(Reuters) -BioCryst Pharmaceuticals said on Tuesday it would buy Astria Therapeutics in a cash-and-stock deal valued at about $700 million, as it looks to expand its portfolio of treatments for rare diseases.

The offer implies a per-share value of $13, a premium of about 54% over Astria’s last closing price. Its shares surged 35.1% to $11.02 before the bell.

Astria CEO Jill Milne would join BioCryst’s board after the deal is closed, which is expected in the first quarter of 2026.

(Reporting by Siddhi Mahatole in Bengaluru; Editing by Shilpi Majumdar)

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