Blocking the neonatal Fc receptor as a novel approach to prevent cardiac neonatal lupus: a proof-of-concept study.

Objectives: Novel biologic agents targeting the neonatal Fc receptor (FcRn) offer a promising strategy to prevent cardiac neonatal lupus (cardiac-NL) in pregnant patients with high-titre anti-SSA/Ro52 kD or 60 kD autoantibodies via dual effects: reducing serum immunoglobin G (IgG) levels and inhibiting placental transfer. This study was initiated to assess the feasibility of FcRn blockade as prophylactic therapy for recurrent cardiac-NL.

Methods: A 34-year-old pregnant patient with systemic lupus erythematosus and 3 prior consecutive pregnancies complicated by neonatal lupus (1 cutaneous, 1 fatal cardiac-NL at 20 weeks, 1 cardiac-NL delivered at 32 weeks and neonatal cutaneous NL), each despite hydroxychloroquine 400 mg daily, was treated with weekly subcutaneous infusions of 560 mg rozanolixizumab (humanised IgG4 monoclonal antibody against FcRn) from gestational weeks 14 to 28 (to cover the vulnerable period of fetal cardiac injury) through a compassionate use designation. The patient performed home fetal heart rhythm monitoring thrice daily with weekly echocardiograms.

Results: Maternal anti-SSA/Ro52 kD and 60 kD autoantibodies, total IgG, and subclasses IgG1, 2, 3 decreased by about 65% at gestational week 22, with a return to near baseline levels by week 34. The pregnancy was uncomplicated, resulting in a spontaneous vaginal delivery of a healthy neonate at 37 weeks. At delivery, cord blood and maternal IgG levels were normal, obviating the need for rescue intravenous immune globulin. The neonate had a normal echocardiogram and electrocardiogram but developed a rash consistent with neonatal lupus at 5 weeks of life. There were no serious adverse events.

Conclusions: The successful application of FcRn blockade to prevent recurrent cardiac-NL sets a precedent for a multicentre study.