I had the privilege of attending last week's annual meeting of the American Society of Hematology, held in San Francisco. It was one of the most interesting meetings I have ever attended. I paid particularly close attention to the abstracts and educational symposia in the field of thrombosis and anticoagulant therapies.
What interested me the most is the emergence of new oral anticoagulants. These drugs fall into the category of direct thrombin inhibitors (DTIs) and factor Xa inhibitors.
The ideal anticoagulant drug would be one with a wide therapeutic index, oral administration, once a day administration, easy reversibility and availability of an effective antidote, short half life, lack of need for laboratory monitoring and reasonable cost.
While unfractionated heparin, low molecular weight heparins and warfarin in their own respects fulfill some of the above characteristics, none of them are by any means ideal and they all fall far short of fulfilling all of the above criteria.
The drugs to be on the watch for in my opinion are going to be rivaroxaban (Xarelto-Bayer), apixaban (Pfizer and BMS) and dabigatran (Pradaxa-Boehringer Ingelheim) which come much closer to being the "ideal" drug. The latter drug is a DTI that has been shown to be as effective and safe as enoxaparin (Lovenox) in reducing VTE after orthopedic surgery, while the first two are factor Xa inhibitors. Rivaroxaban has received approval in Canada and the EU for prevention of VTE in patients undergoing elective total hip or total knee replacement surgery. Apixaban failed to meet pre-specified criteria of non-inferiority in a study comparing it to enoxaparin in post-op patients but was numerically very similar in efficacy and statistically superior in terms of bleeding complications.
Also to watch for are potential antidote drugs, in particular one that is in development from Portola Pharmaceuticals (S. San Franciso), which is directed against the Xa inhibitors.
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