MEP Pathway: First-Synthesized IspH-Directed Prodrugs with Potent Antimycobacterial Activity.

Area of Science:

• Medicinal Chemistry
• Biochemistry
• Microbiology

Background:

• The 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway is essential for bacterial survival.
• Targeting the terminal enzyme, (E)-4-hydroxy-3-methylbut-2-enyl diphosphate reductase (IspH or LytB), offers a potential strategy for antimycobacterial drug development.
• Prodrug strategies can enhance the delivery and efficacy of phosphorylated inhibitors.

Purpose of the Study:

• To synthesize and evaluate novel IspH-directed prodrugs.
• To investigate the impact of substituents on prodrug permeability and antimycobacterial activity.
• To establish the efficacy of the cycloSaligenyl (cycloSal) prodrug approach for delivering phosphorylated inhibitors.

Main Methods:

• Synthesis of alkyne and pyridine monophosphate cycloSal prodrugs with varying substituents (electron-withdrawing and donating).
• Evaluation of prodrugs against Mycobacterium smegmatis using agar diffusion assays.
• Assessment of structure-activity relationships, including amino acid-functionalized and mutual prodrug analogs.

Main Results:

• Chlorine-substituted derivatives (5c and 6c) exhibited potent antimycobacterial activity against Mycobacterium smegmatis.
• These compounds demonstrated superior activity compared to isoniazid in agar diffusion assays.
• Electron-withdrawing substituents were found to accelerate prodrug hydrolysis and intracellular release of the active inhibitor.

Conclusions:

• The study presents the first experimental evidence for an IspH-targeted prodrug approach.
• The cycloSal prodrug strategy is effective for delivering phosphorylated inhibitors.
• This work paves the way for developing novel antimycobacterial agents targeting the MEP pathway.