Icosavax CEO Adam Simpson. (Icosavax Photo)

Seattle-based Icosavax, a spin-out from the University of Washington’s Institute for Protein Design, will be acquired by biotech giant AstraZeneca for up to $1.1 billion.

The pending acquisition, announced Tuesday, values Icosavax at about $838 million, a 43% premium to its closing price on Monday.

Founded in 2017, Icosavax is developing vaccines that resemble naturally occurring viruses. Its lead product targets respiratory viruses.

The company raised more than $150 million from private investors before going public in 2021. Its stock has fallen more than 30% since then, though it has nearly doubled in 2023.

Icosavax shares were up more than 40% on Tuesday following the news.

“We are pleased to announce the proposed acquisition of Icosavax by AstraZeneca as we believe it offers the opportunity to accelerate, and expand access to, our potential first-in-class combination vaccine for older adults at risk from RSV and hMPV,” Icosavax CEO and co-founder Adam Simpson said in a statement. “We look forward to combining our skills and expertise in advancing the development of IVX-A12, with AstraZeneca’s decades of experience in RSV, resources, and capabilities in late-stage development.”

The company’s virus-like particle technology was invented at the Institute for Protein Design by Neil King, a scientific co-founder of Icosavax along with IPD head David Baker.

Simpson formerly led another IPD spinout, PvP Biologics, which sold to the pharmaceutical company Takeda.

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