OSE Immunotherapeutics SA announced that promising data from dose escalation Phase 1 of selective SIRPa inhibitor BI 765063 in patients with advanced solid tumors (Poster 983P) have been presented(1) at the 2021 European Society for Medical Oncology (ESMO) Virtual Conference held on September 16 - 21, 2021. The dose escalation part (Step 1) of the Phase 1 trial evaluating BI 765063 alone and in combination with BI 754091 (ezabenlimab) in advanced solid tumors has been completed. As of June 2021, a total of 18 patients have been treated (with 16 evaluable for efficacy). The combination of anti-SIRPa BI 765063 with BI745091 was well tolerated with no dose-limiting toxicities (DLTs) and the maximum tolerated dose (MTD) not reached. Promising early efficacy was observed with three partial responses (PR) in patients with microsatellite stable (MSS) advanced endometrium or colorectal cancer. The recommended Phase 2 dose and dosing schedule of BI 765063 was determined as 24 mg/kg with full receptor occupancy using a once every three weeks dosing schedule. The trial is currently recruiting MSS advanced colorectal and advanced endometrium cancer patients in the expansion Phase 1 trial (Step 2). Micro Satellite Instable (MSI) tumors can be effectively treated with immune checkpoint inhibitors alone. However, Micro Satellite Stable (MSS) colorectal and endometrial cancers represent the majority of these cancer patients where monotherapy with immune checkpoint inhibitors has limited benefit(2), highlighting the need for effective new combination therapies such as BI 765063 and BI 754091 for these patients. The previous data presented at the 2021 ASCO meeting indicated that BI 765063 was well tolerated and showed monotherapy activity in heavily pre-treated solid tumor patients. In particular, a durable partial response was observed in an advanced hepatocellular carcinoma (HCC) patient (data presented at the ASCO 2021). The study is being conducted by OSE Immunotherapeutics as part of a collaboration and license agreement under which Boehringer Ingelheim obtained exclusive rights to BI 765063.