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Pregnancy Outcomes Mirror General Population in Women With MS Who Took Alemtuzumab


Alemtuzumab did not appear to negatively impact pregnancy outcomes in women who took the therapy for relapsing-remitting multiple sclerosis prior to becoming pregnant.

Women who took alemtuzumab (Lemtrada) before becoming pregnant were not at a higher risk of birth defects or spontaneous abortion, according to a new long-term study of women with relapsing-remitting multiple sclerosis (RRMS).

Still, the study authors said women of child-bearing age should continue to follow recommendations to use contraceptives for 4 months following alemtuzumab infusion. The results were published in the journal Multiple Sclerosis and Related Disorders.

Disease-modifying therapies have dramatically reshaped therapy for patients with MS, but the implications of those new treatments on women seeking to become pregnant are not yet fully clear.

Alemtuzumab is gone from the body approximately 30 days following infusion, but it is recommended that women of child-bearing age take contraceptives for 120 days following administration of alemtuzumab, given that animal models have suggested placental transfer during gestation and postpartum transfer through lactation are possible.

Corresponding author Jiwon Oh, MD, PhD, of the University of Toronto, and colleagues wanted to better understand the impact of alemtuzumab on women who become pregnant. To do so, they looked at the outcomes of women who were enrolled in phase 2 and 3 clinical development trials over the course of 16 years (2002-2018).

Those studies yielded a total of 264 pregnancies among 160 women who had been treated with alemtuzumab. The women had a median age of 32.6 years and, on average, became pregnant 3 years (35.9 months) after their last dose of the therapy.

Of the 264 pregnancies, 233 (88%) were completed, 11(4) were ongoing at the end of the study period, and 20 (8%) had unknown outcomes.

Most of the completed pregnancies with known results (67%) ended in live births with no congenital abnormalities or birth defects, Oh and colleagues said.

Twenty-two percent of pregnancies resulted in spontaneous abortions, and 11% resulted in elective abortions. One pregnancy resulted in a stillbirth. Women

who were older tended to be at a higher risk of spontaneous abortion, the authors said, and there was no statistically significant difference between patients who became pregnant before or after the 4-month post-exposure contraception guideline, though only 6% of pregnancies were conceived within the 4-month window. The authors said the patients’ annualized relapse rate increased modestly postpartum, to 0.22, but returned to normal rates in the second and third years following pregnancy.

The authors said the spontaneous abortion rate of 22% was comparable to that of the general public, which has a rate of 17-22% if early pregnancy losses are included.

“These reference data for the general population include early pregnancy losses, which are frequently not captured in epidemiological studies of pregnancy outcomes and depend upon early recognition of pregnancy,” they said. “Thus, these rates are an appropriate comparator for closely monitored clinical trial patients.”

Oh and colleagues said DMTs present a challenge for women who are planning to have children, but they said alemtuzumab generally has the benefit of less frequent dosing requirements.

“In contrast to DMTs with more frequent administration, the prolonged clinical effect of alemtuzumab without continuous dosing minimizes the risk for disease activity without fetal drug exposure,” they said. “With more frequently dosed DMTs, treatment discontinuation for pregnancy may carry a risk for increased disease activity before, during, or after pregnancy.”

The authors said there are a number of limitations. The number of pregnancies within 4 months of alemtuzumab administration was small, making it difficult to draw broad conclusions about those patients. It is also possible that some of the elective abortions were related to developmental abnormalities that were not tabulated in the study. Developmental defects that appeared more than a year following birth would also not be included in the study, the authors said.

Thus, while the data were broadly favorable, the authors said women on alemtuzumab should continue to follow the 4-month contraception recommendation.


Oh J, Achiron A, Celius EG, et al. Pregnancy outcomes and postpartum relapse rates in women with RRMS treated with alemtuzumab in the phase 2 and 3 clinical development program over 16 years. Mult Scler Relat Disord. 2020;43:102146. doi:10.1016/j.msard.2020.102146

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