I have been on Tysabri for 2 relapse free years. Now I want to try for another baby. I was advised to gradually lengthen the intervals between the infusions. So my last three infusions were every 8 weeks. Are there any studies suggesting this approach will prevent rebound activity?
This is one of many unproven approaches that neurologists use to avoid rebound during pregnancy after discontinuation of Tysabri: The idea is to continue Tysabri during pregnancy, administered less frequently, but avoid administering in the 3rd trimester when the maximum protective effects of pregnancy on your MS takes hold. Remember, Tysabri will not cross the placenta during the first trimester of pregnancy. Once the the baby is delivered, tysabri is restarted. The rationale is that it usually takes more than 3 to 6 months off of tysabri for disease activity to return and pregnancy itself increasingly reduces the risk of relapse during the second and especially the third trimester.
It is important to note that not all people have an equal chance of relapsing after stopping Tysabri. Relapses after stopping Tysabri are more common in people with frequent relapses (more than 1 a year) or frequent MRI activity before starting Tysabri. Overall, about 1/3 of patients experience a relapse after stopping Tysabri and about 10 % or less experience rebound (an increase in disease activity compared to their activity before starting Tysabri). This disease activity can usually be controlled with steroid treatments but there are some potential risks of steroids during pregnancy that must be balanced against the risk of Tysabri.
There are now several observational studies of exposure to Tysabri during pregnancy and no evidence of an increased risk of fetal malformation or other problems. There is some evidence that exposure to Tysabri during the third trimester increasing the risk of newborns experiencing low platelet counts and anemia and this must be understood by your obstetrician.
I hope this information helps. We (you) often have to make decisions in medicine in the absence of the ideal amount of information. Go over all this information with your doctor to make sure you are comfortable with the choice you make. If you are not in a hurry to get pregnant, there are several other choices to consider that involve switching to another DMT. Depending on your circumstances, switching to Rituximab or Ocrelizumab prior to pregnancy is one such choice. This could be administered before pregnancy with benefits lasting through pregnancy. Generally, there is no information that switching to any other DMTs after stopping Tysabri prevents rebound and most of these other DMTs (except interferons and copaxone) are small molecules that can easily cross the placenta in the first trimester and should be avoided.
Revere (Rip) Kinkel MD
Director of the Multiple Sclerosis Program
Director of Hillcrest Neurology
Professor of Clinical Neurosciences
University of California San Diego