Bloomberg had one good article as well: http://www.bloomberg.com/news/2010-09-24/merck-kgaa-multiple-sclerosis-pill-is-rejected-by-eu-drug-agency-on-risks.html Multiple sclerosis causes the body to attack nerve cells through the immune system. Both cladribine and Novartis’s Gilenya blunt the attack by targeting white blood cells that harm the protective coating of nerve cells. Gilenya keeps lymphocytes, a type of white blood cell, from being released into the immune system, while cladribine kills lymphocytes. Lasting Effect One distinction between the two drugs is that cladribine’s effect lasts longer, said Jeffrey Cohen, a staff physician at the Cleveland Clinic’s Mellen Center for Multiple Sclerosis Treatment and Research, in a telephone interview yesterday. Cohen led a final-stage clinical trial comparing Gilenya to Biogen Idec’s Avonex. The prolonged impact makes cladribine more convenient for patients, who need only take pills a few days a year, Cohen said. Doctors may be concerned about the drug’s long-term influence on the immune system, he said, because “you can’t undo the effects.”