Hemolytic disease of the fetus and newborn (HDFN) often results in severe anemia resulting in intrauterine transfusions and increased risk of fetal death. According to the recently published phase 2 UNITY study of 13 pregnancies, nipocalimab (a human monoclonal antibody that blocks the Fc receptor) given during pregnancy helps to prevent maternal IgG alloantibodies from crossing the placenta and delays or prevents severe HDFN. New analysis from the study shows limited, but not zero, potential for nipocalimab exposure to fetuses and neonates as maternal serum levels are pharmacologically active (>10 µg/mL). All four of the fetal cordocentesis samples from intrauterine transfusions during the study were below pharmacologically active levels. Of the 10 cord blood samples available, only one infant had detectable levels of nipocalimab at 0.70 µg/mL. Seven of the nine available breast milk samples taken 6 to 8 days after delivery had undetectable levels of nipocalimab, while two had concentrations less than 4 µg/mL. While cord blood levels of IgG were below normal in 10 of 12 live births after antenatal exposure, 8 of 9 infants had normal serum IgG levels by week 24. In addition, neonatal infections were typical as were 6 of 7 vaccine responses to diphtheria and tetanus. Further studies are needed on the safety and efficacy of nipocalimab to prevent HDFN.
References:
- de Winter DP, Moise KJ, Ling LE, Oepkes D, et al. Infant Immunity after Maternal Nipocalimab in Severe Hemolytic Disease of the Fetus and Newborn. NEJM Evid. 2026 Feb;5(2):EVIDoa2500097. doi: 10.1056/EVIDoa2500097. Epub 2026 Jan 27. PMID: 41591368.
- Moise KJ Jr, Ling LE, Oepkes D, Tiblad E, et al; UNITY Study Group. Nipocalimab in Early-Onset Severe Hemolytic Disease of the Fetus and Newborn. N Engl J Med. 2024 Aug 8;391(6):526-537. doi: 10.1056/NEJMoa2314466. PMID: 39115062.
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