Interferon-α mechanism of action in MPN

Current understanding

Pegylated interferon alfa-2a (and ropeginterferon alfa-2b) induce hematological and molecular responses in MPN by preferentially targeting malignant hematopoietic stem cells, with the most consistent depth of molecular response observed in JAK2V617F-mutant disease. The precise mechanisms of selective HSC targeting — including effects on cell cycle activation, immune-mediated clone elimination, and induction of apoptosis or differentiation — remain incompletely defined. CALR-mutant patients show heterogeneous and generally lower molecular responses than JAK2-mutant patients, and predictors of deep molecular response (DMR) are not yet established.

Evidence log

• 2026-09-15 — Type 1 interferon perturbates clonal competition by reshaping human blood development.: Single-cell multiomic study of human HSCs proposes IFNα polarizes differentiation into anti-inflammatory lymphoid vs inflammatory myeloid states, and CALR- or JAK2-mutant stem cells gain clonal fitness under IFNα by resisting inflammatory myeloid differentiation — offering a mechanistic account of how IFNα depletes MPN clones and why response depth varies by driver. (novelty: 4)
• 2026-06-10 — Ropeginterferon alfa-2b-njft treatment in essential thrombocythemia across different driver mutations: results from a North American, single-arm, multicentre study (EXCEED-ET).: EXCEED-ET Phase 2b North American single-arm trial reports ropeginterferon alfa-2b achieved a 60.2% durable modified ELN response in ET with molecular responses observed across JAK2, CALR, and MPL driver mutations — extending the IFN-α mutant-HSC-depleting mechanism from PV and the Asia-focused SURPASS-ET cohort into a North American ET population spanning treatment-naive and HU-pretreated patients. (novelty: 3)
• 2025-06-26 — Efficacy and Safety of Ropeginterferon Alfa-2b in Low-Risk Polycythemia Vera.: Early trial evidence in low-risk PV requiring cytoreduction shows ropeginterferon alfa-2b substantially reduces phlebotomy need and achieves high complete hematologic response rates with concurrent JAK2 allele-burden reduction, extending the mutant-HSC-depleting mechanism of IFN-α to the low-risk cytoreduction-indicated PV subgroup. (novelty: 3)
• 2026-08-01 — Ropeginterferon alfa-2b in Polycythemia Vera: A systematic review and meta-analysis.: PRISMA meta-analysis of 3 RCTs (n=522) confirms ropeginterferon alfa-2b achieves superior complete hematologic response, partial molecular response, and JAK2V617F allele-burden reduction versus phlebotomy alone in PV, but shows no significant advantage over hydroxyurea — bounding IFN-α’s disease-modifying mechanism against a cytoreductive comparator while validating it against non-cytoreductive control. (novelty: 3)
• 2026-07-23 — Complete Hematological Response Coupled with Molecular Response in Polycythemia Vera Treatment with Ropeginterferon Alfa-2b.: Small single-arm case series of 13 HU-intolerant high-risk PV patients reports that a low-start/slow-titration ropeginterferon alfa-2b regimen with biweekly monitoring achieves complete hematological response at a mean of 4.15 months alongside concurrent JAK2 VAF decline and pruritus resolution — suggesting IFN-α–mediated mutant-clone suppression and symptomatic benefit can manifest well before the conventional 12-month response assessment window. (novelty: 3)
• 2026-09-01 — Type-I interferon-activated NK cells control polycythemia vera in vivo.: Preclinical study identifies NK cells as the primary immune effectors of type-I interferon in PV, mediating preferential TNF-α-dependent killing of JAK2V617F-mutant HSPCs — providing a concrete cellular mechanism for IFN-α’s selective mutant-clone depletion beyond direct HSC-intrinsic effects. (novelty: 5)
• 2026-07-17 — Cross-study analyses of the ropeginterferon alfa-2b effect on phlebotomy in low- and high-risk patients with polycythemia vera.: Cross-study meta-analysis of ropeginterferon alfa-2b in low- and high-risk PV finds durable hematocrit control and phlebotomy independence across risk strata, with the accelerated HIDAT titration regimen producing faster phlebotomy-free responses and deeper JAK2V617F allele-burden reduction than slow titration — implying that IFN-α’s mutant-HSC-depleting activity is dose/exposure-dependent rather than plateaued at conservative doses. (novelty: 3)
• 2025-10-30 — Effective Treatment with Ruxolitinib and Ropeginterferon Alfa-2b for Refractory TAFRO-like Syndrome.: Case report of combined ropeginterferon alfa-2b + ruxolitinib resolving refractory TAFRO-like syndrome in JAK2 V617F PV supports a complementary mechanism in which IFN-α-mediated mutant-clone suppression and JAK-STAT blockade together control hyperinflammatory MPN complications. (novelty: 3)
• 2026-06-10 — Ropeginterferon for High Risk JAK2 Clonal Hematopoiesis: First trial of ropeginterferon alfa-2b in JAK2 clonal hematopoiesis without overt MPN probes whether IFN-α’s preferential JAK2-mutant HSC targeting is engageable before MPN diagnosis, testing the mechanism at the earliest detectable clonal stage. (novelty: 4)
• 2026-06-04 — AlloHCT With PegINFa for Myelofibrosis: Phase 1 dose de-escalation trial is testing pegylated interferon alfa-2a as post-alloHCT maintenance in primary/secondary myelofibrosis, extending IFN-α’s hypothesized mutant-HSC-depleting mechanism into the post-transplant minimal residual disease setting where donor immune reconstitution may synergize with IFN-α signaling. (novelty: 4)
• 2026-04-08 — A paradigm shift in the treatment of patients with polycythemia vera. The initial early use of recombinant interferon-alpha.: Review synthesizing 35 years of evidence (including PROUD-PV/CONTINUATION-PV and Low-PV trials) argues rIFNα achieves superior molecular remission and disease-modifying activity versus hydroxyurea or phlebotomy alone, supporting early-line use across both low- and high-risk PV. (novelty: 3)
• 2026-05-10 — Scalable genotyping in fixed transcriptomes resolves clonal heterogeneity via single-cell sequencing: GIFT single-cell genotype+transcriptome data reveal an endogenous, JAK2V617F dose-dependent interferon transcriptional program already operating in mutant HSCs, suggesting therapeutic IFN-α may act on a clone whose baseline IFN-pathway tone is itself set by mutant allele burden — a possible substrate for the preferential JAK2-mutant molecular response to pegIFN. (novelty: 5)
• 2026-04-14 — Mechanism of Action of Interferon in the Treatment of Myeloproliferative Neoplasms: cross-connection with clonal-hematopoiesis: IFN-α is hypothesized to act by preferentially activating and depleting mutant HSCs, directly modulating the clonal hematopoiesis substrate of MPN. (novelty: 3)

Open questions

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