An Antiherpesviral Host-Directed Strategy Based on CDK7 Covalently Binding Drugs: Target-Selective, Picomolar-Dose,...

Area of Science:

• Virology
• Drug Discovery
• Molecular Biology

Background:

• Current direct-acting antivirals (DAAs) for viruses like SARS-CoV-2, HIV-1, and HCMV face limitations due to drug resistance and side effects.
• Host-directed antivirals (HDAs) offer an alternative strategy by targeting host proteins essential for viral replication.
• Host protein kinases, informed by cancer therapy research, are identified as potential HDA targets.

Purpose of the Study:

• To develop and evaluate novel, selective host-directed antivirals (HDAs) targeting the host kinase CDK7.
• To investigate the efficacy and mechanism of action of 3D structure-derived CDK7 inhibitors with covalent binding capabilities.
• To assess the potential of this HDA strategy against human cytomegalovirus (HCMV) and other herpesviruses.

Main Methods:

• In vitro kinase assays to verify CDK7 inhibition and selectivity, confirming covalent binding.
• Cell-based infection models to assess antiviral efficacy and determine half-maximal effective concentrations (EC50).
• Infection assays in human fibroblasts to evaluate potency against HCMV strains and recombinants.
• Western blot analysis to determine the mechanism of action and timing of viral replication block.
• Drug synergism assays (Loewe additivity) and testing against drug-resistant viral mutants.

Main Results:

• Selective CDK7 inhibitors with covalent binding warheads were synthesized and validated in vitro.
• Hit compounds demonstrated highly potent antiviral activity, with EC50 values in the picomolar range.
• Compounds showed strong efficacy against HCMV, other animal cytomegaloviruses (CMVs), and Varicella-zoster virus (VZV).
• A unique mechanistic property observed was an immediate block of early HCMV replication.
• Significant drug synergism was observed when combined with MBV, and compounds were effective against HCMV mutants resistant to existing therapies.

Conclusions:

• The study validates CDK7 as a viable HDA target for novel antiviral drug development.
• Covalently binding, selective CDK7 inhibitors exhibit potent and broad-spectrum antiviral activity, particularly against HCMV.
• This host-directed antiviral strategy holds significant developmental potential for overcoming limitations of current antiviral therapies.