Novel phthalimides regulating PD-1/PD-L1 interaction as potential immunotherapy agents

Area of Science:

• Immunology
• Pharmacology
• Oncology

Background:

• Programmed cell death 1 (PD-1) and its ligand PD-L1 are crucial immune checkpoints in cancer.
• Small-molecule inhibitors offer advantages over antibodies for targeting PD-1/PD-L1, but their development lags.
• Rational drug design based on structural insights can improve small-molecule inhibitor efficacy.

Purpose of the Study:

• To design and synthesize novel small-molecule inhibitors targeting the PD-1/PD-L1 interaction.
• To identify a potent small-molecule inhibitor with improved binding capacity and therapeutic potential.
• To evaluate the efficacy and safety of the lead compound in preclinical models.

Main Methods:

• Structure-based drug design utilizing docking studies.
• Synthesis of novel phthalimide derivatives.
• Biochemical assays to determine inhibitory activity (IC50).
• Co-crystal structural analysis to elucidate mechanism of action.
• In vitro and in vivo efficacy studies, including assessment of immune cell activity and tumor growth inhibition.
• Safety profiling (LD50 determination).

Main Results:

• A series of novel phthalimide derivatives were synthesized.
• Compound P39 demonstrated potent inhibition of PD-1/PD-L1 interaction (IC50 = 8.9 nmol/L).
• Co-crystal data revealed P39 induces PD-L1 dimerization, blocking PD-1 binding.
• P39 enhanced immune cell-mediated killing of cancer cells.
• P39 exhibited a favorable safety profile (LD50 > 5000 mg/kg) and significant in vivo antitumor activity.
• P39 promoted CD8+ T cell activation.

Conclusions:

• P39 is a highly promising small-molecule inhibitor targeting the PD-1/PD-L1 axis.
• The rational design approach, incorporating aromatic linkers, successfully enhanced binding affinity.
• P39 demonstrates potential to improve the efficacy of T-cell-based cancer immunotherapy.