Does current research indicate contraindications for Tysabri throughout pregnancy?

Here is My Question:
Does current research indicate contraindications for Tysabri throughout pregnancy?

Answer:
Pregnancy is not a contraindication to the use of Tysabri (Natalizumab). We usually advise the use of Natalizumab, as well as many other disease modifying therapies (DMTs), during pregnancy when the mother is advised of the risks involved and the physician and mother determine that the risk of stopping the DMT is greater than the risks of continuing the DMT.  

So what are the risks and how do you make this kind of decision? Here is what we know:

Risks of  exposing the developing infant to Tysabri during pregnancy:
1. A recent study of 80 plus pregnancies in the which the developing embryo was exposed to Tysabri revealed a higher miscarriage rate in the first trimester compared to a control group of pregnant women with MS exposed to interferons or no treatment. However, the rate of miscarriage was within the expected range for the general population of pregnant women.
2. There is weak data on congenital anomalies or defects in children born after exposure to tysabri. Generally this means there is not enough data yet to draw any conclusions
3. There is some data that infants exposed to tysabri in the third trimester of pregnancy may experience  temporarily hematologic abnormalities, particularly anemia and low platelet counts. The pediatrician and obstetrician need to be aware of this possibility.

Risks to the mother of stopping Tysabri before pregnancy or after learning your are pregnant:
1. Stopping Tysabri before your last menstrual cycle is associated with a large increase in the risk of relapse(s) during pregnancy (56% of patients relapsed compared to 10 % of the control group of women with MS)
2. The risk of relapses during pregnancy is reduced if tysabri is stopped after your last menstrual cycle (20% of patients relapsed compared to 10 % of the control group of women with MS)
3. The risk of disability progression and relapse is probably increased in women who do not restart Tysabri shortly after delivery.

Use this information to have further discussions with your MS specialist. Patients on Tysabri who are at highest risk of a relapse (2 relapses in the 2 years prior to starting Tysabri and an active MRI scan prior to starting tysabri) during pregnancy if they stop Tysabri to get pregnant have several options to consider (these same options could be considered for most patients on Tysabri, but the risk benefit ratio will be different):

1. Continue Tysabri during pregnancy with monitoring of the fetus. Consideration could be given to extending the dosing interval to ever 6 weeks although there is no evidence that this would reduce the risks to the developing infant. It may be wise to stop Tysabri 2 to 3 months  before delivery (the longer amount of time off, the greater the risk of relapse) and restart immediately after delivery to avoid anemia and low platelet counts in the newborn.

OR

2. Stop Tysabri before pregnancy and get one cycle of anti-CD20 treatment (Ocrevus or Rituximab),just before pregnancy to prevent relapses during pregnancy. If not pregnant within 6-12 months consider another cycle of anti-CD20 treatment at that time.

Revere (Rip) Kinkel MD
Professor of Clinical Neurosciences
Director of the Multiple Sclerosis Program
Clinical Neurosciences Director
University of California San Diego