After a successful pilot study with anti-CD40L mAb (IDEC-131) in 15 MS patients (treatment with anti-CD40L revealed a profound reduction in clinical relapse rate in relapsing-remitting MS), a phase II trial with 46 MS patients was launched by Lloyd Kasper and Randolph Noelle in 2002 but was halted soon after a case of severe thromboembolism occurred in a similar trial in Crohn’s disease patients [48, 49]. Here, CD40LG is linked to Crohn disease.