German drug company Boehringer Ingelheim announced December 12 that it had to stop a Phase 2 clinical trial of Pradaxa in patients with mechanical heart valves. The drug was approved in the U.S. by the Food and Drug Administration (FDA) as an anticoagulant to treat an irregular heartbeat also known as atrial fibrillation (AF).
Use in patients recovering from heart valve surgery is considered off-label use for which the drug is not approved.
Artificial heart valves
Forbes reports the RE-ALIGN trial was to be conducted over a 12-week period on 400 patients that compared dabigatran (Pradaxa) to its closest competitor Coumadin (warfarin). The randomized trial first looked at patients in the hospital then three months post-surgery. This was to be the first trial to consider the alternative to the old standby Coumadin. Boehringer claimed early on that plasma levels of dabigatran were lower than projected in patients and there was an imbalance in reports of strokes. At that point the trial was set to continue.
But when two of the mechanical heart valve patients switched from Pradaxa to Coumadin they developed thrombosis. That’s when the trial was halted. The theory is the proper dose for these patients is yet to be found and more clinical trials are necessary before establishing safety and efficacy in mechanical valve patients.
Pradaxa is approved in Europe for prevention of venous thromboembolism (VTE), a blood clot that forms in a vein following a knee or hip replacement, but not in the U.S. The nearest competitor Xarelto has been approved for VTE in Europe and the U.S. Boehringer says even with this outcome, Pradaxa has proven effective in preventing strokes in patients with non-valvular atrial fibrillation as well as VTE after hip or knee replacement surgery.