Pegylated Interferon Alpha-2a in 75 Patients with Myeloproliferative Neoplasms: A Single Center Experience
Authors: Gowin Krisstina L. , Jain Tania , Kosiorek Heidi E. , Camoriano John , Tibes Raoul , Palmer Jeanne , Mesa Ruben A. 
Published: October 2019

Abstract
Background: Pegylated interferon alpha-2a (Peg INF2a) has been demonstrated to be active therapy for high-risk essential thrombocythemia (ET), polycythemia vera (PV), and early myelofibrosis (MF). We retrospectively analyzed the outcomes of Peg INF2a therapy in myeloproliferative (MPN) patients treated outside the constraints of a clinical trial.
Methods: Charts were analyzed for demographic and clinical data. Toxicity to therapy was assessed per CTCAE 3.0 criteria. Therapeutic responses for ET and PV were calculated by the revised ELN/IWG-MRT criteria including complete remission (CR), partial resmission (PR), no response (NR), or progressive disease (PD). Responses in MF were calculated by EUNMET: complete response (CR), major response (MR), moderate response (MoR), minor response (MiR) and NRand the revised IWG-MRT/ELN criteria: CR, PR, clinical improvement (CI), stable disease (SD) or PD.
Results:
Patients: 75 patients were identified overall. There were 36 PV patients (48%), 20 ET patients (26.7%), and 19 MF patients (25.6%). Thirteen MF patients were post-PV/ET MF. The median age at diagnosis was 51.5 yrs (range 28.8-75.1). JAK2 V617 mutation was present in 53 patients (70.7%). Median baseline hemoglobin (g/dL), leukocyte (x10 9), and platelet count (x109) for PV was 13.6, 8.6, 369, for ET was 12.5, 6.8, 517, and for MF was 11.4, 8.0, and 420, respectively. DIPSS risk category for the 19 MF patients: Low in 6 (31.5%) patients, Intermediate-1 in 3 (15.7%), Intermediate-2 in 8 (42%), and High in 2 (10.5%) patients. The majority of patients (82.2%) had received at least one prior cytoreductive therapy for their disease.
Therapy: Median starting dose of Peg INF2a was 45 micrograms/week (range 45-90). The median peak dose was 90 micrograms/week (range 45-270). The median tolerated dose was 60 micrograms/week (range 5.6-180). The median duration of treatment was 24 months (range 3.6-85).
Toxicity: Overall the Peg INF2a was well tolerated. Hematological toxicity included: leukopenia at grade 1 in 13 patients (17.3%), grade 2 in 5 patients (6.7%), and grade 3 in 1 patient (1.3%), anemia at grade 1 in 10 patients (13.3%) and grade 2 in 1 patient (1.3%), thrombocytopenia at grade 1 in 13 patients (17.3%) and grade 2 in 1 patient (1.3%). The most common non-hematologic toxicity included: fatigue at grade 1 in 14 patients (18.7%) and grade 2 in 4 patients (5.3%), transaminitis at grade 1 in 6 patients (8%) and grade 2 in 3 patients (4%), myalgias at grade 1 in 4 patients (5.3%).
Response: See Table #1
PV/ET: 56 patients were evaluated by ELN/IWG-MRT criteria overall: A complete remission (CR) was seen in 8 patients (14.3%), a partial remission (PR) in 18 patients (32.1%), either a CR or PR in 18 patients (32.1%) when histologic remissions were unable to be documented due to lack of restaging bone marrow examination, no response in 11 patients (19.6%), and progressive disease in 1 patient (1.8%). Of the 12 patients receiving at least1 phlebotomy per month, 10 patients (83.3%) became phlebotomy independent with therapy. Of the 20 ET patients, 12 patients (60%) had platelet normalization (<400 x 109).
MF: 19 patients were evaluated by IWG-ELN criteria: a PR was seen in 2 patients (10.5%), CI in 4 patients (21.1%), SD in 12 patients (63.2%), and PD in 1 patient (5.3%). Utilizing EUNMET critieria: 1 patient (5.3%) with a CR, 5 patients (26.3%) with a MR, 3 patients (15.8%) with MoR, 5 patients (26.3%) with MiR, and 5 patients (26.3%) with NR.
Table 1. Peg INF2a Patient Responses RESPONSE Disease IWG-ELN response criteria: (Patient #, %) (Barosi, Blood 2013, Tefferi, Blood 2013) EUMET response criteria: (Patient #, %) (Barosi, Blood 2005) PV: N=36 CR: 3 pts (8.3%) PR: 14 pts (38.8%) CR/PR: 14 pts (38.8%) NR: 5 pts (13.8%) PD: 0 NA ET: N=20 CR: 5 pts (25%) PR: 4 pts (20%) CR/PR: 4 pts (20%) NR: 6 pts (30%) PD: 1 (5%) NA MF: N=19 IWG-ELN: PR: 2 pts (10.5%) CI: 4 pts (21.1%) SD: 12 pts (63.2%) PD: 1 pt (5.3%) EUNMET: CR: 1 pt (5.3%) MR: 5 pts (26.3%) MoR: 3 pts (15.8%) MiR: 5 pts (26.3%) NR: 5 pts (26.3%) NA: Not applicable
Conclusions: Peg INF2a is active and well-tolerated when administered outside of the support of a clinical trial. Given the majority of patients had previously failed cytoreductive therapy these results substantiate prior reports of efficacy of Peg INF2a in MPNs.

Disclosures
Mesa: Pfizer: Research Funding; Gilead: Research Funding; Promedior: Research Funding; Novartis Pharmaceuticals Corporation: Consultancy; CTI Biopharma: Research Funding; Incyte Corporation: Research Funding; NS Pharma: Research Funding; Genentech: Research Funding.