Discovery of novel pyrazolopyrimidine derivatives as potent mTOR/HDAC bi-functional inhibitors via pharmacophore-merging strategy

The mTOR and HDAC dual suppression is meaningful for counteracting drug resistance resulted from kinase mutation and bypass mechanisms. Herein, we communicate our recent discovery of a novel structural series of mTOR/HDAC bi-functional inhibitors featuring the pyrazolopyrimidine core via pharmacophore-merging strategy. More than half of them exerted potent dual-target inhibitory activities. In particular, compound 50 exhibited IC50 values of 0.49 and 0.91 nM against mTOR and HDAC1, respectively, along with remarkably enhanced anti-proliferative activity (IC50 = 1.74 μM) against MV4-11 cell line than mTOR inhibitor MLN-0128 (IC50 = 5.84 μM) and HDAC inhibitor SAHA (IC50 = 8.44 μM). Its intracellular intervention of both mTOR signaling and HDAC was validated by the Western blot analysis. Moreover, as the first disclosed mTOR/HDAC dual inhibitor with selectivity for some specific HDAC subtypes, it has the potential to alleviate the adverse effects resulted from pan-HDAC inhibition. Attributed to its favorable in vitro performance, compound 50 is valuable for further functional investigation as a polypharmacological anti-cancer agent.