Ropeginterferon alfa-2b has minimal transplacental passage and breastmilk secretion in pregnant patients with MPN

Pregnancy in patients with myeloproliferative neoplasms (MPNs) poses unique challenges due to increased risks of maternal complications and adverse fetal outcomes.Interferon-alpha (IFN-) has been shown to be safe and is the preferred cytoreductive agent in pregnant MPN patients.Ropeginterferon alfa-2b (RopegIFN) is a novel monopegylated interferon and is the only IFN approved for the treatment of polycythemia vera (PV), but also used for essential thrombocythemia (ET) and myelofibrosis; yet, limited data exist on the safety of RopegIFN during pregnancy and lactation.In this study, we report four cases of pregnant MPN patients treated with RopegIFN, in whom maternal blood, umbilical cord blood, and breast milk samples were analyzed to assess exposure to RopegIFN.Quantitative ELISA and dot-blot assays demonstrated therapeutic levels of RopegIFN in maternal plasma but negligible levels in cord blood and breast milk, suggesting minimal transplacental transfer and excretion into breast milk.This is the first study to provide pharmacokinetic evidence of RopegIFN exposure during pregnancy and lactation.These findings support the safety of RopegIFN use in pregnant ET and PV patients and highlight the need for a collaborative registry to collect real-world data and guide management for this high-risk population.