Офатумумаб

It is a human anti-CD20 monoclonal antibody used in the treatment of lymphocytic leukemia and recurrent multiple sclerosis. It is administered subcutaneously on a weekly or monthly basis.

Its extremely high molecular weight (>100,000 Da) explains the undetectable or negligible excretion observed in breast milk ^{(Witt 2025)}, since molecules larger than 800–1,000 Da do not pass into breast milk. ^{(Hale, Almas 2016, Anderson 2016)}

Its low oral bioavailability suggests that the passage to infant plasma from ingested breast milk is null or negligible ^{(Witzel 2014)}, except in premature infants and the immediate neonatal period, in which there may be greater intestinal absorption.

Twelve infants breastfed for an average of 10 months (2 to 24 months) while their mothers with multiple sclerosis were taking ofatumumab did not show any developmental problems, more infections than usual, or reactions to live attenuated virus vaccinations ^{(Witt 2025)}. In fourteen cases of exposure to ofatumumab during lactation there was no effect on B-cell counts in infants. ^{(Schwake 2022)}

Null or negligible passage into breast milk of similar monoclonal antibodies, such as adalimumab, belimumab, certolizumab, golimumab, infliximab, ipilimumab, natalizumab, rituximab, tocilizumab and ustekinumab has been confirmed. ^{(Dobson 2022, Bar-Gil 2021, LaHue 2020, Ciplea 2020, Saito 2020, 2019 y 2018, Krysko 2019, Whittam 2019, Klenske 2019, Matro 2018, Anderson 2018, Bragnes 2017, Witzel 2014, Ross 2014, Fritzsche 2012)}

No problems have been detected in infants whose mothers received other similar monoclonal antibodies such as belimumab, bevacizumab, infliximab, rituximab, tocilizumab, or ustekinumab.^{(Bar-Gil 2021, LaHue 2020, Saito 2020, 2019 and 2018, Klenske 2019, Mugheddu 2019, Krysko 2019, Matro 2018, Bragnes 2017, Hyrich 2014, Danve 2014)}

If the mother received treatment during the last weeks of pregnancy, she can start breastfeeding immediately after delivery. Avoid its use in the first two weeks after delivery: there may be a significant transfer of IgG to milk until the first 3-4 days postpartum. The manufacturer considers its use compatible with lactation. ^{(EMA 2021)}

Expert authors consider that the use of monoclonal antibodies during breastfeeding is safe or very likely to be safe. ^{(Witt 2025, Dobson 2022, Whittam 2019, Matro 2018, Anderson 2018 y 2016, Mahadevan 2017, Almas 2016, Baker 2015, Briggs 2015, Damas 2015, Witzel 2014, Pistilli 2013, van der Woude 2010)}

Given the strong evidence that exists on the benefits of breastfeeding and the development of babies and the health of their mothers, it might be appropriate to evaluate the risk-benefit of any maternal treatment, including chemotherapy, and counsel individually each mother who wishes to continue breastfeeding.^{(Koren 2013)}

See below the information of these related products:

• Maternal Cancer; Maternal Neoplasia (Unsafe. Moderate/severe adverse effects. Compatible under certain circumstances. Follow-up recommended. Use safer alternative or discontinue breastfeeding from 5 to 7 T ½ . Read Commentary.)
• Maternal Multiple Sclerosis (Fairly safe. Mild or unlikely adverse effects. Compatible under certain circumstances. Follow-up recommended. Read Commentary.)