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Mar 29, 2010
 |  BioCentury  |  Product Development

Betting on best, not first

Portola, Merck aim to be best in class in a growing field to replace warfarin

Portola Pharmaceuticals Inc. and partner Merck & Co. Inc. have reached the threshold of Phase III for betrixaban in the race to replace warfarin, but with three pharma compounds ahead of it, betrixaban will be selling a best-in-class story in the atrial fibrillation space.

In Phase IIb data presented at this month's American College of Cardiology meeting in Atlanta, Portola's once-daily, oral Factor Xa inhibitor showed improved safety over warfarin, which is associated with major bleeding, as well as unpredictable kinetics and interactions with other medications and even food. The study wasn't powered to show significance on efficacy endpoints.

Meanwhile, Boehringer Ingelheim GmbH presented a new subgroup analysis from a previously reported Phase III trial of its Pradaxa dabigatran etexilate, showing that the direct, oral thrombin inhibitor reduced the risk of stroke and systemic embolism compared with warfarin.

The BI product is already on the market outside the U.S. to treat venous thromboembolism, and other pharma tie-ups also have reached Phase III with compounds to prevent stroke in AF patients.

Portola's compound therefore is unlikely to be the first on the market going after warfarin. But the biotech hopes betrixaban will be best in class based on superior PK/PD characteristics in three areas: half-life, minimal renal excretion and the fact that it is not metabolized by CYP enzymes, which is often associated with drug-drug interactions.

Betrixaban rising

While it's too early to draw conclusions about betrixaban's efficacy relative to warfarin, the data presented at ACC show superior safety in a high-risk patient population.

In the international Phase IIb EXPLORE-Xa trial, 508 patients were randomized to receive a blinded daily dose of 40, 60 or 80 mg betrixaban or open-label, dose-adjusted warfarin. Patients either had non-valvular AF or atrial flutter (AFl) at enrollment, or had experienced at least one episode of AF or AFl in the previous 12 months, and all patients had at least one additional stroke risk factor. Patients were followed for a minimum of 3...

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