Synthesis, structure-activity relationship studies and biological characterization of new [1,2,4]triazolo[1,5-a]pyrimidine-based LSD1/KDM1A inhibitors

The histone lysine specific demethylase 1 (LSD1/KDM1A) is implicated in the development of cancers, targeting LSD1 has been recognized as a promising strategy for cancer therapy. To date, some small-molecule inhibitors are currently being investigated in clinical trials. Herein we report the design, synthesis and biochemical characterization of [1,2,4]triazolo[1,5-a]pyrimidine derivatives as new LSD1 inhibitors. Of these compounds, compound C26 inhibited LSD1 in a reversible manner (IC50 = 1.72 μM) and showed selectivity to LSD1 over MAO-A/B. Besides, compound C26 displayed FAD-competitive binding to LSD1. Interestingly, C26 did not inhibit horseradish peroxidase (HRP) and quench H2O2, thus excluding the possibility that LSD1 inhibition by C26 was due to the HRP inhibition and consumption of H2O2. In LSD1 overexpressed A549 cells, compound C26 concentration-dependently induced accumulation of H3K4me1/me2 and H3K9me2 and showed cellular target engagement to LSD1. Additionally, compound C26 significantly inhibited migration of A549 cells in a concentration-dependent manner, further western blot analysis showed that C26 increased expression levels of epithelial cell markers E-Cadherin and Claudin-1, down-regulated mesenchymal cell marker N-Cadherin and the upstream transcription factors Snail and Slug. Docking studies were also performed to rationalize the potency of C26 toward LSD1. To conclude, the [1,2,4]triazolo[1,5-a]pyrimidine could serve as a promising scaffold for the development of new LSD1 inhibitors.