Four Weeks Administration Schedule of Ropeginterferon Alfa-2b (AOP2014/P1101) in Polycythemia Very Patients Allows Maintaining of Efficacy with Favorable Toxicity Profile in the Phase I/II Peginvera Study

Background Ropeginterferon alfa-2b (AOP2014/P1101) is a novel long-acting pegylated IFN-alpha-2b, consisting predominantly of only one isoform, leading to longer half-life and exposure time. Reduced dosing frequencies, better tolerability, improved compliance and more favorable long-term treatment outcomes in patients with polycythemia vera (PV) are expected. The drug has Orphan designation by EMA and FDA and is currently in the phase III stage of development.

Study design The PEGINVERA study (NCT01193699) is the phase I/II single arm dose escalation study with cohort extension after defining the MTD. 51 patients with PV who could be either cytoreduction therapy naive or pre-treated were included. Ropeginterferon alfa-2b was administered subcutaneously in a dose range of 50-540 µg every two weeks. Main objectives were definition of the maximum tolerated dose as well as observation long term safety and efficacy in terms of normalization of blood parameters and molecular abnormalities. The option to switch to an "once every four weeks" schedule has been implemented by the amended protocol for patients who responded well to the treatment and participated in the study for longer than one year. The dose of the study drug had to remain unchanged after the switch, resulting in a decrease of the overall exposure to the drug. Outcomes of this switch are presented here.

Results 44 patients (period A, median exposure duration 37 weeks, mean monthly dose 505 µg), eligible for the analysis ,i.e. being treated in the maintenance setting, were dosed every two weeks based on the Phase II dosing rules prior the amendment. 33 patients (period B, median exposure duration 12 weeks, mean monthly dose 432 µg) were dosed every two weeks beyond the first year and, showing benefit from treatment, have been assessed as eligible for the switch. 28 patients (period C, median exposure duration 93 weeks) were then switched to dosing once every four weeks (mean monthly dose 203 µg). Blood parameters were normalized and remained stable following one year of treatment and could be maintained after the switch (hematocrit, median in % - period A: 42.7, period B: 42.9, period C: 42.8; WBC, median in G/l - period A: 5.6, period B: 5.3, period C: 5.8; platelets, median in G/l - period A: 252, period B: 217, period C: 210). Spleen length stayed stable within the normal range following the switch in the majority of patients (mean, in cm – period A: 11.6, period B: 8.8, period C: 11.1). Complete hematological response could be maintained in 57% of patients in period A, in 38% of patients in period B and in 50% of patients in period C, while for partial hematological responders the results were 71%, 54% and 57%, respectively. Molecular response improved continuously over time, being maintained at the best individual level in 38% of period A patients, compared to 53% of period B and 69% of period C patients. Comparison of patient discontinuations between the arms revealed the following rates: 5(11%) in the period A, 5(15%) in the period B and 3(11%) in the period C, while the mean numbers of adverse events per patient treatment week was 0.15, 0.27 and 0.09 respectively. There were no new drug-related SAEs occurring in the period C.

Conclusions This explorative data re-confirm the feasibility to administer ropeginterferon alfa-2b once every four weeks, while efficacy was maintained compared to the biweekly application schedule. Reduced injection frequency is not associated with a lack or loss of response, but clearly improves tolerability. Finally, continuous reduction of the JAK2 allelic burden indicates that duration of interferon treatment rather than the absolute dose level is an important variable inducing molecular responses. The here presented findings support the idea that interferon alpha effects in PV are pleiotropic, such as induction of immune-surveillance, which may be sufficiently maintained also at lower ropeginterferon alfa-2b levels.