Alphaviruses, such as Ross River virus (RRV), Barmah Forest virus (BFV), and chikungunya virus (CHIKV), are notorious for causing severe joint pain and inflammation, conditions for which effective therapeutic solutions are an ongoing challenge. The increasing global burden of these viruses has expedited the need to fast-track treatments to mitigate these impacts. In this study, we used molecular docking to optimise a drug repurposing strategy by identifying licensed ligands that bind to the viral capsid protein with high affinity, potency, and efficiency.
In-silico screening of 2509 FDA-approved drugs found 9 bound with a high affinity to the RRV, BFV, and/or CHIKV capsid. These included drugs licensed for use in cardiac conditions, antineoplastic agents, antibiotics, antifungals, and anticoagulants. The antifungal drug A11N showed high affinity for all three (CHIKV, BFV, and RRV) viral capsids and was further explored in vitro and in vivo to confirm the in silico findings.
Surface plasmon resonance was used to validate the in silico screen and confirmed that A11N binds with high affinity to the protease region of the alphavirus capsid with KD in the nanomolar range. To functionally characterise A11N, we show that the drug IC50 for RRV, BFV, and CHIKV was 9.39µM, 12.14µM, and 20µM, respectively, highlighting its potent antiviral properties and confirming the value of the in silico screening method.
The A11N binding targeting the capsid protease was further explored using qPCR, confocal microscopy and western blot analysis with results suggesting a novel mechanism for disrupting capsid protein release and structural polyprotein processing. Interestingly, A11N shows preliminary activity against different flaviviruses, further showcasing its broad-spectrum potential.
This study lays the foundation for further development of A11N as a versatile antiviral agent, potentially relieving the public health burden of these diseases.