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ultragenyx Ultragenyx Announces U.S. FDA Approval of GENGLYCOS ™ Gene Therapy , the First - Ever FDA - Approved Treatment Designed to Treat the Underlying Cause of Glycogen Storage Disease Type la ( GSDIa ) August 19 , 2026 GENGLYCOS is the first gene therapy approval , and fifth FDA approval overall , for the company Approval provides a long - awaited first - ever option to reduce the burden of care associated with GSDla Ultragenyx received a Priority Review Voucher upon approval Ultragenyx to host conference call on 8/19/26 at 6:00 p.m. Eastern Time NOVATO , Calif . , Aug. 19 , 2026 ( GLOBE NEWSWIRE ) -- Ultragenyx Pharmaceutical Inc. ( NASDAQ : RARE ) today announced that the U.S. Food and Drug Administration ( FDA ) granted accelerated approval for GENGLYCOSTM ( pariglasgene brecaparvovec - opnr ) , also known as DTX401 , in adult and pediatric patients eight years and older with glycogen storage disease type la ( GSDla ) . " The approval of GENGLYCOS fulfills our commitment to provide the first therapy that directly targets the root cause of GSDIa . The reduced reliance on cornstarch , experienced by patients in our clinical studies , demonstrates this gene therapy's ability to establish the normal breakdown of glycogen to produce glucose during fasting or episodes of metabolic stress . This ability to regulate glucose has alleviated the disease burden and has the potential to mitigate the risk of severe or life - threatening hypoglycemia for these patients , " said Eric Crombez , M.D. , chief medical officer at Ultragenyx . " As our first gene therapy approval , GENGLYCOS represents an important achievement for our company and the realization of the promise of a powerful new tool to deliver transformative medicines for people living with rare diseases . " GSDIa is an ultra - rare genetic metabolic disorder caused by a deficiency of the enzyme needed to release glucose from the liver to the bloodstream . The deficiency reduces the liver's ability to control glucose levels and is associated with potentially life - threatening hypoglycemia episodes and other serious complications , requiring rigorous nutritional management that involves a burdensome , around - the - clock regimen of raw cornstarch intake as an oral glucose replacement therapy . Glucose control with cornstarch is crude with large swings in glucose , and patients instead end up spending a large fraction of their day significantly hyperglycemic to avoid hypoglycemic episodes . GSDIa affects 1,500-2,500 patients in the U.S. and 6,000-8,000 worldwide within commercially accessible geographies . " Day - to - day management of GSDla requires a relentless regimen of raw cornstarch and strict dietary management that can be extraordinarily demanding for patients and families . Even with meticulous adherence to this regimen , patients must be perfect . Any missed cornstarch puts patients at risk of severe hypoglycemia , seizures , and even death , " said David Weinstein , M.D. , MMSc , one of the world's leading GSDla experts . " The approval of GENGLYCOS represents a major step forward for the GSDla community and reflects almost 30 years of work and scientific progress aimed at improving safety and the quality of life of people living with this disease . " " For families affected by GSDIa , every day revolves around strict schedules , overnight vigilance , and the constant worry that a missed meal or dose of cornstarch could trigger life - threatening hypoglycemia , " said David and Wendy Feldman , co - founders and current Board members at The Children's Fund for Glycogen Storage Disease Research . " This approval is an incredibly meaningful milestone for a community that has spent decades hoping , advocating , and helping advance the research for new treatment options that could ease the burdens of this disease . " Clinical Program and Post - Marketing Study Requirements Supporting Accelerated Approval of GENGLYCOS The approval of GENGLYCOS is based on positive data from the 48 - week randomized , double - blind , placebo - controlled Phase 3 GlucoGene study which treated 46 participants aged eight years and older with DTX401 ( 1.0 x 10 ^ 13 GC / kg dose ) or placebo , showing a reduction in the cornstarch requirements in the treated group ( p < 0.001 ) . There were 44 participants in the modified intention - to - treat ( mITT ) population providing efficacy data within the Week 48 analysis period following treatment with DTX401 ( n = 20 ) or placebo ( n = 24 ) . At Week 48 , eligible participants crossed over and received the alternate treatment . After crossover , participants continued to be followed , with analyses conducted at Week 96 and Week 144 . As part of accelerated approval , Ultragenyx has agreed to provide two years of safety and efficacy clinical data from open - label commercial treatment of 50 patients and 20 control patients through enhancement of its existing GSDla Disease Monitoring Program ( DMP ) . The control group will consist of patients who sought commercial treatment but cannot be treated with GENGLYCOS due to the presence of anti - AAV8 antibodies . The study will provide more data to support the reduction in cornstarch clinical burden , fasting tolerance , and other measures in a post - marketing setting where patients can know their immediate glucose levels , and their cornstarch and diet can be managed more promptly by their physician . The DMP will also evaluate previously treated clinical trial participants as well as these new commercial patients for a total of 10 years . Enabling Access for Eligible Patients Ultragenyx will provide support to help enrolled patients and caregivers navigate access to treatment through its UltraCare® program , which now includes specially trained UltraCare® Gene Therapy Guides to help understand insurance coverage , assist in obtaining treatment support , and answer questions about the treatment process . Dedicated in - house UltraCare Gene Therapy Guides are available Monday through Friday from 9 a.m. to 8 p.m. Eastern Time at 888-756-8657 . More information is available at www.ultracaresupport.com . GENGLYCOS will be available through a national network of Qualified Treatment Centers ( QTCs ) with specialized expertise and training to safely administer gene therapy . GENGLYCOS is manufactured entirely at Ultragenyx's Gene Therapy Manufacturing Facility ( GTMF ) in Bedford , Mass . , strengthening the Company's ability to scale production of high - quality gene therapy products and deliver them to patients as efficiently as possible .