MPN-546 A Single-Arm Multicenter Study to Assess the Efficacy, Safety, and Tolerability of Ropeginterferon alfa-2b-njft (P1101) in North American Adults With Essential Thrombocythemia

Context: There is an unmet need for treatment options for patients with essential thrombocythemia (ET) who require cytoreduction who may or may not have been treated with hydroxyurea (HU) or anagrelide (ANA), which is commonly used outside of North America. In addition to the reduction of thrombotic risk, treatment options for ET should reduce all blood cell types, prevent disease progression, and modify the disease. Objective: To assess the efficacy of ropeginterferon alfa-2b-njft (P1101) in adults with ET who live in the US or Canada. Design: Single-arm, open-label study includes a 28-day screening period, a 12-month treatment phase, and a 28-day follow-up period, for a total trial duration of 14 months. P1101 will be administered every 2 weeks during the treatment phase at each study visit, and once a maintenance dose is identified for a patient, bi-weekly minor assessment visits may be replaced with phone visits. A subsequent extension phase will supply P1101 to patients deriving benefit for a total of 3 years of treatment. Setting: Study results will impact the general management of patients with ET. Patients or Other Participants: Adults diagnosed with ET according to the WHO 2016 criteria with a platelet count at screening >4 50 × 10⁹/L, cytoreductive treatment naïve or with prior HU and/or ANA may participate. Patients with a history or presence of clinically relevant depression, risk of suicide, or autoimmune disease may not participate. Interventions: P1101 will be administered subcutaneously every 2 weeks at the starting dose of 250 mcg (Week 0), 350 mcg (Week 2), and target optimal dose of 500 mcg (Week 4) and remain fixed for the 12-month treatment period. Subjects currently on HU or ANA will follow a pre-specified dose-tapering schedule. All subjects will receive low-dose aspirin unless contraindicated. Main Outcome Measures: The primary endpoint is a durable response defined as the proportion of subjects who achieve simultaneous peripheral blood count remission (platelets ≤400×10⁹/L and WBC <10 × 10⁹/L) for at least 80% of bi-weekly measurements consecutively between weeks 32-52. This study is being sponsored by PharmaEssentia USA.