Efficacy and safety of a three-step dose escalation regimen of ropeginterferon alfa-2b in Japanese patients with polycythemia vera: a phase 3b, single-arm, multicenter study

Ropeginterferon alfa-2b, a monopegylated interferon α-2b, is a cytoreductive treatment for polycythemia vera (PV). In Japan, the current regimen involves titration in 50-µg increments every 2 weeks until reaching the maximum dose (500 µg), which requires considerable time. This phase 3b, open-label, single-arm, multicenter study (October 2023-July 2024) assessed the efficacy and safety of a three-step dose escalation regimen (day 1: 250 µg, week 2: 350 µg, week 4: 500 µg) of ropeginterferon alfa-2b in Japanese patients with PV (NCT06002490). Twenty-one patients were included (mean age: 57 years); most (95.2%) received ropeginterferon alfa-2b for at least 24 weeks. The complete hematologic response rate (primary endpoint; hematocrit < 45%, no phlebotomy in the previous 12 weeks, platelet count ≤ 400 × 10⁹/L, and white blood cell count ≤ 10 × 10⁹/L) was 23.8% (95% confidence interval 8.2, 47.2) at week 12 and 57.1% (34.0, 78.2) at week 24. Most patients (90.5%) reached the maximum dose of 500 µg by week 4. All patients had treatment-emergent adverse events, but none led to death, treatment discontinuation, or study withdrawal. This three-step dose escalation regimen of ropeginterferon alfa-2b has the potential to provide faster therapeutic effects in patients with PV without additional safety concerns.