Rusfertide rapidly decreases hematocrit in patients with suboptimally controlled polycythemia vera.

Polycythemia vera (PV) is characterized by overproduction of erythrocytes, leukocytes, and platelets. Rusfertide is a hepcidin mimetic polypeptide that binds to ferroportin and decreases iron delivery to bone marrow, reducing the production of red blood cells. The primary objective of this study was to evaluate the efficacy and safety of rusfertide in patients with PV and elevated (>48 %) baseline hematocrit. Patients were treated with 40 mg subcutaneous rusfertide twice weekly until their hematocrit reached < 45 %; once achieved, patients received weekly rusfertide dosing. Of the 20 patients enrolled, 15 (75 %) completed 24 weeks of treatment, 13 (65 %) completed 52 weeks, and 7 discontinued rusfertide therapy. Mean baseline hematocrit was 51.6 %. By Week 8, 17 (85 %) patients achieved hematocrit < 45 %, and 19 (95 %) achieved ≥ 5 % absolute reduction from baseline. Median time to first hematocrit < 45 % was 4.9 weeks. Mean hematocrit was < 45 % at Week 4 and subsequently remained < 45 % throughout the study. No patients received phlebotomy during rusfertide treatment. Rusfertide led to a significant reduction in erythrocyte count (5.98 ×1012/L to 4.79 ×1012/L; nominal p-value 0.0036) and an improvement in iron deficiency markers (eg, ferritin and mean corpuscular volume) relative to baseline. Seventeen patients (85 %) experienced treatment-emergent adverse events, most of which were Grade 1/2. In this open-label phase 2 study, rusfertide resulted in a rapid and sustained improvement in hematocrit and was generally well tolerated. Rapid and sustained control of hematocrit reduces the need for therapeutic phlebotomy and may help reduce thrombotic and cardiovascular events over the long term in patients with PV.