Ultragenyx Pharma Offers Interim Data from Phase 3 Extension Study of Sialic Acid ER at Int'l Congress of World Muscle Safety

Ultragenyx Pharmaceutical Inc. RARE, a biopharmaceutical company focused on the development of novel products for rare and ultra-rare diseases, today announced the presentation of results from a Phase 2 extension study of sialic acid extended-release (SA-ER, UX001) tablets in patients with hereditary inclusion body myopathy (HIBM; also known as GNE myopathy), a rare, progressive muscle-wasting disease. SA-ER is designed to replace the deficient sialic acid substrate in patients with HIBM. The data were presented at the 19^th International Congress of the World Muscle Society (WMS) in Berlin. "The data from the extension study of SA-ER support our plans to move forward with this program," said Sunil Agarwal, M.D., Chief Medical Officer of Ultragenyx. "While the 12 gram per day dose did not appear to have a clear advantage over the 6 gram per day dose, it does provide additional evidence of activity and safety and we are encouraged to see a potential long-term impact on disease progression in upper extremity muscle strength after approximately two years of treatment." Patients in the initial Phase 2 study were randomized to receive placebo, 3 grams/day, or 6 grams/day of SA-ER. After 24 weeks, placebo patients crossed over to either 3 grams/day or 6 grams/day, on a blinded basis, for an additional 24 weeks. The 48-week analysis compared change from baseline for the combined groups at 6 grams/day versus 3 grams/day of SA-ER. The initial Phase 2 data, which were presented at the American Academy of Neurology (AAN) Annual Meeting in April 2014, showed a statistically significant difference in the upper extremity composite (UEC) of muscle strength at 48 weeks with the higher dose group compared to the lower dose group. SA-ER appeared to be safe and well-tolerated with no serious adverse events observed to date. Most adverse events were mild to moderate and most commonly gastrointestinal in nature. In the first part of the extension study, all 46 patients from the 48-week Phase 2 study crossed over to 6 grams/day for a variable period of time that was on average 24 weeks. In the second part of the extension study, all 46 patients and 13 treatment-naïve patients received 12 grams/day of SA-ER for 24 weeks. The results presented at WMS include the 49 out of 59 patients who had 24 weeks of data at the higher dose. While the 12 grams/day data do not suggest any clinically meaningful advantage over 6 grams/day, the 12 gram data do provide additional data that support clinical activity with SA-ER treatment. The 12 gram daily dose of SA-ER appeared to be generally safe and well tolerated with no drug-related serious adverse events, but the rate of mild to moderate gastrointestinal adverse events did appear to be greater with this dose. Over the entire approximate two-year study, treatment with SA-ER appeared to slow the progression of upper extremity disease when compared to the 24-week placebo group extrapolated out to two years. Based on the 48-week and extension study data, Ultragenyx intends to discuss with regulatory authorities a potential pivotal study of SA-ER in HIBM patients. The company will also continue to treat patients in the ongoing extension study.