The US Food and Drug Administration (FDA) has approved the expanded use of Johnson & Johnson’s drug ​Imaavy to treat a rare blood disorder, the company said on Monday.

The ‌approval makes Imaavy the first treatment cleared for warm autoimmune hemolytic anemia, or wAIHA, and covers patients aged 12 and older who are currently or were previously treated with steroids.

Imaavy blocks ⁠a protein that keeps harmful antibodies in the bloodstream, lowering their levels ​while preserving other immune functions. The drug is infused into a vein every ​four weeks at a dose based on weight.

“Imaavy was able to demonstrate patients can go down on their steroids and still maintain that clinical response. Those are really important advances for ​patients,” Johnson & Johnson’s global immunology head David Lee told Reuters.

The approval was ​based on a mid-to-late-stage study of 115 adults in which about three times as many patients ‌receiving ⁠Imaavy achieved a lasting improvement in hemoglobin levels after 24 weeks as those on placebo.

Hemoglobin carries oxygen in red blood cells.

The most common side effects were swelling in the arms or legs, diarrhea and fever. Imaavy can also ​raise the risk ​of infections and ⁠cause serious allergic or infusion-related reactions, according to its prescribing information.

Lee said existing treatments also have toxicities and may not ​adequately control the disease. He said Imaavy improved and stabilized ​patients’ blood ⁠counts in the study.

About one in 8,000 people have wAIHA, with one to three new cases diagnosed annually per 100,000 people, according to Johnson & Johnson.

Imaavy was first ⁠approved in ​April last year to treat generalized myasthenia gravis ​in certain adults and patients aged 12 and older. The rare immune disorder causes muscle weakness.