REGENXBIO Stock Plummets 28% After FDA Hold

REGENXBIO (RGNX) stock tumbled 28% Wednesday after the FDA placed clinical holds on two gene therapy trials following a brain tumor discovery in a patient ¹.

The regulatory action threatens the company’s pipeline for treating rare genetic diseases and raises safety concerns for its lead programs nearing potential approval.

Key Takeaways

FDA halted RGX-111 and RGX-121 trials after brain tumor found
Stock fell 28% on safety concerns for gene therapy programs
Company awaits full details from FDA clinical hold letter

Market Reaction & Context

REGENXBIO shares dropped sharply in Wednesday trading, underperforming the broader biotech sector ⁴. The clinical hold affects the company’s most advanced gene therapy programs targeting ultra-rare genetic disorders.

The FDA placed holds on RGX-111 for treating MPS I (Hurler syndrome) and RGX-121 for MPS II (Hunter syndrome), citing similarities between the products ⁷. Both therapies were in Phase I/II clinical trials and represented key value drivers for the company.

Safety Concerns Emerge

The regulatory action stems from a brain tumor case discovered in a patient receiving treatment, according to reports ². Gene therapy trials face heightened scrutiny due to potential risks associated with viral vector delivery systems.

REGENXBIO has not yet received the full clinical hold letter from the FDA and awaits additional details about the agency’s specific concerns ³. The company filed a Form 8-K disclosure with the SEC regarding the material event ⁶.

Pipeline Impact

The clinical holds represent a significant setback for REGENXBIO’s rare disease portfolio. RGX-111 targets MPS I, a fatal lysosomal storage disorder, while RGX-121 addresses MPS II, another life-threatening genetic condition.

Both treatments had shown promise in early-stage trials and were considered potential breakthrough therapies for patients with limited treatment options. The development programs represent substantial investments in the company’s gene therapy platform.

Regulatory Path Forward

REGENXBIO must now work with the FDA to address safety concerns before trials can resume. Clinical holds can range from weeks to months depending on the severity of issues and the company’s response to regulatory requirements.

The company’s ability to restart the programs will depend on providing satisfactory safety data and potentially modifying trial protocols. Investors will closely monitor communications with the FDA for resolution timelines.

Conclusion

The FDA’s clinical holds on REGENXBIO’s gene therapy programs highlight ongoing safety challenges in the sector. While the company maintains other pipeline assets, the regulatory setback significantly impacts its near-term commercial prospects.

Investors should monitor the company’s response to FDA concerns and any modifications to trial protocols that may be required for program continuation.

Not investment advice. For informational purposes only.