Design, synthesis and biological evaluation of pyrrolopyrimidine derivatives as novel and selective positive modulator of the small conductance Ca2+-activated K+ channels

Novel SK channel positive modulators prevent ferroptosis and excitotoxicity in neuronal cells

Small conductance calcium-activated potassium (SK) channel activity has been proposed to play a role in the pathology of several neurological diseases. Besides regulating plasma membrane excitability, SK channel activation provides neuroprotection against ferroptotic cell death by reducing mitochondrial Ca2+ uptake and reactive oxygen species (ROS). In this study, we employed a multifaceted approach, integrating structure-based and computational techniques, to strategically design and synthesize an innovative class of potent small-molecule SK2 channel modifiers through highly efficient multicomponent reactions (MCRs). The compounds' neuroprotective activity was compared with the well-studied SK positive modulator, CyPPA. Pharmacological SK channel activation by selected compounds confers neuroprotection against ferroptosis at low nanomolar ranges compared to CyPPA, that mediates protection at micromolar concentrations, as shown by an MTT assay, real-time cell impedance measurements and propidium iodide staining (PI). These novel compounds suppress increased mitochondrial ROS and Ca2+ level induced by ferroptosis inducer RSL3. Moreover, axonal degeneration was rescued by these novel SK channel activators in primary mouse neurons and they attenuated glutamate-induced neuronal excitability, as shown via microelectrode array. Meanwhile, functional afterhyperpolarization of the novel SK2 channel modulators was validated by electrophysiological measurements showing more current change induced by the novel modulators than the reference compound, CyPPA. These data support the notion that SK2 channel activation can represent a therapeutic target for brain diseases in which ferroptosis and excitotoxicity contribute to the pathology.

Design and discovery of novel pyrazole-pyrrolopyrimidine derivatives as anti-glioma agents via promoting apoptosis, inhibiting cell cycle and EGFR-TK

Glioma is an aggressive type of brain malignancy responsible for significant morbidity and mortality. In the current scenario, epidermal growth factor receptor (EGFR) kinases targeted therapy showed significant benefits in glioma patients. Therefore, in the present study, we intend to investigate the anti-glioma potential of a novel class of pyrazole-pyrrolopyrimidine derivatives and their mechanism of action. The compounds will be synthesized in a straight-forward synthetic route in excellent yields and subsequently tested for EGFR kinase inhibition. The compounds showed a diverse range of inhibitory activity against EGFR (IC50  = 3.4-873.2 nM). With an IC50 of 1.5 nM, compound 4i was determined to be the most effective EGFR inhibitor, even superior to the standard erlotinib (IC50 2.3 nM). Among them, the three most potent compounds (4i, 4j, and 4k) were further subjected to the anticancer activity against the panel of various cancer cell lines MCF-7 (breast cancer), A549 (lung cancer), U87 (glioblastoma cell)-EGFR-Wild Type, U87 (mutant glioblastoma cells) EGFR-mutant cell, MCF-12A (normal cells). The compound 4i showed the most potent activity against glioblastoma cells as compared to other cancer cells. The effect of compound 4i was also studied on the apoptosis of U87 cells, where it showed induction of apoptosis in a concentration-dependent manner. It also showed inhibition of the G2/M cell cycle phase of U87 cells. Our study demonstrated the development of novel pyrazole-pyrrolopyrimidine derivatives as a novel class of anti-glioma agents.