By Colin Kellaher

Mersana Therapeutics shares rose sharply after the biopharmaceutical company won a second Food and Drug Administration fast-track designation for a proposed treatment for breast cancer and reported positive early stage study results for the drug.

Mersana on Friday said the new designation covers the drug, XMT-1660, for the treatment of advanced or metastatic breast cancer in patients with human epidermal growth factor receptor 2 low or HER2-negative disease, including triple-negative breast cancer, who have received a prior topoisomerase-1 inhibitor antibody-drug conjugate.

Mersana shares, which closed Wednesday at $1.30, were recently up 22% at $1.59 in premarket trading.

The FDA's fast-track program is designed to facilitate the development and expedite the review of treatments for serious or potentially life-threatening illnesses with high unmet medical needs.

The agency previously granted fast-track designation to XMT-1660 for the treatment of adults with advanced or metastatic recurrent triple-negative breast cancer.

Mersana also reported positive initial data from the dose-escalation and backfill cohorts of a Phase 1 study of XMT-1660.

The Cambridge, Mass., company said it saw promising clinical activity in patients with triple-negative breast cancer previously treated with topoisomerase-1 inhibitor ADCs, adding that the drug was generally well tolerated.

Write to Colin Kellaher at colin.kellaher@wsj.com

(END) Dow Jones Newswires

January 10, 2025 06:45 ET (11:45 GMT)

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