C5 and rheumatoid arthritis: More importantly C5 activation and its peptide C5a signaling are in the FDA-approved clinical interventions to this date: PMX-53TM (PepTech, MA) is prescribed for rheumatoid arthritis and psoriasis patients, and EculizumabTM (Alexion, MA) is prescribed for paroxysmal nocturnal hemonglobinuria.