WASHINGTON, D.C. — The Food and Drug Administration last week granted accelerated approval to Ultragenyx Pharmaceutical Inc.’s Genglycos, the first treatment for glycogen storage disease type Ia, after a clinical trial found the one-time gene therapy reduced patients’ dependence on daily cornstarch supplementation by an average of 31%.
The treatment is approved for adults and children ages 8 and older as an addition to nutritional management. Its authorization requires Ultragenyx to conduct further studies confirming the therapy’s clinical effectiveness.
Glycogen storage disease type Ia is an inherited disorder caused by a deficiency of glucose-6-phosphatase, an enzyme needed to release stored glucose from the liver and kidneys into the bloodstream.
Without that enzyme, patients can experience dangerously low blood sugar between meals or during fasting. The disorder can also cause metabolic complications affecting multiple organs and tissues.
Treatment traditionally requires frequent meals, restrictions on certain sugars, medical monitoring and round-the-clock doses of uncooked or specially formulated cornstarch to maintain blood sugar levels.
Genglycos, also known as pariglasgene brecaparvovec-opnr, uses an AAV8-based gene therapy to deliver a functional G6PC gene to the liver. The treatment is designed to restore the missing enzyme and improve the body’s ability to release stored glucose.
The FDA based its decision on a randomized, double-blind, placebo-controlled study that followed patients for 48 weeks after treatment.
Patients receiving Genglycos recorded a statistically significant average reduction in daily cornstarch intake of 31% compared with the placebo group. They also required an average of one fewer cornstarch dose per day.
However, treated patients experienced an average 3% increase in the proportion of glucose readings falling below 70 milligrams per deciliter, the threshold associated with hypoglycemia, compared with patients receiving a placebo.
Serious adverse reactions reported across two clinical studies included anaphylaxis, adrenal insufficiency, elevated lactate levels and hypoglycemia.
More common side effects included elevated liver enzymes, nausea, headaches, constipation and high blood sugar. Elevated triglyceride levels occurred in 29% of treated patients, compared with 8% of those receiving a placebo.
The prescribing information includes warnings about severe allergic reactions, liver toxicity, adrenal insufficiency and the potential development of tumors. The treatment should not be used during pregnancy.
“Genglycos offers these patients and their families a one-time therapy that targets the root cause of the disease,” stated Megha Kaushal, acting deputy director of the FDA’s Office of Therapeutic Products.
The accelerated approval relied on reduced cornstarch intake as a surrogate measure considered reasonably likely to predict clinical benefit. Continued confirmation of the treatment’s effectiveness will depend on additional clinical trials.
The application received a Rare Pediatric Disease Priority Review Voucher, along with regenerative medicine advanced therapy and Fast Track designations.
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