No information is available on the clinical use of inotuzumab ozogamicin during breastfeeding. Because inotuzumab ozogamicin is a large protein molecule with a molecular weight of 168,000 Da and its active metabolite is 97% plasma protein bound, 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] Ozogamicin (N-acetyl gamma calicheamicin) is a small-molecule that causes double-stranded DNA 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 inotuzumab ozogamicin therapy for at least 2 months after the last dose.