NOVATO, Calif., March 30, 2026 (GLOBE NEWSWIRE) — Ultragenyx Pharmaceutical Inc. (NASDAQ: RARE) today announced that the U.S. Food and Drug Administration (FDA) has cleared the Investigational New Drug (IND) application for UX016, an investigational small molecule prodrug of sialic acid (SA) being evaluated as a substrate replacement therapy for GNE myopathy (GNEM). GNEM is a rare, severely debilitating, inherited neuromuscular disorder caused by mutations in the GNE gene that lead to deficient SA production. The UX016 program is externally funded by a patient group through clinical proof-of-concept, including a Phase 1/2 study expected to begin in the second half of 2026.
“People living with GNE myopathy face a profound and progressive loss of muscle function that affects every aspect of daily life, yet there are currently no approved treatment options to slow or alter the course of the disease,” said Coleman Kennedy, chief executive officer of the Neuromuscular Disease Foundation (NDF). “We appreciate Ultragenyx’s engagement with our community and are grateful for the innovative philanthropic support from others helping to move this program into the clinic. We look forward to continued collaboration as this study begins.”
UX016 is a prodrug composed of SA and a hydrophobic fatty acid tail that enhances efficient delivery to muscle as compared to naturally occurring SA. UX016 aims to address challenges that have historically limited the efficacy of prior substrate replacement therapies. Based on preclinical data, the fatty acid tail improves UX016 distribution to muscle and other tissues and supports more efficient uptake and release of SA within muscle cells.
“Advancing UX016 into the clinic marks an important milestone for the GNE myopathy community and reflects our commitment to developing an innovative approach to increase sialic acid uptake in muscle and to addressing the significant medical needs faced by this community,” said Emil Kakkis, M.D., Ph.D., chief executive officer and president of Ultragenyx. “We are pleased to initiate this work with the support of an innovative external funding model and look forward to working closely with physicians and the patient community as we evaluate UX016 in a Phase 1/2 study.”
The planned first-in-human, Phase 1/2 study will enroll approximately 24 adults ages 18 to 55 years with GNEM in the United States. The study, expected to begin in the second half of 2026, will evaluate the safety and efficacy of UX016. The study will also evaluate the pharmacokinetics and delivery to muscle at two doses 3:1 relative to placebo over the first 12 weeks and then will evaluate upper and lower muscle strength, patient reported outcomes relevant to GNEM, and other functional measures through Week 48 of treatment. For more information, patients can contact [email protected].
About GNE Myopathy
GNE myopathy (GNEM), also known as hereditary inclusion body myopathy (HIBM) and Nonaka Myopathy, is a rare, severely debilitating, adult-onset autosomal recessive neuromuscular disease caused by a defect in the biosynthetic pathway for sialic acid (SA). The body’s inability to produce adequate SA leads to progressive muscle wasting and severe disability. Patients typically become non-ambulatory and ultimately dependent on caregivers for most activities of daily living due to loss of upper and lower extremity muscle function. GNEM is estimated to affect approximately 10,000 people in commercially accessible geographies, and there is currently no approved therapy in the United States.
About UX016
UX016 is an investigational small-molecule prodrug composed of sialic acid (SA; also known as N‑acetylneuraminic acid [NANA]) and a C16 fatty acid tail designed to improve biodistribution to target tissues, like muscle, more effectively and efficiently than free SA. By increasing SA availability in muscle, UX016 is expected to restore sialylation of muscle glycoproteins and glycolipids and has the potential to slow or alter GNEM disease progression. In a GNEM (HIBM) mouse model, repeat subcutaneous administration of UX016 increased total, free and bound SA concentrations across multiple skeletal muscles and restored SA levels toward near normal.
About Ultragenyx
Ultragenyx is a biopharmaceutical company committed to bringing novel therapies to patients for the treatment of serious rare and ultra-rare genetic diseases. The company has built a diverse portfolio of approved medicines and treatment candidates aimed at addressing diseases with high unmet medical need and clear biology, for which there are typically no approved therapies treating the underlying disease.
The company is led by a management team experienced in the development and commercialization of rare disease therapeutics. Ultragenyx’s strategy is predicated upon time- and cost-efficient drug development, with the goal of delivering safe and effective therapies to patients with the utmost urgency.
For more information on Ultragenyx, please visit the company’s website at: www.ultragenyx.com.
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