Therapeutic efficacy of a MMAE-based anti-DR5 drug conjugate Oba01 in preclinical models of pancreatic cancer.

Pancreatic cancer (PC) is among the most aggressive malignancies associated with a 5-year survival rate of <9%, and the treatment options remain limited. Antibody-drug conjugates (ADCs) are a new class of anticancer agents with superior efficacy and safety profiles. We studied the antitumor activity of Oba01 ADC and the mechanism underlying the targeting of death receptor 5 (DR5) in preclinical PC models. Our data revealed that DR5 was highly expressed on the plasma membrane of PC cells and Oba01 showed potent in vitro antitumor activity in a panel of human DR5-positive PC cell lines. DR5 was readily cleaved by lysosomal proteases after receptor-mediated internalization. Monomethyl auristatin E (MMAE) was then released into the cytosol to induce G2/M-phase growth arrest, cell death via apoptosis induction, and the bystander effect. Furthermore, Oba01 mediated cell death via antibody-dependent cell-mediated cytotoxicity and complement-dependent cytotoxicity. For improved potency, we investigated the synergetic effect of Oba01 in combination with approved drugs. Oba01 combined with gemcitabine showed better antiproliferative activity than either standalone treatment. In cell- and patient-derived xenografts, Oba01 showed excellent tumoricidal activity in mono- or combinational therapy. Thus, Oba01 may provide a novel biotherapeutic approach and a scientific basis for clinical trials in DR5-expressing patients with PC.