Merck signs deal with Infinimmune to search for new antibodies in human immune memory, with total payouts reaching $838 million

Merck signs deal with Infinimmune to search for new antibodies in human immune memory, with total payouts reaching $838 million

On March 31, Merck and California-based Infinimmune announced a deal to discover therapeutic antibodies against several as-yet undisclosed targets. Infinimmune screens memory B cells, the immune system cells that retain the body’s successful responses to past threats, and extracts paired antibody chains from them. Merck gets exclusive rights to candidates found through this system; the upfront payment was not disclosed, and the total milestone ceiling is about $838 million.

The central question in this story is what exactly Merck decided to buy.

Infinimmune turns human immune experience into a search engine. The company assembles fully paired heavy and light antibody chains from memory B cells, the two parts of a single molecule that together determine what it binds to and how it works. The company says on its website that the platform can screen up to 300 million B cells across 350+ targets. For therapeutic antibody discovery, that is a critical detail: when a researcher sees only half of the pair, the full working construct is lost.

Next comes GLIMPSE, Infinimmune’s antibody language model, which the company trained last year on human sequences. The model helps refine antibodies that have already been found: increasing target affinity, removing properties that complicate development, and improving the odds that a molecule can be manufactured reliably as a drug. Here, AI functions as part of the production pipeline.

Merck is buying a systematic way to pull rare molecules out of existing human biology. At the center of the deal is a machine for finding the next drugs. The same logic was already visible in Chugai’s deal with Gero for an anti-aging AI platform: big pharma is increasingly buying systems that can deliver new molecules at scale.

Merck has a pragmatic motive. BioPharma Dive reports that the company has been expanding its biologics business in recent years ahead of the future patent expiry of Keytruda, its flagship cancer drug. In that situation, platforms that can consistently generate new candidates become especially valuable.

The same report says talks between Merck and Infinimmune began back in December 2024, and that Infinimmune itself grew out of a team of former 10x Genomics employees. The negotiations lasted more than a year. That timeframe alone does not prove the quality of the platform, but it does show that Merck evaluated it for a long time before committing to a multi-target deal.

There is still no independent evidence that this platform already outperforms competitors on clinical outcomes. For now, what exists is a corporate release, secondary coverage, and a promise of speed. But it is already clear that some of the value in biomedicine is shifting from the individual molecule to the systems that can produce such molecules repeatedly.