Combinatorial Drug Treatments Reveal Promising Anticytomegaloviral Profiles for Clinically Relevant Pharmaceutical Kinase Inhibitors (PKIs)

Abstract

Human cytomegalovirus (HCMV) is a human pathogenic herpesvirus associated with a variety of clinical symptoms. Current antiviral therapy is not always effective, so that improved drug classes and drug-targeting strategies are needed. Particularly host-directed antivirals, including pharmaceutical kinase inhibitors (PKIs), may help to overcome problems of drug resistance. Here, we focused on utilizing a selection of clinically relevant PKIs and determined their anticytomegaloviral efficacies. Particularly, PKIs directed to host or viral cyclin-dependent kinases, i.e., abemaciclib, LDC4297 and maribavir, exerted promising profiles against human and murine cytomegaloviruses. The anti-HCMV in vitro activity of the approved anti-cancer drug abemaciclib was confirmed in vivo using our luciferase-based murine cytomegalovirus (MCMV) animal model in immunocompetent mice. To assess drug combinations, we applied the Bliss independence checkerboard and Loewe additivity fixed-dose assays in parallel. Results revealed that (i) both affirmative approaches provided valuable information on anti-CMV drug efficacies and interactions, (ii) the analyzed combinations comprised additive, synergistic or antagonistic drug interactions consistent with the drugs’ antiviral mode-of-action, (iii) the selected PKIs, especially LDC4297, showed promising inhibitory profiles, not only against HCMV but also other α-, β- and γ-herpesviruses, and specifically, (iv) the combination treatment with LDC4297 and maribavir revealed a strong synergism against HCMV, which might open doors towards novel clinical options in the near future. Taken together, this study highlights the potential of therapeutic drug combinations of current developmental/preclinical PKIs.

Functional Relevance of the Interaction between Human Cyclins and the Cytomegalovirus-Encoded CDK-Like Protein Kinase pUL97

“…Interestingly, GCV or MBV are characterized by profound mechanistic differences, in that MBV is a classical inhibitor of the ATP binding site, whereas GCV is a prodrug that requires the activation of phosphorylation through pUL97 to develop antiviral activity. Due to these differences, the two drugs express an antagonistic effect upon cotreatment [ 63 ]. Irrespective of these mechanistic differences, both drugs share the necessity of proper access to their binding sites in pUL97 [ 64 ], so that the present data may support the idea that deleted regions might have a certain impact on these binding characteristics.…”

“…Here, the dimension of a viral replication defect was more drastic under combination treatment, thus demonstrating that some cellular kinase inhibitors enhanced the antiviral activity of MBV. Notably, our recent finding contributed to this notion, in that we identified a pronounced synergism of combination treatments with MBV and the CDK7-specific preclinical drug LDC4297, as quantitatively assessed by two established drug combination assays [ 63 ]. This may refer to the crosstalk and functional complementation between active cellular CDK–cyclin complexes and the viral CDK ortholog pUL97.…”

Methodological Development of a Multi-Readout Assay for the Assessment of Antiviral Drugs against SARS-CoV-2

“…Additionally, the combinatorial drug treatment of SARS-CoV-2 infection was analyzed using the d6-YFP reporter system. To this end, the Loewe additivity fixed-dose assay was performed under conditions applied from our previous studies [ 18 ]. Essentially, the cotreatment with RDV plus GC376 was expected to have a non-antagonistic, possibly additive or synergistic effect, considering the fact that the two drugs acted in mechanistically different modes of action (MoA), i.e., a nsp12 replication complex-directed MoA by nucleoside analog RDV, and a 3CL pro -directed MoA by the protease inhibitor GC376.…”

Recent Advances in Kinase Drug Discovery Part I: The Editors’ Take

“… Recent advances in kinase drug discovery span the drug discovery pipeline from target identification through to pharmacovigilance. These advances are illustrated in six primary research articles covering kinome array profiling [ 4 ], structure-guided drug development [ 5 , 6 ], rational computational design [ 7 ], targeting the protein/peptide substrate binding site [ 8 ] and combinatorial drug treatment [ 9 ]; and nine topical reviews on TAO kinases [ 10 ], liver disease [ 11 ], AMPK [ 3 ], pancreatic cancer [ 12 ], urothelial carcinoma [ 13 ], Flaviviridae infections [ 14 ], squamous cell carcinoma [ 15 ], thyroid cancer [ 16 ] and adverse reactions to JAK inhibitors [ 17 ]. The indicated figures from special issue papers have been re-used with permission from the authors.…”

“…The potential of host-directed anti-virals is confirmed by Wild and co-authors [ 9 ], who use both cell-based and animal models to assess the potential effectiveness of three cyclin-dependent kinase (CDK) inhibitors (abemaciclib, LDC4297 and maribavir) in the treatment of human cytomegaloviral (HCMV) infection, both alone and in combination. Their data demonstrate the effectiveness of these compounds against human, as well as, in some cases, murine CMV and other members of the herpes virus family.…”