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12:00 AM
Apr 25, 2011
 |  BioCentury  |  Product Development

Still Banking on the Best

Losing Merck: Portola to run anticoagulant Phase III in smaller indication

Merck & Co. Inc. isn't saying why it handed betrixaban back to Portola Pharmaceuticals Inc., but the biotech still believes the oral Factor Xa inhibitor has best-in-class potential. Portola thus plans to move the compound into Phase III testing itself, but in a smaller indication than it had hoped to pursue with Merck.

Betrixaban belongs to a new wave of anticoagulants designed to block one of two individual coagulation factors: either thrombin or Factor Xa. These compounds are intended to replace warfarin, which is widely used but carries a risk of major bleeding and has complicated dosing, unpredictable kinetics and interactions with many drugs and even food.

In 2009, Merck paid $50 million up front for worldwide rights to betrixaban. The molecule had completed a Phase II trial to prevent venous thromboembolism (VTE) and was in a Phase IIb trial to prevent stroke in atrial fibrillation (AF) patients (seeBioCentury, July 20, 2009).

Last year, the partners reported results from the Phase IIb EXPLORE-Xa trial in 508 patients with AF. Betrixaban met the primary endpoint of time to occurrence of major or clinically relevant non-major bleeds(see BioCentury, March 29, 2010).

The 40 mg once-daily betrixaban dose significantly reduced the incidence of major or clinically relevant non-major bleeding vs. warfarin (0.8% vs. 5.5%, p=0.035). The 60 and 80 mg betrixaban arms were similar to warfarin.

The trial was not powered to show efficacy on cardiovascular outcomes. One stroke was recorded in each of the betrixaban 60 and 80 mg groups, and one death was recorded in each of the betrixaban 40 mg and warfarin groups. There were no myocardial infarctions or other systemic emboli in the trial.

Looking to stand out

While it is too early to compare betrixaban's efficacy to other anticoagulants, its...

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