Preclinical evaluation of a novel antibody-drug conjugate targeting DR5 for lymphoblastic leukemia therapy

Acute lymphoblastic leukemia (ALL) is an aggressive hematological neoplasm resulting from immature lymphoid precursors. An antibody-drug conjugate (ADC), coupling a small molecule covalently with a targeting antibody, can specifically kill tumor cells. Death receptor 5 (DR5) is considered as a promising anti-tumor drug target. In this study, we describe the preclinical evaluation of a novel DR5-targeting ADC (Oba01) as a potential therapeutic against ALL. Oba01 utilizes anti-DR5 humanized monoclonal antibody (zaptuzumab) coupled via a cleavable linker to monomethyl auristatin E (MMAE). Oba01 can specifically bind to DR5 on the tumor cells and transfer into lysosome via DR5-mediated endocytosis. It then effectively releases the MMAE, which can bind to the tubulin and prevent its aggregation, thereby leading to a significant inhibition of proliferation and cell death in tumor cells. Additionally, Oba01 displays significant dose-dependent tumoricidal activity in cell-derived xenograft (CDX) and patient-derived xenograft (PDX) mouse models. More importantly, toxicity analysis of Oba01 showed a favorable safety profile, and pharmacokinetic analysis illustrated an excellent stability and tolerability in rats and cynomolgus monkeys. Taken together, our data conclusively demonstrate that Oba01 is an attractive candidate for further clinical trials in DR5-positive ALL patients.