It’s amazing we aren’t at $2 with this publication. Here is a copy and paste of the Discussion...
Discussion
The ongoing global COVID-19 pandemic powerfully reinforces the need for thera- peutic strategies that can safely and effectively address virus- and host-based events elic- ited during SARS-CoV-2 infection.
In multiple studies, we have attempted to evaluate the capability of brilacidin to de- crease viral load in the context of the SARS-CoV-2 infection. Our experiments in the Vero cell line model demonstrate brilacidin decreases viral load in a robust manner when the virus is preincubated with brilacidin (Figure 2D), suggesting brilacidin impacts virus in- tegrity. Brilacidin’s ability to decrease viral load in an ACE2-positive cell line is demon- strated in Figures 3–5, in which Calu-3 cells were used.
All experiments conducted in Vero and Calu-3 cell line models were supportive of an early inhibition exerted by brilacidin on SARS-CoV-2, indicating the drug’s impact on viral integrity. The idea that brilacidin directly interferes with the integrity of the virion is further supported by the observation that when drug treatment was limited to the virus alone (Figure 2E), with no treatment of host cells, a robust decrease of viral load was still observed in both the Washington strain and the Italian strain of SARS-CoV-2. This mech- anism of inhibition may be akin to that achieved by neutralizing antibodies that may in- teract with specific exposed epitopes on the surface of virions. It remains to be determined if the impact of brilacidin on viral membranes is driven by specific viral membrane com- positions.
While brilacidin’s mechanism of action appears primarily to be extracellular, it may also impact intracellular viral replication and is planned to be researched further. Sup- portive of this, an in silico quantum mechanical molecular screening study of 11,522 com- pounds identified brilacidin as a potential inhibitor of SARS-CoV-2 based on the potential of its physicochemical properties to interfere with the intracellular replication of SARS- CoV-2's main protease (Mpro) [69].
The high CC50 (a measure of cytotoxicity) and low IC50 (a measure of potency) val- ues observed for brilacidin in Calu-3 cells—yielding a Selectivity Index (SI) for brilacidin of 426 (CC50 = 241 µM/IC50 = 0.565 µM)—strongly support brilacidin’s treatment poten- tial to achieve positive antiviral outcomes in humans. A vast majority of other drugs being evaluated as potential COVID-19 treatments, including repurposed drugs, have SIs that are much lower than that achieved by brilacidin [70], with most drugs failing to show anti- SARS-CoV-2 potency in the <1 µM range [71]. Of note, the IC50 (0.565 µM) and IC90 (2.63 µM) values for brilacidin observed in the Calu-3 cell line are well below clinically achiev- able concentrations based on pharmacokinetics observed in Phase 2 clinical trials with brilacidin for the treatment of Acute Bacterial Skin and Skin Structure Infections (ABSSSI). Applying the in vitro IC50 and IC90 parameter targets to in vivo human plasma concen- tration data, simulated dose regimens for brilacidin are similar to that already tested in clinical trials for ABSSSI and even exceed such targets, thereby further supporting the progression of brilacidin to clinical testing for treatment of COVID-19.
As of January 2021, FDA Investigational New Drug approval (with FDA Fast Track designation), and a similar regulatory approval from an overseas health authority, has been obtained for conduct of a multinational Phase 2 clinical trial of intravenously admin- istered brilacidin in hospitalized patients with COVID-19. Brilacidin has been tested in numerous human trials (a total of eight) for other clinical indications, providing estab- lished safety and efficacy data on over 460 subjects.
A desirable outcome for any potential COVID-19 therapeutic will be its ability to syn- ergize with existing COVID-19 treatments, particularly if the mechanisms of action of the synergistic treatments can impact more than one step of the viral lifecycle. Such combina- tions are more likely to elicit an additive response while also reducing the likelihood of viral resistance developing. Along these lines, we conducted experiments to evaluate the potential of brilacidin to work in conjunction with remdesivir and favipiravir (Figure 5), two frontline COVID-19 treatments, which proved supportive of synergistic inhibition between brilacidin and remdesivir. Remdesivir is a SARS-CoV-2 nucleotide analog RNA
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polymerase inhibitor that impacts the viral RNA synthesis step of the infectious process. By that mechanism, remdesivir may help decrease progeny viral genomes in infected cells but will not be conducive to inhibiting progressive infection of naïve cells once the prog- eny virions have been released from infected cells.
By combining remdesivir with brilacidin, a two-pronged strategy of inhibiting viral entry and viral RNA synthesis might be successfully leveraged to most effectively control progression of SARS-CoV-2 infection. The opportunity that combination treatments with brilacidin could potentially offer in treating COVID-19 requires further exploration, and in vivo animal studies are in planning stages.
Clearly, an effective COVID-19 therapeutic (or therapeutics in combination) ideally would control both viral load and the corresponding inflammatory damage due to SARS- CoV-2 [72], and mitigate bacterial coinfections. With its HDP mimetic properties—antivi- ral, immuno/anti-inflammatory, and antibacterial—brilacidin may be able to address the different disease parameters of COVID-19 within the one therapeutic treatment. The re- sults of the planned Phase 2 clinical trial, with intravenous treatment of COVID-19 in ad- dition to standard of care, are highly anticipated.
In this manuscript, we demonstrate brilacidin exhibits robust inhibition of SARS- CoV-2 in Vero cells and Calu-3 cells, and in two strains of the virus. Likely to function as a viral entry inhibitor [73-75], the proposed mechanism of action for brilacidin includes affecting the integrity of the viral membrane and interfering with viral entry. Brilacidin also exhibited an excellent synergistic inhibitory profile against SARS-CoV-2 in combina- tion with remdesivir. Destabilizing viral integrity is a desirable antiviral property, espe- cially in relation to pan-coronavirus agents, as the viral membrane is highly conserved and similar in construct across different coronavirus strains. Further research will be con- ducted in the context of other lethal coronaviruses (MERS-CoV, SARS-CoV) toward as- sessing the potential of brilacidin as a broad-spectrum inhibitor of coronaviruses.
Author Contributions: Conceptualization, A.B., A.N., T.L.C., W.K.W., and J.A.H.; Methodology, A.B., W.K.W., J.A.H.; A.B., K.R., N.B., F.A., and T.L.C. conducted experiments; Visualization, Formal analysis, Data curation, A.B., A.N., W.K.W., T.L.C., and J.A.H.; Writing—original draft preparation, A.B., A.N., W.K.W., and J.A.H.; Writing—review and editing, A.B., A.N., W.K.W., and J.A.H.; Pro- ject administration, A.N., W.K.W., and J.A.H.; Funding acquisition, A.N., W.K.W., and J.A.H. All authors have read and agreed to the published version of the manuscript.
Funding: George Mason University, with identified lead researcher Aarthi Narayanan, received fi- nancial support from Innovation Pharmaceuticals Inc. to conduct research on brilacidin’s antiviral properties.
Institutional Review Board Statement: Not applicable. Informed Consent Statement: Not applicable.
Data Availability Statement: All new data generated for this publication have been included in the current manuscript.
Acknowledgments: Authors thank William F. DeGrado (Department of Pharmaceutical Chemistry, University of California San Francisco) and Jun Wang (Department of Pharmacology and Toxicol- ogy, University of Arizona) for helpful discussions during this research project and for manuscript review. Authors acknowledge the contribution of Scott Van Wart from Enhanced Pharmacodynam- ics (ePD) to the analyses contributing to and generation of Figure 4.
Conflicts of Interest: Warren K. Weston serves as a consultant for Innovation Pharmaceuticals Inc.
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