Federal regulators have formally stopped all enrollment and dosing in phase 3 clinical trials for Regado Biosciences (NASDAQ:RGDO) blood clotting drug amid safety concerns.

The clinical hold follows Regado’s July 2 announcement that it would voluntarily stop its trial of Revolixys Kit after the Data Safety Monitoring Board started an unplanned review of the data from the study. New Jersey-based Regado, which maintains R&D labs in Durham, said at the time the review of data for all 3,234 patients enrolled to date would take eight weeks. The review is focusing on serious adverse events and allergic reactions. Regado and the clinical sites conducting the trials will remain blinded to the study findings during the review.

Regado went public last August at $4 per share, raising $43 million. The company’s stock has traded as high as $14.10 per share. But Regado stock took a hit with the latest news and its shares fell by as much as 6 percent Thursday, trading at $2.53 per share in mid-afternoon Trading.

Revolixys, formerly known as REG-1, is based on technology originally developed at Duke University. The drug is being studied in a worldwide phase 3 trial comparing it to another drug, bivalirudin, in patients with acute coronary syndromes undergoing percutaneous coronary intervention (PCI), a hospital-based procedure used to mechanically open or widen obstructed coronary arteries.

“As announced earlier, we remain blinded to REGULATE-PCI study data and are awaiting the outcome of the full safety and efficacy analysis, including an analysis of benefit/risk ratio, being performed by our Data and Safety Monitoring Board (DSMB). Any recommendation to re-initiate patient enrollment in REGULATE-PCI will be based on the DSMB’s conclusions and would always be implemented in agreement with FDA,” Regado CEO David Mazzo said in a statement.