Merck returns promising blood clot drug to Portola

* 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: Quote, Profile, Research) 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

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

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

They include apixaban, being developed by Bristol-Myers
Squibb (BMY.N: Quote, Profile, Research) and Pfizer Inc (PFE.N: Quote, Profile, Research), and Xarelto from Johnson
& Johnson (JNJ.N: Quote, Profile, Research) and Bayer (BAYGn.DE: Quote, Profile, Research).

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
(Reporting by Ransdell Pierson; editing by John Wallace)

Merck returns promising blood clot drug to Portola