Cardiac glycosides (CGs) have been used to treat cancer for hundreds of years. However, the narrow therapeutic window and system toxicity have hindered their wide clinical applications. Herein, the small molecule prodrug strategy and nanotechnology were integrated into one drug delivery system with enhanced therapeutic effect. Using periplocymarin (PPM) as a target agent, we designed a novel redox-responsive prodrug conjugated with linoleic acid (PPM-ss-LA), which was capable of self-assembling independent of exogenous excipients. This prodrug could co-assemble with DSPE 2k to form PEGylated prodrug nanoparticles (PPM-ss-LA/DSPE 2k -NPs) with enhanced colloidal stability and blood circulation. Compared with free PPM, PPM-ss-LA/DSPE 2k -NPs retained high anti-proliferative activity and showed increased cell uptake and therapeutic efficacy. Furthermore, the PPM-ss-LA/DSPE 2k -NPs acquired a greatly enhancement of 50% lethal dose (LD 50 ) in mice and reduced system toxicity compared with the free drug. Overall, the on-demand release of nanoprodrug delivery system could improve the therapeutic window and anticancer efficacy of CGs.
Cardiac glycosides could increase intracellular Ca 2+ ion by inhibiting the Na + /K + ATPase to induce apoptosis in many tumor cells. However, narrow therapeutic index, poor tumor selectivity and severe cardiovascular toxicity hinder their applications in cancer treatment. To improve the safety profile and tumor targetablility of cardiac glycosides, we designed octreotide conjugated periplocymarin, a cardiac glycoside isolated from Cortex periplocae . The conjugate showed higher cytotoxicity on MCF-7 cells and HepG2 tumor cells (SSTRs overexpression) but much less toxicity in L-02 normal cells. Tissue distribution studies of the conjugate using H 22 tumor model in mice showed higher accumulation in tumor and lower distribution in heart and liver than periplocymarin. Furthermore, in vivo anticancer effects of the conjugate on mice bearing H 22 cancer xenografts confirmed enhanced anti-tumor efficacy and decreased systemic toxicity. Altogether, octreotide-conjugated periplocymarin demonstrated tumor selectivity and may be useful as a targeting agent to improve the safety profile of cardiac glycosides for cancer therapy.
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