We employed chemical conjugation of a 5-FU prodrug possessing an o-nitrobenzyl group with cyclic peptide Cys-Asn-Gly-Arg-Cys (CNGRC), which should target one of the tumor molecular markers, a specific APN/CD13 aminopeptidase N. Photoirradiation of the photoactivated prodrug 23 readily removed the photolabile o-nitrobenzyl chromophore to give quantitative amounts of 5-FU, whereas the prodrug was quite stable under dark conditions. The gene discussed is ANPEP; the disease is neoplasm.