NCT-58 is a potent C-terminal HSP90 inhibitor. NCT-58 does not induce the heat shock response (HSR). NCT-58 elicits anti-tumor activity via the simultaneous downregulation of HER family members as well as inhibition of Akt phosphorylation. NCT-58 kills Trastuzumab-resistant breast cancer stem-like cells. NCT-58 induces apoptosis in HER2-positive breast cancer cells.

NCT-58 treatment (0.1-10 μM; 72 hours) increases the number of early and late apoptotic cells in HER2-positive BT474 and SKBR3 cells. NCT-58 treatment (0.1-20 μM; 72 hours) dose-dependently reduces cell viability in HER2-positive BT474 and SKBR3 cells. NCT-58 treatment (2-10 μM; 72 hours) effectively reduced the levels of truncated p95HER2 and its phosphorylated form, as well as downregulation of Akt and phospho-Akt (Ser473) protein contents in JIMT-1 and MDA-MB-453 cells [1].

NCT-58 (30 mg/kg; i.p.; every other day for 47 days) significantly impedes tumor growth, markedly reduces tumor weight, and effectively suppresses Trastuzumab-resistant tumor growth [1].