Ultragenyx reports ‘positive’ topline results for ornithine transcarbamylase deficiency.

Ultragenyx reports ‘positive’ topline results from Phase 1/2 DTX301 study

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Ultragenyx reports ‘positive’ topline results from Phase 1/2 DTX301 study

Ultragenyx Pharmaceutical (RARE) announced positive longer-term safety and efficacy data from the first dose cohort of the Phase 1/2 study of DTX301, an investigational adeno-associated virus gene therapy for the treatment of ornithine transcarbamylase deficiency.

The 52-week study is designed to enroll patients with late-onset disease who are clinically stable and on a stable dose of alternate pathway medication.

All three patients in the first, lowest-dose cohort received a single DTX301 dose of 2.0 10^12 GC/kg, and the pre-defined endpoint for efficacy evaluation occurred 12 weeks after dosing.

As of the February 15, 2018 data cutoff date, patient 1 has been followed for 24 weeks, patient 2 for 20 weeks, and patient three for 12 weeks The first patient’s rate of ureagenesis was normalized, maintained and then substantially increased over 24 weeks.

The rate of ureagenesis at baseline was 67% of normal, with the normal rate of ureagenesis defined as 300 umol/kg/hr. The patient had an initial peak effect at 6 weeks at 112% of normal, and then declined at week 12 to 87% of normal during the steroid regimen that was used to treat the patient’s mild ALT elevations.

After steroids were weaned, ureagenesis began to rebound to 91% of normal at week 20 and then substantially increased to 134% of normal at week 24. The protocol allows for the tapering or discontinuation of alternate pathway medications and all alternate pathway medications were stopped at week 24 for patient 1 based on their choice. In the 3 weeks since stopping these medications, the patient has been doing well clinically as reported by the investigator.

The second and third patients did not show a clinically meaningful change in rate of ureagenesis over 20 weeks and 12 weeks, respectively.

As of February 15, 2018 there have been no infusion-related adverse events and no serious adverse events reported. All adverse events have been Grade 1 or 2 and have resolved.

The only treatment-related adverse events were the previously-reported mild, clinically asymptomatic and manageable elevations in alanine aminotransferase in two patients, peaking at 45 and 118 IU/L.These ALT elevations were mild and similar to what has been observed in other programs using AAV gene therapy.

Both patients completed a standard tapering course of corticosteroids as outpatients to treat the ALT elevations and their ALT levels have remained in the normal range since completing the tapering course. The third patient’s ALT levels remained in the normal range through twelve weeks. All three patients have remained clinically and metabolically stable.

The Data Monitoring Committee has completed its review of the current Cohort 1 data, and Ultragenyx will proceed to the second, higher-dose cohort of the study. Three patients will be enrolled in Cohort 2 and will each receive a single DTX301 dose of 6.0 10^12 GC/kg.

The first patient is expected to be enrolled in March 2018, and data from the second cohort are expected in the second half of 2018.

RARE closed at $52.66. It last traded at $54.00


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