Hydroxyethyl starch-10-hydroxy camptothecin conjugate: synthesis, pharmacokinetics, cytotoxicity and pharmacodynamics research

10-hydroxy camptothecin (10-HCPT) is an antitumor agent effective in the treatment of several solid tumors but its use is hampered by poor water solubility, low lactone stability, short plasma half-life and dose-limiting toxicity. In this study, 10-HCPT-hydroxyethyl starch (HES) conjugate was prepared to overcome these limits of 10-HCPT. The solubility of 10-HCPT conjugate was 0.72mg/ml, about 100 times to free 10-HCPT. The 10-HCPT conjugate showed good sustained release effect in phosphate-buffered saline (PBS), rat plasma and liver homogenate. Meanwhile, 10-HCPT-HES conjugate achieved much lower IC50 and higher cytotoxicity effects than the free 10-HCPT on Hep-3B liver cancer cells. The pharmacokinetics results of 10-HCPT-HES conjugate demonstrated that the biological half-life of 10-HCPT was increased from 10min to 4.38h and the bioavailability was 40 times higher than the commercial 10-HCPT injection. The pharmacodynamics results indicated that 10-HCPT-HES conjugate had a better antitumor efficiency against nude mouse with Hep-3B tumor than the commercial 10-HCPT injection, and the inhibition ratio of tumor was 83.9 and 27.8%, respectively, at the same administration dosage. These findings suggest that 10-HCPT-HES conjugate is a promising drug delivery system providing improved long circulating effect, greater stability and better antitumor effect.