Miniprotein engineering for inhibition of PD-1/PD-L1 interaction.

Area of Science:

• Biochemistry
• Molecular Biology
• Drug Discovery

Background:

• Miniproteins offer a stable scaffold for developing functional molecules.
• The programmed cell death protein 1/programmed death-ligand 1 (PD-1/PD-L1) pathway is a key regulator of immune responses and a target for cancer immunotherapy.

Purpose of the Study:

• To engineer miniprotein-based inhibitors of PD-1/PD-L1 interaction.
• To optimize these inhibitors for enhanced binding affinity and solubility.

Main Methods:

• Utilized computer-aided design for initial PD-L1 binder development.
• Employed iterative optimization and circular dichroism spectroscopy for conformational stability assessment.
• Incorporated charged amino acid residues to improve solubility.

Main Results:

• Successfully designed and optimized miniproteins that bind to PD-L1 with high affinity (K_D = 51.4 nM).
• Demonstrated inhibition of PD-1/PD-L1 interaction in cell-based assays with an EC₅₀ of 3.9 μM.
• Confirmed conformational stability of engineered miniproteins despite mutations.

Conclusions:

• Miniproteins, specifically the engrailed homeodomain scaffold, are effective for developing PD-1/PD-L1 inhibitors.
• The engineered miniprotein exhibits potent PD-L1 binding and functional inhibition.
• This approach provides a promising strategy for novel immunotherapeutic agents targeting the PD-1/PD-L1 axis.