Ropeginterferon Demonstrates Safety and Efficacy in Myelofibrosis: Pilot Study Results

Background:

Myelofibrosis (MF) is a clonal bone marrow disorder characterized by a constitutional symptoms, splenomegaly, anemia, elevated WBC and bone marrow fibrosis. Ruxolitinib is a JAK2 inhibitor approved for patients with Intermediate-2 (INT-2) or high risk disease based on dynamic international prognostic scoring system (DIPSS), however, there are limited options for patients with early disease. Interferon alpha (IFNa) is a cytokine therapy that has been used in treatment of chronic myelogenous leukemia and polycythemia vera (PV). In these diseases, there can be a reduction in the clonal burden in addition to a hematologic response. Therefore, we sought to use this therapy in patients with MF.

Methods:

Patients who had MF were enrolled on an IRB approved clinical protocol in a single arm, single institution study. Patients were stratified to either an early disease arm (characterized by intermediate 1 (INT-1) risk or advanced disease (Int-2 or high-risk disease based on DIPSS). Patients were started on ropeginterferon (interferon-alpha 2b) at 50 ug every two weeks, and the dose was titrated up to either 300 ug every other week, or until unacceptable toxicity. Patients were monitored for response based on IWG criteria.

Results:

Ten patients with MF have been enrolled on the study to date (Early: 3, Int/High: 7). Median age was 69.5 (39 - 88), four patients were female. Five patients had primary MF (PMF), 4 had post-essential thrombocythemia and 1 post PV MF. Five patients had previous treatment for their disease. Four patients continue to receive active treatment (2 early disease, and 2 advanced disease). Reasons for stopping include disease progression (3), toxicity (1), alternate treatment (1) and lack of benefit (1). The median number of cycles for those who ended treatment was 7.5 (4-47), and for those who remain on treatment, they range from 16 – 46 cycles.

Five patients achieved a clinical improvement, 3 had a spleen response, and 2 had a symptom response. A grade 3 adverse event (AE) potentially attributable to the treatment occurred in 6 patients (60%), 4 (40.0%) patients had anemia, and 2 (20.0%) patients had lymphopenia. Only one patient discontinued therapy due to AEs (dizziness, atrial fibrillation). One death has occurred to date, due to an unrelated cause.

Discussion:

Ropeginterferon is a well-tolerated therapy that results in clinical improvement in half the patients, and appears to be well tolerated. These results, along with historic data suggesting possible reduction in clonal burden, suggest that ongoing studies are warranted to further understand the clinical benefit of ropeginterferon.