Jasper Therapeutics Shares Plunge 50% After Faulty Drug Batch Disrupts Multiple Clinical Trials

Jasper Therapeutics experienced a significant stock decline, with shares dropping over 50% following the discovery of a faulty batch of its investigational antibody therapy briquilimab used in a Phase Ib/IIa trial for chronic spontaneous urticaria (CSU). The compromised drug lot led to underwhelming efficacy results in affected patients, causing the company to halt related asthma and severe combined immunodeficiency studies and implement cost-cutting measures. The company is investigating the faulty batch, transitioning affected patients to new drug products, and plans to enroll additional patients to ensure robust data for the upcoming Phase IIb study, now expected to begin in mid-2026. Analysts have downgraded Jasper's stock to Neutral or Hold due to uncertainties stemming from the manufacturing issues, trial delays, and competitive pressures, although the drug showed promising efficacy in non-impacted patients. Cantor Fitzgerald specifically cited the uncertainty about clinical trial execution and development timelines as reasons for stepping back from the stock. Despite the setbacks, the drug demonstrated rapid onset and deep clinical response in patients treated with unaffected drug lots, supporting continued development focus on CSU.