Discovery of 3-Ethyl-4-(3-isopropyl-4-(4-(1-methyl-1 H-pyrazol-4-yl)-1 H-imidazol-1-yl)-1 H-pyrazolo[3,4- b]pyridin-1-yl)benzamide (TAS-116) as a Potent, Selective, and Orally Available HSP90 Inhibitor.
Uno, T., Kawai, Y., Yamashita, S., Oshiumi, H., Yoshimura, C., Mizutani, T., Suzuki, T., Chong, K.T., Shigeno, K., Ohkubo, M., Kodama, Y., Muraoka, H., Funabashi, K., Takahashi, K., Ohkubo, S., Kitade, M.(2019) J Med Chem 62: 531-551
- PubMed: 30525599 
- DOI: https://doi.org/10.1021/acs.jmedchem.8b01085
- Primary Citation of Related Structures:  
5ZR3 - PubMed Abstract: 
The molecular chaperone heat shock protein 90 (HSP90) is a promising target for cancer therapy, as it assists in the stabilization of cancer-related proteins, promoting cancer cell growth, and survival. A novel series of HSP90 inhibitors were discovered by structure-activity relationship (SAR)-based optimization of an initial hit compound 11a having a 4-(4-(quinolin-3-yl)-1 H-indol-1-yl)benzamide structure. The pyrazolo[3,4- b]pyridine derivative, 16e (TAS-116), is a selective inhibitor of HSP90α and HSP90β among the HSP90 family proteins and exhibits oral availability in mice. The X-ray cocrystal structure of the 16e analogue 16d demonstrated a unique binding mode at the N-terminal ATP binding site. Oral administration of 16e demonstrated potent antitumor effects in an NCI-H1975 xenograft mouse model without significant body weight loss.
Organizational Affiliation: 
Discovery and Preclinical Research Division , Taiho Pharmaceutical Co. Ltd. , Tsukuba , Ibaraki 300-2611 , Japan.