Sepsis is a life-threatening condition. Septic shock is when sepsis becomes severe and cardiovascular function is severely deteriorated, leading to a high mortality rate. To date, there is only one FDA-approved drug with specific indication for sepsis: Giapreza (Angiotensin II). We discovered a new peptoid inhibitor of IL-15 receptor, IFRA3Q1. Our data show that IFRA3Q1 effectively rescues mice dying from LPS-induced sepsis and septic shock.