CStone Pharmaceuticals announced that the GEMSTONE-304 study, in which sugemalimab in combination with chemotherapy is used as first-line treatment of unresectable locally advanced, recurrent, or metastatic esophageal squamous cell carcinoma (ESCC), has met its primary endpoints. Sugemalimab in combination with chemotherapy demonstrated a statistically significant and clinically meaningful improvement in Blinded Independent Central Review (BICR)-assessed progression-free survival (PFS) and overall survival (OS) compared with placebo in combination with chemotherapy. The safety profile was consistent with previous findings across the studies in additional diseases with sugemalimab and no new safety signal was observed.

The GEMSTONE-304 study is a randomized, double-blind, multi-center, placebo-controlled phase 3 registrational clinical trial designed to evaluate the efficacy and safety of sugemalimab in combination with 5-fluorouracil plus cisplatin (FP) as first-line treatment in patients with unresectable locally advanced, recurrent, or metastatic ESCC. The primary endpoints are BICR-assessed PFS and OS, and secondary endpoints include investigator-assessed PFS, BICR and investigator-assessed objective response rate (ORR) and duration of response (DoR). In a phase Ib trial in this population, sugemalimab in combination with FP achieved an ORR of 67.6% (25/37) and a disease control rate (DCR) of 89.2%, along with durable responses as first-line treatment of ESCC patients.

Based on the top-line data of GEMSTONE-304 study, CStone plans to submit a supplemental new drug application on this new indication to the National Medical Products Administration (NMPA) of China in the near future.