Drug synergy of combinatory treatment with remdesivir and the repurposed drugs fluoxetine and itraconazole effectively impairs SARS-CoV-2 infection in vitro

Abstract

Background and purpose: The SARS-COV-2 pandemic and the global spread of coronavirus disease 2019 (COVID-19) urgently call for efficient and safe antiviral treatment strategies. A straightforward approach to speed up drug development at lower costs is drug repurposing. Here, we investigated the therapeutic potential of targeting the interface of SARS CoV-2 with the host via repurposing of clinically licensed drugs and evaluated their use in combinatory treatments with virus- and host-directed drugs in vitro.

Experimental approach: We tested the antiviral potential of the antifungal itraconazole and the antidepressant fluoxetine on the production of infectious SARS-CoV-2 particles in the polarized Calu-3 cell culture model and evaluated the added benefit of a combinatory use of these host-directed drugs with the direct acting antiviral remdesivir, an inhibitor of viral RNA polymerase.

Key results: Drug treatments were well-tolerated and potently impaired viral replication. Importantly, both itraconazole-remdesivir and fluoxetine-remdesivir combinations inhibited the production of infectious SARS-CoV-2 particles > 90% and displayed synergistic effects, as determined in commonly used reference models for drug interaction.

Conclusion and implications: Itraconazole-remdesivir and fluoxetine-remdesivir combinations are promising starting points for therapeutic options to control SARS-CoV-2 infection and severe progression of COVID-19.

Keywords: SARS-CoV-2; combination therapy; drug repurposing; fluoxetine; itraconazole; remdesivir.

FIGURE 1

Analysis of itraconazole‐mediated reduction of SARS‐CoV‐2 replication. Calu‐3 and Vero E6 cells were infected with 0.1 multiplicity of infection (MOI) of SARS‐CoV‐2. At 2 hours post‐infection (hpi), cells were treated with itraconazole at the indicated concentrations. (a) Mean infectious viral titres ± SEM, (b) mean per cent inhibition ± SEM of SARS‐CoV‐2 replication, with mean virus titre in control cells (treated with the solvent DMSO) set to 100%; n = 5. LogEC₅₀ and LogEC₉₀ values were determined by fitting a four‐parameter non‐linear regression model (Calu‐3: EC₅₀ = 0.43 μM, EC₉₀ = 2.46 μM; Vero E6: EC₅₀ = 0.39 μM, EC₉₀ = 0.87 μM)

FIGURE 2

Antiviral activities of treatments. Infectious virus production in polarized Calu‐3 cells treated with two‐drug combinations as indicated 2 hours post‐infection (hpi). Each symbol represents plaque‐forming units (PFU) per ml detected in a single experimental sample; lines indicate means; n = 5 per treatment

FIGURE 3

Antiviral activities of single and combination treatments. Polarized Calu‐3 cells were treated with the indicated drug combinations for 48 h. (a) Single treatment; (b) combinatory treatment. Each symbol represents mean per cent inhibition ± SEM of infectious virus production, with mean virus titre produced in control cells (treated with the solvent DMSO) set to 100%; n = 5. Dotted line, 90% reduction in viral titre

FIGURE 4

Evaluation of the pharmacological interactions of itraconazole and remdesivir (ItraRem). zero interaction potency (ZIP), Bliss independence and highest single agent (HSA) reference models were used to assess the interaction landscapes and to identify areas of synergy. Interaction surfaces are colour coded according to the synergy scores of the responses

FIGURE 5

Evaluation of the pharmacological interactions of fluoxetine and remdesivir (FluoRem). zero interaction potency (ZIP), Bliss independence and highest single agent (HSA) reference models were used to assess the interaction landscapes and to identify areas of synergy. Interaction surfaces are colour coded according to the synergy scores of the responses