To determine the transfer of galcanezumab, a monoclonal antibody to calcitonin gene-related peptide (CGRP) used for migraine prevention, into breast milk.

Migraine is the most common cause of disability among women of reproductive age. While migraines often remit in the second and third trimesters of pregnancy, they commonly reappear postpartum. Limited data on the safety of lactation on migraine medication may result in undertreating migraine or unnecessary breastfeeding avoidance. 

Breast milk samples were collected from four women (2 weeks-9 months postpartum) on galcanezumab for migraine. Breast milk was sampled at serial time points before and after galcanezumab injection at two clinical sites, the University of California, San Francisco (UCSF) and the University of California, San Diego (UCSD). Galcanezumab concentration was measured by antibody-specific ELISA. Mothers were surveyed on breastfeeding practices and completed Ages and Stages Questionnaires (ASQ-3).

Women were on average 30.9 years old (range 24.8-35.4) and held a migraine diagnosis for 11.8 years (range 4-25). All women breastfed their infants while taking galcanezumab. ASQ-3 scores were normal for the UCSF participants at 6 and 12 months. All galcanezumab concentrations in mature breast milk samples were less than 4.5 ug/mL. Further testing of galcanezumab concentrations in breast milk will be repeated, as well as a calculated relative infant dose.  

Monoclonal antibodies used in other neurological conditions (such as rituximab, ocrelizumab) have previously shown low transfer into breast milk. An oral CGRP receptor antagonist, rimegepant, has a low RID in human breast milk; until this study, no published data were available on the transfer of galcanezumab, an injectable CGRP monoclonal antibody, into human breast milk. Understanding the transfer into breast milk of highly effective migraine therapies such as galcanezumab is crucial to providing women safe, effective treatments for headaches, especially during the postpartum period when at high risk of migraine recrudescence.