Ropeginterferon alfa-2b, a novel IFNα-2b, induces high response rates with low toxicity in patients with polycythemia vera.

In this prospective, open-label, multicenter phase 1/2 dose escalation study, we used a next-generation, mono-pegylated interferon (IFN) α-2b isoform, ropeginterferon alfa-2b. The unique feature of ropeginterferon alfa-2b is a longer elimination half-life, which allows administration every 2 weeks. We present data from 51 polycythemia vera patients. The main goal was to define the maximum tolerated dose and to assess safety and efficacy. A dose range of 50 to 540 µg was tested without the appearance of dose-limiting toxicities. All drug-related adverse events were known toxicities associated with IFN-α. The cumulative overall response rate was 90%, comprising complete response in 47% and partial response in 43% of patients; the best individual molecular response level was a complete response in 21% of patients and partial response in 47%. Notably, we did not observe any correlation between the dose level and the response rate or response duration, suggesting that already low levels of ropeginterferon alfa-2b are sufficient to induce significant hematologic and molecular responses. These data suggest promising efficacy and safety of ropeginterferon alfa-2b and support the development of the drug in a randomized phase 3 clinical trial. The study was disclosed at www.clinicaltrials.gov as #NCT01193699 before including the first patient.