Several drug companies, such as Biogen Idec and Novo Nordisk, are developing new, longer-acting versions of the blood clotting factors used by people with hemophilia. Patients with severe forms of the disease need regular infusions, lasting 30 minutes or more, of relatively short acting and very expensive clotting factors.

The new longer-lasting hemophilia B products can be given every 10 days or two weeks, offering significant advantages for patients, especially young children, who now need infusions every two or three days.

Hemophilia is hereditary, passed from parent to child through genes. People with hemophilia have little or no clotting factor. Hemophilia A and Hemophilia B have different clotting factors that are low or missing, but both can experience spontaneous bleeding, as well as severe bleeding following injuries or surgery.

Worldwide, about one in 5,000 men is born with hemophilia A and one in 25,000 men is born with hemophilia B each year. Since the gene is carried on the X chromosome, hemophilia is almost entirely a disease of men. Women can pass the gene to their offspring. Hemophilia has often been called the “Royal Disease” since it was carried by Britain’s Queen Victoria and affected many of the ruling families of Europe. Blood factor concentrates were not developed until the mid-20th century, and up until that time people with hemophilia had a life expectancy of less than 30 years.

The U.S. Food and Drug Administration is due to decide by mid-year whether to approve a new long-lasting hemophilia B clotting factor from Biogen Idec. Novo Nordisk expects to file next year for regulatory approval of its long-acting hemophilia B drug.

Some industry experts say these and other new treatments could help drive down the price of existing hemophilia products, which can total $300,000 or more a year for a single patient.