No information is available on the clinical use of brentuximab vedotin during breastfeeding. Because brentuximab is a large protein molecule with a molecular weight of about 153,000 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] Vedotin (monomethyl auristatin E) is a small-molecule anticancer drug that might enter milk and be absorbed by the infant. The manufacturer recommends that breastfeeding be discontinued during brentuximab vedotin therapy.