Pharmacogenetic testing for warfarin sensitivity

Optimization of anticoagulation with warfarin for stroke prevention: pharmacogenetic considerations

Warfarin is a cornerstone of oral anticoagulation for stroke prevention. Anticoagulation with warfarin in patients with atrial fibrillation is over twice as effective in secondary prevention of stroke as any other tested alternatives, including all other antithrombotic drugs or surgical interventions. General belief is that warfarin is capable of preventing 20 ischemic strokes for every hemorrhagic one it causes. However, warfarin is one of the most feared agents as a result of its woeful safety profile and difficulties in maintaining the proper daily dose. Recent research in pharmacogenetics predominantly focused on elucidating the influence of individual genetic predispositions to administered warfarin. Although the incorporation of genotype information improves the accuracy of adequate dose prediction, an improvement in anticoagulation control or a reduction in hemorrhagic complications has not been yet convincingly demonstrated. It is clear that identifying an individual patient's risk for hemorrhage on warfarin will require more broad clinical and genetic studies. Future research focused on patients with stroke should concentrate on defining the possible differences, especially focusing on predicting bleeding events in general and intracranial hemorrhages in particular. The purpose of this review is to summarize the existing evidence about pharmacogenetics of warfarin in general, especially focusing on stroke prevention.

Treating MS: getting to know the two birds in the bush

Current therapies for immune-mediated diseases, such as rheumatoid arthritis and MS, could represent the proverbial bird in the hand - a known entity, yet limited in potential. Emerging biologic therapeutics for these diseases carry with them the potential for known as well as unknown adverse effects. Alemtuzumab, a biologic that depletes leukocytes, shows great promise for the treatment of MS. However, a significant number of patients develop autoimmunity after treatment, raising the level of caution for the use of this drug. In this issue of the JCI, Jones et al. describe a link between IL-21 levels and alemtuzumab-associated autoimmunity (see the related article beginning on page 2052). They show that proliferation of lymphocytes in those patients with autoimmunity is higher than in those without autoimmunity and suggest that the lymphopenia-driven proliferation of T cells, in combination with higher IL-21 levels, results in autoimmunity. This study helps inspire new enthusiasm for making a grab for the proverbial two birds in the bush - representing undiscovered therapies - with greater confidence.