Soluplus(®) based 9-nitrocamptothecin solid dispersion for peroral administration: preparation, characterization, in vitro and in vivo evaluation.

Our study aimed to develop an amorphous 9-nitrocamptothecin solid dispersion (9-NC-SD) using polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer (Soluplus(®)) for improving its oral bioavailability and antitumor efficacy in vivo. Freeze-dried 9-NC-SD with an optimized drug/polymer ratio at 1:15 (w/w) was characterized by powder X-ray diffraction, scanning electron microscopy and Fourier transform infrared spectroscopy. The amorphous form of 9-NC was obtained by freeze-drying and the aqueous solubility of 9-NC was increased to 1.42 mg/mL. Upon dilution, 9-NC-SD was proven to form micellar structures with an average size distribution around 58 nm ± 5 nm (PDI=0.107 ± 0.016). Moreover, 9-NC-SD showed significantly increased intracellular uptake efficiency in Caco-2 cells compared to free 9-NC. Furthermore, the AUC0-8h of 9-NC-SD following oral administration showed a 2.68-fold increase in the lactone form of 9-NC compared to that of free 9-NC in Sprague-Dawley rats. The 9-NC-SD did not show obvious inflammatory responses and gastrointestinal toxicity following oral administration as demonstrated by the histological analysis of the rat intestinal sections. Thus, 9-NC-SD represents a promising approach for improving the solubility and oral bioavailability of drugs with poor solubility.