GSK Says Drug Candidate Risvutatug Rezetecan Shows 61% Response Rate in Phase 1b Lung Cancer Trial

03:44 AM EDT, 10/19/2026 (MT Newswires) -- GSK (GSK) said Sunday its experimental drug risvutatug rezetecan shrank tumors in 61% of the 18 patients who could be assessed in a phase 1b trial in relapsed, extensive-stage small cell lung cancer. The response rate was 32% among 22 patients given a lower dose, and the higher 8 milligram-per-kilogram dose selected from these results is now in a larger phase 3 trial, the company said. Severe side effects affected 42% of patients on the higher dose and 15% on the lower, mostly blood-related, and one case of lung inflammation occurred among 50 patients, GSK said. The results will be presented at the European Society for Medical Oncology congress in Spain and will add to Chinese phase 3 data in the same cancer, it added.