ASCO26: Summit, Akeso claim OS victory for ivonescimab in pivotal Chinese study

ASCO26: Summit, Akeso claim OS victory for ivonescimab in pivotal Chinese study

Summit Therapeutics and partner Akeso reported a statistically significant 34% overall survival improvement for ivonescimab plus chemotherapy over tislelizumab plus chemotherapy in first-line NSCLC at ASCO26, sending Summit's stock surging and establishing the PD-1/VEGF bispecific as a credible threat to the dominant PD-1 franchise.

Key Takeaways

• Ivonescimab plus chemotherapy cut the risk of death by 34% versus tislelizumab (BeOne Medicine's PD-1 inhibitor) plus chemotherapy in the Phase III HARMONi-6 trial, crossing the pre-specified statistical significance threshold for overall survival in first-line NSCLC.
• The result marks the first time a PD-1/VEGF bispecific has demonstrated an OS advantage over a PD-1 inhibitor in this setting, validating Summit's core investment thesis for the asset it licensed from Akeso for ex-China rights.
• Summit's stock surged on the readout, reflecting investor conviction that ivonescimab can compete with pembrolizumab-based regimens that dominate the $20 billion-plus first-line NSCLC market.
• BeOne Medicine now faces a head-to-head OS loss for tislelizumab in a key indication, with potential consequences for formulary positioning and physician preference in China.
• Regulatory and partnership catalysts are imminent: Summit is expected to outline its ex-China regulatory pathway, while Akeso pursues label expansion in China on the back of this data and the earlier HARMONi-2 approval.

What happened at ASCO26?

Summit Therapeutics and Akeso reported final OS data from the Phase III HARMONi-6 trial at ASCO26, showing that ivonescimab combined with chemotherapy reduced the risk of death by 34% versus tislelizumab plus chemotherapy in patients with first-line non-small cell lung cancer. The trial met its primary endpoint with statistical significance, establishing ivonescimab as the first PD-1/VEGF bispecific antibody to demonstrate an OS benefit over an established PD-1 inhibitor backbone in this setting.

The study was conducted entirely in China, where both Akeso and BeOne Medicine maintain deep commercial infrastructure. Tislelizumab, marketed as Tevimbra outside China, is approved across multiple tumor types and has been central to BeOne Medicine's global expansion strategy. Using an active PD-1 comparator rather than placebo strengthened the clinical relevance of the result, though it also means Western regulators will need to carefully interpret the data when evaluating ivonescimab against pembrolizumab-based standards of care.

Ivonescimab's dual mechanism — simultaneously blocking PD-1 immune checkpoint signaling and VEGF-mediated angiogenesis — has been the foundational thesis behind Summit's $500 million-plus bet on the asset. The company licensed ex-China commercialization rights from Akeso and has positioned the drug as a potential best-in-class challenger to pembrolizumab in first-line NSCLC, the single largest oncology indication globally.

Why does this matter for the PD-1 franchise?

The HARMONi-6 result cracks a narrative that has persisted for years: no next-generation PD-1 combination has cleanly beaten a PD-1 inhibitor on overall survival in a randomized first-line NSCLC trial. Ivonescimab's 34% OS improvement over tislelizumab is the first Phase III proof point that a bispecific approach can deliver meaningful survival gains beyond what single-agent PD-1 blockade achieves with chemotherapy.

For Merck, the data add another competitive variable to monitor. Keytruda's dominance in first-line NSCLC has been built on a combination of registration-trial breadth, real-world evidence, and entrenched formulary access. Ivonescimab does not directly challenge Keytruda on its own trial data yet — the comparator was tislelizumab, not pembrolizumab — but the magnitude of benefit raises the bar for any future head-to-head comparisons and gives Summit a compelling data package to bring to regulators and potential partners.

BeOne Medicine faces the most immediate competitive pressure. Tislelizumab has been the company's flagship asset and a cornerstone of its ambition to build a global oncology franchise. A head-to-head OS deficit in first-line NSCLC could influence prescribing patterns in China and complicate BeOne's positioning in markets where both drugs may eventually compete.

What does this mean for Summit's ex-China strategy?

Summit Therapeutics now has Phase III OS data to anchor regulatory discussions with the FDA and EMA. The company has signaled plans to pursue ex-China development, and the HARMONi-6 result provides the kind of statistically significant survival data that regulators expect to see before considering accelerated or standard approval pathways.

Business development teams should watch for two near-term catalysts. First, Summit is expected to request a Type B meeting with the FDA to discuss trial design for a Western patient population — likely a head-to-head study against pembrolizumab-based regimens. Second, the company may seek a co-commercialization or distribution partner to fund the substantial costs of global development, and the HARMONi-6 data materially strengthen Summit's negotiating position in any such discussions.

For investors, the 34% OS improvement validates the bispecific thesis and differentiates ivonescimab from other PD-1/VEGF combinations that have struggled to show clear superiority over PD-1 monotherapy. Summit's market capitalization has been largely predicated on ivonescimab's ability to compete with Keytruda, and this result provides the strongest clinical evidence yet that the drug can deliver on that promise.

What happens next?

Regulatory strategy will be the next major watchpoint. Akeso has already secured NMPA approval for ivonescimab in a separate indication based on the HARMONi-2 trial, which showed superiority over pembrolizumab. The HARMONi-6 data could support label expansion in first-line NSCLC in China, potentially broadening the drug's addressable patient population significantly.

On the ex-China front, Summit's timeline for an FDA meeting request and trial initiation will be closely scrutinized by analysts. The company will need to address questions about generalizability — the HARMONi-6 population was entirely Chinese — and whether the OS benefit holds in more diverse, Western patient cohorts with different PD-L1 expression profiles and standard-of-care backbones.

BeOne Medicine's response will also merit attention. The company may invest in additional tislelizumab combination studies to shore up its competitive position, or it may shift commercial emphasis to indications where tislelizumab has stronger data. Either way, the HARMONi-6 result reshapes the competitive calculus in first-line NSCLC and establishes ivonescimab as a force that the entire PD-1 ecosystem must now account for.

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