Novel 1,3,4-trisubstituted pyrazolopyrimidine derivatives show potent antiproliferative activity in mantle cell lymphoma

Background: Pyrazolopyrimidine scaffold is an important pharmacophore in drug discovery. This pharmacophore has been reported to produce numerous biological activities, of which anticancer is an important one. The development of novel pyrazolopyrimidine derivatives is of great importance for antitumor drug research. Objective: Compound 6, a pyrazolopyrimidine derivative reported by our group, showed weak antiproliferative activity with IC50 values of over 30 μM against mantle cell lymphoma (MCL) cell lines. In this study, we will further perform the structural optimization of compound 6 to screen highly active pyrazolopyrimidine derivatives. Methods: A novel series of 1,3,4-trisubstituted pyrazolopyrimidine derivatives were synthesized and their structures were elucidated by 1H-NMR, 13C-NMR, and HRMS. The antiproliferative activities of target compounds against MCL cell lines (Mino, Jeko-1, and Z138) were evaluated by the CellTiter-Glo luminescent cell viability assay. The effect of representative compounds to induce apoptosis was evaluated by Annexin V/Propidium Iodide (PI)-binding assay. Mitochondrial membrane potential and reactive oxygen species (ROS) levels in 15c-treated Z138 cells were tested by JC-1 and DCFH-DA probes, respectively. Results: Most compounds demonstrated improved antiproliferative activity against MCL cell lines compared to the lead compound 6, especially 15c, 15f, 15g, 15j, and 15o, with IC50 values at low micromolar levels. In addition, compound 15c could induce apoptosis in a dose-dependent manner in Z138 cells through reduction of mitochondrial membrane potential and enhancing reactive oxygen species production. Conclusion: The results showed that 1,3,4-trisubstituted pyrazolopyrimidine derivatives could be valuable lead compounds for the further development of anti-lymphoma agents.