Akeso's Lung Cancer Drug Beats Keytruda in Phase III Trial

Akeso's ivonescimab outperformed MSD's Keytruda in a Phase III lung cancer trial in China, adding to its recent discovery that it slowed disease progression.

The company said the benefit was statistically significant but did not disclose its size, including the reduction in death risk or median overall survival in either treatment group. Detailed results will be presented at an upcoming medical conference and published in a peer-reviewed journal.

MSD's biggest seller, Keytruda, earned US$31.6 billion in 2025, nearly half its revenue. Even though the Chinese trial only addresses one lung cancer setting in Keytruda's business, its commercial weight raises the stakes for competitors.

The finding came from a prespecified interim analysis of HARMONi-2, which met its key secondary endpoint of overall survival, according to Akeso. Progression-free survival was the trial's primary endpoint.

The randomized, double-blind study included 398 patients from 55 Chinese hospitals. It compared ivonescimab to Keytruda (pembrolizumab) as initial treatment for locally advanced or metastatic non-small cell lung cancer with positive PD-L1 expression. Patients with EGFR or ALK mutations were excluded.

Earlier Lancet results showed median progression-free survival of 11.1 months for ivonescimab and 5.8 months for pembrolizumab. That measure tracks the time before cancer worsens or a patient dies, not months of life. The latest study examines patient longevity.

"These results further reinforce the clinical value of ivonescimab in the treatment of lung cancer," said Xia Yu, Akeso's founder, chairwoman and chief executive.

The result follows an earlier survival benefit in HARMONi-6, another China-based trial, which compared ivonescimab plus chemotherapy with tislelizumab plus chemotherapy in advanced squamous lung cancer. HARMONi-2 instead tested ivonescimab directly against Keytruda without chemotherapy in either group.

This bispecific antibody targets PD-1, which suppresses the immune response to cancer, and VEGF, which promotes blood vessel growth that supports tumors. Pembrolizumab targets PD-1 only. One drug inhibits the growth of blood vessels that support tumors and treats the immune system.

The earlier HARMONi-2 findings showed a safety trade-off. Compared to 16 percent of pembrolizumab patients, 29 percent of ivonescimab patients had grade 3 or higher adverse events. Akeso failed to update safety figures in its latest announcement. Treatment decisions will depend on the survival benefit and side effects.

In China, ivonescimab has been approved for the HARMONi-2 indication since April 2025, so the findings could support uptake of an already marketed treatment. For Akeso and its overseas partner Summit Therapeutics, they also add clinical evidence to support efforts to compete internationally.

But HARMONi-2 was conducted entirely in China. Summit is conducting HARMONi-7, an international Phase III trial comparing the two drugs as standalone treatments in patients with high PD-L1 expression, a narrower population than HARMONi-2. Ivonescimab remains unapproved in the United States and Europe, according to Summit's September announcement.

The commercial question is how much of that clinical progress can translate into prescriptions and sales. Detailed survival results, international trial evidence, and pricing and reimbursement will help determine how effectively ivonescimab can compete with MSD's established treatment.