Summary Safety Review - TYSABRI (natalizumab) - Blood (hematological) Abnormalities in Newborns whose Mothers were treated with Tysabri During Pregnancy

Review decision

A Summary Safety Review complements other safety related information to help Canadians make informed decisions about their use of health products. Each summary outlines what was assessed in Health Canada’s review, what was found and what action was taken by Health Canada, if any.


Issued: 2017-06-22

Product

Tysabri (natalizumab)

Potential Safety Issue

Blood (hematological) abnormalities in newborns whose mothers were treated with Tysabri during pregnancy.

Key Messages

  • Tysabri (natalizumab) is authorized for sale in Canada to treat patients with the relapsing-remitting form of multiple sclerosis (MS).
  • Health Canada reviewed the potential risk of blood abnormalities in newborns whose mothers were treated with Tysabri during pregnancy following the publication of reports of newborns having lower numbers of red blood cells (anemia) and platelets (thrombocytopenia) and higher numbers of white blood cells (leukocytosis).
  • Health Canada's safety review concluded that there is a potential for blood abnormalities in newborns whose mothers were treated with Tysabri during pregnancy. Since the completion of this review, the Canadian product information for Tysabri has been updated to reflect this potential risk in newborns.

Overview

Health Canada conducted a review of the potential risk of blood abnormalities in newborns whose mothers were treated with Tysabri during pregnancy. The review included reports provided by the manufacturer and from published literature. Blood (hematological) abnormalities have been reported in adult patients treated with Tysabri and this was already written in the product information.

Use in Canada

  • Tysabri (natalizumab) is authorized for sale in Canada to treat patients with the relapsing-remitting form of multiple sclerosis (MS). Tysabri is generally recommended for MS patients who have not responded well to other treatments or who are unable to tolerate them.
  • Tysabri belongs to a family of medicines called monoclonal antibodies. It prevents active immune cells from reaching the brain where they can cause the inflammation and the nerve damage seen in MS.
  • Tysabri has been marketed in Canada since 2006. Tysabri is given into a vein (intravenously) and is available by prescription only.
  • At the time of this review, the Canadian product information for Tysabri included the risk of blood abnormalities in adult patients.

Safety Review Findings

  • At the time of the review, Health Canada had received, from the manufacturer, 15 reports of blood abnormalities in newborns whose mothers were treated with Tysabri during pregnancy. None of the reports were from mothers treated in Canada.
  • It was determined that in 14 of the 15 reports the abnormalities in the newborns' blood was potentially related to the Tysabri treatment, while the remaining 1 case could not be assessed due to missing information. The blood abnormalities included having lower numbers of red blood cells (anemia) and platelets (thrombocytopenia) and higher numbers of white blood cells (leukocytosis).
  • In 3 of the 15 cases it was reported that the newborns' umbilical cord blood was found to contain Tysabri. This suggests that Tysabri can cross from the mother's blood into the fetus and may contribute to a blood abnormality in the newborn.

Conclusions and actions

  • Health Canada's safety review concluded that there is a potential for blood abnormalities to happen in newborns whose mothers were treated with Tysabri during pregnancy.
  • Since the completion of the review, the Canadian product information has been updated to reflect this potential risk.
  • Health Canada will continue to monitor safety information involving Tysabri, as it does for all health products on the Canadian market, to identify and assess potential harms. Health Canada will take appropriate and timely action if and when any new health risks are identified.

Additional information

The analysis that contributed to this safety review included scientific and medical literature, Canadian and international information and what is known about the use of this product both in Canada and internationally.

For additional information, contact the Marketed Health Products Directorate.

Date modified: