Positive Results from Phase 3 Study of Acute Hepatic Porphyria Drug

Earlier this week, a press release from Alnylam Pharmaceuticals, Inc, announced the that the phase 3 study of their experimental acute hepatic porphyria drug Givosiran yielded positive results. According to the biotechnology company, the drug succeeded in meeting its primary efficacy goal and most of its secondary endpoints.

About Acute Hepatic Porphyria

Acute hepatic porphyria (AHP) is a subgroup of the porphyrias: a collection of diseases that effect the enzymes responsible for mediating heme synthesis. Heme is an iron-containing compound that partially makes up molecules of hemoglobin, the protein in red blood cells that carries oxygen throughout the body.

In a general sense, porphyrias lead to an overabundance of the natural chemicals in the body that produce porphyrins – organic compounds vital to the function of hemoglobin. The subsequent buildup of porphyrins can cause serious problems that vary in character depending on the subtype of porphyria.

Acute porphyrias typically create symptoms in the nervous system, which can be severe an onset rapidly. Symptoms during these porphyria attacks can last for days or weeks at a time. Acute hepatic porphyria is one such acute porphyria, and Alnylam hopes their drug Givosiran might help reduce the likelihood of experiencing attacks.

Givosiran Phase 3 Study

In a randomized, double-blind, placebo-controlled trial of 94 people with AHP (89 of which had the same type, acute intermittent porphyria [AIP]), Givosiran was found to produce an observable reduction in the rate of annual porphyria attacks (specifically attacks requiring hospitalization, or other urgent healthcare).

Adverse events 89.6% of Givosiran and 80.4% of placebo patients. Serious adverse events occurred in 20.8% of Givosiran and 8.7% of placebo patients. These numbers are reassuring about Givosiran’s safety, though one patient administered the drug was asked to leave the program following a spike in their alanine aminotransferase (a liver and kidney enzyme) levels that 8 times that of the normal upper limit.

The numbers are dense, but encouraging. Alnylam plans to move ahead by filing a new drug application (NDA) and Marketing Authorisation Application (MAA) by sometime midyear. NDAs and MAAs represent the last significant paperwork hurdles facing pharmaceutical companies before their product gains final approval. Based on their reported timeline, it could be possible to see Givosiran advertisements as early as the end of this year.

Givosiran has already been granted orphan drug status for acute hepatic porphyria in both the United States and Europe.


At this point it practically seems guaranteed for Givosiran to gain FDA approval in the near future. What do you think of this important news for AHP patients? Share your thoughts with Patient Worthy!

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