Warfarin, the long-established gold standard therapy for stroke prevention in atrial fibrillation (AF) carries many significant inherent risks such as bleeding, leaving a very narrow therapeutic window. The launch of Pradaxa (dabigatran), an oral direct thrombin inhibitor (DTI) developed by the Boehringer Ingelheim (Germany) is expected to drastically change this clinical practice landscape. A second growth period is expected upon the anticipated launch of Eliquis (apixaban), an oral factor Xa inhibitor, by Pfizer (New York, NY, USA) and Bristol-Myers Squibb (New York, NY, USA) in late 2012 or early 2013.

Edoxaban, an oral factor Xa inhibitor, is also in the pipeline, and Xarelto (rivaroxaban), another oral factor Xa inhibitor that is approved for prophylaxis following orthopedic surgery, is awaiting approval for stroke prevention. These agents are poised to dominate the market for stroke prevention in AF, a very large and partially untapped market. They are also likely to grab substantial market share from the parenteral anticoagulants for prophylaxis of venous thromboembolism in orthopedic joint replacement surgery.

“Studies reveal that there are currently 2.7 million patients in the United States with atrial fibrillation; however, this may be an underestimation as the actual figure could be as high as four million,” said Deborah Toscano, a Frost & Sullivan Industry Analyst. “Lifelong anticoagulant therapy is critical for stroke prevention in these patients, resulting in substantial commercial opportunities.”

A fine line exists between the prevention of thrombosis and uncontrollable bleeding. Most often, bleeding issues or other safety concerns may not arise until late-stage clinical trials, or only in certain patient populations, after significant investments in drug development have been made. In addition, bleeding issues or other safety concerns may surface in the future, particularly if the bleeding risk of the real-world population differs from that studied in clinical trials, leading to black-box warnings or market withdrawal. One of the shortcomings, however, of oral anticoagulants is the lack of a strategy for reversal in case of emergency or uncontrolled bleeding.

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