VANCOUVER – Three types of drugs commonly used to treat multiple sclerosis (MS) appear to have a generally good safety profile when administered before and during early pregnancy, suggest a trio of studies reported at the annual meeting of the American Academy of Neurology.
Exposure to interferon-beta during the first trimester did not increase the risks of miscarriage, congenital anomalies, or birth weight. And although use of natalizumab led to higher odds of spontaneous abortion as compared with interferon-beta or no therapy, the absolute rate still fell within that of the general population. Pregnancies occurring weeks to years after treatment with alemtuzumab also had rates of spontaneous abortion, birth defects, and stillbirth on par with population values.
All three drugs fall in a gray area when it comes to use in pregnancy, with a Food and Drug Administration designation of category C, indicating that animal studies have shown adverse effects on the fetus and adequate, quality human data are lacking, but potential benefits may outweigh potential harms in pregnancy. The studies’ findings are therefore likely to be informative to women of reproductive age, a group disproportionately affected by MS.
Dr. Jennifer Graves
“It’s very important to collect as much data as possible about potential exposure risks with disease-modifying therapy in pregnancy,” session comoderator Dr. Jennifer Graves, a neurologist at the Multiple Sclerosis Center at University of California–San Francisco Medical Center and UCSF Benioff Children’s Hospital, San Francisco, said in an interview.
“However, all studies have the limitation of sample size,” she added. “The majority of serious adverse effects – teratogenicity, major birth defects – may be less than 1 in 500 [in frequency]. So this is something that puts all of these studies into context because we just don’t have that many pregnancies that have been exposed to some of these agents.” The method whereby miscarriages are ascertained can also influence findings.
Nonetheless, this research is critical for women and their physicians when it comes to making decisions about treatment, Dr. Graves maintained. “Although pregnancy may be protective for many women with MS, many do need treatment during their pregnancy to prevent severe relapses due to various factors. Collecting this type of information is important.”
Interferon-beta safety
In the first study, investigators led by Dr. Sandra Thiel of Ruhr University Bochum and the Heinrich Heine University Düsseldorf, both in Germany, analyzed data from the German Multiple Sclerosis and Pregnancy Registry.
Dr. Sandra Thiel
They studied pregnancies among women who had at least 12 months of postpartum follow-up. Exposure to interferon-beta (brand names Rebif, Avonex, Betaseron, and Extavia) was defined as injection of the drug at any time after the last menstrual period.
In all, 251 pregnancies exposed to interferon-beta were compared with 194 pregnancies not exposed to any disease-modifying drugs. The median duration of exposure in the former group was 32 days, indicating that most women stopped the drug soon after discovering they were pregnant, Dr. Thiel noted.
Study results, reported at the meeting and recently published (Mult Scler. 2016 Feb 26. doi: 10.1177/1352458516634872), showed that the rate of miscarriage was 9.96% in the exposed group and 7.73% in the unexposed group, and the rate of congenital anomalies among live births was 3.08% and 5.52%.
In analyses using propensity score adjustment, there were no significant differences between groups in the odds of live birth, spontaneous abortion, congenital anomalies, preterm birth, cesarean section, or small for gestational age, or in mean infant birth weight.
Of note, the women whose pregnancies were not exposed to any disease-modifying therapy had a higher rate of relapse during pregnancy when compared with counterparts whose pregnancies were exposed to interferon-beta (27.3% vs. 14.3%).
“Taken together with the existing literature, our study provides further reassurance that interferon-beta treatment can be safely continued up until the time when women with MS become pregnant,” Dr. Thiel concluded. The safety profile seen “is consistent with the pharmacologically plausible safety of interferon-beta, as interferon-beta is a huge molecule that cannot pass the placental barrier.”
“Since the vast majority of women stopped the interferon-beta treatment during the first trimester of pregnancy, we cannot draw any conclusions about the safety of interferon-beta later in pregnancy,” she cautioned. “Another limitation is the variability in the gestational week of entry into the cohort, as later than first-trimester inclusion can lead to an underestimation of early events, particularly spontaneous abortions.”
Natalizumab safety
In the second study, Dr. Maria Pia Amato, Department of NEUROFARBA, Section of Neurosciences, University of Florence, Italy, and her colleagues with the Italian MS Study Group assessed pregnancy outcomes after exposure to natalizumab (Tysabri). This antibody targets alpha-4 integrins, which play a role in a variety of pregnancy processes and in fetal hematopoiesis and cardiac development, she noted.