British drugmaker AstraZeneca says the U.S. Department of Justice has closed its investigation into a clinical trial of the company's blood thinner Brilinta, and plans no further action.
The company announced in October 2013 that federal officials were looking into the 18,000-patient study, which began in 2009.
The study, dubbed PLATO, showed that patients taking Brilinta instead of competing drug Plavix were less likely to experience various heart-related problems, including heart attack, stroke and death. News of the U.S. investigation has raised questions about the validity of the trial and the benefits of the drug, which hit the market in 2011.
The London-based drugmaker said in a statement Tuesday: "AstraZeneca has always had absolute confidence in the integrity of the PLATO trial."
Brilinta had sales of $283 million last year.