Congenital heart block, sometimes referred to as cardiac neonatal lupus, is a rare but potentially life-threatening condition that affects babies born to mothers with specific autoantibodies-called anti-SSA/Ro antibodies-which can attack the fetal heart via its electrical conduction system, leading to a slower heart rate. Most surviving infants with congenital heart block eventually require a pacemaker for life. In a study of one pregnant mother with systemic lupus erythematosus and high levels of anti-SSA/Ro antibodies, NYU Langone Health researchers found a drug that blocks the movement of harmful immune proteins (autoantibodies) across the placenta and into the fetal circulation, preventing development of congenital heart block in the newborn. The researchers who treated the pregnant mother say this is the first case of using the drug, rozanolixizumab, a neonatal Fc receptor (FcRn) inhibitor, to prevent congenital heart block. Publishing in the journalAnnals of the Rheumatic Diseasesonline Oct. 18, the researchers report how they used weekly injections of rozanolixizumab, given from week 14 to 28 of the mother’spregnancy— when the fetal heart is most vulnerable. Ultrasound and at-home heart rhythm checks were used to closely monitor the fetal heartbeat. Rozanolixizumab is a monoclonal antibody drug that prevents a mother’s antibodies from crossing the placental barrier by blocking FcRn receptors on the placenta. In addition to blocking placental transfer, this drug reduces autoantibody levels in the mother. During treatment, the researchers report, the autoantibody levels of the mother in the study dropped by more than half. Use of rozanolixizumab was granted under federal compassionate drug use protocols. The mother had already experienced two pregnancies complicated by congenital heart block. One baby died before birth and the other required a pacemaker shortly after birth. Researchers say study results were encouraging. The baby, a girl, was delivered at 37 weeks and weighed 6 pounds, 6 ounces (2.89 kilograms). The baby had no heart complications. The mother had no serious side effects. “This single-patient study suggests the feasibility and safety of using rozanolixizumab to prevent congenital heart block in the offspring of pregnant women who are at high risk of passing along the potentially devasting autoantibodies that associate with fetal disease,” said study lead investigator Philip Carlucci, MD. Carlucci is a rheumatology fellow and Colton Center for Autoimmunity – Briedenbach Scholar in the Department of Medicine at the NYU Grossman School of Medicine. “Our research offers proof-of-concept data in support of the hypothesis that no autoantibodies equals no congenital heart block,” said study senior investigator Jill Buyon, MD, the Sir Deryck and Lady Va Maughan Professor of Rheumatology at the NYU Grossman School of Medicine.” Buyon is also the director of the Lupus Center at NYU Langone. Buyon says the study’s promising results have already prompted the National Institutes of Health’s Office of Autoimmune Disease Research to partner with the National Institute of Arthritis and Musculoskeletal and Skin Diseases to fund a multicenter trial. The investigation will be led by Buyon and study co-investigators Bettina Cuneo, at the University of Arizona in Tucson, and Justin Brandt, MD, director of maternal fetal medicine at NYU Langone and an associate professor in the Department of Obstetrics and Gynecology at the NYU Grossman School of Medicine. Called AVERT (Atrioventricular Block Elimination with Rozanolixizumab Therapy), the new investigation will enroll pregnant women who have already had a child with congenital heart block and assess whether rozanolixizumab prevents deveopment of the disease. Rozanolixizumab is currently approved by the Food and Drug Administration for treatment of myasthenia gravis, a disease that leads to muscle weakness. Carlucci, Philip M. et al., Blocking the neonatal Fc receptor as a novel approach to prevent cardiac neonatal lupus: a proof-of-concept study, Annals of the Rheumatic Diseases, DOI: 10.1016/j.ard.2025.09.011