CH5138303 is an orally available Hsp90 inhibitor with Kd of 0.48 nM.

HSP90 α:0.48 nM(Kd)

CH5138303 shows high affinity to Hsp90αand potent cell growth inhibitory activity against an HCT116 colorectal cancer cell line and an NCI-N87 gastric cancer cell line with IC50 of 98 nM and 66 nM, respectively. [1] Besides, CH5138303 also demonstrates liver microsomal stability. [1]

CH5138303 (50 mg/kg p.o.) displays high oral bioavailability in mice and produces potent antitumor efficacy in a human NCI-N87 gastric cancer xenograft model.[1]

Surface plasmon resonance direct binding assay for Hsp90α: Measurements are performed on a Biacore2000 at a flow rate of 30 μL/min, 25 °C in 50 mM Tris-based saline, pH 7.6, 0.005% Tween20 and 1% DMSO. Biotinylated N-terminal Hsp90α (9–236) is coupled on a streptavidin-coated surface of a sensorchip to a density of ca. 2000 RU.

HCT116 cell line and NCI-N87 cell line are cultured according to the supplier's instructions. Cells suspended in a medium are added to solutions containing various concentrations of the test substance, and the cells are cultured at 37 °C in 5% CO2. Four days later, Cell Counting Kit-8 solution is added and absorbance at 450 nm is measured with Microplate-Reader iMark. Antiproliferative activity is calculated by the formula (1?T/C) × 100 (%), where T represents the absorbance of drug-treated cells and C that of untreated control cells at 450 nm. The 50% inhibition concentration (IC50) values are calculated using Microsoft Excel 2007.(Only for Reference)