VALENCIA, Spain—Nipocalimab may be beneficial for pregnant women who are at high risk of early-onset severe hemolytic disease of the fetus and newborn (HDFN), according to results from the phase 2 UNITY study presented for the first time at the 20th World Congress in Fetal Medicine by Kenneth J. Moise Jr., MD, who helped design the study. 

The treatment was well tolerated by both mothers and infants and was not associated with unusual infections despite lowering immunoglobulin G (IgG) by 80% to 85% during pregnancy. Moreover, serious adverse events associated with the treatment were generally consistent with pregnancy conditions, HDFN outcomes, and gestational age at birth.

In terms of efficacy, more than half (54%) of the participants did not need any intrauterine transfusions despite a history of early-onset severe HDFN. Of these, the majority (86%) needed neither intrauterine transfusions nor transfusions for their neonates.

A little less than half (46%) of participants needed an intrauterine transfusion at a median gestational age of 271/7 weeks at first transfusion overall and 281/7 weeks for those with live births. In those with live births, none required intrauterine transfusion before 24 weeks.

Dr. Moise said intrauterine blood transfusion has been the only effective treatment option for HDFN for more than 30 years. If approved, nipocalimab would be the first nonsurgical intervention for pregnancies at high risk of HDFN.

Kenneth J. Moise Jr., MD, speaks at the 20th World Congress in Fetal Medicine in Valencia, Spain. (Photo by Larry Luxner)

The multicenter, open-label study sponsored by Janssen Research & Development enrolled 14 women, ages 18 and above, at 19 study locations worldwide. Participants received once-weekly intravenous infusions of nipocalimab and 13 of the babies were already born.

“The phase 2 nipocalimab safety and efficacy findings support favorable benefit/risk in early-onset severe HDFN and a recommended phase 3 dose regimen of 45 mg/kg/week intravenously,” said Dr. Moise, the lead investigator on the phase 2 study. He is a professor in the department of women’s health and director of the Comprehensive Fetal Care Center at Dell Medical School at the University of Texas in Austin.

Janssen recently opened a pivotal phase 3 randomized, placebo-controlled, double-blind, multicenter study to evaluate the safety and efficacy of nipocalimab in pregnancies at risk for severe HDFN. The trial is not yet recruiting participants but researchers plan to test the treatment on 120 participants starting on December 29, 2023.

Nipocalimab is an investigational monoclonal antibody that is thought to selectively block the neonatal Fc receptor to reduce levels of circulating IgG antibodies that are associated with many conditions, including HDFN. It is also being studied as a treatment for rare autoantibody diseases, including myasthenia gravis.

HDFN is a rare condition that occurs when maternal red blood cells or blood group antibodies cross the placenta and cause the red blood cells of the fetus to be destroyed, leading to severe anemia.


Moise K. Treatment with anti-neonatal Fc receptor monoclonal antibody. Oral presentation at: 20th World Congress in Fetal Medicine; June 26, 2023; Valencia, Spain.

A study to evaluate the safety, efficacy, pharmacokinetics and pharmacodynamics of M281 administered to pregnant women at high risk for early onset severe hemolytic disease of the fetus and newborn (HDFN). February 15, 2019. Updated May 31, 2023. Accessed June 26, 2023.

A study of nipocalimab in pregnancies at risk for severe hemolytic disease of the fetus and newborn (HDFN) (AZALEA). June 22, 2023. Accessed June 26, 2023.

New phase 2 data demonstrate potential benefit of nipocalimab for pregnant individuals at high risk of early-onset severe hemolytic disease of the fetus and newborn (HDFN). News release. The Janssen Pharmaceutical Companies of Johnson & Johnson; June 26, 2023.

A Clinical Trial for the treatment of HDFN is currently in the planning stage. Click to learn more.