Purpose: Recent studies have demonstrated the potential for a triglyceride (TG) mimetic prodrug to promote the delivery of mycophenolic acid (MPA) to the lymphatic system. Here, the metabolic pathways that facilitate the lymphatic transport of the TG prodrug (1,3-dipalmitoyl-2-mycophenoloyl glycerol, 2-MPA-TG) were examined to better inform the design of next generation prodrugs.
Methods: In vitro hydrolysis experiments in simulated intestinal conditions and in vivo rat lymphatic transport experiments were conducted in the presence and absence of orlistat and A922500 (inhibitors of lipolysis and TG re-esterification, respectively), to evaluate the importance of 2-MPA-TG digestion and re-esterification of 2-MPA-MG (the 2-monoglyceride derivative) in promoting lymphatic transport.
Results: 2-MPA-TG was rapidly hydrolysed to 2-MPA-MG on incubation with fresh bile and pancreatic fluid (BPF), but not in simulated gastric fluid, heat-inactivated BPF or BPF + orlistat. Orlistat markedly decreased lymphatic transport and systemic exposure of 2-MPA-TG derivatives suggesting that inhibition of pancreatic lipase hindered luminal digestion and absorption of the prodrug. A922500 also significantly decreased lymphatic transport of 2-MPA-TG but redirected MPA to the portal blood, suggesting that hindered re-acylation of 2-MPA-MG resulted in intracellular degradation.
Conclusion: Incorporation into TG deacylation-reacylation pathways is a critical determinant of the utility of lymph directed TG-mimetic prodrugs.