MC-GGFG-AM-(10Me-11F-Camptothecin) is a linker-payload conjugate used to synthesize ZW251. ZW251 an antibody-drug conjugate (ADC) targeting human GPC3 . ZW251 consists of a humanized IgG1 antibody conjugated to a novel camptothecin-based topoisomerase 1 inhibitor, ZD06519, via a linker. The linker is the maleimide anchor and a glycyl glycyl phenylalanyl glycine (GGFG)-aminomethyl (AM) cleavable linker. ZW251 has high affinity with human and cynomolgus monkey GPC3. ZW251 displays rapid internalization in GPC3-expressing HCC cell lines, and bystander-mediated killing of GPC3 negative cancer cells IC50& Target:Topoisomerase I