The U.S. Department of Justice (DoJ) is investigating the PLATO clinical trial, Astra Zeneca announced in a financial report.

London-based Astra Zeneca reported that it received a demand from the DoJ’s civil division for documents and information on PLATO (PLatelet Inhibition And paTient Outcomes) on Oct. 21. PLATO researchers determined that ticagrelor (Brilinta, Astra Zeneca), an oral, reversible, direct-acting inhibitor of the adenosine diphosphate receptor P2Y12, significantly reduced the rate of death from vascular causes, MI or stroke without an increase in the rate of overall major bleeding compared with clopidogrel (Plavix, Bristol-Myers Squibb) in patients with acute coronary syndrome.

The FDA approved ticagrelor in 2011 based on PLATO results. But the agency had issued several delays before making its decision while it sought additional information from the company.

In its statement on third quarter and nine-month results for 2013, Astra Zeneca acknowledged the DoJ request and said it planned to cooperate with the inquiry.