CHICOPEE, Mass. (WWLP) — The FDA just approved the most expensive drug on the market to date. The drug, known as Hemgenix, costs $3.5 million per dose and is administered to patients with the rare disorder Hemophilia B.

Hemophilia B is the rarer form of a blood clotting disorder resulting from insufficient amounts of a protein called Protein IX.

Most patients with Hemophilia B are men, and about 1 in every 40,000 people has the disorder. Women are often carriers, displaying no symptoms but passing the disorder on to their children.

Small cuts or bruises can be life-threatening, and many people need treatments once or more a week to prevent serious bleeding. Left untreated, the condition can cause bleeding that seeps into joints and internal organs, including the brain.

Currently, patients receive frequent, expensive IVs of a protein that helps blood clot and prevents bleeding. Hemgenix is a gene therapy drug that is given in one dose via IV infusion.

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

Drugmaker CSL Behring announced the $3.5 million price tag shortly after the FDA approval, saying its drug would ultimately reduce healthcare costs because patients would have fewer bleeding incidents and need fewer clotting treatments. The price appeared to exceed that of several other gene therapies priced upwards of $2 million.

Like most medicines in the U.S., most of the cost for new treatment will be paid by insurers — not patients — including private plans and government programs.

Famous people diagnosed with Hemophilia B include Alexei Nikolaevich, the ill-fated only son of Russian Czar Nicholas II, who was killed with the rest of his family in 1918 at the start of the Russian Revolution. Richard Burton, the actor in movies like “Cleopatra” and “1984,” was one of the first actors to publicly reveal he had Hemophilia B.

The Associated Press contributed to this report.