BARCELONA (Reuters) - An experimental intravenous drug from Sanofi-Aventis to stop blood clots in people with serious heart conditions has proved successful in a mid-stage trial, researchers said on Sunday. Patients receiving an intermediate dose of otamixaban had a 40 percent lower rate of death, second heart attack or other coronary complications than those treated with heparin and Schering-Ploughs Integrilin. Findings from the trial, involving 3,241 patients, were presented at the annual meeting of the European Society of Cardiology and published online by the Lancet medical journal. Marc Sabatine of Brigham and Womens Hospital in Boston, who led the research, said his team was now liaising with Sanofi on plans for a final-stage Phase III on the drugs use in patients with acute coronary syndrome (ACS). ACS describes a range of conditions, including unstable angina, or acute chest pain, and heart attack. We and they (Sanofi) have a high degree of enthusiasm and are working on design of a Phase III trial, Sabatine said, after reporting the Phase II clinical trial results in Barcelona. Plans have not been finalised yet but there is active work going on in the design for the Phase III trial, so stay tuned. If it succeeds in the next stage of testing, otamixaban may offer a simpler and more effective alternative to heparin and Integrilin in patients undergoing procedures to open clogged arteries, making it a rival to the Medicines Cos Angiomax. J.P. Morgan analyst Alexandra Hauber said in a recent report that the drug, which is not generally on investors radar screens, could eventually generate peak sales of $1 billion to $1.5 billion a year, though it is not expected to reach the market before 2013. However, John Eikelboom of McMaster University, writing in a commentary in the Lancet, questioned the need for another treatment option like otamixaban. Without safety or convenience advantages, otamixaban would need to demonstrate efficacy that is superior not only to heparin, but also to bivalirudin (Angiomax), before it would be adopted for clinical use, he wrote. French drugmaker Sanofi needs to find new drugs to replace a raft of products that are set to lose patent protection in the coming years.