The present invention encompasses novel synthetic peptide analogs that are antagonists to Substance P, substance P like peptides and related peptides and are useful for the treatment of cancer. The invention particularly relates to the design and synthesis of the novel substance P antagonist analogs incorporating &agr;,&agr;-dialkylated amino acids in a site specific manner. The invention encompasses methods for the generation of these peptides, compositions containing these peptides and pharmacological applications of these peptides specifically in the treatment and prevention of cancer.