Common MS therapies appear safe to use while breastfeeding

Taking antibody-based medications for multiple sclerosis (MS) while breastfeeding does not appear to harm a child’s health or development during at least the first three years of life, according to a preliminary study of more than 180 babies.

Children breastfed by mothers taking Tysabri (natalizumab), Ocrevus (ocrelizumab), rituximab, or Kesimpta (ofatumumab) developed normally and were as healthy as those of mothers not using any of those monoclonal antibodies for their MS, the researchers reported.

The study, “Child development after exposure to monoclonal antibodies during breastfeeding,” will be presented at the American Academy of Neurology (AAN) 2024 annual meeting, taking place April 13-18 in person in Denver and online.

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MS is two to three times more common in women than in men, and many women are of childbearing age when they’re first diagnosed with the disease. There’s evidence that pregnancy can influence the course of MS, with some studies suggesting that pregnancy may be protective.

However, women who take highly effective disease-modifying therapies (DMTs) before getting pregnant, then stop their use during pregnancy have a relapse rate after giving birth that’s nearly three times greater than before conception.

This risk could be eased if patients restart their high efficacy treatments soon after giving birth, but little is known about the safety of these medications for the breastfeeding infant.

“Most monoclonal antibody medications for multiple sclerosis are not currently approved for use while a mother is breastfeeding,” Kerstin Hellwig, MD, a neurology professor and expert in MS and pregnancy at Ruhr University in Bochum, Germany, and the study’s lead author, said in an AAN press release. “Since the risk of MS relapses increases after giving birth, some mothers may need or want to restart these therapies, so it is important to determine whether these medications, through breast milk, have a negative impact on a child’s development.”

To investigate the impact of antibody-based MS medications on a child’s overall health and development, Hellwig and her team examined data covering children born to mothers with MS using these therapies while breastfeeding. Their data came from the German MS and Pregnancy Registry, and they assessed how those children developed over their first three years of life.

183 babies with mothers breastfeeding while on DMT compared with 183 others

The study included 180 mothers with MS and three with neuromyelitis optica spectrum disease (NMOSD), a related autoimmune condition also marked by damage to myelin, the protective covering around nerve fibers that allows for efficient neuronal communication.

Their children were compared with another 183 infants born to mothers with the same diseases and matched for exposure to DMTs during pregnancy. But this group didn’t take monoclonal antibodies while breastfeeding.

Exposure to monoclonal antibodies through breast milk started at a median of 19 days into a child’s life. Some babies were exposed to the medications as early as the first day of life, while for others, a first exposure came up to nine months after birth.

Exposure lasted for a median 172 days (about 5.5 months), and it ranged from two days to three years. The most common antibody medication used while breastfeeding was Tysabri (68.3%), followed by Ocrevus (18.6%), rituximab (used off-label in MS, 6%), and Kesimpta (5.5%).

Two mothers switched from Tysabri to Ocrevus, and one from rituximab to Ocrevus while breastfeeding. Five others who had been using glatiramer acetate (sold as Copaxone and available as generics) or interferon-based medications during breastfeeding switched to a monoclonal antibody.

‘No negative effect on development or health’ seen over initial years of life

Results showed that children breastfed by mothers taking a monoclonal antibody were no more likely than other children to be admitted to the hospital or be prescribed antibiotics to treat infections during their first three years of life.

They also weren’t more likely to have developmental delays or slow weight gain, suggesting that exposure to those monoclonal antibodies through breast milk had “ no negative effect on the development or health of breastfed infants” at least for their first three years of life, the researchers wrote.

One noted study limitation was following only about one-third of these children for a full three years, meaning that further research may be needed to confirm the results for the third year of life.

The German MS and Pregnancy Registry is funded by a number of companies, including Biogen, Roche, and Novartis. Biogen has developed and sells Tysabri, Novartis markets Kesimpta, and Genentech, part of Roche, sells Ocrevus and Rituxan, the brand-name of rituximab.