CCK2R-drug conjugates

TECHNICAL FIELD

The disclosure provided herein pertains to CCK2R-drug conjugates. In particular, the disclosure pertains to CCK2R-drug conjugates that target the delivery of drugs to a mammalian recipient. Also described are methods of making and using CCK2R-drug conjugates.

BACKGROUND

Cholecystokinin-2 receptors (also referred to as cholecystokinin-2 receptor, CCK2R, CCKBR or CCK₂) are regulatory peptides of the brain and gastrointestinal tract. CCK2R has been demonstrated to be overexpressed in certain human cancers. For example, CCK2R splice variants have been observed in human gastrointestinal and lung tumors. (See Korner, M. et al., J. Cell Mol. Med., 14, 4, 933-43 (2010)). Natural substrates of high affinity for cholecystokinin receptors include peptide hormones CCK and gastrin. C-terminal CCK peptide amide is selectively targeting CCK2R with 2 times higher affinity than binding to CCK1R. CCK2R has also been implicated in leukemia through immunoblotting of several leukemia cells lines. (See Stubbs, M. et al., Oncol. Rep., 14, 4, 1055-8 (2005).

The targeted delivery of drugs has been of recent interest, especially in the area of cancer therapy. Among the most well studied drug conjugates are anti-body drug conjugates (also known as ADCs) that have been designed as targeted therapies for cancer. (See Ducry, L. et al., Bioconjugate Chemistry, 21, 1, 5-13 (2010)). Examples of approved ADC treatments for cancer include Adcetris®, and Kadcyla®. Another promising avenue for the targeted delivery of drugs that has gained significant interest is the delivery of drug conjugates to a target cell through the binding of a receptor with a ligand. One example of such an approach is the delivery of a drug conjugate to a vitamin receptor through a vitamin receptor binding ligand. See for example, drug conjugates of folate described in U.S. Pat. No. 7,601,332.

The development of novel drug conjugates for delivery of therapeutic agents to molecular targets associated with cancer cells continues to be of great interest. Here we report the design and synthesis of novel CCK2-receptor drug conjugates.

SUMMARY

In one aspect, the disclosure provides conjugates of the formula A-L-B, or a pharmaceutically acceptable salt thereof, wherein A is a drug (D) or an imaging agent (I), L is a linker, and B is a binding ligand of CCK2R.

In one aspect, the disclosure provides conjugates of the formula D-L-B, or a pharmaceutically acceptable salt thereof, wherein D is a drug, L is a linker comprising at least one releasable linker (L¹), and B is a binding ligand of CCK2R.

In one aspect, the disclosure provides conjugates of the formula I-L-B, or a pharmaceutically acceptable salt thereof, wherein I is an imaging, L is a linker, and B is a binding ligand of CCK2R.

In another aspect, the disclosure provides pharmaceutical compositions comprising a therapeutically effective amount of the conjugates described herein, or a pharmaceutically acceptable salt thereof, and at least on excipient.

In another aspect, the disclosure provides a method of treating abnormal cell growth in a mammal, including a human, the method comprising administering to the mammal any of the conjugates or compositions described herein.

In another aspect, the disclosure provides uses of conjugates or compositions as described herein in the preparation of medicament for treating abnormal cell growth in a mammal.

In another aspect, the disclosure provides conjugates or compositions as described herein for the treatment abnormal cell growth in a mammal.

The conjugates of the present disclosure can be described as embodiments in any of the following enumerated clauses. It will be understood that any of the embodiments described herein can be used in connection with any other embodiments described herein to the extent that the embodiments do not contradict one another.

1. A conjugate of the formula A-L-B, or a pharmaceutically acceptable salt thereof, wherein A is a drug (D) or imaging agent (I), L is a linker, and B is a binding ligand of CCK2R.

1a. A conjugate of the formula D-L-B, or a pharmaceutically acceptable salt thereof, wherein D is a drug, L is a linker comprising at least one releasable linker (L¹), and B is a binding ligand of CCK2R.

1b. A conjugate of the formula I-L-B, or a pharmaceutically acceptable salt thereof, wherein I is an imaging agent, L is a linker, and B is a binding ligand of CCK2R.

1c. The conjugate of clause 1, having the formula

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wherein R is H, SO₃⁻ or SO₃^M, wherein M is a counter-ion, L is a linker comprising a disulfide moiety, and D is a drug, or a pharmaceutically acceptable salt thereof.

1d. The conjugate of clause 1, having the formula

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wherein R is H, SO₃⁻ or SO₃^M, wherein M is a counter-ion, L is a linker, and I is an imaging agent, or a pharmaceutically acceptable salt thereof.

1e. The conjugate of clause 1, having the formula

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wherein

Y is a bond or a C₁-C₆alkyl;

each of R⁴⁶, R⁴⁷, R⁴⁸and R⁴⁹is independently selected from the group consisting of H, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl and C₃-C₆cycloalkyl, wherein each hydrogen atom in C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl and C₃-C₆cycloalkyl is independently optionally substituted by halogen, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl, —OR⁵⁰, —OC(O)R⁵⁰, —OC(O)NR⁵⁰R^50′, —OS(O)R⁵⁰, —OS(O)₂R⁵⁰, —SR⁵⁰, —S(O)R⁵⁰, —S(O)₂R⁵⁰, —S(O)NR⁵⁰R^50′, —S(O)₂NR⁵⁰R^50′, —OS(O)NR⁵⁰R^50′, —OS(O)₂NR⁵⁰R^50′, —NR⁵⁰R^50′, —NR⁵⁰C(O)R⁵¹, —NR⁵⁰C(O)OR⁵¹, —NR⁵⁰C(O)NR⁵¹R^51′, —NR⁵⁰S(O)R⁵¹, —NR⁵⁰S(O)₂R⁵¹, —NR⁵⁰S(O)NR⁵¹R^51′, —NR⁵⁰S(O)₂NR⁵¹R^51′, —C(O)R⁵⁰, —C(O)OR⁵⁰or —C(O)NR⁵⁰R^50′; and

each R⁵⁰, R^50′, R⁵¹and R^51′is independently H, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl or C₃-C₆cycloalkyl;

L is a linker comprising a disulfide moiety, and D is a drug, or a pharmaceutically acceptable salt thereof.

2. The conjugate of clause 1 to 1e, or a pharmaceutically acceptable salt thereof, wherein R is H.

3. The conjugate of clause 1 to 1e, or a pharmaceutically acceptable salt thereof, wherein R is SO₃⁻ or SO₃M, wherein M is a counter-ion.

4. The conjugate of any one of clauses 1 to 3, or a pharmaceutically acceptable salt thereof, wherein L further comprises a polyether moiety.

5. The conjugate of any one of the preceding clauses, or a pharmaceutically acceptable salt thereof, wherein L further comprises a hydrazine moiety.

6. The conjugate of any one of the preceding clauses, wherein L further comprises one or more amino acids.

7. The conjugate of clause 6, or a pharmaceutically acceptable salt thereof, wherein at least one amino acid is in the D-configuration.

8. The conjugate of clause 6, or a pharmaceutically acceptable salt thereof, wherein at least one amino acid is in the L-configuration.

9. The conjugate of any one of the preceding clauses, or a pharmaceutically acceptable salt thereof, wherein L further comprises one or more amino acids selected from the group consisting of L-asparagine, L-arginine, L-glycine, L-aspartic acid, L-glutamic acid, L-glutamine, L-cysteine, L-alanine, L-valine, L-leucine, L-isoleucine, 3-amino-L-alanine, D-asparagine, D-arginine, D-glycine, D-aspartic acid, D-glutamic acid, D-glutamine, D-cysteine, D-alanine, D-valine, D-leucine, D-isoleucine and 3-amino-D-alanine.

10. The conjugate of any one of the preceding clauses, or a pharmaceutically acceptable salt thereof, wherein L further comprises at least two amino acids selected from the group consisting of L-asparagine, L-arginine, L-glycine, L-aspartic acid, L-glutamic acid, L-glutamine, L-cysteine, L-alanine, L-valine, L-leucine, L-isoleucine and 3-amino-L-alanine.

11. The conjugate of any one of the preceding clauses, or a pharmaceutically acceptable salt thereof, wherein D is a drug selected from the group consisting of a vinca alkaloid, a cryptophycin, bortezomib, thiobortezomib, a tubulysin, aminopterin, rapamycin, paclitaxel, docetaxel, doxorubicin, daunorubicin, everolimus, α-amanatin, verucarin, didemnin B, geldanomycin, purvalanol A, ispinesib, budesonide, dasatinib, an epothilone, a maytansine, and a tyrosine kinase inhibitor.

12. The conjugate of any one of the preceding clauses, or a pharmaceutically acceptable salt thereof, wherein D, when present, is a tubulysin.

13. The conjugate of any one of the preceding clauses, or a pharmaceutically acceptable salt thereof, wherein D, when present, is a tetrapeptide of the formula I

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wherein

R¹, R³, R^3′and R^3″are each independently selected from the group consisting of H, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl and C₃-C₆cycloalkyl, wherein each hydrogen atom in C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl and C₃-C₆cycloalkyl is independently optionally substituted by halogen, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl, —OR¹³, —OC(O)R¹³, —OC(O)NR¹³R^13′, —OS(O)R¹³, —OS(O)₂R¹³, —SR¹³, —SC(O)R¹³, —S(O)R¹³, —S(O)₂R¹³, —S(O)₂OR¹³, —S(O)NR¹³R^13′, —S(O)₂NR¹³R^13′, —OS(O)NR¹³R^13′, —OS(O)₂NR¹³R^13′, —NR³R^3′, —N R¹³C(O)R¹⁴, —NR¹³C(O)OR¹⁴, —NR¹³C(O)NR¹⁴R^14′, —NR¹³S(O)R¹⁴, —NR¹³S(O)₂R¹⁴, —NR¹³S(O)NR¹³R^14′, —NR¹³S(O)₂NR¹⁴R^14′, —P(O)(OR¹³)₂, —C(O)R¹³, —C(O)OR¹³or —C(O)NR¹³R^13′;

R², R⁴and R¹²are each independently selected from the group consisting of H, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl;

R⁵and R⁶are each independently selected from the group consisting of H, halogen, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, —OR¹⁵, —SR¹⁵, —OC(O)R¹⁵, —OC(O)NR¹⁵R^15′, and —NR¹⁵R^15′, wherein each hydrogen atom in C₁-C₆alkyl, C₂-C₆alkenyl and C₂-C₆alkynyl is independently optionally substituted by halogen, —OR¹⁶, —SR¹⁶, —NR¹⁶R^16′, C(O)R¹⁶, —C(O)OR¹⁶or —C(O)NR¹⁶R^16′; or R⁵and R⁶taken together with the carbon atom to which they are attached form a —C(O)—;

each R⁷, R⁸, R⁹, R¹⁰and R¹¹is independently selected from the group consisting of H, halogen, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, —CN, —NO₂, —NCO, —OR¹⁷, —SR¹⁷, —S(O)₂OR¹⁷, —NR¹⁷R^17′, —P(O)(OR¹⁷)₂, —C(O)R¹⁷, —C(O)OR¹⁷and —C(O)NR¹⁷R^17′, wherein each hydrogen atom in C₁-C₆alkyl, C₂-C₆alkenyl and C₂-C₆alkynyl is independently optionally substituted by halogen, —OR¹⁸, —SR¹⁸, —NR¹⁸R^18′, —C(O)R¹⁸, —C(O)OR¹⁸or —C(O)NR¹⁸R^18′;

each R¹³, R^13′, R¹⁴, R^14′, R¹⁵, R^15′, R¹⁶, R^16′, R¹⁷and R^17′is independently selected from the group consisting of H, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl and 5- to 7-membered heteroaryl, wherein each hydrogen atom in C₁-C₇alkyl, C₂-C₇alkenyl, C₂-C₇alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, or 5- to 7-membered heteroaryl is independently optionally substituted by halogen, —OH, —SH, —NH₂or —CO₂H;

each R¹⁸and R^18′is independently selected from the group consisting of H, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl —C(O)R¹⁹, —P(O)(OR¹⁹)₂, and —S(O)₂OR¹⁹;

each R¹⁹is independently selected from H, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl and 5- to 7-membered heteroaryl; and

t is 1, 2 or 3,

wherein * is a covalent bond.

14. The conjugate of clause 13, or a pharmaceutically acceptable salt thereof, wherein t is 2.

15. The conjugate of clause 13 or 14, or a pharmaceutically acceptable salt thereof, wherein R^1ais C₁-C₆alkyl.

16. The conjugate of any one of clauses 13 to 15, or a pharmaceutically acceptable salt thereof, wherein R¹is methyl.

17. The conjugate of any one of clauses 13 to 16, or a pharmaceutically acceptable salt thereof, wherein R²is C₁-C₆alkyl.

18. The conjugate of any one of clauses 13 to 17, or a pharmaceutically acceptable salt thereof, wherein R²is sec-butyl.

19. The conjugate of any one of clauses 13 to 18, or a pharmaceutically acceptable salt thereof, wherein R³is C₁-C₆alkyl, wherein each hydrogen atom in C₁-C₆alkyl is independently optionally substituted by —OC(O)R¹³and wherein R¹³is C₁-C₆alkyl.

20. The conjugate of any one of clauses 13 to 19, or a pharmaceutically acceptable salt thereof, wherein R⁴is C₁-C₆alkyl.

21. The conjugate of any one of clauses 13 to 20, or a pharmaceutically acceptable salt thereof, wherein R⁴is iso-propyl.

22. The conjugate of any one of clauses 13 to 21, or a pharmaceutically acceptable salt thereof, wherein R⁵is —OC(O)R¹⁵.

23. The conjugate of clause 22, or a pharmaceutically acceptable salt thereof, wherein R¹⁵is methyl.

24. The conjugate of any one of clauses 13 to 23, or a pharmaceutically acceptable salt thereof, wherein R⁶is H.

25. The conjugate of any one of clauses 13 to 24, or a pharmaceutically acceptable salt thereof, wherein R⁷, R⁸, R¹⁰and R¹¹are H.

26. The conjugate of any one of clauses 13 to 25, or a pharmaceutically acceptable salt thereof, wherein R⁷is —OH.

27. The conjugate of any one of clauses 13 to 26, or a pharmaceutically acceptable salt thereof, wherein R¹²is C₁-C₆alkyl.

28. The conjugate of any one of clauses 13 to 27, or a pharmaceutically acceptable salt thereof, wherein R¹²is methyl.

29. The conjugate of any one of clauses 13 to 28, or a pharmaceutically acceptable salt thereof, wherein R^3′and R^3″ are H.

30. The conjugate of any one of clauses 13 to 29, or a pharmaceutically acceptable salt thereof, wherein D is a tetrapeptide of the formula

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31. The conjugate of any one of clauses 13 to 30, or a pharmaceutically acceptable salt thereof, wherein D is a tetrapeptide of the formula

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32. The conjugate of any one of the preceding clauses, or a pharmaceutically acceptable salt thereof, wherein L comprises a moiety L¹of the formula selected from the group consisting of

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wherein

each R³¹, R^31′ and R^31″is independently selected from the group consisting of H, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl and C₃-C₆cycloalkyl, wherein each hydrogen atom in C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl and C₃-C₆cycloalkyl is independently optionally substituted by halogen, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl, —OR³², OC(O)R³², —OC(O)NR³²R^32′, —OS(O)R³², —OS(O)₂R³², —SR³², —S(O)R³², —S(O)₂R³², —S(O)NR³²R^32′, —S(O)₂NR³²R^32′, —OS(O)NR³²R^32′, —OS(O)₂NR³²R^32′, —NR³²R^32′, —NR³²C(O)R³³, —NR³²C(O)OR³³, —NR³²C(O)NR³³R^33′, —NR³²S(O)R³³, —NR³²S(O)₂R³³, —NR³²S(O)NR³³R^33′, —NR³²S(O)₂NR³³R^33′, —NR³⁴C(O)R³², —C(O)OR³²or —C(O)NR³²R^32′;

each X⁶is independently C₁-C₆alkyl or C₆-C₁₀aryl(C₁-C₆alkyl), wherein each hydrogen atom in C₁-C₆alkyl and C₆-C₁₀aryl(C₁-C₆alkyl) is independently optionally substituted by halogen, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl, —OR³⁴, —OC(O)R³⁴, —OC(O)NR³⁴R^34′, —OS(O)R³⁴, —OS(O)₂R³⁴, —SR³⁴, —S(O)R³⁴, —S(O)₂R³⁴, —S(O)NR³⁴R^34′, —S(O)₂NR³⁴R^34′, —OS(O)NR³⁴R^34′, —OS(O)₂NR³⁴R^34′, —NR³⁴R^34′, —NR^{3 4}C(O)R³⁵, —NR³⁴C(O)OR³⁵, —NR³⁴C(O)NR³⁵R^35′, —NR³⁴S(O)R³⁵, —NR³⁴S(O)₂R³⁵, —NR³⁴S(O)NR³⁵R^35′, —NR³⁴S(O)₂NR³⁵R^35′, —C(O)R³⁴, —C(O)OR³⁴or —C(O)NR³⁴R^34′;

each R³², R^32′, R³³, R^33′, R³⁴, R^34′, R³⁵and R^35′is independently selected from the group consisting of H, C₁-C₇alkyl, C₂-C₇alkenyl, C₂-C₇alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, and 5- to 7-membered heteroaryl;

each R³⁹, R^39′, R⁴⁰and R^40′is independently selected from the group consisting of H, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl and C₃-C₆cycloalkyl, wherein each hydrogen atom in C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl and C₃-C₆cycloalkyl is independently optionally substituted by halogen, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl, —OR⁴⁴, —OC(O)R⁴⁴, —OC(O)NR⁴⁴R^44′, —OS(O)R⁴⁴, —OS(O)₂R⁴⁴, —SR⁴⁴, —S(O)R⁴⁴, —S(O)₂R⁴⁴, —S(O)NR⁴⁴R^44′, —S(O)₂NR⁴⁴R^44′, —OS(O)NR⁴⁴R^44′, —OS(O)₂NR⁴⁴R^44′, —NR⁴⁴R^44′, —NR⁴⁴C(O)R⁴⁵, —NR⁴⁴C(O)OR⁴⁵, —NR⁴C(O)NR⁴⁵R^45′, —NR⁴⁴S(O)R⁴⁵, —NR⁴⁴S(O)₂R⁴⁵, —NR⁴⁴S(O)NR⁴⁵R^45′, —NR⁴⁴S(O)₂NR⁴⁵R^45′, —C(O)R⁴⁴, —C(O)OR⁴⁴or —C(O)NR⁴⁴R^44′;

each R⁴¹is independently selected from the group consisting of H, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl and C₃-C₆cycloalkyl, wherein each hydrogen atom in C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl and C₃-C₆cycloalkyl is independently optionally substituted by halogen, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl, —OR⁴², OC(O)R⁴², —OC(O)NR⁴²R^42′, —OS(O)R⁴², —OS(O)₂R⁴², —SR⁴², —S(O)R⁴², S(O)₂R⁴², —S(O)NR⁴²R^42′, —S(O)₂NR⁴²R^42′, —OS(O)NR⁴²R^42′, —OS(O)₂NR⁴²R^42′, —NR⁴²R^42′, —NR⁴²C(O)R⁴³, —NR⁴²C(O)OR⁴³, —NR⁴²C(O)NR⁴³R^43′, —NR⁴²S(O)R⁴³, —NR⁴²S(O)₂R⁴³, —NR⁴²S(O)NR⁴³R^43′, —NR⁴²S(O)₂NR⁴³R^43′, —C(O)R⁴², —C(O)OR⁴²or —C(O)NR⁴²R^42′;

each R⁴², R^42′, R⁴³, R^43′, R⁴⁴, R^44′, R⁴⁵, and R^45′is independently selected from the group consisting of H, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl and 5- to 7-membered heteroaryl; and

u is 1, 2, 3 or 4;

wherein * is a covalent bond.

32a. The conjugate of any one of the preceding clauses, or a pharmaceutically acceptable salt thereof, wherein L comprises a moiety L¹of the formula selected from the group consisting of

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wherein

each X⁶is independently C₁-C₆alkyl or C₆-C₁₀aryl(C₁-C₆alkyl), wherein each hydrogen atom in C₁-C₆alkyl and C₆-C₁₀aryl(C₁-C₆alkyl) is independently optionally substituted by halogen, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl, —OR³⁴, —OC(O)R³⁴, —OC(O)NR³⁴R^34′, —OS(O)R³⁴, —OS(O)₂R³⁴, —SR³⁴, —S(O)R³⁴, —S(O)₂R³⁴, —S(O)NR³⁴R^34′, —S(O)₂NR³⁴R^34′, —OS(O)NR³⁴R^34′, —OS(O)₂NR³⁴R^34′, —NR³⁴R^34′, —NR³⁴C(O)R³⁵, —NR³⁴C(O)OR³⁵, —NR³⁴C(O)NR³⁵R^35′, —NR³⁴S(O)R³⁵, —NR³⁴S(O)₂R³⁵, —NR³⁴S(O)NR³⁵R^35′, —NR³⁴S(O)₂NR³⁵R^35′, —C(O)R³⁴, —C(O)OR³⁴or —C(O)NR³⁴R^34′;

each R³⁹, R^39′, R⁴⁰and R^40′is independently selected from the group consisting of H, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl and C₃-C₆cycloalkyl, wherein each hydrogen atom in C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl and C₃-C₆cycloalkyl is independently optionally substituted by halogen, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl, —OR⁴⁴, —OC(O)R⁴⁴, —OC(O)NR⁴⁴R^44′, —OS(O)R⁴⁴, —OS(O)₂R⁴⁴, —SR⁴⁴, —S(O)R⁴⁴, —S(O)₂R⁴⁴, —S(O)NR⁴⁴R^44′, —S(O)₂NR⁴⁴R^44′, —OS(O)NR⁴⁴R^44′, —OS(O)₂NR⁴⁴R^44′, —NR⁴⁴R^44′, —NR⁴⁴C(O)R⁴⁵, NR⁴⁴C(O)OR⁴⁵, —NR⁴⁴C(O)NR⁴⁵R^45′, —NR⁴⁴S(O)R⁴⁵, —NR⁴⁴S(O)₂R⁴⁵, —NR⁴⁴S(O)NR⁴⁵R^45′, —NR⁴⁴S(O)₂NR⁴⁵R^45′, —C(O)R⁴⁴, —C(O)OR⁴⁴or —C(O)NR⁴⁴R^44′;

each R⁴¹is independently selected from the group consisting of H, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl and C₃-C₆cycloalkyl, wherein each hydrogen atom in C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl and C₃-C₆cycloalkyl is independently optionally substituted by halogen, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl, —OR⁴², OC(O)R⁴², —OC(O)NR⁴²R^42′, —OS(O)R⁴², —OS(O)₂R⁴², —SR⁴², —S(O)R⁴², —S(O)₂R⁴², —S(O)NR⁴²R^42′, —S(O)₂NR⁴²R^42′, —OS(O)NR⁴²R^42′, —OS(O)₂NR⁴²R^42′, —NR⁴²R^42′, —NR⁴²C(O)R⁴³, —NR⁴²C(O)OR⁴³, —NR⁴²C(O)NR⁴³R^43′, —NR⁴²S(O)R⁴³, —NR⁴²S(O)₂R⁴³, —NR⁴²S(O)NR⁴³R^43′, —NR⁴²S(O)₂NR⁴³R^43′, —C(O)R⁴², —C(O)OR⁴²or —C(O)NR⁴²R^42′;

u is 1, 2, 3 or 4;

wherein * is a covalent bond.

33. The conjugate of any one of the preceding clauses, or a pharmaceutically acceptable salt thereof, wherein L comprises a moiety L¹of the formula selected from the group consisting of

embedded image

wherein

each R³¹, R^31′and R^31″is independently selected from the group consisting of H, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl and C₃-C₆cycloalkyl, wherein each hydrogen atom in C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl and C₃-C₆cycloalkyl is independently optionally substituted by halogen, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl, —OR³², OC(O)R³², —OC(O)NR³²R^32′, —OS(O)R³², —OS(O)₂R³², —SR³², —S(O)R³², —S(O)₂R³², —S(O)NR³²R^32′, —S(O)₂NR³²R^32′, —OS(O)NR³²R^32′, —OS(O)₂NR³²R^32′, —NR³²R^32′, —NR³²C(O)R³³, —NR³²C(O)OR³³, —NR³²C(O)NR³³R^33′, —NR³²S(O)R³³, —NR³²S(O)₂R³³, —NR³²S(O)NR³³R^33′, —NR³²S(O)₂NR³³R^33′, —C(O)R³², —C(O)OR³²or —C(O)NR³²R^32′;

each X⁶is independently C₁-C₆alkyl or C₆-C₁₀aryl(C₁-C₆alkyl), wherein each hydrogen atom in C₁-C₆alkyl and C₆-C₁₀aryl(C₁-C₆alkyl) is independently optionally substituted by halogen, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl, —OR³⁴, —OC(O)R³⁴, —OC(O)NR³⁴R^34′, —OS(O)R³⁴, —OS(O)₂R³⁴, —SR³⁴, —S(O)R³⁴, —S(O)₂R³⁴, —S(O)NR³⁴R^34′, —S(O)₂NR³⁴R^34′, —OS(O)NR³⁴R^34′, —OS(O)₂NR³⁴R^34′, —NR³⁴R^34′, —NR³⁴C(O)R³⁵, —NR³⁴C(O)OR³⁵, —NR³⁴C(O)NR³⁵R^35′, —NR³⁴S(O)R³⁵, —NR³⁴S(O)₂R³⁵, —NR³⁴S(O)NR³⁵R^35′, —NR³⁴S(O)₂NR³⁵R^35′, —C(O)R³⁴, —C(O)OR³⁴or —C(O)NR³⁴R^34′;

34. The conjugate of clause 33, or a pharmaceutically acceptable salt thereof, wherein L comprises a moiety L¹of the formula

embedded image

wherein

each R³¹, R^31′and R^31″is independently selected from the group consisting of H, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl and C₃-C₆cycloalkyl, wherein each hydrogen atom in C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl and C₃-C₆cycloalkyl is independently optionally substituted by halogen, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl, —OR³², OC(O)R³², —OC(O)NR³²R^32′, —OS(O)R³², —OS(O)₂R³², —SR³², —S(O)R³², —S(O)₂R³², —S(O)NR³²R^32′, —S(O)₂NR³²R^32′, —OS(O)NR³²R^32′, —OS(O)₂NR³²R^32′, —NR³²R^32′, —NR³²C(O)R³³, —NR³²C(O)OR³³, —NR³²C(O)NR³³R^33′, —NR³²S(O)R³³, —NR³²S(O)₂R³³, —NR³²S(O)NR³³R^33′, —NR³²S(O)₂NR³³R^33′, —C(O)R³², —C(O)OR³²or —C(O)NR³²R^32′;

each X⁶is independently C₁-C₆alkyl or C₆-C₁₀aryl(C₁-C₆alkyl), wherein each hydrogen atom in C₁-C₆alkyl and C₆-C₁₀aryl(C₁-C₆alkyl) is independently optionally substituted by halogen, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl, —OR³⁴, —OC(O)R³⁴, —OC(O)NR³⁴R^34′, —OS(O)R³⁴, —OS(O)₂R³⁴, —SR³⁴, —S(O)R³⁴, —S(O)₂R³⁴, —S(O)NR³⁴R^34′, —S(O)₂NR³⁴R^34′, —OS(O)NR³⁴R^34′, —OS(O)₂NR³⁴R^34′, —NR³⁴R^34′, —NR³⁴C(O)R³⁵, —NR³⁴C(O)OR³⁵, —NR³⁴C(O)NR³⁵R^35′, —NR³⁴S(O)R³⁵, —NR³⁴S(O)₂R³⁵, —NR³⁴S(O)NR³⁵R^35′, —NR³⁴S(O)₂NR³⁵R^35′, —C(O)R³⁴, —C(O)OR³⁴or —C(O)NR³⁴R^34′;

35. The conjugate of clause 33, or a pharmaceutically acceptable salt thereof, wherein L comprises a moiety L¹of the formula

embedded image

wherein

each X⁶is independently C₁-C₆alkyl or C₆-C₁₀aryl(C₁-C₆alkyl), wherein each hydrogen atom in C₁-C₆alkyl and C₆-C₁₀aryl(C₁-C₆alkyl) is independently optionally substituted by halogen, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl, —OR³⁴, —OC(O)R³⁴, —OC(O)NR³⁴R^34′, —OS(O)R³⁴, —OS(O)₂R³⁴, —SR³⁴, —S(O)R³⁴, —S(O)₂R³⁴, —S(O)NR³⁴R^34′, —S(O)₂NR³⁴R^34′, —OS(O)NR³⁴R^34′, —OS(O)₂NR³⁴R^34′, —NR³⁴R^34′, —NR³⁴C(O)R³⁵, —NR³⁴C(O)OR³⁵, —NR³⁴C(O)NR³⁵R^35′, —NR³⁴S(O)R³⁵, —NR³⁴S(O)₂R³⁵, —NR³⁴S(O)NR³⁵R^35′, —NR³⁴S(O)₂NR³⁵R^35′, —C(O)R³⁴, —C(O)OR³⁴or —C(O)NR³⁴R^34′;

36. The conjugate of clause 33, or a pharmaceutically acceptable salt thereof, wherein L comprises a moiety L¹of the formula

embedded image

wherein

each R³¹, R^31′and R^31″is independently selected from the group consisting of H, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl and C₃-C₆cycloalkyl, wherein each hydrogen atom in C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl and C₃-C₆cycloalkyl is independently optionally substituted by halogen, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl, —OR³², OC(O)R³², —OC(O)NR³²R^32′, —OS(O)R³², —OS(O)₂R³², —SR³², —S(O)R³², —S(O)₂R³², —S(O)NR³²R^32′, —S(O)₂NR³²R^32′, —OS(O)NR³²R^32′, —OS(O)₂NR³²R^32′, —NR³²R^32′, —NR³²C(O)R³³, —NR³²C(O)OR³³, —NR³²C(O)NR³³R^33′, —NR³²S(O)R³³, —NR³²S(O)₂R³³, —NR³²S(O)NR³³R^33′, —NR³²S(O)₂NR³³R^33′, —C(O)R³², —C(O)OR³²or —C(O)NR³²R^32′;

each X⁶is independently C₁-C₆alkyl or C₆-C₁₀aryl(C₁-C₆alkyl), wherein each hydrogen atom in C₁-C₆alkyl and C₆-C₁₀aryl(C₁-C₆alkyl) is independently optionally substituted by halogen, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl, —OR³⁴, —OC(O)R³⁴, —OC(O)NR³⁴R^34′, —OS(O)R³⁴, —OS(O)₂R³⁴, —SR³⁴, —S(O)R³⁴, —S(O)₂R³⁴, —S(O)NR³⁴R^34′, —S(O)₂NR³⁴R^34′, —OS(O)NR³⁴R^34′, —OS(O)₂NR³⁴R^34′, —NR³⁴R^34′, —NR³⁴C(O)R³⁵, —NR³⁴C(O)OR³⁵, —NR³⁴C(O)NR³⁵R^35′, —NR³⁴S(O)R³⁵, —NR³⁴S(O)₂R³⁵, —NR³⁴S(O)NR³⁵R^35′, —NR³⁴S(O)₂NR³⁵R^35′, —C(O)R³⁴, —C(O)OR³⁴or —C(O)NR³⁴R^34′;

37. The conjugate of any one of clauses 1 to 32, or a pharmaceutically acceptable salt thereof, wherein L comprises a moiety L¹of the formula selected from the group consisting of

embedded image

wherein

each R³¹is independently selected from the group consisting of H, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl and C₃-C₆cycloalkyl, wherein each hydrogen atom in C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl and C₃-C₆cycloalkyl is independently optionally substituted by halogen, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl, —OR³², OC(O)R³², —OC(O)NR³²R^32′, —OS(O)R³², —OS(O)₂R³², —SR³², —S(O)R³², —S(O)₂R³², —S(O)NR³²R^32′, —S(O)₂NR³²R^32′, —OS(O)NR³²R^32′, —OS(O)₂NR³²R^32′, —NR³²R^32′, —NR³²C(O)R³³, —NR³²C(O)OR³³, —NR³²C(O)NR³³R^33′, —NR³²S(O)R³³, —NR³²S(O)₂R³³, —NR³²S(O)NR³³R^33′, —NR³²S(O)₂NR³³R^33′, —C(O)R³², —C(O)OR³²or —C(O)NR³²R^32′;

each X⁶is independently C₁-C₆alkyl or C₆-C₁₀aryl(C₁-C₆alkyl), wherein each hydrogen atom in C₁-C₆alkyl and C₆-C₁₀aryl(C₁-C₆alkyl) is independently optionally substituted by halogen, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl, —OR³⁴, —OC(O)R³⁴, —OC(O)NR³⁴R^34′, —OS(O)R³⁴, —OS(O)₂R³⁴, —SR³⁴, —S(O)R³⁴, —S(O)₂R³⁴, —S(O)NR³⁴R^34′, —S(O)₂NR³⁴R^34′, —OS(O)NR³⁴R^34′, —OS(O)₂NR³⁴R^34′, —NR³⁴R^34′, —NR³⁴C(O)R³⁵, —NR³⁴C(O)OR³⁵, —NR³⁴C(O)NR³⁵R^35′, —NR³⁴S(O)R³⁵, —NR³⁴S(O)₂R³⁵, —NR³⁴S(O)NR³⁵R^35′, —NR³⁴S(O)₂NR³⁵R^35′, —C(O)R³⁴, —C(O)OR³⁴or —C(O)NR³⁴R^34′;

38. The conjugate of clause 37, or a pharmaceutically acceptable salt thereof, wherein L comprises a moiety L¹of the formula

embedded image

wherein

each X⁶is independently C₁-C₆alkyl or C₆-C₁₀aryl(C₁-C₆alkyl), wherein each hydrogen atom in C₁-C₆alkyl and C₆-C₁₀aryl(C₁-C₆alkyl) is independently optionally substituted by halogen, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl, —OR³⁴, —OC(O)R³⁴, —OC(O)NR³⁴R^34′, —OS(O)R³⁴, —OS(O)₂R³⁴, —SR³⁴, —S(O)R³⁴, —S(O)₂R³⁴, —S(O)NR³⁴R^34′, —S(O)₂NR³⁴R^34′, —OS(O)NR³⁴R^34′, —OS(O)₂NR³⁴R^34′, —NR³⁴R^34′, —NR³⁴C(O)R³⁵, —NR³⁴C(O)OR³⁵, —NR³⁴C(O)NR³⁵R^35′, —NR³⁴S(O)R³⁵, —NR³⁴S(O)₂R³⁵, —NR³⁴S(O)NR³⁵R^35′, —NR³⁴S(O)₂NR³⁵R^35′, —C(O)R³⁴, —C(O)OR³⁴or —C(O)NR³⁴R^34′;

39. The conjugate of clause 37, or a pharmaceutically acceptable salt thereof, wherein L comprises a moiety L¹of the formula

embedded image

wherein

each X⁶is independently C₁-C₆alkyl or C₆-C₁₀aryl(C₁-C₆alkyl), wherein each hydrogen atom in C₁-C₆alkyl and C₆-C₁₀aryl(C₁-C₆alkyl) is independently optionally substituted by halogen, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl, —OR³⁴, —OC(O)R³⁴, —OC(O)NR³⁴R^34′, —OS(O)R³⁴, —OS(O)₂R³⁴, —SR³⁴, —S(O)R³⁴, —S(O)₂R³⁴, —S(O)NR³⁴R^34′, —S(O)₂NR³⁴R^34′, —OS(O)NR³⁴R^34′, —OS(O)₂NR³⁴R^34′, —NR³⁴R^34′, —C(O)R³⁵, —NR³⁴C(O)OR³⁵, —NR³⁴C(O)NR³⁵R^35′, —NR³⁴S(O)R³⁵, —NR³⁴S(O)₂R³⁵, —NR³⁴S(O)NR³⁵R^35′, —NR³⁴S(O)₂NR³⁵R^35′, —C(O)R³⁴, —C(O)OR³⁴or —C(O)NR³⁴R^34′;

40. The conjugate of clause 37, or a pharmaceutically acceptable salt thereof, wherein L comprises a moiety L¹of the formula

embedded image

wherein

each X⁶is independently C₁-C₆alkyl or C₆-C₁₀aryl(C₁-C₆alkyl), wherein each hydrogen atom in C₁-C₆alkyl and C₆-C₁₀aryl(C₁-C₆alkyl) is independently optionally substituted by halogen, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl, —OR³⁴, —OC(O)R³⁴, —OC(O)NR³⁴R^34′, —OS(O)R³⁴, —OS(O)₂R³⁴, —SR³⁴, —S(O)R³⁴, —S(O)₂R³⁴, —S(O)NR³⁴R^34′, —S(O)₂NR³⁴R^34′, —OS(O)NR³⁴R^34′, —OS(O)₂NR³⁴R^34′, —NR³⁴R^34′, —NR³⁴C(O)R³⁵, —NR³⁴C(O)OR³⁵, —NR³⁴C(O)NR³⁵R^35′, —NR³⁴S(O)R³⁵, —NR³⁴S(O)₂R³⁵, —NR³⁴S(O)NR³⁵R^35′, —NR³⁴S(O)₂NR³⁵R^35′, —C(O)R³⁴, —C(O)OR³⁴or —C(O)NR³⁴R³⁴R^34′;

41. The conjugate of any one of clauses 32 to 40, or a pharmaceutically acceptable salt thereof, wherein X⁶is C₁-C₆alkyl.

42. The conjugate of any one of clauses 32 to 41, or a pharmaceutically acceptable salt thereof, wherein R³¹is H.

43. The conjugate of any one of clauses 32 to 42, or a pharmaceutically acceptable salt thereof, wherein R^31′is H.

44. The conjugate of any one of clauses 32 to 43, or a pharmaceutically acceptable salt thereof, wherein R^31″is H.

45. The conjugate of any one of the preceding clauses, wherein L comprises a moiety L²of the formula

embedded image

wherein

R²⁰is selected from the group consisting of H, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, —C(O)R²³, —C(O)OR²³and —C(O)NR²³R^23′, wherein each hydrogen atom in C₁-C₆alkyl, C₂-C₆alkenyl and C₂-C₆alkynyl is independently optionally substituted by halogen, C₁-C₆alkyl, C₂-C₆alkenyl, and C₂-C₆alkynyl, —OR²⁴, —OC(O)R²⁴, —OC(O)NR²⁴R^24′, —OS(O)R²⁴, —OS(O)₂R²⁴, —SR²⁴, —S(O)R²⁴, —S(O)₂R²⁴, —S(O)NR²⁴R^24′, —S(O)₂NR²⁴R^24′, —OS(O)NR²⁴R^24′, —OS(O)₂NR²⁴R^24′, —NR²⁴R^24′, —NR²⁴C(O)R²⁵, —NR²⁴C(O)OR²⁵, —NR²⁴C(O)NR²⁵R^25′, —NR²⁴S(O)R²⁵, —NR²⁴S(O)₂R²⁵, —NR²⁴S(O)NR²⁵R^25′, —NR²⁴S(O)₂NR²⁵R^25′, C(O)R²⁴, —C(O)OR²⁴, or —C(O)NR²⁴R^24′;

each R²¹and R^21′is independently selected from the group consisting of H, halogen, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl, —OR²⁴, OC(O)R²⁴, —OC(O)NR²⁴R^24′, —OS(O)R²⁴, —OS(O)₂R²⁴, —SR²⁴, —S(O)R²⁴, —S(O)₂R²⁴, —S(O)NR²⁴R^24′, —S(O)₂NR²⁴R^24′, —OS(O)NR²⁴R^24′, —OS(O)₂NR²⁴R^24′, —NR²⁴R^24′, —NR²⁴C(O)R²⁵, —NR²⁴C(O)OR²⁵, —NR²⁴C(O)NR²⁵R^25′, —NR²⁴S(O)R²⁵, —NR²⁴S(O)₂R²⁵, —NR²⁴S(O)NR²⁵R^25′, —NR²⁴S(O)₂NR²⁵R^25′, —C(O)R²⁴, —C(O)OR²⁴and —C(O)NR²⁴R^24′, wherein each hydrogen atom in C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl and 5- to 7-membered heteroaryl is independently optionally substituted by halogen, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, —OR²⁴, —OC(O)R²⁴, —OC(O)NR²⁴R^24′, —OS(O)R²⁴, —OS(O)₂R²⁴, —SR²⁴, —S(O)R²⁴, —S(O)₂R²⁴, —S(O)NR²⁴R^24′, —S(O)₂NR²⁴R^24′, —OS(O)NR²⁴R^24′, —OS(O)₂NR²⁴R^24′, —NR²⁴R^24′, —NR²⁴C(O)R²⁵, —NR²⁴C(O)OR²⁵, NR²⁴C(O)NR²⁵R^25′, —NR²⁴S(O)R²⁵, —NR²⁴S(O)₂R²⁵, —NR²⁴S(O)NR²⁵R^25′, —NR²⁴S(O)₂NR²⁵R^25′, —C(O)R²⁴, —C(O)OR²⁴or —C(O)NR²⁴R^24′; or R²¹and R^21′may combine to form a C₄-C₆cycloalkyl or a 4- to 6-membered heterocycle, wherein each hydrogen atom in C₄-C₆cycloalkyl or 4- to 6-membered heterocycle is independently optionally substituted by halogen, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl, —OR²⁴, —OC(O)R²⁴, —OC(O)NR²⁴R^24′, —OS(O)R²⁴, —OS(O)₂R²⁴, —SR²⁴, —S(O)R²⁴, —S(O)₂R²⁴, —S(O)NR²⁴R^24′, —S(O)₂NR²⁴R^24′, —OS(O)NR²⁴R^24′, —OS(O)₂NR²⁴R^24′, —NR²⁴R^24′, —NR²⁴C(O)R²⁵, —NR²⁴C(O)OR²⁵, —NR²⁴C(O)NR²⁵R^25′, —NR²⁴S(O)R²⁵, —NR²⁴S(O)₂R²⁵, —NR²⁴S(O)NR²⁵R^25′, —NR²⁴S(O)₂NR²⁵R^25′, —C(O)R²⁴, —C(O)OR²⁴or —C(O)NR²⁴R^24′;

R²²is selected from the group consisting of H, D, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl, —OR²⁶, —OC(O)R²⁶, —OC(O)NR²⁶R^26′, —OS(O)R²⁶, —OS(O)₂R²⁶, —SR²⁶, —S(O)R²⁶, —S(O)₂R²⁶, —S(O)NR²⁶R^26′, —S(O)₂NR²⁶R^26′, —OS(O)NR²⁶R^26′, —OS(O)₂NR²⁶R^26′, —NR²⁶R^26′, —NR²⁶C(O)R²⁷, —NR²⁶C(O)OR²⁷, —NR²⁶C(O)NR²⁷R^27′, NR²⁶C(═NR^26″)NR²⁷R^27′, —NR²⁶S(O)R²⁷, —NR²⁶S(O)₂R²⁷, —NR²⁶S(O)NR²⁷R^27′, —NR²⁶S(O)₂NR²⁷R^27′, —C(O)R²⁶, —C(O)OR²⁶and —C(O)NR²⁶R^26′, wherein each hydrogen atom in C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl and 5- to 7-membered heteroaryl is independently optionally substituted by halogen, C₁-C₆alkyl, C₂-C₆alkenyl, —(CH₂)_pOR²⁸, —(CH₂)_p(OCH₂)_qOR²⁸, —(CH₂)_p(OCH₂CH₂)_qOR²⁸, —OR²⁹, —OC(O)R²⁹, —OC(O)NR²⁹R^29′, —OS(O)R²⁹, —OS(O)₂R²⁹, —(CH₂)_pOS(O)₂OR²⁹, —OS(O)₂OR²⁹, —SR²⁹, —S(O)R²⁹, —S(O)₂R²⁹, —S(O)NR²⁹R^29′, —S(O)₂NR²⁹R^29′, —OS(O)NR²⁹R^29′, —OS(O)₂NR²⁹R^29′, —NR²⁹R^29′, —NR²⁹C(O)R³⁰, —NR²⁹C(O)OR³⁰, —NR²⁹C(O)NR³⁰R^30′, —NR²⁹S(O)R³⁰, —NR²⁹S(O)₂R³⁰, —NR²⁹S(O)NR³⁰R^30′, —NR²⁹S(O)₂NR³⁰R^30′, —C(O)R²⁹, —C(O)OR²⁹or —C(O)NR²⁹R^29′;

each R²⁴, R^24′, R²⁵, R^25′, R²⁶, R^26′, R^26″, R²⁹, R^29′, R³⁰and R^30′is independently selected from the group consisting of H, D, C₁-C₇alkyl, C₂-C₇alkenyl, C₂-C₇alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl and 5- to 7-membered heteroaryl, wherein each hydrogen atom in C₁-C₇alkyl, C₂-C₇alkenyl, C₂-C₇alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, or 5- to 7-membered heteroaryl is independently optionally substituted by halogen, —OH, —SH, —NH₂or —CO₂H;

R²⁷and R^27′are each independently selected from the group consisting of H, C₁-C₉alkyl, C₂-C₉alkenyl, C₂-C₉alkynyl, C₃-C₆cycloalkyl, —(CH₂)_p(sugar), —(CH₂)_p(OCH₂CH₂)_q-(sugar) and —(CH₂)_p(OCH₂CH₂CH₂)_q(sugar);

R²⁸is H, D, C₁-C₇alkyl, C₂-C₇alkenyl, C₂-C₇alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl or sugar;

n is 1, 2, 3, 4 or 5;

p is 1, 2, 3, 4 or 5;

q is 1, 2, 3, 4 or 5; and

* is a covalent bond.

46. The conjugate of any of the preceding clauses, wherein L comprises a moiety L²of the formula

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wherein R²⁰, R²¹, R^21′, R²²and n are as described herein, or a pharmaceutically acceptable salt thereof.

47. The conjugate of any of the preceding clauses, wherein L comprises a moiety L²of the formula

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wherein R²⁰, n, p, q and r are as described herein, or a pharmaceutically acceptable salt thereof.

48. The conjugate of any one of the preceding clauses, or a pharmaceutically acceptable salt thereof, wherein L comprises one or more moiety L³of the formula

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wherein m is an integer from 1 to about 50, m1 is an integer from 1 to about 30, m2 is an integer from 1 to 20, and each * represents a covalent bond to the rest of the conjugate.

49. The conjugate of any one of the preceding clauses, or a pharmaceutically acceptable salt thereof, wherein L comprises at least one AA.

50. The conjugate of any one of the preceding clauses, or a pharmaceutically acceptable salt thereof, wherein L is of the formula

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wherein AA is an amino acid, R′ is selected from the group consisting of H, C₁-C₆alkyl, and —C(O)R″, R″ is selected from the group consisting of H, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl C₃-C₆cycloalkyl and C₆-C₁₀aryl, m is an integer between 1 and 50, and * is a covalent bond.

51. The conjugate of any one of clauses 1 to 49, or a pharmaceutically acceptable salt thereof, wherein L is of the formula

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52. The conjugate of clause 50 or 51, or a pharmaceutically acceptable salt thereof, wherein m is 2.

53. The conjugate of clause 50 or 51, or a pharmaceutically acceptable salt thereof, wherein m is 3.

54. The conjugate of clause 50 or 51, or a pharmaceutically acceptable salt thereof, wherein m is 12.

55. The conjugate of any one of clauses 1 to 49, or a pharmaceutically acceptable salt thereof, wherein L is of the formula -L³-AA-L²-AA-L²-L¹-.

56. The conjugate of any one of clauses 1 to 49, or a pharmaceutically acceptable salt thereof, wherein L is of the formula

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wherein m1 is an integer from 1 to about 30, and n is 2.

57. The conjugate of any one of clauses 1 to 49, or a pharmaceutically acceptable salt thereof, wherein L is of the formula -L³-AA-L²-AA-L²-AA-AA-L¹-.

58. The conjugate of any one of clauses 1 to 49, or a pharmaceutically acceptable salt thereof, wherein L is of the formula

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wherein m is an integer from about 1 to about 50, and n is 2.

59. The conjugate of any one of the preceding clauses, wherein AA is selected from the group consisting of Glu, Asp and Dap.

60. The conjugate of clause 1, or a pharmaceutically acceptable salt thereof, of the formula

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wherein m is 2.

61. The conjugate of clause 1, or a pharmaceutically acceptable salt thereof, of the formula

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wherein m1 is 3.

62. The conjugate of clause 1, or a pharmaceutically acceptable salt thereof, of the formula

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wherein m is 12.

63. The conjugate of clause 1, or a pharmaceutically acceptable salt thereof, of the formula

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wherein m is 2.

64. The conjugate of clause 1, having the formula

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or a pharmaceutically acceptable salt thereof.

65. The conjugate of clause 1, having the formula

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or a pharmaceutically acceptable salt thereof.

66. The conjugate of clause 1, having the formula

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67. A pharmaceutical composition, comprising a conjugate of any one of the preceding clauses, or a pharmaceutically acceptable salt thereof, and optionally at least one excipient.

68. A method of treating abnormal cell growth in a mammal, including a human, the method comprising administering to the mammal a conjugate of any one of clauses 1-65.

69. The method of clause 68, wherein the abnormal cell growth is cancer.

70. The method of clause 69, wherein the cancer is selected from the group consisting of lung cancer, small cell lung cancer (SCLC), non-small cell lung cancer (NSCLC), bronchopulmonary carcinoid, bone cancer, pancreatic cancer, pancreatic ductal adenocarcinomas, skin cancer, cancer of the head or neck, cutaneous or intraocular melanoma, uterine cancer, ovarian cancer, rectal cancer, cancer of the anal region, stomach cancer, colon cancer, colorectal cancer, colorectal ductal adenocarcinomas, breast cancer, uterine cancer, carcinoma of the fallopian tubes, carcinoma of the endometrium, carcinoma of the cervix, carcinoma of the vagina, carcinoma of the vulva, Hodgkin's Disease, cancer of the esophagus, cancer of the small intestine, cancer of the endocrine system, gastrointestinal cancer, insulinoma, ileal carcinoid, gastrointestinal stromal tumor (GIST), gastric ductal adenocarcinoma, cancer of the thyroid gland, cancer of the parathyroid gland, cancer of the adrenal gland, sarcoma of soft tissue, cancer of the urethra, cancer of the penis, prostate cancer, chronic or acute leukemia, lymphocytic lymphomas, cancer of the bladder, cancer of the kidney or ureter, cholangiocellular carcinoma, hepatocellular carcinoma, renal cell carcinoma, carcinoma of the renal pelvis, neoplasms of the central nervous system (CNS), primary CNS lymphoma, spinal axis tumors, brain stem glioma and pituitary adenoma

71. Use of a conjugate according to any one of clauses 1-65 in the preparation of a medicament for the treatment of cancer.

72. The use of clause 70, wherein the cancer is selected from the group consisting of lung cancer, small cell lung cancer (SCLC), non-small cell lung cancer (NSCLC), bronchopulmonary carcinoid, bone cancer, pancreatic cancer, pancreatic ductal adenocarcinomas, skin cancer, cancer of the head or neck, cutaneous or intraocular melanoma, uterine cancer, ovarian cancer, rectal cancer, cancer of the anal region, stomach cancer, colon cancer, colorectal cancer, colorectal ductal adenocarcinomas, breast cancer, uterine cancer, carcinoma of the fallopian tubes, carcinoma of the endometrium, carcinoma of the cervix, carcinoma of the vagina, carcinoma of the vulva, Hodgkin's Disease, cancer of the esophagus, cancer of the small intestine, cancer of the endocrine system, gastrointestinal cancer, insulinoma, ileal carcinoid, gastrointestinal stromal tumor (GIST), gastric ductal adenocarcinoma, cancer of the thyroid gland, cancer of the parathyroid gland, cancer of the adrenal gland, sarcoma of soft tissue, cancer of the urethra, cancer of the penis, prostate cancer, chronic or acute leukemia, lymphocytic lymphomas, cancer of the bladder, cancer of the kidney or ureter, cholangiocellular carcinoma, hepatocellular carcinoma, renal cell carcinoma, carcinoma of the renal pelvis, neoplasms of the central nervous system (CNS), primary CNS lymphoma, spinal axis tumors, brain stem glioma and pituitary adenoma

73. A conjugate according to any one of clauses 1-65 for use in the treatment of the treatment of cancer.

74. The conjugate of clause 72, wherein the cancer is selected from the group consisting of lung cancer, small cell lung cancer (SCLC), non-small cell lung cancer (NSCLC), bronchopulmonary carcinoid, bone cancer, pancreatic cancer, pancreatic ductal adenocarcinomas, skin cancer, cancer of the head or neck, cutaneous or intraocular melanoma, uterine cancer, ovarian cancer, rectal cancer, cancer of the anal region, stomach cancer, colon cancer, colorectal cancer, colorectal ductal adenocarcinomas, breast cancer, uterine cancer, carcinoma of the fallopian tubes, carcinoma of the endometrium, carcinoma of the cervix, carcinoma of the vagina, carcinoma of the vulva, Hodgkin's Disease, cancer of the esophagus, cancer of the small intestine, cancer of the endocrine system, gastrointestinal cancer, insulinoma, ileal carcinoid, gastrointestinal stromal tumor (GIST), gastric ductal adenocarcinoma, cancer of the thyroid gland, cancer of the parathyroid gland, cancer of the adrenal gland, sarcoma of soft tissue, cancer of the urethra, cancer of the penis, prostate cancer, chronic or acute leukemia, lymphocytic lymphomas, cancer of the bladder, cancer of the kidney or ureter, cholangiocellular carcinoma, hepatocellular carcinoma, renal cell carcinoma, carcinoma of the renal pelvis, neoplasms of the central nervous system (CNS), primary CNS lymphoma, spinal axis tumors, brain stem glioma and pituitary adenoma.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the biodistribution of conjugates ^99mTc-EC1981 and ^99mTc-EC1825 in mice inoculated with HEK-CCK2R tumor cells, and administered 0.05 μmol/kg of ^99mTc-EC1981 and ^99mTc-EC1825. (a) ^99mTc-EC1825; (b) ^99mTc-EC1981.

FIG. 2 shows that the conjugates described herein are more efficacious in vivo, as compared to control, in mice bearing subcutaneous HEK-CCK2R tumor cells at a dose of 2 μmol/kg, TIW×2 weeks. (▪) control; (▴) EC1873 {1,4,0}; (●) EC1868 {0,5,0}; (∘) EC1947 {0,1,4}. All treatment groups were n=5; and each treatment group indicates {PR, CR, cure}.

FIG. 3 shows that the conjugates described herein do not induce weight loss when administered in vivo to mice bearing subcutaneous HEK-CCK2R tumor cells tumors at a dose of 2 μmol/kg, TIW×2 weeks. (▪) control; (▴) EC1873; (●) EC1868; (∘) EC1947.

FIG. 4 shows that the conjugates described herein are more efficacious in vivo, as compared to control, in mice bearing subcutaneous HEK-CCK2R tumor cells at a dose of 2 μmol/kg, TIW×2 weeks. (▪) control; (▾) EC1812 {1,0,0}; (●) EC1868 {0,5,0}; (□) EC1977 {0,1,4}. All treatment groups were n=5; and each treatment group indicates {PR, CR, cure}.

FIG. 5 shows the effect of EC1812 (Z360-tubulysin)+/−Re-EC1786 on HEK-CCK2R. EC1812 is relatively inactive on HEK-CCK2R, and the activity is not competeable with excess Re-EC1786. (a) EC1812 (IC₅₀=225 nM), (b) EC1812+Re-EC1786 (IC₅₀=262 nM).

FIG. 6 shows the effect of EC1868+/−Re-EC1850 on HEK-CCK2R. EX1868 exhibits potent, competeable cytotoxic activity in HEK293-CCK2R expressing cells. (●) EC1812 (IC₅₀=5.8 nM), (▪) EC1812+Re-EC1825 (IC₅₀=364.7 nM).

FIG. 7 shows CCK2R radioligand binding in GIST.

FIG. 8 shows CCK2R radioligand binding in normal stomach tissue.

FIG. 9 shows CCK2R mRNA expression in frozen human tissues. Results show CCK2R expression in GIST and normal stomach human samples.

FIG. 10 shows CCK2R binding-mRNA correlation in GIST.

FIG. 11 shows confocal microscope images of HEK-CCK2R GFP-overexpressing cells stained with EC1906. FIG. 11A: CCK2R/EC1906; FIG. 11B: 100 nM EC1906; FIG. 11C: CCK2R/EC1906; FIG. 11D: 100 nM EC1906+10 μM EC1850.

DEFINITIONS

As used herein, the term “alkyl” includes a chain of carbon atoms, which is optionally branched and contains from 1 to 20 carbon atoms. It is to be further understood that in certain embodiments, alkyl may be advantageously of limited length, including C₁-C₁₂, C₁-C₁₀, C₁-C₉, C₁-C₈, C₁-C₇, C₁-C₆, and C₁-C₄, Illustratively, such particularly limited length alkyl groups, including C₁-C₈, C₁-C₇, C₁-C₆, and C₁-C₄, and the like may be referred to as “lower alkyl.” Illustrative alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, 2-pentyl, 3-pentyl, neopentyl, hexyl, heptyl, octyl, and the like. Alkyl may be substituted or unsubstituted. Typical substituent groups include cycloalkyl, aryl, heteroaryl, heteroalicyclic, hydroxy, alkoxy, aryloxy, mercapto, alkylthio, arylthio, cyano, halo, carbonyl, oxo, (═O), thiocarbonyl, O-carbamyl, N-carbamyl, O-thiocarbamyl, N-thiocarbamyl, C-amido, N-amido, C-carboxy, O-carboxy, nitro, and amino, or as described in the various embodiments provided herein. It will be understood that “alkyl” may be combined with other groups, such as those provided above, to form a functionalized alkyl. By way of example, the combination of an “alkyl” group, as described herein, with a “carboxy” group may be referred to as a “carboxyalkyl” group. Other non-limiting examples include hydroxyalkyl, aminoalkyl, and the like.

As used herein, the term “alkenyl” includes a chain of carbon atoms, which is optionally branched, and contains from 2 to 20 carbon atoms, and also includes at least one carbon-carbon double bond (i.e. C═C). It will be understood that in certain embodiments, alkenyl may be advantageously of limited length, including C₂-C₁₂, C₂-C₉, C₂-C₈, C₂-C₇, C₂-C₆, and C₂-C₄. Illustratively, such particularly limited length alkenyl groups, including C₂-C₈, C₂-C₇, C₂-C₆, and C₂-C₄may be referred to as lower alkenyl. Alkenyl may be unsubstituted, or substituted as described for alkyl or as described in the various embodiments provided herein. Illustrative alkenyl groups include, but are not limited to, ethenyl, 1-propenyl, 2-propenyl, 1-, 2-, or 3-butenyl, and the like.

As used herein, the term “alkynyl” includes a chain of carbon atoms, which is optionally branched, and contains from 2 to 20 carbon atoms, and also includes at least one carbon-carbon triple bond (i.e. C≡C). It will be understood that in certain embodiments alkynyl may each be advantageously of limited length, including C₂-C₁₂, C₂-C₉, C₂-C₈, C₂-C₇, C₂-C₆, and C₂-C₄. Illustratively, such particularly limited length alkynyl groups, including C₂-C₈, C₂-C₇, C₂-C₆, and C₂-C₄may be referred to as lower alkynyl. Alkenyl may be unsubstituted, or substituted as described for alkyl or as described in the various embodiments provided herein. Illustrative alkenyl groups include, but are not limited to, ethynyl, 1-propynyl, 2-propynyl, 1-, 2-, or 3-butynyl, and the like.

As used herein, the term “aryl” refers to an all-carbon monocyclic or fused-ring polycyclic groups of 6 to 12 carbon atoms having a completely conjugated pi-electron system. It will be understood that in certain embodiments, aryl may be advantageously of limited size such as C₆-C₁₀aryl. Illustrative aryl groups include, but are not limited to, phenyl, naphthalenyl and anthracenyl. The aryl group may be unsubstituted, or substituted as described for alkyl or as described in the various embodiments provided herein.

As used herein, the term “cycloalkyl” refers to a 3 to 15 member all-carbon monocyclic ring, an all-carbon 5-member/6-member or 6-member/6-member fused bicyclic ring, or a multicyclic fused ring (a “fused” ring system means that each ring in the system shares an adjacent pair of carbon atoms with each other ring in the system) group where one or more of the rings may contain one or more double bonds but the cycloalkyl does not contain a completely conjugated pi-electron system. It will be understood that in certain embodiments, cycloalkyl may be advantageously of limited size such as C₃-C₁₃, C₃-C₆, C₃-C₆and C₄-C₆. Cycloalkyl may be unsubstituted, or substituted as described for alkyl or as described in the various embodiments provided herein. Illustrative cycloalkyl groups include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclopentenyl, cyclopentadienyl, cyclohexyl, cyclohexenyl, cycloheptyl, adamantyl, norbornyl, norbornenyl, 9H-fluoren-9-yl, and the like.

As used herein, the term “heterocycloalkyl” refers to a monocyclic or fused ring group having in the ring(s) from 3 to 12 ring atoms, in which at least one ring atom is a heteroatom, such as nitrogen, oxygen or sulfur, the remaining ring atoms being carbon atoms. Heterocycloalkyl may optionally contain 1, 2, 3 or 4 heteroatoms. Heterocycloalkyl may also have one of more double bonds, including double bonds to nitrogen (e.g. C═N or N═N) but does not contain a completely conjugated pi-electron system. It will be understood that in certain embodiments, heterocycloalkyl may be advantageously of limited size such as 3- to 7-membered heterocycloalkyl, 5- to 7-membered heterocycloalkyl, and the like. Heterocycloalkyl may be unsubstituted, or substituted as described for alkyl or as described in the various embodiments provided herein. Illustrative heterocycloalkyl groups include, but are not limited to, oxiranyl, thianaryl, azetidinyl, oxetanyl, tetrahydrofuranyl, pyrrolidinyl, tetrahydropyranyl, piperidinyl, 1,4-dioxanyl, morpholinyl, 1,4-dithianyl, piperazinyl, oxepanyl, 3,4-dihydro-2H-pyranyl, 5,6-dihydro-2H-pyranyl, 2H-pyranyl, 1, 2, 3, 4-tetrahydropyridinyl, and the like.

As used herein, the term “heteroaryl” refers to a monocyclic or fused ring group of 5 to 12 ring atoms containing one, two, three or four ring heteroatoms selected from nitrogen, oxygen and sulfur, the remaining ring atoms being carbon atoms, and also having a completely conjugated pi-electron system. It will be understood that in certain embodiments, heteroaryl may be advantageously of limited size such as 3- to 7-membered heteroaryl, 5- to 7-membered heteroaryl, and the like. Heteroaryl may be unsubstituted, or substituted as described for alkyl or as described in the various embodiments provided herein. Illustrative heteroaryl groups include, but are not limited to, pyrrolyl, furanyl, thiophenyl, imidazolyl, oxazolyl, thiazolyl, pyrazolyl, pyridinyl, pyrimidinyl, quinolinyl, isoquinolinyl, purinyl, tetrazolyl, triazinyl, pyrazinyl, tetrazinyl, quinazolinyl, quinoxalinyl, thienyl, isoxazolyl, isothiazolyl, oxadiazolyl, thiadiazolyl, triazolyl, benzimidazolyl, benzoxazolyl, benzthiazolyl, benzisoxazolyl, benzisothiazolyl and carbazoloyl, and the like.

As used herein, “hydroxy” or “hydroxyl” refers to an —OH group.

As used herein, “alkoxy” refers to both an —O-(alkyl) or an —O-(unsubstituted cycloalkyl) group. Representative examples include, but are not limited to, methoxy, ethoxy, propoxy, butoxy, cyclopropyloxy, cyclobutyloxy, cyclopentyloxy, cyclohexyloxy, and the like.

As used herein, “aryloxy” refers to an —O-aryl or an —O-heteroaryl group. Representative examples include, but are not limited to, phenoxy, pyridinyloxy, furanyloxy, thienyloxy, pyrimidinyloxy, pyrazinyloxy, and the like, and the like.

As used herein, “mercapto” refers to an —SH group.

As used herein, “alkylthio” refers to an —S-(alkyl) or an —S-(unsubstituted cycloalkyl) group. Representative examples include, but are not limited to, methylthio, ethylthio, propylthio, butylthio, cyclopropylthio, cyclobutylthio, cyclopentylthio, cyclohexylthio, and the like.

As used herein, “arylthio” refers to an —S-aryl or an —S-heteroaryl group. Representative examples include, but are not limited to, phenylthio, pyridinylthio, furanylthio, thienylthio, pyrimidinylthio, and the like.

As used herein, “halo” or “halogen” refers to fluorine, chlorine, bromine or iodine.

As used herein, “trihalomethyl” refers to a methyl group having three halo substituents, such as a trifluoromethyl group.

As used herein, “cyano” refers to a —CN group.

As used herein, “sulfinyl” refers to a —S(O)R^agroup, where R^ais any variable group as described in the various embodiments provided herein, or R^amay be a hydroxyl group.

As used herein, “sulfonyl” refers to a —S(O)₂R^agroup, where R^ais any variable group as described in the various embodiments provided herein, or R^amay be a hydroxyl group.

As used herein, “S-sulfonamido” refers to a —S(O)₂NR^aR^bgroup, where R^aand R^bare any variable group as described in the various embodiments provided herein.

As used herein, “N-sulfonamido” refers to a —NR^aS(O)₂R^bgroup, where R^aand R^bare any variable group as described in the various embodiments provided herein.

As used herein, “O-carbamyl” refers to a —OC(O)NR^aR^bgroup, where R^aand R^bare any variable group as described in the various embodiments provided herein.

As used herein, “N-carbamyl” refers to an R^aOC(O)NR^b— group, where R^aand R^bare any variable group as described in the various embodiments provided herein.

As used herein, “O-thiocarbamyl” refers to a —OC(S)NR^aR^bgroup, where R^aand R^bare any variable group as described in the various embodiments provided herein.

As used herein, “N-thiocarbamyl” refers to a R^aOC(S)NR^b— group, where R^aand R^bare any variable group as described in the various embodiments provided herein.

As used herein, “amino” refers to an —NR^aR^bgroup, where R^aand R^bare any variable group as described in the various embodiments provided herein.

As used herein, “C-amido” refers to a —C(O)NR^aR^bgroup, where R^aand R^bare any variable group as described in the various embodiments provided herein.

As used herein, “N-amido” refers to a R^aC(O)NR^b— group, where R^aand R^bare any variable group as described in the various embodiments provided herein.

As used herein, “nitro” refers to a —NO₂group.

As used herein, “bond” refers to a covalent bond.

As used herein, “optional” or “optionally” means that the subsequently described event or circumstance may but need not occur, and that the description includes instances where the event or circumstance occurs and instances in which it does not. For example, “heterocycle group optionally substituted with an alkyl group” means that the alkyl may but need not be present, and the description includes situations where the heterocycle group is substituted with an alkyl group and situations where the heterocycle group is not substituted with the alkyl group.

As used herein, “independently” means that the subsequently described event or circumstance is to be read on its own relative to other similar events or circumstances. For example, in a circumstance where several equivalent hydrogen groups are optionally substituted by another group described in the circumstance, the use of “independently optionally” means that each instance of a hydrogen atom on the group may be substituted by another group, where the groups replacing each of the hydrogen atoms may be the same or different. Or for example, where multiple groups exist all of which can be selected from a set of possibilities, the use of “independently” means that each of the groups can be selected from the set of possibilities separate from any other group, and the groups selected in the circumstance may be the same or different.

As used herein, the term “pharmaceutically acceptable salt” refers to those salts which counter ions which may be used in pharmaceuticals. Such salts include:

(1) acid addition salts, which can be obtained by reaction of the free base of the parent conjugate with inorganic acids such as hydrochloric acid, hydrobromic acid, nitric acid, phosphoric acid, sulfuric acid, and perchloric acid and the like, or with organic acids such as acetic acid, oxalic acid, (D) or (L) malic acid, maleic acid, methane sulfonic acid, ethanesulfonic acid, p-toluenesulfonic acid, salicylic acid, tartaric acid, citric acid, succinic acid or malonic acid and the like; or

(2) salts formed when an acidic proton present in the parent conjugate either is replaced by a metal ion, e.g., an alkali metal ion, an alkaline earth ion, or an aluminum ion; or coordinates with an organic base such as ethanolamine, diethanolamine, triethanolamine, trimethamine, N-methylglucamine, and the like.

Pharmaceutically acceptable salts are well known to those skilled in the art, and any such pharmaceutically acceptable salt may be contemplated in connection with the embodiments described herein

As used herein, “amino acid” (a.k.a. “AA”) means any molecule that includes an alpha-carbon atom covalently bonded to an amino group and an acid group. The acid group may include a carboxyl group. “Amino acid” may include molecules having one of the formulas:

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wherein R^sis a side group and Φ includes at least 3 carbon atoms. “Amino acid” includes stereoisomers such as the D-amino acid and L-amino acid forms. Illustrative amino acid groups include, but are not limited to, the twenty endogenous human amino acids and their derivatives, such as lysine (Lys), asparagine (Asn), threonine (Thr), serine (Ser), isoleucine (Ile), methionine (Met), proline (Pro), histidine (His), glutamine (Gln), arginine (Arg), glycine (Gly), aspartic acid (Asp), glutamic acid (Glu), alanine (Ala), valine (Val), phenylalanine (Phe), leucine (Leu), tyrosine (Tyr), cysteine (Cys), tryptophan (Trp), phosphoserine (PSER), sulfo-cysteine, arginosuccinic acid (ASA), hydroxyproline, phosphoethanolamine (PEA), sarcosine (SARC), taurine (TAU), carnosine (CARN), citrulline (CIT), anserine (ANS), 1,3-methyl-histidine (ME-HIS), alpha-amino-adipic acid (AAA), beta-alanine (BALA), ethanolamine (ETN), gamma-amino-butyric acid (GABA), beta-amino-isobutyric acid (BAIA), alpha-amino-butyric acid (BABA), L-allo-cystathionine (cystathionine-A; CYSTA-A), L-cystathionine (cystathionine-B; CYSTA-B), cystine, allo-isoleucine (ALLO-ILE), DL-hydroxylysine (hydroxylysine (I)), DL-allo-hydroxylysine (hydroxylysine (2)), ornithine (ORN), homocystine (HCY), 3-amino-L-alanine (L-2,3-diaminopropionic acid or Dap) and derivatives thereof. It will be appreciated that each of these examples are also contemplated in connection with the present disclosure in the D-configuration as noted above. Specifically, for example, D-lysine (D-Lys), D-asparagine (D-Asn), D-threonine (D-Thr), D-serine (D-Ser), D-isoleucine (D-Ile), D-methionine (D-Met), D-proline (D-Pro), D-histidine (D-His), D-glutamine (D-Gln), D-arginine (D-Arg), D-glycine (D-Gly), D-aspartic acid (D-Asp), D-glutamic acid (D-Glu), D-alanine (D-Ala), D-valine (D-Val), D-phenylalanine (D-Phe), D-leucine (D-Leu), D-tyrosine (D-Tyr), D-cysteine (D-Cys), D-tryptophan (D-Trp), D-citrulline (D-CIT), D-carnosine (D-CARN), and the like. In connection with the embodiments described herein, amino acids can be covalently attached to other portions of the conjugates described herein through their alpha-amino and carboxy functional groups (i.e. in a peptide bond configuration), or through their side chain functional groups (such as the side chain carboxy group in glutamic acid) and either their alpha-amino or carboxy functional groups. It will be understood that amino acids, when used in connection with the conjugates described herein, may exist as zwitterions in a conjugate in which they are incorporated.

As used herein, “prodrug” refers to a compound that can be administered to a subject in a pharmacologically inactive form which then can be converted to a pharmacologically active form through a normal metabolic process, such as hydrolysis of an oxazolidine. It will be understood that the metabolic processes through which a prodrug can be converted to an active drug include, but are not limited to, one or more spontaneous chemical reaction(s), enzyme-catalyzed chemical reaction(s), and/or other metabolic chemical reaction(s), or a combination thereof. It will be appreciated that understood that a variety of metabolic processes are known in the art, and the metabolic processes through which the prodrugs described herein are converted to active drugs are non-limiting. A prodrug can be a precursor chemical compound of a drug that has a therapeutic effect on a subject.

As used herein, the term “therapeutically effective amount” refers to an amount of a drug or pharmaceutical agent that elicits the biological or medicinal response in a subject (i.e. a tissue system, animal or human) that is being sought by a researcher, veterinarian, medical doctor or other clinician, which includes, but is not limited to, alleviation of the symptoms of the disease or disorder being treated. In one aspect, the therapeutically effective amount is that amount of an active which may treat or alleviate the disease or symptoms of the disease at a reasonable benefit/risk ratio applicable to any medical treatment. In another aspect, the therapeutically effective amount is that amount of an inactive prodrug which when converted through normal metabolic processes to produce an amount of active drug capable of eliciting the biological or medicinal response in a subject that is being sought.

It is also appreciated that the dose, whether referring to monotherapy or combination therapy, is advantageously selected with reference to any toxicity, or other undesirable side effect, that might occur during administration of one or more of the conjugates described herein. Further, it is appreciated that the co-therapies described herein may allow for the administration of lower doses of conjugates that show such toxicity, or other undesirable side effect, where those lower doses are below thresholds of toxicity or lower in the therapeutic window than would otherwise be administered in the absence of a cotherapy.

As used herein, “administering” includes all means of introducing the conjugates and compositions described herein to the host animal, including, but are not limited to, oral (po), intravenous (iv), intramuscular (im), subcutaneous (sc), transdermal, inhalation, buccal, ocular, sublingual, vaginal, rectal, and the like. The conjugates and compositions described herein may be administered in unit dosage forms and/or formulations containing conventional nontoxic pharmaceutically-acceptable carriers, adjuvants, and/or vehicles.

As used herein, “pharmaceutical composition” or “composition” refers to a mixture of one or more of the conjugates described herein, or pharmaceutically acceptable salts, solvates, hydrates thereof, with other chemical components, such as pharmaceutically acceptable excipients. The purpose of a pharmaceutical composition is to facilitate administration of a conjugate to a subject. Pharmaceutical compositions suitable for the delivery of conjugates described and methods for their preparation will be readily apparent to those skilled in the art. Such compositions and methods for their preparation may be found, for example, in ‘Remington's Pharmaceutical Sciences’, 19th Edition (Mack Publishing Company, 1995).

A “pharmaceutically acceptable excipient” refers to an inert substance added to a pharmaceutical composition to further facilitate administration of a conjugate such as a diluent or a carrier.

As used herein, “counter-ion” refers to any ion that accompanies an ionic species in order to maintain electric neutrality that is known in the art. Suitable counter-ions can be metal ions such as Na⁺, Mg⁺⁺, K⁺ and the like, or organic ions (e.g. lipophilic cations), such as quaterary ammonium cations, such as tetramethylammonium, tetraethylammonium, tetrabuylammonium, and the like. It will be appreciated that the exact nature or identity of a counter-ion suitable for use in connection with the present disclosure is not particularly limited.

DETAILED DESCRIPTION

In each of the foregoing and each of the following embodiments, it is to be understood that the formulae include and represent not only all pharmaceutically acceptable salts of the conjugates, but also include any and all hydrates and/or solvates of the conjugate formulae. It is appreciated that certain functional groups, such as the hydroxy, amino, and like groups form complexes and/or coordination conjugates with water and/or various solvents, in the various physical forms of the conjugates. Accordingly, the above formulae are to be understood to include and represent those various hydrates and/or solvates. It is also to be understood that the non-hydrates and/or non-solvates of the conjugate formulae are described by such formula, as well as the hydrates and/or solvates of the conjugate formulae.

As used herein, the term cell surface receptor binding ligand (aka a “binding ligand”), generally refers to compounds that bind to and/or target receptors that are found on cell surfaces, and in particular those that are found on, over-expressed by, and/or preferentially expressed on the surface of pathogenic cells. Binding ligands include, but are not limited to, those that target CCK2R. Examples of CCK2R binding ligands include non-peptidic agonists and antagonists of CCK2R that have been described in the literature (See for example, Wayua, C. et al., J. Nucl. Med., 56, 1, 113-9 (2015)), and peptidic agonists and antagonists of CCK2R.

In the case of non-peptidic CCK2R binding ligands, the binding ligand can be of the type described in United Stated Patent Publication US2012/0010401A1. Such non-peptidic binding ligands include those described by the formula

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wherein

Y is a bond or a C₁-C₆alkyl;

each of R⁴⁶, R⁴⁷, R⁴⁸and R⁴⁹is independently selected from the group consisting of H, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl and C₃-C₆cycloalkyl, wherein each hydrogen atom in C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl and C₃-C₆cycloalkyl is independently optionally substituted by halogen, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl, —OR⁵⁰, —OC(O)R⁵⁰, —OC(O)NR⁵⁰R^50′, —OS(O)R⁵⁰, —OS(O)₂R⁵⁰, —SR^50′, —S(O)R⁵⁰, —S(O)₂R⁵⁰, —S(O)NR⁵⁰R^50′, —S(O)₂NR⁵⁰R^50′, —OS(O)NR⁵⁰R^50′, —OS(O)₂NR⁵⁰R^50′, —NR⁵⁰R^50′, —NR⁵⁰C(O)R⁵¹, —NR⁵⁰C(O)OR⁵¹, —NR⁵⁰C(O)NR⁵¹R^51′, —NR⁵⁰S(O)R⁵¹, —NR⁵⁰S(O)₂R⁵¹, —NR⁵⁰S(O)NR⁵¹R^51′, —NR⁵⁰S(O)₂NR⁵¹R^51′, —C(O)R⁵⁰, —C(O)OR⁵⁰or —C(O)NR⁵⁰R⁵⁰; and

each R⁵⁰, R^50′, R⁵¹and R^51′is independently H, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl or C₃-C₆cycloalkyl.

In some embodiments, the CCK2R binding ligand is a compound of the formula

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In some embodiments, R⁴⁶is —CH₂C(O)C(CH₃)₃. In some embodiments, R⁴⁷is cyclohexyl. In some embodiments, R⁴⁸and R⁴⁹are H. In some embodiments, Y is a bond. In some embodiments, R⁴⁶is —CH₂C(O)C(CH₃)₃, R⁴⁷is cyclohexyl, R⁴⁸and R⁴⁹are H; and Y is a bond.

In the case of peptidic CCK2R binding ligands, the sequence of the binding ligand can be any sequence capable of recognizing and sequestering the CCK2R receptor. Such peptidic binding ligands include those having unnatural amino acids in the sequence. For example, peptidic binding ligands can include one or more amino acids having a D-configuration. In addition, such peptidic binding ligands can include one or more amino acids having an unnatural or derivitized side chain group, such as a sulfated side chain.

In some embodiments, peptidic binding ligands useful in connection with the present disclosure can be peptides of from 6 to 10 amino acids in length capable of binding to CCK2R. In some embodiments, peptidic binding ligands useful in connection with the present disclosure can be peptides of from 6 to 10 amino acids in length where the amino acids are each independently selected from the group consisting of methionine (Met), glycine (Gly), aspartic acid (Asp), phenylalanine (Phe), tyrosine (Tyr) and tryptophan (Trp). In some embodiments, peptidic binding ligands useful in connection with the present disclosure include an amino acid sequence of Met-Gly-Trp-Met-Asp-Phe. In some embodiments, peptidic binding ligands useful in connection with the present disclosure include an amino acid sequence of Tyr-Met-Gly-Trp-Met-Asp-Phe. In some embodiments, peptidic binding ligands useful in connection with the present disclosure include an amino acid sequence of Tyr-Met-Gly-Trp-Met-Asp-Phe, wherein one or more of the amino acids in the sequence are an unnatural amino acid. In some embodiments, peptidic binding ligands useful in connection with the present disclosure include an amino acid sequence of Tyr-Met-Gly-Trp-Met-Asp-Phe, wherein one or more of the amino acids in the sequence have an unnatural or derivitized side chain group, such as a sulfated side chain. In some embodiments, peptidic binding ligands useful in connection with the present disclosure include an amino acid sequence of Asp-Tyr-Met-Gly-Trp-Met-Asp-Phe. In some embodiments, peptidic binding ligands useful in connection with the present disclosure include an amino acid sequence of Asp-Tyr-Met-Gly-Trp-Met-Asp-Phe, wherein one or more of the amino acids in the sequence are an unnatural amino acid. In some embodiments, peptidic binding ligands useful in connection with the present disclosure include an amino acid sequence of Asp-Tyr-Met-Gly-Trp-Met-Asp-Phe, wherein one or more of the amino acids in the sequence have an unnatural or derivitized side chain group, such as a sulfated side chain.

In some embodiments, the binding ligand can be of the formula

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wherein R is H, —SO₃⁻ or —SO₃M, wherein M is a counter-ion, and wherein * is a covalent bond attaching the binding ligand to a linker as described herein.

In some embodiments, L is a releasable linker. In some embodiments L comprises one or more of the moieties L¹, L²and L³, as defined herein. In some embodiments, L further comprises at least one amino acid (AA) as defined herein. As used herein, the term “releasable linker” refers to a linker that includes at least one bond that can be broken under physiological conditions, such as a pH-labile, acid-labile, base-labile, oxidatively labile, metabolically labile, biochemically labile, or enzyme-labile bond (a “releasable moiety” or “cleavable bond”). It is appreciated that such physiological conditions resulting in bond breaking do not necessarily include a biological or metabolic process, and instead may include a standard chemical reaction, such as a hydrolysis reaction, for example, at physiological pH, or as a result of compartmentalization into a cellular organelle such as an endosome having a lower pH than cytosolic pH.

It is understood that a cleavable bond can connect two adjacent atoms within the releasable linker and/or connect other linkers, B or D, as described herein, at either or both ends of the releasable linker. In the case where a cleavable bond connects two adjacent atoms within the releasable linker, following breakage of the bond, the releasable linker is broken into two or more fragments. Alternatively, in the case where a cleavable bond is between the releasable linker and another moiety, such as another linker, a drug or binding ligand, the releasable linker becomes separated from the other moiety following breaking of the bond.

The lability of the cleavable bond can be adjusted by, for example, substituents at or near the cleavable bond, such as including alpha-branching adjacent to a cleavable disulfide bond.

In some embodiments, releasable linkers described herein include one or more cleavable functional groups, such as a disulfide, a carbonate, a carbamate, a hydrazine, an amide, an ester, and the like. Illustrative cleavable functional group included in the releasable linkers described herein include hemiacetals and sulfur variations thereof, acetals and sulfur variations thereof, hemiaminals, aminals, and the like, and can be formed from methylene fragments substituted with at least one heteroatom, 1-alkoxy alkylene, 1-alkoxycycloalkylene, 1-alkoxyalkylenecarbonyl, 1-alkoxycycloalkylene-carbonyl, and the like. Illustrative releasable linkers described herein include linkers that include carbonylarylcarbonyl, carbonyl(carboxyaryl)carbonyl, carbonyl(biscarboxyaryl)carbonyl, haloalkylenecarbonyl, and the like. Illustrative releasable linkers described herein include linkers that include alkylene(dialkylsilyl), alkylene(alkylarylsilyl), alkylene(diarylsilyl), (dialkylsilyl)aryl, (alkylarylsilyl)aryl, (diarylsilyl)aryl, and the like. Illustrative releasable linkers described herein include oxycarbonyloxy, oxycarbonyloxyalkyl, sulfonyloxy, oxysulfonylalkyl, and the like. Illustrative releasable linkers described herein include functional groups that include iminoalkylidenyl, carbonylalkylideniminyl, iminocycloalkylidenyl, carbonylcycloalkyliden-iminyl, and the like. Illustrative releasable linkers described herein include functional groups that include alkylenethio, alkylenearylthio, and carbonylalkylthio, and the like.

In some embodiments, the conjugates described herein comprise more than one cleavable functional group. It will be appreciated that when the conjugates described herein comprise more than one cleavable functional group, the cleavable functional groups may be the same. It will be further appreciated that when the conjugates described herein comprise more than one cleavable functional group, the cleavable functional groups may be different. In some embodiments, the conjugates described herein comprise more than one cleavable functional group, wherein at least one cleavable functional group comprises is a disulfide bond.

In some embodiments, L comprises a moiety L¹of the formula selected from the group consisting of

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wherein

each X⁶is independently C₁-C₆alkyl or C₆-C₁₀aryl(C₁-C₆alkyl), wherein each hydrogen atom in C₁-C₆alkyl and C₆-C₁₀aryl(C₁-C₆alkyl) is independently optionally substituted by halogen, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl, —OR³⁴, —OC(O)R³⁴, —OC(O)NR³⁴R^34′, —OS(O)R³⁴, —OS(O)₂R³⁴, —SR³⁴, —S(O)R³⁴, —S(O)₂R³⁴, —S(O)NR³⁴R^34′, —S(O)₂NR³⁴R^34′, —OS(O)NR³⁴R^34′, —OS(O)₂NR³⁴R^34′, —NR³⁴R^34′, —NR³⁴C(O)R³⁵, —NR³⁴C(O)OR³⁵, —NR³⁴C(O)NR³⁵R^35′, —NR³⁴S(O)R³⁵, —NR³⁴S(O)₂R³⁵, —NR³⁴S(O)NR³⁵R^35′, —NR³⁴S(O)₂NR³⁵R^35′, —C(O)R³⁴, —C(O)OR³⁴or —C(O)NR³⁴R^34′;

each R³⁹, R^39′, R⁴⁰and R^40′is independently selected from the group consisting of H, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl and C₃-C₆cycloalkyl, wherein each hydrogen atom in C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl and C₃-C₆cycloalkyl is independently optionally substituted by halogen, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl, —OR⁴⁴, —OC(O)R⁴⁴, —OC(O)NR⁴⁴R^44′, —OS(O)R⁴⁴, —OS(O)₂R⁴⁴, —SR⁴⁴, —S(O)R⁴⁴, —S(O)₂R⁴⁴, —S(O)NR⁴⁴R^44′, —S(O)₂NR⁴⁴R^44′, —OS(O)NR⁴⁴R^44′, —OS(O)₂NR⁴⁴R^44′, —NR⁴⁴R^44′, —NR⁴⁴C(O)R⁴⁵, NR⁴⁴C(O)OR⁴⁵, —NR⁴⁴C(O)NR⁴⁵R^45′, —NR⁴⁴S(O)R⁴⁵, —NR⁴⁴S(O)₂R⁴⁵, —NR⁴⁴S(O)NR⁴⁵R^45′, —NR⁴⁴S(O)₂NR⁴⁵R^45′, —C(O)R⁴⁴, —C(O)OR⁴⁴or —C(O)NR⁴⁴R^44′;

each R⁴¹is independently selected from the group consisting of H, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl and C₃-C₆cycloalkyl, wherein each hydrogen atom in C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl and C₃-C₆cycloalkyl is independently optionally substituted by halogen, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl, —OR⁴², OC(O)R⁴², —OC(O)NR⁴²R^42′, —OS(O)R⁴², —OS(O)₂R⁴², —SR⁴², —S(O)R⁴², —S(O)₂R⁴², —S(O)NR⁴²R^42′, —S(O)₂NR⁴²R^42′, —OS(O)NR⁴²R^42′, —OS(O)₂NR⁴²R^42′, —NR⁴²R^42′, —NR⁴²C(O)R⁴³, —NR⁴²C(O)OR⁴³, —NR⁴²C(O)NR⁴³R^43′, —NR⁴²S(O)R⁴³, —NR⁴²S(O)₂R⁴³, —NR⁴²S(O)NR⁴³R^43′, —NR⁴²S(O)₂NR⁴³R^43′, —C(O)R⁴², —C(O)OR⁴²or —C(O)NR⁴²R^42′;

u is 1, 2, 3 or 4;

wherein * is a covalent bond.

In some embodiments, L comprises a moiety L¹of the formula selected from the group consisting of

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wherein

each X⁶is independently C₁-C₆alkyl or C₆-C₁₀aryl(C₁-C₆alkyl), wherein each hydrogen atom in C₁-C₆alkyl and C₆-C₁₀aryl(C₁-C₆alkyl) is independently optionally substituted by halogen, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl, —OR³⁴, —OC(O)R³⁴, —OC(O)NR³⁴R^34′, —OS(O)R³⁴, —OS(O)₂R³⁴, —SR³⁴, —S(O)R³⁴, —S(O)₂R³⁴, —S(O)NR³⁴R^34′, —S(O)₂NR³⁴R^34′, —OS(O)NR³⁴R^34′, —OS(O)₂NR³⁴R^34′, —NR³⁴R^34′, —NR³⁴C(O)R³⁵, NR³⁴C(O)OR³⁵, —NR³⁴C(O)NR³⁵R^35′, —NR³⁴S(O)R³⁵, —NR³⁴S(O)₂R³⁵, —NR³⁴S(O)NR³⁵R^35′, —NR³⁴S(O)₂NR³⁵R^35′, —C(O)R³⁴, —C(O)OR³⁴or —C(O)NR³⁴R^34′;

each R³⁹, R^39′, R⁴⁰and R^40′is independently selected from the group consisting of H, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl and C₃-C₆cycloalkyl, wherein each hydrogen atom in C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl and C₃-C₆cycloalkyl is independently optionally substituted by halogen, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl, —OR⁴⁴, —OC(O)R⁴⁴, —OC(O)NR⁴⁴R^44′, —OS(O)R⁴⁴, —OS(O)₂R⁴⁴, —SR⁴⁴, —S(O)R⁴⁴, —S(O)₂R⁴⁴, —S(O)NR⁴⁴R^44′, —S(O)₂NR⁴⁴R^44′, —OS(O)NR⁴⁴R^44′, —OS(O)₂NR⁴⁴R^44′, —NR⁴⁴R^44′, —NR⁴⁴C(O)R⁴⁵, NR⁴⁴C(O)OR⁴⁵, —NR⁴⁴C(O)NR⁴⁵R^45′, —NR⁴⁴S(O)R⁴⁵, —NR⁴⁴S(O)₂R⁴⁵, —NR⁴⁴S(O)NR⁴⁵R^45′, —NR⁴⁴S(O)₂NR⁴⁵R^45′, —C(O)R⁴⁴, —C(O)OR⁴⁴or —C(O)NR⁴⁴R⁴⁴;

each R⁴¹is independently selected from the group consisting of H, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl and C₃-C₆cycloalkyl, wherein each hydrogen atom in C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl and C₃-C₆cycloalkyl is independently optionally substituted by halogen, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl, —OR⁴², OC(O)R⁴², —OC(O)NR⁴²R^42′, —OS(O)R⁴², —OS(O)₂R⁴², —SR⁴², —S(O)R⁴², —S(O)₂R⁴², —S(O)NR⁴²R^42′, —S(O)₂NR⁴²R^42′, —OS(O)NR⁴²R^42′, —OS(O)₂NR⁴²R^42′, —NR⁴²R^42′, —NR⁴²C(O)R⁴³, —NR⁴²C(O)OR⁴³, —NR⁴²C(O)NR⁴³R^43′, —NR⁴²S(O)R⁴³, —NR⁴²S(O)₂R⁴³, —NR⁴²S(O)NR⁴³R^43′, —NR⁴²S(O)₂NR⁴³R^43′, —C(O)R⁴², —C(O)OR⁴²or —C(O)NR⁴²R^42′;

u is 1, 2, 3 or 4;

wherein * is a covalent bond.

In some embodiments, L comprises a moiety of the formula selected from the group consisting of

embedded image

wherein

each R^31′ and R^31″is independently selected from the group consisting of H, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl and C₃-C₆cycloalkyl, wherein each hydrogen atom in C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl and C₃-C₆cycloalkyl is independently optionally substituted by halogen, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl, —OR³², OC(O)R³², —OC(O)NR³²R^32′, —OS(O)R³², —OS(O)₂R³², —SR³², —S(O)R³², —S(O)₂R³², —S(O)NR³²R^32′, —S(O)₂NR³²R^32′, —OS(O)NR³²R^32′, —OS(O)₂NR³²R^32′, —NR³²R^32′, —NR³²C(O)R³³, —NR³²C(O)OR³³, —NR³²C(O)NR³³R^33′, —NR³²S(O)R³³, —NR³²S(O)₂R³³, —NR³²S(O)NR³³R^33′, —NR³²S(O)₂NR³³R^33′, —C(O)R³², —C(O)OR³²or —C(O)NR³²R^32′;

each X⁶is independently C₁-C₆alkyl or C₆-C₁₀aryl(C₁-C₆alkyl), wherein each hydrogen atom in C₁-C₆alkyl and C₆-C₁₀aryl(C₁-C₆alkyl) is independently optionally substituted by halogen, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl, —OR³⁴, —OC(O)R³⁴, —OC(O)NR³⁴R^34′, —OS(O)R³⁴, —OS(O)₂R³⁴, —SR³⁴, —S(O)R³⁴, —S(O)₂R³⁴, —S(O)NR³⁴R^34′, —S(O)₂NR³⁴R^34′, —OS(O)NR³⁴R^34′, —OS(O)₂NR³⁴R^34′, —NR³⁴R^34′, —NR³⁴C(O)R³⁵, NR³⁴C(O)OR³⁵, —NR³⁴C(O)NR³⁵R^35′, —NR³⁴S(O)R³⁵, —NR³⁴S(O)₂R³⁵, —NR³⁴S(O)NR³⁵R^35′, —NR³⁴S(O)₂NR³⁵R^35′, —C(O)R³⁴, —C(O)OR³⁴or —C(O)NR³⁴R^34′;

each R³⁹and R^39′is independently selected from the group consisting of H, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl and C₃-C₆cycloalkyl, wherein each hydrogen atom in C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl and C₃-C₆cycloalkyl is independently optionally substituted by halogen, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl, —OR⁴⁴, OC(O)R⁴⁴, —OC(O)NR⁴⁴R^44′, —OS(O)R⁴⁴, —OS(O)₂R⁴⁴, —SR⁴⁴, —S(O)R⁴⁴, —S(O)₂R⁴⁴, —S(O)NR⁴⁴R^44′, —S(O)₂NR⁴⁴R^44′, —OS(O)NR⁴⁴R^44′, —OS(O)₂NR⁴⁴R^44′, —NR⁴⁴R^44′, —NR⁴⁴C(O)R⁴⁵, —NR⁴⁴C(O)OR⁴⁵, —NR⁴⁴C(O)NR⁴⁵R^45′, —NR⁴⁴S(O)R⁴⁵, —NR⁴⁴S(O)₂R⁴⁵, —NR⁴⁴S(O)NR⁴⁵R^45′, —NR⁴⁴S(O)₂NR⁴⁵R^45′, —C(O)R⁴⁴, —C(O)OR⁴⁴or —C(O)NR⁴⁴R^44′;

each R⁴⁴, R^44′, R⁴⁵, and R^45′is independently selected from the group consisting of H, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl and 5- to 7-membered heteroaryl; and

u is 1, 2, 3 or 4;

wherein * is a covalent bond.

In some embodiments, L comprises one or more additional linker moieties L²of the formula

embedded image

wherein

each R²¹and R^21′is independently selected from the group consisting of H, halogen, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl, —OR²⁴, OC(O)R²⁴, —OC(O)NR²⁴R^24′, —OS(O)R²⁴, —OS(O)₂R²⁴, —SR²⁴, —S(O)R²⁴, —S(O)₂R²⁴, —S(O)NR²⁴R^24′, —S(O)₂NR²⁴R^24′, —OS(O)NR²⁴R^24′, —OS(O)₂NR²⁴R^24′, —NR²⁴R^24′, —NR²⁴C(O)R²⁵, —NR²⁴C(O)OR²⁵, —NR²⁴C(O)NR²⁵R^25′, —NR²⁴S(O)R²⁵, —NR²⁴S(O)₂R²⁵, —NR²S(O)NR²⁵R^25′, —NR²⁴S(O)₂NR²⁵R^25′, —C(O)R²⁴, —C(O)OR²⁴and —C(O)NR²⁴R^24′, wherein each hydrogen atom in C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl and 5- to 7-membered heteroaryl is independently optionally substituted by halogen, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, —OR²⁴, —OC(O)R²⁴, —OC(O)NR²⁴R^24′, —OS(O)R²⁴, —OS(O)₂R²⁴, —SR²⁴, —S(O)R²⁴, —S(O)₂R²⁴, —S(O)NR²⁴R^24′, —S(O)₂NR²⁴R^24′, —OS(O)NR²⁴R^24′, —OS(O)₂NR²⁴R^24′, —NR²⁴R^24′, —NR²⁴C(O)R²⁵, —NR²⁴C(O)OR²⁵, —NR²⁴C(O)NR²⁵R^25′, —NR²⁴S(O)R²⁵, —NR²⁴S(O)₂R²⁵, —NR²⁴S(O)NR²⁵R^25′, —NR²⁴S(O)₂NR²⁵R^25′, C(O)R²⁴, —C(O)OR²⁴, or —C(O)NR²⁴R^24′; or R²¹and R^21′may combine to form a C₄-C₆cycloalkyl or a 4- to 6-membered heterocycle, wherein each hydrogen atom in C₄-C₆cycloalkyl or 4- to 6-membered heterocycle is independently optionally substituted by halogen, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl, —OR²⁴, —OC(O)R²⁴, —OC(O)NR²⁴R^24′, —OS(O)R²⁴, —OS(O)₂R²⁴, —SR²⁴, —S(O)R²⁴, —S(O)₂R²⁴, —S(O)NR²⁴R^24′, —S(O)₂NR²⁴R^24′, —OS(O)NR²⁴R^24′, —OS(O)₂NR²⁴R^24′, —NR²⁴R^24′, —NR²⁴C(O)R²⁵, —NR²⁴C(O)OR²⁵, NR²⁴C(O)NR²⁵R^25′, —NR²⁴S(O)R²⁵, —NR²⁴S(O)₂R²⁵, —NR²⁴S(O)NR²⁵R^25′, —NR²⁴S(O)₂NR²⁵R^25′, —C(O)R²⁴, —C(O)OR²⁴or —C(O)NR²⁴R^24′;

R²²is selected from the group consisting of H, D, C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl, —OR²⁶, —OC(O)R²⁶, —OC(O)NR²⁶R^26′, —OS(O)R²⁶, —OS(O)₂R²⁶, —SR²⁶, —S(O)R²⁶, —S(O)₂R²⁶, —S(O)NR²⁶R^26′, —S(O)₂NR²⁶R^26′, —OS(O)NR²⁶R^26′, —OS(O)₂NR²⁶R^26′, —NR²⁶R^26′, —NR²⁶C(O)R²⁷, —NR²⁶C(O)OR²⁷, —NR²⁶C(O)NR²⁷R^27′, NR²⁶C(═NR^26″)NR²⁷R^27′, —NR²⁶S(O)R²⁷, —NR²⁶S(O)₂R²⁷, —NR²⁶S(O)NR²⁷R^27′, —NR²⁶S(O)₂NR²⁷R^27′, —C(O)R²⁶, —C(O)OR²⁶and —C(O)NR²⁶R^26′, wherein each hydrogen atom in C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl and 5- to 7-membered heteroaryl is independently optionally substituted by halogen, C₁-C₆alkyl, C₂-C₆alkenyl, —(CH₂)_pOR²⁸, —(CH₂)_p(OCH₂)_qOR²⁸, —(CH₂)_p(OCH₂CH₂)_qOR²⁸, —OR²⁹, —OC(O)R²⁹, —OC(O)NR²⁹R^29′, —OS(O)R²⁹, —OS(O)₂R²⁹, —(CH₂)_pOS(O)₂OR²⁹, —OS(O)₂OR²⁹, —SR²⁹, —S(O)R²⁹, —S(O)₂R²⁹, —S(O)NR²⁹R^29′, —S(O)₂NR²⁹R^29′, —OS(O)NR²⁹R^29′, —OS(O)₂NR²⁹R^29′, —NR²⁹R^29′, —NR²⁹C(O)R³⁰, NR²⁹C(O)OR³⁰, —NR²⁹C(O)NR³⁰R^30′, —NR²⁹S(O)R³⁰, —NR²⁹S(O)₂R³⁰, —NR²⁹S(O)NR³⁰R^30′, —NR²⁹S(O)₂NR³⁰R^30′, —C(O)R²⁹, —C(O)OR²⁹or —C(O)NR²⁹R^29′;

R²⁸is H, D, C₁-C₇alkyl, C₂-C₇alkenyl, C₂-C₇alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl or sugar;

n is 1, 2, 3, 4 or 5;

p is 1, 2, 3, 4 or 5;

q is 1, 2, 3, 4 or 5; and

* is a covalent bond.

In some embodiments, L comprises a moiety L²of the formula

embedded image

wherein R²⁰, R²¹, R^21′, R²²and n are as defined herein.

In some embodiments, L comprises a moiety L²of the formula

embedded image

wherein R²⁰, R²⁷, n, p and q are as defined herein.

In some embodiments, L comprises additional groups such as polymers, such as polyolefins, polyethers, polyamides, copolymers, and the like, long-chain alkyl groups, peptides, and the like. In some embodiments, L comprises a polymer comprising from about 2 to about 200 monomer units. In some embodiments, L comprises a polymer comprising from about 2 to about 100 monomer units. In some embodiments, the polymer comprises from about 2 to about 20 monomer units. In some embodiments, L comprises a polyether. In some embodiments, L comprises a polyethylene glycol (PEG). In some embodiments, L comprises a polyethylene glycol (PEG) comprising from about 2 to about 200 monomer units. In some embodiments, L comprises a polyethylene glycol (PEG) comprising from about 2 to about 100 monomer units. In some embodiments, L comprises a polyethylene glycol (PEG) comprising from about 2 to about 50 monomer units. It will be appreciated that a range such as about 2 to 200, about 2 to about 100, about 2 to about 50, about 2 to about 20, and the like, contemplates all sub-ranges included therein. For example, the range about 2 to about 20, includes ranges such as 2 to 20, 2 to 15, 2 to 12, 2 to 10, 2 to 5, 3 to 20, 3 to 15, 3 to 12, 3 to 10, 3 to 5, and the like including all possible ranges. In some embodiments, L comprises a polyethylene glycol (PEG) comprising two monomer units. In some embodiments, L comprises a polyethylene glycol (PEG) comprising three monomer units. In some embodiments, L comprises a polyethylene glycol (PEG) comprising 6 monomer units. In some embodiments, L comprises a polyethylene glycol (PEG) comprising 10 monomer units. In some embodiments, L comprises a polyethylene glycol (PEG) comprising 12 monomer units.

In some embodiments, L comprises a moiety L³of the formula

embedded image

wherein m is an integer from 1 to about 50, m1 is an integer from 1 to about 30, m2 is an integer from 1 to 20, and each * represents a covalent bond to the rest of the conjugate.

In some embodiments, L comprises one or more amino acids (AA) as described herein. It will be appreciated that where L comprises one or more amino acids, the amino acids can be directly in the chain of atoms that connect D to B or ancillary to the chain of atoms that connect D to B. It will be further appreciated that where L comprises more than one amino acid, the amide bond may or may not be cleaved under physiological conditions. For example, in the case where L comprises a dipeptide directly in the chain of atoms that connect B to D, the amide bond in the dipeptide may be cleavable under physiological conditions to release B from D.

It will be further appreciated that where L comprises one or more amino acids, such amino acids can be naturally occurring amino acids of unnatural amino acids. It will be further appreciated that where L comprises one or more amino acids, such amino acids can be derivatized with one or more functional groups or protecting groups as are commonly known in the art.

In some embodiments, L further comprises one or more amino acids selected from the group consisting of lysine (Lys), asparagine (Asn), threonine (Thr), serine (Ser), isoleucine (Ile), methionine (Met), proline (Pro), histidine (His), glutamine (Gln), arginine (Arg), glycine (Gly), aspartic acid (Asp), glutamic acid (Glu), alanine (Ala), valine (Val), phenylalanine (Phe), leucine (Leu), tyrosine (Tyr), cysteine (Cys), tryptophan (Trp), phosphoserine (PSER), sulfo-cysteine, arginosuccinic acid (ASA), hydroxyproline, phosphoethanolamine (PEA), sarcosine (SARC), taurine (TAU), carnosine (CARN), citrulline (CIT), anserine (ANS), 1,3-methyl-histidine (ME-HIS), alpha-amino-adipic acid (AAA), beta-alanine (BALA), ethanolamine (ETN), gamma-amino-butyric acid (GABA), beta-amino-isobutyric acid (BAIA), alpha-amino-butyric acid (BABA), L-allo-cystathionine (cystathionine-A; CYSTA-A), L-cystathionine (cystathionine-B; CYSTA-B), cystine, allo-isoleucine (ALLO-ILE), DL-hydroxylysine (hydroxylysine (I)), DL-allo-hydroxylysine (hydroxylysine (2)), ornithine (ORN), and homocystine (HCY).

In some embodiments, L comprises one or more amino acids selected from the group consisting of L-asparagine, L-arginine, L-glycine, L-aspartic acid, L-glutamic acid, L-glutamine, L-cysteine, L-alanine, L-valine, L-leucine, L-isoleucine, 3-amino-L-alanine, D-asparagine, D-arginine, D-glycine, D-aspartic acid, D-glutamic acid, D-glutamine, D-cysteine, D-alanine, D-valine, D-leucine, D-isoleucine and 3-amino-D-alanine. In some embodiments, L comprises at least two amino acids selected from the group consisting of L-asparagine, L-arginine, L-glycine, L-aspartic acid, L-glutamic acid, L-glutamine, L-cysteine, L-alanine, L-valine, L-leucine, L-isoleucine and 3-amino-L-alanine. In some embodiments, L comprises at least two amino acids selected from the group consisting of L-asparagine, L-arginine, L-glycine, L-aspartic acid, L-glutamic acid, L-glutamine, L-cysteine, L-alanine, L-valine, L-leucine, L-isoleucine and 3-amino-L-alanine, wherein at least one amino acid is derivatized with a functional group or a protecting group as commonly known in the art.

It will be appreciated that the parts of L (e.g. L¹, L², L³, AA, and the like) can be combined in various arrangements to provide different embodiments of the present disclosure. In some embodiments, L is of the formula -L³-AA-L²-AA-L²-L¹-. In some embodiments, L is of the formula -L³-AA-L²-AA-L²-AA-AA-L¹-. In some embodiments, L comprises a group of the formula AA-AA-AA-L³-. In some embodiments, L comprises a group of the formula AA-AA-L¹-L³-. In some embodiments, L comprises a group of the formula AA-AA-AA-L³-. In some embodiments, L comprises a group of the formula AA-AA-L³-. In some embodiments, L comprises a group of the formula AA-L³-. In some embodiments, L comprises a group of the formula AA-(L³)₂- In some embodiments, L comprises a group of the formula -L¹-AA-AA-L³-. In some embodiments, L comprises a group of the formula L³. In some embodiments, L comprises a group of the formula (L³)₂.