Safety and Efficacy of Chronic Extended Release Cornstarch Therapy for Glycogen Storage Disease Type I

Glycogen storage disease type I (GSD I) causes severe hypoglycemia during periods of fasting since both glycogenolysis and gluconeogenesis are impaired. Primary treatment in North America consists of cornstarch therapy every 3-4 h. Waxy maize extended release cornstarch was introduced for maintaining overnight glucose concentrations, but no studies have assessed long-term safety and efficacy of the product.

To demonstrate the safety and efficacy of modified cornstarch in GSD I.

An open-label overnight trial of extended release cornstarch was performed. Subjects with a successful trial (optimal metabolic control 2 or more hours longer than with traditional cornstarch) were given the option of continuing into the chronic observational phase. Subjects were assessed biochemically at baseline and after 12 months.

Of the 106 subjects (93 GSD Ia/13 GSD Ib), efficacy was demonstrated in 82 patients (88%) with GSD Ia and 10 patients (77%) with GSD Ib. The success rate for extending fasting was 95% for females and 78% for males. Of the patients who entered the longitudinal phase, long-term data are available for 44 subjects. Mean duration of fasting on traditional cornstarch prior to study for the cohort was 4.1 and 7.8 h on the extended release cornstarch (P < 0.001). All laboratory markers of metabolic control have remained stable in the chronically treated patients.

Extended release cornstarch appears to improve the quality of life of patients with GSD I without sacrificing metabolic control. Avoiding the overnight dose of cornstarch should enhance safety in this population.