75 yr old male who recently transferred care to me w/ pmh of P Vera treated with phlebotomy and ASA. He was noted to have a rising WBC count. Also on Hydrea with issues with thrombocytopenia despite low doses [500 mg 1x a week, platelet count nadir of 17k] He was noted to have a rising WBC count [Hb and underwent a BM biopsy which reported changes compatible with post-polycythemia vera myelofibrosis. JAK2 V617F and TET2 mutated. In terms of symptoms: fatigue and weight loss are affecting his QOL. Palpable splenomegaly w/ early satiety. My question was treatment recommendations. I typically start off with Jakafi but with his platelet count would you consider paracritinib. I should note that the platelet counts have been oscillating with low-dose hydrea ranging from 17k to 428k]

MPN Specialist

Interesting to see such wildly fluctuating platelet counts. Pacritinib would certainly be an ideal option if the platelet counts are > 50K, but given the fluctuating nature, I wonder if it is truly the best option. Pacritinib has some tolerability concerns with frequent GI side effects (nausea, vomiting, diarrhea). I would recommend holding the hydroxyurea/lowering the dose and if the platelet come up, then I would try Jakafi first. You may find that the patient is very sensitive to hydroxyurea, but is able to tolerate a decent dose of Jakafi without dropping the platelets. If you can't keep the platelets > 50K on a minimum of 10 mg BID of Jakafi, then I would switch to pacritinib.