Computational screening for natural compounds as potential immune checkpoint inhibitors against TIGIT, a new avenue in cancer immunotherapy.

The TIGIT-PVR signalling pathway is a key mechanism of tumour immune evasion, making it an attractive target for cancer immunotherapy. Despite the recent advances in anti-TIGIT antibodies, monoclonal antibody-based therapeutics present significant challenges because of their immunogenicity and immune-related side effects. This study presents a new path involving natural compounds as potential small molecule inhibitors of TIGIT, providing a possible alternative to antibodies in cancer immunotherapy. Through a comprehensive in silico workflow combining structure-based virtual screening, ADMET analysis, Molecular docking and molecular dynamics simulations, six promising candidates, mostly of bacterial origin, were identified: Neomycin K, 4'-Deoxybutirosin A, 5-Glucosyl-neamine, S-11-A, 12-carbamoylstreptothricin E acid, and Zwittermicin A. These candidates demonstrated favourable binding energies, stable interactions, and the capacity to block TIGIT-PVR signalling. The compounds can potentially compete with PVR to bind to TIGIT, limiting the formation of the TIGIT-PVR complex, which typically activates an inhibitory cascade in T cells and NK cells, reducing their anti-tumour activity. By disrupting this interaction, the identified compounds have the potential to stimulate T cell and NK cell responses against cancer cells. Such natural compounds potentially provide better tissue penetration and reduced immunogenicity compared to conventional antibody therapies. The discovery of bacterial-derived compounds as TIGIT inhibitors presents a new direction in the investigation of microbial metabolites for cancer immunotherapy. This strategy not only identifies a new class of TIGIT inhibitors but also provides a robust computational framework for discovering and characterizing small molecule immune checkpoint inhibitors, paving the way for subsequent experimental validation to explore their efficacy in restoring anti-tumour immune responses and improving clinical outcomes for cancer patients.