Alpine Immune Sciences CEO Mitchell Gold in 2017. (AIS Photo)

Boston-based biotech company Vertex Pharmaceuticals agreed to acquire Seattle-based Alpine Immune Sciences for $65 per share, totaling about $4.9 billion in cash, a 38% premium over Alpine’s closing price on Wednesday afternoon.

The premium would have been higher, around 67%, based on Alpine’s closing price on Tuesday. However, the company’s stock jumped 21% in regular trading Wednesday after Bloomberg News reported it was considering a sale.

Alpine develops immunotherapies to address cancer, kidney disease, and other serious autoimmune and inflammatory conditions by engineering proteins that influence the body’s immune response.

“This is a historic moment for Alpine, for our employees, and most importantly, for patients who may benefit from our pipeline of products,” said Mitchell Gold, the company’s CEO, on a call with investors.

He specifically referenced povetacicept (ALPN-303), which is designed to treat autoimmune and inflammatory diseases, and is slated to enter Stage 3 clinical trials in the second half of this year.

Gold was previously CEO of biotech startup Dendreon and founder of health-care investment firm Alpine BioVentures.

The deal is the latest in a string of large acquisitions for biotech companies based in the Seattle region.

The acquisition of Alpine by Vertex, announced Wednesday afternoon, is scheduled to close in the second quarter. The boards of both companies have unanimously approved the transaction, the companies said.

Alpine had 142 employees as of the end of 2023, including 113 employees in R&D and 29 in general and administrative roles, according to a March 20 SEC filing.

The company launched in 2015 and went public in 2017 through a merger with publicly traded pharmaceutical company Nivalis. Alpine has raised additional funds including $91 million in 2021 through a private placement from investors including Seattle-based Frazier Healthcare Partners.

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