Boosting SN38-based oral chemotherapy to combine reduction-bioactivated structured lipid-mimetic prodrug with ascorbic acid

The reduction-responsive disulfide bonds have been widely used as bioactive linkages to facilitate a rapid release of anticancer drugs into tumor cells. However, the activation can be hindered by the kinetics of the thiol-disulfide exchange reactions. Supplementing with an additional reductant is a promising strategy to further boost drug release. Herein, inspired by the specific absorption mechanism of triglyceride fat, structured lipid-mimetic oral prodrugs of 7-ethyl-10-hydroxycamptothecin (SN38) were designed to improve intestinal permeability and bypass the first-pass effect. SN38 prodrugs were prepared into lipid formulations that could self-emulsify into nano-sized particles after entering the gastrointestinal tract. Surprisingly, we found that the oral bioavailability of the prodrug lipid formulation could be up to 2.69-fold higher than that of the parent SN38, indicating an effective oral delivery. In addition, the reduction-responsive disulfide bond was used as a linker, and ascorbic acid (ASC) was coadministrated to further promote the efficient release of SN38 from the prodrug. ASC enhanced the oral antitumor effect of the reduction-responsive oral prodrug and exhibited good safety. In summary, the combination of a structured lipid-mimetic prodrug and ASC was firstly demonstrated to boost the oral chemotherapy effect of the difficult-for-oral chemotherapeutics.