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Abstract: The SARS-CoV-2 papain-like protease PLpro has multiple roles in the viral replication cycle, related to both its polypeptide cleavage function and its ability to antagonize the host immune response. Targeting the PLpro function is recognized as a promising mechanism to modulate viral replication, while supporting host immune responses. However, the development of PLpro-specific inhibitors remains challenging. Comprehensive investigations utilizing enzymatic, binding studies, and cellular assays revealed the previously reported inhibitors to act in an unspecific manner. At present, GRL-0617 and its derivatives remain the best-validated compounds with demonstrated antiviral activity in cells and in mouse models. In this study, we refer to the pitfalls of the redox sensitivity of PLpro. Using a screening-based approach to identify inhibitors of PLpro’s proteolytic activity, we made extensive efforts to validate active compounds over a range of conditions and readouts, emphasizing the need for comprehensive orthogonal data when profiling putative PLpro inhibitors. The remaining active compound, CPI-169, was shown to be a noncovalent inhibitor capable of competing with GRL-0617 in NMR-based experiments, suggesting that it occupied a similar binding site and inhibited viral replication in Vero-E6 cells, opening new design opportunities for further development as antiviral agents.
Keywords: SARS-CoV-2, drug repurposing, papain-like protease, redox, STD-NMR, CPI-169, GRL-0617
Published in DiRROS: 20.08.2025; Views: 324; Downloads: 157
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Abstract: The molecular nanomachine, human DNA topoisomerase IIα, plays a crucial role in replication, transcription, and recombination by catalyzing topological changes in the DNA, rendering it an optimal target for cancer chemotherapy. Current clinical topoisomerase II poisons often cause secondary tumors as side effects due to the accumulation of double-strand breaks in the DNA, spurring the development of catalytic inhibitors. Here, we used a dynamic pharmacophore approach to develop catalytic inhibitors targeting the ATP binding site of human DNA topoisomerase IIα. Our screening of a library of nature-inspired compounds led to the discovery of a class of 3-(imidazol-2-yl) morpholines as potent catalytic inhibitors that bind to the ATPase domain. Further experimental and computational studies identified hit compound 17, which exhibited selectivity against the human DNA topoisomerase IIα versus human protein kinases, cytotoxicity against several human cancer cells, and did not induce DNA double-strand breaks, making it distinct from clinical topoisomerase II poisons. This study integrates an innovative natural product-inspired chemistry and successful implementation of a molecular design strategy that incorporates a dynamic component of ligand-target molecular recognition, with comprehensive experimental characterization leading to hit compounds with potential impact on the development of more efficient chemotherapies.
Keywords: topoisomerase II, catalytic inhibitors, chemotherapy, DNA damage, cancer
Published in DiRROS: 03.06.2024; Views: 1266; Downloads: 714
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