Thromboembolic Risk Reduction and High Rate of Complete Molecular Response with Long-Term Use of Ropeginterferon Alpha-2b in Polycythemia Vera: Results from a Randomized Controlled Study

Introduction: The key treatment goals for polycythemia vera (PV) are to prevent thromboembolic events and minimize the risk of progression, ultimately modifying the natural history of the disease by selectively targeting the malignant clone. In the PROUD-PV/CONTINUATION-PV study, long-term treatment with ropeginterferon alpha-2b (BESREMi®; hereafter ropeg) was compared with standard cytoreductive therapy regarding thromboembolic and other adverse events as well as hematological and molecular parameters over a four-year period. Methods: Cytoreduction-naïve or HU-pre-treated patients aged ≥18 years diagnosed with PV according to WHO 2008 criteria were eligible. A total of 257 patients were randomly allocated to ropeg or hydroxyurea at individualized doses for 12 months in the initial study phase (PROUD-PV). In the ongoing extension phase (CONTINUATION-PV), patients in the hydroxyurea arm were permitted to switch to best available treatment. Efficacy assessments included a longitudinal analysis of complete hematological response (CHR) and complete molecular response (CMR; JAK2V617F was determined using real-time PCR [ipsogen® JAK2 MutaQuant® kit; QIAGEN GmbH]), defined by modified ELN criteria. Discontinued patients were considered non-responders. A data snapshot was performed once all patients reached 48 months of treatment; all available safety data were included. Results: Ninety-five patients in the ropeg arm and 76 in the control arm entered the extension phase. At the time of analysis 139 patients remained on study: 74/95 in the ropeg arm and 65/76 in the control arm. Almost all patients in the control arm (>97% at the last available assessment) continued on HU. The rate of patients in CHR was significantly higher in the ropeg arm than in the control arm in the 4th year (60.6% versus 43.4%; p=0.02), as seen after 2 and 3 years of treatment. In line with this effective control of hematologic parameters by ropeg, a very low rate of major thromboembolic adverse events was observed in the ropeg arm: 0.0%, 0.0% and 1.1% of patients in the 2nd, 3rd and 4th years, respectively. In the control arm, rates of major thromboembolic adverse events in the 2nd, 3rd and 4th year were 0.9%, 1.4% and 0.0%, respectively. The median JAK2V617F allele burden declined from 37.3% at baseline to 9.8% over 4 years in the ropeg arm, whereas in the control group, the median allele burden increased from 38.1% to 43.1% in the same period (p<0.0001). The rate of molecular response (partial or complete) at 48 months was significantly higher among ropeg-treated patients than in the control arm (67.0% versus 25.7%; RR: 2.5 [95% CI: 1.7 to 3.7; p<0.0001]). No patients achieved CMR in the control arm. In the ropeg arm, 13 patients had a JAK2V617F allele burden below the threshold of 1% at month 48, 11 of whom also had a CHR at this time point. An additional 34 patients in the ropeg arm achieved an allele burden <10% at 48 months, suggesting that further patients may reach the <1% threshold with ongoing treatment. In terms of safety, no new signals were detected in the 4th year. Rates of patients with treatment-related adverse events remained similar in the ropeg and control arms in the 4th year (ropeg: 28.7% of patients; control: 22.9%). Disease or treatment-related secondary malignancies reported in the entire study period comprised 2 cases of acute leukemia, 2 cases of basal cell carcinoma and 1 case of malignant melanoma, all in the control group; 1 case of disease-related transformation to myelofibrosis occurred in each treatment arm. Conclusions: Ropeg minimizes the occurrence of thromboembolic events in patients with PV over long-term treatment, without leukemogenic risk. In addition, we show for the first time in a randomized study that, in contrast to hydroxyurea, long-term ropeg treatment is capable of inducing deep molecular responses including CMR, which underscores its disease modifying potential. These results also suggest that selected patients could achieve operational cure (with both CHR and CMR) with ropeg, opening the way for treatment discontinuation. Disclosures Kiladjian: Novartis: Honoraria, Research Funding; AOP Orphan: Honoraria, Research Funding; Celgene: Consultancy. Klade:AOP Orphan Pharmaceuticals AG: Employment. Illés:Takeda, Seattle: Research Funding; Janssen, Celgene, Novartis, Takeda, Roche, Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees. Mayer:AOP Orphan Pharmaceuticals AG: Research Funding. Krejcy:AOP Orphan Pharmaceuticals AG: Employment. Hasselbalch:Novartis: Research Funding; AOP Orphan Pharmaceuticals: Other: Data monitoring board. Kralovics:Pharma Essentia: Honoraria; MyeloPro Diagnostics and Research: Equity Ownership; AOP Orphan Pharmaceuticals AG: Honoraria, Other: Advisory board; Qiagen: Honoraria; Novartis: Honoraria. Gisslinger:Celgene GmbH: Honoraria; Pharma Essentia: Other: Personal fees; Roche Austria GmbH: Consultancy; Janssen-Cilag: Honoraria; Novartis Pharma GmbH: Consultancy, Honoraria, Research Funding; AOP Orphan Pharmaceuticals: Consultancy, Honoraria, Research Funding; Myelopro GmbH: Consultancy.