Purpose: Compound A is a lead candidate for local treatment of gastrointestinal (GI) diseases. The solubility and stability of the compound in the GI environment was first evaluated in a specialist Colon Simulation Model using colonic inoculum from healthy human subjects and rats. An innovative colon-targeted microparticle formulation was then developed to assess the efficacy and safety margins of the compound in preclinical animal models. The pH-responsive microparticles were engineered using the ProRelease® technology that involves a novel solvent evaporation process which distributes the drug throughout a polymer matrix in a stabilized form. This innovative formulation was developed to enable targeted GI delivery in rodents through oral administration.
Methods: Ex vivo stability and solubility experiments were completed using freshly prepared fecal inoculum. Fresh fecal samples were acquired from six Wistar rats to produce a pooled sample of inoculum. Human inoculum was prepared using pooled fecal samples from three healthy subjects. A specially adapted basal media was used to preserve the viability of microbiota and accurately mimic the luminal environment of the large intestine. Each fecal inoculum was characterized for key physiological properties that affect solubility and stability, including pH, buffer capacity and protease activity. The solubility of the drug in each slurry was determined following 24 hours incubation at 37oC. Drug stability was determined by sampling at six time points over 24 hours from samples incubated in a specialist anaerobic workstation maintained at 37oC and 70% relative humidity.
ProRelease® microparticle formulations were fabricated using the pH-responsive polymer Eudragit® L100 at 10% drug loading. Eight different batches were prepared at varying conditions/compositions to optimize morphology, yield, encapsulation efficiency and dissolution profile of the microparticle formulation.
Results: Compound A was determined to be stable in both rat colon inoculum (0.018 mg/mL solubility) and human colon inoculum (0.03 mg/mL). The optimal microparticle formulation was prepared with compound A (300 mg) and Eudragit® L100 (2.7 g) using the innovative oil-in-oil emulsion solvent evaporation process. The robust spherical microparticles (Fig. 1) showed excellent morphology, size (<100µm) and size uniformity. The process was efficient with 99.4% yield, and 83% encapsulation efficiency. The in-vitro dissolution profile (Fig. 2) demonstrated optimal release to the distal gut in rats.
Conclusion: Compound A was determined to be stable in rat and human colonic inoculums. Robust, pH-responsive microparticles were successfully developed with an excellent release profile for colon targeted delivery of the drug candidate. The ProRelease® technology proved to be ideal for oral targeted delivery of drugs in rodent efficacy and safety studies.
Vipul Yadav– Director of Product Development, Intract Pharma Ltd., England
Sejal Ranmal– Director of Formulation, Intract Pharma Ltd., England
Abdul Basit– Professor, UCL School of Pharmacy, London, England
Lu Zeng– Director, Analytical Development, Takeda California, California