Zolbetuximab plus chemotherapy in Japanese patients with claudin 18.2–positive gastric or gastroesophageal junction adenocarcinoma: a combined subgroup analysis of the phase 3 SPOTLIGHT and GLOW trials

BACKGROUND: Zolbetuximab is a monoclonal antibody targeting claudin 18 isoform 2 (CLDN18.2) approved for first-line treatment of CLDN18.2-positive, human epidermal growth factor receptor 2 (HER2)-negative, locally advanced (LA) unresectable or metastatic gastric or gastroesophageal junction (GEJ) adenocarcinoma. Here, we report efficacy and safety outcomes from the combined Japanese subgroup analysis of SPOTLIGHT and GLOW. METHODS: Global, double-blind, phase 3 SPOTLIGHT (NCT03504397) and GLOW (NCT03653507) trials investigated zolbetuximab plus chemotherapy versus placebo plus chemotherapy in patients with CLDN18.2-positive, HER2-negative, LA unresectable or metastatic gastric or GEJ adenocarcinoma. The primary endpoint in both trials was progression-free survival (PFS); overall survival (OS) was a key secondary endpoint. RESULTS: Of 1072 patients enrolled, 116 Japanese patients (SPOTLIGHT, n = 65; GLOW, n = 51) comprised the combined Japanese subgroup. The baseline characteristics of Japanese patients were generally similar to those of the overall study populations. In the combined Japanese subgroup, PFS was improved with zolbetuximab plus chemotherapy versus placebo plus chemotherapy (20.53 months [95% confidence interval (CI) 12.09-not estimable] versus 8.28 months [95% CI 6.57-9.07]). Median OS was 23.06 months (95% CI 16.49-25.49) in the zolbetuximab group versus 16.53 months (95% CI 10.38-18.33) in the placebo group. No new safety signals were observed. CONCLUSIONS: In Japanese patients, zolbetuximab plus chemotherapy improved PFS versus placebo plus chemotherapy and showed a numerical improvement in OS. These results support zolbetuximab plus chemotherapy as a potential new standard-of-care first-line option for Japanese patients with CLDN18.2-positive, HER2-negative, LA unresectable or metastatic gastric or GEJ adenocarcinoma.