The disorder, congenital fibrinogen deficiency (CFD), affects only 150 to 300 people in the United States, the agency said in a news release. People with the condition are unable to produce enough fibrinogen, a protein produced by the liver that's crucial to helping blood clot. Without treatment, patients face life-threatening bleeding.

Riastap is an injected fibrinogen concentrate made from the plasma of healthy human donors. Clinical testing among 15 patients with CFD showed an increase in clot firmness in 14 of the participants. The most frequent side effects reported were fever and headache, the FDA said.

Riastap is produced by CSL Behring, based in Marburg, Germany.

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