Portola's long-acting blood thinner misses main study goal

Natalie Grover : Portola Pharmaceuticals Inc said data showed its oral anticoagulant missed the main goal of preventing blood clots in acutely ill patients in a late-stage study.

The company's shares fell 30 percent to a two-year low of $20.00 in early trading.

Portola's betrixaban, designed for the prevention of venous thromboembolism (VTE), or blood clots, was tested against an injectable standard therapy in patients hospitalized for serious conditions such as heart failure, stroke, and pulmonary disease.

In the study, patients were divided into three groups. The first with a high risk of VTE, the second with high VTE risk and aged above 75, and the last included the overall population.

The trial was designed such that the primary efficacy analysis of the first group was to be done initially and had to be successful, before the other groups could be evaluated.

The first group narrowly missed the required threshhold, Portola said, but management went ahead and analyzed the remaining groups, which threw up data in favor of betrixaban.

On safety, there isn't much to argue about, but on efficacy the study has failed, Morgan Stanley analysts wrote, adding that without meeting the required threshold in the first group, all of the other analyses are exploratory.

"We are not yet ready to completely rule out betrixaban, but we acknowledge there is a long road ahead."

There was no statistical difference in major bleeding between the patients who were treated with betrixaban and those given the injectable, enoxaparin, in the 7,513-patient trial, the company said.

The number of fatal bleeds was balanced between the two therapies, but the number of brain hemorrhages was numerically lower in patients on betrixaban. Overall, a "positive net clinical benefit" with betrixaban was observed, Portola said.

Chief Executive Bill Lis said the totality of the efficacy and safety data in such a high-risk patient population was robust enough to support the submission of marketing application for the drug later this year.

Although more than half of all VTE events occur after the patient is discharged, no anticoagulant, including any of the marketed oral Factor Xa inhibitors, is approved for the prevention of VTE in both the hospital setting or after discharge, the company said.

Betrixaban is also designed to inhibit the activity of Factor Xa, a protein involved in the blood-clotting process. Factor Xa inhibitors include Xarelto from Johnson & Johnson and Bayer AG, and Eliquis, sold by Bristol-Myers Squibb Co and Pfizer Inc. (Reporting by Natalie Grover in Bengaluru; Editing by Maju Samuel)