RS17 is a peptide which binds to the transmembrane protein CD47 and blocks the interaction of CD47 with the regulatory membrane glycoprotein signal regulatory protein alpha (SIRPalpha). In normal cells, CD47 interaction with SIRPalpha on the macrophage surface membrane sends a phagocytosis inhibiting signal, a mechanism which can be taken advantage of by cancer cells to enable immune escape. RS17 blockade of the CD47 and SIRPalpha interaction in cancer cells can prevent phagocytosis evasion, and treatment with RS17 significantly promotes the removal of tumour cells by macrophages. RS17 has a strongly inhibitory effect on tumour growth in a cancer xenograft mouse model.
