Introduction

The coronavirus family recently gained a new member in SARS-CoV-2 to go along with SARS-CoV and MERS-CoV. Infection with SARS-CoV-2 causes COVID-19 which has rapidly become a pandemic (with at the time of writing millions infected and hundreds of thousands dead) requiring social distancing, leading to global shutdowns, resulting in a recession, and pushing healthcare infrastructures to the breaking point. This pandemic is demanding an urgent response and we need to rapidly find treatments which can be accomplished by using existing drugs. Thus, drug repurposing for COVID-19 has garnered mainstream attention which did not occur in previous epidemics (1).

Initially the response from China and elsewhere was for scientists to look at compounds tested previously against SARS and MERS almost exclusively (2). Ritonavir/lopinavir, remdesivir (repurposed from Ebola and FDA emergency approved), chloroquine and hydroxychloroquine (both now FDA emergency approved, see Supplementary Material) are the most well-known compounds currently in clinical trials. Other drug repurposing efforts have used computational approaches such as docking or biological network mining to identify molecules as candidates for future testing (2,3,4,1). Limitations of the text mining approach are that at the time of writing there had only been reports of approximately 450 molecules associated with other coronaviruses and many of these could likely be discounted due to no reported antiviral activity, toxicity and perhaps most important, the lack of FDA approved status.

Summary

We propose that in particular, cetylpyridinium chloride is a simple molecule that is cheap, safe, clinically approved, widely accessible in hospitals and the consumer sector and which could enter clinical trials immediately. If reported to have activity in vitro against SARS-CoV-2 subsequent delivery in the form of a mouthwash or nasal spray containing this compound may be an effective way both to combat the virus at its point of entry and reduce SARS-CoV-2 transmission. Similarly, this compound could be added to shampoo and body cleansers so that one could effectively bathe in low concentrations of this compound to destroy shed coronavirus. Cetylpyridinium chloride and many other quaternary ammonium compounds have already demonstrated their antiviral activity against a wide array of related coronaviruses as disinfectants and antiseptics, therefore they represent especially low hanging fruit for testing in humans. Due to their reported mechanisms they may also have much broader activity against viruses which could be useful to address future enveloped viruses. Certainly, additional studies may be warranted to assess potential drug-drug or drug-transporter interactions. This work may also point to other related compounds that could be utilized, or at least enable the generation of new antiviral compounds that leverage the quaternary ammonium substructural fragment as a potential warhead. As simple as it sounds, it is entirely possible that we should be looking in our bathroom cupboards, for potential remedies against COVID-19.