Ivonescimab Beats Keytruda on Overall Survival in HARMONi-2

Akeso, Summit Therapeutics’ China partner, said the Phase 3 HARMONi-2 trial met its key secondary endpoint of overall survival at a pre-specified interim analysis, giving ivonescimab a statistically significant and clinically meaningful survival advantage over Merck’s Keytruda in first-line PD-L1-positive non-small cell lung cancer. Summit (SMMT) shares closed at $14.60 on Wednesday and jumped about 14% to roughly $16.60 in Thursday trading.

The result matters because Keytruda is the standard of care and the top-selling drug in oncology. HARMONi-2 is a randomized, double-blind, registrational trial run in China that put ivonescimab head-to-head against pembrolizumab in patients whose tumors express PD-L1. It already met its primary endpoint of progression-free survival in May 2024, with a median of 11.14 months versus 5.82 months for pembrolizumab, making it the first randomized, double-blind Phase 3 trial to show a positive outcome against Keytruda in this setting. The new readout adds the survival endpoint on top of that progression-free benefit.

Ivonescimab is a PD-1/VEGF bispecific antibody that blocks the PD-1 immune checkpoint and traps VEGF, the protein that feeds tumor blood vessels, in a single molecule. It is already approved in China for this indication and two others. Akeso did not release the detailed OS numbers, saying it will present them at an upcoming medical meeting and publish them in a peer-reviewed journal.

For Summit, which holds ex-China rights to the drug, the caveat is familiar: HARMONi-2 is a China-only trial, and the FDA wants Western data before a clean review. Summit is running the global Phase 3 HARMONi-3 trial to confirm the benefit, and its nearest real catalyst remains the November 14 PDUFA date for ivonescimab in EGFR-mutant NSCLC.

The readout extends a long streak for the molecule. Ivonescimab has now logged five positive Phase 3 readouts, including the HARMONi-GI1 biliary tract cancer win in August, and Akeso’s chief executive said this is the fourth ivonescimab-based regimen to show a statistically significant benefit on both overall survival and progression-free survival.

What to watch next: the detailed HARMONi-2 OS data at the next medical conference, the HARMONi-3 global readout, and the November 14 PDUFA decision.

Source: Akeso press release

What It Means for the Trade

This is the single most important datapoint in the ivonescimab bull thesis, and it’s worth being precise about why. Plenty of drugs have beaten chemotherapy. A handful have beaten Keytruda-containing regimens on PFS in niche settings. But a statistically significant OS advantage head-to-head against pembrolizumab monotherapy in first-line PD-L1-positive NSCLC — the exact setting where Keytruda earned roughly half its ~$30 billion a year — is a different category of claim. If HARMONi-2’s final numbers hold up in Western populations, ivonescimab isn’t just another checkpoint competitor; it’s the first credible threat to the largest product in pharmaceutical history.

The market mechanics matter for sizing the move. SMMT is a ~$16 billion-ish company at these levels whose entire value rests on ex-China rights to one molecule. That means the stock trades on binary credible-pathway news, not fundamentals — hence the 14% pop on a topline line without numbers. Expect continued violent swings in both directions as each HARMONi readout, data presentation, and PDUFA lands. This is not a position for sizing you can’t afford to lose on a single slide deck.

The China caveat is the whole bear case, so treat it as the trade’s central variable. The FDA’s stated preference (and its track record under the oncology review modernization) is for multiregional clinical trials with U.S. site participation before approving China-only data — the long list of China-only readouts that stalled or required confirmatory Western trials (sintilimab’s ORIENT-11 rebuff being the canonical example) frames the risk. HARMONi-3, the global first-line squamous NSCLC trial versus pembrolizumab-plus-chemo, is therefore the value-creating event, and HARMONi-2 OS is the strongest de-risking datapoint HARMONi-3 could have asked for short of reading out itself.

Mechanism and Competitive Context

Why the molecule plausibly beats Keytruda: ivonescimab is a tetravalent PD-1/VEGF bispecific that blocks the checkpoint and traps VEGF isoforms in one molecule, with avidity-driven tumor retention. The mechanistic argument for synergy is that anti-VEGF activity normalizes tumor vasculature and improves immune infiltration, while PD-1 blockade removes the brake — and the “in one molecule” part delivers both at matched pharmacokinetics and tumor-to-plasma ratios no combination of separate antibodies easily replicates. China’s Akeso has also hypothesized a protein-binding (“super buffering”) effect unique to the tetravalent design that smooths VEGF inhibition.

The competitive frame is the interesting part. Akeso/Summit are attacking Keytruda head-on in first-line NSCLC — territory where every prior challenger (including Tecentriq, Imfinzi, and various combinations) settled for niche slices. Meanwhile Akeso already out-licensed ivonescimab-adjacent bispecifics (the PD-1/VEGF class it pioneered is now crowded with Meihua, Innovent, and others following in China). Summit’s moat is ex-China exclusivity, not mechanism exclusivity, so speed on HARMONi-3 enrollment and the November 14 EGFR-mutant PDUFA (the HARMONi/European study in post-TKI patients, where the FDA has actual Western data to review) are the moat-preserving events.

For Merck holders, this is a slow-motion threat, not an imminent one: Keytruda’s patent cliff lands 2028, and the subcutaneous Keytruda launch plus ADC-heavy pipeline (with Daiichi and LaNova deals) is the defensive playbook. But if ivonescimab or any PD-1/VEGF wins Western first-line NSCLC before 2030, the terminal-value assumptions underpinning MRK’s multiple compress.

Risks and What Could Go Wrong

Ranked honestly: (1) HARMONi-3 fails or underwhelms. China NSCLC populations differ meaningfully from Western ones — EGFR-mutation prevalence, smoking histories, hepatitis co-infections, and prior-line patterns all shift the frame, and the bear argument has always been that HARMONi-2’s China-only population flattered the drug. If the global trial misses or lands marginal, the stock reprices toward a single-indication China-partner story. (2) Numbers disappoint at presentation. “Statistically significant” without a hazard ratio leaves room for a modest effect that shrinks under scrutiny; the detailed OS curve, the median (if reached), and subgroup consistency (PD-L1 high vs low, squamous vs non-squamous) all get parsed line-by-line. (3) The November 14 PDUFA cuts the other way. A CRL or a demand for more Western data in EGFR-mutant disease would sap momentum going into HARMONi-3’s readout. (4) Bleeding risk as a class issue — anti-VEGF bleeding signals in squamous NSCLC have killed programs before (bevacizumab’s history in squamous disease), and HARMONi-3’s squamous population is exactly where that risk concentrates. Watch the safety slides as closely as the efficacy ones.

One thing not to worry about near-term: dilution or funding — Summit raised on strength and has runway through the pivotal readouts. The position-sizing discipline is the risk management here, not the balance sheet.