| abstract |
A peptide vector comprising a cyclic peptide that is useful for a drug delivery system capable of repeated systemic administration to advanced solid cancers such as liver cancer and pancreatic cancer, and that can be taken into tumor cells and transferred to the cytoplasm, and the cyclic peptide are used. To provide a tumor-directed peptide vector. A pancreatic cancer cell line or a tumor formed by inoculating the pancreatic cancer cell line is contacted with a phage library on the surface of which a peptide having a 9 amino acid sequence having cysteine at both ends is displayed, and the tumor cell is actually used. The amplified phage is extracted, DNA is extracted and subjected to sequencing, and a cyclic peptide that can be taken into the tumor cell and transferred to the cytoplasm is identified from the determined base sequence. |