C5 is the target of the Food and Drug Administration (FDA)-approved monoclonal antibody eculizumab in diseases such as paroxysmal nocturnal haemoglobinuria (PNH) [18, 19] and atypical haemolytic uremic syndrome (aHUS) [20] and remains an enduring focus of drug discovery efforts to prevent complement-induced autoinflammation, with a number of second-generation therapeutics in clinical and preclinical development [21]. Here, C5 is linked to paroxysmal nocturnal hemoglobinuria.