No information is available about crizanlizumab during breastfeeding. Because crizanlizumab is a large protein molecule with a molecular weight of about 146,000 Da, the amount in milk is likely to be very low. It is also likely to be partially destroyed in the infant's gastrointestinal tract and absorption by the infant is probably minimal. Waiting for at least 2 weeks postpartum to resume therapy may minimize transfer to the infant.[1] Until more data become available, crizanlizumab should be used with caution during breastfeeding, especially while nursing a newborn or preterm infant.