The study treated 24 patients with advanced solid tumors who had progressed on prior treatment, with a median of three earlier lines of therapy. Tumor shrinkage was seen in 2 of 21 evaluable patients. A patient with gastrointestinal stromal tumor (GIST), a tumor type that rarely responds to checkpoint inhibitors, had a partial response lasting more than two years. Six further patients had stable disease as best response.

Translational data showed BI-1808 depleted regulatory T cells, reprogrammed myeloid cells and drove CD8+ T-cell activity in tumors, matching the mechanism seen in preclinical models. The 1000 mg dose every three weeks has been selected as the recommended Phase 2 dose and is being evaluated in Phase 2a cohorts focused on relapsed ovarian cancer and cutaneous T-cell lymphoma.

BI-1808 is the first antibody of its class to be tested in patients. It holds FDA Fast Track Designation in ovarian cancer and in mycosis fungoides and Sézary syndrome.

“Our findings provide the first clinical validation of TNFR2 as an immunotherapy target and show that BI-1808 can safely induce broad immune activation through mechanisms that differ from existing checkpoint inhibitors,” says Andres McAllister, Chief Medical Officer at BioInvent.