Roche Holding AG's arthritis and cancer drug, Rituxan, received approval from the U.S. Food and Drug Administration (FDA) to treat two rare disorders that cause blood vessel inflammation.

The U.S. health regulator approved Rituxan, in combination with glucocorticoids (steroids), to treat patients with Wegener’s granulomatosis (WG) and microscopic polyangiitis (MPA).

Vasculitis in patients with WG and MPA can lead to tissue damage. WG mostly affects the respiratory tract (sinuses, nose, trachea, and lungs) and kidneys, while MPA commonly affects the kidneys, lungs, nerves, skin, and joints.

Both of these diseases affect people of all ages and ethnicities, and both genders. The causes of these disorders are unknown, and both are considered orphan diseases because they each affect less than 200,000 people in the United States, the FDA said.

“This new indication for Rituxan provides the first approved therapy for these two orphan diseases,” said Curtis Rosebraugh, director of the Office of Drug Evaluation II in the FDA’s Center for Drug Evaluation and Research.

Rituxan is an antibody that is manufactured through biotechnology methods. The drug works by greatly reducing the number of specific immune cells in the blood, known as B cells.

The drug, which has been marketed since 1997, is also indicated for the treatment of patients with non-Hodgkin’s lymphoma, chronic lymphocytic leukemia, and rheumatoid arthritis.

Rituxan, also known as rituximab, is manufactured by San Francisco-based Genentech, which was acquired by Switzerland-based Roche in 2009.