Targeting the endolysosomal host-SARS-CoV-2 interface by clinically licensed functional inhibitors of acid sphingomyelinase (FIASMA) including the antidepressant fluoxetine

Abstract

The Coronavirus Disease 2019 (COVID-19) pandemic caused by the Severe Acute Respiratory Syndrome Related Coronavirus 2 (SARS-CoV-2) is a global health emergency. As only very limited therapeutic options are clinically available, there is an urgent need for the rapid development of safe, effective, and globally available pharmaceuticals that inhibit SARS-CoV-2 entry and ameliorate COVID-19 severity. In this study, we explored the use of small compounds acting on the homeostasis of the endolysosomal host-pathogen interface, to fight SARS-CoV-2 infection. We find that fluoxetine, a widely used antidepressant and a functional inhibitor of acid sphingomyelinase (FIASMA), efficiently inhibited the entry and propagation of SARS-CoV-2 in the cell culture model without cytotoxic effects and also exerted potent antiviral activity against two currently circulating influenza A virus subtypes, an effect which was also observed upon treatment with the FIASMAs amiodarone and imipramine. Mechanistically, fluoxetine induced both impaired endolysosomal acidification and the accumulation of cholesterol within the endosomes. As the FIASMA group consists of a large number of small compounds that are well-tolerated and widely used for a broad range of clinical applications, exploring these licensed pharmaceuticals may offer a variety of promising antivirals for host-directed therapy to counteract enveloped viruses, including SARS-CoV-2.

SARS-CoV-2 Cellular Infection and Therapeutic Opportunities: Lessons Learned from Ebola Virus

“…Moreover, SARS-CoV-2 specifically interacts with tyrosine-protein kinase receptor UFO (Axl) on the host membrane, where this receptor can promote viral entry [ 13 ], as already described for EBOV ( Figure 1 A,B). Interestingly and also previously reported for EBOV, fluoxetine, a functional inhibitor of ASMase, efficiently abrogates the SARS-CoV-2 entry and propagation in Vero E6 and CaLu-3 cells, suggesting that ASMase may also play a significant role in the early steps of the virus infection cycle [ 3 , 14 ]. A further understanding of the role of attachment factors implicated in SARS-CoV-2 binding will be required to reduce systemic dissemination between susceptible cells and tissues.…”

Antihistamine and cationic amphiphilic drugs, old molecules as new tools against the COVID-19?

“…Cationic and amphiphilic represent key physicochemical characteristics of a newly proposed classification of drugs related to their ability of acid sphingomyelinase (ASM) inhibition and called Functional Inhibitors of Acid SphingoMyelinase (FIASMAs) [ 7 ],. This property could also be linked to the endolysosomal anti-SARS-CoV-2 activity and of the 11 drugs described above, 7 are indeed confirmed FIASMAs [ 6 , 8 , 9 ].…”

Fluoxetine pharmacokinetics and tissue distribution suggest a possible role in reducing SARS-CoV-2 titers

“…Comparing the Hoertel et al and Zimniak et al publications, Hoertel et al found that in addition to fluoxetine, venlafaxine (median dose of 75mg) and escitalopram (median dose of 10mg) were also associated with a lower risk of intubation and death, however, Zimniak et al showed neither SSRIs escitalopram nor paroxetine inhibited SARS-Cov-2 in vitro (Hoertel et al, 2020;Zimniak et al, 2020). Of note, as shown in Table 1, a 40mg or 60mg daily fluoxetine dose results in 90% inhibition of the SARS-Cov-2 infection due to surpassing the EC90 value of 4.02 μM as found in Calu-3 cells and the EC90 value of 1.81 μM in Vero E6 cells (Schloer et al, 2020).…”

“…Specifically, Zimniak et al reported that following a 3-day incubation period of fluoxetine in Vero cells, inoculated at a multiplicity of infection (MOI) of 0.5, resulted in the median maximal effective concentration (EC50) of 387 ng/ml (1.1 μM) and further found a concentration of 800 ng/ml (2.3 μM) significantly inhibited SARS-Cov-2 replication (Zimniak et al, 2020). Similarly, Schloer et al found that fluoxetine significantly decreases SARS-Cov-2 titers, after a 48-hour incubation period, in both African green monkey kidney epithelial Vero E6 cells (EC50 = 0.69 μM and 90% maximal effective concentration [EC90] = 1.81 μM, MOI=0.01) and human-lung Calu-3 cells (EC50 = 0.82 μM and EC90 = 4.02 μM, MOI=0.1) (Schloer et al, 2020). Taken together, these in vitro studies prove in a dose-dependent manner, the SSRI fluoxetine inhibits the SARS-CoV-2 pathogen known to cause the worldwide pandemic, the novel coronavirus disease 2019 .…”

“…With the whole-blood to plasma fluoxetine concentration -that is the fraction unbound in plasma -being 0.94 and having whole-blood to lung distribution coefficient of 60, the EC50 and EC90 values would need to be 6% higher than the aforementioned EC50 and EC90 results to then scale the final expected plasma concentration to 1/60 that of the final lung concentration (Sommi, Crismon & Bowden, 1987;Johnson, Lewis & Angier, 2007). For all calculations, the trough target plasma concentration is referenced from the Schloer et al study who reported after a 48-hour incubation period in Calu-3 lung cells the 90% maximal effective concentration is 4.02 μM (Schloer et al, 2020) which is significantly higher than the EC90 in Vero E6 cells (1.81 μM) and EC50 results from Zimniak et al and the Schloer et al studies (Schloer et al, 2020;Zimniak et al, 2020).…”