Dec 17 (Reuters) - The U.S. Food and Drug Administration approved AstraZeneca (AZN.L) and Amgen"s (AMGN.O) drug, Tezspire, to treat severe asthma for those aged 12 years and older, the companies said on Friday. The approval is based on late-stage trial data that showed the drug cut the rate of asthma attacks by 56% among patients when compared with placebo. Amgen, which leads the manufacturing of the drug developed by AstraZeneca, told Reuters it was working to make Tezspire available to patients in January. Tezspire works by blocking a type of immune protein called TSLP, found in the linings of the lungs. TSLP belongs to the cytokine group responsible for sounding an alarm to the body"s immune system and can trigger inflammation. The drug in the trial had shown promise for wider use against different triggers and is the first and only biologic for severe asthma that does not have an eosinophilic or biomarker limitation within its approved label. Eosinophils are a type of white blood cell, associated with swelling and narrowing of airways that could make asthma attacks worse. Tezspire will compete with Regeneron"s (REGN.O) Dupixent and AstraZeneca"s own Fasenra, which brought in sales of almost $1 billion last year. Amgen will record sales for the drug in the United States, while AstraZeneca will record sales outside the country. Both the companies will also receive collaboration revenue from the profits.