Regeneron backs $75M series A for antibody upstart Infinimmune

Biotech Regeneron backs $75M series A for antibody upstart Infinimmune By Darren Incorvaia Aug 11, 2026 8:00am Infinimmune Regeneron Pharmaceuticals Regeneron Ventures eczema Infinimmune has amassed further fuel to power its antibody discovery engine, netting a $75 million series A headlined by Regeneron’s venture arm. Regeneron Ventures co-led the Bay Area biotech’s fundraise alongside Playground Global, with other newcomers like RA Capital Management, Forge Life Science Partners and Goldcrest Capital also pitching in. Existing investors came back for the series A too, including Infinimmune’s partner, Merck & Co.

“As a company working in eczema, we're thrilled to have Regeneron Ventures co-leading our financing,” Infinimmune co-founder and CEO Wyatt McDonnell, Ph.D., told Fierce. By backing Infinimmune, Regeneron is financing the development of a potential competitor to its inflammation blockbuster Dupixent. Dupixent targets both interleukin-4 and interleukin-13, and the latter is also the focus of one of Infinimmune’s lead antibodies.

“With IFX-201, we have an opportunity to improve on a clinically validated mechanism,” McDonnell explained. Many eczema patients, he noted, may stop responding to one drug only to then see an effect when switching to another, even if both drugs hit the same target. “We're looking at this as an opportunity to develop complementary molecules for a disease that is really complex, that's very multifactorial,” McDonnell explained.

“We're going after a pair of targets that play different roles in that core disease biology.” Unlike IFX-201, the other Infinimmune antibody that is nearing the clinic, IFX-101, is designed to hit a target that has never been successfully drugged before. “With [interleukin]-22, we’re pursuing a really important and underestimated component of eczema biology for which there is currently no approved biologic,” McDonnell said. Both of these antibodies, discovered through Infinimmune’s human B cell-based platform, are due to enter phase 1 testing next year, the CEO told Fierce.

The new cash should last the biotech “through to meaningful value inflection points,” McDonnell added. “It obviously would not be very good to just run out of cash the second you complete a pair of healthy volunteer studies,” he said. “We planned for substantially more than that.” Related Merck enlists antibody hunter Infinimmune for $838M biobucks pact Behind IFX-101 and IFX-201 sit other earlier-stage antibodies targeting A Proliferation-Inducing Ligand (APRIL) and interleukin-17F for IgA nephropathy and ulcerative colitis, respectively, as well as another asset currently shrouded in mystery.

McDonnell also thinks there’s room for Infinimmune to strike one or two more Big Pharma partnerships of the same scale as the March Merck pact that’s valued at as much as $838 million. The key is for a potential partner to be motivated to get high-quality, innovative new medicines “out the door and into the clinic quickly,” he said. “We're not a platform company—we're a therapeutics company with a really productive platform,” McDonnell told Fierce.

“That's the value that we're focused on realizing for patients.” Infinimmune Regeneron Pharmaceuticals Regeneron Ventures eczema atopic dermatitis antibodies Fundraising biotech venture capital Venture Capital Biotech