RARE Stock Gains on FDA Nod for Rare Disease Gene Therapy Genglycos

FDA Nod for RARE’s Genglycos Supported by Phase III Data

The accelerated approval of Ultragenyx’s Genglycos is supported by results from the 48-week phase III GlucoGene study, which enrolled 46 participants aged eight years and older. Treatment with the drug produced a statistically significant reduction in daily cornstarch requirements compared with placebo. Patients were subsequently crossed over to the alternate treatment and continued to be monitored in longer-term follow-up.

Under the accelerated approval, Ultragenyx is required to provide additional safety and efficacy data through an enhanced GSDIa Disease Monitoring Program. The company will follow 50 commercially treated patients and 20 control patients for two years, while the broader monitoring program will continue to evaluate patients for up to 10 years. Continued approval for the indication may depend on confirmation of clinical benefit in post-marketing studies.

Year to date, shares of Ultragenyx have gained 14.1% compared with the industry’s 7% growth.

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RARE’s Genglycos May Ease the GSDIa Treatment Burden

GSDIa is an ultra-rare inherited metabolic disorder caused by pathogenic variants in the G6PC gene. These variants lead to a deficiency of glucose-6-phosphatase, an enzyme required for the release of glucose from stored glycogen and other metabolic sources. As a result, patients can experience severe hypoglycemia during fasting, including overnight, along with excess glycogen accumulation in the liver and other metabolic complications.

The condition affects an estimated 1,500-2,500 patients in the United States and 6,000-8,000 globally within commercially accessible geographies. Existing management relies on strict, around-the-clock supplementation with raw cornstarch to help maintain blood glucose levels. Even with strict adherence, interruptions in treatment can expose patients to severe hypoglycemia, seizures and potentially life-threatening complications, making the disease particularly burdensome for patients and caregivers.

Against this backdrop, the FDA decision is significant because Ultragenyx’s Genglycos is designed to address the underlying biological defect in GSDIa rather than manage its metabolic consequences. By delivering a functional G6PC gene to the liver, the therapy aims to restore the enzyme’s role in glucose production during fasting or metabolic stress, potentially reducing patients’ reliance on intensive cornstarch supplementation and easing the day-to-day burden of glucose management.

Genglycos Expands RARE’s Approved Product Portfolio

Following the FDA nod, Genglycos becomes the fifth FDA-approved therapy in Ultragenyx’s portfolio, adding to four established products. Crysvita (burosumab-twza) is approved in the United States for X-linked hypophosphatemia in adults and pediatric patients and for tumor-induced osteomalacia. Mepsevii (vestronidase alfa-vjbk) is approved for mucopolysaccharidosis type VII, while Dojolvi (triheptanoin) is approved for long-chain fatty acid oxidation disorders.

The fourth product, Evkeeza (evinacumab-dgnb), is indicated for homozygous familial hypercholesterolemia. Ultragenyx holds rights to develop, commercialize and distribute Evkeeza outside the United States, while Regeneron Pharmaceuticals commercializes the drug in the United States. This makes Genglycos a particularly important addition to Ultragenyx’s directly marketed U.S. portfolio, further diversifying its commercial base across rare and ultra-rare diseases.

RARE’s Zacks Rank & Stocks to Consider

Ultragenyx currently carries a Zacks Rank #3 (Hold).

Some better-ranked stocks in the biotech sector are Amneal Pharmaceuticals AMRX, Repligen RGEN and AC Immune ACIU. AMRX and RGEN currently sport a Zacks Rank #1 (Strong Buy) each, while ACIU carries a Zacks Rank #2 (Buy). You can see the complete list of today’s Zacks #1 Rank stocks here.

Over the past 60 days, earnings estimates for Amneal Pharmaceuticals have increased from $1.00 to $1.02 for 2026. Over the same period, earnings estimates increased from $1.12 to $1.21 for 2027. AMRX shares have risen 43.7% year to date.

Amneal Pharmaceuticals beat earnings in each of the trailing four quarters, delivering an average surprise of 32.82%.

Over the past 60 days, estimates for Repligen’s 2026 earnings per share have risen from $1.99 to $2.06, while estimates for 2027 have increased from $2.57 to $2.61. RGEN shares have gained 7.6% year to date.

Repligen’s earnings beat estimates in each of the trailing four quarters, with the average surprise being 16.80%.

Over the past 60 days, estimates for AC Immune’s 2026 loss per share have narrowed from 84 cents to 60 cents. Over the same period, earnings estimates for 2027 remained unchanged at 17 cents. ACIU shares have plunged 17.9% year to date.

AC Immune’s earnings beat estimates in each of the trailing four quarters, with the average surprise being 33.25%.

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This article originally published on Zacks Investment Research (zacks.com).

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