Causal role for JAK2 V617F in thrombosis

The article by Takahashi and colleagues is impactful because it helps validate the decision of both sets of response criteria that focus on peripheral blood analysis for the assessment of the JAK2 V617F allele burden. The quality demonstration in a high number of samples across MPNs demonstrating the interchangeable nature of measuring alleleburden in blood and bone marrow will be very helpful in clinical trials moving forward, as well as potentially clinical practice as we further validate the impact that reduction in allele burden is helpful. In addition, it helps validate the practice even today of monitoring the JAK2 V617F allele burden in patients post stem cell transplantation in terms of monitoring for both response and relapse. As the current clinical trials of MPNs are evolving from single agent to combination strategies, the ability to dynamically follow allele burden in the course of these trials through the peripheral blood is an important advancement.Whether in the future monitoring the lower prevalence MPN molecular mutations will be helpful in assessment of therapeutic response remains a question to be answered.