The present invention provides a method of screening for a drug for the prophylaxis or treatment of at least one disease selected from the group consisting of cardiac disease, autoimmune disease, inflammatory disease, central nervous system disease, infectious disease, sepsis, severe sepsis and septic shock, which includes selecting a substance that binds to an intracellular region of TLR4, and inhibits signal transduction from said molecule, and a kit for this method, which contains (1) a cell that expresses wild-type TLR4 and (2) a cell that expresses a mutant TLR4, and which can detect a signal from TLR4 with expression of a reporter gene as an index.