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Results of the phase II trial Low-PV: Ropeginterferon versus phlebotomy for low risk PV

Jul 13, 2020

At the 25th European Hematology Association (EHA) Annual Congress, our Steering Committee member Tiziano Barbuipresented the preplanned interim results from the phase II trial Low-PV ( NCT03003325). This is a randomized study comparing the efficacy of the monopegylated interferon, ropeginterferon alfa-2b, plus phlebotomy versusphlebotomy alone in low-risk patients with polycythemia vera (PV).

Currently, phlebotomy alone is considered the standard of care for patients of ≤ 60 years with PV and no history of thrombosis, who are defined as low risk. 1However, it is still unclear whether phlebotomy alone is enough to maintain hematocrit (HCT) at < 45% over time, a target that significantly reduces the risk of cardiovascular-related death or major thrombosis events as reported by the CYTO-PV phase III trial. 2  Another unanswered question is whether the addition of other cytoreductive agents, like ropeginterferon alfa-2b, can lead to more robust outcomes in this low-risk patient population. 1To address these questions and evaluate the benefit/risk profile of ropeginterferon alfa-2b versusphlebotomy alone, the Low-PV trial was established.

Study design

  • Phase II, multicenter, randomized trial in patients aged 18–60 years without history of thrombosis
  • All patients (N = 150) were phlebotomized upon study entry to achieve HCT < 45%, and then randomized 1:1 to either:
    • Phlebotomy plus low dose acetylsalicylic acid (ASA) (n = 75), or
    • Phlebotomy plus ASA plus 100 μg of ropeginterferon alfa-2b every 2 weeks (n = 75)
  • The composite primary endpoint was the proportion of patients maintaining a median HCT value of < 45% over 12 months, with no signs of progressive disease, including thrombosis, bleeding, progressive leukocytosis, symptomatic or extreme thrombocytosis, symptomatic splenomegaly, or other uncontrolled symptoms
  • Secondary endpoints included the number of phlebotomies, bone marrow morphology, incidence of thrombohemorrhagic events, quality of life, and safety
  • Data cut-off for this interim analysis was the end of February 2020 (N = 100)
  • Baseline patient characteristics were well balanced between the arms and are shown below in Table 1

Table 1 . Baseline patient characteristics from Low-PV 1

ASA, acetylsalicylic acid; CI, confidence interval; JAK2, Janus kinase 2


Ropeginterferon alfa-2b arm
(n = 50)

Standard phlebotomy arm
(n = 50)

p value

Male/female patients, %




Median age (range), years

51.4 (31.9–59.7)

48.1 (23.5–60.8)


Previous ASA/phlebotomies, %




Patients with diagnosis, %

< 3 years

3–5 years

> 5 years












Median hemoglobin, g/dL (95% CI)

13.55 (11.6–15.6)

13.65 (11.9–15.9)


Median platelets, x 10 9/L (95% CI)

> 1000 x 10 9/L, %

645 (278–1127)


677 (254–1202)



Median hematocrit, % (95% CI)

44.2 (40.7–47.7)

44.6 (40.3–49.7)


Median white blood cells, x 10 9/L (95% CI)

> 11 x 10 9/L, %

10.83 (6.27–21.50)


10.89 (6.16–22.64)



Median JAK2V617F allelic burden, % (range, n = 67)

30.0 (3.0–88.0)

35.9 (0.0–98.0)


Palpable splenomegaly, %




Median bone marrow cellularity, % (range)

80 (35–95)

70 (35–95)



  • The primary endpoint was achieved by 84% of patients in the ropeginterferon alfa-2b arm versus60% of patients in the standard phlebotomy arm (Odds ratio, 3.5; 95% CI, 1.3–10.4; p = 0.008)
  • HCT control was achieved by 84% of patients in the ropeginterferon alfa-2b arm versus66% of patients in the standard phlebotomy arm
  • Disease progression occurred in 0% of patients in the ropeginterferon alfa-2b arm versus8% in the standard phlebotomy arm (n = 4)
  • The number of phlebotomies needed was significantly lower in the ropeginterferon alfa-2b arm versusthe standard phlebotomy arm (43% vs57%; p = 0.024)
  • Reduction in symptom severity by 21% occurred in the patients receiving ropeginterferon alfa-2b plus phlebotomy, which was not observed in the standard phlebotomy arm (p = 0.033)


  • The incidence of any adverse event (AE) as well as that of treatment-related adverse events were higher in the ropeginterferon alfa-2b arm than the standard phlebotomy arm. Nevertheless, the incidence of severe Grade 3 AEs was similar between the arms as shown below in Table 2

Table 2 . Safety profiles reported in the interim analysis of the Low-PV trial 1

AE, adverse event; TEAEs, treatment-related adverse event

Statistical significance is indicated by bold font


Ropeginterferon alfa-2b arm, %
(n = 50)

Standard phlebotomy arm, %
(n = 50)

p value

Any AE



< 0.001




< 0.001

Severe Grade 3 AEs





The above data from the interim analysis of the Low-PV phase II trial indicate that ropeginterferon alfa-2b addition to phlebotomy is more efficacious than the current standard therapy of phlebotomy alone in low risk patients with PV. Patients in the ropeginterferon alfa-2b arm were better able to maintain HCT at target levels for a long duration of time and required a significantly lower number of phlebotomies, when compared to the phlebotomy alone arm. Despite the increased incidence of TEAEs seen in the ropeginterferon alfa-2b arm, the incidence of severe AEs was similar across the arms and quite low. Further secondary endpoints from the trial are planned for evaluation in 2022. You can also listen to Tiziano Barbui’s interview with the MPN Hub explaining the importance and outcomes of the Low-PV trial, in the video below.

Should ropeginterferon become SoC for all patients with low-risk PV?

  1. Barbui T, Vannucchi AM, De Stefano V, et al. Phase II randomized clinical trial comparing ropeginterferon versus phlebotomy in low-risk patients with polycythemia vera. Results of the pre-planned interim analysis. Oral Abstract #LB2602. 25th EHA Annual Congress; June 14, 2020; Virtual.
  2. Finazzi G, Specchia G, Marchioli R, et al. Cardiovascular events and intensity of treatment in polycythemia vera. N Engl J Med. 2013;368:22-33. DOI: 10.1056/NEJMoa1208500