ruxolitinib (JAKAVI°) and polycythaemia vera Inconclusive evaluation

Patients with polycythaemia vera, a myeloproliferative syndrome, are at increased risk of thrombotic events. Marrow fibrosis and transformation to acute leukaemia can also occur after several years. Treatment is based on phlebotomy and aspirin at low (antiplatelet) doses, sometimes combined with hydroxycarbamide, a cytotoxic drug. Various other drugs are available if hydroxycarbamide fails or is poorly tolerated, but there is no consensus treatment. Ruxolitinib inhibits Janus tyrosine kinases, which are involved, among other roles, in haematopoiesis. Ruxolitinib has been authorised in the European Union for patients with polycythaemia vera in whom hydroxycarbamide has failed or is poorly tolerated. Clinical evaluation of ruxolitinib in this setting is based on a randomised, unblinded trial versus treatment chosen by the investigators, in 222 patients treated for 32 weeks. Hydroxycarbamide was chosen in 59% of cases, even though the patients had unacceptable adverse effects or an inadequate response to the drug. The efficacy of the investigators' other treatment choices was uncertain. Phlebotomy was less frequent in the ruxofitinib group than in the control group. The adverse effects of ruxotitinib in this situation are poorly documented, due to inadequate long-term assessment. In the short term, ruxolitinib causes anaemia and thrombocytopenia, as well as bleeding, potentially severe infections, headache, sensory disturbances, and weight gain. It is also likely to share the serious adverse effects of other immunosuppressants. Ruxolitinib is mainly metabolised by cytochrome P450 isoenzymes CYP3A4 and CYP2C9, creating a risk of multiple drug interactions. Ruxolitinib showed embryofetal toxicity in animal studies. Virtually no data are available in pregnant women. In practice, available data on the harm-benefit balance of ruxolitinib fail to show that this drug represents a tangible advance for patients with polycythaemia vera, as compared with other drugs used when hydroxycarbamide is unsuitable.