Biopharmaceutical company GSK plc (LSE: GSK) (NYSE: GSK) on Monday reported a confirmed overall response rate of 61% for its investigational antibody-drug conjugate risvutatug rezetecan (Ris-Rez) at the 8 mg/kg dose in a Phase Ib trial involving patients with relapsed extensive-stage small cell lung cancer (ES-SCLC). The global data from the EMBOLD PanTumour-101 trial support the selection of this dose for the ongoing Phase III EMBOLD SCLC-301 study.

The response rate compared with 32% at the 6 mg/kg dose. At a median follow-up of 100.5 days, the safety profile was manageable, although Grade 3 or higher treatment-related adverse events occurred in 42% of patients receiving the higher dose, compared with 15% at the lower dose. Interstitial lung disease was reported in one of the 50 patients, a moderate Grade 2 case.

These findings will be presented at the European Society for Medical Oncology Congress 2026 in Madrid, alongside further data from GSK's EMBOLD clinical programme. The results add to positive Phase III data reported in Chinese patients and support continued development of Ris-Rez for a cancer characterised by frequent relapse and limited treatment options.