Magrolimab and gemcitabine-cisplatin combination enhance phagocytic elimination of bladder cancer.

Abstract

e17035 Background: CD47 is an antiphagocytic signal and macrophage checkpoint that bladder and other cancer cells over-express to evade innate immunity. Magrolimab (Hu5F9-G4) a CD47 blocking antibody, promotes phagocytosis of cancer cells by macrophages and is being tested in several clinical trials (NCT02953509, NCT03248479, NCT02953782, NCT03558139). Chemotherapies synergize with magrolimab by increasing “eat me” signals on cancer cells, and thus enhancing phagocytosis. This synergy has been shown in MDS and AML, whereby magrolimab+azacitidine has shown encouraging efficacy in pre-clinical and clinical studies. This study aimed to investigate the effect of magrolimab as monotherapy and in combination with gemcitabine-cisplatin chemotherapy in bladder cancer. Methods: Phagocytosis of urothelial bladder cancer cells (639V) was evaluated in vitro with magrolimab alone and in combination with chemotherapy (gemcitabine + cisplatin). Treatment in vivo was evaluated in a xenograft mouse model. 639V cells were transplanted into NSG mice and upon confirmation of engraftment mice were randomized into 4 treatment cohorts: control (PBS), magrolimab, chemotherapy (cisplatin + gemcitabine), and magrolimab in combination with chemotherapy. In the first experimental setup treatment was started early in small tumors and in the second experimental setup treatment was started late after tumors have grown to large size. Tumor growth was monitored by in vivo bioluminescent imaging. Metastases were evaluated postmortem. Results: Chemotherapy increased calreticulin on bladder cancer cells. Magrolimab enhanced phagocytosis of bladder cancer cells in vitro and combination of magrolimab with chemotherapy further increased phagocytosis compared to either therapy alone. Magrolimab and chemotherapy, each alone decreased tumor growth in vivo but only combination of magrolimab with chemotherapy showed a strong inhibition of tumor growth, resulting in a significantly prolonged survival compared to all other treatment cohorts. This was shown for both, small tumors and large tumors. Metastases formation in liver and lungs was completely inhibited by treatment with magrolimab, whereas mice treated with chemotherapy alone or PBS control showed metastases in these organs. Conclusions: Magrolimab treatment in combination with chemotherapy was efficacious in preclinical in vitro and in vivo studies in bladder cancer and provides a novel treatment opportunity for patients with bladder cancer and other solid tumors.