Novel SN38 derivative-based liposome as anticancer prodrug: an in vitro and in vivo study

Chan Wu,1,* Yang Zhang,1,2,* Daoqiu Yang,3,* Jinfeng Zhang,4 Juanjuan Ma,1 Dan Cheng,1 Jianming Chen,1,5 Li Deng1 1Department of Pharmaceutics, School of Pharmacy, Second Military Medical University, Shanghai 200433, People’s Republic of China; 2Department of Pharmacy, Shanghai Tenth People’s Hospital, School of Medicine, Tongji University, Shanghai 200072, People’s Republic of China; 3Department of Dermatology, 107th Hospital of PLA, Yantai 264000, People’s Republic of China; 4Department of Traditional Chinese Medicine, Shanghai Hospital of Chinese Integrative Medicine, Shanghai, People’s Republic of China; 5Tasly Diyi Pharmaceutical Group Co., Ltd, Jiangsu 223002, People’s Republic of China *These authors contributed equally to this work Background: Many novel drug delivery systems have been extensively studied to exploit the full therapeutic potential of SN38, which is one of the most potent antitumor analogs of camptothecins (CPTs), whose clinical application is seriously hindered by poor water solubility, low plasmatic stability, and severe toxicity, but results are always unsatisfactory.Methods: In this study, combining the advantages of prodrug and nanotechnology, a lipophilic prodrug of SN38, SN38-PA, was developed by conjugating palmitic acid to SN38 via ester bond at C10 position, and then the lipophilic prodrug was encapsulated into a long-circulating liposomal carrier by film dispersion method.Results: The SN38-PA liposomes were characterized as follows: an average particle size of 80.13 nm, an average zeta potential of -33.53 mv, and the entrapment efficiency of 99%. Compared with CPT-11, SN38-PA liposome was more stable in close lactone form, more efficient in conversion rate to SN38, and more potent in cytotoxicity against tumor cells. Pharmacokinetic study showed that SN38-PA liposome had significantly enhanced plasma half-life (t1/2) value of SN38 and increased area under the curve (AUC) of SN38, which was 7.5-fold higher than that of CPT-11. Biodistribution study showed that SN38-PA liposome had more active metabolite SN38 in each tissue. Finally, the pharmacodynamic study showed that SN38-PA liposome had higher antitumor effect with the antitumor inhibition rate of 1.61 times than that of CPT-11.Conclusion: These encouraging data merit further investigation on this novel SN38-PA liposome. Keywords: SN38, lipophilic prodrug, long-circulating liposome, pharmacokinetics, biodistribution, pharmacodynamics, CPT-1