London, United Kingdom, October 18, 2026
GSK has announced the first global clinical data for risvutatug rezetecan (Ris-Rez), its investigational B7-H3-targeted antibody-drug conjugate (ADC), in patients with relapsed extensive-stage small cell lung cancer (ES-SCLC). Results from the Phase Ib dose-optimisation portion of the EMBOLD PanTumour-101 clinical trial showed promising antitumour activity and a manageable safety profile. At the 8 mg/kg dose, Ris-Rez achieved a confirmed objective response rate of 61% among evaluable patients, compared with 32% at the 6 mg/kg dose. The findings build on positive Phase III results previously reported in Chinese patients and support the continued development of Ris-Rez as a potential treatment for this aggressive form of lung cancer. GSK announced the results on October 18, 2026, ahead of their presentation at the European Society for Medical Oncology (ESMO) Congress 2026 in Madrid, Spain. The medicine remains investigational and is not yet approved for routine clinical use.
Phase Ib Trial Shows Antitumour Activity
The Phase Ib dose-optimisation study evaluated Ris-Rez in patients whose extensive-stage small cell lung cancer had returned after previous treatment. Among evaluable patients receiving the 8 mg/kg dose, 11 of 18 patients achieved a confirmed response, corresponding to an objective response rate of 61%. In the 6 mg/kg group, 7 of 22 evaluable patients responded, resulting in a confirmed response rate of 32%. These results suggest greater antitumour activity at the higher dose in this early-stage analysis, although the groups were small and the findings require confirmation in larger clinical trials. The safety profile was described as manageable at both doses. Treatment-related adverse events of Grade 3 or higher were reported in 42% of patients receiving 8 mg/kg and 15% receiving 6 mg/kg, highlighting the importance of balancing potential efficacy with tolerability. The study findings, including the dose comparison, will help inform further clinical evaluation of this investigational therapy.
How Ris-Rez Targets Cancer Cells
Ris-Rez is a B7-H3-targeted antibody-drug conjugate, a type of cancer medicine designed to deliver a cell-killing drug to tumour cells expressing a specific target. B7-H3 is a cell-surface protein found at elevated levels in several solid tumours, including small cell lung cancer. The antibody component is designed to bind to B7-H3, enabling delivery of its linked cytotoxic payload to cancer cells. This targeted approach aims to concentrate anticancer activity while limiting exposure to healthy tissues, although adverse effects can still occur. Small cell lung cancer is an aggressive malignancy that often spreads rapidly and frequently returns following initial treatment. Patients with relapsed extensive-stage disease have limited treatment options, making the development of new therapies an important research priority. By investigating a B7-H3-directed ADC, GSK is exploring a different treatment strategy for patients who need additional options after their cancer progresses.
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GSK Advances Global Phase III Development
The global Phase Ib findings, together with results from the Phase III ARTEMIS-008 study conducted in China by GSK’s licensing partner Hansoh Pharma, supported the selection of the 8 mg/kg dose for further investigation. In ARTEMIS-008, Ris-Rez reduced the risk of death by 54% compared with topotecan, with median overall survival of 18.5 months versus 10.3 months. GSK is evaluating the selected dose in the ongoing EMBOLD SCLC-301 global Phase III trial, which compares Ris-Rez with topotecan in patients with relapsed small cell lung cancer. The global development programme aims to establish whether the treatment can deliver meaningful clinical benefits across broader patient populations. The Phase Ib results are encouraging, but further evidence is needed to confirm response durability, long-term outcomes and safety. If subsequent trials demonstrate a favourable benefit-risk profile, Ris-Rez could become a potential future treatment option for patients with this difficult-to-treat cancer.
Source: GSK press release
