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

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)