Improved Oral Bioavailability and Gastrointestinal Stability of Amphotericin B through Fatty Acid Conjugation...

Amphotericin B (AmB) is one of the most effective drugs used in the treatment of leishmaniasis and systemic fungal infections. Considering the global burden of leishmaniasis, ∼90% of disease cases occur in developing countries, suggestive of the need for an affordable AmB therapy. However, owing to the physicochemical properties of AmB, all the clinically available formulations must be administered by intravenous route, thereby creating a significant hurdle in patients' access to AmB due to pharmacoeconomic considerations. We have previously demonstrated that lipid conjugation (e.g., fatty acids) to AmB significantly decreases the toxicity of resulting prodrug by a favorable alteration in the aggregation pattern. The hypothesis of the present work was to investigate the potential of the previously established AmB-lipid conjugate [AmB-oleyl conjugate (AmB-OA)] in improving the physicochemical properties such as gastric instability and lower intestinal permeability that otherwise limits the oral delivery of AmB. The synthesized AmB-OA conjugate was remarkably stable at gastric pH in contrast to AmB and exhibited significantly higher permeation across the Caco-2 monolayer (indicative of intestinal permeability). Mechanistic studies revealed that AmB-OA retained an equivalent antifungal activity. Also, AmB-OA was found to interact preferentially with intracellular membranes of Saccharomyces cerevisiae, while AmB interacted with the plasma membrane. The results of Caco-2 monolayer permeation experiments were further confirmed by in vivo pharmacokinetics, which showed that AmB-OA exhibited a 3.13-fold increase in the C_max and a 4.88-fold increase in AUC_Tot as compared to AmB. In conclusion, the lipid conjugation approach may provide an effective solution for current challenges in designing drug delivery systems intended for oral AmB therapy.