Prodrug-Based Targeting Approach for Inflammatory Bowel Diseases Therapy: Mechanistic Study of Phospholipid-Linker-Cyclosporine PLA2-Mediated Activation

Abstract

Therapeutics with activity specifically at the inflamed sites throughout the gastrointestinal tract (GIT) would be a major advance in our therapeutic approach to inflammatory bowel disease (IBD). We aimed to develop the prodrug approach that can allow such site-specific drug delivery. Currently, using cyclosporine as a drug of choice in IBD is limited to the most severe cases due to substantial systemic toxicities and narrow therapeutic index of this drug. Previously, we synthesized a series of a phospholipid-linker-cyclosporine (PLC) prodrugs designed to exploit the overexpression of phospholipase A2 (PLA2) in the inflamed intestinal tissues, as the prodrug-activating enzyme. Nevertheless, the extent and rate of prodrug activation differed significantly. In this study we applied in-vitro and modern in-silico tools based on molecular dynamics (MD) simulation, to gain insight into the dynamics and mechanisms of the PLC prodrug activation. We aimed to elucidate the reason for the significant activation change between different linker lengths in our prodrug design. Our work reveals that the PLC conjugate with the 12-carbon linker length yields the optimal prodrug activation by PLA2 in comparison to shorter linker length (6-carbons). This optimized length efficiently allows cyclosporine to be released from the prodrug to the active pocket of PLA2. This newly developed mechanistic approach, presented in this study, can be applied for future prodrug optimization to accomplish optimal prodrug activation and drug targeting in various conditions that include overexpression of PLA2.

Exploring the Anticonvulsant Properties of a Celecoxib-Phospholipid Conjugate: Synthesis, Activation, and Evaluation of Cytotoxicity

“…In summary, PLA2 hydrolysis of PLC prodrug is highly dependent on PLA2 enzyme concentrations. This supports our hypothesis that enzyme overexpression will result in selective activation of the prodrug, as opposed to the low enzyme concentrations reported in healthy tissues [18].…”

“…The mixture was then incubated for 1.5 hours at 25 °C. The samples were taken at 0, 5, 10, 15, 20, 30, 40, 60, and 90 minutes [18].…”

PLA2-Triggered Activation of Cyclosporine-Phospholipid Prodrug as a Drug Targeting Approach in Inflammatory Bowel Disease Therapy

“…Limitation of our approach lies in the fact that individual optimization in terms of the prodrug structure and linker length is needed for each parent drug, as demonstrated in our previous work [ 18 , 24 , 25 , 45 ]. Indeed, higher molecular weight drugs such as cyclosporine might require longer linkers for optimal activation [ 50 ] than the ones with lower molecular weight [ 45 , 51 , 52 , 53 ]. Nevertheless, advanced in-silico techniques are nowadays available, and we and others have previously shown just how useful they may be in optimization of the prodrug structure [ 45 , 50 , 51 , 52 , 54 , 55 , 56 ].…”

“…Indeed, higher molecular weight drugs such as cyclosporine might require longer linkers for optimal activation [ 50 ] than the ones with lower molecular weight [ 45 , 51 , 52 , 53 ]. Nevertheless, advanced in-silico techniques are nowadays available, and we and others have previously shown just how useful they may be in optimization of the prodrug structure [ 45 , 50 , 51 , 52 , 54 , 55 , 56 ]. Future avenues should explore the pharmacological effects of PL–cyclosporine prodrugs in novel genetically engineered or humanized IBD animal models, in addition to development of suitable formulations that would circumvent the gastric environment.…”