By Colin Kellaher

Shares of Jasper Therapeutics plummeted in premarket trading Monday after the clinical-stage biotechnology company said issues with one lot of its lead drug candidate briquilimab was disrupting studies of the proposed antibody therapy.

Shares of the Redwood City, Calif., which closed Friday at $6.77, were recently down 71% at $1.98 premarket.

Jasper said the issues had affected results from a Phase 1b/2a study of briquilimab in adults with the skin condition chronic spontaneous urticaria, and that the same lot had been used to treat participants in a study evaluating the drug in asthma.

Jasper said it is halting the asthma study and pausing development of briquilimab in asthma in order to focus its resources on advancing the drug in chronic spontaneous urticaria.

The company said it is also halting development of briquilimab in the rare genetic disorder severe combined immunodeficiency and implementing a number of other cost-cutting measures, including a potential restructuring, in an effort to reduce cash burn and extend its runway.

Jasper said briquilimab has continued to show rapid onset, a deep clinical response and favorable safety in the study in chronic spontaneous urticaria, but that results from some multi-dose cohorts had been affected by issues with the single product lot.

Jasper said it is investigating the lot in question, and that it expects to have the results of the investigation in the coming weeks.

Jasper said it will transition the study patients who were initially dosed with drug from the lot in question to a new product and add more patients to the study to ensure a robust data set to inform a planned Phase 2b study.

The company said it expects data from the additional patients by the end of the year, and that it now expects to begin the Phase 2b study in mid-2026.

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

(END) Dow Jones Newswires

July 07, 2025 08:23 ET (12:23 GMT)

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