“Cold” Solid Tumors Become the Proving Ground for a New Generation of Engager and Immune-Priming Therapies

GT Biopharma announced on May 14, 2026 that the first patient has been dosed in a Phase 1 dose-escalation basket trial of GTB-5550, a B7-H3-targeted natural killer cell engager for solid tumors, with the trial spanning seven tumor types including prostate, pancreatic, ovarian, breast, head and neck, non-small cell lung, and bladder cancer.