Pyrrolobenzodiazepine-antibody conjugates

1. A conjugate of formula (I):

Ab-(DL) p   (I)

wherein:

Ab is an antibody that binds to DLK1 and comprises a VH domain comprising a VH CDR1 with the amino acid sequence of SEQ ID NO.5, a VH CDR2 with the amino acid sequence of SEQ ID NO.6, and a VH CDR3 with the amino acid sequence of SEQ ID NO.7; and, a VL domain comprising a VL CDR1 with the amino acid sequence of SEQ ID NO.8, a VL CDR2 with the amino acid sequence of SEQ ID NO.9, and a VL CDR3 with the amino acid sequence of SEQ ID NO.10;

wherein DL is

wherein:

X is selected from the group comprising: a single bond, —CH2— and —C 2 H 4 —;

n is from 1 to 8;

m is 0 or 1;

R 7 is either methyl or phenyl;

when there is a double bond between C2 and C3, R 2 is selected the group consisting of:

(ia) C 5-10 aryl group, optionally substituted by one or more substituents selected from the group comprising: halo, nitro, cyano, ether, carboxy, ester, C 1-7 alkyl, C 3-7 heterocyclyl and bis-oxy-C 1-3 alkylene;

(ib) C 1-5 saturated aliphatic alkyl;

(ic) C 3-6 saturated cycloalkyl;

wherein each of R 21 , R 22 and R 23 are independently selected from H, C 1-3 saturated alkyl, C 2-3 alkenyl, C 2-3 alkynyl and cyclopropyl, where the total number of carbon atoms in the R 2 group is no more than 5;

wherein one of R 25 a and R 25b is H and the other is selected from: phenyl, which phenyl is optionally substituted by a group selected from halo, methyl, methoxy pyridyl and thiophenyl; and

where R 24 is selected from: H, C 1-3 saturated alkyl C 2-3 alkenyl, C 2-3 alkynyl cyclopropyl phenyl, which phenyl is optionally substituted by a group selected from halo, methyl, methoxy pyridyl and thiophenyl;

when there is a single bond between C2 and C3, R 2 is

where R 26a and R 26b are independently selected from H, F, C 1-4 saturated alkyl, C 2-3 alkenyl, which alkyl and alkenyl groups are optionally substituted by a group selected from C 1-4 alkyl amido and C 1-4 alkyl ester; or, when one of R 26 a and R 26b is H, the other is selected from nitrile and a C 1-4 alkyl ester;

when there is a double bond between C2′ and C3′, R 12 is selected the group consisting of:

(iia) C 5-10 aryl group, optionally substituted by one or more substituents selected from the group comprising: halo, nitro, cyano, ether, carboxy, ester, C 1-7 alkyl, C 3-7 heterocyclyl and bis-oxy-C 1-3 alkylene;

(iib) C 1-5 saturated aliphatic alkyl;

(iic) C 3-6 saturated cycloalkyl;

wherein each of R 31 , R 32 and R 33 are independently selected from H, C 1-3 saturated alkyl, C 2-3 alkenyl, C 2-3 alkynyl and cyclopropyl, where the total number of carbon atoms in the R 12 group is no more than 5;

wherein one of R 35a and R 35b is H and the other is selected from: phenyl, which phenyl is optionally substituted by a group selected from halo, methyl, methoxy pyridyl, and thiophenyl; and

wherein R 34 is selected from: H, C 1-3 saturated alkyl, C 2-3 alkenyl, C 2-3 alkynyl, cyclopropyl, phenyl, which phenyl is optionally substituted by a group selected from halo, methyl, methoxy, pyridyl, and thiophenyl;

when there is a single bond between C2′ and C3′, R 12 is

where R 36a and R 36b are independently selected from H, F, C 1-4 saturated alkyl, C 2-3 alkenyl, which alkyl and alkenyl groups are optionally substituted by a group selected from C 1-4 alkyl amido and C 1-4 alkyl ester; or, when one of R 36a and R 36b is H, the other is selected from nitrile and a C 1-4 alkyl ester;

and p is from 1 to 8.

2. The conjugate according to claim 1 , wherein X is —CH 2 —.

3. The conjugate according to claim 1 , wherein n is 1 to 4.

4. The conjugate according to claim 3 , wherein n is 2.

5. The conjugate according to claim 1 , wherein there is a double bond between C2 and C3, and R 2 is a C 1-5 saturated aliphatic alkyl group.

6. The conjugate according to claim 5 , wherein R 2 is methyl, ethyl or propyl.

7. The conjugate according to claim 1 , wherein there is a double bond between C2 and C3, and R 2 is:

(a) phenyl, which bears one to three substituent groups, wherein the substituents may be selected from methoxy, ethoxy, fluoro, chloro, cyano, bis-oxy-methylene, methyl-piperazinyl, morpholino and methyl-thiophenyl;

(b) cyclopropyl;

(c) a group of formula:

wherein the total number of carbon atoms in the R 2 group is no more than 3;

(d) the group:

or

(e) a group of formula:

wherein R 24 is selected from H and methyl.

8. The conjugate according to claim 1 , wherein there is a single bond between C2 and C3, R 2 is

and

(a) R 26a and R 26b are both H;

(b) R 26a and R 26b are both methyl; or

(c) one of R 26a and R 26b is H, and the other is selected from C 1-4 saturated alkyl, C 2-3 alkenyl, which alkyl and alkenyl groups are optionally substituted.

9. The conjugate according to claim 1 , wherein there is a double bond between C2′ and C3′, and R 12 is a C 1-5 saturated aliphatic alkyl group.

10. The conjugate according to claim 9 , wherein R 12 is methyl, ethyl or propyl.

11. The conjugate according to claim 1 , wherein there is a double bond between C2′ and C3′, and R 12 is:

(a) phenyl, which bears one to three substituent groups, wherein the substituents are selected from methoxy, ethoxy, fluoro, chloro, cyano, bis-oxy-methylene, methyl-piperazinyl, morpholino and methyl-thiophenyl;

(b) cyclopropyl;

(c) a group of formula:

wherein the total number of carbon atoms in the R 12 group is no more than 3;

(d) the group:

or

(e) a group of formula:

wherein R 34 is selected from H and methyl.

12. The conjugate according to claim 1 , wherein there is a single bond between C2′ and C3′, R 12 is

and

(a) R 36a and R 36b are both H;

(b) R 36a and R 36b are both methyl; or

(c) one of R 36a and R 36b is H, and the other is selected from C 1-4 saturated alkyl, C 2-3 alkenyl, which alkyl and alkenyl groups are optionally substituted.

13. The conjugate according to claim 1 , wherein DL is:

14. The conjugate according to claim 1 , wherein the antibody comprises a VH domain having the sequence of SEQ ID NO.1.

15. The conjugate according to claim 1 , wherein the antibody comprises a VL domain having the sequence of SEQ ID NO. 2.

16. The conjugate according to claim 1 , wherein the antibody comprises a heavy chain having the sequence of SEQ ID NO. 3, or a heavy chain having the sequence of SEQ ID NO. 11.

17. The conjugate according to claim 1 , wherein the antibody comprises a light chain having the sequence of SEQ ID NO. 4.

18. A composition comprising a mixture of conjugates as defined in claim 1 , wherein the average drug loading per antibody in the mixture of conjugates is about 1 to about 4.

19. A pharmaceutical composition comprising the conjugate of claim 1 , and a pharmaceutically acceptable diluent, carrier or excipient.

20. The pharmaceutical composition of claim 19 , further comprising a therapeutically effective amount of a chemotherapeutic agent.

21. A conjugate of formula (I):

Ab-(DL) p   (I)

wherein:

Ab is an antibody that binds to DLK1 and comprises a VH domain comprising a VH CDR1 with the amino acid sequence of SEQ ID NO.5, a VH CDR2 with the amino acid sequence of SEQ ID NO.6, and a VH CDR3 with the amino acid sequence of SEQ ID NO.7; and, a VL domain comprising a VL CDR1 with the amino acid sequence of SEQ ID NO.8, a VL CDR2 with the amino acid sequence of SEQ ID NO.9, and a VL CDR3 with the amino acid sequence of SEQ ID NO.10;

wherein DL is

and p is from 1 to 8.

22. The conjugate according to claim 21 , wherein the antibody comprises a VH domain having the sequence of SEQ ID NO.1 and a VL domain having the sequence of SEQ ID NO. 2.

23. A composition comprising a mixture of conjugates as defined in claim 21 , wherein the average drug loading per antibody in the mixture of conjugates is about 1 to about 4.

24. A pharmaceutical composition comprising the conjugate of claim 21 , and a pharmaceutically acceptable diluent, carrier or excipient.

25. The pharmaceutical composition of claim 24 , further comprising a therapeutically effective amount of a chemotherapeutic agent.