The invention relates to a sorption agent for removing endotoxins from a biological fluid, the sorption agent having a water-insoluble, porous carrier and polymyxin, which is immobilized on the carrier, the carrier having a neutral, hydrophobic surface and polymyxin being immobilized on the surface of the carrier via hydrophobic interaction. The sorption agent is used in extracorporeal blood purification, in particular for treating individuals with sepsis.