes against fentanyl and carfentanil. AG10-L-E2-Naloxone was administered a single s.c. dose of (30 µmol kg-1; equivalent to 31 mg kg-1; which is half the dose in rats) and the plasma concentration of parent AG10-L-E2-Naloxone and naloxone released were measured over 72 hr. The enhanced pharmacokinetic profile of the parent AG10-L-E2-Naloxone was similar to that in rat (compared to typical 2 mg IM dose of naloxone; Cmax and disappear in 4 hr). AG10-L-E2-Naloxone was rapidly absorbed (plasma conc. At 5 min = 309 nM). The Cmax (2392 nM) was also achieved rapidly within 15 min of dosing. Importantly, the concentration of AG10-L-E2-Naloxone from 4 hr to 72 hr (the last timepoint tested) was within a narrow range (303 nM to 141 nM). The pharmacokinetic profile of the naloxone released from AG10-L-E2-Naloxone was remarkable, ranging from 3 nM at 15 min post dosing to 4.5 nM after 72 hr. The Cmax at 8 hr was 12.5 nM. The data on the lower concentration of naloxone relative to its parent prodrug, agree with in vitro data which is highlighted the stability of the prodrug in monkey plasma but allows the prodrug torelease naloxone by CES2 in liver and potentially other organs with CES2 activity. This slowand extended release of steady concentration of naloxone is what believe provided with the excellent efficacy profile in rats. We predict that the AG10-L-E2-Naloxone and naloxoneAttorney Docket No. 330272000240released will be extended to a longer time in monkey, which is supported by the pharmacokinetic study in rats (at least 96 hr; Fig 4a). Example 11: Development and preclinical testing of a naloxone prodrug depot for extended protection against opioid overdose Introduction In 2023, the US reported more than 80,000 opioid overdose deaths, the majority ofwhich were caused by synthetic opioids like fentanyl1. Among high school students, an average of 22 adolescents died weekly from fentanyl-laced counterfeit pills in 20222. Fentanyl, with a lethal dose of about two milligrams, poses significant risks, especially foropioid-naïve individuals. While the half-life of fentanyl (~7 hr) is relatively short, theduration of overdose could last for up to 24 hr3. Naloxone, a μ-opioid receptor antagonistused for reversing overdoses, has a short duration of action (DOA ~1 hr), requiring repeateddoses and continuous monitoring4. This highlights the need for long-acting opioid antagonists. Emerging approaches include pseudo-irreversible antagonists, covalent naloxone nanoparticles, and antibody-based strategies4-7. However, these approaches do not address themain challenges: rapid reversal of opioid-induced respiratory depression and subsequentprotection from re-narcotization. Developing extended-release opioid antagonists is crucial, and one promising approach involves using prodrugs that slowly release the active drug over time8-11. However, this prodrug approach has had limited success with naloxone so far. Our strategy involves endowing naloxone prodrugs with a hydrophilic derivative ofthe small molecule, AG10 (Alhamadsheh-Graef molecule 10 or acoramidis)12, which bindsreversibly to the plasma protein transthyretin (TTR). Acoramidis, discovered by our group, is the most potent and selective transthyretin (TTR) ligand and has recently received FDA approval for treating transthyretin amyloid cardiomyopathy (ATTR-CM)13. This example introduces a naloxone prodrug delivery system leveraging the ionizable properties of ourhydrophilic AG10 derivative. Upon subcutaneous administration of the fully soluble prodrugsolution, the prodrug forms a zwitterion at physiological pH, reducing the prodrug’s solubility and creating a depot that extends the release and duration of action of naloxone. The prodrug is specifically bioactivated by carboxylesterase 2 (CES2) enzyme present in human liver, allowing controlled and extended naloxone release. Additionally, its balanced hydrophilicity and ability to bind to TTR in plasma reduce passive diffusion across the blood- brain barrier (BBB), potentially lowering the risk of precipitated opioid withdrawal symptoms and central nervous system (CNS) toxicity.Attorney Docket No. 330272000240In this example we demonstrate the potential of our approach by developing analoxone prodrug that displays extended DOA compared to naloxone against fentanyl andmorphine overdose in rats. The consistent pharmacokinetic profile of naloxone released fromour prodrug in male rats and cynomolgus monkeys, combined with superior efficacy (in rats)and a promising safety profile and chemical stability, highlights the potential of translating this prodrug to humans. This simple and practical naloxone prodrug system could significantly advance the treatment of opioid overdoses and potentially other opioid-related disorders. Results Concept of the prodrug delivery system The degree of ionization and solubility of ionizable drugs is dependent on the pH of the drug solution. The absorption rate of a drug from the subcutaneous (s.c.) tissue is alsoaffected by the physiological pH of the s.c. interstitial fluid (pH ~7.4). One example is insulinglargine (Lantus®), which is a long-acting insulin analog (~24 hr DOA after s.c. injection). The incorporation of two arginine residues shifts its isoelectric point from pH 5.4 to 6.7, making it soluble in slightly acidic solution (pH 4)14. Upon injection into s.c. tissue, the acidic solution is neutralized by the interstitial fluid, forming a depot of micro-precipitates that dissolve slowly to release insulin glargine over time. The slow absorption rate of insulin glargine, acting as the rate-limiting step, influences its pharmacokinetic profile by controlling the gradual reduction in insulin plasma levels. This behavior exemplifies flip-flop kinetics, where the terminal phase of concentration decline is more dependent on release and absorption from the injection site than on systemic clearance15. However, the low levels of soluble free insulin glargine, along with the slow dissolution of the depot, result in delayed absorption and a slower onset of action compared to regular insulin. This delayed absorption is a drawback for long-acting lipid or polymer depots16, especially for applications requiring rapid onset, such as opioid antidotes. It's important to note that non-polymeric drugs that form a depot after injection, similar to insulin glargine, are quite rare. We recently developed a hydrophilic derivative of AG10 that enhances the DOA and limits BBB penetration of non-cleavable covalently linked opioid agonists and antagonists in rats17. Surprisingly, these highly hydrophilic covalent conjugates were rapidly absorbed after subcutaneous dosing, appearing in rat plasma within 2 minutes, despite their expected limitedAttorney Docket No. 330272000240membrane permeability. We hypothesize that these conjugates form a zwitterion at physiological pH, reducing the hydrophilicity / solubility of the conjugates in interstitial fluid, and forming a depot similar to insulin glargine. This led us to investigate utilizing the potential zwitterionic nature of the AG10 derivative to create a prodrug delivery system for extending the DOA of subcutaneously administered drugs, focusing on the opioid antagonist naloxone. Design of naloxone prodrugs Our prodrug approach involves conjugating a linker modified-hydrophilic derivative of AG10 to naloxone using esters with varying stability. Modeling studies indicated that AG10-Linker can extend out of TTR, allowing naloxone conjugation via different ester moieties. Esters, common in prodrugs, can be activated by hydrolysis through enzymatic or chemical means, with esterases present throughout the body, including in blood, liver, kidneys, adipose tissue, and brain18. We initially explored esterifying naloxone with aliphatic acid derivatives (AG10-L- E1-Naloxone, Fig.1a), but found the hydrolysis rate to be very rapid (discussed below). Recognizing that the metabolic fate of esters depends on their steric and electronic properties, we switched to using the aromatic para-amino benzoic acid (PABA) for forming the ester with naloxone (AG10-L-E2-Naloxone, Fig.1a). PABA was chosen for its stabilizing steric (aromatic moiety) and electronic (electron donating para-amino group) effects on the ester moiety. PABA is naturally occurring in humans, making it largely non-toxic (LD50 in dogs and rat >2 g kg-1)19. We also synthesized the acyl hydrolysis product of AG10-L-E2- Naloxone (i.e., AG10-L-E2-COOH, Fig.1a). As control for fatty acid conjugation(established half-life extension approach for peptides, through binding to albumin), wesynthesized a lipidated naloxone prodrug containing the PABA ester, C12-E2-Naloxone. All compounds were synthesized as HCl salts (utilizing the presence of multiple basic amines in the conjugates). To test our zwitterion hypothesis, we evaluated the aqueous solubility of test compounds in water and phosphate buffer (pH 7.4, to mimic the pH of s.c. tissue). Dissolving the prodrugs' HCl salts in water resulted in an acidic pH of ~3.5. All compounds, except C12-E2-Naloxone (5 µM), were soluble in water at 200 µM (Fig. 1b). The solubility of naloxoneat pH 7.4 in phosphate buffer was slightly lower (170 µM) than water. However, AG10-L-Attorney Docket No. 330272000240E2-Naloxone's solubility dropped significantly at pH 7.4 (44 µM) compared to water (200 µM), supporting our hypothesis that the zwitterionic form of AG10-Linker lowers solubility at physiological pH (Fig.6a). AG10-L-E2-COOH was fully soluble in both water and buffer (200 µM), indicating no zwitterion formation (Fig.6b). Conversely, AG10-L-E2-Ethyl,which forms a zwitterion (Fig. 6c), showed lower solubility at pH 7.4 (97 µM) compared topH 3.5 (200 µM). The logD7.4 values further supported the hypothesis, showing a majordecrease in hydrophilicity for zwitterionic AG10-L-E2-Ethyl (logD7.4 = 1.2) compared to AG10-L-E2-COOH (logD7.4 = -1.6). AG10-L-E2-Naloxone (logD7.4 = 1.5) demonstrated a balanced hydrophilicity / lipophilicity, compared to both naloxone (logD7.4= 1.2) and the lipidated C12-E2-Naloxone (logD7.4= 2.0), enhancing its s.c. absorption. Achieving this balance is important, as it enabled the formation of a depot while maintaining a significant free soluble fraction (44 µM, Fig.1b), which is essential for efficient and rapid prodrug absorption. Prodrugs bind selectively to TTR in buffer and in human serum The binding affinity of prodrugs AG10-L-E1-Naloxone and AG10-L-E2-Naloxone to TTR were evaluated using fluorescence polarization (FP) binding assay20(Kd = 394.3 nM and 258.8 nM, respectively; Fig.1c). This is comparable to AG10-L-E2-COOH (Kd = 213 nM). The selectivity of these compounds for TTR over more than 4,000 other human serum proteins was assessed using a TTR serum fluorescent probe exclusion (FPE) selectivity assay21. All test compounds demonstrated strong binding selectivity to TTR in human serum (~50 to 70% TTR occupancy) (Fig.1d, e). AG10-L-E2-Naloxone showed a TTR occupancy of 48.1%, similar to the approved TTR stabilizer, tafamidis (49.2%). AG10-L-E2-Naloxone and C12-E2-Naloxone prodrugs are stable in human plasma but release naloxone in rat plasma The in vivo efficacy studies of the prodrugs was evaluated in rats. Initially, weassessed the hydrolysis of the prodrug esters in human and rat plasma, given their similar TTR plasma concentrations (~ 5 µM) and the high sequence homology (~80%)22-24. The TTR thyroxine binding sites, where AG10 and prodrugs bind, are conserved between rat and human23. In human plasma, the alkyl-based AG10-L-E1-Naloxone prodrug was unstable, degrading completely within 1 min, while the PABA-based esters (AG10-L-E2-Naloxone and C12-E2-Naloxone) were fully stable at 24 hr (Fig.1f). This unexpected stability wasAttorney Docket No. 330272000240surprising since modeling studies showed that the PABA ester extends out of the TTR binding pocket, allowing esterase access (Fig.2b). To investigate this observation, we evaluated the stability of the prodrugs in rat plasma. AG10-L-E1-Naloxone degraded rapidly, while AG10-L-E2-Naloxone showed moderate stability (60% remaining after 15 min, 3.8% after 2 hr). C12-E2-Naloxone had slightly lower stability than AG10-L-E2-Naloxone. This disparity in hydrolysis rates pointed to carboxylesterase enzymes 1 and 2 (CES1 and CES2), which are present in rat plasma but absent in human plasma25. AG10-L-E2-Naloxone is specifically bioactivated by CES2 enzyme Carboxylesterase (CES) enzymes, CES1 and CES2, are crucial for the hydrolytic inactivation of many ester drugs25. Human CES1 is primarily responsible for the bioactivation of several prodrugs, while CES2 plays a minor role26,27. CES1 is highly expressed in the liver, whereas CES2 is primarily found in the small intestine, kidney, andliver. The expression level of CES2 in human liver is ~9-fold lower than CES127. Weinvestigated the roles of CES1 and CES2 in the bioactivation of AG10-L-E2-Naloxone. Due to its insolubility in buffer (Fig.1b), we could not evaluate the CES selectivity for C12-E2- Naloxone. In vitro studies with recombinant human CESs showed AG10-L-E2-Naloxone is aspecific substrate for CES2 (Fig. 2c), which is surprising since few prodrugs, like procaineand irinotecan, are selectively hydrolyzed by CES2. Procaine undergoes rapid hydrolysis bybutyrylcholinesterase in human plasma in addition to liver CES2, while irinotecan is slowly hydrolyzed by both CES1 and CES2, with less than 5% of the dose bioactivated27,28. To further investigate CES2 specificity and the potential for human translation, we assessed the metabolic bioactivation of AG10-L-E2-Naloxone in liver microsomes from humans, rats, andcynomolgus monkeys (Fig. 2d). Human liver microsomes (HLM) effectively producednaloxone from AG10-L-E2-Naloxone, and the CES2 inhibitor loperamide significantly decreased naloxone release, while the CES1 inhibitor digitonin had no protection. Rat liver microsomes (RLM) produced less naloxone due to higher metabolism and de-alkylation by CYP3A4. Given the similar CES2 expression in monkeys and humans25, monkey liver microsomes (MLM) showed naloxone release comparable to HLM, suggesting monkeys as suitable models for evaluating the efficacy of AG10-L-E2-Naloxone. The specific CES2 bioactivation of AG10-L-E2-Naloxone was confirmed using rat plasma with CES1 and CES2 inhibitors (Fig.2e). Additionally, AG10-L-E2-Naloxone showed 100% stability inAttorney Docket No. 330272000240cynomolgus monkey plasma (lacking CES1 and CES2)25 and 0% stability in rabbit plasma(high CES1 and CES2 levels) after 24 hr (Fig. 2f).The 9-fold lower liver concentration of CES2 compared to CES127provides unique bioactivation for AG10-L-E2-Naloxone. Additionally, CES2 is absent from s.c. adiposetissue while CES1 is present29, reducing the potential burst release of naloxone from theprodrug depot. While the crystal structure of human CES1 is available30, the first crystal structure of mouse CES2, a potential ortholog of human CES2, was recently reported31. The mouse CES2 structure resembles human CES1, with differences in active site access. Docking studies showed no binding of AG10-L-E2-Naloxone to CES1, but it fit well in theactive site of CES2, with the nucleophilic Serine (S230) in close proximity (2.9 Å) to thecarbonyl carbon of the ester group in AG10-L-E2-Naloxone (Fig. 2b and Fig. 7). These datawere supported by performing a docking study of the three known CES2 selective prodrugsirinotecan, procaine, and molnupiravir to both CES1 and CES2 (Fig. 7). The three prodrugsshowed very good binding to CES2 with a favorable distance between the nucleophilic S230 and the carbonyl carbon of prodrugs (3.3 Å, 3.1 Å, and 3.5 Å for irinotecan, procaine, and molnupiravir, respectively). While there was no binding between AG10-L-E2-Naloxone and CES1, the three other prodrugs displayed modest to weak binding with distance between the nucleophilic S230 and the carbonyl carbon of prodrugs (9.2 Å, 6.8 Å, and 4.8 Å for irinotecan, procaine, and molnupiravir, respectively). Therefore, our study represents the first docking experiment of a CES2-specific substrate, offering insights for designing additional CES2-specific prodrugs. The specific hydrolysis of AG10-L-E2-Naloxone by CES2 is driven by conjugation to AG10-Linker We investigated whether the specific hydrolysis of AG10-L-E2-Naloxone by CES2 is driven by the PABA ester or a combination of PABA and AG10-Linker. We synthesized three aryl-based naloxone prodrugs without the AG10-Linker. The benzoic acid naloxoneester (BA-Naloxone) hydrolyzed the fastest in human plasma, while the Boc-PABA-Naloxone and PABA-Naloxone were more stable (Fig. 8). This highlights the stabilizingeffect of the electron donating amine group in PABA on the ester moiety. All three compounds were effectively hydrolyzed in human plasma, indicating they are substrates for esterases other than CES1 or CES2. CES2 selectivity was demonstrated in rat plasma stability studies with CES2 and CES1 inhibitors. Our data suggest that the specific hydroly...

Claims

1. Attorney Docket No.330272000240 CLAIMS What is claimed is:

1. A conjugate of formula (I): (I) or a pharmaceutically acceptable salt thereof, wherein: T is a ligand selective for transthyretin TTR; L is a linker; LBis absent or a click product formed via a Click reaction between a first Click handle and a second click handle; E is a cleavable ester; and D1is a drug moiety.

2. The conjugate of claim 1, wherein: LBis the Click product of: (i) a copper-catalyzed reaction between an azide and an alkyne; (ii) a reaction between an azide and dibenzocyclooctene (DBCO); (iii) an inverse electron demand Diels-alder cycloaddition (IEDDA) between a trans- cyclooctene (TCO) moiety and a tetrazine ring, or (iv) a Staudinger reaction between an azide and a phosphine.

3. The conjugate of claim 1, comprising the moiety:wherein each R7is independently selected from the group consisting of hydrogen, halogen atoms (e.g., Cl, Br or F), hydroxy, -OCF3, -NH2, -NHC1-4alkyl, -N(C1-4alkyl)2, -CONH2, -Attorney Docket No.330272000240 CONHC1-4 alkyl, -CON(C1-4 alkyl)2, -NHCOC1-4 alkyl, C1-6 alkyl, C1-6 alkoxy and C3-6 cycloalkyl, p is 0, 1, 2, or 3, andindicates the point of attachment to the linker (L).

4. The conjugate of claim 1, wherein T has the structure of Compound (A):(A), or a pharmaceutically acceptable salt thereof, wherein: Xa, Xband Xcare independently selected from C(R8a)(R8b), O, N-R8bor S; where R8aand R8bare independently selected from hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl, aryl, substituted aryl, alkoxy, aryloxy, hydroxyl, heterocyclic group, halogen, nitro, acyl, substituted acyl, carboxyl, alkoxycarbonyl, substituted alkoxycarbonyl, aminoacyl, substituted aminoacyl, amino, substituted amino, acylamino, substituted acylamino, and cyano; a ring is a 4 to 12-membered ring, in certain embodiments the 4 to 12-membered ring is an aromatic or heteroaromatic ring; each Y is independently selected from hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl, aryl, substituted aryl, alkoxy, aryloxy, hydroxyl, heterocyclic group, halogen, nitro, acyl, substituted acyl, carboxyl, alkoxycarbonyl, substituted alkoxycarbonyl, aminoacyl, substituted aminoacyl, amino, substituted amino, acylamino, substituted acylamino, sulfonamide, sulfonyl fluoride, thioester and cyano; c is an integer ranging from 0 to 5; and, B ring is a heterocyclic ring selected from the following (h1-h30):Attorney Docket No.330272000240where R11-R16are independently selected from hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl, aryl, substituted aryl, alkoxy, aryloxy, hydroxyl, heterocyclic group, halogen, nitro, acyl, substituted acyl, carboxyl, alkoxycarbonyl, substituted alkoxycarbonyl, aminoacyl, substituted aminoacyl, amino, substituted amino, acylamino, substituted acylamino, and cyano; R17is selected from a hydroxyl, alkyl, amino, and alkyl amino; and at least one of R11-R16is the linking group to Xc.Attorney Docket No.330272000240 5. The conjugate of claim 1, wherein T has the structure of Compound (B):or a pharmaceutically acceptable salt thereof, wherein: n is an integer ranging from 0 to 8; R18, R19and R20are independently selected from hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl, aryl, substituted aryl, alkoxy, aryloxy, hydroxyl, heterocyclic group, halogen, nitro, acyl, substituted acyl, carboxyl, alkoxycarbonyl, substituted alkoxycarbonyl, aminoacyl, substituted aminoacyl, amino, substituted amino, acylamino, substituted acylamino, sulfonamide, sulfonyl fluoride, thioester and cyano; Xais C(R21)(R22), O, N-R22or S; where R21and R22are independently selected from hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl, aryl, substituted aryl, alkoxy, aryloxy, hydroxyl, heterocyclic group, halogen, nitro, acyl, substituted acyl, carboxyl, alkoxycarbonyl, substituted alkoxycarbonyl, aminoacyl, substituted aminoacyl, amino, substituted amino, acylamino, substituted acylamino, and cyano; A is a 5 to 12-membered ring, in certain embodiments the 5 to 12-membered ring is an aromatic or heteroaromatic ring; each Y is independently selected from hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl, aryl, substituted aryl, alkoxy, aryloxy, hydroxyl, heterocyclic group, halogen, nitro, acyl, substituted acyl, carboxyl, alkoxycarbonyl, substituted alkoxycarbonyl, aminoacyl, substituted aminoacyl, amino, substituted amino, acylamino, substituted acylamino, sulfonamide, sulfonyl fluoride, thioester and cyano; and, c is a number from zero to 5.Attorney Docket No.330272000240 6. The conjugate of claim 1, wherein T has the structure of Compound (C):or a pharmaceutically acceptable salt thereof, wherein: n is an integer ranging from 1 to 4; R23is a short chain alkyl having 1 to 4 carbon atoms; R24is hydrogen; R25is a short chain alkyl having 1 to 4 carbon atoms; Xa is C(R21)(R22), O, N-R22or S; where R21and R22are independently selected from hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl, aryl, substituted aryl, alkoxy, aryloxy, hydroxyl, heterocyclic group, halogen, nitro, acyl, substituted acyl, carboxyl, alkoxycarbonyl, substituted alkoxycarbonyl, aminoacyl, substituted aminoacyl, amino, substituted amino, acylamino, substituted acylamino, and cyano; each Y is independently selected from hydrogen, halogen, acyl, substituted acyl, carboxyl, heterocyclic group, alkoxycarbonyl sulfonamide, sulfonyl fluoride, thioester and substituted alkoxycarbonyl; and c is 2.

7. The conjugate of claim 1, wherein T has the structure of Compound (D):or a pharmaceutically acceptable salt thereof, wherein: n is 1 to 8; R23, R24and R25are independently selected from hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl, aryl, substituted aryl, alkoxy, aryloxy, hydroxyl, heterocyclic group, halo, nitro, acyl, substituted acyl, carboxyl, alkoxycarbonyl, substituted alkoxycarbonyl,Attorney Docket No.330272000240 aminoacyl, substituted aminoacyl, amino, substituted amino, acylamino, substituted acylamino, and cyano; Xais C(R21)(R22), O, N-R22or S; where R21and R22are independently selected from hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl, aryl, substituted aryl, alkoxy, aryloxy, hydroxyl, heterocyclic group, halogen, nitro, acyl, substituted acyl, carboxyl, alkoxycarbonyl, substituted alkoxycarbonyl, aminoacyl, substituted aminoacyl, amino, substituted amino, acylamino, substituted acylamino, and cyano; Rais CHO, COOH, COOCH3, COOR6, CONR7R8, tetrazolyl, CONHOH, B(OH)2, CONHSO2Ar, CONHCH(R9)COOH, CF3, hydrogen, halogen, alkyl, substituted alkyl, acyl, substituted acyl, carboxyl, heterocyclic group, sulfonamide, sulfonyl fluoride, thioester, alkoxycarbonyl or substituted alkoxycarbonyl; Rbis CHO, COOH, COOCH3, COOR26, CONR27R28, tetrazolyl, CONHOH, B(OH)2, CONHSO2Ar, CONHCH(R29)COOH, CF3, hydrogen, halogen, alkyl, substituted alkyl, acyl, substituted acyl, carboxyl, heterocyclic group, sulfonamide, sulfonyl fluoride, thioester, alkoxycarbonyl or substituted alkoxycarbonyl; R26is alkyl, haloalkyl, cycloalkyl, or heterocyclyl; R27and R28are each independently hydrogen, alkyl, alkenyl, alkynyl, cycloalkyl, heterocyclyl, or heteroaryl; and, R29is the side chain of a naturally occurring α-amino carboxylic acid.

8. The conjugate of claim 7, wherein T has the structure of Compound (E):or a pharmaceutically acceptable salt thereof.Attorney Docket No.330272000240 9. The conjugate of claim 7, wherein T has the structure of Compound (Y):or a pharmaceutically acceptable salt thereof.

10. A conjugate of formula (II’):or a pharmaceutically acceptable salt thereof, wherein: each R1is independently halo or C1-4alkyl; m is 0, 1, 2, or 3; R2is H or C1-4alkyl; X1is -O- or -NRx-; n is 0, 1, 2, 3, or 4 R3is H or C1-4alkyl; R4is H or C1-4alkyl;Attorney Docket No.330272000240 R5is H or C1-4alkyl; Rxis H or C1-4alkyl; L is a linker; Y1is a bond or C1-4alkylene; Y2is NR6, O or S; R6is H or C1-4alkyl; each R7is independently selected from the group consisting of hydrogen, halogen atoms (e.g., Cl, Br or F), NO2, CF3, OMe, O(C1-4 alkyl), hydroxy, -OCF3, -NH2, -NHC1-4 alkyl, - N(C1-4alkyl)2, -CONH2, -CONHC1-4alkyl, -CON(C1-4alkyl)2, -NHCOC1-4alkyl, C1-6alkyl, C1-6alkoxy and C3-6cycloalkyl; p is 0, 1, 2, or 3; and D1is a drug moiety.

11. A conjugate of formula (III’):or a pharmaceutically acceptable salt thereof, wherein: each R1is independently halo or C1-4alkyl; m is 0, 1, 2, or 3; R2is H or C1-4alkyl; X1is -O- or -NRx-; n is 0, 1, 2, 3, or 4; R3is H or C1-4alkyl; R4is H or C1-4alkyl;Attorney Docket No.330272000240 R5is H or C1-4alkyl; Rxis H or C1-4alkyl; LAis C3-20alkylene, wherein the C3-20alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, - NRy-, and -S-; each L1ais halo, C1-6alkyl, or C1-6alkyl substituted by halo; each Ryis H or C1-4alkyl; LBis a click product formed via a Click reaction between a first Click handle and a second click handle; Y1is a bond or C1-4alkylene; Y2is NR6, O, or S; R6is H or C1-4alkyl; each R7is independently selected from the group consisting of hydrogen, halogen atoms (e.g., Cl, Br or F), NO2, CF3, OMe, O(C1-4 alkyl), hydroxy, -OCF3, -NH2, -NHC1-4 alkyl, - N(C1-4alkyl)2, -CONH2, -CONHC1-4alkyl, -CON(C1-4alkyl)2, -NHCOC1-4alkyl, C1-6alkyl, C1-6 alkoxy and C3-6 cycloalkyl; p is 0, 1, 2, or 3; and D1is a drug moiety.

12. A conjugate of formula (IV’):or a pharmaceutically acceptable salt thereof, wherein:Attorney Docket No.330272000240 each R1is independently halo or C1-4alkyl; m is 0, 1, 2, or 3; R2is H or C1-4alkyl; X1is -O- or -NRx-; n is 0, 1, 2, 3, or 4; R3is H or C1-4alkyl; R4is H or C1-4alkyl; R5is H or C1-4alkyl; Rxis H or C1-4alkyl; LAis C3-20alkylene, wherein the C3-20alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, - NRy-, and -S-; each L1ais halo, C1-6alkyl, or C1-6alkyl substituted by halo; each Ryis H or C1-4alkyl; LBis a click product formed via a Click reaction between a first Click handle and a second click handle; Y1is a bond or C1-4alkylene; Y2is NR6, O, or S; R6is H or C1-4alkyl; each R7is independently selected from the group consisting of hydrogen, halogen atoms (e.g., Cl, Br or F), NO2, CF3, OMe, O(C1-4alkyl), hydroxy, -OCF3, -NH2, -NHC1-4alkyl, - N(C1-4alkyl)2, -CONH2, -CONHC1-4alkyl, -CON(C1-4alkyl)2, -NHCOC1-4alkyl, C1-6alkyl, C1-6 alkoxy and C3-6 cycloalkyl; p is 0, 1, 2, or 3; and D1is a drug moiety.Attorney Docket No.330272000240 13. A conjugate of formula (V’):or a pharmaceutically acceptable salt thereof, wherein: each R1is independently halo or C1-4alkyl; m is 0, 1, 2, or 3; R2is H or C1-4alkyl; X1is -O- or -NRx-; n is 0, 1, 2, or 3; R3is H or C1-4alkyl; R4is H or C1-4alkyl; R5is H or C1-4alkyl; Rxis H or C1-4alkyl; LAis C3-20alkylene, wherein the C3-20alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, - NRy-, and -S-; each L1ais halo, C1-6alkyl, or C1-6alkyl substituted by halo; each Ryis H or C1-4alkyl; Y1is a bond or C1-4alkylene; Y2is NR6, O or S; R6is H or C1-4alkyl; each R7is independently selected from the group consisting of hydrogen, halogen atoms (e.g., Cl, Br or F), hydroxy, -OCF3, -NH2, -NHC1-4alkyl, -N(C1-4alkyl)2, -CONH2, -Attorney Docket No.330272000240 CONHC1-4 alkyl, -CON(C1-4 alkyl)2, -NHCOC1-4 alkyl, C1-6 alkyl, C1-6 alkoxy and C3-6 cycloalkyl; p is 0, 1, 2, or 3; and D1is a drug moiety.

14. A conjugate of formula (VI’):or a pharmaceutically acceptable salt thereof, wherein: each R1is independently halo or C1-4alkyl; m is 0, 1, 2, or 3; R2is H or C1-4alkyl; X1is -O- or -NRx-; n is 0, 1, 2, or 3; R3is H or C1-4alkyl; R4is H or C1-4alkyl; R5is H or C1-4alkyl; Rxis H or C1-4alkyl; LAis C3-20alkylene, wherein the C3-20alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, - NRy-, and -S-; each L1ais halo, C1-6alkyl, or C1-6alkyl substituted by halo; each Ryis H or C1-4alkyl; Y1is a bond or C1-4alkylene; Y2is NR6, O or S;Attorney Docket No.330272000240 R6is H or C1-4alkyl; each R7is independently selected from the group consisting of hydrogen, halogen atoms (e.g., Cl, Br or F), hydroxy, -OCF3, -NH2, -NHC1-4alkyl, -N(C1-4alkyl)2, -CONH2, - CONHC1-4 alkyl, -CON(C1-4 alkyl)2, -NHCOC1-4 alkyl, C1-6 alkyl, C1-6 alkoxy and C3-6 cycloalkyl p is 0, 1, 2, or 3; and D1is a drug moiety (opioid agonist or opioid antagonist).

15. A conjugate of formula (VII’):or a pharmaceutically acceptable salt thereof, wherein: each R1is independently halo or C1-4alkyl; m is 0, 1, 2, or 3; R2is H or C1-4alkyl; X1is -O- or -NRx-; n is 0, 1, 2, or 3; R3is H or C1-4alkyl; R4is H or C1-4alkyl; R5is H or C1-4alkyl; Rxis H or C1-4alkyl; Y1is a bond or C1-4alkylene; Y2is NR6, O or S;Attorney Docket No.330272000240 LBis a click product formed via a Click reaction between a first Click handle and a second click handle; R6is H or C1-4alkyl; each R7is independently selected from the group consisting of hydrogen, halogen atoms (e.g., Cl, Br or F), hydroxy, -OCF3, -NH2, -NHC1-4alkyl, -N(C1-4alkyl)2, -CONH2, - CONHC1-4alkyl, -CON(C1-4alkyl)2, -NHCOC1-4alkyl, C1-6alkyl, C1-6alkoxy and C3-6cycloalkyl; p is 0, 1, 2, or 3; r is 1, 2, 3, 4, 5, 6, or 7; s is 1, 2, 3, 4, 5, 6, or 7; and D1is a drug moiety.

16. A conjugate of formula (VIII’):or a pharmaceutically acceptable salt thereof, wherein: each R1is independently halo or C1-4alkyl; m is 0, 1, 2, or 3; R2is H or C1-4alkyl; X1is -O- or -NRx-; n is 0, 1, 2, or 3; R3is H or C1-4alkyl; R4is H or C1-4alkyl; R5is H or C1-4alkyl; Rxis H or C1-4alkyl;Attorney Docket No.330272000240 Y1is a bond or C1-4alkylene; Y2is NR6, O or S; LBis a click product formed via a Click reaction between a first Click handle and a second click handle; R6is H or C1-4alkyl; each R7is independently selected from the group consisting of hydrogen, halogen atoms (e.g., Cl, Br or F), hydroxy, -OCF3, -NH2, -NHC1-4 alkyl, -N(C1-4 alkyl)2, -CONH2, - CONHC1-4 alkyl, -CON(C1-4 alkyl)2, -NHCOC1-4 alkyl, C1-6 alkyl, C1-6 alkoxy and C3-6 cycloalkyl; p is 0, 1, 2, or 3; r is 1, 2, 3, 4, 5, 6, or 7; s is 1, 2, 3, 4, 5, 6, or 7; t is 1, 2, 3, or 4; u is 1, 2, 3, or 4; and D1is a drug moiety.

17. A conjugate of formula (IX):or a pharmaceutically acceptable salt thereof, wherein: each R1is independently halo or C1-4alkyl; m is 0, 1, 2, or 3; R2is H or C1-4alkyl; X1is -O- or -NRx-; n is 0, 1, 2, or 3; R3is H or C1-4alkyl; R4is H or C1-4alkyl;Attorney Docket No.330272000240 R5is H or C1-4alkyl; Rxis H or C1-4alkyl; L is a linker; Z1is C1-6alkyl, C6-10aryl, or 5- to 10-membered heteroaryl, wherein the C1-6alkyl is optionally substituted with one or more Z1a, and the C6-10aryl or 5- to 10-membered heteroaryl is optionally substituted with one or more Z1b; each Z1aor Z1bis independently halo, C1-6alkoxy, or C1-6alkyl optionally substituted by halo; and D1is a drug moiety (opioid agonist or opioid antagonist).

18. A conjugate of formula (X):or a pharmaceutically acceptable salt thereof, wherein: each R1is independently halo or C1-4alkyl; m is 0, 1, 2, or 3; R2is H or C1-4alkyl; X1is -O- or -NRx-; n is 0, 1, 2, or 3; R3is H or C1-4alkyl; R4is H or C1-4alkyl; R5is H or C1-4alkyl; Rxis H or C1-4alkyl; LAis C3-20alkylene, whereinAttorney Docket No.330272000240 the C3-20alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, - NRy-, and -S-; each L1ais halo, C1-6alkyl, or C1-6alkyl substituted by halo; each Ryis H or C1-4alkyl; LBis a click product formed via a Click reaction between a first Click handle and a second click handle; Z1is C1-6alkyl, C6-10aryl, or 5- to 10-membered heteroaryl, wherein the C1-6alkyl is optionally substituted with one or more Z1a, and the C6-10aryl or 5- to 10-membered heteroaryl is optionally substituted with one or more Z1b; each Z1aor Z1bis independently halo, C1-6alkoxy, or C1-6alkyl optionally substituted by halo; and D1is a drug moiety.

19. A conjugate of formula (XI):or a pharmaceutically acceptable salt thereof, wherein: each R1is independently halo or C1-4alkyl; m is 0, 1, 2, or 3; R2is H or C1-4alkyl; X1is -O- or -NRx-; n is 0, 1, 2, or 3; R3is H or C1-4alkyl; R4is H or C1-4alkyl;Attorney Docket No.330272000240 R5is H or C1-4alkyl; Rxis H or C1-4alkyl; LAis C3-20alkylene, wherein the C3-20alkylene is optionally substituted with one or more L1a, and one or more alkylene units is optionally replaced with a group selected from -O-, - NRy-, and -S-; each L1ais halo, C1-6alkyl, or C1-6alkyl substituted by halo; each Ryis H or C1-4alkyl; Z1is C1-6alkyl, C6-10aryl, or 5- to 10-membered heteroaryl, wherein the C1-6alkyl is optionally substituted with one or more Z1a, and the C6-10aryl or 5- to 10-membered heteroaryl is optionally substituted with one or more Z1b; each Z1aor Z1bis independently halo, C1-6alkoxy, or C1-6alkyl optionally substituted by halo; and D1is a drug moiety.

20. The conjugate of any one of claims 1-19, wherein D1is a peptide.

21. The conjugate of any one of claims 1-19, wherein D1is a small molecule, a nucleotide, an oligonucleotide, a polynucleotide, an amino acid, an oligopeptide, a polypeptides, or a protein.

22. The conjugate of any one of claims 1-19, wherein D1is a cytokine.

23. The conjugate of claim 22, wherein the cytokine is Interleukin-2 (IL-2).

24. The conjugate of claim 22, wherein the cytokine is Interleukin-15 (IL-15).

25. The conjugate of any one of claims 1-19, wherein D1is an anti-cancer agent.

26. The conjugate of claim 25, wherein the anti-cancer agent is SN-38, irinotecan, capecitabine, monomethyl auristatin E, trifluridine, docetaxel, or infigratinib.

27. The conjugate of any one of claims 1-19, wherein D1is insulin.Attorney Docket No.330272000240 28. The conjugate of any one of claims 1-19, wherein D1is a glucagon-like-peptide-1 (GLP-1) agonist.

29. The conjugate of claim 28, wherein the GLP-1 agonist is semaglutide, liraglutide, dulaglutide, albiglutide, or exenatide.

30. The conjugate of any one of claims 1-19, wherein D1is a glucagon-like-peptide-1 (GLP-1) and GIP (glucose-dependent insulinotropic polypeptide) receptor agonist.

31. The conjugate of claim 30, wherein glucagon-like-peptide-1 (GLP-1) and GIP (glucose-dependent insulinotropic polypeptide) receptor agonist tirzepatide.

32. A method of treating a disease, comprising administering a conjugate if any one of claims 1-31.

33. The method of claim 32, further comprising administering a second drug (D2) in free (unconjugated) form.

34. The method of claim 33, wherein D1is the same as D2.

35. The method of claim 33, wherein D1is different than D2.

36. A method of treating cancer, comprising administering a conjugate of claim 25 or claim 26.

37. The method of claim 36, further comprising administering a second drug (D2) in free (unconjugated) form.

38. The method of claim 37, wherein D1is the same as D2.

39. The method of claim 37, wherein D1is different than D2.Attorney Docket No.330272000240 40. A method of treating obesity comprising administering a conjugate of any one of claims 28-31.

41. A method of treating diabetes comprising administering a conjugate of any one of claims 28-31.

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