Peptide antagonists of NK-1R show lower affinity for NK-1R than natural peptide agonists; they are metabolically unstable because they are hydrolyzed by peptidases; they are not lipid soluble so they do not penetrate the brain; and some of them have toxic effects; therefore, they cannot be used for the treatment of glioma [8,44]. The gene discussed is TACR1; the disease is central nervous system cancer.