BOSTON — A medicine increasingly used to mitigate the risk of deadly gene therapy side effects could also blunt the therapy’s effectiveness, a new study finds.
The trial, from the startup Encoded Therapeutics, tested a gene therapy for Dravet syndrome, a severe form of genetic epilepsy. A key concern in gene therapy trials is that patients could mount an immune response against the engineered viruses used to deliver new genes into the brain.
In the study, Encoded assigned most of the 21 children in the trial to receive steroids, the most commonly used immune suppressant. A subset — including most of the patients on the highest dose level — were assigned to also receive sirolimus, also known as rapamycin, a drug historically given to prevent rejection in transplant recipients.

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