Abstract: The use of classical superantigens for treatment of cancer has resulted in a low response rates and serious toxicity in humans which is attributable, in part, to the presence of preformed superantigen specific antibodies in the plasma of treated patients. The present invention addresses this problem by providing a method for treating tumors comprising the administration of one or a plurality of egc (enterotoxin gene cluster) staphylococcal enterotoxins comprising staphylococcal enterotoxins G, I, M, N, O. These superantigens in native unmodified form can be administered intrathecally, intratumorally, intravenously to humans with advanced lung cancer while resolving pleural effusions and prolonging survival to 300% above control patients treated with talc pleurodesis. Intratumoral egc superantigens induces a significant and sustained reduction of the tumor size.

Abstract: The invention provides mutant pyrogenic toxins. Preferred mutants retain a disulfide loop structure, although the endogenous sequence of the disulfide loop may be modified for example by insertion, deletion and/or substitution of at least one amino acid residue, or by combining a pyrogenic enterotoxin (or a fragment thereof) with another polypeptide to provide a chimeric molecule. Preferred mutants have a disulfide loop having less than about 8 amino acid residues. The invention also provides a system for producing the mutant pyrogenic toxins and methods of use for the mutants.