CSF1R-IN-15 (compound 23) serves as an inhibitor of the colony-stimulating factor-1 receptor (CSF1R), a tyrosine kinase located in the macrophage cell membrane. This receptor is activated by colony-stimulating factor-1 (CSF-1) and interleukin-34. Signaling through CSF1R is essential for the differentiation, proliferation, and survival of macrophages [1].

CSF1R-IN-15 displays no activity against Ba/F3 cells at concentrations ranging from 0.007 to 10 μM over 72 hours, whereas pexidartinib shows superior activity [1]. The compound's plasma protein binding was assessed through equilibrium dialysis. When incubated at 5 μM for 6 hours at 37°C, CSF1R-IN-15 demonstrated a 69% plasma protein binding rate in mouse plasma [1].

Pharmacokinetic parameters for CSF1R-IN-15 were derived from a boxed dosing study in C57BLKS mice. The observed values for half-life (t 1/2), initial concentration (C 0), area under the curve from zero to infinity (AUC 0-∞), observed clearance (CL obs), and steady-state volume of distribution (V ss,obs) were 0.5 hours, 37 ng/mL, 18 h*ng/mL, 54 L/h/kg, and 32 L/kg, respectively [1]. The study utilized an animal model for in vivo pharmacokinetics with a dosage of 1mg/kg administered intravenously (i.v.), in a single dose formulation of 20% DMSO and 80% PEG400. Blood samples were collected at 10, 30, 60, 120, 240, and 480 minutes post-administration. The results reaffirmed the pharmacokinetic parameters as t 1/2 (0.5 h), C 0 (37 ng/mL), AUC 0-∞ (18 h*ng/mL), CL obs (54 L/h/kg), and V ss,obs (32 L/kg).