In 195 patients who received the C5 inhibitor eculizumab in clinical trials between 2002 and 2005, thrombosis rates decreased from 7.37 events per 100 patient-years (1683 patient-years of exposure) without complement inhibition (ie, before eculizumab treatment) to 1.07 events per 100 patient-years (281 patient-years of exposure) with eculizumab [7]. The gene discussed is C5; the disease is deep vein thrombosis.