Long-Term Use of Ropeginterferon Alpha-2b in Polycythemia Vera: 5-Year Results from a Randomized Controlled Study and Its Extension

Introduction:

Patients with polycythemia vera (PV) require life-long treatment to prevent thromboembolic events and minimize the risk of progression. Ropeginterferon alpha-2b (BESREMi®; hereafter ropeg) may ultimately modify the natural history of PV by selectively targeting the malignant clone. In the PROUD-PV/CONTINUATION-PV studies, long-term treatment with ropeg was compared with standard cytoreductive therapy regarding thromboembolic and other adverse events as well as evolution of hematologic and molecular parameters over five years.

Methods:

Patients aged ≥18 years and diagnosed with PV according to WHO 2008 criteria who were either cytoreduction-naïve or hydroxyurea (HU)-pre-treated for < 3 years were enrolled. A total of 257 patients were randomized 1:1 (stratified by age > 60 years, prior thromboembolic events, and HU pre-treatment) to receive ropeg or HU at individualized doses for 12 months in the initial study (PROUD-PV). In the extension study (CONTINUATION-PV), patients in the HU arm were permitted to switch to best available treatment. Efficacy assessments included hematologic parameters, phlebotomy need, JAK2V617F allele burden, and molecular response defined by modified ELN criteria. An interim analysis was conducted once all patients reached 5 years of treatment; efficacy data for patients enrolled in the extension study and all available safety data were analyzed.

Results:

Ninety-five patients in the ropeg arm and 76 in the control arm entered the extension study. Most patients in the control arm continued to receive HU (88% at month 60). At the time of this 5-year analysis, 70 patients in the ropeg arm and 57 in the control arm remained on study; discontinuation rates were balanced between the treatment arms (ropeg: 26.3%; control: 25.0%).

Hematocrit <45% was maintained without the need for phlebotomy in 81.8% patients in the ropeg arm in the fifth year of treatment, which was significantly higher than the rate of 63.2% observed in the control group (p=0.01). Very few patients experienced a major thromboembolic adverse event (4.2% [1.2%-patient year] of patients in the ropeg arm and 6.6% [1.2%-patient-year] of patients in the control arm during the entire treatment period).

With respect to the causative JAK2V617F mutation, the median allele burden declined from 37.3% at baseline to 7.3% over 5 years of treatment in the ropeg arm, whereas in the control arm the median allele burden increased from 38.1% to 42.6% in the same period (p<0.0001). The rate of molecular response at 5 years was also significantly higher among ropeg-treated patients than in the control arm (69.1% versus 21.6%; RR: 3.2 [95% CI: 2.1 to 4.9; p<0.0001]). The sustained molecular response observed in ropeg-treated patients was accompanied by a low risk of disease progression; only 1 case of progression to myelofibrosis (0.20%-patient year) was reported during the entire study period and no leukemic transformation occurred. In contrast, 2 cases of progression to myelofibrosis and 2 cases of transformation to acute leukemia (1.0%-patient year in total) were reported in the control arm.

A further analysis of combined hematologic and molecular parameters was performed, these being known to influence the risk of thrombosis and of progression in PV. At the 5 year visit, 58.5% of patients receiving ropeg had well-controlled hematocrit (<45%) without requiring phlebotomy, as well as achieving a molecular response, compared to 17.3% on standard treatment (RR: 3.52 [2.13 to 5.81]; p<0.0001).

Regarding safety and tolerability, no new signals were detected in the fifth year. Treatment related adverse events were reported in 25.6% and 24.2% of patients in the ropeg and control arms, respectively, and one patient in each arm withdrew due to drug-related toxicity. Three patients (3.8%) in the ropeg arm reported grade ≥3 treatment-related adverse events in the fifth year; over the entire treatment period, the rate of grade ≥3 drug-related adverse events was the same in each study arm (16.5%).

Conclusions:

In a randomized controlled setting, ropeg treatment effectively controlled hematocrit and minimized the occurrence of thromboembolic events in patients with PV. Disease progression was very rare during long-term treatment with ropeg and this possible change in the disease natural history appears to be related to deep and durable molecular responses selectively achieved with ropeg.