Gastrin-releasing peptide receptor (GRPR)-targeted compounds and uses thereof

Abstract

The present invention rreellaatteess to gastrin-releasing peptide receptor (GRPR)-targeted compounds and their use for imaging and treatment of diseases or conditions characterized by expression of the gastrin-releasing peptide receptor.

Description

GASTRIN-RELEASING PEPTIDE RECEPTOR (GRPR)-TARGETED COMPOUNDS AND USES THEREOFCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 603,961 , filed on November 29, 2023, the contents of which is hereby incorporated by reference in its entirety for all purposes.REFERENCE TO AN ELECTRONIC SEQUENCE LISTING

[0002] The contents of the electronic sequence listing (A9TH_024_01WO_Seql_ist_ST26.xml; Size: 62,397 bytes; and Date of Creation: November 19, 2024) are herein incorporated by reference in its entirety.FIELD OF INVENTION

[0003] The present invention relates to gastrin-releasing peptide receptor (GRPR)-targeted compounds and their use for imaging and treatment of diseases or conditions characterized by expression of the gastrin-releasing peptide receptor.BACKGROUND OF THE INVENTION

[0004] Gastrin-releasing peptide receptor (GRPR) is a G protein-coupled receptor of the bombesin (BBN) receptor family (Roesler & Schwartsmann. 2012. Front Endocrinol (Lausanne) 3:159; Bitar & Zhu. 1993. Gastroenterology. 105:1672-1680; Weber. 2009. Curr Opin Endocrinol Diabetes Obes. 16:66-71). Together with its endogenous ligand, gastrin-releasing peptide (GRP), GRPR is involved in synaptic plasticity, emotional and feeding behavior, hormone secretion, smooth muscle contraction, and cell proliferation ibid.). In normal conditions, the expression of GRPR is restricted to the central nervous system, pancreas, adrenal cortex and gastrointestinal tract (Jensen, et al. 2008. Pharmacol Rev. 60:1-42). GRPR is also implicated in neoplastic progression, with overexpression of GRPR having been reported in many cancer subtypes including lung, head and neck, colon, kidney, ovarian, breast and prostate cancers (Cornelio, et al. Ann Oncol. 2007, 18:1457-1466). This ectopic expression in cancers makes it an attractive target for personalized therapies.

[0005] BBN is a 14 amino acid GRPR binding peptide (Lin, et al. 2004. Bioconjugate Chemistry. Vol 15. American Chemical Society pages 1416-1423; Inkster, et al. 2013 Bioorganic Med Chem Lett. 23:3920-3926; Mansi, etal. 2016 J Nucl Med. 57:67S-72S; Bodei, et al. 2007.177Lu-AMBA Bombesin analogue in hormone refractory prostate cancer patients: a phase I escalation study with single-cycle administrations. In: JOINT EANM-EORTCSymposium; Sah, et al. 2015 J Nucl Med. 56:372-378; Zang, et al. 2018 Clin Nucl Med. 43:663-669; Nock, et al. 2017 J Nucl Med. 58:75-80; Maina, et al. 2016 Eur J Nucl Med Mol Imaging 43:964-973). BBN derivatives have been radiolabeled for imaging with single photon emission computed tomography (SPECT), positron emission tomography (PET), and have also been radiolabeled for therapy with beta and alpha emitters (Maina, et al. PET Clin. 2017;12:297-309; Lin, et al. 2004. Bioconjugate Chemistry. Vol 15. American Chemical Society pages 1416-1423; Inkster, et al. 2013 Bioorganic Med Chem Lett. 23:3920-3926). Often, a radiolabelled group is appended directly onto the structure or via a linker at the N-terminus, while modifications at the C-terminus dictate agonist / antagonist properties. For targeting GRPR, antagonists are preferred since agonists have been shown to induce gastrointestinal adverse events (Bodei, et al. 2007.177Lu-AMBA Bombesin analogue in hormone refractory prostate cancer patients: a phase I escalation study with single-cycle administrations. In: JOINT EANM-EORTC Symposium). Examples of GRPR antagonists evaluated in the clinic include:68Ga-RM2,68Ga-SB3,68Ga-NeoBOMB1 ,68Ga-RM26,18F-BAY-864367, and64Cu-CB-TE2A-AR06 (Mansi, et al. 2016 J Nucl Med. 57:67S-72S; Sah, et al. 2015 J Nucl Med. 56:372-378; Zang, et al. 2018 Clin Nucl Med. 43:663-669; Nock, et al. 2017 J Nucl Med. 58:75-80; Maina, et al. 2016 Eur J Nucl Med Mol Imaging 43:964-973; Kahkonen, et al. Clin Cancer Res. 2013;19:5434-5443, Kahkonen, et al. Clin Cancer Res. 2013;19:5434-5443; Baum, et al. 2007 Journal of Nuclear Medicine 48, 79P-79P). However, high pancreas uptake remains the major limitation of currently reported GRPR-targeting radioligands.

[0006] In a study, the high pancreas uptake of68Ga-labeled AMBA was up to 54.9 SUV (SUV: standard uptake value) (Baum, et al. 2007 Journal of Nuclear Medicine 48, 79P-79P). In addition,68Ga-labeled RM2 was also reported to show high uptake in pancreas (Kurth, et al. 2020. European journal of nuclear medicine and molecular imaging 47 , 123-135; Minamimoto, et al. 2016 J Nucl Med. 57:557-562). It has also been reported that radiolabeled NeoBOMBI showed high pancreas uptake in both PC-3 tumor-bearing mice and prostate cancer patients (Nock, et al. 2017 J Nucl Med. 58:75-80).

[0007] Another limitation for most of the reported GRPR-targeting ligands is their in vivo metabolic instability (Bakker, et al. 2018 Molecular imaging and biology 20, 973-983; Rousseau, et al. 2020 Journal of Labelled Compounds and Radiopharmaceuticals 63, 56-64) due to enzymatic degradation by neutral endopeptidase (NEP) (Nock, et al. 2014 J Nucl Med. 55:121-127). His12-Leu13, Trp8-Ala9and Gln7-Trp8were reported to be the main cleavage sites within the AMBA’s sequence, and Trp8-Ala9, Ala9-Val10and Gln7-Trp8were considered to be the cleavage sites of RM2 (Kahkonen, et al. 2013 Clin Cancer Res. 19:5434-5443; Linder et al. 2009 Bioconjugate chemistry 20, 1 171-1 178).

[0008] There remains an unmet need in the field for improved tracers for the non-invasive in-vivo imaging of the GRPR. Such tracers are useful for the diagnosis of disorders related to aberrant / ectopic expression of GRPR, including but not limited to cancer (e.g. prostate cancer). There also remains an unmet need for improved radiotherapeutic agents for treatment of diseases / disorders related to aberrant / ectopic expression of GRPR, including but not limited to cancer (e.g. prostate cancer). In particular, there is a need for GRPR-targeting radioligands (for imaging and / or therapy) with lower pancreas uptake, and useful stability in vivo.

[0009] No admission is necessarily intended, nor should it be construed, that any of the preceding information constitutes prior art against the present invention.SUMMARY

[0010] The present disclosure provides a new class of peptidic compounds that bind to GRPR. Such compounds may have lower pancreas uptake and increased tumor uptake than prior art bombesin analogs as well as useful stability in vivo for imaging and / or radiotherapy.

[0011] In one aspect, this disclosure provides a peptidic compound of Formula (I), or a salt or solvate thereof, optionally complexed with a radioisotope (e.g., a radiometal or a radiohalogen):Rradn6-[linker]-RL-Xaa1-Xaa2-Xaa3-Xaa4-Xaa5-Xaa6-Xaa7-Xaa8-(qj-Xaa9)m-R(I) wherein:Xaa1is an N-terminal amino acid residue selected from D-Phe, 4-chlorophenylalanine (Cpa), D-Cpa, 3-(1-naphthyl)alanine (Nal), D-Tpi, D-Nal, 3-(2-naphthyl)alanine (2-Nal), or D-2-Nal;Xaa2is Asn, Gin, homoserine (Hse), citrulline (Cit) or His;Xaa3is Trp, |3-(3-benzothienyl)alanine (Bta), Trp(Me), Trp(7-Me), Trp(6-Me), Trp(5-Me), Trp(4-Me), Trp(2-Me), Trp(7-F), Trp(6-F), Trp(5-F), Trp(4-F), Trp(5-OH), Tpi, 7-Aza, or aMe-Trp;Xaa4is Ala or Ser;Xaa5is Vai, 2,3-dehydro-Val, Cpg (cyclopentylglycine), L-cyclopropylglycine, L-cyclobutylg lycine, or tert-leucine (Tie);Xaa6is Gly, NMe-Gly, or D-Ala;Xaa7is His or NMe-His;R is -NH2or -NHOH; m is 0 or 1 ;when m is 0, Xaa8-R is a C-terminally amidated (R is -NH2) or a C-terminally hydroxylamidated (R is -NHOH) amino acid residue selected from statine (Sta), Leu, D-Pro, or Phe; when m is 1 , Xaa8is statine (Sta), Leu, D-Pro, or Phe; and Xaa9-R is aC-terminally amidated (R is -NH2) or a C-terminally hydroxylamidated (R is -NHOH) amino acid residue selected from Pro, Phe, oxazolidine-4-carboxylic acid (4-oxa-L-Pro), 4,4-difluoroproline (diFPro), Leu, Me2Thz (5,5-dimethyl-1 ,3-thiazolidine-4-carboxylic acid), or thiazoline-4-carboxylic acid (Thz); qj represents a peptide bond or reduced peptide bond joining Xaa8to Xaa9; RLis -C(O)-, -NH-C(O)-, or -NH-C(S)-; the linker is a linear or branched chain of n1 units of -L1R1- and / or -(L1)2R1-, wherein: n1 is 1-20; each R1is, independently, a linear, branched, and / or cyclic Cn2alkylenyl, alkenylenyl and / or alkynylenyl, wherein each n2 is independently 1-20, wherein any carbon bonded to two other carbons is optionally independently replaced by N, S, or O, and carbons are optionally independently substituted with oxo, hydroxyl, sulfhydryl, -SeH, halogen, guanidino, amine, amide, urea, carboxylic acid, sulfonic acid, sulfinic acid, or phosphoric acid;L1bonds to carbon, wherein each L1is independently -S-, -N(R2)C(O)-,R2is H, methyl or ethyl; an albumin binder (Ralb) is optionally bonded to an L1of the linker, wherein the albumin binder is:-(CH2)n3-CH3wherein n3 is 8-20; H wherein n4 is 8-20;wherein n5 is 1-4 and R3ais H or methyl, and R3bis I, Br, F, Cl, H, OH, OCH3, NH2, NO2or Ci-C6alkyl; orn6 is 1-5; each Rradis a radiolabeling group bonded to or incorporating an L1of the linker, wherein each radiolabeling group is independently: a radiometal chelator wherein the radiometal chelator is optionally bound to a radiometal, a radionuclide-bound metal, or a radionuclide-bound metal-containing prosthetic group; an aryl or heteroaryl substituted with a radiohalogen; a prosthetic group containing a trifluoroborate; a prosthetic group containing a silicon-fluorine-acceptor moiety; or a prosthetic group containing a fluorophosphate, fluorosulfate, sulfonyl fluoride, or a combination thereof; and wherein(i) Xaa3is Trp(7-F) and Xaa9-R is a C-terminally amidated Pro or diFPro;(ii) qj represents a reduced peptide bond, m is 1 , Xaa3is |3-(3-benzothienyl)alanine (Bta), Trp(Me), Trp(7-Me), Trp(6-Me), Trp(5-Me), Trp(4-Me), Trp(2-Me), Trp(7-F), Trp(6-F), Trp(5-F), Trp(4-F), Trp(5-OH), Tpi, 7-Aza, or aMe-Trp, and Xaa9-R is a C-terminally amidated Pro or diFPro; or(iii) a combination of (i) and (ii); and wherein Xaa1, Xaa2, Xaa3, Xaa4, Xaa5, Xaa6, Xaa7, Xaa8, or Xaa9is each optionally methylated.

[0012] In another aspect, this disclosure also covers a pharmaceutical composition comprising a peptidic compound described above and a pharmaceutically acceptable carrier or excipient.

[0013] In some embodiment of the peptidic compound, Xaa1is an N-terminal amino acid residue selected from D-Phe; Xaa2is Gin; Xaa3isTrp(7-F); Xaa4is Ala; Xaa5is Vai or Tie; Xaa6is Gly or NMe-Gly; Xaa8is Leu; Xaa7is His; Xaa8is Leu; Xaa9-R is a C-terminally amidated Pro; m is 1 ; and qj represents a reduced peptide bond.

[0014] In a further aspect, this disclosure provides a method of imaging GRPR in a subject, the method comprising administering to the subject one of the above peptidic compounds or a composition comprising the same; and imaging tissue of the subject.

[0015] Still within the scope of this disclosure is a method of treating cancer in a subject comprising administering to the subject in need thereof the above described peptidic compound or composition.BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The features of the invention will become apparent from the following description in which reference is made to the appended drawings wherein:

[0017] Figure 1 shows the binding curves of four Lu- or La-cold metal labeled peptides via in vitro competition binding assay.DETAILED DESCRIPTION

[0018] As used herein, the terms “comprising,” “having”, “including” and “containing,” and grammatical variations thereof, are inclusive or open-ended and do not exclude additional, unrecited elements and / or method steps, even if a feature / component defined as a part thereof consists or consists essentially of specified feature(s) / component(s). The term “consisting essentially of’ if used herein in connection with a compound, composition, use or method, denotes that additional elements and / or method steps may be present, but that these additions do not materially affect the manner in which the recited compound, composition, method or use functions. The term “consisting of’ if used herein in connection with a feature of a compound, composition, use or method, excludes the presence of additional elements and / or method steps in that feature. A compound, composition, use or method described herein as comprising certain elements and / or steps may also, in certain embodiments consist essentially of those elements and / or steps, and in other embodiments consist of those elements and / or steps, whether or not these embodiments are specifically referred to. A use or method described herein as comprising certain elements and / or steps may also, in certain embodiments consist essentially of those elements and / or steps, and in other embodiments consist of those elements and / or steps, whether or not these embodiments are specifically referred to.

[0019] A reference to an element by the indefinite article “a” does not exclude the possibility that more than one of the elements is present, unless the context clearly requires that there be one and only one of the elements. The singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise. The use of the word “a” or “an” when used herein in conjunction with the term “comprising” may mean “one,” but it is also consistent with the meaning of “one or more,” “at least one” and “one or more than one.”

[0020] In this disclosure, the recitation of numerical ranges by endpoints includes all numbers subsumed within that range including all whole numbers, all integers and, where suitable, all fractional intermediates (e.g., 1 to 5 may include 1 , 1.5, 2, 2.75, 3, 3.80, 4, and 5 etc.).

[0021] Unless otherwise specified, “certain embodiments”, “various embodiments”, “an embodiment” and similar terms includes the particular feature(s) described for that embodiment either alone or in combination with any other embodiment or embodiments described herein, whether or not the other embodiments are directly or indirectly referencedand regardless of whether the feature or embodiment is described in the context of a method, product, use, composition, compound, et cetera.

[0022] As used herein, the terms “treat”, “treatment”, “therapeutic” and the like includes ameliorating symptoms, reducing disease progression, improving prognosis and reducing recurrence.

[0023] As used herein, the term “diagnostic agent” includes an “imaging agent”. As such, a “diagnostic radionuclide” includes radionuclides that are suitable for use in imaging agents.

[0024] The term “subject” refers to an animal (e.g. a mammal or a non-mammal animal). The subject may be a human or a non-human primate. The subject may be a laboratory mammal (e.g., mouse, rat, rabbit, hamster and the like). The subject may be an agricultural animal (e.g., equine, ovine, bovine, porcine, camelid and the like) or a domestic animal (e.g., canine, feline and the like). In some embodiments, the subject is a human.

[0025] The compounds disclosed herein may also include base-free forms, solvates, salts or pharmaceutically acceptable salts thereof. Unless otherwise specified or indicated, the compounds claimed and described herein are meant to include all racemic mixtures and all individual enantiomers or combinations thereof, whether or not they are explicitly represented herein.

[0026] The compounds disclosed herein may be shown as having one or more charged groups, may be shown with ionizable groups in an uncharged (e.g. protonated) state or may be shown without specifying formal charges. As will be appreciated by a person of skill in the art, the ionization state of certain groups within a compound (e.g. without limitation, COOH, and the like) is dependent, inter alia, on the pKa of that group and the pH at that location. For example, but without limitation, a carboxylic acid group (i.e. COOH) would be understood to usually be deprotonated (and negatively charged) at neutral pH and at most physiological pH values, unless the protonated state is stabilized.

[0027] As used herein, the terms “salt” and “solvate” have their usual meaning in chemistry. As such, when the compound is a salt or solvate, it is associated with a suitable counter-ion. It is well known in the art how to prepare salts or to exchange counter-ions. Generally, such salts can be prepared by reacting free acid forms of these compounds with a stoichiometric amount of a suitable base (e.g. without limitation, Na, Ca, Mg, or K hydroxide, carbonate, bicarbonate, or the like), or by reacting free base forms of these compounds with a stoichiometric amount of a suitable acid. Such reactions are generally carried out in water or in an organic solvent, or in a mixture of the two. Counter-ions may be changed, for example, by ion-exchange techniques such as ion-exchange chromatography. All zwitterions, salts, solvates and counter-ions are intended, unless a particular form is specifically indicated.

[0028] In certain embodiments, the salt or counter-ion may be pharmaceutically acceptable, for administration to a subject. As used herein, “pharmaceutically acceptable” means suitablefor in vivo use in a subject, and is not necessarily restricted to therapeutic use, but also includes diagnostic use. More generally, with respect to any pharmaceutical composition disclosed herein, non-limiting examples of suitable excipients include any suitable buffers, stabilizing agents, salts, antioxidants, complexing agents, tonicity agents, cryoprotectants, lyoprotectants, suspending agents, emulsifying agents, antimicrobial agents, preservatives, chelating agents, binding agents, surfactants, wetting agents, non-aqueous vehicles such as fixed oils, or polymers for sustained or controlled release. See, for example, Berge et al. 1977. (J. Pharm Sci. 66:1-19), or Remington- The Science and Practice of Pharmacy, 21st edition (Gennaro et al editors. Lippincott Williams & Wilkins Philadelphia), each of which is incorporated by reference in its entirety.

[0029] As used herein, the expression “Cn” where n is an integer (e.g. 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 , 12, 13, 14, 15, 16,17, 18, 19, 20, and the like) or where n is defined as a range of integers (e.g. 1-20, 1-18, 2-15, 3-20, and the like) refers to the number of carbons in a compound, R-group, L-group, or substituent, or refers to the number of carbons plus heteroatoms in a compound, R-group, L-group, or substituent. A range of integers includes all integers in the range; e.g. the range 1-20 includes the integers 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 , 12, 13, 14, 15, 16, 17, 18, 19, and 20. Unless otherwise defined, heteroatoms may include any, some or all possible heteroatoms. For example, in some embodiments, the heteroatoms may be selected from N, O, S, P and Se. In some embodiments, the heteroatoms are selected from N, S, or O. Such embodiments are non-limiting. The alternative expression “Cy-Cz”, where y and z are integers (e.g. C3-C15 and the like), is equivalent to “Cn” where n is a range of integers from y to z.

[0030] The terms “alkyl”, “alkylenyl”, “alkenylenyl”, and “alkynylenyl” have their usual meanings in organic chemistry. For example, an “alkyenylenyl” has at least one carbon-carbon double bond, and may have any number of carbon-carbon single bonds. Similarly, an “alkynylenyl” has at least one carbon-carbon triple bond, and may have any number of carbon-carbon single bonds. The expressions “alkylenyl, alkenylenyl and / or alkynylenyl” and “alkylenyl, alkenylenyl or alkynylenyl” are intended to be equivalent and each includes hydrocarbon chains that can have any reasonable number or combination of carbon-carbon single bonds, double bonds, and triple bonds. These hydrocarbon chains can be linear, branched, cyclic, or any combination of linear and branched, linear and cyclic, cyclic and branched, branched and cyclic, or linear, branched and cyclic. Cyclic hydrocarbons may be nonaromatic, partially aromatic, or aromatic. Unless otherwise specified, the term “cyclic” includes single rings, multiple non-fused rings, fused rings, bridged rings, and combinations thereof.

[0031] The expression “wherein any carbon ... is optionally independently replaced by N, S, or O” and other similar expressions means that the defined hydrocarbon (e.g. “alkyl”,“alkylenyl”, “alkenylenyl”, or “alkynylenyl”) includes zero, one, more than one, or any reasonable combination of two or more heteroatoms selected from N, S, and O. The above expression therefore expands the defined hydrocarbon to additionally encompass heteroalkyls, heteroalkylenyls, heteroalkenylenyls, and heteroalkynylenyls, etc. A person of skill in the art would understand that various combinations of different heteroatoms may be used. The expression “wherein any carbon bonded to two other carbons is optionally independently replaced by N, S, or O” and other similar expressions means that any carbon in the defined hydrocarbon bonded to two other carbons (e.g. the underlined carbon in -C-C-C-), whether those bonds are single, double, or triple bonds, may be a heteroatom, but excludes heteroatoms bonded to other heteroatoms (e.g. excludes -C-N-S-, -S-S-N-, -N-S-C-, and the like).

[0032] Various R-groups (e.g. R1, R2, R3, etc.) and L-groups (e.g. L1, L2, L3, etc.) are defined in this disclosure. L-groups generally refer to linkages (-N(alkyl)-C(O)-, -C(O)-N(alkyl)-, -NH-C(O)-NH-,

[0033] If unspecified, the size of an R-group or L-group is what would be considered reasonable to a person of skill in the art. For example, but without limitation, if unspecified, the size of an alkyl may be 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 , 12, 13, 14, 15, 16, 17, 18, 19, 20, 21 , 22, 23, 24, 25, 26, 27, 28, 29, 30, 31 , 32, 33, 34, 35, 36, 37, 38, 39, 40, 41 , 42, 43, 44, 45, 46, 47,48, 49, 50, 51 , 52, 53, 54, 55, 56, 57, 58, 59, 60, 61 , 62, 63, 64, 65, 66, 67, 68, 69, 70, 71 , 72,73, 74, 75, 76, 77, 78, 79, 80, 81 , 82, 83, 84, 85, 86, 87, 89, 90, 91 , 92, 93, 94, 95, 96, 97, 98, 99, 100 or more than 100 carbons in length, subject to the common general knowledge of the person of skill in the art. Further, but without limitation, if unspecified, the size of a heteroalkyl may be 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 , 12, 13, 14, 15, 16, 17, 18, 19, 20, 21 , 22, 23, 24, 25, 26, 27, 28, 29, 30, 31 , 32, 33, 34, 35, 36, 37, 38, 39, 40, 41 , 42, 43, 44, 45, 46, 47, 48, 49, 50, 51 , 52, 53, 54, 55, 56, 57, 58, 59, 60, 61 , 62, 63, 64, 65, 66, 67, 68, 69, 70, 71 , 72, 73, 74, 75, 76, 77, 78, 79, 80, 81 , 82, 83, 84, 85, 86, 87, 89, 90, 91 , 92, 93, 94, 95, 96, 97, 98, 99, 100 or more than 100 carbons and heteroatoms in length, subject to the common general knowledge of the person of skill in the art. In the context of the expression “alkyl, alkenyl or alkynyl” and similar expressions, the “alkyl” would be understood to be a saturated alkyl, and the “alkenyl” and the “alkynyl” would be understood to be unsaturated.

[0034] As used herein, in the context of an alkyl / heteroalkyl group of a compound, the term “linear” may be used as it is normally understood to a person of skill in the art and generallyrefers to a chemical entity that comprises a skeleton or main chain that does not split off into more than one contiguous chain. Non-limiting examples of linear alkyls include methyl, ethyl, n-propyl, and n-butyl.

[0035] As used herein, the term “branched” may be used as it is normally understood to a person of skill in the art and generally refers to a chemical entity that comprises a skeleton or main chain that splits off into more than one contiguous chain. The portions of the skeleton or main chain that split off in more than one direction may be linear, cyclic or any combination thereof. Non-limiting examples of a branched alkyl group include tert-butyl and isopropyl.

[0036] The term “alkylenyl” refers to a divalent analog of an alkyl group. In the context of the expression “alkylenyl, alkenylenyl and / or alkynylenyl”, and similar expressions, the “alkylenyl” would be understood to be a saturated alkylenyl, and the “alkenylenyl” and the “alkynylenyl” would be understood to be unsaturated. The term “heteroalkylenyl” refers to a divalent analog of a heteroalkyl group. The term “heteroalkenylenyl” refers to a divalent analog of a heteroalkenyl group. The term “heteroalkynylenyl” refers to a divalent analog of a heteroalkynyl group.

[0037] As used herein, the term “saturated” when referring to a chemical entity may be used as it is normally understood to a person of skill in the art and generally refers to a chemical entity that comprises only single bonds, and may include linear, branched, and / or cyclic groups. Non-limiting examples of a saturated C1-C20 alkyl group may include methyl, ethyl, n-propyl, i-propyl, sec-propyl, n-butyl, i-butyl, sec-butyl, t-butyl, n-pentyl, i-pentyl, sec-pentyl, t-pentyl, n-hexyl, i-hexyl, 1 ,2-dimethylpropyl, 2-ethylpropyl, 1-methyl-2-ethylpropyl, l-ethyl-2-methylpropyl, 1 , 1 ,2-trimethylpropyl, 1 ,1 ,2-triethylpropyl, 1 ,1 -dimethylbutyl, 2,2-dimethylbutyl, 2-ethylbutyl, 1 ,3-dimethylbutyl, 2-methylpentyl, 3-methylpentyl, sec-hexyl, t-hexyl, n-heptyl, i-heptyl, sec-heptyl, t-heptyl, n-octyl, i-octyl, sec-octyl, t-octyl, n-nonyl,1-nonyl, sec-nonyl, t-nonyl, n-decyl, i-decyl, sec-decyl, t-decyl, cyclopropanyl, cyclobutanyl, cyclopentanyl, cyclohexanyl, cycloheptanyl, cyclooctanyl, cyclononanyl, cyclodecanyl, and the like. Unless otherwise specified, a C1-C20 alkylenyl therefore encompasses, without limitation, all divalent analogs of the above-listed saturated alkyl groups.

[0038] As used herein, the term “unsaturated” when referring to a chemical entity may be used as it is normally understood to a person of skill in the art and generally refers to a chemical entity that comprises at least one double or triple bond, and may include linear, branched, and / or cyclic groups. Non-limiting examples of a C2-C20 alkenyl group may include vinyl, allyl, isopropenyl, l-propene-2-yl, 1-butene-l-yl, l-butene-2-yl, l-butene-3-yl, 2-butene-l-yl,2-butene-2-yl, octenyl, decenyl, cyclopropenyl, cyclobutenyl, cyclopentenyl, cyclohexenyl, cycloheptenyl, cyclooctenyl, cyclononanenyl, cyclodecanenyl, and the like. Unless otherwise specified, a C1-C20 alkenylenyl therefore encompasses, without limitation, all divalent analogs of the above-listed alkenyl groups. Non-limiting examples of a C2-C20 alkynyl group mayinclude ethynyl, propynyl, butynyl, pentynyl, hexynyl, heptynyl, octynyl, nonynyl, decynyl, and the like. Unless otherwise specified, a C1-C20 alkynylenyl therefore encompasses, without limitation, all divalent analogs of the above-listed alkynyl groups.

[0039] Non-limiting examples of non-aromatic cyclic groups include cylcopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and the like. Non-limiting examples of non-aromatic heterocyclic groups include aziridinyl, azetidinyl, diazetidinyl, pyrrolidinyl, pyrrolinyl, piperidinyl, piperazinyl, imidazolinyl, pyrazolidinyl, imidazolydinyl, phthalimidyl, succinimidyl, oxiranyl, tetrahydropyranyl, oxetanyl, dioxanyl, thietanyl, thiepinyl, morpholinyl, oxathiolanyl, and the like.

[0040] Unless further specified, an “aryl” group includes both single aromatic rings as well as fused rings containing at least one aromatic ring, non-limiting examples of C3-C20 aryl groups include phenyl (Ph), pentalenyl, indenyl, naphthyl and azulenyl. Non-limiting examples of aromatic heterocyclic groups of similar size include pyrrolyl, imidazolyl, pyrazolyl, pyridinyl, pyridazinyl, pyrimidinyl, pirazinyl, quinolinyl, isoquinolinyl, acridinyl, indolyl, isoindolyl, indolizinyl, purinyl, carbazolyl, indazolyl, phthalazinyl, naphthyridinyl, quinoxalinyl, quinazolinyl, cinnolinyl, pteridinyl, phenanthridinyl, phenazinyl, phenanthrolinyl, perimidinyl, furyl, dibenzofuryl, xanthenyl, benzofuryl, thiophenyl, thianthrenyl, benzothiophenyl, phosphorinyl, phosphinolinyl, phosphindolyl, thiazolyl, oxazolyl, isoxazolyl, and the like.

[0041] As used herein, the term “substituted” is used as it would normally be understood to a person of skill in the art and generally refers to a compound or chemical entity that has one chemical group replaced with a different chemical group. Unless otherwise specified, a substituted alkyl, alkylenyl, alkenylenyl, or alkynylenyl has one or more hydrogen atom(s) independently replaced with an atom that is not hydrogen. For example, chloromethyl is a non-limiting example of a substituted alkyl, more particularly an example of a substituted methyl. Aminoethyl is another non-limiting example of a substituted alkyl, more particularly an example of a substituted ethyl. Unless otherwise specified, a substituted compound or group (e.g. R-group or L-group) may be substituted with any chemical group reasonable to a person of skill in the art. For example, but without limitation, a hydrogen bonded to a carbon or heteroatom (e.g. N) may be substituted with halide (e.g. F, I, Br, Cl), amine, amide, oxo, hydroxyl, thiol, phosphate, phosphonate, sulfate, SO2H, SO3H, alkyls, heteroalkyls, aryl, heteroaryl, ketones, carboxaldehyde, carboxylates, carboxamides, nitriles, monohalomethyl, dihalomethyl or trihalomethyl. In som embodiments, each carbon may be independently substituted or unsubstituted with oxo, hydroxyl, sulfhydryl, amine, amide, urea, halogen, guanidino, carboxylic acid, sulfonic acid, sulfinic acid, or phosphoric acid. In some embodiments, the amide substituent is -C(O)-NH2.

[0042] As used herein, the term “unsubstituted” is used as it would normally be understood to a person of skill in the art. Non-limiting examples of unsubstituted alkyls include methyl, ethyl,tert-butyl, pentyl and the like. The expression “optionally substituted” is used interchangeably with the expression “unsubstituted or substituted”. The expression “optionally independently substituted” means that each location may be substituted or may not be substituted, and when substituted each substituent may be the same or different.

[0043] In the structures provided herein, hydrogen may or may not be shown. In some embodiments, hydrogens (whether shown or implicit) may be protium (i.e.1H), deuterium (i.e.2H) or combinations of1H and2H. Methods for exchanging1H with2H are well known in the art. For solvent-exchangeable hydrogens, the exchange of1H with2H occurs readily in the presence of a suitable deuterium source, without any catalyst. The use of acid, base or metal catalysts, coupled with conditions of increased temperature and pressure, can facilitate the exchange of non-exchangeable hydrogen atoms, generally resulting in the exchange of all1H to2H in a molecule.

[0044] The term “Xaa” refers to an amino acid residue in a peptide chain or an amino acid that is otherwise part of a compound. Amino acids have both an amino group and a carboxylic acid group, either or both of which can be used for covalent attachment. In attaching to the remainder of the compound, the amino group and / or the carboxylic acid group may be converted to an amide or other structure; e.g. a carboxylic acid group of a first amino acid is converted to an amide (i.e. a peptide bond) when bonded to the amino group of a second amino acid. As such, Xaa may have the formula -N(Ra)RbC(O)-, where Raand Rbare R-groups. Rawill typically be hydrogen or alkyl (e.g. methyl) or Raand Rbmay form a cyclic structure. The amino acid residues of a peptide may comprise typical peptide (amide) bonds and may further comprise bonds between side chain functional groups and the side chain or main chain functional group of another amino acid. For example, the side chain carboxylate of one amino acid residue in the peptide (e.g. Asp, Glu, etc.) may be bonded to and the amine of another amino acid residue in the peptide (e.g. Dap, Dab, Orn, Lys). Further details are provided below. Unless otherwise indicated, “Xaa” may be any amino acid, including a proteinogenic or nonproteinogenic amino acid. Non-limiting examples of nonproteinogenic amino acids are shown in Table A and include: D-amino acids (including without limitation any D-form of the following amino acids), ornithine (Orn), 3-(1-naphtyl)alanine (Nal),3-(2-naphtyl)alanine (2-Nal), a-aminobutyric acid, norvaline, norleucine (Nle), homonorleucine, beta-(1 ,2,3-triazol-4-yl)-L-alanine, 1 ,2,4-triazole-3-alanine, Phe(4-F), Phe(4-CI), Phe(4-Br), Phe(4-I), Phe(4-NH2), Phe(4-NO2), homoarginine (hArg), 2-amino-4-guanidinobutyric acid (Agb), 2-amino-3-guanidinopropionic acid (Agp), B-alanine,4-aminobutyric acid, 5-aminovaleric acid, 6-aminohexanoic acid, 7-aminoheptanoic acid, 8-aminooctanoic acid, 9-aminononanoic acid, 10-aminodecanoic acid, 2-aminooctanoic acid, 2-amino-3-(anthracen-2-yl)propanoic acid, 2-amino-3-(anthracen-9-yl)propanoic acid, 2- amino-3-(pyren-1-yl)propanoic acid, Trp(5-Br), Trp(5-OCH3), Trp(6-F), Trp(5-OH) orTrp(CHO), 2-aminoadipic acid (2-Aad), 3-aminoadipic acid (3-Aad), propargylglycine (Pra), homopropargylglycine (Hpg), beta-homopropargylglycine (Bpg), 2,3-diaminopropionic acid (Dap), 2,4-diaminobutyric acid (Dab), azidolysine (Lys(N3)), azido-ornithine (Orn(N3)), 2-amino-4-azidobutanoic acid Dab(N3), Dap(N3), 2-(5'-azidopentyl)alanine, 2-(6'-azidohexyl)alanine, 4-amino-1-carboxymethyl-piperidine (Pip),4-(2-aminoethyl)-1-carboxymethyl-piperazine (Acp), tranexamic acid, tert-leucine (Tie), 4-chlorophenylalanine (Cpa), thiazoline-4-carboxylic acid (Thz), aMe-Trp, p-aminomethylaniline-diglycolic acid (pABzA-DIG), 4-amino-1-carboxymethyl-piperidine (Pip), NH2(CH2)2O(CH2)2C(O)OH, NH2(CH2)2[O(CH2)2]2C(O)OH (dPEG2),NH2(CH2)2[O(CH2)2]3C(O)OH, NH2(CH2)2[O(CH2)2]4C(O)OH, NH2(CH2)2[O(CH2)2]5C(O)OH, NH2(CH2)2[O(CH2)2]6C(O)OH, oxazolidine-4-carboxylic acid (4- oxa- L- Pro), 4,4-difluoroproline (diFPro), statine (Sta), |3-(3-benzothienyl)alanine (Bta), citrulline (Cit), Trp(Me), Trp (7-Me), Trp(6-Me), Trp(5-Me), Trp(4-Me), Trp(2-Me), Trp(7-F), Trp(5-F), Trp(4-F) or cyclopentylglycine (Cpa). If not specified as an L- or D-amino acid, an amino acid shall be understood to be an L-amino acid.

[0045] TABLE A. List of non-limiting examples of non-proteinogenic amino acids.

[0046] The wavy line “-~w ” symbol shown through or at the end of a bond in a chemical formula (e.g. in the definitions L1or RAof Formula I) is intended to define the group on one side of the wavy line, without modifying the definition of the structure on the opposite side of the wavy line. Where an R-group or L-group is bonded on two or more sides, any atoms shown outside the wavy lines are intended to clarify orientation of the defined group. As such, only the atoms between the two wavy lines constitute the definition of the R-group or L-group. When atoms are not shown outside the wavy lines (e.g. L1), or for a chemical group shown without wavy lines but does have bonds on multiple sides (e.g. -C(O)NH-, and the like), the chemical group should be read from left to right matching the orientation in the formula that the group relates to; e.g. for formula -Ra-Rb-Rc-, the definition of Rbas -C(O)NH- would be incorporated into the formula as -Ra-C(O)NH-Rc- not as -Ra-NHC(O)-Rc-

[0047] Compounds

[0048] To minimize the pancreas uptake, series of bombesin analogs by modifying C-terminal Leu13-Met14have been developed, where some of the analogs showed significantly lower pancreas uptake. See, Rousseau, E. et al. Journal of Labelled Compounds and Radiopharmaceuticals 63, 56-64 (2020), Lau, J. et al. ACS omega 4, 1470-1478 (2019), and Bratanovic, I. J. et al. J. of Nuclear Medicine, jnumed.120.257758, doi:10.2967 / jnumed.120.257758 (2021), each of which is hereby incorporated by reference in its entirety for all purposes. Based on these data, bombesin(7-14) sequence was modified with Leu13-Thz14(Thz: thiazoline-4-carboxylic acid) with a hypothesis that it would decrease pancreas uptake. It was also hypothesized that GRPR-targeting radioligands with good binding affinity and low pancreas uptake could be obtained by modifying the GRP(20-27) sequence with Leu13qjThz14. See Reile, H. et al. International journal of oncology 7 , 749-754 (1995). To this end, unnatural amino acids were introduced into the sequence, particularly at the cleavage sites. The hypothesis for substituting the amino acids at the cleavage sites with unnatural amino acids was that it would improve in vivo metabolic stability of the tracers.

[0049] In some embodiments, the present disclosure relates to a peptidic compound of Formula (I), or a salt or solvate thereof, optionally complexed with a radioisotope (e.g., a radiometal or a radiohalogen):Rradn6-[linker]-RL-Xaa1-Xaa2-Xaa3-Xaa4-Xaa5-Xaa6-Xaa7-Xaa8-(qj-Xaa9)m-R(I) wherein:Xaa1is an N-terminal amino acid residue selected from D-Phe, 4-chlorophenylalanine (Cpa), D-Cpa, 3-(1-naphthyl)alanine (Nal), D-Tpi, D-Nal, 3-(2-naphthyl)alanine (2-Nal), or D-2-Nal;Xaa2is Asn, Gin, homoserine (Hse), citrulline (Cit) or His;Xaa3is Trp, |3-(3-benzothienyl)alanine (Bta), Trp(Me), Trp(7-Me), Trp(6-Me), Trp(5-Me), Trp(4-Me), Trp(2-Me), Trp(7-F), Trp(6-F), Trp(5-F), Trp(4-F), Trp(5-0H), Tpi, 7-Aza, or aMe-Trp;Xaa4is Ala or Ser;Xaa5is Vai, 2,3-dehydro-Val, Cpg (cyclopentylglycine), L-cyclopropylglycine, L-cyclobutylg lycine, or tert-leucine (Tie);Xaa6is Gly, NMe-Gly, or D-Ala;Xaa7is His or NMe-His;R is -NH2or -NHOH; m is 0 or 1 ; when m is 0, Xaa8-R is a C-terminally amidated (R is -NH2) or a C-terminally hydroxylamidated (R is -NHOH) amino acid residue selected from statine (Sta), Leu, D-Pro, or Phe; when m is 1 , Xaa8is statine (Sta), Leu, D-Pro, or Phe; and Xaa9-R is aC-terminally amidated (R is -NH2) or a C-terminally hydroxylamidated (R is -NHOH) amino acid residue selected from Pro, Phe, oxazolidine-4-carboxylic acid (4-oxa-L-Pro),4,4-difluoroproline (difluoroPro), Leu, Me2Thz (5,5-dimethyl-1 ,3-thiazolidine-4-carboxylic acid), or thiazoline-4-carboxylic acid (Thz); qj represents a peptide bond or reduced peptide bond joining Xaa8to Xaa9;RLis -C(O)-, -NH-C(O)-, or -NH-C(S)-; the linker is a linear or branched chain of n1 units of -L1R1- and / or -(L1)2R1-, wherein: n1 is 1-20; each R1is, independently, a linear, branched, and / or cyclic Cn2alkylenyl, alkenylenyl and / or alkynylenyl, wherein each n2 is independently 1-20, wherein any carbon bonded to two other carbons is optionally independently replaced by N, S, or O, and carbons are optionally independently substituted with oxo, hydroxyl, sulfhydryl, -SeH, halogen, guanidino, amine, amide, urea, carboxylic acid, sulfonic acid, sulfinic acid, or phosphoric acid;L1bonds to carbon, wherein each L1is independently -S-, -N(R2)C(O)-,R2is H, methyl or ethyl;an albumin binder (Ralb) is optionally bonded to an L1of the linker, wherein the albumin binder is:-(CH2)n3-CH3wherein n3 is 8-20; H wherein n4 is 8-20;wherein n5 is 1-4 and R3ais H or methyl, and R3bis I, Br, F, Cl, H, OH, OCH3, NH2, NO2or Ci-C6alkyl; orn6 is 1-5; each Rradis a radiolabeling group bonded to or incorporating an L1of the linker, wherein each radiolabeling group is independently: a radiometal chelator wherein the radiometal chelator is optionally bound to a radiometal, a radionuclide-bound metal, or a radionuclide-bound metal-containing prosthetic group; an aryl or heteroaryl substituted with a radiohalogen; a prosthetic group containing a trifluoroborate; a prosthetic group containing a silicon-fluorine-acceptor moiety; or a prosthetic group containing a fluorophosphate, fluorosulfate, sulfonyl fluoride, or a combination thereof; and wherein Xaa1, Xaa2, Xaa3, Xaa4, Xaa5, Xaa6, Xaa7, Xaa8, or Xaa9is each optionally methylated.

[0050] In some embodiment of the peptidic compound:(i) Xaa3is Trp(7-F) and Xaa9-R is a C-terminally amidated Pro or diFPro;(ii) qj represents a reduced peptide bond, m is 1 , Xaa3is |3-(3-benzothienyl)alanine (Bta), Trp(Me), Trp(7-Me), Trp(6-Me), Trp(5-Me), Trp(4-Me), Trp(2-Me), Trp(7-F), Trp(6-F), Trp(5-F), Trp(4-F), Trp(5-OH), Tpi, 7-Aza, or aMe-Trp, and Xaa9-R is a C-terminally amidated Pro or diFPro.

[0051] In some embodiment of the peptidic compound, Xaa3is Trp(7-F); Xaa6is NMe-Gly; and Xaa9-R is a C-terminally amidated Pro or diFPro. In embodiments, Xaa3is Trp(7-F); Xaa6is Gly or NMe-Gly; and Xaa9-R is a C-terminally amidated Pro. In embodiments, Xaa3is Trp(7-F); Xaa6is Gly or NMe-Gly; and Xaa9-R is a C-terminally amidated diFPro.

[0052] In some embodiment of the peptidic compound, Xaa3is Trp(7-F); Xaa5is Tie; and Xaa9-R is a C-terminally amidated Pro or diFPro. In embodiments, Xaa3is Trp(7-F); Xaa5is Vai or Tie; and Xaa9-R is a C-terminally amidated Pro. In embodiments, Xaa3is Trp(7-F); Xaa5is Vai or Tie; and Xaa9-R is a C-terminally amidated diFPro.

[0053] In some embodiment of the peptidic compound, m is 1

[0054] In some embodiment of the peptidic compound, qj represents a reduced peptide bond.

[0055] In some embodiment of the peptidic compound, Xaa1is an N-terminal amino acid residue selected from D-Phe.

[0056] In some embodiment of the peptidic compound, Xaa2is Gin.

[0057] In some embodiment of the peptidic compound, Xaa3is Trp(7-F).

[0058] In some embodiment of the peptidic compound, Xaa4is Ala.

[0059] In some embodiment of the peptidic compound, Xaa5is Vai or Tie.

[0060] In some embodiment of the peptidic compound, Xaa6is Gly or NMe-Gly.

[0061] In some embodiment of the peptidic compound, Xaa7is His.

[0062] In some embodiment of the peptidic compound, Xaa8is Leu.

[0063] In some embodiment of the peptidic compound, Xaa9-R is a C-terminally amidated Pro or diFPro.

[0064] In some embodiment of the peptidic compound, Xaa1is an N-terminal amino acid residue selected from D-Phe; Xaa2is Gin; Xaa4is Ala; Xaa5is Vai or Tie; Xaa6is Gly or NMe-Gly; Xaa8is Leu; and Xaa9-R is a C-terminally amidated Pro or diFPro.

[0065] In some embodiment of the peptidic compound, Xaa1is an N-terminal amino acid residue selected from D-Phe; Xaa2is Gin; Xaa3isTrp(7-F); Xaa4is Ala; Xaa5is Vai or Tie; Xaa6is Gly or NMe-Gly; Xaa8is Leu; Xaa7is His; Xaa8is Leu; and Xaa9-R is a C-terminally amidated Pro or diFPro.

[0066] In some embodiment of the peptidic compound, Xaa1is an N-terminal amino acid residue selected from D-Phe; Xaa2is Gin; Xaa3isTrp(7-F); Xaa4is Ala; Xaa5is Vai or Tie; Xaa6is Gly or NMe-Gly; Xaa8is Leu; Xaa7is His; Xaa8is Leu; Xaa9-R is a C-terminally amidated Pro or diFPro; m is 1 ; and qj represents a reduced peptide bond.

[0067] In some embodiment of the peptidic compound, Xaa1is an N-terminal amino acid residue selected from D-Phe; Xaa2is Gin; Xaa3isTrp(7-F); Xaa4is Ala; Xaa5is Vai or Tie; Xaa6is Gly or NMe-Gly; Xaa8is Leu; Xaa7is His; Xaa8is Leu; Xaa9-R is a C-terminally amidatedPro; m is 1 ; and qj represents a reduced peptide bond.

[0068] In some embodiments, the peptidic compound is, or a salt or a solvate thereof, wherein the compound is optionally conjugated by a radiometal, a radionuclide-bound metal, or a radionuclide-bound metal-containing prosthetic group. In some embodiments, the peptidic compound is conjugated by a radiometal.

[0069] In various aspects, there is disclosed a peptidic compound, wherein the compound has the structure of Formula IA or is a salt or solvate of Formula IA defined as follows, optionally complexed with a radioisotope (e.g., a radiometal or a radiohalogen):Rradn6-[linker]-RL-Xaa1-Xaa2-Xaa3-Xaa4-Xaa5-Xaa6-Xaa7-Xaa8-qj-Xaa9-R(IA) wherein:Xaa1is an N-terminal amino acid residue selected from D-Phe, Cpa (4-chlorophenylalanine), D-Cpa, Nal (3-(1-naphthyl)alanine), D-Nal, 2-Nal (3-(2-naphthyl)alanine), or D-2-Nal;Xaa2is Asn, Gin, homoserine (Hse), citrulline (Cit) or His;Xaa3is Trp, |3-(3-benzothienyl)alanine (Bta), Trp(Me), Trp(7-Me), Trp(6-Me), Trp(5-Me), Trp(4-Me), Trp(2-Me), Trp(7-F), Trp(6-F), Trp(5-F), Trp(4-F), Trp(5-OH) or aMe-Trp;Xaa4is Ala or Ser;Xaa5isVal, Cpg (cyclopentylglycine) or tert-leucine (Tie);Xaa6is Gly, NMe-Gly, or D-Ala;Xaa7is His or NMe-His;Xaa8is Sta, Leu, D-Pro, or Phe;R is -NH2or -NHOH;Xaa9-R is a C-terminally amidated or hydroxylamidated amino acid residue selected from Pro, Phe, 4-oxa-L-Pro (oxazolidine-4-carboxylic acid), diFPro, Leu, Me2Thz (5,5-dimethyl-1 ,3-thiazolidine-4-carboxylic acid), or Thz (thiazoline-4-carboxylic acid); qj is a peptide bond or reduced peptide bond between Xaa8and Xaa9;RLis -C(O)-, -NH-C(O)-, or -NH-C(S)-; the linker is a linear or branched chain of n1 units of -L1R1- and / or -(L1)2R1-, wherein: n1 is 1-20; each R1is, independently, a linear, branched, and / or cyclic Cn2alkylenyl, alkenylenyl and / or alkynylenyl, wherein each n2 is independently 1-20, wherein any carbon bonded to two other carbons is optionally independently replaced by N, S, or O, and carbons are optionally independently substituted with oxo, hydroxyl, sulfhydryl, -SeH, halogen, guanidino, amine, amide, urea, carboxylic acid, sulfonic acid, sulfinic acid, or phosphoric acid;L1bonds to carbon, wherein each L1is independently -S-, -N(R2)C(O)-,R2is H, methyl or ethyl; and an albumin binder (Ralb) is optionally bonded to an L1of the linker, wherein the albumin binder is:-(CH2)n3-CH3wherein n3 is 8-20; H wherein n4 is 8-20;wherein n5 is 1-4 and R3ais H or methyl, and R3bis I, Br, F, Cl, H, OH, OCH3, NH2, NO2or Ci-C6alkyl; orn6 is 1-5; and each Rradis a radiolabeling group bonded to or incorporating an L1of the linker, wherein each radiolabeling group is independently: a radiometal chelator wherein the radiometal chelator is optionally bound to a radiometal, a radionuclide-bound metal, or a radionuclide-bound metal-containing prosthetic group; an aryl or heteroaryl substituted with a radiohalogen; a prosthetic group containing a trifluoroborate; a prosthetic group containing a silicon-fluorine-acceptor moiety; or a prosthetic group containing a fluorophosphate, fluorosulfate, sulfonyl fluoride, or a combination thereof.

[0070] In one embodiment of the peptidic compound of formula (IA), the compound does not have the combination in which Xaa2, Xaa3, Xaa5, and Xaa7are Gin, Trp, Vai, and His, respectively, and qj is a reduced peptide bond.

[0071] In another embodiment, the peptidic compound may be a compound with the structure of Formula A or is a salt or solvate of Formula A as follows, optionally complexed with a radioisotope (e.g., a radiometal or a radiohalogen):Rradn6-[linker]-RL-Xaa1-Xaa2-Xaa3-Xaa4-Xaa5-Xaa6-Xaa7-Xaa8-qj-Xaa9-R (Formula A) wherein:Xaa1is an N-terminal amino acid residue selected from D-Phe, 4-chlorophenylalanine (Cpa), D-Cpa, 3-(1-naphthyl)alanine (Nal), D-Tpi, D-Nal, 3-(2-naphthyl)alanine (2-Nal), or D-2-Nal;Xaa2is Asn, Gin, homoserine (Hse), citrulline (Cit) or His;Xaa3is Trp, |3-(3-benzothienyl)alanine (Bta), Trp(Me), Trp(7-Me), Trp(6-Me), Trp(5-Me), Trp(4-Me), Trp(2-Me), Trp(7-F), Trp(6-F), Trp(5-F), Trp(4-F), Trp(5-OH), Tpi, 7-Aza, or aMe-Trp;Xaa4is Ala or Ser;Xaa5is Vai, 2,3-dehydro-Val, Cpg (cyclopentylglycine), cyclopropylglycine, cyclobutylglycine, or tert-leucine (Tie);Xaa6is Gly, NMe-Gly, or D-Ala;Xaa7is His or NMe-His;Xaa8is Sta, Leu, D-Pro, or Phe;R is -NH2or -NHOH;Xaa9-R is a C-terminally amidated or hydroxylamidated amino acid residue selected from Pro, Phe, oxazolidine-4-carboxylic acid (4-oxa-L-Pro), diFPro, Leu, Me2Thz (5,5-dimethyl-1 ,3-thiazolidine-4-carboxylic acid), or thiazoline-4-carboxylic acid (Thz); qj represents a peptide bond or reduced peptide bond joining Xaa8to Xaa9; excluding compounds in which Xaa2, Xaa3, Xaa5, and Xaa7are Gin, Trp, Vai, and His, respectively, in which qj is a reduced peptide bond;RLis -C(O)-, -NH-C(O)-, or -NH-C(S)-; the linker is a linear or branched chain of n1 units of -L1R1- and / or -(L1)2R1-, wherein:n1 is 1-20; each R1is, independently, a linear, branched, and / or cyclic Cn2 alkylenyl, alkenylenyl and / or alkynylenyl, wherein each n2 is independently 1-20, wherein any carbon bonded to two other carbons is optionally independently replaced by N, S, or O, and carbons are optionally independently substituted with oxo, hydroxyl, sulfhydryl, -SeH, halogen, guanidino, amine, amide, urea, carboxylic acid, sulfonic acid, sulfinic acid, or phosphoric acid;L1bonds to carbon, wherein each L1is independently -S-, -N(R2)C(O)-,ethyl; andan albumin binder (Ralb) is optionally bonded to an L1of the linker, wherein the albumin binder is:-(CH2)n3-CH3wherein n3 is 8-20; -(CH2)n4-C(O)OH wherein n4 is 8-20;n6 is 1-5; and each Rradis a radiolabeling group bonded to or incorporating an L1of the linker, wherein each radiolabeling group is independently: a radiometal chelator wherein the radiometal chelator is optionally bound to a radiometal, a radionuclide-bound metal, or a radionuclide-bound metal-containing prosthetic group; an aryl or heteroaryl substituted with a radiohalogen; a prosthetic group containing a trifluoroborate; a prosthetic group containing a silicon-fluorine-acceptor moiety; or a prosthetic group containing a fluorophosphate, fluorosulfate, sulfonyl fluoride, or a combination thereof.

[0072] In another embodiment, the invention may include a peptidic compound where Xaa1is an N-terminal amino acid residue selected from D-Phe, 4-chlorophenylalanine (Cpa), D-Cpa, 3-(1-naphthyl)alanine (Nal), D-Nal, 3-(2-naphthyl)alanine (2-Nal), or D-2-Nal; Xaa3is Trp, P-(3-benzothienyl)alanine (Bta), Trp(Me), Trp(7-Me), Trp(6-Me), Trp(5-Me), Trp(4-Me),Trp(2-Me), Trp(7-F), Trp(6-F), Trp(5-F), Trp(4-F), Trp(5-0H), or aMe-Trp; and Xaa5is Vai, Cpg (cyclopentylglycine), or tert-leucine (Tie).

[0073] In another specific embodiment, Xaa1is an N-terminal amino acid residue selected from D-Phe, or D-2-Nal. In another specific embodiment, Xaa2is Gin, or His. In another specific embodiment, Xaa5is Vai, or tert-leucine (Tie). In another specific embodiment, Xaa6is Gly, or NMe-Gly. In another specific embodiment, Xaa9-NH2is a C-terminally amidated amino acid residue selected from Pro or thiazoline-4-carboxylic acid (Thz). In another specific embodiment, Xaa1is an N-terminal amino acid residue selected from D-Phe, or D-2-Nal; Xaa2is Gin, or His; Xaa4is Ala; Xaa5is Vai, or tert-leucine (Tie); Xaa6is Gly, or NMe-Gly; Xaa8is Leu; and Xaa9-NH2is a C-terminally amidated amino acid residue selected from Pro or thiazoline-4-carboxylic acid (Thz). In another specific embodiment, Xaa1is an N-terminal amino acid residue selected from D-Phe or D-2-Nal; Xaa2is Gin or His; Xaa4is Ala; Xaa5is Vai or tert-leucine (Tie); Xaa6is Gly or NMe-Gly; Xaa7is His; Xaa8is Leu; Xaa9-NH2is a C-terminally amidated amino acid residue selected from Pro, diFPro, or thiazoline-4-carboxylic acid (Thz); and qj is a reduced peptide bond. In another specific embodiment, Xaa1is an N-terminal amino acid residue selected from D-Phe or D-2-Nal; Xaa2is Gin or His; Xaa4is Ala; Xaa5is Vai or tert-leucine (Tie); Xaa6is Gly or NMe-Gly; Xaa7is His; Xaa8is Leu; Xaa9-NH2is a C-terminally amidated amino acid residue selected from Pro, or diFPro; and qj is a reduced peptide bond.

[0074] In another specific embodiment, Xaa3is |3-(3-benzothienyl)alanine (Bta), Trp(Me), Trp(7-Me), Trp(6-Me), Trp(5-Me), Trp(4-Me), Trp(2-Me), Trp(7-F), Trp(6-F), Trp(5-F), Trp(4-F), Trp(5-OH), Tpi, 7-Aza, or aMe-Trp. Xaa3is Trp(7-F). In another specific embodiment, qj is a reduced peptide bond. In another specific embodiment, Xaa9is Thz. In another specific embodiment, Xaa2is His. In another specific embodiment, wherein Xaa3is Trp. In another specific embodiment, Xaa5is Tie. In another specific embodiment, Xaa7is NMe-His.

[0075] In another specific embodiment of the peptidic compounds described herein, qj is a reduced peptide bond; Xaa9is Pro or diFPro; Xaa2is Gin; Xaa3is Trp(7-F); Xaa5is Tie; and Xaa7is His. In another specific embodiment of the peptidic compounds described herein, qj is a reduced peptide bond; Xaa9is Pro or diFPro; Xaa2is Gin; Xaa3is Trp(7-F); Xaa5is Vai; and Xaa7is His.

[0076] In another embodiment, at least one of Xaa1, Xaa2, Xaa3, Xaa4, Xaa5, Xaa6, Xaa7, Xaa8, or Xaa9is methylated.

[0077] In another embodiment, the peptidic compounds of the present invention may have the structure of Formula B or is a salt or solvate of Formula B, wherein Formula B is as follows, optionally complexed with a radioisotope (e.g., a radiometal or a radiohalogen):Rradn6-[linker]-RL-Xaa1-Xaa2-Xaa3-Xaa4-Xaa5-Xaa6-Xaa7-Xaa8-qj-Xaa9-R (Formula B)wherein:Xaa1is an N-terminal amino acid residue selected from D-Phe, 4-chlorophenylalanine (Cpa), D-Cpa, 3-(1-naphthyl)alanine (Nal), D-Tpi, D-Nal, 3-(2-naphthyl)alanine (2-Nal), or D-2-Nal;Xaa2is Asn, Gin, homoserine (Hse), citrulline (Cit) or His;Xaa3is Trp, |3-(3-benzothienyl)alanine (Bta), Trp(Me), Trp(7-Me), Trp(6-Me), Trp(5-Me), Trp(4-Me), Trp(2-Me), Trp(7-F), Trp(6-F), Trp(5-F), Trp(4-F), Trp(5-OH), Tpi, 7-Aza, or aMe-Trp;Xaa4is Ala or Ser;Xaa5is Vai, 2,3-dehydro-Val, Cpg (cyclopentylglycine), cyclopropylglycine, cyclobuylglycine, or tert-leucine (Tie);Xaa6is Gly, NMe-Gly, or D-Ala;Xaa7is His or NMe-His;Xaa8is Sta, Leu, D-Pro, or Phe;R is -NH2or -NHOH;Xaa9-R is a C-terminally amidated amino acid residue selected from Pro, oxazolidine-4-carboxylic acid (4-oxa-L-Pro), diFPro, Leu, Me2Thz (5,5-dimethyl-1 ,3-thiazolidine-4-carboxylic acid), or thiazoline-4-carboxylic acid (Thz); qj represents a peptide bond or reduced peptide bond joining Xaa8to Xaa9;RLis -C(O)-, -NH-C(O)-, or -NH-C(S)-; the linker is a linear or branched chain of n1 units of -L1R1- and / or -(L1)2R1-, wherein: n1 is 1-20; each R1is, independently, a linear, branched, and / or cyclic Cn2alkylenyl, alkenylenyl and / or alkynylenyl, wherein each n2 is independently 1-20, wherein any carbon bonded to two other carbons is optionally independently replaced by N, S, or O, and carbons are optionally independently substituted with oxo, hydroxyl, sulfhydryl, -SeH, halogen, guanidino, amine, amide, urea, carboxylic acid, sulfonic acid, sulfinic acid, or phosphoric acid;L1bonds to carbon, wherein each L1is independently -S-, -N(R2)C(O)-,R2is H, methyl or ethyl; andan albumin binder (Ralb) is optionally bonded to an L1of the linker, wherein the albumin binder is:-(CH2)n3-CH3wherein n3 is 8-20; H wherein n4 is 8-20;wherein n5 is 1-4 and R3ais H or methyl, and R3bis I, Br, F, Cl, H, OH,OCH3, NH2, NO2or Ci-C6alkyl; orn6 is 1-5; and each Rradis a radiolabeling group bonded to or incorporating an L1of the linker, wherein each radiolabeling group is independently: a radiometal chelator wherein the radiometal chelator is optionally bound to a radiometal, a radionuclide-bound metal, or a radionuclide-bound metal-containing prosthetic group; an aryl or heteroaryl substituted with a radiohalogen; a prosthetic group containing a trifluoroborate; a prosthetic group containing a silicon-fluorine-acceptor moiety; or a prosthetic group containing a fluorophosphate, fluorosulfate, sulfonyl fluoride, or a combination thereof.

[0078] In a specific embodiment, the compounds of Formulas I, IA, A, or B do not comprise the albumin binder Ralbin the linker.

[0079] In a specific embodiment, at least one of Xaa1, Xaa2, Xaa3, Xaa4, Xaa5, Xaa6, Xaa7, Xaa8, or Xaa9is methylated. In another specific embodiment, qj is a reduced peptide bond joining Xaa8to Xaa9. In another specific embodiment, Xaa1is D-Phe; and / or Xaa6is Gly; and / or Xaa8is Leu; and / or Xaa9is Pro, Thz or 4-oxa-L-Pro. In another specific embodiment, Xaa6is Gly or N-methyl-Gly. In another specific embodiment, Xaa9is Thz. In another specific embodiment, Xaa9is Pro. In another embodiment, Xaa1is D-phe, Xaa2is Gin, Xaa3is Trp, Xaa4is Ala, Xaa5is Vai, Xaa6Xaa6is Gly or N-methyl-Gly, Xaa7is His, Xaa8is Leu, Xaa9is Thz, and qj is a reduced peptide bond joining Xaa8to Xaa9. In another specific embodiment, Xaa6is N-methyl-Gly.

[0080] In another specific embodiment, the peptidic compound is any compound from Formula I, IA, A, or B, wherein the compounds described in PCT application publication W02009 / 109332, which is incorporated by reference in its entirety herein, are excluded. In a specific embodiment, the peptidic compound is any compound from Formula B, wherein the compounds described in PCT application publication W02009 / 109332, which is incorporatedby reference in its entirety herein, are excluded. In another specific embodiment, the peptidic compound is any compound from Formula I, IA, A, or B, wherein the compounds described in PCT application publication W02021 / 068051 , which is incorporated by reference in its entirety herein, are excluded. In a specific embodiment, the peptidic compound is any compound from Formula B, wherein the compounds described in PCT application publication WO2021 / 068051 , which is incorporated by reference in its entirety herein, are excluded.

[0081] In a specific embodiment, the peptidic compound is any compound described in PCT application publication WO2021 / 068051 , which is incorporated by reference in its entirety herein.

[0082] In a specific embodiment, the peptidic compound is any compound from Formula B, wherein the compounds described in Wang, L et al., Molecules, 2022 27, 3777, which is incorporated by reference in its entirety herein, are excluded.

[0083] In a specific embodiment, the peptidic compound is any compound described in Wang, L et al., Molecules, 2022 27, 3777, which is incorporated by reference in its entirety herein.

[0084] In another specific embodiment, peptidic compounds of Formula I, IA, A, or B exclude Rradn6-[linker]-RL-, or Rradn6, or [linker] or RL-.

[0085] In another specific embodiment of the peptidic compounds described herein, the radiometal, the radionuclide-bound metal, or the radionuclide-bound metal-containing prosthetic group is:68Ga,61Cu,64Cu,67Ga,99mTc,110mln,111ln,44Sc,86Y,90Y,89Zr, "Nb,152Tb,155Tb, [18F]AIF,131l,123l,124l, and203Pb,72As.

[0086] In another specific embodiment of the peptidic compounds described herein, the radiometal, the radionuclide-bound metal, or the radionuclide-bound metal-containing prosthetic group is:165Er,212Bi,211At,166Ho,149Pm,159Gd,105Rh,109Pd,198Au,199Au,175Yb,142Pr,177Lu,111ln,213Bi,47Sc, "Y,225Ac,117mSn,153Sm,149Tb,161Tb,224Ra,223Ra,212Pb,227Th,223Ra,77As,186Re,188Re,67Cu, or64Cu.

[0087] In another specific embodiment, the compounds or peptidic compounds may be included in a pharmaceutical composition. In a specific embodiment, the pharmaceutical composition may include one or more compounds from Formula I, IA, A, or B and a pharmaceutically acceptable carrier. In another specific embodiment, the peptidic compound(s) may be bound to or include a radiometal. In a specific embodiment, the radiometal is165Er,212Bi,211At,166Ho,149Pm,159Gd,105Rh,109Pd,198Au,199Au,175Yb,142Pr,177Lu,111ln,213Bi,47Sc, "Y,225Ac,117mSn,153Sm,149Tb,161Tb,224Ra,223Ra,212Pb,227Th,223Ra,77As,186Re,188Re,67Cu, or64Cu.

[0088] In another embodiment, the invention may include using the peptidic compounds described herein for imaging methods. In a specific embodiment, the methods may include imaging Gastrin-releasing peptide receptor (GRPR) in a subject, the method comprising: administering to the subject a peptidic compound of any one of Formulas I, A or B; andimaging tissue of the subject. In a specific embodiment, the methods may include the methods of treating cancer in a subject comprising, administering to the subject in need thereof a peptidic compound of any one of Formulas I, A or B and a pharmaceutically acceptable excipient.

[0089] In another specific embodiment, the methods may include treating a GRPR-expressing condition or disease. In a specific embodiment, the GRPR-expressing condition or disease may be a psychiatric disorder, neurological disorder, inflammatory disease, prostate cancer, lung cancer, head and neck cancer, colon cancer, kidney cancer, ovarian cancer, liver cancer, pancreatic cancer, breast cancer, glioma or neuroblastoma. In some embodiments, the cancer is prostate cancer.

[0090] As described herein, the peptidic moiety -Xaa1-Xaa2-Xaa3-Xaa4-Xaa5-Xaa6-Xaa7-Xaa8-qj-Xaa9-R is the GRPR-targeting moiety of the compound; i.e. it is capable of specifically binding GRPR and potentially producing antagonist effects.

[0091] In some embodiments, Xaa1is D-Phe. In other embodiments, Xaa1is Cpa. In other embodiments, Xaa1is D-Cpa. In other embodiments, Xaa1is Nal. In other embodiments, Xaa1is D-Nal. In other embodiments, Xaa1is 2-Nal. In other embodiments, Xaa1is D-2-Nal. D-Phe at position Xaa1has been reported to retain binding affinity for GRPR (e.g. see: Lau, et al., 2019, ACS Omega 4:1470-1478). D-Cpa, Tpi, D-Tpi and D-Nal at position Xaa1have been reported to retain strong binding affinity for GRPR (e.g. see: Tables 1 and 3 in Cai et al., 1994 Proc. Natl. Acad. Sci. USA 91 :12664-12668; RC-3965-II disclosed in Reile et al., 1995 International Journal of Oncology 7:749-754). Since both L-Tpi and D-Tpi retain binding affinity, the L-isomers of D-Nal and D-Cpa would also retain strong binding affinity for GRPR.

[0092] In some embodiments, Xaa2is Asn. In other embodiments, Xaa2is Gin. In other embodiments, Xaa2is Hse. In other embodiments, Xaa2is Cit. In other embodiments, Xaa2is His. Gin at position Xaa2is found in wildtype BBN. His at position Xaa2is found in wildtype GRP. Hse and Cit at position Xaa2have been reported to retain binding affinity for GRPR (see Gunther, et al., 2021 , J Nucl Med. 62 (supplement 1) 1474).

[0093] In some embodiments, Xaa3is Trp. In other embodiments, Xaa3is Bta. In other embodiments, Xaa3is aMe-Trp. In other embodiments, Xaa3is Trp(Me). In other embodiments, Xaa3is Trp(7-Me). In other embodiments, Xaa3is Trp(6-Me). In other embodiments, Xaa3is Trp(5-Me). In other embodiments, Xaa3is Trp(4-Me). In other embodiments, Xaa3is Trp(2-Me). In other embodiments, Xaa3is Trp(7-F). In other embodiments, Xaa3is Trp(6-F). In other embodiments, Xaa3is Trp(5-F). In other embodiments, Xaa3is Trp(4-F). In other embodiments, Xaa3is Trp(5-OH). Trp at position Xaa3is found in wildtype BBN and GRP. Bta and aMe-Trp at position Xaa3have been reported to retain binding affinity for GRPR (see Gunther, et al., 2021 , Journal of Nuclear Medicine 62(supplement 1) 1474; Gunther, et al., J Nucl Med. 2022, jnumed.121 .263323; DOI: https: / / doi.org / 10.2967 / jnumed.121.263323).

[0094] In some embodiments, Xaa4is Ala. In other embodiments, Xaa4is Ser.

[0095] In some embodiments, Xaa5is Vai. In other embodiments, Xaa5is Cpg. In other embodiments, Xaa5is Tie. Vai in position Xaa5is found in wildtype BBN and GRP.

[0096] In some embodiments, Xaa6is Gly. In other embodiments, Xaa6is N-methyl-Gly. In other embodiments, Xaa6is D-Ala. N-methyl-Gly and D-Ala at position Xaa6have been reported to retain strong binding affinity for GRPR (e.g. see: Table 4 in Horwell et al., 1996 Int. J. Peptide Protein Res. 48:522-531 ; Table 3 in Lin et al., 1995 European Journal of Pharmacology 284:55-69).

[0097] In some embodiments, Xaa7is His. In other embodiments, Xaa7is NMe-His. His at position Xaa7is found in wildtype BBN and GRP. NMe-His at position Xaa7 has been reported to retain binding affinity for GRPR (e.g. see: Table 4 in Horwell et al., 1996 Int. J. Peptide Protein Res. 48:522-531).

[0098] In some embodiments, Xaa8is Leu. In other embodiments, Xaa8is D-Pro. In other embodiments, Xaa8is Phe. In some embodiments, Xaa8is Sta. Leu at position Xaa8is found in wildtype BBN and GRP. D-Pro at position Xaa8has been reported to retain binding affinity for GRPR (e.g. see: Leban, et al., 1994, J. Med. Chem. 37:439-445). Phe at position Xaa8is supported by Phe at this position in ranatensin and litorin, which have very strong binding affinity to the GRPR (Heimbrook et al., 1991 J. Med. Chem. 34:2102-2107; Lin et al., 1995 European Journal of Phamacology 294:55-69).

[0099] In some embodiments, Xaa9is Pro (i.e. Xaa9-R is C-terminally amidated or hydroxylamidated Pro). In some embodiments, Xaa9is diFPro (i.e. Xaa9-R is C-terminally amidated or hydroxylamidated diFPro). In other embodiments, Xaa9is Phe (i.e. Xaa9-R is C-terminally amidated or hydroxylamidated Phe). In other embodiments, Xaa9is 4-oxa-L-Pro (i.e. Xaa9R is C-terminally amidated or hydroxylamidated 4-oxa-L-Pro). In other embodiments, Xaa9is Leu (i.e. Xaa9-R is C-terminally amidated or hydroxylamidated Leu). In other embodiments, Xaa9is Me2Thz (i.e. Xaa9-R is C-terminally amidated or hydroxylamidated Me2Thz). In other embodiments, Xaa9is Thz (i.e. Xaa9-R is C-terminally amidated or hydroxylamidated Thz). Pro at position Xaa9has been reported to retain binding affinity for GRPR (e.g. see: Lau, et al., 2019, ACS Omega 4:1470-1478; WO / 2021 / 068051). Phe at position Xaa9has been reported to retain binding affinity for GRPR (e.g. see: Leban, et al., 1994, J. Med. Chem. 37:439-445). Thz at position Xaa9has been reported to retain binding affinity for GRPR (e.g. see: Cai, et al., 1994 Proc Natl Acad Sci USA 91 : 12664-12668).

[0100] In some embodiment, Xaa8is Sta and Xaa9is Leu (i.e. Xaa9-R is C-terminally amidated or hydroxylamidated Leu).

[0101] In some embodiments, Xaa8is Leu and Xaa9is diFPro (i.e. Xaa9-R is C-terminally amidated or hydroxylamidated diFPro).

[0102] In some embodiments, “qj” represents a peptide bond joining Xaa8and Xaa9. In other embodiments, “qj” represents a reduced peptide bond joining Xaa8and Xaa9, meaning o that the main chain amide (e.g.formed between Xaa8and Xaa9is replaced by

[0103] In some embodiments, -Xaa1-Xaa2-Xaa3-Xaa4-Xaa5-Xaa6-Xaa7-Xaa8-qj-Xaa9-R is -D-Phe-Gln-Trp(7-F)-Ala-Val-NMe-Gly-His-Leu-qj-Pro-NH2.

[0104] In some embodiments, -Xaa1-Xaa2-Xaa3-Xaa4-Xaa5-Xaa6-Xaa7-Xaa8-qj-Xaa9-R is -D-Phe-Gln-Trp(7-F)-Ala-Val-NMe-Gly-His-Leu-qj-diFPro-NH2.

[0105] In some embodiments, -Xaa1-Xaa2-Xaa3-Xaa4-Xaa5-Xaa6-Xaa7-Xaa8-qj-Xaa9-R is -D-Phe-Gln-Trp(7-F)-Ala-Tle-Gly-His-Leu-qj-Pro-NH2.

[0106] In some embodiments, -Xaa1-Xaa2-Xaa3-Xaa4-Xaa5-Xaa6-Xaa7-Xaa8-qj-Xaa9-R is -D-Phe-Gln-Trp(7-F)-Ala-Tle-Gly-His-Leu-qj-diFPro-NH2.

[0107] RLis a linkage moiety joining the linker to the N-terminus of Xaa1. In some embodiments, RLis -C(O)-. In other embodiments, RLis -NH-C(O)-. In yet other embodiments, RLis-NH-C(S)-.

[0108] The linker enables attachment of 1-5 radiolabelling groups, and optionally an albumin binder, to the compound.

[0109] A non-limiting example of a suitable linker is a peptide linker. More generally, the linker is a linear or branched chain of n1 units of -L1R1- and / or -(L1)2R1- (i.e. each unit is independently -L1R1- or — (L1)2R1— ), wherein n1 is 1-20. In alternative embodiments, n1 is 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 , 12, 13, 14, 15, 16, 17, 18, 19, or 20. In some embodiments, n1 is1-7. In some embodiments, n1 is 1 . In other embodiments, n1 is 2. In other embodiments, n1 is 3. In other embodiments, n1 is 4. In other embodiments, n1 is 5. In other embodiments, n1 is 6. In other embodiments, n1 is 7.

[0110] In some embodiments, n6 is 1 and n1 is 1.

[0111] In some embodiments, n6 is 1 , n1 is 1 , and L1is -C(O)NH-.

[0112] In some embodiments, n6 is 1 , n1 is 1 , L1is -C(O)NH-, and RLis -C(O)-.

[0113] In some embodiments, n6 is 1 , n1 is 1 , L1is -C(O)NH-, RLis -C(O)-, and R1is a linear C1.5 alkylenyl or -(CH2)2-[O(CH2)2]i.6-(CH2)0-2.

[0114] In some embodiments, Rradn6-[linker]- is configured as shown in Formula IIA:wherein L1and R1are as defined in the definition of the linker in Formula IA, and Rrad / albis either Rrador Ralb, and wherein 0-1 Rrad / albis Ralb.

[0115] Each R1(Formula I, IA or IIA) is, independently, a linear, branched, and / or cyclicCn2alkylenyl, alkenylenyl and / or alkynylenyl, wherein each n2 is independently 1-20, wherein any carbon bonded to two other carbons is optionally independently replaced by N, S, or O, and carbons are optionally independently substituted. In some embodiments, each n2 is independently 1-15 or 1-10. In alternative embodiments, each n2 is independently 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 , 12, 13, 14, 15, 16, 17, 18, 19, or 20. In some embodiments, each R1is independently a Cn2 alkylenyl wherein any carbon bonded to two other carbons is optionally independently replaced by N, S, or O, and carbons are optionally independently substituted. In some embodiments, each R1is independently a linear C1-5 alkylenyl or— (CH2)2— [O(CH2)2]I-6— (CH2)O-2— ; in some of these embodiments, n1 is 1-7. In some embodiments, each R1is independently -C(Raa)H-, wherein each Raais independently the sidechain of a proteinogenic amino acid or the sidechain of an alpha amino acid from Table A. In some embodiments, each R1is independently a proteinogenic amino acid or an amino acid from Table A omitting the backbone amino and carboxylic acid groups of the amino acid.

[0116] Each L1(Formula I, lA or IIA) is a linkage group. In some embodiments, at least one L1is -S-. In some embodiments, at least one L1is -N(R2)C(O)-; in some of these embodiments, at least one R2is hydrogen. In some embodiments, at least one L1is -C(O)N(R2)-; in some of these embodiments, at least one R2is hydrogen. In some embodiments, at least one L1is -NH-C(O)-NH-. In some embodiments, at least one L1is-NH-C(S)-NH-. In some embodiments, at least one L1In some embodiments, at least one L1is. In some embodiments, at least one L1is. In some embodiments, at least one L1is N=N

[0117] In some embodiments, the linker has the configuration shown in Formula IIA, and each R1is independently a linear C1-5 alkylenyl or -(CH2)2-[0(CH2)2]i-6-(CH2)o-2-.

[0118] In some embodiments, n6 is 1 , the linker is L1R1and together with RLforms -C(O)-Xaa11- wherein Xaa11is a proteinogenic amino acid residue or an amino acid residue selected from Table A. In some embodiments, Xaa11is pABzA-DIG. In other embodiments, Xaa11is Pip. In other embodiments, Xaa11is dPEG2. In other embodiments, Xaa11is Acp.

[0119] In some embodiments, the linker together with RLforms a peptide linker, wherein peptide (amide) bonds are independently optionally methylated, optionally replacing one or more amide bonds with 1 ,2,3-triazole linkages (product of a reaction between an azide and an alkyne). In some embodiments, the peptide linker is a linear peptide linker, optionally replacing one or more amide bonds with 1 ,2,3-triazole linkages. In some embodiments, the peptide linker is a branched peptide linker, where the amino acid residues may be connected through a combination of main chain amide (peptide) bonds and ‘side chain’-to-‘main chain’ or ‘side chain’-to-‘side chain’ bonds. For example, a branched peptide may be connected by one or more of: backbone (main chain) peptide (amide) bonds, ‘main chain’-to-side chain amide bonds (between an amino group and a carboxylic acid group), optionally replacing one or more amide bonds with 1 ,2,3-triazole linkages. In some such embodiments, the peptide linker is (Xaa1o)i-2o, wherein each Xaa10is independently a proteinogenic amino acid residue or a non-proteinogenic amino acid residue (e.g. selected from Table A) linked together as a linear or branched peptide linker. In some embodiments, (Xaa1o)i.2o is a linear peptide linker. In some embodiments, (Xaa1o)i.2o is a branched peptide linker. Rradis bonded to the peptide linker through an amide bond or another L1linkage group; in some embodiments, Rrad is bonded to the peptide linker through an amide bond.

[0120] In some embodiments, each Xaa10is independently -N(Ra)RbC(O)- wherein: Ramay be H or methyl; Rbmay be a 1- to 30-atom alkylenyl, heterolakylenyl, alkenylenyl, heteroalkenylenyl, alkynylenyl, or heteroalkynylenyl, including linear, branched, and / or cyclic (whether aromatic or nonaromatic as well as mono-cyclic, multicyclic or fused cyclic) structures; or N, Raand Rbtogether may form a 5- to 7-atom heteroalkylenyl or heteroalkenylenyl.

[0121] In some embodiments, (Xaa10)i.20consists of a single amino acid or residue. In some embodiments, (Xaa10)i.20is a dipeptide, wherein each Xaa10may be the same or different. In some embodiments, (Xaa10)i.20is a tripeptide, wherein each Xaa10may be the same, different or a combination thereof. In some embodiments, (Xaa10)i.20consists of 4 amino acid residues connected by peptide bonds, wherein each Xaa10may be the same, different or a combination thereof. In some embodiments, each Xaa10is independently selected from proteinogenic amino acids and the non-proteinogenic amino acids listed in Table A, wherein each peptide backbone amino group of the peptide linker is independently optionally methylated. In some embodiments, all peptide backbone amino groups of the peptide linker are methylated. In other embodiments, only one peptide backbone amino groupof the peptide linker is methylated. In other embodiments, only two peptide backbone amino groups of the peptide linker are methylated. In other embodiments, no peptide backbone amino groups of the peptide linker are methylated.

[0122] In some embodiments, n6 is 1. In other embodiments, n6 is 2. In other embodiments, n6 is 3. In other embodiments, n6 is 4. In other embodiments, n6 is 5.

[0123] In some embodiments, the linker does not comprise Ralb.

[0124] In some embodiments, the linker comprises Ralbbonded to an L1of the linker.

[0125] In some embodiments, Ralbis -(CH2)n3-CH3wherein n3 is 8-20. In alternative embodiments, n3 is 8, 9, 10, 1 1 , 12, 13, 14, 15, 16, 17, 18, 19, or 20.

[0126] In some embodiments, Ralbis -(CH2)n4-C(O)OH wherein n4 is 8-20. In alternative embodiments, n4 is 8, 9, 10, 1 1 , 12, 13, 14, 15, 16, 17, 18, 19, or 20.

[0127] In some embodiments, Ralbiswherein n5 is 1-4 and R3ais H or methyl, and R3bis I, Br, F, Cl, H, OH, OCH3, NH2, NO2or Ci-C6alkyl. In alternative embodiments, n5 is 1 , 2, 3, or 4. In certain embodiments, R3ais H. In certain embodiments, R3ais methyl. In certain embodiments, R3bis I, Br, F, or Cl, optionally in para position. In certain embodiments, R3bis H. In certain embodiments, R3bis OH, optionally in para position. In certain embodiments, R3bis OCH3, optionally in para position. In certain embodiments, R3bis NH2, optionally in para position In certain embodiments, R3bis NO2, optionally in para position. In certain embodiments, R3bis Ci-C6alkyl, optionally in para position. In certain embodiments, R3ais H and R3bis OCH3or NO2. In some embodiments, R3ais methyl and R3bis isobutyl, optionally para-isobutyl.

[0128] In some embodiments,

[0129] In some embodiments, at least one Rradis or comprises a radiometal chelator. The radiometal chelator may be any chelator suitable for binding a radiometal, a radionuclide-bound metal, or a radionuclide-bound metal-containing prosthetic group, and which is attached to the linker by forming an amide bond (between an amino group and a carboxylic acid group) or a 1 ,2,3-triazole (reaction between an azide and an alkyne), or by reaction between a maleimide and a thiol group. Many suitable radiometal chelators are known, e.g. as summarized in Price and Orvig, Chem. Soc. Rev., 2014, 43, 260-290. In some embodiments, but without limitation, each radiometal chelator is independently selected from the group consisting of: DOTA and DOTA derivatives; DOTAGA; NOTA; NODAGA; NODASA; CB-DO2A; 3p-C-DEPA; TCMC; DO3A; DTPA and DTPA analogues optionally selected fromCHX-A”-DTPA and 1 B4M-DTPA; TETA; NOPO; Me-3,2-HOPO; CB-TE1A1 P; CB-TE2P; MM-TE2A; DM-TE2A; sarcophagine and sarcophagine derivatives optionally selected from SarAr, SarAr-NCS, diamSar, AmBaSar, and BaBaSar; TRAP; AAZTA; DATA and DATA derivatives; H2-macropa or a derivative thereof; H2dedpa, H4octapa, H4py4pa, H4Pypa, H2azapa, H5decapa, and other picolinic acid derivatives; CP256; PCTA; C-NETA; C-NE3TA; HBED; SHBED; BCPA; CP256; YM103; desferrioxamine (DFO) and DFO derivatives; H6phospa; a trithiol chelate; mercaptoacetyl; hydrazinonicotinamide; dimercaptosuccinic acid; 1 ,2-ethylenediylbis-L-cysteine diethyl ester; methylenediphosphonate; hexamethylpropyleneamineoxime; and hexakis(methoxy isobutyl isonitrile). In some embodiments, at least one radiometal chelator is DOTA or a DOTA derivative.

[0130] Exemplary non-limiting examples of radiometal chelators and example radionuclides that may be chelated by these chelators are shown in Table B. In alternative embodiments, at least one Rradis a radiometal chelator selected from those listed above or in Table B. It is noted, however, that one skilled in the art could replace any of the chelators listed herein with another chelator.

[0131] TABLE B: Exemplary chelators and exemplary radionuclide which bind said chelators

[0132] In some embodiments, each radiometal chelator is independently selected from Table B, wherein each chelator is optionally bound by a radiometal. In some embodiments, each radiometal chelator is bound by one of the corresponding radionuclides shown in Table B.

[0133] In some embodiments, at least one Rradis DOTA, or a derivative thereof, linked via an amide (e.g. formed from one of the carboxyl groups shown in Table B. In some embodiments, at least one Rradis CB-DO2A, or a derivative thereof, linked via an amide (e.g. formed from one of the carboxyl groups shown in Table B). In some embodiments, at least one Rradis TCMC, or a derivative thereof, linked via an amide (e.g. formed from one of the -CONH2groups shown in Table B). In some embodiments, the chelator at least one Rradis 3p-C-DEPA, or a derivative thereof, linked via an amide (e.g. formed from one of the carboxyl groups shown in Table B). In some embodiments, at least one Rradis p-NH2-Bn-Oxo-D03A or a derivative thereof, linked via an amide (e.g. formed from one of the carboxyl groups shown in Table B). In some embodiments, at least one Rradis TETA, or a derivative thereof, linked via an amide (e.g. formed from one of the carboxyl groups shown in Table B). In some embodiments, at least one Rradis CB-TE2A, or a derivative thereof, linked via an amide (e.g.formed from one of the carboxyl groups shown in Table B). In some embodiments, at least one Rradis Diamsar, or a derivative thereof, linked via an amide (e.g. formed from one of the amino groups shown in Table B). In some embodiments, at least one Rradis NOTA, or a derivative thereof, linked via an amide (e.g. formed from one of the carboxyl groups shown in Table B). In some embodiments, at least one Rradis NETA, or a derivative thereof, linked via an amide (e.g. formed from one of the carboxyl groups shown in Table B). In some embodiments, at least one Rradis HxTSE, or a derivative thereof, linked via an amide (e.g. formed from one of the amino groups shown in Table B). In some embodiments, at least one Rradis P2N2Ph2, or a derivative thereof, linked via an amide (e.g. formed from one of the amino groups shown in Table B). In some embodiments, at least one Rradis DTPA, or a derivative thereof, linked via an amide (e.g. formed from one of the carboxyl groups shown in Table B). In some embodiments, at least one Rradis CHX-AOO-DTPA, or a derivative thereof, linked via an amide (e.g. formed from one of the carboxyl groups shown in Table B). In some embodiments, at least one Rradis H2dedpa, or a derivative thereof, linked via an amide (e.g. formed from one of the carboxyl groups shown in Table B). In some embodiments, at least one Rradis H2azapa, or a derivative thereof, linked via an amide (e.g. formed from one of the carboxyl groups shown in Table B). In some embodiments, at least one Rradis H4octapa, or a derivative thereof, linked via an amide (e.g. formed from one of the carboxyl groups shown in Table B). In some embodiments, at least one Rradis H6phospa, or a derivative thereof, linked via an amide (e.g. formed from one of the carboxyl groups shown in Table B). In some embodiments, at least one Rradis H4CHXoctapa, or a derivative thereof, linked via an amide (e.g. formed from one of the carboxyl groups shown in Table B). In some embodiments, at least one Rradis H5decapa, or a derivative thereof, linked via an amide (e.g. formed from one of the carboxyl groups shown in Table B). In some embodiments, at least one Rradis H4neunpa-p-Bn-NO2, or a derivative thereof, linked via an amide (e.g. formed from one of the carboxyl groups shown in Table B). In some embodiments, at least one Rradis SHBED, or a derivative thereof, linked via an amide (e.g. formed from one of the carboxyl groups shown in Table B). In some embodiments, at least one Rradis BPCA, or a derivative thereof, linked via an amide (e.g. formed from one of the carboxyl groups shown in Table B). In some embodiments, at least one Rradis PCTA, or a derivative thereof, linked via an amide (e.g. formed from one of the carboxyl groups shown in Table B). In some embodiments, at least one Rradis H2-MACROPA, or a derivative thereof, linked via an amide (e.g. formed from one of the carboxyl groups shown in Table B). In some embodiments, at least one Rradis Crown, or a derivative thereof, linked via an amide (e.g. formed from one of the carboxyl groups shown in Table B). In some embodiments, at least one Rradis HYNIC, or a derivative thereof, linked via an amide (e.g. formed from the carboxyl group shown in Table B). In some embodiments, at least one Rradis N4, or a derivative thereof, linked via an amide (e.g. formed from the carboxyl group shown in Table B). In some embodiments,at least one Rradis HBED-CC, or a derivative thereof, linked via an amide (e.g. formed from one of the carboxyl groups shown in Table B).

[0134] In some embodiments, the radiometal chelator (or one of the radiometal chelators) is a derivative of a radiometal chelator shown in Table B. A derivative may include, e.g. (1) modification of a functional group of the chelator (e.g. a carboxyl group, an amino group, etc.) or (2) attachment of a new functional group (e.g. attachment of an R-group to an ethylene carbon located between two nitrogen atoms, wherein the R-group is a functional group fused to a spacer). In some embodiments, a carboxyl functional group shown in Table B is replaced with azidopropyl ethylacetamide (e.g. azido-mono-amide-DOTA), butynylacetamide (e.g. butyne-DOTA), thioethylacetamide (e.g. D03A-thiol), maleimidoethylacetamide (e.g. maleimido-mono-amide-DOTA), or N-hydroxysuccinimide ester (e.g. DOTA-NHS-ester). When linked, these derivative chelators can be linked either via an amide (formed from a remaining carboxyl group) or via -C(0)-NH-(CH2)2-3-(triazole) or -C(0)-NH-(CH2)2-3-(thiomaleimide). In other embodiments, a backbone carbon (e.g. in an ethylene positioned between two backbone nitrogen atoms) in the chelator ring is fused to an R-group containing a functional group, optionally wherein the R-group is -(CH2)i-3-(phenyl)-N=C=S or -(CH2)i-3-(phenyl)-N=C=O, optionally 1 ,4-isothiocyanatobenzyl; e.g. p-SCN-Bn-DOTA(S-2-(4-isothiocyanatobenzyl)-1 ,4,7,10-tetraazacyclododecane tetraacetic acid), p-SCN-Bn-NOTA (2-S-(4-isothiocyanatobenzyl)-1 ,4,7-triazacyclononane-1 ,4,7-triacetic acid), and the like. When linked, these derivatives can form a urea linkage (formed from isocyanate) or a thiourea linkage (formed from isothiocyanate).

[0135] In some embodiments, a radiometal chelator is conjugated with a radiometal, a radionuclide-bound metal, or a radionuclide-bound metal-containing prosthetic group, and the radiometal, the radionuclide-bound metal, or the radionuclide-bound metal-containing prosthetic group is chelated to the radionuclide-chelator complex. In some embodiments, the radiometal, the radionuclide-bound metal, or the radionuclide-bound metal-containing prosthetic group is:68Ga,61Cu,64Cu,67Cu,67Ga,111ln,44Sc,86Y,89Zr,90Nb,177Lu,117mSn,165Er, "Y,227Th,225Ac,213Bi,212Bi,72As,77As,211At,203Pb,212Pb,47Sc,166Ho,188Re,186Re,149Pm,159Gd,105Rh,109Pd,198Au,199Au,175Yb,142Pr,114mln,94mTc,99mTc,149Tb,152Tb,155Tb,161Tb, or [18F]AIF. In other embodiments, the radiometal, the radionuclide-bound metal, or the radionuclide-bound metal-containing prosthetic group is:68Ga,61Cu,64Cu,67Cu,67Ga,111ln,44Sc,86Y,177Lu, "Y,225Ac,213Bi, or212Bi. In some embodiments, the chelator is a chelator from Table B and the chelated radionuclide is a radionuclide indicated in Table B as a binder of the chelator.

[0136] In some embodiments, the chelator is: DOTA or a derivative thereof, conjugated with177Lu,111In,213Bi,68Ga,67Ga,203Pb,212Pb,44Sc,47Sc, "Y,86Y,225Ac,117mSn,153Sm,149Tb,152Tb,155Tb,161Tb,165Er,213Bi,224Ra,212Bi,212Pb,225Ac,227Th,223Ra,47Sc,64Cu or67Cu; H2-MACR0PA conjugated with225Ac; Me-3,2-HOPO conjugated with227Th; H4py4pa conjugated with225Ac,227Th or177Lu; H4pypa conjugated with177Lu; NODAGA conjugated with68Ga; DTPA conjugated with111In; or DFO conjugated with89Zr.

[0137] In some embodiments, the chelator is TETA (1 ,4,8,1 1 -tetraazacyclotetradecane- 1 ,4,8,1 1 -tetraacetic acid), SarAr(1 -N-(4-Aminobenzyl)-3,6, 10,13,16,19-hexaazabicyclo[6.6.6]-eicosane-1 ,8-diamine) , NOTA (1 ,4,7-triazacyclononane-1 ,4,7-triacetic acid), TRAP(1 ,4,7-triazacyclononane-1 ,4,7-tris[methyl(2-carboxyethyl)phosphinic acid), HBED (N,N0-bis(2-hydroxybenzyl)-ethylenediamine-N, NO-diacetic acid), 2,3-HOPO(3-hydroxypyridin-2-one), PCTA(3,6,9, 15-tetraazabicyclo[9.3.1 ]-pentadeca-1 (15), 1 1 , 13-triene-3, 6, 9, -triacetic acid) , DFO (desferrioxamine), DTPA (diethylenetriaminepentaacetic acid), OCTAPA (N,N0-bis(6-carboxy-2-pyridylmethyl)-ethylenediamine-N, NO-diacetic acid) or another picolinic acid derivative.

[0138] In some embodiments, an Rradis a chelator for radiolabelling with99mTc,94mTc,186Re, or188Re, such as mercaptoacetyl, hydrazinonicotinamide, dimercaptosuccinic acid, 1 ,2-ethylenediylbis-L-cysteine diethyl ester, methylenediphosphonate, hexamethylpropyleneamineoxime and hexakis(methoxy isobutyl isonitrile), and the like. In some embodiments, an Rradis a chelator, wherein the chelator is mercaptoacetyl, hydrazinonicotinamide, dimercaptosuccinic acid, 1 ,2-ethylenediylbis-L-cysteine diethyl ester, methylenediphosphonate, hexamethylpropyleneamineoxime or hexakis(methoxy isobutyl isonitrile). In some of these embodiments, the chelator is bound by a radionuclide. In some such embodiments, the radionuclide is99mTc,94mTc,186Re, or188Re.

[0139] In some embodiments, an Rradis a chelator that can bind18F-aluminum fluoride ([18F]AIF), such as 1 ,4,7-triazacyclononane-1 ,4-diacetate (NODA) and the like. In some embodiments, the chelator is NODA. In some embodiments, the chelator is bound by [18F]AIF.

[0140] In some embodiments, an Rradis a chelator that can bind72As or77As, such as a trithiol chelate and the like. In some embodiments, the chelator is a trithiol chelate. In some embodiments, the chelator is conjugated to72As. In some embodiments, the chelator is conjugated to77As.

[0141] In certain embodiments, at least one Rradis a prosthetic group containing a trifluoroborate (BF3), capable of18F / 19F exchange radiolabeling. In some of these embodiments, the Rradis BF3-R5-R4-, wherein R4is -(CH2)I-5, optionally methylene, andwherein BF3-R5- forms:wherein R5aand R5bare each independently a C1-C5 linear or branched alkyl group, or a structure listed in Table C (below) or Table D (below). For Tables 3 and 4, each R group in each pyridine substituted with -OR, -SR, -NR-, -NHR or -NR2is independently a C1-C5 linear or branched alkyl. In some embodiments, at least oneBF3-R5- formsBF3 R5awherein R5aand R5bare each independently a C1-C5 linear or branched alkyl group. In some embodiments, at least one of the BF3-R5- group(s) is / are selected from those listed in TableC. In some embodiments, at least one of the BF3-R5-group(s) is / are selected from those listed in Table D. The trifluoroborate-containing prosthetic group(s) may comprise18F. In some embodiments, one fluorine in BF3forms is18F. In some embodiments, all three fluorines in BF3are18F. In some embodiments, all three fluorines in BF3 are19F.

[0143] TABLE D: Exemplary BF3-R5- groups.present) in the pyridine substituted -OR, -SR, -NR-, -NHR or -NR2is independently a linear or branched C1-C5 alkyl. In some embodiments, R is methyl. In some embodiments, R is ethyl. In some embodiments, R is propyl. In some embodiments, R is isopropyl. In some embodiments, R is n-butyl. The trifluoroborate-containing prosthetic group(s) may comprise18F. In some embodiments, one fluorine is a BF3-R5- is18F. In some embodiments, all three fluorines in a BF3-R5- are18F. In some embodiments, all three fluorines in a BF3-R5- are19F.

[0145] In some embodiments, a BF3-R5- may independently formwhich each R (when present) in the pyridine substituted -OR,-SR, -NR-, -NHR or -NR2is independently a linear or branched C1-C5 alkyl. In some embodiments, R is methyl. In some embodiments, R is ethyl. In some embodiments, R ispropyl. In some embodiments, R is isopropyl. In some embodiments, R is n-butyl. In some 0 BF36 N embodiments, a BF3-R5- is . In some embodiments, all three fluorines in a BF3-R5- are18F. In some embodiments, one fluorine in a BF3-R5- is18F. In some embodiments, all three fluorines in a BF3-R5- are19F.

[0146] In some embodiments, at least one BF3-R5- or optionally each BF3-R5- is independentlywherein R5aand R5bare each independently a C1-C5 linear or branched alkyl group. In some embodiments, R5ais methyl. In some embodiments, R5ais ethyl. In some embodiments, R5ais propyl. In some embodiments, R5ais isopropyl. In some embodiments, R5ais butyl. In some embodiments, R5ais n-butyl. In some embodiments, R5ais pentyl. In some embodiments, R5bis methyl. In some embodiments, R5bis ethyl. In some embodiments, R5bis propyl. In some embodiments, R5bis isopropyl. In some embodiments, R5bis butyl. In some embodiments, R5bis n-butyl. In some embodiments, R5bis pentyl. In some embodiments, R5aand R5bare both methyl. The trifluoroborate-containing prosthetic group may comprise18F. In some embodiments, one fluorine in BF3-R5- is18F. In some embodiments, all three fluorines in BF3-R5- are18F. In some embodiments, all three fluorines in BF3-R5- are19F.

[0147] In certain embodiments, the compound is conjugated with a radiometal, a radionuclide-bound metal, or a radionuclide-bound metal-containing prosthetic group for positron emission tomography (PET) or single photon emission computed tomography (SPECT) imaging of GRPR expressing tumors, wherein the compound is conjugated with a radiometal, a radionuclide-bound metal, or a radionuclide-bound metal-containing prosthetic group that is a positron emitter or a gamma emitter. Without limitation, the positron or gamma emitting radiometal, radionuclide-bound metal, or radionuclide-bound metal-containing prosthetic group i152Tb,155Tb,18F,1

[0148] In certain embodiments the compound is conjugated with a radiometal, a radionuclide-bound metal, or a radionuclide-bound metal-containing prosthetic group that is used for therapy. This includes radiometals such as165Er,212Bi,211At,166Ho,149Pm,159Gd,105Rh,109Pd,198Au,199Au,175Yb,142Pr,177Lu,213Bi,47Sc,225Ac,117mSn,153Sm,149Tb,161Tb,224Ra,223Ra,203Pb,212Pb,227Th,77As,186Re,188Re,64Cu or67Cu. In embodiments, the radiometal is165Er,212Bi,211At,166Ho,149Pm,159Gd,105Rh,109Pd,198Au,199Au,175Yb,142Pr,177Lu,111ln,213Bi,47Sc,225Ac,117mSn,153Sm,149Tb,161Tb,224Ra,223Ra,212Pb,227Th,223Ra,77As,186Re,188Re,67Cu, or64Cu.

[0149] In some embodiments, n6 is 1 , and the linker and RLtogether form a p-aminomethylaniline-diglycolic acid (pABzA-DIG) linker, a 4-amino-(1-carboxymethyl)piperidine (Pip) linker, a 9-amino-4,7-dioxanonanoic acid (dPEG2) linker, or a 4-(2-aminoethyl)-1-carboxymethyl-piperazine (Acp) linker. In some embodiments, the linker and RLtogether form:

[0150] In some embodiments, the compound is:RD06-001 : DOTA-Pip-D-Phe-Gln-Trp(7-F)-Ala-Val-NMe-Gly-His-Leu-qj-Pro-NH2,RD06-002: DOTA-Pip-D-Phe-Gln-Trp(7-F)-Ala-Val-NMe-Gly-His-Leu-qj-diFPro-NH2, RD06-003: DOTA-Pip-D-Phe-Gln-Trp(7-F)-Ala-Tle-Gly-His-Leu-qj-Pro-NH2, orRD06-004: DOTA-Pip-D-Phe-Gln-Trp(7-F)-Ala-Tle-Gly-His-Leu-qj-diFPro-NH2, wherein qj is a reduced peptide bond.

[0151] In some embodiments, the compound is RD06-001 , optionally conjugated by a radiometal. In some embodiments, the compound is RD06-002, optionally conjugated by a radiometal. In some embodiments, the compound is RD06-003, optionally conjugated by a radiometal. In some embodiments, the compound is RD06-004, optionally conjugated by a radiometal.

[0152] In some embodiments, the compound is:Ga-RD06-001 : Ga-DOTA-Pip-D-Phe-Gln-Trp(7-F)-Ala-Val-NMe-Gly-His-Leu-qj-Pro-NH2,Ga-RD06-002: Ga-DOTA-Pip-D-Phe-Gln-Trp(7-F)-Ala-Val-NMe-Gly-His-Leu-qj-diFPro-NH2, Ga-RD06-003: Ga-DOTA-Pip-D-Phe-Gln-Trp(7-F)-Ala-Tle-Gly-His-Leu-qj-Pro-NH2, or Ga-RD06-004: Ga-DOTA-Pip-D-Phe-Gln-Trp(7-F)-Ala-Tle-Gly-His-Leu-qj-diFPro-NH2, wherein qj is a reduced peptide bond.

[0153] In some embodiments, the compound is:68Ga-RD06-001 :68Ga-DOTA-Pip-D-Phe-Gln-Trp(7-F)-Ala-Val-NMe-Gly-His-Leu-qj-Pro-NH2,68Ga-RD06-002:68Ga-DOTA-Pip-D-Phe-Gln-Trp(7-F)-Ala-Val-NMe-Gly-His-Leu-qj-diFPro-NH2,68Ga-RD06-003:68Ga-DOTA-Pip-D-Phe-Gln-Trp(7-F)-Ala-Tle-Gly-His-Leu-qj-Pro-NH2, or68Ga-RD06-004:68Ga-DOTA-Pip-D-Phe-Gln-Trp(7-F)-Ala-Tle-Gly-His-Leu-qj-diFPro-NH2, wherein qj is a reduced peptide bond.

[0154] In another specific embodiment, the compounds listed above (such as RD06-001 , RD06-002, RD06-003, and RD06-004) and described herein may be included in a pharmaceutical composition. In a specific embodiment, the pharmaceutical composition mayinclude one or more compounds from the compounds listed above (such as RD06-001 , RD06-002, RD06-003, and RD06-004) and described herein or Formula I, IA, A, or B and a pharmaceutically acceptable carrier. In another specific embodiment, the compound(s) may be bound to or include a radiometal. In a specific embodiment, the radiometal is165Er,212Bi,211At,166Ho,149Pm,159Gd,105Rh,109Pd,198Au,199Au,175Yb,142Pr,177Lu,111ln,213Bi,47Sc, "Y,225Ac,117mSn,153Sm,149Tb,161Tb,224Ra,223Ra,212Pb,227Th,223Ra,77As,186Re,188Re,67Cu, or64Cu.

[0155] In a specific embodiment, the compounds listed above (such as RD06-001 , RD06-002, RD06-003, and RD06-004) and described herein, may used for imaging methods.In a specific embodiment, the methods may include imaging Gastrin-releasing peptide receptor (GRPR) in a subject, the method comprising: administering to the subject a peptidic compound, including RD06-001 , RD06-002, RD06-003, and RD06-004 listed above and described herein, and / or any compound of Formulas I, A or B; and imaging tissue of the subject. In a specific embodiment, the methods may include the methods of treating cancer in a subject comprising, administering to the subject in need thereof a peptidic compound including RD06-001 , RD06-002, RD06-003, and RD06-004 listed above and described herein, and / or any compound of Formulas I, IA, A or B.

[0156] In another specific embodiment, the methods may include treating a GRPR-expressing condition or disease. In a specific embodiment, the GRPR-expressing condition or disease may be a psychiatric disorder, neurological disorder, inflammatory disease, prostate cancer, lung cancer, head and neck cancer, colon cancer, kidney cancer, ovarian cancer, liver cancer, pancreatic cancer, breast cancer, glioma or neuroblastoma. In some embodiments, the cancer is prostate cancer.

[0157] In some embodiments, the compounds described herein are optionally conjugated by a radiometal, and may be used for the methods described herein.

[0158] In alternative embodiments, the radiometal is177Lu,111ln,213Bi,68Ga,67Ga,203Pb,212Pb,44Sc,47Sc, "Y,86Y,225Ac,117mSn,153Sm,149Tb,152Tb,155Tb,161Tb,165Er,213Bi,224Ra,212Bi,212Pb,225Ac,227Th,223Ra,47Sc,64Cu or67Cu. In some embodiments, the radiometal is68Ga. In some embodiments, the radiometal is64Cu. In some embodiments, the radiometal is67Cu. In some embodiments, the radiometal is67Ga. In some embodiments, the radiometal is111ln. In some embodiments, the radiometal is177Lu. In some embodiments, the radiometal is "Y In some embodiments, the radiometal is225Ac.

[0159] When the radiolabeling group (i.e. Rradin Formula I) comprises or is conjugated to a diagnostic radionuclide, there is disclosed use of certain embodiments of a compound as disclosed herein for preparation of a radiolabelled tracer for imaging GRPR-expressing tissues in a subject. There is also disclosed a method of imaging GRPR-expressing tissues in a subject, in which the method comprises: administering to the subject a compositioncomprising a compound described herein and a pharmaceutically acceptable excipient; and imaging tissue of the subject, e.g. using PET or SPECT. When the tissue is a diseased tissue (e.g. a GRPR-expressing cancer), GRPR-targeted treatment may then be selected for treating the subject.

[0160] When the radiolabeling group (i.e. Rradin Formula I) comprises or is conjugated to a therapeutic radionuclide, there is disclosed use of certain embodiments of the compound (or a pharmaceutical composition thereof) for the treatment of GRPR-expressing conditions or diseases (e.g. cancer and the like) in a subject. Accordingly, there is provided use of a compound disclosed herein in preparation of a medicament for treating a GRPR-expressing condition or disease in a subject. There is also provided a method of treating GRPR-expressing disease in a subject, in which the method comprises: administering to the subject a composition comprising the compound and a pharmaceutically acceptable excipient. For example, but without limitation, the disease may be a GRPR-expressing cancer. In a specific embodiment, the compounds listed above (such as RD06-001 , RD06-002, RD06-003, and RD06-004) and described herein, may include or be conjugated to a radiometal. In a specific embodiment, the methods may include imaging Gastrin-releasing peptide receptor (GRPR) in a subject, the method comprising: administering to the subject a peptidic compound, including the compounds listed above (such as RD06-001 , RD06-002, RD06-003, and RD06-004) with a radiometal and described herein, and / or any compound of Formulas I, A or B with a radiometal; and imaging tissue of the subject. In a specific embodiment, the methods may include the methods of treating cancer in a subject comprising, administering to the subject in need thereof a peptidic compound including the compounds listed above (such as RD06-001 , RD06-002, RD06-003, and RD06-004) with a radiometal and described herein, and / or any compound of Formulas I, A or B with a radiometal.

[0161] Aberrant or ectopic GRPR expression has been detected in various conditions and diseases, including psychiatric / neurological disorders, inflammatory disease, and cancer (Cornelio, et al. Ann Oncol. 2007, 18:1457-1466; Bajo et al. Proc Natl Acad Sci U S A. 2002, 99:3836-3841 ; Koppan et al. Cancer. 1998, 83:1335-1343; Shirahige et al. Biomed Pharmacother. 1994 48:465-472; Cai et al. Int J Oncol. 1995, 6:1165-1172; Jungwirth, Eur J Cancer Part A. 1997, 33:1141-1148; Gonzalez et al., J Pharmacol Exp Ther. 200, 331 (1): 265-276; Dalm et al. PLoS One. 2017, 12(1): e0170536; Guo et al., Curr Opin Endocrinol Diabetes Obes. 2015, 22(1): 3-8; Ischia et al., BJU Int. 201 ,113 Suppl 2:40-47; Ramos-Alvarez et al. Peptide 2015, 72: 128-144). Accordingly, without limitation, the GRPR-expressing condition or disease may be psychiatric disorder, neurological disorder, inflammatory disease, prostate cancer, lung cancer, head and neck cancer, colon cancer, kidney cancer, ovarian cancer, liver cancer, pancreatic cancer, breast cancer, glioma or neuroblastoma. In some embodiments, the cancer is prostate cancer.

[0162] The compounds presented herein incorporate peptides, which may be synthesized by any of a variety of methods established in the art. This includes but is not limited to liquid-phase as well as solid-phase peptide synthesis using methods employing 9-fluorenylmethoxycarbonyl (Fmoc) and / or t-butyloxycarbonyl (Boc) chemistries, and / or other synthetic approaches.

[0163] Solid-phase peptide synthesis methods and technology are well-established in the art. For example, peptides may be synthesized by sequential incorporation of the amino acid residues of interest one at a time. In such methods, peptide synthesis is typically initiated by attaching the C-terminal amino acid of the peptide of interest to a suitable resin. Prior to this, reactive side chain and alpha amino groups of the amino acids are protected from reaction by suitable protecting groups, allowing only the alpha carboxyl group to react with a functional group such as an amine group, a hydroxyl group, or an alkyl halide group on the solid support. Following coupling of the C-terminal amino acid to the support, the protecting group on the side chain and / or the alpha amino group of the amino acid is selectively removed, allowing the coupling of the next amino acid of interest. This process is repeated until the desired peptide is fully synthesized, at which point the peptide can be cleaved from the support and purified. A non-limiting example of an instrument for solid-phase peptide synthesis is the Aapptec Endeavor 90 peptide synthesizer.

[0164] To allow coupling of additional amino acids, Fmoc protecting groups may be removed from the amino acid on the solid support, e.g. under mild basic conditions, such as piperidine (20-50% v / v) in DMF. The amino acid to be added must also have been activated for coupling (e.g. at the alpha carboxylate). Non-limiting examples of activating reagents include without limitation 2-(1 H-benzotriazol-1-yl)-1 ,1 ,3,3-tetramethyluronium hexafluorophosphate (HBTU), 2-(1 H-benzotriazol-1-yl)-1 ,1 ,3,3-tetramethyluronium tetrafluoroborate (TBTU), 2-(7-Aza-1 H-benzotriazole-1-yl)-1 , 1 ,3,3-tetramethyluronium hexafluorophosphate (HATU), benzotriazole-1-yl-oxy-tris(dimethylamino)phosphoniumhexafluorophosphate (BOP), benzotriazole- 1-yl-oxy-tris(pyrrolidino)phosphoniumhexafluorophosphate (PyBOP).Racemization is minimized by using triazoles, such as 1-hydroxy-benzotriazole (HOBt) and 1-hydroxy-7-aza-benzotriazole (HOAt). Coupling may be performed in the presence of a suitable base, such as N,N-diisopropylethylamine (DIPEA / DIEA) and the like.

[0165] Apart from forming typical peptide bonds to elongate a peptide, peptides may be elongated in a branched fashion by attaching to side chain functional groups (e.g. carboxylic acid groups or amino groups), either: side chain to side chain; or side chain to backbone amino or carboxylate. Coupling to amino acid side chains may be performed by any known method, and may be performed on-resin or off-resin. Non-limiting examples include: forming an amide between an amino acid side chain containing a carboxyl group (e.g. Asp, D-Asp,Glu, D-Glu, and the like) and an amino acid side chain containing an amino group (e.g. Lys, D-Lys, Orn, D-Orn, Dab, D-Dab, Dap, D-Dap, and the like) or the peptide N-terminus; forming an amide between an amino acid side chain containing an amino group (e.g. Lys, D-Lys, Orn, D-Orn, Dab, D-Dab, Dap, D-Dap, and the like) and either an amino acid side chain containing a carboxyl group (e.g. Asp, D-Asp, Glu, D-Glu, and the like) or the peptide C-terminus; and forming a 1 , 2, 3-triazole via click chemistry between an amino acid side chain containing an azide group (e.g. Lys(N3), D-Lys(N3), and the like) and an alkyne group (e.g. Pra, D-Pra, and the like). The protecting groups on the appropriate functional groups must be selectively removed before amide bond formation, whereas the reaction between an alkyne and an azido groups via the click reaction to form an 1 ,2, 3-triazole does not require selective deprotection. Non-limiting examples of selectively removable protecting groups include 2-phenylisopropyl esters (O-2-PhiPr) (e.g. on Asp / Glu) as well as 4- methyltrityl (Mtt), allyloxycarbonyl (alloc), 1-(4,4-dimethyl-2,6-dioxocyclohex-1-ylidene))ethyl (Dde), and1-(4,4-dimethyl-2,6-dioxocyclohex-1-ylidene)-3-methylbutyl (ivDde) (e.g. on Lys / Orn / Dab / Dap). O-2-PhiPr and Mtt protecting groups can be selectively deprotected under mild acidic conditions, such as 2.5% trifluoroacetic acid (TFA) in DCM. Alloc protecting groups can be selectively deprotected using tetrakis(triphenylphosphine)palladium(0) and phenyl silane in DCM. Dde and ivDde protecting groups can be selectively deprotected using 2-5% of hydrazine in DMF. Deprotected side chains of Asp / Glu (L- or D-forms) and Lys / Orn / Dab / Dap (L- or D-forms) can then be coupled, e.g. by using the coupling reaction conditions described above. The above provides means for including multiple BF3groups.

[0166] Peptide backbone amides may be N-methylated (i.e. alpha amino methylated) or N-alkylated. This may be achieved by directly using Fmoc-N-methylated (or Fmoc-N-alkylated) amino acids during peptide synthesis. Alternatively, N-methylation under Mitsunobu conditions may be performed. First, a free primary amine group is protected using a solution of 4-nitrobenzenesulfonyl chloride (Ns-CI) and 2,4,6-trimethylpyridine (collidine) in NMP. N-methylation (or N-alkylation) may then be achieved in the presence of triphenylphosphine, diisopropyl azodicarboxylate (DIAD) and methanol. Subsequently, N-deprotection may be performed using mercaptoethanol and 1 ,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in NMP. For coupling protected amino acids to N-methylated (or N-alkylated) alpha amino groups, HATU, HOAt and DIEA may be used.

[0167] The formation of the thioether (-S-) linkages (e.g. for L1) can be achieved either on solid phase or in solution phase. For example, the formation of thioether (-S-) linkage can be achieved by coupling between a thiol-containing compound (such as the thiol group on cysteine side chain) and an alkyl halide (such as 3-(Fmoc-amino)propyl bromide and the like) in an appropriate solvent (such as N,N-dimethylformamide and the like) in the presence of base (such as N,N-diisopropylethylamine and the like). If the reactions are carried out insolution phase, the reactants used are preferably in equivalent molar ratio (1 to 1), and the desired products can be purified by flash column chromatography or high performance liquid chromatography (HPLC). If the reactions are carried out on solid phase, meaning one reactant has been attached to a solid phase, then the other reactant is normally used in excess amount (> 3 equivalents of the reactant attached to the solid phase). After the reactions, the excess unreacted reactant and reagents can be removed by sequentially washing the solid phase (resin) using a combination of solvents, such as N,N-dimethylformamide, methanol and dichloromethane, for example.

[0168] The formation of the linkage (e.g. for L1) between a thiol group and a maleimide group can be performed using the conditions described above for the formation of the thioether (-S-) linkage simply by replacing the alkyl halide with a maleimide-containing compounds. Similarly, this reaction can be conducted in solid phase or solution phase. If the reactions are carried out in solution phase, the reactants used are preferably in equivalent molar ratio (1 to 1), and the desired products can be purified by flash column chromatography or high performance liquid chromatography (HPLC). If the reactions are carried out on solid phase, meaning one reactant has been attached to a solid phase, then the other reactant is normally used in excess amount (> 3 equivalents of the reactant attached to the solid phase). After the reactions, the excess unreacted reactant and reagents can be removed by sequentially washing the solid phase (resin) using a combination of solvents, such as N,N-dimethylformamide, methanol and dichloromethane, for example.

[0169] Urea or thiourea linkages can be made from reaction of an amine group with an isocyanate or an isothiocyanate, respectively, which are common functional groups on radiometal chelators. The isothiocyanate functional group may be added to the radiometal chelator by reacting an amino group on the chelator with thiophosgene [i.e. C(S)CI2]. Similarly, the isocyanate functional group may be added to the radiometal chelator by reacting an amino group on the chelator with phosgene [i.e. C(O)CI2].

[0170] Non-peptide moieties (e.g. radiolabeling groups and / or albumin binders) may be coupled to the peptide N-terminus while the peptide is attached to the solid support. This is facile when the non-peptide moiety comprises an activated carboxylate (and protected groups if necessary) so that coupling can be performed on resin. For example, but without limitation, a bifunctional chelator, such as 1 ,4,7,10-tetraazacyclododecane-1 ,4,7,10-tetraacetic acid (DOTA) tris(tert-butyl ester) may be activated in the presence of N-hydroxysuccinimide (NHS) and N,N'-dicyclohexylcarbodiimide (DCC) for coupling to a peptide. Alternatively, a non-peptide moiety may be incorporated into the compound via a copper-catalyzed click reaction under either liquid or solid phase conditions. Copper-catalyzed click reactions are well established in the art. For example, 2-azidoacetic acid is first activated by NHS and DCC and coupled to a peptide. Then, an alkyne-containing non-peptide moiety may be clicked tothe azide-containing peptide in the presence of Cu2+and sodium ascorbate in water and organic solvent, such as acetonitrile (ACN) and DMF and the like. Non-peptide moieties may also be added in solution phase, which is routinely performed.

[0171] The synthesis of radiometal chelators is well-known and many chelators are commercially available (e.g. from Sigma-AldrichTM / Milipore Sigma™ and others). Protocols for conjugation of radiometals to the chelators is also well known (e.g. see Examples, below).

[0172] The synthesis of the BF3-R5-R4- component of the compounds can be achieved following previously reported procedures (Liu et al. Angew Chem Int Ed 2014 53:11876-11880; Liu et al. J Nucl Med 2015 55:1499-1505; Liu et al. Nat Protoc 2015 10:1423-1432; Kuo et al. J Nucl Med, 2019 60:1160-1166; each of which is incorporated by reference in its entirety). Generally, the BF3-containing motif can be coupled to the linker via click chemistry by forming a 1 ,2,3-triazole ring between a BF3-containg azido (or alkynyl) group and an alkynyl (or azido) group on the linker, or by forming an amide linkage between a BF3-containg carboxylate and an amino group on the linker. To make the BF3-containing azide, alkyne or carboxylate, a boronic acid ester-containing azide, alkyne or carboxylate is first prepared following by the conversion of the boronic acid ester to BF3in a mixture of HCI, DMF and KHF2. For alkyl BF3, the boronic acid ester-containing azide, alkyne or carboxylate can be prepared by coupling boronic acid ester-containing alkyl halide (such as iodomethylboronic acid pinacol ester) with an amine-containing azide, alkyne or carboxylate (such as N,N-dimethylpropargylamine). For aryl BF3, the boronic acid ester can be prepared via Suzuki coupling using aryl halide (iodine or bromide) and bis(pinacolato)diboron.

[0173] 18F-Fluorination of the BF3-containing compounds via18F-19F isotope exchange reaction can be achieved following previously published procedures (Liu et al. Nat Protoc 2015 10:1423-1432, incorporated by reference in its entirety). Generally, ~100 nmol of the BF3-containing compound is dissolved in a mixture of 15 pl of pyridazine-HCI buffer (pH = 2.0-2.5, 1 M), 15 pl of DMF and 1 pl of a 7.5 mM KHF2aqueous solution.18F-Fluoride solution (in saline, 60 pl) is added to the reaction mixture, and the resulting solution is heated at 80 °C for 20 min. At the end of the reaction, the desired product can be purified by solid phase extraction or by reversed high performance liquid chromatography (HPLC) using a mixture of water and acetonitrile as the mobile phase.

[0174] When the peptide has been fully synthesized on the solid support, the desired peptide may be cleaved from the solid support using suitable reagents, such as TFA, tri-isopropylsilane (TIS) and water. Side chain protecting groups, such as Boc, pentamethyldihydrobenzofuran-5-sulfonyl (Pbf), trityl (Trt) and tert-butyl (tBu) are simultaneously removed (i.e. deprotection). The crude peptide may be precipitated and collected from the solution by adding cold ether followed by centrifugation. Purification and characterization of the peptides may be performed by standard separation techniques, suchas high performance liquid chromatography (HPLC) based on the size, charge and polarity of the peptides. The identity of the purified peptides may be confirmed by mass spectrometry or other similar approaches. The inventions described herein are further represented by the following embodiments.

[0175] The present invention will be further illustrated in the following examples.EXAMPLES

[0176] General methods: Chemicals were procured from commercial sources and used without further purification. All peptides were synthesized on apeptide synthesizer. Purification and quality control of peptide precursor and nonradioactive Lu-complexed standards were performed on Agilent HPLC systemsHPLC columns used were a semipreparative column (Luna C18, 5 pm particle size, 100 A pore size, 250 x mm) and an analytical column (Luna C18, 5 pm particle size, 100 A pore size, 250 x 4.6 mm) from Phenomenex. The collected HPLC eluates containing the desired peptides were lyophilized using a Labconco FreeZone 4.5 Plus freeze drier. Mass analyses were performed using Agilent mass spectrometer.

[0177] Example 1. Synthesis of Fmoc-Leu(i )diFPro-OH

[0178] Synthesis of Fmoc-diFPro-OtBu (1): t-Butyl trichloroacetimidate (4.37 g, 20 mmol) was added to a solution of (2S)-Fmoc-4,4-difluoro-pyrrolidine-2-carboxylic acid (Fmoc-diFPro-OH, 3.73 g, 10 mmol) in dichloromethane (30 mL), and the resulting solution was stirred at room temperature for 22 h. After evaporation, the residue was purified by flash column chromatography eluted with 1 :2 diethyl ether / hexanes to obtain 3.76 g (88%) of compound 1 as a colorless thick oil.

[0179] Synthesis of diFPro-OtBu HCI salt (2): A solution of compound 1 (3.72 g, 8.7 mmol) and palladium on charcoal (10%, 300 mg) in methanol (80 mL) was hydrogenated using a balloon. After 2 days, the reaction mixture was filtered through celite, and the filtrate was evaporated under reduced pressure. The residue was dissolved in diethyl ether (200 mL). After the addition of HCI (4 N in 1 ,4-dioxane, 5 mL), the solution was stirred for 10 min. The resulting precipitate was filtered and dried under vacuum to obtain 1 .78 g (84%) of compound 2 as a white solid.

[0180] Synthesis of Fmoc-Leu(qj)diFPro-OtBu (4): A solution of Fmoc-leucinol (2.20 g, 6.5 mmol) in dichloromethane (40 mL) cooled in an ice / water bath was added Dess-Martin periodinane (3.44 g, 8.1 mmol). After stirring for 22 h, a solution of sodium thiosulfate (4.5 g) in saturated sodium bicarbonate aqueous solution (45 mL) was added, and the resulting solution was stirred for 30 min. After separating the two phases, the aqueous phase was extracted with dichloromethane (50 mL). The organic phases were combined, dried over anhydrous magnesium sulfate, and evaporated under reduced pressure to yield the 2.33 g of crude aldehyde 3 as a yellowish solid.

[0181] A solution of the crude aldehyde 3 (2.33 g), diFPro-OtBu HCI salt (2, 1.70 g, 7.0 mmol), triethylamine (TEA, 809 mg, 8 mmol) and sodium triacetoxyborohydride (3.18 g, 15 mmol) in dichloromethane (40 mL) was stirred for 2 days. After addition of 100 mL of saturated sodium bicarbonate aqueous solution, the resulting mixture was stirred for 10 min. The phases were separated and the aqueous phase was extracted with dichloromethane (50 mL). The organic phases were combined, dried over anhydrous magnesium sulfate, and evaporated under reduced pressure. The residue was purified by flash column chromatography eluted with 1 :4 ethyl acetate / hexanes to obtain 2.51 g of compound 4 as a thick colorless oil. The yield is 73% over 2 steps.

[0182] Synthesis of Fmoc-Leu(qj)diFPro-OH (5): A solution of compound 4 (2.48 g, 4.7 mmol) and triethylsilane (1.37 g, 11.8 mmol) in dichloromethane (25 mL) was added trifluoroacetic acid (TFA, 75 mL). The resulting solution was stirred at room temperature for 3 h. The volatile solvents were evaporated under reduced pressure, and the residue was dissolved in diethyl ether (200 mL). HCI (4 N in 1 ,4-dioxane, 4 mL) was added to the ethereal solution, and the resulting solution was stirred for 5 min. The formed precipitate was filtered and dried under vacuum to obtain 1 .87 g (78%) of compound 5 as a white solid.

[0183] Example 2. Peptide synthesis: general methods

[0184] The peptide synthesis was performed by solid-phase peptide synthesis (SPPS) with an Fmoc / HATU strategy, beginning with a Sieber resin or Rink Amide Resin to yield desirable C-termini. In most cases, a microwave-based automated peptide synthesizer was employed. According to the peptide sequence, each Fmoc-protected amino acid wassubsequently coupled to the resin, followed by Fmoc-deprotection. The synthesis continued with the addition of the linker, Fmoc-4-amino-(1 -carboxymethyl) piperidine (4 eq.) and then followed by the chelator DOTA(tBu)3. The peptide was then deprotected and simultaneously cleaved from the resin by using trifluoroacetic acid (TFA) approach. The cleaved peptides were filtrated and then precipitated by cold diethyl ether. The crude peptides were collected by centrifugation and purified by HPLC (0.1% TFA in H2O / MeCN, semi-preparative column, Luna C18). The eluates containing the desired peptides were collected and lyophilized to yield quantities between 10 and 50 mg, with purities ranging from 95% to 99%. The four synthesized peptides (i.e., RD06-001 , RD06-002, RD06-003, RD06-004) have their structures shown below and sequences shown in TABLE E.RD06-004

[0185] TABLE E: Exemplary peptide sequences

[0186] Example 3. Synthesis of Lu- or La- cold standards: general methodsThe precursor (1 eq., 5-10 mg) and LuCI3or LaCI3(5 eq.) were dissolved in 0.2 M aq. NaOAc and MeCN (2.5:1 , DMSO was added when solubility is low). The reaction mixture was heated to 90°C for 30 minutes then diluted with H2O / MeCN and directly purified by semi-prep HPLC (0.1% TFA in H2O / MeCN) to obtain the Lu or La-cold standard. The eluates containing the desired compounds were collected and lyophilized to yield quantities between 3 and 8 mg, with purities ranging from 95% to 99%, with their mass shown in TABLE F.

[0187] TABLE F: Exemplary peptide mass

[0188] In vitro competition binding assayPC-3 cells were seeded at 2 x 105 cells / well in 24-well poly-D-lysine plates 24-48 hours prior to the experiment. The growth medium was replaced by 400 pL of reaction medium (RPMI 1640 containing 2 mg / mL BSA, 4.8 mg / mL HEPES, 1 U / mL penicillin G and 1 pg / mL streptomycin). Cells were incubated for 30-60 min at 37 °C. Peptides below provided in 50 pL of decreasing concentrations (10 pM to 1 pM) and 50 pL of 0.011 nM [125l-Tyr4]bombesin were added to wells. The cells were incubated with moderate agitation for 1 h at 27 °C, washed twice with ice-cold PBS, harvested by trypsinization, and measured for radioactivity on thegamma counter. Data were analyzed using nonlinear regression (one binding site model for competition assay) with GraphPad Prism 10.1.1. See TABLE G and Figure 1.

[0189] TABLE G: Binding affinities of exemplary peptides

[0190] Radiolabeling with177LuA small aliquot of the precursor (1-5 pL, 1-3 nmol) was dissolved in 0.2 M NaOAc buffer (pH 4.5). To the solution was added a known amount / activity of177LuCI3. Then, the reaction was heated to 95°C for 15 minutes. The reaction was then cooled down and further diluted with the suitable formulation or dilution buffer. For quality control, the formulated solutions were analyzed using radio-TLC (iTLC) and radio-HPLC. iTLCs were run on SG paper plates, with 0.1 M sodium citrate (5% MeOH) as the eluent. The developed plates were then read using a radio-TLC reading instrument. HPLC analyses were performed using an analytical Luna column, the mobile phase condition was using gradient from 5 to 85% acetonitrile in water with 0.1% TFA in 15 minutes at a flow rate of 1 mL / min. The eluting components were visualized by UV (DAD) and radio-detection flow monitors. In all cases, the radiochemical purity of the radiolabeled compound was assessed at the end of synthesis (EOS) and after 3 h (estimated time between end of synthesis and in vivo experiments).

[0191] Radiolabeling with225AcA small aliquot of the precursor (1-5 pL, 1-3 nmol) was dissolved in 0.2 M NaOAc buffer (pH 4.5). To the solution was added a known amount / activity of of225AcCI3or225Ac(NO3)3. The reaction was heated to 95°C for 20 minutes, then cooled down, and further diluted with the suitable formulation or dilution buffer. For quality control, the formulated solutions were analyzed using radio-TLC (iTLC) and radio-HPLC. iTLCs were run on SG paper plates, with 0.1 M sodium citrate (5% MeOH) as the eluent. The developed plates were then read using a radio-TLC reading instrument. HPLC analyses were performed using an analytical Luna column with fraction collection. The mobile phase condition was using gradient from 5 to 85% acetonitrile in water with 0.1% TFA in 15 minutes at a flow rate of 1 mL / min. The eluting components were visualized by UV (DAD) and radio-detection flow monitors. To detect the emissions resulting from the decay chain of225Ac, all collected fractions from HPLC were allowed to equilibrate for 6 h, then were placed in a Gamma counting instrument forsubsequent measurements. The radiochemical purity of the radiolabeled compound was assessed at the end of synthesis (EOS) and after 3-5 h (estimated time between end of synthesis and in vivo experiments).

[0192] Example 4. Ex vivo biodistribution in PC-3 tumor-bearing miceAll experiments were conducted according to the guidelines established by the Canadian Council on Animal Care and approved by the University of British Columbia Animal Ethics Committee. Male NOD.Cg-Rag1tm1 MomH2rgtm1Wjl / SzJ (NRG) mice (n > 4) were subcutaneously inoculated with human prostate PC-3 cells (GRPR positive). When tumors reached suitable size, animals were injected intravenously with the formulated radiopharmaceutical of interest (~33 kBq of the177Lu-labeled tracer or ~8 kBq of the225Ac-labeled tracer). At desire time points after injection, the animals were euthanized. Blood, urine, tumor and major organs were harvested, rinsed with PBS, blotted dry, weighted and assessed for their radioactivity in an automated gamma counter. Uptake was reported as a fraction of injected dose per mass of tissue (%ID / g) decay corrected. Biodistribution data of exemplary radioligands are included in TABLES H-K below.

[0193] TABLE H: Biodistribution of radioligand177Lu-RD06-001int. = intestine

[0194] TABLE I: Biodistribution of radioligand177Lu-RD06-003int. = intestine

[0195] TABLE J: Biodistribution of radioligand177Lu-RD06-004int. = intestine

[0196] TABLE K: Biodistribution of radioligand225Ac-RD06-003int. = intestine; T = tumor

[0197] All publications, patents and patent applications, including any drawings and appendices therein are incorporated by reference in their entirety for all purposes to the same extent as if each individual publication, patent or patent application, drawing, or appendix was specifically and individually indicated to be incorporated by reference in its entirety for all purposes. It will be apparent to persons skilled in the art that a number of variations and modifications can be made without departing from the scope of the invention as defined in the following claims. The scope of the invention should therefore not be limited by the preferred embodiments set forth in the above Examples, but should be given the broadest interpretation consistent with the description as a whole.

Claims

WHAT IS CLAIMED IS:1 . A peptidic compound of Formula (I), or a salt or solvate thereof, optionally complexed with a radioisotope,Rradn6-[linker]-RL-Xaa1-Xaa2-Xaa3-Xaa4-Xaa5-Xaa6-Xaa7-Xaa8-(qj-Xaa9)m-R(I) wherein:Xaa1is an N-terminal amino acid residue selected from D-Phe, 4-chlorophenylalanine (Cpa), D-Cpa, 3-(1-naphthyl)alanine (Nal), D-Tpi, D-Nal, 3-(2-naphthyl)alanine (2-Nal), or D-2-Nal;Xaa2is Asn, Gin, homoserine (Hse), citrulline (Cit) or His;Xaa3is Trp, |3-(3-benzothienyl)alanine (Bta), Trp(Me), Trp(7-Me), Trp(6-Me), Trp(5-Me), Trp(4-Me), Trp(2-Me), Trp(7-F), Trp(6-F), Trp(5-F), Trp(4-F), Trp(5-OH), Tpi, 7-Aza, or aMe-Trp;Xaa4is Ala or Ser;Xaa5is Vai, 2,3-dehydro-Val, Cpg (cyclopentylglycine), L-cyclopropylglycine, L-cyclobutylg lycine, or tert-leucine (Tie);Xaa6is Gly, NMe-Gly, or D-Ala;Xaa7is His or NMe-His;R is -NH2or -NHOH; m is 0 or 1 ; when m is 0, Xaa8-R is a C-terminally amidated (R is -NH2) or a C-terminally hydroxylamidated (R is -NHOH) amino acid residue selected from statine (Sta), Leu, D-Pro, or Phe; when m is 1 , Xaa8is statine (Sta), Leu, D-Pro, or Phe; and Xaa9-R is a C-terminally amidated (R is -NH2) or a C-terminally hydroxylamidated (R is -NHOH) amino acid residue selected from Pro, Phe, oxazolidine-4-carboxylic acid (4-oxa-L-Pro), 4,4-difluoroproline (diFPro), Leu, Me2Thz (5,5-dimethyl-1 ,3-thiazolidine-4-carboxylic acid), or thiazoline-4-carboxylic acid (Thz); qj represents a peptide bond or reduced peptide bond joining Xaa8to Xaa9;RLis -C(O)-, -NH-C(O)-, or -NH-C(S)-; the linker is a linear or branched chain of n1 units of -L1R1- and / or -(L1)2R1-, wherein: n1 is 1-20; each R1is, independently, a linear, branched, and / or cyclic Cn2alkylenyl, alkenylenyl and / or alkynylenyl, wherein each n2 is independently 1-20, wherein any carbon bonded to two other carbons is optionally independently replaced by N, S, or O, and carbons are optionally independently substituted with oxo, hydroxyl, sulfhydryl,-SeH, halogen, guanidino, amine, amide, urea, carboxylic acid, sulfonic acid, sulfinic acid, or phosphoric acid;L1bonds to carbon, wherein each L1is independently -S-, -N(R2)C(O)-,R2is H, methyl or ethyl; an albumin binder (Ralb) is optionally bonded to an L1of the linker, wherein the albumin binder is:-(CH2)n3-CH3wherein n3 is 8-20; H wherein n4 is 8-20;wherein n5 is 1-4 and R3ais H or methyl, and R3bis I, Br, F, Cl, H, OH, OCH3, NH2, NO2or Ci-C6alkyl; orn6 is 1-5; each Rradis a radiolabeling group bonded to or incorporating an L1of the linker, wherein each radiolabeling group is independently: a radiometal chelator; an aryl or heteroaryl substituted with a radiohalogen; a prosthetic group containing a trifluoroborate; a prosthetic group containing a silicon-fluorine-acceptor moiety; or a prosthetic group containing a fluorophosphate, fluorosulfate, sulfonyl fluoride, or a combination thereof; and wherein(i) Xaa3is Trp(7-F) and Xaa9-R is a C-terminally amidated Pro or diFPro;(ii) qj represents a reduced peptide bond, m is 1 , Xaa3is |3-(3-benzothienyl)alanine (Bta), Trp(Me), Trp(7-Me), Trp(6-Me), Trp(5-Me), Trp(4-Me), Trp(2-Me), Trp(7-F), Trp(6-F), Trp(5-F), Trp(4-F), Trp(5-OH), Tpi, 7-Aza, or aMe-Trp, and Xaa9-R is a C-terminally amidated Pro or diFPro; or(iii) a combination of (i) and (ii); and wherein Xaa1, Xaa2, Xaa3, Xaa4, Xaa5, Xaa6, Xaa7, Xaa8, or Xaa9is each optionally methylated.

2. The peptidic compound of claim 1 , wherein:Xaa3is Trp(7-F);Xaa6is NMe-Gly; andXaa9-R is a C-terminally amidated Pro or diFPro.

3. The peptidic compound of claim 1 , wherein:Xaa3is Trp(7-F);Xaa5is Tie; andXaa9-R is a C-terminally amidated Pro or diFPro.

4. The peptidic compound of any one of claims 1-3, wherein m is 1 .

5. The peptidic compound of any one of claims 1-4, wherein qj represents a reduced peptide bond.

6. The peptidic compound of any one of claims 1-5, wherein Xaa1is an N-terminal amino acid residue selected from D-Phe.

7. The peptidic compound of any one of claims 1-6, wherein Xaa2is Gin.

8. The peptidic compound of any one of claims 1-7, wherein Xaa3isTrp(7-F).

9. The peptidic compound of any one of claims 1-8, wherein Xaa4is Ala.

10. The peptidic compound of any one of claims 1 -9, wherein Xaa5is Vai or Tie.

11. The peptidic compound of any one of claims 1-10, wherein Xaa6is Gly or NMe-Gly.

12. The peptidic compound of any one of claims 1-11 , wherein Xaa7is His.

13. The peptidic compound of any one of claims 1-12, wherein Xaa8is Leu.

14. The peptidic compound of any one of claims 1-13, wherein Xaa9-R is a C-terminally amidated Pro or diFPro.

15. The peptidic compound of any one of claims 1-14, wherein:Xaa1is an N-terminal amino acid residue selected from D-Phe;Xaa2is Gin;Xaa4is Ala;Xaa5is Vai or Tie;Xaa6is Gly or NMe-Gly;Xaa8is Leu; andXaa9-R is a C-terminally amidated Pro or diFPro.

16. The peptidic compound of any one of claims 1-15, wherein:Xaa1is an N-terminal amino acid residue selected from D-Phe;Xaa2is Gin;Xaa3isTrp(7-F);Xaa4is Ala;Xaa5is Vai or Tie;Xaa6is Gly or NMe-Gly;Xaa7is His;Xaa8is Leu; andXaa9-R is a C-terminally amidated Pro or diFPro.

17. The peptidic compound of any one of claims 1-16, wherein:Xaa1is an N-terminal amino acid residue selected from D-Phe;Xaa2is Gin;Xaa3isTrp(7-F);Xaa4is Ala;Xaa5is Vai or Tie;Xaa6is Gly or NMe-Gly;Xaa7is His;Xaa8is Leu;Xaa9-R is a C-terminally amidated Pro or diFPro; m is 1 ; and qj represents a reduced peptide bond.

18. The peptidic compounds of any one of claims 1-17, wherein at least one of Xaa1, Xaa2, Xaa3, Xaa4, Xaa5, Xaa6, Xaa7, Xaa8, or Xaa9is methylated.

19. The peptidic compounds of any one of claims 1-18, wherein the peptidic compounds do not include an albumin binder Ralb.

20. The peptidic compound of any one of claims 1-19, wherein Rradn6-[linker]-RL- is DOTA-Pip-.21 . The peptidic compound of any one of claims 1-20, wherein at least one Rradis a radiometal chelator wherein the radiometal chelator is optionally bound to a radiometal, a radionuclide-bound metal, or a radionuclide-bound metal-containing prosthetic group.

22. The peptidic compound of claim 21 , wherein the radiometal chelator is DOTA and derivatives; DOTAGA; NOTA; NODAGA; NODASA; CB-DO2A; 3p-C-DEPA; TCMC; DO3A; DTPA and DTPA analogues optionally selected from CHX-A”-DTPA and 1 B4M-DTPA; TETA; NOPO; Me-3,2-HOPO; CB-TE1A1 P; CB-TE2P; MM-TE2A; DM-TE2A; sarcophagine and sarcophagine derivatives optionally selected from SarAr, SarAr-NCS, diamSar, AmBaSar, and BaBaSar; TRAP; AAZTA; DATA and DATA derivatives; H2-macropa or a derivative thereof; H2dedpa, H4octapa, H4py4pa, H4Pypa, H2azapa, H5decapa, and other picolinic acid derivatives; CP256; PCTA; C-NETA; C-NE3TA; HBED; SHBED; BCPA; CP256; YM103; desferrioxamine (DFO) and DFO derivatives; H6phospa; a trithiol chelate; mercaptoacetyl; hydrazinonicotinamide; dimercaptosuccinic acid; 1 ,2-ethylenediylbis-L-cysteine diethyl ester; methylenediphosphonate; hexamethylpropyleneamineoxime; hexakis(methoxy isobutyl isonitrile), H4py4pa-phenyl-NCS, or Crown.

23. The peptidic compound of claim 21 or 22, wherein the radiometal chelator is bound by a radiometal, a radionuclide-bound metal, or a radionuclide-bound metal-containing prosthetic group, optionally selected from the group consisting of:68Ga,61Cu,64Cu,67Cu,67Ga,111ln,44Sc,86Y,89Zr, "Nb,177Lu,117mSn,165Er, "Y,227Th,225Ac,213Bi,212Bi,72As,77As,211At,203Pb,212Pb,47Sc,166Ho,188Re,186Re,149Pm,159Gd,105Rh,109Pd,198Au,199Au,175Yb,142Pr,114mln,94mTc, "mTc,149Tb,152Tb,155Tb,161Tb, and [18F]AIF.

24. The peptidic compound of any one of claims 1-23, wherein at least one Rradis a trifluoroborate containing prosthetic group BF3-R5-R4-, wherein R4is -(CH2)I_5- and optionally methylene, and wherein BF3-R5- forms:wherein R5aand R5bare each independently a C1-C5 linear or branched alkyl group,which the R in each pyridine substituted -OR, -SR, -NR-, -NHR or -NR2is independently a branched or linear C1-C5 alkyl, optionally wherein the fluorines in BF3-R5-R4- comprise18F.

25. The peptidic compound of any one of claims 1-24, wherein the linker and RLtogether form a linear or branched peptide linker (Xaa1o)i.2o, wherein each Xaa10is independently a proteinogenic or non-proteinogenic amino acid residue, wherein each peptide backbone amino group is independently optionally methylated, and wherein each non-proteinogenic amino acid residue is independently selected from Table A.

26. The peptidic compound of any one of claims 1-25, wherein n6 is 1 , and wherein the linker and RLtogether form a p-aminomethylaniline-diglycolic acid (pABzA-DIG) linker, a 4-amino-(1-carboxymethyl)piperidine (Pip) linker, a 9-amino-4,7-dioxanonanoic acid (dPEG2) linker, or a 4-(2-aminoethyl)-1-carboxymethyl-piperazine (Acp) linker, optionally wherein the linker and RLtogether form:

27. The peptidic compound of claim 1 , wherein the peptidic compound isoror a salt or a solvate thereof, wherein the compound is optionally conjugated by a radiometal, a radionuclide-bound metal, or a radionuclide-bound metal-containing prosthetic group.

28. The peptidic compound of claim 1 , wherein:Xaa1is an N-terminal amino acid residue selected from D-Phe;Xaa2is Gin;Xaa3is Trp(7-F);Xaa4is Ala;Xaa5is Vai or Tie;Xaa6is Gly or NMe-Gly;Xaa7is His;Xaa8is Leu;Xaa9-R is a C-terminally amidated Pro; m is 1 ; and qj represents a reduced peptide bond.

29. The peptidic compound of claim 23 or 27, wherein the radiometal, the radionuclide-bound metal, or the radionuclide-bound metal-containing prosthetic group is:

30. The peptidic compound of claim 23 or 27, wherein the radiometal, the radionuclide-bound metal, or the radionuclide-bound metal-containing prosthetic group is:165Er,212Bi,211At,166Ho,149Pm,159Gd,105Rh,109Pd,198Au,199Au,175Yb,142Pr,177Lu,111ln,213Bi,47Sc,225Ac,117mSn,153Sm,149Tb,161Tb,224Ra,223Ra,212Pb,227Th,223Ra,77As,186Re,188Re,67Cu, or64Cu.31 . A pharmaceutical composition comprising a peptidic compound of any one of claims 1-30 and a pharmaceutically acceptable carrier or excipient.

32. A method of imaging gastrin-releasing peptide receptor (GRPR) in a subject, the method comprising: administering to the subject a peptidic compound of any one of claims 1-30 or a composition of claim 31 ; and imaging tissue of the subject.

33. A method of treating cancer in a subject comprising, administering to the subject in need thereof a peptidic compound of any one of claims 1 -28 and 30, or a composition of claim 31.

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