Structure Overhaul Affords a Potent Purine PI3Kδ Inhibitor with Improved Tolerability

Area of Science:

• Immunology
• Medicinal Chemistry
• Pharmacology

Background:

• Phosphoinositide 3-kinase delta (PI3Kδ) activity is crucial for immune cell activation.
• Overactive PI3Kδ and AKT pathways are linked to inflammatory diseases and hematological malignancies.
• A prior PI3Kδ inhibitor caused vascular injury in dogs, necessitating safety improvements.

Purpose of the Study:

• To develop a PI3Kδ inhibitor with an improved safety profile, specifically addressing vascular toxicity.
• To identify structural modifications that enhance ligand efficiency, kinome selectivity, and tolerability.

Main Methods:

• Structure-based drug design was employed to modify the inhibitor's core structure.
• Reconstruction of the benzimidazolone-piperidine selectivity motif was a key strategy.
• Advanced computational and synthetic chemistry techniques were utilized.

Main Results:

• Novel O- and N-linked heterocycloalkyl moieties, particularly pyrrolidines, were identified.
• These modifications resulted in highly ligand-efficient and kinome-selective compounds.
• A representative compound showed excellent tolerability in a dog study, with no signs of vascular injury.

Conclusions:

• Structural modifications to the PI3Kδ inhibitor successfully mitigated vascular toxicity observed in preclinical studies.
• Pyrrolidine-containing heterocycles represent a promising scaffold for developing safer PI3Kδ inhibitors.
• The findings support the advancement of these improved inhibitors for potential therapeutic applications.