Cooper, G.; Snape, T. J.; Shivkumar, M.

Host-targeting antivirals offer a promising strategy for combating emerging viral threats by targeting cellular pathways required for infection. The p38 mitogen-activated protein kinase (MAPK) pathway has been implicated as a host dependency factor exploited by multiple viruses, including coronaviruses, making it an attractive antiviral target. Here, we show for the first time that targeted degradation of p38 using the proteolysis-targeting chimera (PROTAC) NR-7h potently inhibits coronavirus infection. NR-7h induced substantial degradation of p38 in multiple cell lines and inhibited infection of two seasonal coronaviruses OC43 and 229E, providing broad pan-coronavirus activity. Infectious viral titres and viral RNA levels were significantly reduced without any detectable cytotoxicity. NR-7h exhibited greater antiviral potency than conventional p38 small-molecule inhibitors, with an IC50 of 1.0 nM compared with 648.4 nM for LY2228820, while the parent kinase inhibitor PH-797804 did not achieve 50% inhibition at the highest concentration tested. Pseudovirus and time-of-addition studies indicated that antiviral activity occurred at a post-entry stage of infection. Importantly, antiviral activity was eliminated by inhibition of proteasome function or E3 ligase activity, demonstrating dependence on PROTAC-mediated degradation. Our findings provide a proof-of-concept that targeted degradation of host kinase p38 can function as an antiviral modality and suggest PROTAC-based host-directed therapeutics may offer advantages over conventional kinase inhibition for broad-spectrum antiviral development.