Eli Lilly and Johnson & Johnson unit Centocor have temporarily stopped enrolling new patients in a late-stage clinical trial assessing their blockbuster ReoPro (abciximab) for the treatment of acute stroke.

The study has been suspended to allow an independent Safety and Efficacy Monitoring Committee to evaluate the benefit-risk profile of the agent for this indication, after data collected so far uncovered some issues with safety. Although the exact nature of the Committee’s concern has not been disclosed, the agent is known to increase the risk of bleeding, especially when used in combination with blood thinners.

The groups did not divulge how many patients were taking part in the Phase III study, known as AbESTT-II, but noted that they had planned to recruit 1,800 subjects in total. Those already participating will not receive further treatment until the SEMC recommends how to proceed, the companies said.

In defense of the drug, Jerome Boscia, senior vice president, clinical R&D at Centocor, stressed: “It is important to note…that ReoPro has an established favorable benefit-risk profile for its approved uses in people undergoing coronary procedures such as angioplasty or stenting.”

Investors seemed relatively unmoved by the news - Johnson & Johnson stock closed up $0.49 at $63.07 and Lilly’s shares rose 1.3% to $53.61 on the New York Stock Exchange.