From Lead to Drug Candidate: Optimization of 3-(Phenylethyny1)-1H-pyrazolo[3,4-d]pyrimidin-4-amine Derivatives as Agents for the Treatment of Triple Negative Breast Cancer

Herein we report the sophisticated process of structural optimization toward a previously disclosed Src inhibitor, compound 1, which showed high potency in the treatment of triple negative breast cancer (TNBC) both in vitro and in vivo but had considerable toxicity. A series of 3-(phenylethynyl)-1H-pyrazolo[3,4-d]pyrimidin-4-amine derivatives were synthesized. In vitro cell-based phenotypic screening together with in vivo assays and structure activity relationship (SAR) studies finally led to the discovery of N-(34(4-amino-1-(trans-4-hydroxycydohexyl)-1H-pyrazolo[3,4-4pyrimidin-3-ypethyny1)-4-methylphenyl)-4methyl-3-(trifluoromethyl)benzamide (13an). 13an is a multikinase inhibitor, which potently inhibited Src (IC50 = 0.003 mu M), KDR (IC50 = 0.032 mu M), and several kinases involved in the MAPK signal transduction. This compound showed potent antiTNBC activities both in vitro and in vivo, and good pharmacokinetic properties and low toxicity. Mechanisms of action of antiTNBC were also investigated. Collectively, the data obtained in this study indicate that 13an could be a promising thug candidate for the treatment of TNBC and hence merits further studies.