Ruxolitinib treatment appears to reduce JAK2 p.V617F allele burden in patients with polycythemia vera (PV) who do not tolerate hydroxyurea, according to a multicenter, open-label, phase 3 randomized study involving more than 200 individuals.

Participants received either ruxolitinib (n=107) or best available therapy with crossover to ruxolitinib at week 32 (n=97). Among the results:

• Average changes from baseline over time in JAK2 p.V617F allele burden ranged from -12.2 to -40.0% in those receiving ruxolitinib; this range was -6.3 to -17.8% in the crossover group.
• Complete molecular response was observed in 2 ruxolitinib patients and 1 crossover patient.
• Partial response occurred in 33 and 20 patients, respectively.
• 1 patient receiving best available therapy achieved partial response before crossover.
• Among patients treated with interferon, average maximal reduction in allele burden from baseline was ~26% after crossover, vs ~7% before.