June 15 (Reuters) - Mersana Therapeutics (MRSN.O) said on Thursday the U.S. Food and Drug Administration (FDA) had paused enrollment in two studies of its ovarian cancer drug after five deaths in bleeding-related events, sending shares of the company tumbling. Mersana said the cause of the bleeding events was under investigation, but patients who are already enrolled in the studies will continue to receive the treatment. Mersana said it expects the FDA to ask for a comprehensive assessment of the safety data of upifitamab rilsodotin (UpRi), the company's lead drug. "Work is now underway to compile further analyses that may inform FDA," Mersana CEO Anna Protopapas said. UpRi is also being tested in another ovarian cancer study, which has already completed enrollment, and data from it is expected in August.

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Persons: Mersana, David Nierengarten, Anna Protopapas, UpRi, Khushi, Savio D'Souza, Shinjini Organizations: Mersana Therapeutics, U.S . Food, Drug Administration, Wedbush Securities, FDA, Thomson Locations: Bengaluru