EMA’s safety committee, PRAC, has concluded that there is no evidence linking the viral vector in Zynteglo to a blood cancer known as acute myeloid leukemia (AML).

The European Medicines Agency’s (EMA’s) Pharmacovigilance Risk Assessment Committee (PRAC) has concluded that there is no evidence linking the viral vector in Zynteglo to a blood cancer known as acute myeloid leukemia (AML). The findings were released in a July 9, 2021 press release.

Two cases of AML in patients treated with an investigational medicine, bb1111, in a clinical trial for sickle cell disease were reviewed by PRAC. The investigational medicine and Zynteglo both use the same viral vector to deliver a working gene to blood cells and there were initial concerns that the viral vector was implicated in the development of AML.

Through its review, PRAC found that the viral vector was unlikely to be the cause of cancer. After examining all the evidence, PRAC concluded that there were more plausible explanations for AML cases, such as the conditioning treatment patients receive to clear out bone marrow cells and the higher risk of blood cancer in people with sickle cell disease.

As patients receiving Zynteglo also undergo conditioning treatment to clear out bone marrow cells, PRAC has recommended that healthcare professionals explicitly inform patients of an increased risk of blood cancers from medicines used in conditioning treatments. Additionally, PRAC has updated its recommendations for monitoring patients so that any potential signs of blood cancers are checked for on a yearly basis for 15 years. However, it was concluded that the benefits of Zynteglo continue to outweigh the risks.

Zynteglo is a one-time treatment for beta thalassemia, a blood disorder, in patients 12 years and older who require regular blood transfusions. The treatment received conditional marketing authorization in May 2019 and all new evidence will continue to be reviewed by EMA as it becomes available.