Bivalent CK2 Inhibition as a Potent Strategy Against SARS-CoV-2 and Other Coronaviruses

Protein kinase CK2 is a ubiquitously expressed serine/threonine kinase that has emerged as a key host factor exploited by several viruses, including SARS-CoV-2. This study set out to investigate the role of CK2 subunits in SARS-CoV-2 replication and to evaluate the antiviral potential and broad-spectrum anti-coronavirus activity of two CK2 inhibitors: the previously described ATP-competitive inhibitor CX-4945 and a newly developed, highly selective bivalent inhibitor, AB668.

Using siRNA-mediated knockdown of CK2 subunits, the researchers found that reducing CK2 significantly decreased SARS-CoV-2 replication, highlighting the kinase's essential role in the viral lifecycle. Co-immunoprecipitation assays showed that the SARS-CoV-2 nucleoprotein interacts with CK2, and bio-layer interferometry demonstrated that the nucleoprotein specifically binds to the tetrameric CK2 holoenzyme (CK2₂β₂) but not to individual CK2α or CK2β subunits.

Pharmacological inhibition of CK2 with AB668 produced potent antiviral activity, significantly reducing viral replication by targeting a pre-replicative or RNA-replicative step of the viral lifecycle. AB668 also displayed broad-spectrum antiviral activity, effectively inhibiting both HCoV-OC43 (a beta-coronavirus) and HCoV-229E (an alpha-coronavirus).

The findings establish CK2 as a critical host factor for SARS-CoV-2 replication and identify AB668 as a promising candidate for broad-spectrum antiviral therapy. With its high selectivity, minimized off-target effects, and efficacy against multiple coronaviruses, AB668 represents a valuable chemobiological and therapeutic tool.