Mersana sheds 60% on FDA partial hold on trials for lead asset

• Mersana Therapeutics (NASDAQ:MRSN) lost ~60% pre-market Thursday after announcing that the FDA issued a partial clinical hold halting the enrollment in its UP-NEXT and UPGRADE-A trials for lead asset UpRi in platinum-sensitive ovarian cancer.
• The decision follows bleeding events reported from about 560 patients who received UpRi, an antibody-drug conjugate. The reason for the bleeding events remains under investigation, Mersana (MRSN) said.
• However, there were five (<1%) Grade 5 (fatal) bleeding events though most of the cases were low-grade. Patients in the UP-NEXT and UPGRADE-A trials can continue to receive the therapy.
• Despite the setback, the company intends to report topline data from its UPLIFT trial for UpRi in platinum-resistant ovarian cancer by early August.

More on Mersana

• Mersana jumps 18% on rival ImmunoGen's ovarian cancer treatment sales
• Mersana Therapeutics: Unrecognized Promise In UpRi's Cancer Fight