XL888

XL888 induces HER2 degradation in NCI-N87 cells with IC50 of 56 nM. XL888 inhibits the proliferation of HER2 over-expressed NCI-N87, HER2 over-expressed BT-474, HER2 over-expressed MDA-MB-453, MET mutated MKN45, B-Raf mutated Colo-205, B-Raf mutated SK-MEL-28, EGFR mutated HN5, EGFR mutated NCI-H1975, PI3K mutated MCF7, and K-Ras mutated A549 with IC50 of 21.8, 0.1, 16.0, 45.5, 11.6, 0.3, 5.5, 0.7, 4.1 and 4.3 nM. ^[1] The growth inhibitory effects of XL888 are associated with induction of either a G₁-phase cell-cycle arrest (WM164, M229, M229R, M249, M249R, 1205Lu, and WM39 cell lines) or a G₂-M phase cell-cycle arrest (WM164R, 1205LuR, and RPMI 7951 cell lines). XL888 (300 nmol) induces high levels ( > 66%) of apoptosis, and loss of mitochondrial membrane potential (TMRM) in these cell lines. The cytotoxic effects of XL888 are durable with no signs of colony formation observed in any of the cell lines even cultured up to 4 weeks. Treatment with XL888 (300 nM) leads to robust time-dependent increases in the expression of HSP70 isoform 1. XL888 (48 hours, 300 nM) treatment increases the expression of BIM-EL, BIM-L, and BIM-S expression in the M229R, 1205LuR, RPMI7951, and WM39 cell lines, induces expression of BIM-L and BIM-S in the WM164R cell line, and BIM-EL in the M249R cell line. ^[2]

Cells are plated at a density of 2?0⁵ per mL and left to grow overnight before being treated with increasing concentrations of XL888. After incubation with XL888 for 3 days, Methylthiazolyldiphenyl-tetrazolium bromide (MTT) assays are performed.

XL888 (100 mg/kg) significantly induces the regression of, or growth inhibition (50%) of established M229R and 1205LuR xenografts in SCID mice. 15 days of XL888 treatment showes a robust (8.6-fold) increase in intratumoral HSP70 expression compared with controls. XL888 treatment is noted to be proapoptotic in vivo and leads to increased TUNEL staining in M229R xenografts associated with increased expression of BIM and decreased expression of Mcl-1. ^[2]