Contested Lung Cancer Drug Shows 34% Reduction in Death Risk in Late-Stage China Trial

Ivonescimab, a bispecific antibody developed by Chinese biotech Akeso and licensed to Summit Therapeutics for markets outside China, reduced the risk of death by 34% in patients with advanced squamous non-small cell lung cancer (NSCLC) when combined with chemotherapy, compared to the standard immunotherapy-chemotherapy combination [1][2]. The results, from the Phase III HARMONi-6 trial conducted entirely in China, were presented at the 2026 American Society of Clinical Oncology (ASCO) annual meeting — the first time a China-developed drug has earned the conference's plenary session in its six-decade history [3].

The presentation arrives at a moment of maximum tension. A previous global trial of the same drug missed its overall survival endpoint in Western patients [4], and the oncology community remains split on whether ivonescimab represents a genuine advance or a product of favorable trial design in a specific population.

What Ivonescimab Is and How It Works

Ivonescimab is a potential first-in-class bispecific antibody engineered using Akeso's proprietary Tetrabody technology. It simultaneously blocks PD-1, the immune checkpoint that Merck's Keytruda (pembrolizumab) targets, and VEGF, the angiogenesis factor targeted by Roche's Avastin (bevacizumab) [5]. By combining both mechanisms into a single molecule, the drug aims to both reactivate the immune system against tumors and starve them of blood supply.

The molecular design features four antigen-binding sites. In the presence of VEGF, the tetravalent structure accelerates ivonescimab's binding to PD-1, creating what Akeso describes as "cooperative binding" — potentially making the immune checkpoint blockade more potent when tumors are actively generating new blood vessels [5].

The HARMONi-6 Trial: Design and Results

HARMONi-6 enrolled 532 patients with previously untreated advanced (stage III or IV) squamous NSCLC across sites in China [1][2]. Patients were randomized to receive either ivonescimab plus platinum-based chemotherapy or tislelizumab (a PD-1 inhibitor marketed by BeiGene) plus the same chemotherapy backbone.

The key findings:

• Median overall survival: 28 months in the ivonescimab arm versus 24 months in the control arm [1]
• Hazard ratio for death: 0.66, meaning a 34% relative reduction in mortality risk [1][2]
• Statistical significance: The result met its pre-specified threshold [2]
• Approximately 63% of patients had centrally located squamous cell carcinoma, consistent with real-world Chinese patient populations [3]

The trial had previously met its co-primary endpoint of progression-free survival at an earlier interim analysis [6].

Source: ASCO 2026 / WCLC 2025 Presentations

Data as of May 31, 2026CSV

The Global Trial That Missed: HARMONi-2

The celebration around HARMONi-6 cannot be separated from the shadow of HARMONi-2, a global Phase III trial that tested ivonescimab in EGFR-mutant NSCLC patients whose disease had progressed after targeted therapy.

HARMONi-2 met one co-primary endpoint — a 48% reduction in disease progression or death risk — but missed the other: overall survival [4][7]. The geographic split was stark. Among Chinese participants, the hazard ratio for tumor progression was 0.55 (a 45% risk reduction). Among Western participants, it was 0.67 — a 33% reduction that failed to reach statistical significance [4].

Summit's stock fell 15% after the data were presented at the 2025 World Conference on Lung Cancer [7]. A subsequent updated analysis showed a slightly improved overall survival hazard ratio of 0.78 (nominal p = 0.0332), but this came after the pre-specified analysis had already missed [4].

The Skeptic's Case

The strongest scientific argument against extrapolating HARMONi-6's results to global populations rests on several observations:

Population differences. Squamous NSCLC in Chinese patients differs biologically from the same disease in Western populations. Smoking prevalence, environmental exposures, and genetic polymorphisms in drug-metabolizing enzymes all vary. The EGFR mutation rate in East Asian lung cancer patients runs 40-55%, versus 10-15% in Western patients [8]. While HARMONi-6 studied squamous histology (where EGFR mutations are less relevant), other genomic differences — including TP53 mutation patterns and tumor mutational burden — may influence immunotherapy response.

Comparator choice. HARMONi-6 used tislelizumab as its comparator, not pembrolizumab (Keytruda), which dominates in the United States and Europe. While tislelizumab is an established PD-1 inhibitor in China, some analysts have questioned whether it represents the true global standard of care [7].

China-only execution. The trial was sponsored, conducted, and enrolled entirely within China's clinical trial infrastructure. An observational study published in PLOS Medicine found that randomized trials in China between 2016 and 2021 sometimes used suboptimal control arms [9]. While HARMONi-6 used an active comparator (not placebo), the lack of geographic diversity raises questions about external validity.

The HARMONi-2 precedent. When ivonescimab was tested globally, the survival benefit did not reach significance in Western patients. Truist Securities analysts argued the East-West populations "look similar enough" to remain optimistic [4], but the data gap remains unresolved.

The Bull Case

Proponents counter with several points:

The 34% mortality reduction and 4-month median survival difference are clinically meaningful by any standard in advanced squamous NSCLC, a disease with a 5-year survival rate of approximately 9% in distant-stage patients [10]. Summit co-CEO Robert Duggan characterized the data as supporting "a very valuable business with a very valuable product that is in its early stages" [2].

The HARMONi-2 trial tested a different patient population (EGFR-mutant, post-TKI) in a different disease context. Checkpoint inhibitors generally struggle in EGFR-mutant NSCLC due to lower PD-L1 expression [4] — making HARMONi-2's miss less relevant to HARMONi-6's squamous population, where immunotherapy works well.

Additionally, the simultaneous publication in The Lancet subjects the data to peer review, providing an independent check on the trial's integrity [2].

Source: American Cancer Society, Cancer Statistics 2024

Data as of Jan 1, 2024CSV

Safety Profile

Ivonescimab's dual-targeting mechanism introduces VEGF-related toxicities on top of standard immunotherapy side effects. Based on available trial data:

• Hemorrhage: Grade 3 or higher bleeding events occurred in 2.6% of ivonescimab-treated patients versus 0.8% in the control arm [3]. The trial excluded patients with tumors invading major blood vessels or a history of significant hemoptysis.
• Proteinuria: Reported at 31.5% in earlier ivonescimab trials (HARMONi-2), versus not applicable for PD-1 monotherapy [5]
• Hypertension: 15.7% in ivonescimab-treated patients in prior studies [5]

These VEGF-related adverse events — particularly proteinuria and hypertension — are consistent with the known safety profile of anti-angiogenic therapies like bevacizumab. They may disproportionately affect older patients and those with pre-existing renal or cardiovascular conditions, populations that are heavily represented among lung cancer patients.

Treatment discontinuation rates for HARMONi-6 have not yet been fully disclosed in publicly available abstracts as of the ASCO presentation date.

Regulatory Pathways and Market Stakes

Ivonescimab's regulatory position varies by geography:

China (NMPA): Already approved. The drug received NMPA approval for first-line treatment of PD-L1-positive advanced NSCLC as monotherapy and for second-line EGFR-mutant NSCLC in combination with chemotherapy [11][12]. An application for the squamous NSCLC indication (based on HARMONi-6) has been accepted for review [13].

United States (FDA): The FDA accepted Summit's Biologics License Application (BLA) for ivonescimab plus chemotherapy in EGFR-mutant NSCLC post-TKI therapy, with a PDUFA target action date of November 14, 2026 [14]. This is based on HARMONi-2 data — the global trial that missed on OS. Over 14,000 U.S. patients per year are eligible in this setting [14]. For the broader squamous NSCLC indication, additional data or a U.S.-inclusive trial would likely be required.

Europe (EMA): No application has been publicly announced for European markets.

The financial stakes are substantial. Keytruda generated approximately $31.7 billion in global sales in 2025, with lung cancer accounting for 38.7% of revenue — roughly $12.3 billion [15]. Even capturing a fraction of this market would make ivonescimab a multi-billion-dollar drug. Analysts have described ivonescimab as a potential successor to Keytruda, which faces biosimilar competition as patents expire.

Who Benefits — And Who Doesn't

Based on available subgroup data, the patients most likely to benefit from ivonescimab are:

• Those with squamous NSCLC lacking actionable driver mutations (the HARMONi-6 population)
• PD-L1-positive patients (HARMONi-3 showed ivonescimab monotherapy superior to pembrolizumab)
• EGFR-mutant patients who have progressed on targeted therapy (HARMONi-2, with caveats about geographic performance)

Patients least likely to benefit based on current evidence include those in Western populations where the drug has not demonstrated statistically significant overall survival improvement, and potentially those with high bleeding risk given the VEGF-related hemorrhage signal.

Globally, approximately 2.5 million new lung cancer cases are diagnosed annually, with 1.8 million deaths [8]. NSCLC accounts for roughly 85% of cases. Many patients in low- and middle-income countries currently lack access to any immunotherapy, let alone combination regimens.

Access and Affordability

Specific per-patient pricing for ivonescimab has not been publicly disclosed in China or projected for the U.S. market. For context, Keytruda costs approximately $175,000-$200,000 per year in the United States. In China, where ivonescimab is already approved, the drug would be subject to National Healthcare Security Administration price negotiations for inclusion in the national reimbursement list.

The fact that the pivotal trial was conducted in China's healthcare system may actually facilitate faster access for Chinese patients. But for uninsured Americans or patients in lower-income countries, the barriers mirror those seen with other biologic oncology drugs: high list prices, limited patient assistance programs, and absence from WHO essential medicines lists until sufficient global data are generated.

Source: OpenAlex

Data as of Jan 1, 2026CSV

What Comes Next

The scientific community awaits several clarifications: full subgroup analyses from HARMONi-6, longer follow-up data, and most critically, whether Summit and Akeso will launch a confirmatory trial in Western populations for the squamous NSCLC indication. The FDA's November 2026 decision on the EGFR-mutant indication will also signal how regulators view China-generated data for U.S. approval.

The broader question is whether a drug that produced clear survival gains in Chinese patients — but uncertain results in a global context — can cross the regulatory and scientific threshold needed to change practice worldwide. The 34% mortality reduction is the strongest overall survival signal any bispecific antibody has produced in lung cancer. Whether it holds up under broader scrutiny will determine not just ivonescimab's fate, but the credibility of China's clinical trial infrastructure as a source of globally actionable evidence.