Regenxbio Falls Most Ever After Tumor Found in Trial Participant

Regenxbio Inc. shares fell the most on record after US regulators placed a hold on the company’s gene therapy trials because a patient was found to have a brain tumor.

The US Food and Drug Administration took the action on a study of the company’s treatment for a condition called Hurler syndrome after a routine brain MRI found a 5-year-old patient in a study had a tumor, according to a Regenxbio statement. The patient had received the treatment four years ago. The company said it’s investigating whether the tumor is related to the drug.