Harpoon announces updated interim data from Phase 1/2 trial of HPN328

Harpoon Therapeutics announced the updated interim monotherapy data from its Phase 1/2 clinical trial evaluating HPN328 in small cell lung cancer and other neuroendocrine tumor types in a poster at the European Society of Medical Oncology Congress 2023. HPN328 targets delta-like ligand 3 and is derived from Harpoon’s proprietary Tri-specific T cell Activating Construct platform designed to recruit a patient’s own immune cells to kill tumor cells. HPN328 was generally well tolerated across all dose cohorts. Treatment-related adverse events occurred in 67 patients, and Grade greater than or equal to 3 TRAEs in 18 patients. CRS was most common and was primarily Grade 1 or 2. No dose limiting toxicities occurred at target doses, and the target maximum tolerated dose has not been reached as of the data cut off on September 12, 2023. The preliminary response data for evaluable patients treated in 1 mg priming dose cohorts showed confirmed response rate of 35% across all tumor types. In SCLC, the confirmed response rate was 32% with one confirmed complete response. In patients with other neuroendocrine tumor types, such as prostate cancer, small cell cervical, small cell bladder, and large cell lung cancer, 42% confirmed response rate was observed, including two confirmed complete responses in small cell bladder and small cell cervical tumor types. The duration of response data in the 1 mg priming dose cohorts continues to mature.