Cooperation of the agonistic DR5 antibody apomab with chemotherapy to inhibit orthotopic lung tumor growth and improve survival.

PURPOSE Apomab is a fully human monoclonal antibody that induces programmed cell death through the proapoptotic receptor DR5 in various cancer cells but not in normal cells. Several lung cancer cell lines express DR5 and exhibit apoptosis in response to apomab in vitro. EXPERIMENTAL DESIGN We investigated the efficacy of apomab and its interaction with chemotherapy in xenograft models based on human NCI-H460 non-small-cell lung carcinoma cells. In an established model of s.c. tumor xenografts, apomab or Taxol plus carboplatin chemotherapy delayed tumor progression, whereas combined treatment caused tumor regression and a substantially longer growth delay. To test apomab activity in a setting that may more closely mimic lung cancer pathology in patients, we developed a lung orthotopic model. RESULTS In this model, microcomputed tomography imaging showed that apomab, chemotherapy, or combination treatment significantly inhibited tumor growth compared with vehicle, whereas the combination caused greater inhibition in tumor growth relative to chemotherapy or apomab. Similarly, histologic analysis revealed that apomab, chemotherapy, or the combination significantly reduced tumor size compared with vehicle, whereas the combination induced significantly greater reduction in tumor size than did chemotherapy or apomab. Furthermore, combined treatment improved 105-day survival relative to vehicle (P = 0.0023) as well as to apomab (P = 0.0445) or chemotherapy (P = 0.0415). CONCLUSION These results show a positive interaction of apomab with chemotherapy, evidenced by significant inhibition of tumor growth as well as improved survival, thus supporting further investigation of this therapeutic approach in lung cancer patients.