Summit and Akeso's Ivonescimab Faces Long-Term Efficacy Questions as China Label Reveals PFS Degradation
On August 12, 2026, China's National Medical Products Administration (NMPA) approved the supplemental New Drug Application (sNDA) for ivonescimab (a PD-1/VEGF bispecific antibody co-developed by Akeso and Summit Therapeutics) in combination with chemotherapy for the first-line treatment of advanced squamous non-small cell lung cancer (sq-NSCLC). While this marks the third lung cancer approval for ivonescimab in China, the regulatory milestone was overshadowed by newly disclosed long-term data on the drug's label.
Buried within the NMPA-approved label is an updated analysis from the Phase III HARMONi-6 trial showing that the drug's progression-free survival (PFS) benefit degrades over time with longer patient follow-up. In the initial interim analysis, ivonescimab plus chemotherapy demonstrated a 40% reduction in the risk of disease progression or death compared to tislelizumab plus chemotherapy (hazard ratio of 0.60; 95% CI: 0.46-0.78; P<0.0001). However, with approximately seven months of additional patient follow-up, the PFS benefit was reduced to 28% (a hazard ratio of 0.72).
This degradation of efficacy has sparked pessimism among analysts, notably Leerink Partners, who are concerned that the ongoing global Phase III HARMONi-3 trial—intended to support an accelerated approval in the United States—may fail to show a substantial or durable PFS benefit. Consequently, analysts now expect a delayed U.S. launch of ivonescimab, pushing the projected timeline for squamous NSCLC from late 2027 to late 2029, and non-squamous NSCLC to late 2030. Following the disclosure, Summit's stock fell over 4% to close at $13.35 on August 14, 2026.
Quotes
"With about seven months of additional patient follow-up, ivonescimab produced a 28% reduction in the risk of disease progression or death, compared to a 40%..." — Summit and Akeso's PD-1xVEGF bispecific got a new approval in China. It came with an unwelcome surprise
"But as part of the approval, the NMPA posted some new data on the drug’s label showing degradation of progression free survival (PFS) in the Phase 3 HARMONi-6 trial that underpinned the regulatory clearance. The update spurred 'increased pessimism' from Leerink Partners, as Summit works to confirm the benefit of ivonescimab in global clinical trials to secure an FDA approval." — Summit, Akeso’s China approval celebration cut short as survival benefit degrades