CStone Pharmaceuticals and partner EQRx reported more data from the Phase III GEMSTONE-301 trial on Friday, saying that using sugemalimab as consolidation therapy prolonged progression-free survival (PFS) by a median 9 months in patients with Stage III non-small-cell lung cancer (NSCLC), versus 5.8 months for placebo. The results, top-lined in May, make sugemalimab the first PD-(L)1 monoclonal antibody to demonstrate a significant PFS benefit in this setting, according to the companies.
GEMSTONE-301 is "unique…in that it enrolled a highly heterogenous population of patients...reflective of everyday practice across a range of tumour pathologic subtypes, performance status and those treated with either sequential or concurrent chemoradiotherapy," noted Vincent Miller, physician-in-chief at EQRx. He said the findings, released ahead of presentation at the ongoing European Society for Medical Oncology (ESMO) congress, suggest sugemalimab may be able to treat a "broad population of patients."
The study, which is being conducted in China, included 381 patients with locally advanced/unresectable Stage III NSCLC, whose disease did not progress after concurrent or sequential chemoradiotherapy. Participants were randomised to receive sugemalimab, formerly known as CS1001, by intravenous infusions for up to 24 months, or placebo. The primary endpoint is PFS per blinded independent central review, with secondary goals evaluating overall survival (OS) and PFS as assessed by the investigators.
Results to be detailed at ESMO showed that for patients who received prior concurrent chemoradiotherapy, median PFS was 10.5 months for the sugemalimab group versus 6.4 months for placebo. Among those given prior sequential chemoradiotherapy, median PFS was 8.1 months and 4.1 months, respectively. CStone and EQRx also pointed to an "encouraging trend" in terms of survival, but OS data are still immature. They said median OS for sugemalimab was not reached, and was 24.1 months for placebo, with follow-up ongoing. No new safety signals were observed.
Earlier this month, the companies unveiled updated results at the World Conference on Lung Cancer (WCLC) from the Phase III GEMSTONE-302 study, which is testing sugemalimab in combination with chemotherapy as a first-line treatment for Stage IV NSCLC. The new findings showed that as of the March 2021 cut-off, sugemalimab plus chemotherapy was associated with significantly longer PFS of 9 months, compared to 4.9 months for placebo. Meanwhile, OS data are still immature here too, but preliminary median OS was 22.8 months in the sugemalimab arm versus 17.7 months for chemotherapy alone.
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