Discovery of Affinity-Based Probes for Btk Occupancy Assays

Area of Science:

• Biochemistry
• Pharmacology
• Medicinal Chemistry

Background:

• Bruton's tyrosine kinase (Btk) is a key target for treating B-cell malignancies and autoimmune diseases.
• Covalent irreversible Btk inhibitors targeting Cys481 are in clinical development.
• Pharmacodynamic (PD) studies require probe molecules to assess target engagement and guide dosage.

Purpose of the Study:

• To develop a potent and selective affinity-based biotinylated probe for Btk.
• To utilize the probe in occupancy assays for preclinical evaluation of Btk inhibitors.

Main Methods:

• Design and synthesis of a biotinylated probe based on a pyridine carboxamide scaffold.
• Development of a novel solvent-accessible pocket (SAP) inhibitor series.
• Application of the probe (Compound 12) in Btk occupancy assays.

Main Results:

• A potent and selective affinity-based biotinylated probe (Compound 12) was successfully developed.
• Compound 12 was utilized in Btk occupancy assays for preclinical studies.
• The probe facilitated assessment of Btk inhibition efficacy in mouse lupus models.

Conclusions:

• The developed biotinylated probe is a valuable tool for Btk occupancy studies.
• This probe aids in optimizing dosage and evaluating therapeutic efficacy of Btk inhibitors.
• The findings support the successful preclinical evaluation of Btk inhibitors in autoimmune disease models.