Ocrevus (ocrelizumab) is a medication used to treat multiple sclerosis (MS), specifically relapsing forms and primary progressive MS. When it comes to pregnancy, the safety of Ocrevus is a complex and nuanced topic because it involves balancing the health needs of the mother with potential risks to the developing fetus.
Ocrevus is a humanized monoclonal antibody that targets CD20-positive B cells, which are part of the immune system. Because it is an immunoglobulin G1 (IgG1) antibody, it can cross the placenta during pregnancy. This means that the drug can reach the fetus, especially during the second and third trimesters when placental transfer of antibodies is more pronounced.
There is limited data on the use of Ocrevus specifically in pregnant women. Clinical trials have not adequately studied its effects on fetal development, so the full risks are not well established. However, studies with similar anti-CD20 therapies (like rituximab) and animal studies provide some insights. In animal studies, pregnant monkeys given doses of ocrelizumab similar to or higher than those used in humans showed increased perinatal mortality and toxic effects on the offspring’s kidneys, bone marrow, and testes, even when the mother did not show toxicity. This suggests potential risks to fetal development and survival.
In infants born to mothers exposed to anti-CD20 antibodies during pregnancy, transient depletion of peripheral B cells and lymphocytopenia (a reduction in lymphocytes, a type of white blood cell) have been reported. This B-cell depletion could affect the infant’s immune system, potentially impacting how well vaccines work and increasing vulnerability to infections. Because of this, live or live-attenuated vaccines are generally avoided in these infants until their B-cell levels recover.
Despite these concerns, some observational data from women with MS who used anti-CD20 therapies during pregnancy show no relapses of MS during pregnancy, indicating that the medication can be effective in controlling disease activity during this time. However, the long-term safety for the child remains uncertain.
The general background risk of major birth defects in the population is about 2% to 4%, and miscarriage risk is about 15% to 20%. It is unknown how much Ocrevus might increase these risks, if at all.
Because of the potential risks, the current clinical approach often involves careful planning around pregnancy. Some recommendations include:
– Using Ocrevus before pregnancy and stopping it well in advance to allow the drug to clear from the body before conception.
– Avoiding use during pregnancy unless the benefits to the mother outweigh the potential risks to the fetus.
– Monitoring infants born to mothers exposed to Ocrevus for immune system function and delaying live vaccines until immune recovery is confirmed.
Women with MS who are considering pregnancy or become pregnant while on Ocrevus should have detailed discussions with their healthcare providers. The decision to continue or stop treatment involves weighing the risk of MS relapse against potential fetal risks. In some cases, alternative therapies with more established pregnancy safety profiles may be considered.
In summary, Ocrevus is not clearly established as safe during pregnancy due to limited human data and evidence of potential risks from animal studies and related drugs. It can cross the placenta and may cause temporary immune suppression in the newborn. Careful management and individualized decision-making are essential for women with MS who are pregnant or planning to become pregnant while on Ocrevus.
