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

The efficacy of rifapentine, an oral antibiotic used in the treatment of tuberculosis, is reduced due to its degradation at gastric pH and low solubility at intestinal pH. We aimed to improve delivery properties in vitro by incorporating rifapentine into pH-responsive amorphous solid dispersions with cellulose derivatives including: hydroxypropylmethylcellulose acetate succinate (HPMCAS), cellulose acetate suberate (CASub), and 5-carboxypentyl hydroxypropyl cellulose (CHC). Most amorphous solid dispersions reduced rifapentine release at gastric pH, with the best performing polymer CASub showing >31-fold decrease in area under the curve compared to rifapentine alone. Lower solubility at gastric conditions was accompanied by a reduction in the acidic degradation product 3-formylrifamycin, as compared to rifapentine alone. Certain formulations also showed enhanced apparent solubility and stabilization of supersaturated solutions at intestinal pH, with the best performing polymer HPMCAS showing almost a 4-fold increase in total area under the curve compared to rifapentine alone. These in vitro results suggest that delivery of rifapentine via amorphous solid dispersion with cellulose polymers may improve bioavailability in vivo.