Givosiran: a targeted treatment for acute intermittent porphyria

The acute hepatic porphyrias (AHPs) are a family of rare genetic diseases associated with attacks of abdominal pain, vomiting, weakness, neuropathy, and other neurovisceral symptoms. Pathogenic variants in 1 of 4 enzymes of heme synthesis are necessary for the development of AHP, and the onset of acute attacks also requires the induction of δ-aminolevulinic acid synthase 1 (ALAS1), the first and rate-limiting step of heme synthesis in the liver. Givosiran is an RNA interference medication that inhibits hepatic ALAS1 and was designed to treat AHP. In 2019 the US Food and Drug Administration approved givosiran for AHP based on positive results from a phase 3 clinical trial of 94 patients with AHP who demonstrated a marked improvement in AHP attacks and a substantial decrease in δ-aminolevulinic acid and porphobilinogen, the primary disease markers of AHP. A long-term follow-up study demonstrated continued improvement in AHP attack rates, biochemical measures of disease, and quality of life. Real-world studies have also confirmed these results. Common side effects include injection site reactions, hyperhomocysteinemia, and abnormalities of liver and renal biochemistries. This article reviews the studies that led to givosiran approval, discusses real-world clinical data, and highlights remaining questions in the treatment of AHP.