Structure-Based Design of Human TLR8-Specific Agonists with Augmented Potency and Adjuvanticity

Area of Science:

• Immunology
• Medicinal Chemistry

Background:

• Human Toll-like receptor 8 (hTLR8) is crucial for immune responses, particularly in myeloid dendritic cells and monocytes.
• TLR8 agonists stimulate cytokine profiles that promote type 1 helper T cell development.

Purpose of the Study:

• To enhance the potency of a known pure TLR8 agonist, 3-pentylquinoline-2-amine.
• To design novel TLR8 agonists by mimicking key interactions observed in crystal structures.

Main Methods:

• Focused exploration of decorating the quinoline core with alkylamino groups at various positions.
• Cocrystallization of hTLR8 ectodomain with dual TLR7/8-agonistic imidazoquinolines to analyze binding interactions.

Main Results:

• Identified a novel TLR8 agonist with approximately 20-fold increased potency compared to the parent compound.
• The new agonist exhibited significant adjuvantic activity in a rabbit immunization model.

Conclusions:

• Structural insights into hTLR8 binding enabled the rational design of a more potent agonist.
• The developed TLR8 agonist holds promise for enhancing vaccine efficacy through its adjuvantic properties.