Accipiter Bio adds $10.5M seed extension to fast-track AI-designed drugs

Accipiter Biosciences , a Seattle-based biotech using AI to engineer proteins, has raised a $10.5 million seed extension. The round was backed only by existing investors, including seed co-leads Flying Fish Partners and Takeda , alongside Columbus Venture Partners , Cercano Capital, Washington Research Foundation, Alexandria Investments, Pack Ventures, and Argonautic Ventures.

The startup emerged from stealth less than a year ago with $12.7 million and now wants to press its lead. "We could have stuck with the original plan and been just fine," said co-founder and chief executive officer Matthew Bick. "But we thought we'd rather capitalize on the progress we've made now and diversify our clinical portfolio."

Accipiter uses AI tools from the University of Washington's Institute for Protein Design, led by Nobel laureate David Baker, to build proteins that bind multiple cellular targets at once. The extra cash lets it advance three or four in-house drug programs into clinical trials, up from an original plan of one or two, focused on immunology and oncology.

The raise sits in the top 4% of all US health seed deals on record, a sample of nearly 11,000 rounds. Accipiter also holds a licensing deal with Pfizer worth an upfront payment plus more than $330 million in potential milestones and royalties, and a similar agreement with Gilead's Kite Pharma.

Bick, who previously worked at Baker-cofounded Neoleukin, knows AI drug design carries risk. Neoleukin's lead candidate underperformed in a Phase 1 trial before layoffs and a merger. "There's an impression with AI methods that you can just hit a button and you get your molecule out, but it's not that easy," he said.

Investor appetite for AI-driven drug discovery keeps building, but Accipiter's caution is a reminder that automation still meets the hard limits of biology. As Bick put it: "There's still protein intuition that comes into it."