Merck halts study of the billion-dollar cancer drug vintafolide

Merck ($MRK) and partner Endocyte ($ECYT) have stopped a late-stage study of the ovarian cancer-treating vintafolide on the advice of a data safety monitoring board, saying the much-hyped drug failed to move the needle on progression-free survival.

Reviewing vintafolide's Phase III results in an interim analysis, the board recommended that Merck halt its trial for futility, the company said, casting serious doubts on a drug that had polarized analysts and investors. Vintafolide, which Merck picked up in a licensing deal worth up to $1 billion, is a targeted treatment for platinum-resistant ovarian cancer, and its promising Phase II performance in that indication was enough to sway European regulators to recommend conditional approval back in March.

But the drug's Phase III stumble has wiped away much of the cheer tied to that regulatory win, a story borne out in Endocyte's share price: The biotech soared more than 175% on the European Medicines Agency's favor, but it has now fallen roughly 60% in premarket trading after Friday's announcement.

Endocyte is "surprised and disappointed" by vintafolide's failure, CEO Ron Ellis said in a statement. "We are reviewing and validating the data in collaboration with Merck in order to gain a better understanding of the interim trial results and make our formal decision regarding the execution of the trial," Ellis said.

Merck R&D chief Roger Perlmutter

In tandem with the ovarian cancer program, Merck and Endocyte are developing vintafolide for non-small cell lung cancer, in March touting positive Phase IIb results in which the drug hit its primary endpoint of PFS. Merck never publicly committed to a Phase III trial in that indication, and it remains to be seen whether vintafolide's ovarian cancer futility will change the company's plans. Merck didn't respond to a request for comment on Friday.

In any case, the latest news is a major setback for Merck and R&D chief Roger Perlmutter as they try to right the ship of research. Vintafolide, brought in by the since-departed Peter Kim, was the second prong of Merck's late-stage cancer pipeline, following the promising immunotherapy MK-3475. 

- read Merck's statement
- here's Endocyte's release