Ultragenyx Announces Progress Across Broad Gene Therapy Portfolio and Positive Longer-Term Data from Multiple Phase 1/2 Gene Therapy Studies - Seite 3

Based on the regulatory discussion and pending finalization, Ultragenyx intends to study as primary endpoints glycemic control by assessing the maintenance of glucose control by CGM and the reduction in cornstarch requirements. These primary endpoints will be supported by key secondary endpoints of improvement in percent of time spent in normal glucose control (60-120 mg/dL), time to hypoglycemia in controlled fasting challenge, and the GSDIa functional assessment diary signs and symptom scale. The durability of the treatment will be supported by the longer-term Phase 1/2 data and early treated Phase 3 patients. Based on the results to date, the therapeutic benefit appears to increase over time during the second year after treatment. Ultragenyx expects to initiate the study in the first half of 2021.

DTX301 (OTC) Program

Phase 1/2 data update: All six previous responders demonstrate durable metabolic control, including greater than two-year sustained responses

As previously reported, six out of nine treated patients responded to DTX301 on a dose-dependent basis, including all three treated at the highest dose. The three complete responders have now been stable through 104, 130, and 156 weeks post-treatment with good ammonia control despite discontinuation of their alternative pathway medications and protein-restricted diets. The three other responders also remain stable through Weeks 52 and 130 and are either continuing to taper medications and diet or intend to continue tapering once COVID-19 restrictions are lifted and patients can be more closely followed in clinic. All responders remain in excellent clinical condition with no significant adverse events, hospitalizations, or other events related to OTC deficiency.

There have been no infusion-related adverse events and no treatment-related serious adverse events reported in the study. All treatment-related adverse events have been Grade 1 or 2.

Prophylactic steroid cohort: Two OTC patients dosed with no safety issues; third patient to be dosed this month

Two of three patients have been dosed in the prophylactic steroid cohort, the final cohort in the Phase 1/2 study, at the same dose as in Cohort 3. Through up to 18 weeks post-dosing, both patients are doing well clinically with good metabolic control and without any safety issues. The third patient in the cohort, who has not yet been dosed due to delays related to COVID-19, is expected to be dosed this month.