Grb2 SH2 domain inhibitor 1 is a conformationally restricted cyclic cell penetrating peptide (CPP) containing d-pro-l-pro motif ring (AF Φ Rpprrfq) (where Φ It is L-naphthylalanine, R is D-arginine, P is D-proline), which is mainly used as a cyclic peptide inhibitor.