Is fremanezumab (erenumab) safe to use during lactation (breastfeeding)?

Fremanezumab Use During Lactation

There is insufficient data on fremanezumab safety during breastfeeding, but based on its properties as a monoclonal antibody, it can likely be used with caution while breastfeeding.

Current Evidence on Fremanezumab in Lactation

The FDA label for fremanezumab (AJOVY) explicitly states: "There are no data on the presence of fremanezumab-vfrm in human milk, the effects on the breastfed infant, or the effects on milk production" 1. This represents the most direct information available on this specific medication.

Monoclonal Antibodies and Breastfeeding

Fremanezumab is a fully humanized IgG2Δa/kappa monoclonal antibody that targets calcitonin gene-related peptide (CGRP) 1. When considering its use during lactation, several important factors should be considered:

1. Similar biologics are considered compatible with breastfeeding:

   • The 2020 American College of Rheumatology guidelines strongly recommend TNF inhibitors (which are also monoclonal antibodies) as compatible with breastfeeding 2
   • The same guidelines conditionally recommend other non-TNF inhibitor biologic agents (including several monoclonal antibodies like rituximab, belimumab, tocilizumab, secukinumab, and ustekinumab) as compatible with breastfeeding 2

2. Properties of monoclonal antibodies that favor safety in breastfeeding:

   • Large molecular weight (fremanezumab is approximately 148 kDa) 1
   • Limited oral bioavailability (would be poorly absorbed by the infant's GI tract)
   • Likely to be degraded in the infant's digestive system

Decision-Making Algorithm for Fremanezumab Use During Lactation

1. Assess maternal need for treatment:

   • Determine if migraine severity warrants medication use
   • Consider if alternative treatments with more established lactation safety profiles are appropriate

2. Consider infant factors:

   • Age of infant (younger infants, especially <6 weeks, require more caution) 3
   • Health status of infant (premature or ill infants may be more vulnerable)

3. Implement risk minimization strategies:

   • Monitor infant for any unusual symptoms
   • Consider timing administration to minimize exposure (though less relevant with monoclonal antibodies due to long half-life)

Important Considerations and Caveats

• Benefits of breastfeeding: The FDA label acknowledges that "the developmental and health benefits of breastfeeding should be considered along with the mother's clinical need for AJOVY and any potential adverse effects on the breastfed infant" 1

• Theoretical minimal risk: As a monoclonal antibody, fremanezumab likely has:

  • Limited transfer into breast milk
  • Poor oral bioavailability in the infant
  • Degradation in the infant's digestive system

• General principle: The 2025 EULAR recommendations emphasize that "given the benefits of breastfeeding, women should not be discouraged from breastfeeding while taking compatible medications" 2

Conclusion

While direct evidence on fremanezumab use during lactation is lacking, its properties as a monoclonal antibody and the safety profile of similar biologics suggest it can likely be used with caution during breastfeeding. The benefits of treating maternal migraine and enabling continued breastfeeding may outweigh the theoretical minimal risks to the infant. Close monitoring of the infant is recommended, and consultation with the infant's pediatrician is advised.