The present invention relates to non-membrane disruptive and p53 activating stapled peptides, as well as methods of treatment of cancer involving the use of these peptides. In one embodiment, the peptide comprises or consist of the amino acid sequence of TSFXaa1EY-WXaa3LLXaa2, where Xaa1 is (R)-2-(7′-octenyl)alanine or derivative thereof, or is (R)-2-(4′-pentenyl)alanine or derivative thereof; and Xaa2 and Xaa3 are independently any type of amino acid or modified amino acid. In another embodiment, the peptide comprising or consisting of the amino acid sequence of TSFXaa1EYW Xaa3LLXaa2ENXaa5, wherein Xaa1 and Xaa3 are any type of amino acid or modified amino acid; Xaa2 is S, or P, or (S)-2-(4′-pentenyl)alanine or a derivative of (S)-2-(4′-pentenyl)alanine; and wherein Xaa5 is F or Y.