Background: Bispecific T-cell engagers represent a promising therapeutic approach for patients with solid tumors; however, these agents require an appropriate target antigen. B7-H6 is an encouraging target as it is expressed on multiple solid tumors but shows only limited expression on normal tissue (1). BI 765049 is a novel immunoglobulin G (IgG)-like T-cell engager designed to simultaneously bind B7-H6-expressing tumor cells and CD3 on T-cells resulting in the formation of a cytolytic synapse that triggers apoptosis of the tumor cells. Methods: NCT06091930 is a Phase I, non-randomized, open-label, multi-center, dose escalation and expansion trial that aims to assess the safety and tolerability of BI 765049 alone or in combination with programmed cell death protein 1 inhibitor ezabenlimab, in patients with advanced or unresectable gastric cancer, colorectal cancer (CRC), pancreatic ductal adenocarcinoma, hepatocellular cancer, head and neck squamous cell carcinoma, or non-small cell lung cancer. Patients must have progressed on, or be ineligible for, standard therapies. Key inclusion criteria include confirmed B7-H6 expression (central pathology review) except in CRC; ≥1 evaluable target lesion outside of the central nervous system (Response Evaluation Criteria in Solid Tumors [RECIST] v1.1); and Eastern Cooperative Oncology Group performance status 0/1. Patients with prior B7-H6-targeted treatment are ineligible. The study is divided into four parts: dose escalation and expansion of BI 765049 monotherapy (Parts I and II, respectively), and in combination with ezabenlimab (Parts III and IV, respectively). BI 765049 dose escalation will be guided by a Bayesian logistic regression model with overdose control. Treatment will continue until progressive disease or discontinuation for other reasons, or for up to 36 months. The primary endpoint for Parts I and III is the occurrence of dose-limiting toxicities; and for Parts II and IV it is objective response (OR; determined by the investigator; RECIST v1.1). The secondary endpoints for Parts I and III are pharmacokinetic (PK) parameters and OR (RECIST v1.1); and for Parts II and IV secondary endpoints are progression-free survival, duration of response, disease control, PK measurements, and OR (immunotherapy RECIST [iRECIST]). 1. Zhang W, et al. Clin Cancer Res 2022;28(23):5190–5201. Clinical trial information: NCT06091930.