The FDA has again paused Regenxbios RGX-121 gene therapy trial for Hunter syndrome after small, asymptomatic masses were found on the spines of five patients. Regenxbio does not expect to resubmit its biologics license application for the therapy in the near term.
The spine findings, either a small nodule or cystic mass, surfaced through an expanded MRI monitoring plan Regenxbio adopted a few months ago, according to an Aug. 24 news release. All five patients received intracisternal or intraventricular RGX-121 three to six years ago, remain asymptomatic and have shown stability to improvement on neurocognitive assessments. Investigators consider the findings nonserious and likely benign, though no pathological evidence confirms their cause.
The pause comes seven months after Regenxbio disclosed that a boy who received its similar MPS I therapy, RGX-111, developed a brain tumor, a case researchers have since linked to AAV gene therapy, the vector platform used in most gene therapies over the past 20 years.
The FDA placed RGX-121 on clinical hold in January alongside RGX-111, after the RGX-111 brain tumor was found. The agency then rejected the RGX-121 application in February, citing the hold among other trial and safety concerns.
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