A new study suggests B-cell depleting anti-CD20 monoclonal antibodies (mAbs) such as ocrelizumab may be safe when used before or during the first trimester of pregnancy and/or during lactation. Anti-CD20 mAbs do not seem to have a depleting effect on the physiological B-cell development in exposed infants. Exposure in the second or third trimester can lead to B-cell depletion.

B-cell-depleting therapies are widely applied in hemato-oncological and auto-immune diseases such as MS and NMOSD. Rituximab even features among the 10 most used mAbs overall. However, data on the reduction of B-cells in newborns after different exposure windows before or during pregnancy or breastfeeding are extremely scarce. As a result, anti-CD20 mAbs have a very conservative label regarding pregnancy. This is very impractical in daily practice and increases the risk of disease progression in the mother.

Prospective data, presented by Dr. Carolin Schwake (Ruhr-University Bochum, Germany), included results from 44 infants (22 girls and 22 boys) who were exposed to anti-CD20 mAbs before or during pregnancy and the lactation period, or only during lactation. B-cell counts and adverse effects were analyzed from the 44 infants.

Results indicated that 41 infants were exposed before or during pregnancy (33 to ocrelizumab, 6 to rituximab) and during lactation (1 rituximab, 3 ocrelizumab). On average, there were 49.6 days between exposure and the last menstrual period in the 33 women who were exposed to an anti-CD20 mAb before pregnancy and 44 days in 8 women who took the medication during pregnancy. B-cell analysis was done on average 19 days postpartum. Mean postnatal B-cell values were within the normal range (782.6 ± 440.7/µl; 15.9 ± 6.8%). In 2 cases, ocrelizumab exposure in the second and third trimesters of pregnancy resulted in complete B-cell depletion, but complete repopulation was seen after 2 months of follow-up. There were no congenital malformations or severe infections during the first year of life. In 3 cases, exposure was limited to lactation (1 ocrelizumab, 2 ofatumumab). This had no effect on the B-cell count of the infants (1,121.7/µl ± 50.5).

Dr. Schwake concluded that active attempts of conception can be planned shortly after infusion/injection of anti-CD20 mAb. In the second or third trimester, these drugs can cross the placenta and result in B-cell depletion in the infant. During this period, exposure should therefore be monitored and live vaccines postponed.

  1. Schwake C. Effects of anti-CD20 therapies on infant health and physiological B-cell development if administered before or during pregnancy and/or lactation. Abstract O036, ECTRIMS 2022, Amsterdam, 26–28 October, the Netherlands.

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