REGENXBIO Inc. (NASDAQ: RGNX) announced an extension of the FDA review period for its lead gene therapy candidate, RGX-121, for Hunter syndrome. Despite this regulatory delay, the company maintains a "Buy" rating from analysts, buoyed by strong underlying clinical data and a strengthened financial position.

Regenxbio: RGX-121 FDA Review Extended Amidst Robust Clinical Data and Investor Confidence

U.S. biotechnology firm REGENXBIO Inc. (NASDAQ: RGNX) faces an extended review period for its lead gene therapy candidate, RGX-121, aimed at treating Hunter syndrome. The U.S. Food and Drug Administration (FDA) has pushed the Biologics License Application (BLA) target action date to February 8, 2026. Despite this regulatory delay, analysts maintain a "Buy" rating for RGNX, reflecting continued confidence in the therapy's underlying clinical data and the company's broader pipeline and financial strategy.

The Event in Detail

The FDA extended the Prescription Drug User Fee Act (PDUFA) target action date for RGX-121 from the original November 9, 2025. This extension was a procedural adjustment, prompted by REGENXBIO's submission of additional longer-term 12-month clinical data from the 13 patients in the pivotal study. This data was requested by the FDA to allow for more time to review the application. Crucially, the FDA completed pre-BLA inspections in August 2025 with no observations, and no safety concerns have been raised during the BLA review process, a significant positive signal for the gene therapy.

Analysis of Market Reaction

The initial market reaction to the PDUFA date extension saw REGENXBIO's stock dip approximately 7% from $8.70 to $8.10 per share on August 19, 2025. However, RGNX shares have since surged over 50% in the past six months, indicating a rebound in investor optimism. This recovery suggests that the market views the delay as a temporary procedural step rather than a fundamental flaw in the therapy or its clinical profile. Analysts largely maintain a "Buy" rating for RGNX, with price targets ranging from $14 to $52 and a consensus price target of $33.59. This consensus reflects sustained confidence in REGENXBIO's long-term prospects.

Broader Context and Implications

RGX-121 is positioned as a potential one-time gene therapy to address the underlying genetic cause of Hunter syndrome (MPS II). Its design, specifically intracerebroventricular (ICV) delivery, aims to treat both systemic and neurological manifestations of the disease, differentiating it from existing enzyme replacement therapies (ERTs) that lack central nervous system (CNS) penetration and require lifelong administration. The therapy has received multiple FDA designations, including Orphan Drug, Rare Pediatric Disease, Fast Track, and Regenerative Medicine Advanced Therapy (RMAT), which are designed to accelerate review and offer incentives.

The market for Hunter syndrome treatments is projected to grow significantly, from $1.31 billion in 2024 to $1.78 billion by 2030, driven by advancements in gene therapy and orphan drug incentives. REGENXBIO's RGX-121 aims to capture a substantial share of this expanding market.

Financially, REGENXBIO reported cash, cash equivalents, and marketable securities totaling $363.6 million as of June 30, 2025. This robust cash position, bolstered by a $110 million upfront payment from a partnership with Japan's Nippon Shinyaku and a non-dilutive royalty bond agreement of up to $250 million with Healthcare Royalty (HCRx), is projected to fund the company's operations into early 2027. This financial resilience provides a crucial buffer against regulatory delays and supports ongoing research and development.

Despite missing analyst expectations for Q2 2025 earnings, with an EPS of -$1.38 against a forecasted -$0.94 and revenue of $21.36 million against a projected $38.7 million, the company maintains a strong gross profit margin of 82.4%. The revenue decline was primarily attributed to a reduction in Zolgensma royalties.

Beyond RGX-121, REGENXBIO is advancing other promising pipeline programs, including RGX-202 for Duchenne muscular dystrophy, with pivotal trial enrollment on track for completion by October 2025 and a BLA submission slated for mid-2026. The company is also progressing with ABBV-RGX-314 for retinal diseases.

Expert Commentary

Analysts maintain a favorable outlook on REGENXBIO.

RBC Capital, for instance, maintained an Outperform rating on RGNX, despite lowering its price target from $21 to $17, citing ongoing developments across the company's pipeline.

The consensus "Buy" rating and average price target of $33.59 underscore the continued belief in the company's long-term value creation.

Looking Ahead

REGENXBIO plans to present updated 12-month data from the RGX-121 pivotal trial at the International Congress of Inborn Errors of Metabolism in September 2025, which could further influence investor sentiment and regulatory outcomes. The company also anticipates receiving a Priority Review Voucher (PRV) upon RGX-121's U.S. marketing approval, which could be monetized for a substantial amount, potentially extending its financial runway. The progress of RGX-202 and other pipeline assets will also be key factors to watch as REGENXBIO navigates its commercialization strategies and continues to expand its gene therapy portfolio.