Cellulose-based amorphous solid dispersions enhance rifapentine delivery characteristics in vitro

The efficacy of rifapentine, an oral antibiotic used to treat tuberculosis, may be reduced due to degradation at gastric pH and low solubility at intestinal pH. We hypothesized that delivery properties would be improved in vitro by incorporating rifapentine into pH-responsive amorphous solid dispersions (ASDs) with cellulose derivatives including: hydroxypropylmethylcellulose acetate succinate (HPMCAS), cellulose acetate suberate (CASub), and 5-carboxypentyl hydroxypropyl cellulose (CHC). ASDs generally reduced rifapentine release at gastric pH, with CASub affording >31-fold decrease in area under the curve (AUC) compared to rifapentine alone. Critically, reduced gastric dissolution was accompanied by reduced degradation to 3-formylrifamycin. Certain ASDs also enhanced apparent solubility and stabilization of supersaturated solutions at intestinal pH, with HPMCAS providing nearly 4-fold increase in total AUC vs. rifapentine alone. These results suggest that rifapentine delivery via ASD with these cellulosic polymers may improve bioavailability in vivo.