PF-04928473

Novel furanone-based hybrids (series A-I) were designed and synthesized as potential anticancer agents and Hsp90 inhibitors using the privileged fragment combination strategy. NCI single-dose full panel assay identified 13b (series I) as the most active hit, demonstrating broad spectrum antiproliferative activity against 48 NCI cell lines (GI₅₀ = 2.17-9.60 μM) and exhibiting total growth inhibition in 26 cell lines (TGI = 6.23-91.00 μM), with minimal toxicity toward 57 cell lines (LC₅₀ > 92.5 μM) as revealed in the five-dose assay. 13b exerted strong cytotoxicity against MCF-7 and MDA-MB-231 cancer cells, with high selectivity over normal human skin fibroblast cells, according to the MTT assay. Mechanistic studies indicated that apoptosis was not the primary mechanism of activity. 13b suppressed proliferation by reducing colony formation and downregulating the proliferation marker Ki67. Additionally, it inhibited Hsp90, suppressed Hsp90 ATPase activity, downregulated client oncoproteins HER2 and CDK4, and induced a moderate Heat Shock Response. In a TNBC xenograft model, 13b significantly reduced tumor volume and weight with a better safety profile than 5-fluorouracil. Besides, 13b significantly suppressed EGFR expression as confirmed by immunohistochemistry analysis. In vivo pharmacokinetic studies revealed rapid systemic absorption (C_max = 6.74 μM, T_max = 1 h) and short half-life (T_1/2 = 2.98 h). Molecular docking studies showed that 13b binds within the Hsp90 ATP-binding pocket in a comparable pattern to the known inhibitors, SNX-2112 and GDM. These findings support 13b as a promising and well-tolerated Hsp90-targeted anticancer lead, especially for the treatment of breast cancer.