* Merck says decision based on drug’s potential and cost
* Portola has no immediate comment
By Ransdell Pierson
NEW YORK, March 24 (Reuters) - Merck & Co (MRK.N) on Thursday said it is giving up rights to an experimental drug it once heralded as potentially the “best in class” of a promising new family of medicines to replace widely used blood clot treatment warfarin.
Merck said it was returning rights to the drug, called betrixaban, to privately held Portola Pharmaceuticals after determining the drug no longer fit its portfolio — based on its potential for success and costs to develop it.
“Portfolio prioritization is an ongoing process to ensure we’re pragmatic in what we’re pursuing,” said Merck spokesman Ian McConnell.
When drugmakers return drug rights to smaller companies, typically it is because data from clinical trials suggest safety problems or disappointing effectiveness of an experimental product.
Asked if anything went wrong with Portola’s drug, McConnell said, “Nothing that I’m aware of. It was a prioritization decision.”
A spokesman for Portola, a biotechnology company based in South San Francisco, California, said he was not immediately able to comment on the company’s future strategy for the medicine.
Researchers a year ago presented data that showed betrixaban was safe in a mid-stage study that compared it against widely used blood thinner warfarin in patients with an irregular heartbeat called atrial fibrillation.
Merck would have had to conduct a far larger and more costly late-stage trial to prove conclusively its safety and effectiveness in preventing stroke among such patients.
Even if the trial proved successful and betrixaban were approved several years from now, it would have to compete with a crop of similar drugs called Factor Xa inhibitors that are further along in trials and considered potential blockbuster products.
Betrixaban would also have to contend with a recently approved blood clot preventer called Pradaxa developed by German drugmaker Boehringer Ingelheim that prevents strokes in patients with atrial fibrillation. Its U.S. sales are rising quickly. (Reporting by Ransdell Pierson; editing by John Wallace)