| CPC A61K 31/122 (2013.01) [A61K 31/19 (2013.01); A61K 47/55 (2017.08); A61K 47/551 (2017.08); A61K 47/554 (2017.08); A61K 47/58 (2017.08); A61K 47/59 (2017.08); A61K 47/593 (2017.08); A61K 47/62 (2017.08); A61K 47/64 (2017.08); A61K 47/6415 (2017.08); A61K 47/642 (2017.08); A61K 47/65 (2017.08); A61K 47/68 (2017.08); A61K 47/6803 (2017.08); A61K 47/6889 (2017.08)] | 20 Claims |
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1. A compound of the formula I
![]() or a pharmaceutically acceptable salt thereof, where X is selected from a first group consisting of —S— and —O—; R1 represents an antibody affinity moiety;
R3 is —H;
R2, R4 and R5 are —CH3; and
R6 is selected from a second group consisting of —CH3, —CH2—OH, —CH2—O(—(C═O)—CH3, —O—(C═O)—CH2—CH2—CH2—(C═O)—OH, —O(C═O)—C6H3(NO2)2, and —CH2—(C═O)—(CH3)2.
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