Method of targeting specific cell populations using cell-binding agent maytansinoid conjugates linked via a non-cleavable linker, said conjugates and methods of making said

1. A cell-binding agent maytansinoid conjugate comprising at least one thiol-containing maytansinoid linked to a cell-binding agent via a non-cleavable linker,

wherein the cell-binding agent is an antibody, a single chain antibody or an antibody fragment that specifically binds to a target cell,

wherein the antibody, single chain antibody or antibody fragment comprises a human constant region,

wherein the non-cleavable linker is a linker that is substantially resistant to acid-induced cleavage, light-induced cleavage, peptidase-induced cleavage, esterase-induced cleavage, and disulfide bond cleavage,

wherein the conjugate is highly cytotoxic, and

wherein the maximum tolerated dose (MTD) in rodents of the cell-binding maytansinoid conjugate is at least about 150 mg/kg,

provided that the cell-binding agent is not an anti-erbB antibody.

2. The cell-binding agent maytansinoid conjugate of claim 1 ,

wherein the non-cleavable linker is derived from a maleimido-based moiety.

3. The cell-binding agent maytansinoid conjugate of claim 2 , wherein the non-cleavable linker is derived from a maleimido-based moiety selected from N-succinimidyl 4-(maleimidomethyl)cyclohexanecarboxylate (SMCC), N-succinimidyl-4-(N-maleimidomethyl)-cyclohexane-1-carboxy-(6-amidocaproate) (LC-SMCC), k-maleimidoundecanoic acid N-succinimidyl ester (KMUA), γ-maleimidobutyric acid N-succinimidyl ester (GMBS), ε-maleimidcaproic acid N-hydroxysuccinimide ester (EMCS), m-maleimidobenzoyl-N-hydroxysuccinimide ester (MBS), N-αa-maleimidoacetoxy)-succinimide ester (AMAS), succinimidyl-6-(β-maleimidopropionamido)hexanoate (SMPH), N-succinimidyl 4-(p-maleimidophenyl)-butyrate (SMPB), N-(p-maleimidophenyl)isocyanate (PMPI), or a sulfo-succinimidyl variant or an analog thereof.

4. The cell-binding agent maytansinoid conjugate of claim 3 , wherein the non-cleavable linker is derived from SMCC.

5. The cell-binding agent maytansinoid conjugate of claim 1 , wherein the linker is at any one of the C-3 hydroxyl, C-14 hydroxymethyl, C-15 hydroxyl or C-20 desmethyl groups of the at least one maytansinoid.

6. The cell-binding agent maytansinoid conjugate of claim 1 , wherein the at least one maytansinoid is an N-methyl-alanine-containing ester of maytansinol.

7. The cell-binding agent maytansinoid conjugate of claim 1 , wherein the at least one maytansinoid is an N-methyl-cysteine-containing ester of maytansinol.

8. The cell-binding agent maytansinoid conjugate of claim 1 , wherein the at least one maytansinoid is represented by formula (II′-L), (II′-D) or (II′-D,L):

wherein:

Y 1 ′ represents (CR 7 R 8 ) 1 (CR 9 =CR 10 ) p (C=C) q A 0 (CR 5 R 6 ) m D u (CR 11 =CR 12 ) r (C=C) s B t (CR 3 R 4 ) n CR 1 R 2 S,

wherein:

R 1 to R 12 are each independently linear alkyl or alkenyl having 1 to 10 carbon atoms, branched or cyclic alkyl or alkenyl having 3 to 10 carbon atoms, phenyl, substituted phenyl or heterocyclic aromatic or heterocycloalkyl radical, and in addition, R 2 to R 12 can be H;

A, B, and D, each independently is cyclic alkyl or cyclic alkenyl having 3 to 10 carbon atoms, simple or substituted aryl, or heterocyclic aromatic or heterocycloalkyl radical;

1, m, n, o, p, q, r, s, t and u are each independently 0 or an integer of 1 to 5, provided that at least two of 1, m, n, o, p, q, r, s, t and u are not both zero; and

May represents a maytansinoid that bears a side chain at C-3 hydroxyl, C-14 hydroxymethyl, C-15 hydroxyl or C-20 desmethyl.

9. The cell-binding agent maytansinoid conjugate of claim 8 , wherein R 1 is methyl and R 2 is H or R 1 and R 2 are methyl.

10. The cell-binding agent maytansinoid conjugate of claim 8 , wherein R 1 is methyl, R 2 is H, R 5 , R 6 , R 7 and R 8 are each H, 1 and m are each 1, and n is 0; or

wherein R 1 and R 2 are methyl, R 5 , R 6 , R 7 , R 8 are each H, 1 and m are each 1, and n is 0.

11. The cell-binding agent maytansinoid conjugate of claim 1 , wherein the at least one maytansinoid is represented by formula (II-L), (II-D), or (II-D,L):

wherein:

Y 1 represents (CR 7 R 8 ) l (CR 5 R 6 ) m (CR 3 R 4 ) n CR 1 R 2 S, wherein:

R 1 to R 8 are each independently, linear alkyl or alkenyl having 1 to 10 carbon atoms, branched or cyclic alkyl or alkenyl having 3 to 10 carbon atoms, phenyl, substituted phenyl or heterocyclic aromatic or heterocycloalkyl radical, and in addition R 2 to R 8 can be H;

l, m and n are each independently an integer of 1 to 5, and in addition n can be 0; and

May represents a maytansinoid that bears the side chain at C-3 hydroxyl, C-14 hydroxymethyl, C-15 hydroxyl or C-20 desmethyl.

12. The cell-binding agent maytansinoid conjugate of claim 11 , wherein R 1 is methyl and R 2 is H or R 1 and R 2 are methyl.

13. The cell-binding agent maytansinoid conjugate of claim 11 , wherein R 1 is methyl, R 2 is H, R 5 , R 6 , R 7 and R 8 are each H, 1 and m are each 1, and n is 0; or

wherein R 1 and R 2 are methyl, R 5 , R 6 , R 7 , R 8 are each H, 1 and m are each 1, and n is 0.

14. The cell-binding agent maytansinoid conjugate of claim 1 , wherein the at least one maytansinoid is represented by formula 4 1 ′:

wherein:

Y 1 ′ represents (CR 7 R 8 ) l (CR 9 =CR 10 ) p (C=C) q A 0 (CR 5 R 6 ) m (CR 11 =CR 12 ) r (C=C) 8 B t (CR 3 R 4 ) n CR 1 R 2 S,

wherein:

R 1 to R 12 are each independently linear alkyl or alkenyl having 1 to 10 carbon atoms, branched or cyclic alkyl or alkenyl having 3 to 10 carbon atoms, phenyl, substituted phenyl or heterocyclic aromatic or heterocycloalkyl radical, and in addition, R 2 to R 12 can be H;

A, B, and D, each independently is cyclic alkyl or cyclic alkenyl having 3 to 10 carbon atoms, simple or substituted aryl, or heterocyclic aromatic or heterocycloalkyl radical;

l, m, n, o, p, q, r, s, t and u are each independently 0 or an integer of 1 to 5, provided that at least two of l, m, n, o, p, q, r, s, t and u are not both zero; and

May represents a maytansinoid that bears a side chain at C-3 hydroxyl, C-14 hydroxymethyl, C-15 hydroxyl or C-20 desmethyl.

15. The cell-binding agent maytansinoid conjugate of claim 14 , wherein R 1 is methyl and R 2 is H or R 1 and R 2 are methyl.

16. The cell-binding agent maytansinoid conjugate of claim 14 , wherein R 1 is methyl, R 2 is H, R 5 , R 6 , R 7 and R 8 are each H, 1 and m are each 1, and n is 0; or

wherein R 1 and R 2 are methyl, R 5 , R 6 , R 7 , R 8 are each H, 1 and m are each 1, and n is 0.

17. The cell-binding agent maytansinoid conjugate of claim 1 , wherein the at least one maytansinoid is represented by formula 4 1 :

wherein:

Y 1 represents (CR 7 R 8 ) l (CR 5 R 6 ) m (CR 3 R 4 ) n CR 1 R 2 S, wherein:

R 1 to R 5 are each independently, linear alkyl or alkenyl having 1 to 10 carbon atoms, branched or cyclic alkyl or alkenyl having 3 to 10 carbon atoms, phenyl, substituted phenyl or heterocyclic aromatic or heterocycloalkyl radical, and in addition R 2 to R 8 can be H; and

l, m and n are each independently an integer of 1 to 5, and in addition n can be 0.

18. The cell-binding agent maytansinoid conjugate of claim 17 , wherein R 1 is methyl and R 2 is H or R 1 and R 2 are methyl.

19. The cell-binding agent maytansinoid conjugate of claim 17 , wherein R 1 is methyl, R 2 is H, R 5 , R 6 , R 7 and R 8 are each H, l and m are each 1, and n is 0; or

wherein R 1 and R 2 are methyl, R 5 , R 6 , R 7 , R 8 are each H, l and m are each 1, and n is 0.

20. The cell-binding agent maytansinoid conjugate of claim 1 , wherein the at least one maytansinoid is N 2′ -deacetyl-N 2′ -(3-mercapto-1-oxopropyl)-maytansine (DM1).

21. The cell-binding agent maytansinoid conjugate of claim 1 , wherein the at least one maytansinoid is N 2′ -deacetyl-N 2′ -(4-mercapto-1-oxopentyl)-maytansine (DM3).

22. The cell-binding agent maytansinoid conjugate of claim 1 , wherein the at least one maytansinoid is N 2′ -deacetyl-N 2′ -(4-methyl-4-mercapto-1-oxopentyl)-maytansine (DM4).

23. The cell-binding agent maytansinoid conjugate of claim 1 , wherein the cell-binding agent binds to tumor cells; virus infected cells, microorganism infected cells, parasite infected cells, autoimmune cells, activated cells in graft rejection or graft vs. host disease, myeloid cells, activated T-cells, B cells, or melanocytes; cells expressing the CD33, CD19, CanAg, or CALLA antigens; or cells expressing insulin growth factor receptor, or folate receptor.

24. The cell-binding agent maytansinoid conjugate of claim 23 , wherein the cell-binding agent binds to cells chosen from breast cancer cells, kidney cancer cells, lung cancer cells, prostate cancer cells, ovarian cancer cells, colorectal cancer cells, gastric cancer cells, squamous cancer cells, small-cell lung cancer cells, non-small-cell lung cancer cells, pancreatic cancer cells, testicular cancer cells, neuroblastoma cells, melanoma cells, or cells from cancer of the lymphatic organs.

25. The cell-binding agent maytansinoid conjugate of claim 1 , wherein the cell-binding agent is a resurfaced antibody, a resurfaced single chain antibody, or a resurfaced antibody fragment that specifically bind to a target cell.

26. The cell-binding agent maytansinoid conjugate of claim 1 , wherein the cell-binding agent is a humanized antibody, a humanized single chain antibody, or a humanized antibody fragment that specifically bind to a target cell.

27. The cell-binding agent maytansinoid conjugate of claim 1 , wherein the cell-binding agent is a human antibody, a human single chain antibody, or a human antibody fragment that specifically bind to a target cell.

28. The cell-binding agent maytansinoid conjugate of claim 1 , wherein the cell-binding agent is an anti-PSMA antibody, an anti-CanAg antibody, an anti-CD19 antibody, an anti-CD33 antibody, an anti-CALLA antibody, an anti-CD56 antibody, or an anti-IGF-IR antibody.

29. The cell-binding agent maytansinoid conjugate of claim 8 , wherein the maytansinoid is N 2′ -deacetyl-N 2′ -(4-mercapto-1-oxopentyl)-maytansine (DM3), or N 2′ -deacetyl-N 2′ -(4-methyl-4-mercapto-1-oxopentyl)-maytansine (DM4).

30. The cell-binding agent maytansinoid conjugate of claim 11 , wherein the maytansinoid is N 2′ -deacetyl-N 2′ -(4-mercapto-1-oxopentyl)-maytansine (DM3), or N 2′ -deacetyl-N 2′ -(4-methyl-4-mercapto-1-oxopentyl)-maytansine (DM4).

31. The cell-binding agent maytansinoid conjugate of claim 14 , wherein the maytansinoid is N 2′ -deacetyl-N 2′ -(4-mercapto-1-oxopentyl)-maytansine (DM3), or N 2′ -deacetyl-N 2′ -(4-methyl-4-mercapto-1-oxopentyl)-maytansine (DM4).

32. A composition comprising the cell-binding agent maytansinoid conjugate of claim 1 , and a carrier.

33. The cell-binding agent maytansinoid conjugate of claim 1 , having the structure:

or a fragment thereof, wherein n is between 1 to 10.

34. The cell binding agent maytansinoid conjugate of claim 1 , wherein an average of 1 to about 10 maytansinoids are covalently linked to the cell-binding agent.

35. The cell binding agent maytansinoid conjugate of claim 1 , wherein

the cell-binding agent is a resurfaced antibody, a resurfaced single chain antibody, a resurfaced antibody fragment, a humanized antibody, a humanized single chain antibody, or a humanized antibody fragment that specifically binds to target cells,

the maytansinoid is N 2′ -deacetyl-N 2′ -(3-mercapto-1-oxopropyl)-maytansine (DM1), and the linker is derived from SMCC.