FDA Suspends Regenxbio Gene Therapy Trials over Safety

The FDA suspends two Regenxbio gene therapy trials over safety concerns after a study participant developed a brain tumor.

The U.S. Food and Drug Administration (FDA) have placed a clinical hold on two gene therapy trials conducted by biotechnology company Regenxbio. The suspension was triggered by a serious adverse event in which a participant in an early-stage trial for Hurler syndrome developed a brain tumor. The hold also affects a late-stage trial for Hunter syndrome, a therapy that was nearing potential FDA approval.

Regulators are investigating whether the tumor is directly linked to the adeno-associated virus (AAV) vector used by Regenxbio to deliver its genetic medicine. The FDA has paused all dosing in the affected studies and is requiring a comprehensive safety review before any further patient enrollment or treatment can proceed. This action represents a significant setback for Regenxbio's lead pipeline programs.

"The safety of every participant is our utmost priority. We are working closely with the FDA to investigate this event thoroughly," said a Regenxbio spokesperson. An independent gene therapy safety expert commented, "While AAV vectors are generally considered safe, this event will trigger a rigorous industry-wide re-examination of long-term oncogenic risk."

The suspension highlights a critical, persistent safety concern in the rapidly advancing gene therapy field. The development of malignancies following AAV vector administration, though rare, is a theoretical risk that could have profound implications for the regulatory pathway of an entire class of medicines. The outcome of this investigation will be closely watched by developers, investors, and regulators.

Regenxbio stated it will provide further updates after its investigation and discussions with the FDA conclude. The resolution of the clinical hold and any potential changes to trial protocols will determine the future development timeline for these rare disease treatments.