NVP-HSP990 (HSP990) is an effective and specific HSP90α/β inhibitor (IC50: 0.6 /0.8 nM).

HSP90 β:0.8 nM, HSP90 α:0.6 nM

NVP-HSP990 is based on a 2-amino-4-methyl-7,8-dihydropyrido[4,3-d]pyrimidin-5(6H)-one scaffold, which is structurally distinct from other known HSP90 inhibitors. NVP-HSP990 binds to the N-terminal ATP-binding domain of HSP90. NVP-HSP990 exhibits single digit nanomolar IC50 values on three of the HSP90 isoforms (HSP90α, HSP90β, and GRP94) and 320 nM IC50 value on the fourth (TRAP-1), with selectivity against unrelated enzymes, receptors, and kinases. NVP-HSP990 dissociates the HSP90-p23 complex, depleted client protein c-Met, and induced Hsp70 in c-Met amplified GTL-16 gastric tumor cells. NVP-HSP990 potently inhibites the growth of human cell lines and primary patient samples from a variety of tumor types. [1] NVP-HSP990 displays dose- and time-dependent effects on HSP90 client proteins. NVP-HSP990 inhibits Glioma tumor-initiating cells (GIC) proliferation in all GIC lines, with IC50 values ranging approximately between 10 and 500 nM. Olig2 is a functional marker associated with cell proliferation and response to NVP-HSP990, as NVP-HSP990 attenuated cell proliferation in Olig2-high GIC lines. In addition, NVP-HSP990 disrupted cell-cycle control mechanism by decreasing CDK2 and CDK4 and elevating apoptosis-related molecules. [2]

NVP-HSP990 exhibits drug-like pharmaceutical and pharmacologic properties with high oral bioavailability. In the GTL-16 xenograft model, a single oral administration of 15 mg/kg of NVP-HSP990 induced sustained downregulation of c-Met and upregulation of Hsp70. In repeat dosing studies, NVP-HSP990 treatment resulted in tumor growth inhibition of GTL-16 and other human tumor xenograft models driven by well-defined oncogenic HSP90 client proteins. [1]

HSP90 binding, ATPase, and selectivity profiling assays: The potency of HSP90 inhibitors for HSP90α, HSP90β, and Grp94 is determined by AlphaScreen competition binding assays, and activity against TRAP-1 is assessed by an ATPase assay.

Dissociated GICs are plated at 10 cells/μL in 6-well plates and incubated with various concentrations of NVP-HSP990 for 7 days. Formed tumorspheres are dissociated into single cells and counted with hemocytometer using 0.2% Trypan blue exclusion. (Only for Reference)