Laduviglusib (CHIR-99021) HCl

CHIR-99021 shows greater than 500-fold selectivity for GSK-3 versus its closest homologs CDC2 and ERK2, as well as other protein kinases. Furthermore, CHIR-99021 shows only weak binding to a panel of 22 pharmacologically relevant receptors and little inhibitory activity against a panel of 23 nonkinase enzymes. CHIR-99021 induces the activation of glycogen synthase (GS) in insulin receptor-expressing CHO-IR cells with EC50 of 0.763 μM. ^[1] In addition to simulating the actions of insulin, inhibition of GSK-3 by CHIR-99021 (3 μM) increases free cytosolic β-catenin by 1.9-fold, mimicking the canonical Wnt signaling pathway in 3T3-L1 preadipocytes. During any of the first 3 days of differentiation, CHIR-99021 treatment inhibits the preadipocyte differentiation with IC50 of 0.3 μM by blocking induction of CCAAT/enhancer-binding protein α (C/EBPα) and peroxisome proliferator-activated receptor γ (PPARγ). ^[2] Unlike lithium chloride and AR-A014418, CHIR-99021 treatment does not reduce the viability of INS-1E cells even at high concentrations. Instead, CHIR-99021 robustly increases the rate of proliferation of INS-1E cells in a dose-dependent manner, and significantly inhibits INS-E cell death induced by high glucose and high palmitate in a concentration-dependent manner. CHIR-99021 promotes primary beta cell replication in isolated rat islets at concentrations as low as 1 μM, with 2-3 fold increase of cell replication at 5 μM of CHIR-99021 treatment. ^[3]

Cells are maintained for 24 hours in starvation medium (culture medium with only 5 mM glucose, 1% fetal calf serum). Then cells are exposed to various concentrations of CHIR-99021 for 1, or 4 days. Cell number is measured by staining of cellular DNA with CyQuant dye, which becomes fluorescent when bound to DNA. Fluorescence is measured after 30 minutes of incubation using the FLUOstar Optima reader. Cell replication is determined by BrdUrd incorporation. BrdUrd labeling solution is added to the medium for the last 4 hours before the cells are fixed using FixDenat solution and incubated with monoclonal anti-BrdUrd-POD antibodies. After substrate solution is added to each well, the light emission is measured in a microplate luminometer using the Analyst HT detection system.

Oral administration of CHIR-99021 at 30 mg/kg enhances glucose metabolism in a rodent model of type 2 diabetes, with a maximal plasma glucose reduction of nearly 150 mg/dl 3-4 hours after administration, while plasma insulin remains at or below control levels. Oral administration of CHIR-99021 at 16 or 48 mg/kg 1 hour before oral glucose challenges in ZDF rats significantly improves glucose tolerance with 14% and 33% reduction in plasma glucose at 16 mg/kg and 48 mg/kg, respectively, and the higher dose of CHIR-99021 also reduces hyperglycemia before the oral glucose challenge. ^[1]