The study’s primary endpoint was the average annualized rate of porphyria attacks during 6 months of treatment, which was 3.2 attacks in 46 patients evaluable for efficacy on givosiran treatment and 12.5 attacks in 43 patients evaluable for efficacy in the control group, a 74% reduction in attacks with givosiran that was statistically significant, Dr. Balwani reported. The percentage of patients with no attacks during the study was 16% among control patients and 50% among those on givosiran. Future analysis of the study data will attempt to identify the patients with the best responses to givosiran.
Among the full cohort of 94 patients enrolled in the study, 21% of the givosiran-treated patients had a adverse reaction, and 17% had a severe adverse reaction, compared with rates of 9% and 11%, respectively, among controls. Three of the serious adverse reactions were judged related to givosiran treatment: one patient with pyrexia, one with abnormal liver function test results, and one patient who developed chronic kidney disease. A total of two patients in the givosiran group developed chronic kidney disease that warranted elective hospitalization for diagnostic evaluation, and an additional three patients on the drug developed chronic kidney disease that did not require hospitalization. Nausea affected 27% of patients on givosiran and 11% of the control patients. Injection-site reactions occurred in 17% of those on givosiran and in none of the placebo patients. An elevation in the serum level of alanine aminotransferase to more than three times the upper limit of normal of baseline occurred in 15% of the givosiran-treated patients and in 2% of the placebo patients.
Givosiran’s small RNA molecule inhibits production of 5‐aminolevulinic acid synthase 1 (ALAS‐1), the rate-limiting enzyme that drives production of the heme precursor molecules that are pathophysiologic in patients with acute hepatic porphyria.
SOURCE: Balwani M et al. J Hepatol. 2019 April 70(1):e81-2.
