The US Food and Drug Administration has approved the world’s most expensive drug. Per dose, Hemgenix will cost US$3.5 million.

A gene therapy drug, Hemgenix appears to cure, at least temporarily, Haemophilia B, a genetic bleeding disorder resulting from missing or insufficient levels of blood clotting Factor IX, a protein needed to produce blood clots to stop bleeding.

Patients with severe Haemophilia B typically require a routine treatment regimen of intravenous (IV) infusions of Factor IX replacement products to maintain sufficient levels of clotting factor to prevent bleeding episodes.

Hemgenix is a one-time gene therapy product given as a single dose by IV infusion. It consists of a viral vector carrying a gene for clotting Factor IX. The gene is expressed in the liver to produce Factor IX protein, to increase blood levels of Factor IX and thereby limit bleeding episodes.

“Gene therapy for haemophilia has been on the horizon for more than two decades. Despite advancements in the treatment of haemophilia, the prevention and treatment of bleeding episodes can adversely impact individuals’ quality of life,” said Peter Marks, of the FDA’s Center for Biologics Evaluation and Research.

Expensive? Yes – the most expensive drug ever produced. But according to the Institute for Clinical and Economic Review, a non-profit that reviews drug pricing, it is value for money. Routine infusions with Factor IX are also expensive. The hope is that a single treatment will actually cure the disease.

Hemgenix, or etranacogene dezaparvovec, is manufactured by CSL Behring.