Ultragenyx Stock Crashes After GTX-102 Failure Despite Genglycos Win

Ultragenyx Pharmaceutical Inc. (RARE) filed an SEC Form 8-K — Other Events. Item 8.01 Other Events. On September 17, 2026, Ultragenyx Pharmaceutical Inc. (“Ultragenyx” or the “Company”) announced that the U.S. Food and Drug Administration (the “FDA”) granted standard full approval of FAYUVI™ (rebisufligene etisparvovec-hopf), also known as UX111, for the

Ultragenyx Pharmaceutical (RARE) shares rose 10% after the FDA approved Fayuvi, a gene therapy for mucopolysaccharidosis type IIIA. This is the first FDA-authorized treatment for this rare pediatric disease. The therapy showed improved cognitive function in clinical trials but carries risks like liver enzyme increases and potential long-term tumor development.

Ultragenyx Pharmaceutical received FDA approval for Fayuvi, a gene therapy for Sanfilippo syndrome Type A. The treatment targets the enzyme deficiency causing the disease. Ultragenyx shares rose 6% on the news.

The US FDA has approved a gene therapy developed by Ultragenyx Pharmaceutical Inc. for the treatment of a rare disorder. The therapy, designed for patients with a specific genetic condition, marks a significant milestone in the company's pipeline. According to the FDA, this approval provides a new treatment option for a previously underserved patient population.

Ultragenyx (RARE) shares dropped 44.7% premarket after its Phase 3 Aspire study for apazunersen in Angelman syndrome missed primary and key secondary endpoints. Analysts downgraded the stock, with price targets lowered significantly. Shares fell below their 52-week low. According to the company, no meaningful differences were found between treatment and placebo groups.

Ultragenyx Pharmaceutical Inc. (RARE) stock rose 3.57% after positive coverage of its rare disease pipeline. However, it later plunged 45% due to the failure of the GTX-102 Phase 3 trial. The company reported $214M in revenue and an 87.8% gross margin but posted a net loss of $92M. Analysts have mixed views, with some cutting price targets while others maintain an Overweight rating. The stock is highly volatile, trading at $15.35 after the drop.