Ropeginterferon alpha-2b targets JAK2V617F-positive polycythemia vera cells in vitro and in vivo

Abstract

Polycythemia vera is characterized by the acquisition of the JAK2V617F mutation. Recommended treatments include hydroxyurea and interferon-alpha. Several groups have reported a reduction in the JAK2 mutant allele burden in interferon-treated patients, but significance of this observation is questioned. We characterized the activity of ropeginterferon alpha-2b, a novel form of interferon-alpha recently shown to be safe and efficacious in polycythemia vera. Ropeginterferon was able to inhibit the proliferation of the HEL, UKE-1, and UT-7 JAK2-mutant cell lines while sparing JAK2-wild-type UT-7 and normal CD34+ cells growth. In vitro treatment of erythroid progenitors derived from PV patients showed that ropeginterferon could considerably inhibit the growth of endogenous erythroid colonies, a hallmark of polycythemia vera. Finally, we could study in sequential samples the clonal architecture of erythroid progenitors derived from patients included in a randomized study comparing hydroxyurea to ropeginterferon. After 1 year of treatment with ropeginterferon, the ratio of JAK2-mutated to wild-type colonies grown from bone marrow progenitors was reduced by 64%, compared to 25% in patients receiving hydroxyurea. This study shows that ropeginterferon has a potent targeted activity against JAK2-mutant cells and is able to drastically reduce the proportion of malignant progenitors in patients treated with this drug.

Trial registration: ClinicalTrials.gov NCT01949805.

Fig. 1. Antiproliferative effect of Ropeg in MPN-derived human cell lines.

A and B The JAK2^V617F positive UKE1 and HEL cell lines. C and D The UT-7 cell line expressing a wild type or a mutant form of JAK2. Cells were treated with the indicated drugs and the living cells were counted every day. Results are expressed as the fold increase compared to day 0

Fig. 2. Targeted inhibition of JAK2^V617F progenitors in vitro and in vivo

A Clonogenic assays on primary peripheral blood mononuclear cells from 4 PV patients. Median percentages and standard deviations of residual erythroid colonies in treated conditions compared to untreated are presented. B and C JAK2^V617F allele burden evolution in patients included in the PROUD-PV trial in France. B median of the %JAK2V617F in HU (N = 5) or Ropeg (N = 3) treatment arms. C Comparison of the % reduction of JAK2V617F allele burden in patients after 1 year of treatment in each arm. Median and standard deviations in both groups of treatment are represented. (*p < 0.02; unpaired t-test). D and E Clonogenic assays performed on bone marrow samples from patients included in the PROUD-PV trial in France. Percentages of JAK2^V617F positive erythroid colonies before and after 1 year of treatment in patients treated with Ropeg or HU. UPN of each individual patient is given