IMB-A3, an isoindolinone derivative, functions as a molecular glue to promote CRBN-mediated ubiquitination and degradation of enterovirus A71 2C protein.

EV-A71 is one of the main culprits causing hand-foot-mouth disease in children. Currently, there are no specific drugs for the prevention and treatment of EV-A71 infection. In our previous studies, a series of 2-aryl-isoindolin-1-one compounds were found to exhibit anti-EV-A71 activity, among which IMB-A3 demonstrated the most potent antiviral activity. Here, we systematically characterized the in vitro and in vivo antiviral efficacy of IMB-A3 and investigated its mechanism of action. The results showed that IMB-A3 treatment decreased the levels of EV-A71 VP1 protein and viral RNA in the infected cells and mice muscles. IMB-A3 could effectively protected mice from lethal EV-A71 infection. Mechanism studies have shown that IMB-A3 interacts directly with the EV-A71 2C protein, but IMB-A3 has no effect on the ATPase and helicase activities of the 2C protein. Interestingly, IMB-A3 acts as a molecular glue to facilitate the interaction between 2C and CRBN, thereby promoting the ubiquitination and degradation of the N-terminal region of the 2C protein and exerting an antiviral effect. These findings indicate that IMB-A3 is a degrader of the EV-A71 2C protein, providing a basis for the future design and development of targeted degraders of the EV-A71 2C protein.