Sarilumab and Breastfeeding

Summary of use during lactation

Because sarilumab is a large protein molecule with a molecular weight of about 150,000 Da, the amount in milk is likely to be very low.[1] It is also likely to be partially destroyed in the infant's gastrointestinal tract and absorption by the infant is probably minimal.[2] One infant was safely breastfed for 6 months after maternal sarilumab was resumed at 28 days postpartum. If sarilumab is required by the mother, it is not a reason to discontinue breastfeeding.[3] Until more data become available, sarilumab should be used with caution during breastfeeding, especially while nursing a newborn or preterm infant. Waiting for at least 2 weeks postpartum to resume therapy may minimize transfer to the infant.[4]

Drug levels in milk and infant serum

Maternal Levels. A lactating woman was receiving subcutaneous sarilumab 150 mg every 2 weeks for rheumatoid arthritis. After 5 doses of the drug, she donated 6 milk samples over a 28-day period. The peak concentration of about 160 mcg/L occurred on day 3 after the dose. By day 7, the milk sarilumab concentration decreased to about 110 mcg/L; on day 14, the milk concentration was about 75 mcg/L. The drug was undetectable in mill at 28 days after the dose.[5] Infant Levels. Relevant published information was not found as of the revision date.

Effects in breastfed infants

A woman with rheumatoid arthritis refractory to etanercept took sarilumab 200 mg every two weeks during pregnancy until 37 weeks of gestation. She was also taking prednisolone 10 mg and tacrolimus 3 mg daily. She delivered a healthy infant at 38 weeks of gestation and breastfed her infant. Prednisolone was continued postpartum; tacrolimus was restarted at 7 days postpartum and sarilumab was restarted at 28 days postpartum. The mother continued to breastfeed until 6 months postpartum. The infant was vaccinated with multiple live vaccines after reaching six months old, including the Bacille-Calmette-Guerin vaccine, with no adverse effects.[6]

Effects on lactation and breastmilk

Relevant published information was not found as of the revision date.

Alternative drugs to consider

(Rheumatoid Arthritis) Adalimumab, Certolizumab Pegol, Etanercept, Infliximab, Tocilizumab

References

1. Stratigakis A, Paty D, Zou P, et al. A regression approach for assessing large molecular drug concentration in breast milk. Reprod Breed 2023;3:199–207. doi:10.1016/j.repbre.2023.10.003
2. Anderson PO. Monoclonal antibodies during breastfeeding. Breastfeed Med 2021;16:591–3.33956488 PubMed
3. Rüegg L, Pluma A, Hamroun S, et al. EULAR recommendations for use of antirheumatic drugs in reproduction, pregnancy, and lactation: 2024 update. Ann Rheum Dis 2025.40287311 PubMed
4. Krysko KM, Dobson R, Alroughani R, et al. Family planning considerations in people with multiple sclerosis. Lancet Neurol 2023;22:350–66.36931808 PubMed
5. Saito J, Yakuwa N, Hosokawa Y, et al. Establishment of a measurement system to evaluate breast milk transfer of biological agents using dry filter paper: A multi-institutional study. Br J Clin Pharmacol 2024;90:146–57.37548054 PubMed
6. Mizutani S, Okunishi Y, Tamada T, et al. A woman with rheumatoid arthritis who successfully delivered a healthy child with continuous administration of sarilumab throughout pregnancy. Intern Med 2023;62:633–6.35871593 PubMed