Mersana Therapeutics, Inc. (NASDAQ: MRSN) watched its shares plummeted Thursday. The company, a clinical-stage biopharmaceutical company focused on discovering and developing a pipeline of antibody-drug conjugates (ADCs) targeting cancers in areas of high unmet medical need, today announced that the U.S. Food and Drug Administration (FDA) has issued a partial clinical hold pausing new patient enrollment in UP-NEXT and UPGRADE-A, the company’s ongoing clinical trials of UpRi in platinum-sensitive ovarian cancer.
UPLIFT, Mersana’s ongoing clinical trial of UpRi in platinum-resistant ovarian cancer, completed enrollment in October 2022. Patients who are already enrolled in these trials may continue receiving UpRi. Mersana expects to lock its UPLIFT clinical trial database and disclose UPLIFT top-line data by early August.
The partial clinical hold follows a submission by Mersana of a recent aggregate safety report of all patients dosed with UpRi (approximately 560 patients) evaluating bleeding events. As noted in FDA guidance, aggregate analyses generally become more informative as a drug progresses through development and accumulates data. Detection of a clinically meaningful risk, particularly in single-arm clinical trials, typically requires a large safety database to detect differences in rates of adverse events compared to those that are expected in the population being studied.
In addition, Mersana plans to submit to the FDA the UPLIFT safety and efficacy data once available. The company plans to seek alignment with the FDA to lift the partial clinical hold and resume enrollment in UP-NEXT and UPGRADE-A.
MRSN shares collapsed $5.60, or 58.7%, to $3.95.