Solubilizer Tag Effect on PD-L1/Inhibitor Binding Properties for m-Terphenyl Derivatives

Area of Science:

• Medicinal Chemistry
• Immunology
• Structural Biology

Background:

• Anti-programmed cell death ligand 1 (PD-L1) therapies are crucial in cancer treatment.
• Small-molecule inhibitors offer an alternative to antibody-based approaches but face design challenges.
• The influence of specific structural components, like solubilizer tags, on inhibitor efficacy is not fully understood.

Purpose of the Study:

• To systematically outline principles for designing effective anti-PD-L1 small-molecule inhibitors.
• To investigate the impact of the solubilizer tag on inhibitor affinity for PD-L1.
• To elucidate the structure-activity relationships of m-terphenyl-based PD-L1 inhibitors.

Main Methods:

• Design and synthesis of m-terphenyl-based small-molecule inhibitors.
• Homogeneous time-resolved fluorescence (HTRF) assays to measure PD-1/PD-L1 complex inhibition.
• Cell-based assays to evaluate inhibitor potency.
• X-ray crystallography to determine the co-structure of the inhibitor with PD-L1.
• Molecular modeling studies.

Main Results:

• A novel small-molecule inhibitor based on the m-terphenyl scaffold was developed.
• The study highlights the significant, often overlooked, contribution of the solubilizer tag to PD-L1 binding affinity.
• Crystal structure and modeling data elucidated the binding mode and interactions.
• The m-terphenyl scaffold's geometry was confirmed as a strong pharmacophore feature.

Conclusions:

• Successful anti-PD-L1 small-molecule inhibitor design requires careful consideration of both the core scaffold and solubilizer tag.
• The solubilizer tag plays a complex role, including potential PD-L1 homodimer stabilization.
• These findings provide a framework for optimizing future small-molecule inhibitor development against PD-L1.