Atypical hemolytic-uremic syndrome: evolution of treatment and impact of clinical and genetic characteristics on possibility of eculizumab withdrawal

   Atypical hemolytic uremic syndrome (aHUS) is a rare variant of thrombotic microangiopathy (TMA) associated with uncontrolled activation of alternative complement pathway due to mutations in complement regulatory protein genes or antibodies formation to regulators. Clinical manifestations of aHUS can be triggered by infections, sepsis, pregnancy, autoimmune diseases, organ transplantation, and other complement-activating conditions. Previously, the only treatment option for aHUS was plasma therapy – fresh frozen plasma infusions or plasma exchange, but its effectiveness was insufficient. Currently, targeted treatment available – recombinant monoclonal antibodies against complement C5 protein – eculizumab with high efficiency in achieving aHUS remission, renal function recovery, and preventing TMA at kidney transplantation. For a long time, the question of the optimal duration of treatment and the possibility of eculizumab discontinuing remained unresolved. It was shown that aHUS relapses developed in 20-35 % of patients after discontinuation of complement-blocking therapy. The article presents an overview of a large number of studies of eculizumab treatment outcomes and the possibility of its withdrawal, including a French prospective multicenter study that identified risk factors for aHUS relapse after eculizumab discontinuation: the presence of rare variants of complement genes, female gender, increased soluble C5b-9 plasma level. In patients who did not have rare genetic variants, the risk of relapse was less than 5 %. In general, eculizumab discontinuation after achieving complete remission of aHUS and renal function recovery in patients with low risk of recurrence can provide better tolerability of maintenance treatment, and decrease the incidence of infectious complications and the financial burden on the healthcare system.