Summit Therapeutics Inc. (NASDAQ: SMMT) announced today, 2025‑10‑20, the topline results of its Phase III HARMONi‑6 study, a randomized, double‑blind, head‑to‑head comparison of ivonescimab plus chemotherapy versus the PD‑1 inhibitor tislelizumab plus chemotherapy in first‑line advanced squamous non‑small cell lung cancer (NSCLC). The study, presented at the ESMO 2025 Congress in Berlin, showed a median progression‑free survival (PFS) of 11.14 months for the ivonescimab arm versus 6.90 months for the tislelizumab arm, with a hazard ratio of 0.60 (95% CI 0.46‑0.78; p<0.0001). Overall response rates were 75.9% for ivonescimab and 66.5% for tislelizumab, and duration of response was 11.20 months versus 8.38 months, respectively.
In subgroup analyses, the benefit was consistent across PD‑L1 expression levels: patients with PD‑L1 negative tumors had a hazard ratio of 0.55, while those with PD‑L1 positive tumors had a hazard ratio of 0.66. Safety data were manageable, with 3.4% of patients discontinuing due to treatment‑related adverse events in the ivonescimab arm versus 4.2% in the tislelizumab arm. Grade 3 or higher immune‑related events occurred in 9.0% of the ivonescimab group compared to 10.2% for tislelizumab, and grade 3+ VEGF‑related events were 7.5% versus 2.3%. Hemorrhage events of grade 3 or higher were 5 in the ivonescimab arm and 2 in the tislelizumab arm.
The HARMONi‑6 results are a pivotal milestone for Summit’s global registration strategy, as they represent the first Phase III evidence that a bispecific PD‑1/VEGF antibody can outperform a standard PD‑1 inhibitor plus chemotherapy in a hard‑to‑treat squamous NSCLC population. The significant PFS advantage, coupled with a favorable safety profile, strengthens Summit’s case for regulatory submissions in multiple territories and supports the broader expansion of ivonescimab across its Phase III pipeline.
Summit’s global Phase III program now includes three additional trials—HARMONi‑3, HARMONi‑7, and the recently launched HARMONi‑GI3 in colorectal cancer—each designed to evaluate ivonescimab in different first‑line settings. The positive HARMONi‑6 data reinforce Summit’s strategy to pursue registration in key markets and to position ivonescimab as a potential first‑line therapy for squamous NSCLC, thereby expanding the company’s addressable market and providing a critical data point for future regulatory and commercial decisions.
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