Treating MS With Rituximab May Be Safe During Pregnancy and Breastfeeding

Although rituximab does not carry an indication for the treatment of neurological disorders, the drug is widely used off-label as a therapy for B-cell–mediated disorders like multiple sclerosis (MS). Given the fact that rituximab has not been approved in these indications, however, data that reflect its safety and efficacy—particularly in patient populations for whom data are particularly scarce—are crucial.
Kelly Davio
March 18, 2019
Although rituximab does not carry an indication for the treatment of neurological disorders, the drug is widely used off-label as a therapy for B-cell–mediated disorders like multiple sclerosis (MS). The approval of the first US-licensed biosimilar rituximab, Truxima, in 2018, has the potential to make this high-cost treatment option available to more patients, both in its approved indications in oncology and in such off-label applications as the treatment of MS.

Given the fact that rituximab has not been approved in these indications, however, data that reflect its safety and efficacy—particularly in patient populations for whom data are particularly scarce—are crucial. During the upcoming Academy of American Neurology meeting, which will be held May 4-10 in Philadelphia, Pennsylvania, multiple researchers will present on the use of rituximab in patients with MS who are pregnant or breastfeeding.

First, Jessica Rice, MD, of the Oregon Health and Science University in Portland, Oregon, will present a case series in which patients with MS had increased disease activity during pregnancy, although the usual rate of MS relapse typically declines during pregnancy, and many pregnant patients stop taking disease-modifying therapy given concerns about safety.1

In these 2 cases, patients experienced disabling symptoms, and there was concern about further relapses during pregnancy, so the patients were treated with rituximab after risk/benefit considerations.

The first patient, who was treated with rituximab during the third trimester, showed improvement over several weeks, and her infant was born at term without complications. The second patient was treated with rituximab in the early second trimester and has also shown improvement. This patient was in the third trimester at the time of the abstract submission, but no complications had been identified up to that date.

Rice concluded that treating aggressive MS with rituximab during pregnancy has risks, but the drug may be safe and effective when used in an appropriate context.

Researchers from the University of California, San Francisco’s Department of Neurology will report on the concentration of rituximab in the breastmilk of breastfeeding patients with MS. Currently, write the researchers, women with MS have a high risk of postpartum relapse, but due to a lack of data, the standard of care is for them to choose between breastfeeding and resuming MS treatment.2

In the single-center study, the researches collected 6 samples of breast milk from 4 lactating patients who were receiving rituximab. The samples were analyzed using an enzyme-linked immunosorbent assay. The researchers detected only minimal concentrations of rituximab in the samples.

Although the sample size was small, this largest-to-date study of rituximab concentration in breast milk establishes the need for a larger longitudinal study that includes infant outcome measures.

References
1. Rice J. Rituximab for treatment of aggressive multiple sclerosis during pregnancy: a case study. Presented at: 2019 Academy of American Neurology Annual Meeting, May 4-10, 2019; Philadelphia, PA. Abstract P4.2-103.
2. LaHue S, Krysko K, Rutatangwa A, et al. Minimal concentrations of rituximab in the breastmilk of women treated for multiple sclerosis. Presented at: 2019 Academy of American Neurology Annual Meeting, May 4-10, 2019; Philadelphia, PA. Abstract P4.2-097.

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