CStone Pharmaceuticals announced that the National Medical Products Administration (NMPA) of China has approved the supplemental biologics license application (sBLA) for sugemalimab (Cejemly®) in combination with fluoropyrimidine- and platinum-containing chemotherapy as a first-line treatment for unresectable locally advanced or metastatic gastric or gastroesophageal junction (G/GEJ) adenocarcinoma with a PD-L1 expression (Combined Positive Score [CPS] =5). Sugemalimab becomes the world's first PD-L1 monoclonal antibody approved for this indication. This sBLA of sugemalimab was approved based on the data from the GEMSTONE-303 study.

It is a multi-center, randomized, double-blinded, placebo-controlled Phase 3 registrational clinical trial, designed to evaluate the efficacy and safety of sugemalimab plus capecitabine and oxaliplatin (CAPOX) as a first-line treatment in patients with unresectable locally advanced or metastatic G/GEJ adenocarcinoma with PD-L1 expression =5%. The co-primary endpoints were investigator-assessed PFS and OS. Secondary endpoints include blinded independent central review (BICR)-assessed PFS, investigator-assessed objective response rate (ORR), and duration of response (DoR).

This study has met its pre-specified co-primary endpoints. The results from this Phase 3 trial, GEMSTONE-303, have been accepted as a late-breaking abstract (LBA) and showcased in an oral presentation session at the European Society for Medical Oncology (ESMO) Congress 2023. The data presented at the ESMO Congress 2023 is based on the final analyses of PFS as of August 6, 2022, and OS as of July 9, 2023.

The results show that the GEMSTONE-303 study has met its pre-specified co-primary endpoints. In patients with PD-L1 expression=5%, sugemalimab in combination with chemotherapy has demonstrated statistically significant and clinically meaningful improvement in PFS and OS, compared with placebo plus chemotherapy. Key findings are as follows: The investigator-assessed median PFS was 7.6 months in the sugemalimab treatment group compared with 6.1 months in the placebo group, with a hazard ratio (HR) of 0.66 (95% CI, 0.54-0.81), P<0.0001.

Median OS was 15.6 months in the sugemalimab treatment group versus 12.6 months in the placebo group, with an HR of 0.75 (95% CI, 0.61-0.92), P=0.0060. Subgroup analyses has demonstrated clinical benefits across all pre-defined subgroups, including PD-L1 expression status. Sugemalimab treatment resulted in an investigator-assessed ORR of 68.6% compared with 52.7% in the placebo group, with a median DoR of 6.9 months versus 4.6 months.

Sugemalimab in combination with chemotherapy appears safe and tolerable, with no new safety signal identified.