Drug maker AstraZeneca has agreed to pay $520 million to settle whistleblower lawsuits filed in federal court in Philadelphia that accused the company of engaging in illegal tactics — including kickbacks to doctors — to promote so-called “off-label” uses for one of its drugs.

The drug, Seroquel, is an anti-psychotic that was approved by the Food and Drug Administration only for narrow uses, such as combating schizophrenia or acute manic episodes in those with bipolar disorder. But prosecutors said AstraZeneca set out to market the drug directly to doctors for a wider range of ailments including Alzheimer’s disease, anger management, depression and sleeplessness.