NVP-BEP800 is a novel, fully synthetic HSP90β inhibitor with IC50 of 58 nM, exhibits>70-fold selectivity against Hsp90 family members Grp94 and Trap-1.
NVP-BEP800 is an ATP-competitive inhibitor of Hsp90β with an IC50 of 58 nM, exhibiting >70-fold selectivity against Hsp90 family members Grp94 and Trap-1 with IC50 values of 4.1 μM and 5.5 μM, respectively. NVP-BEP800 displays no inhibitory activity against the closely related GHKL ATPase, topoisomerase II, and the structurally unrelated ATPase, Hsp70 at the concentration of 10 μM. NVP-BEP800 potently inhibits the proliferation of various tumor cell lines with GI50 values ranging from 38 nM in A375 to 1.05 μM in PC3, and primary human tumors with the mean IC50 of 0.75 μM and IC70 of 1.8 μM. NVP-BEP800 treatment at the concentration of five times the GI50 increases the percentage of G2-M phase in A2058 and A549 cells and sub-G1 phase in BT-474, HCT116, A2058 and A549 cells by 29.5%, 33.6%, 42.7%, 12.1%, 5.9% and 7.1%, respectively. NVP-BEP800 treatment causes Akt and ErbB2 dephosphorylation, ErbB2 degradation, and Hsp70 induction in a concentration-dependent manner in BT-474 cells with IC50 values of 218 nM, 39.5 nM, 137 nM and 207 nM, respectively.
Oral administration of NVP-BEP800 at 15 or 30 mg/kg/day for 15 days causes a dose-dependent reduction in B-Raf and Akt phosphorylation levels, and displays significant dose-dependent antitumor efficacy in the A375 melanoma xenograft model with the T/C values of 53% and 6% at the dose of 15 and 30 mg/kg/day, respectively, suggesting almost complete tumor inhibition at 30 mg/kg/day. Administration of NVP-BEP800 induces dose-dependent increase of Hsp90-p23 complex dissociation and reductions in the levels of steady-state ErbB2, phospho-Akt and phospho-S6, in BT-474 breast cancer xenografts, and exhibits significant antitumor activity with 38% tumor regression at dose of 30 mg/kg/day and a T/C of 36% at dose of 15 mg/kg/day.
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