No information is available on the clinical use of tisotumab vedotin during breastfeeding. Because tisotumab 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. Because of the potential for serious adverse reactions in the breastfed infant, the manufacturer recommends that breastfeeding be discontinued during enfortumab vedotin therapy and for 3 weeks after the last dose.