Culex mosquitoes are the primary vectors of the Japanese encephalitis virus (JEV). Since its discovery in 1935, Japanese encephalitis (JE), caused by JEV, has posed a significant threat to human health. Despite the widespread implementation of several JEV vaccines, the transmission chain of JEV in the natural ecosystem has not changed, and the vector of transmission cannot be eradicated. Therefore, JEV is still the focus of attention for flaviviruses. At present, there is no clinically specific drug for JE treatment. JEV infection is a complex interaction between the virus and the host cell, which is the focus of drug design and development. An overview of antivirals that target JEV elements and host factors is presented in this review. In addition, drugs that balance antiviral effects and host protection by regulating innate immunity, inflammation, apoptosis, or necrosis are reviewed to treat JE effectively.

Background: Japanese encephalitis virus (JEV), a mosquito-borne flavivirus, remains a leading cause of viral encephalitis. Current management is largely supportive, with no specific antivirals. This study evaluated the antiviral efficacy and mechanism of action of CC-90009 against JEV in vitro and in vivo. Methods: Five targeted protein degraders (TPDs) were screened for anti-JEV activity in the human neuroblastoma cell line SH-SY5Y. Time-of-addition, binding, and endocytosis assays were used to delineate the phase of action of CC-90009, a cereblon (CRBN) E3 ligase modulator (CELMoD) and molecular glue degrader. Small interfering RNA knockdown and co-immunoprecipitation (Co-IP) confirmed targets essential for its antiviral effects. The broad-spectrum activity of CC-90009 against other mosquito-borne viruses was also evaluated. In vivo efficacy was tested in a murine JEV model. Results: Of the five TPDs tested, only CC-90009 significantly inhibited JEV infection in SH-SY5Y cells, acting during both viral entry and post-entry phases without reducing adsorbed or internalised virions. CC-90009 reduced JEV RNA and non-structural protein accumulation. Knockdown of G1-to-S phase transition 1 (GSPT1), a key target of CC-90009, suppressed JEV infection and translation; Co-IP confirmed GSPT1 interaction with JEV non-structural protein 5 (NS5). CC-90009 disrupted JEV translation and replication by inducing proteasomal degradation of the GSPT1/NS5 complex, further demonstrating its broad-spectrum antiviral activity through the effective inhibition of West Nile virus and chikungunya virus. In vivo, it protected mice from JEV-induced mortality, reducing viral load, antigen levels, and brain pathology. Conclusions: CC-90009 exerts potent anti-JEV activity both in vitro and in vivo by inducing proteasomal degradation of the GSPT1/NS5 complex, thereby disrupting viral translation and replication. This targeted protein degradation strategy represents a novel host-directed antiviral approach with promising therapeutic potential against mosquito-borne viral encephalitis.