STAT+: Drug meant to make gene therapy safer may also make it less effective

STAT PlusBiotech Drug meant to make gene therapy safer may also make it less effective Study of Dravet syndrome patients could raise concerns for Sarepta, Regenxbio and others Manage alerts for this article Email this article Share this article By Jason MastMay 13, 2026 General Assignment Reporter Jason Mast[email protected]Jason is a general assignment reporter, with particular focus on genetic medicine and rare disease. Confidential tips can be sent on Signal at JasonMast.77. 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. Advertisement 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. STAT+ Exclusive Story Already have an account? Log in This article is exclusive to STAT+ subscribers Unlock this article — plus daily coverage and analysis of the biotech sector — by subscribing to STAT+. Already have an account? Log in Monthly $39 Totals $468 per year $39/month Get Started Totals $468 per year Starter $30 for 3 months, then $399/year $30 for 3 months Get Started Then $399/year Annual $399 Save 15% $399/year Get Started Save 15% 11+ Users Custom Savings start at 25%! Request A Quote Request A Quote Savings start at 25%! 2-10 Users $300 Annually per user $300/year Get Started $300 Annually per user View All Plans To read the rest of this story subscribe to STAT+. Subscribe Log In CRISPR, gene editing, Gene therapy, rare diseases, STAT+ Submit a correction requestReprints Jason Mast General Assignment Reporter Jason is a general assignment reporter, with particular focus on genetic medicine and rare disease. Confidential tips can be sent on Signal at JasonMast.77. Newsletter Your morning rundown of the science, politics, and money driving biotech today Recommended Matt's Take May 12, 2026 STAT Plus: Why Marty Makary was the worst FDA commissioner in 25 years Politics May 12, 2026 STAT Plus: Makary departs FDA amid turmoil as Diamantas, agency’s top food official, steps in Advertisement The Readout May 12, 2026 STAT Plus: Hims’ sales miss as telehealth competition grows Biotech May 12, 2026 STAT Plus: Capsida says it still doesn’t know what caused gene therapy death The Readout May 11, 2026 STAT Plus: Astellas treatment offers new hope to a devastated rare disease community Subscriber Picks