Drug Development, Setbacks

After billion-dollar drug deal, patient death and trial hold cripple Mersana’s shares

Just two years after inking a billion-dollar deal on its lead drug, Mersana’s cancer program has been put on a partial clinical hold by the FDA due to a patient death.

Anna Protopapas

The Cambridge, MA biotech reported Thursday that the patient death could be related to its drug XMT-1522. Under the hold, Mersana $MRSN can’t enroll new patients in the Phase I trial, which is testing the drug against breast, gastric, and non-small cell lung cancers. Patients already in the study, however, will continue taking XMT-1522.

The biotech — helmed by the high profile biotech vet and former Millennium chief Anna Protopapas — has been boasting a new and different kind of linker tech that is designed to create new cluster bombs that can be aimed at cancer. Current antibody-drug conjugates — or armed antibodies — can be limited to just a few therapies. Mersana believes it can link up with 12 to 15, creating ADCs to go after diseases that are currently beyond the reach.

Back in 2016, Takeda swooped in with a $1 billion deal to grab rights for XMT-1522 in ex-US territories. And just last year, the company went public on the promise of its pipeline. In the face of the clinical hold, however, investors are running. Mersana’s stock is down 43% — and counting — in pre-market trading.  In a statement, CEO Protopapas says there’s hope yet.

“Patient safety is our utmost concern,” Protopapas said. “Based on the totality of the data we have for XMT-1522, we believe that it continues to be a promising drug candidate in the solid tumor setting and we will be initiating the proper steps with the objective of resuming enrollment.”

The partial clinical hold does not affect the ongoing clinical development of Mersana’s other product candidate XMT-1536, currently in Phase 1 clinical trials for NaPi2b-expressing cancers.


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