Regenxbio Shares Plunge Amid FDA Trial Suspension

Regenxbio US75901B1070

Regenxbio Inc., a biotechnology firm, is confronting a significant regulatory challenge after the U.S. Food and Drug Administration (FDA) placed a clinical hold on two of its key gene therapy programs. This action casts serious doubt on a previously anticipated approval deadline scheduled for early next year.

The agency's intervention was triggered by a serious adverse event in the trial for RGX-111, a therapy for Hurler syndrome. A five-year-old patient, who received the treatment approximately four years ago, was subsequently diagnosed with a brain tumor. Although this incident has so far been isolated to a single participant, the FDA has proactively extended the clinical hold to include the related RGX-121 program. The regulator cited the similarity of the underlying products and comparable patient risks as the rationale. A critical question now looms: can Regenxbio adequately address the FDA's safety concerns in a timely manner?

This regulatory setback comes at a pivotal moment for the company. For its candidate RGX-121, the FDA had set a Prescription Drug User Fee Act (PDUFA) target action date of February 8, 2026. This official deadline for a potential marketing decision is now highly unlikely to be met following the trial suspension, significantly clouding the drug's near-term commercial prospects.

In response, Regenxbio has stated that investigations into the cause of the tumor are ongoing and that a direct link to the gene therapy has not been established. The company is currently awaiting the FDA's formal clinical hold letter to determine the necessary steps to resolve the issue and resume trials.

The news sparked a sharp sell-off among investors. Over the past seven trading sessions, the company's stock plummeted roughly 24.19%, closing at €9.40 on Friday. This brings the share price perilously close to its 52-week low of €9.25.

Pipeline Progress and Financial Runway

Despite this major setback in its rare metabolic disease portfolio, Regenxbio continues to advance other pipeline assets. Notably, its promising candidate RGX-202 for Duchenne muscular dystrophy recently reported positive interim data. In an ongoing Phase I/II study, treated patients demonstrated a disease trajectory significantly better than expected.

Financially, the company maintains a buffer to navigate this period:
* Cash Position: $302 million in cash and equivalents (as of September 30, 2025).
* Cash Runway: Management believes these funds are sufficient to support operations into early 2027.
* Recent Earnings: The third quarter of 2025 concluded with a net loss of $61.9 million.

Several key milestones remain on the calendar for the coming year. Regenxbio aims to present initial topline data for the RGX-202 program in early Q2 2026. Furthermore, the company plans to submit a marketing application for this therapy under an FDA accelerated pathway by mid-2026.