Evidence for Superior Efficacy and Disease Modification after Three Years of Prospective Randomized Controlled Treatment of Polycythemia Vera Patients with Ropeginterferon Alfa-2b Vs. HU/BAT

Background: Interferon-alpha (IFN) is being used in myeloproliferative neoplasms (MPNs) since years and remains the only known treatment with disease-modifying potential. Ropeginterferon alfa-2b (Ropeg) is a novel mono-pegylated IFN, with reduced dosing frequency and improved tolerability. Here, we report 3 years clinical data from the phase III PROUD/CONTI-PV trials with an additional emphasis on the first comprehensive, prospective, randomized, controlled genomic profiling including not only JAK2V617F, but longitudinal targeted sequencing to identify non-JAK somatic mutations and chromosomal aberrations.

Study design: 254 PV patients (WHO 2008 criteria, naïve to cytoreduction or HU pretreated but not resistant) were randomized to receive Ropeg or hydroxyurea (HU) in the PROUD-PV study and were rolled over to CONTI-PV study after 12 months, with the option to switch from HU to best-available-therapy (BAT). Efficacy assessment included complete hematological response (CHR, by ELN criteria), and CHR plus symptom improvement (PV-related symptoms and signs including clinically significant splenomegaly). Secondary endpoints included JAK2V617F molecular response (MR, modified ELN criteria). Next-generation-sequencing (NGS, TruSight Myeloid Panel, Illumina) and genome-wide analysis (SNP 6.0, Affymetrix) was applied comprehensively as exploratory genetic work-up.

Results: 83 (Ropeg) and 70 (HU/BAT) patients completed the 36-month efficacy analysis time point, mean treatment duration for safety analysis was 3.8 years. Median doses in the third year remained constant: 425 µg Ropeg every 2 weeks and 1,000 mg HU per day. In the HU/BAT arm over 97% of patients remained treated with HU.

After 36 months of treatment, maintenance of higher responder rates (full analysis set) was shown in the Ropeg arm compared to HU/BAT for CHR (70.5% vs. 51.4%; p=0.0122; RR [95% CI]: 1.38 [1.07-1.79]) and for CHR plus symptom improvement (52.6% vs. 37.8%; p=0.0437; RR [95% CI]: 1.42 [1.01-2.00]). In contrast to HU/BAT, response rates were steadily increasing in the Ropeg arm throughout 24 months of treatment and remained constant after 36 months. Regarding safety, comparable numbers of patients experienced adverse events (89.8% for Ropeg, 90.6% for HU) and treatment-related adverse events (74.8% for Ropeg, 78.7% for HU). The most common (>10%) treatment-related adverse events anemia, thrombocytopenia and leukopenia occurred more frequently under HU, whereas GGT increase was mainly observed under Ropeg. No new safety signals appeared in the third year of treatment.

Regarding JAK2V617F, after 36 months 66.0% of patients in the Ropeg arm but only 27.0% in the HU/BAT arm had achieved MR (p<0.0001; RR [95% CI]: 2.31 [1.56-3.42]). Importantly, MR strongly correlated with CHR. The most common non-JAK mutations involved TET2 (15% of all patients), followed by DNMT3A, ASXL1, CUX1, CEBPA and EZH2. Besides frequent JAK-related chr9 aberrations (88% of patients), other cytogenetic aberrations were detected in 49 patients (23%). Although both treatments showed effects on the genomic level there were marked differences: HU appeared as potent suppressor of JAK2V617F only during the initial phase, while lacking the ability to suppress additional clones with different mutations. In contrast Ropeg was able to reduce also non-JAK allele burden including TET2. On the cytogenetic level, acquisition of novel genomic lesions occurred selectively under HU.

In line with these molecular findings, disease or treatment related secondary malignancies occurred only in the HU cohort, including 2 cases of acute myeloid leukemia, 1 melanoma and 2 basaliomas, whereas in the Ropeg cohort 3 malignancies (glioblastoma, seminoma, adrenal neoplasm) most likely unrelated to IFNa treatment were reported. For one case of AML detailed longitudinal analysis revealed loss of JAK2V617F followed by rapid acquisition of DNMT3A and U2AF1 mutations shortly prior onset of leukemia.

Conclusions: These data demonstrate high and durable hematologic responses and symptom control with good tolerability under Ropeg. The effect not only on JAK2V617F but other mutations involved in MPNs and on cytogentic aberrations confirm the concept of disease modification capability of IFNa. Ropeginterferon alfa-2b will provide a valuable and safe new long-term treatment option with features distinct from other treatment modalities including HU.