Gestational exposure to erenumab - the outcome of three pregnancies

Erenumab is a monoclonal antibody (mAb) approved for the preventive treatment of migraine. While preclinical studies on calcitonin gene-related peptide mAbs did not identify any reproductive toxicity, pregnant and breastfeeding women were excluded from the pivotal human studies, and therefore the safety of calcitonin gene-related peptide medications in this population must be studied. So far, postmarketing data of accidental exposures have not brought to light any specific toxicities. Three women treated with erenumab in our series conceived while exposed to the drug. All had previous successful pregnancies, were on erenumab for more than 6 months, and had ≥80% reduction in headache frequency. The one who stopped erenumab only 1 month before conceiving had a spontaneous abortion during the first trimester due to a gestational trophoblastic neoplasia and has since conceived with an uneventful gestation. The other two women stopped treatment during the first trimester, and both pregnancies went to term with no complications. All babies have shown normal development. No plausible explanation relates the mechanism of action of erenumab and the serious complication that occurred in one patient. Continuous follow-up and reporting of all exposures are encouraged to gather safety data on pregnant and nursing women and on the development of the newborns. So far, immediately stopping the drug is advised and may contribute to decreasing the potential risks.