Antibody drug conjugates

A compound or pharmaceutically acceptable salt thereof, of formula (C-1):

• wherein:
• R1 is an attachment group;
• L1 is a bridging spacer;
• W is N or CRw, wherein Rw is H or C1-C6alkyl (e.g. Rw is H);
• L2 and L3 are each independently a connecting spacer;
• E1 and E2 are each independently a peptide group comprising 1 to 6 amino acids, wherein said peptide group is optionally substituted by a hydrophilic group;
• A1 and A2 are each independently a bond, —OC(═O)—*,
• —OC(═O)N(CH3)CH2CH2N(CH3)C(═O)—* or —OC(═O)N(CH3)C(Ra)2C(Ra)2N(CH3)C(═O)—*,
• wherein each Ra is independently selected from H, C1-C6alkyl, and C3-C8cycloalkyl and the * of A1 or A2 indicates the point of attachment to D1 or D2;
• D1 and D2 are each independently a pharmaceutically active drug, optionally with the proviso that neither D1 nor D2 is a BH3 mimetic;
• L4 and L5 are each independently a spacer moiety;
• R2 and R3 are each independently selected from:
• (i) a polysarcosine with the following moiety:
• wherein
• f is an integer between 3 and 25;
• and
• R23 is H, —CH3 or —CH2CH2C(═O)OH;
• (ii) a polyethylene glycol of formula:
• wherein g and h are independently an integer between 2 and 30;
• and
• m and n are each independently 1;
• or a pharmaceutically acceptable salt thereof.