Small-molecule factor D inhibitors targeting the alternative complement pathway

Area of Science:

• Immunology
• Biochemistry
• Drug Discovery

Background:

• The complement system, part of innate immunity, eliminates pathogens.
• Complement component 3 (C3) is central to complement activation via classical, lectin, and alternative pathways.
• Factor D (FD) protease is crucial for alternative pathway amplification, implicated in diseases like AMD and PNH when dysregulated.

Purpose of the Study:

• To identify potent and selective small-molecule inhibitors of factor D (FD).
• To evaluate the efficacy of these inhibitors in blocking alternative pathway (AP) activation.
• To assess the therapeutic potential of FD inhibitors for complement-mediated diseases.

Main Methods:

• Identification and characterization of small-molecule FD inhibitors.
• Assessment of inhibitor activity on AP activation and C3 deposition.
• In vivo studies using FD-humanized mice to evaluate oral administration and inhibition of LPS-induced AP activation.

Main Results:

• Developed potent and selective small-molecule inhibitors of FD.
• Inhibitors efficiently blocked AP activation, C3 deposition, and lysis of PNH erythrocytes.
• Oral administration of inhibitors suppressed LPS-induced AP activation in vivo.

Conclusions:

• Small-molecule inhibition of the alternative pathway is feasible.
• FD inhibitors demonstrate therapeutic potential for complement-mediated diseases.
• Further development of FD inhibitors is supported by these findings.