A highly GSH-sensitive SN-38 prodrug with an "OFF-to-ON" fluorescence switch as a bifunctional anticancer agent.

SN-38 (7-ethyl-10-hydroxy-camptothecin) is an active metabolite of irinotecan (CPT-11) and the most potent camptothecin analogue. In this study, 2,4-dinitrobenzene sulfonyl (DNS) was covalently conjugated as a GSH-sensitive trigger to 10'-OH of SN-38 to yield a GSH-sensitive prodrug, denoted as DNS-SN38, with virtually quenched fluorescence due to donor-excited photo-induced electron transfer (d-PeT). By investigating DNS-SN38's activation properties upon fluorescence restoration and cytotoxic potency against ovarian cancer cell lines (A2780 and m-Cherry + OCSC1-F2), its potential applicability as a useful chemotherapeutic agent was demonstrated.