Ropeginterferon-α2b in mycosis fungoides and Sézary syndrome: Safety and efficacy in 41 patients.

BACKGROUND AND OBJECTIVES: Pegylated interferon-α2a became the off-label alternative for treating mycosis fungoides/Sézary syndrome (MF/SS) after non-pegylated interferons were withdrawn. This study aimed to evaluate the safety and efficacy of ropeginterferon-α2b in MF/SS. PATIENTS AND METHODS: We performed a retrospective multicenter analysis at 5 Austrian centers and 1 Dutch center, including 41 patients with MF or SS who were treated with ropeginterferon-α2b between October 2024 and September 2025. RESULTS: We included 38 MF (early-stage n = 16, advanced-stage n = 22) and 3 SS patients. In 70.7 % of cases (29/41), ropeginterferon-α2b was administered as part of a combination treatment with a mean dose of 100 µg every 2 weeks. We observed an overall response rate of 48.8 % over a median treatment duration of 6 months (range 1-11 months). Treatment was discontinued in 16 patients (39.0 %) after a median of 4 months because of progressive disease (n = 9), adverse events (n = 4), or other reasons (n = 3). Most frequent AEs were fatigue/flu-like symptoms (32.5 %), anemia (15 %), neutropenia (15 %), lymphopenia (10 %), and elevated liver enzymes (10 %), classified as grade 1 or 2. CONCLUSIONS: Conclusions: This study provides initial evidence that ropeginterferon-α2b may be effective and well tolerated in patients with CTCL. Although interpretation is limited by the small retrospective cohort and short follow-up, the observed outcomes appear comparable to those previously reported for other interferon-α formulations.