Ultragenyx Announces FDA Clearance of Investigational New Drug (IND) Application for UX016, a Sialic Acid Prodrug for the Treatment of GNE Myopathy
Program to be externally funded by a venture philanthropy agreement through clinical proof-of-concept, including the Phase 1/2 study planned to begin in the second half of 2026
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 .
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: .
Forward-Looking Statements and Use of Digital Media
Except for the historical information contained herein, the matters set forth in this press release, including statements related to Ultragenyx’s expectations and projections regarding the development of UX016, the timing, initiation and design of the planned Phase 1/2 clinical study, the anticipated enrollment and evaluation of patients, the potential safety, tolerability and efficacy of UX016, the ability of UX016 to address limitations observed with prior approaches, the expected benefits of the external philanthropic funding arrangement, future regulatory interactions, and the potential therapeutic impact of UX016 for patients with GNE myopathy, are forward-looking statements within the meaning of the "safe harbor" provisions of the Private Securities Litigation Reform Act of 1995. Such forward-looking statements involve substantial risks and uncertainties that could cause our clinical development programs, collaboration with third parties, future results, performance or achievements to differ significantly from those expressed or implied by the forward-looking statements. Such risks and uncertainties include, among others, the uncertainty of clinical drug development; risks related to the initiation, conduct, timing, enrollment and results of clinical trials; the possibility that safety, tolerability or efficacy data from preclinical studies or early‑stage clinical trials may not be predictive of future clinical results; the risk that UX016 may not demonstrate a favorable benefit‑risk profile or achieve clinical proof‑of‑concept; delays or challenges in regulatory interactions or approvals; the company’s ability to execute the planned clinical development program within the expected timelines or funding parameters; risks related to reliance on third parties, including clinical trial sites, investigators and manufacturers; manufacturing and supply risks; smaller than anticipated patient populations or market opportunities; competition from other therapies or approaches; and other risks that could affect the sufficiency of available funding, the company’s development plans, or the commercial potential of UX016. Ultragenyx undertakes no obligation to update or revise any forward-looking statements.
For a further description of the risks and uncertainties that could cause actual results to differ from those expressed in these forward-looking statements, as well as risks relating to the business of Ultragenyx in general, see Ultragenyx's Annual Report on Form 10-K filed with the Securities and Exchange Commission (SEC) on February 18, 2026, and its subsequent periodic reports filed with the SEC.
In addition to its SEC filings, press releases and public conference calls, Ultragenyx uses its investor relations website and social media outlets to publish important information about the company, including information that may be deemed material to investors, and to comply with its disclosure obligations under Regulation FD. Financial and other information about Ultragenyx is routinely posted and is accessible on Ultragenyx’s Investor Relations website () and LinkedIn website ().
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