The agency greenlit the drug, which will be marketed as Beqvez, for adults with moderate to severe hemophilia B who meet certain requirements.

The Food and Drug Administration on Friday approved Pfizer’s treatment for a rare genetic bleeding disorder, making it the company’s first-ever gene therapy to win clearance in the U.S.

The agency greenlit the drug, which will be marketed as Beqvez, for adults with moderate to severe hemophilia B who meet certain requirements.

The treatment will be available by prescription to eligible patients this quarter, a Pfizer spokesperson told CNBC. It has a hefty $3.5 million price tag, before insurance and other rebates, the spokesperson added, making it by far one of the most expensive drugs in the U.S.