A novel functional protein tool derived from cholesterol-dependent cytolysin was developed andits application for clinical field such as a drug delivery system was investigated. This tool iscomposed of both of a functional-domain to connect the drug carrier and a targeting-domain torecognize the target cell. The recombinant protein consisted of a lung tumor specific peptide,domain 1-3 of intermedilysin with an introduced disulphide-bond to block the conformationalchange and pore-formation, and domain 4 of Streptococcus mitis-derived human plateletaggregation factor, was prepared using bacterial-expression system then investigated its function. Itwas shown that the prepared protein tool could specifically deliver a model of drug-carrier vesiclesto human lung tumor cells in vitro. This result suggests that the novel functional protein toolconstructed in this study has the superior properties for clinical application.