Partial clinical hold on ADC sinks Mersana shares

Mersana Therapeutics Inc. (NASDAQ:MRSN) lost $5.20 (32%) to $11.26 on July 19 after it said FDA placed a partial clinical hold on a Phase I trial of XMT-1522 following a "possibly drug-related" patient death. The event occurred at the seventh dose level of the dose-escalation study, which is evaluating the antibody-drug conjugate to treat advanced HER2-expressing breast, gastric or non-small cell lung cancer (NSCLC).

The hold suspends new enrollment in the trial. Patients already enrolled at ongoing dose levels may remain in the study. Mersana plans to meet with FDA to resolve the hold...