In summary, the K-Ras(G12D)-inhibitory bicyclic peptide KS-58 dose-dependently inhibited the proliferation of CT26 colorectal cancer cells expressing K-Ras(G12D) and suppressed the growth of CT26-cell-derived tumors in mice, consistent with previous reports that this compound can inhibit the proliferation of a pancreatic cancer cell line expressing K-Ras(G12D). Here, KRAS is linked to colorectal cancer.