Structure-Guided In Vitro to In Vivo Pharmacokinetic Optimization of Propargyl-Linked Antifolates

Area of Science:

• Medicinal Chemistry
• Pharmacology
• Drug Discovery

Background:

• Antibiotic efficacy correlates with pharmacokinetic/pharmacodynamic (PK/PD) properties.
• Propargyl-linked antifolates show broad-spectrum activity, including against multidrug-resistant *Staphylococcus aureus*.
• Optimizing PK profiles is crucial for translating potent in vitro activity to in vivo efficacy.

Purpose of the Study:

• To optimize the pharmacokinetic profile of propargyl-linked antifolates.
• To enhance metabolic stability and in vivo half-life while retaining antibacterial potency.
• To develop a compound with a favorable human PK profile and reduced drug-drug interaction potential.

Main Methods:

• Utilized high-resolution crystal structures and in vitro pharmacokinetic models for rational drug design.
• Employed structure-based drug design to mitigate metabolic liabilities like N-oxidation.
• Incorporated deuterium and fluorine substitutions to modulate oxidative demethylation rates.
• Assessed metabolic stability using mouse liver microsomes and evaluated efficacy in a mouse disease model.

Main Results:

• Identified and mitigated key metabolic pathways (N-oxidation, demethylation) responsible for the short half-life of the lead compound.
• Developed a novel antifolate derivative with significantly improved metabolic stability and in vivo half-life.
• The optimized compound demonstrated a low projected human clearance and limited cytochrome P450 inhibition.
• Achieved an in vivo exposure profile conducive to bactericidal activity in a preclinical model.

Conclusions:

• Structure-based drug design combined with strategic substitutions effectively enhances the metabolic stability of antifolates.
• The optimized compound exhibits promising pharmacokinetic properties for potential clinical development.
• This approach provides a powerful strategy for developing novel antibiotics with improved therapeutic potential.