Study finds Ultomiris safe as PNH treatment during pregnancy
No major problems for mothers, babies seen in 19 pregnancies
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Ultomiris (ravulizumab-cwvz) may be safe and effective as a treatment for paroxysmal nocturnal hemoglobinuria (PNH) in pregnant women, a study suggested.
Of 19 pregnancies in women treated with Ultomiris, all resulted in live births, compared with four live births out of eight pregnancies previously managed with Soliris (eculizumab), the study found.
Maternal complications that arose during pregnancy were managed with supportive care and treatment adjustments. No severe infections or major developmental problems were reported in babies during follow-up. Although very small amounts of the drug were detected in breast milk, breastfeeding was not associated with safety concerns.
Those results provide “evidence for the safety and effectiveness of [Ultomiris] in managing PNH during pregnancy and breastfeeding with favorable maternal and fetal outcomes,” the researchers wrote. They added that larger studies will be important to better understand Ultomiris’ safety profile in pregnancy and identify rare adverse outcomes that may not appear in smaller groups.
The study, “Ravulizumab for Treatment of Paroxysmal Nocturnal Hemoglobinuria During Pregnancy,” was published in Blood Advances.
Newer, longer-lasting treatment
PNH is a rare blood disorder in which overactivation of the complement system (the part of the immune system that helps fight infections) leads to the destruction of red blood cells, a process called hemolysis. This can cause low red blood cell levels (anemia) and an increased risk of life-threatening blood clots (thrombosis).
Pregnancy further raises these risks, increasing the likelihood of serious maternal complications, miscarriage, and premature birth.
Soliris, developed by Alexion Pharmaceuticals, now part of AstraZeneca, was the first therapy approved to reduce hemolysis in PNH. Given by infusions into the bloodstream, it blocks a complement protein called C5. Because its use has been linked to higher fetal survival rates, it has become the standard treatment for managing PNH during pregnancy.
Ultomiris, also developed by Alexion, is a newer PNH treatment that targets the same complement protein as Soliris but lasts longer in the body. This allows for infusions every eight weeks instead of every two. While it has largely replaced Soliris for many patients, data on its use during pregnancy remain limited.
“Understanding the safety and efficacy of current PNH therapies, such as [Ultomiris], during pregnancy is imperative,” the researchers wrote.
The team analyzed pregnancy outcomes in 16 women with PNH treated with Ultomiris at five centers in the U.S. and Europe between March 2018 and August 2025. Short-term use of Soliris was allowed when medically necessary. Alexion and AstraZeneca partially funded the study.
Altogether, the women had 27 pregnancies — 19 while on Ultomiris and eight earlier pregnancies in five women who previously received Soliris — allowing researchers to compare outcomes between the two treatments.
Women were diagnosed with PNH at a median age of 24.6 and became pregnant a median of 6.3 years later, at a median age of 30.9.
All women were receiving a complement C5 inhibitor before becoming pregnant and continued treatment during pregnancy. In some cases, doctors increased doses, added additional doses, or shortened dosing intervals to control hemolysis as pregnancy progressed. Blood thinners were used in 23 pregnancies to lower the risk of clots.
Despite treatment, episodes of hemolysis and dark-colored urine were reported in six women on Ultomiris and one on Soliris. Severe abdominal pain crises occurred in two women receiving Soliris. Red blood cell transfusions were needed in 13 women on Ultomiris and five on Soliris, most often around delivery.
Infections were reported in nine pregnancies overall. One clotting complication occurred in a woman receiving Ultomiris who had additional underlying risk factors.
Of the pregnancies in women treated with Soliris, three ended in miscarriage, and one resulted in an extremely premature birth in which the baby did not survive. In contrast, all 19 pregnancies in women treated with Ultomiris resulted in live births, including one set of twins. Most babies were born close to full term and had healthy birth weights. Three were delivered prematurely.
All women who had previously experienced pregnancy loss on Soliris later had successful full-term pregnancies while receiving Ultomiris.
A median follow-up of about 16 months showed no reports of severe infections or major developmental problems. One child had a temporary speech delay that later resolved, and another was diagnosed with an autism-spectrum language disorder.
Tests showed that Ultomiris can cross the placenta from the mother to the baby during pregnancy, and very small amounts were also detected in breast milk. These exposures were not linked to health problems, and no safety concerns were seen in breastfed babies.
“Our data suggest that, for patients with PNH receiving [Ultomiris] therapy, continuation of [Ultomiris] during pregnancy is a reasonable option,” the researchers wrote. “However, as with any pregnancy in a patient with PNH, close monitoring of maternal clinical status, markers of hemolysis, and fetal development is mandatory.”
