Since its emergence in China in late 2019, ‘the Coronavirus’ has now deeply affected almost every country on earth. Effective treatment options for Coronavirus disease 2019 (Covid-19) have proved elusive due to the absence of effective target-based therapeutics. However, governments and pharmaceutical research companies have prioritised a search for an effective treatment or vaccine since the beginning of 2020, culminating in the approval of two vaccines in the UK to date.
SARS-CoV-2 is the name given to the virus that causes Covid-19. While SARS-CoV-2 is not the first Coronavirus to be contracted by humans, it has become prevalent in the population at epidemic proportions, triggering national lockdowns and halting international travel. A number of studies in the past year have aimed to assess whether the antiviral potency of some cannabinoids could play a role against the latest version of Coronavirus.
One of these studies used various approaches to understand the antiviral potential of cannabinoids against SARS-CoV-2.
What methods were used?
Researchers screened 32 cannabinoids – compounds produced by the cannabis plant – and evaluated their binding affinities with SARS-CoV-2. Five of these cannabinoids were subjected to further study through in vitro antiviral assays: Δ9-tetrahydrocannabinolic acid (Δ9-THCA), Δ9-tetrahydrocannabinol (Δ9-THC), cannabinol (CBN), cannabidiol acid (CBDA), and cannabidiol (CBD).
The five cannabinoids that were carried forward to in vitro studies were found by the computational studies to have a remarkable binding affinity to the predicted active pocket of the main protease of SARS-CoV-2 – SARS-CoV-2 Mpro. Of these five, CBD and Δ9-THC were found to have the highest affinity for binding to the active pocket of the virus.
The Results of in vitro Studies
When carried forward to in vitro studies, CBD and Δ9-THC were also found to have potent antiviral activity against SARS-CoV-2 Mpro. Δ9-THCA, CBN, and CBDA were also showed moderate antiviral activity.
CBD (cannabidiol) was found to be the most active compound, exhibiting higher inhibition for SARS-CoV-2 Mpro. It was observed that host cell survival ratio suddenly decreased with an administration of 50μM of CBD. However, 12.5μM of CBD was deemed safe for inhibiting SARS-CoV-2 without causing any cytotoxicity, in vitro. A similar concentration-dependent inhibition pattern was observed for Δ9-THCA.
The potential binding of CBD and Δ9-THC to inhibit SARS-CoV-2 Mpro could lead to blocking the translation procedure of the virus. In addition, this interaction may reduce pro-inflammatory cytokines levels in lung cells by acting as agonists of CB2R (cannabinoid receptor 2).
Relevant Potentials of Δ9-THC and CBD
Both CBD and Δ9-THC have been the subject of extensive research in recent years due to their potential in aiding the treatment of a variety of conditions. The cannabinoids have been deemed to have significant therapeutic potentials in conditions including Crohn’s Disease, epilepsy, Parkinson’s Disease, and multiple sclerosis, as well as in symptoms associated with cancer and cancer treatment.
In addition, Δ9-THC acts as a partial agonist ofCB1R and CBR2 and reportedly induces immunological and anti-inflammatory effects via activation of CB2R. While the administration of Δ9-THC, particularly at high concentrations, has some side effects such as increased anxiety, several studies have indicated that these side effects may be reduced when Δ9-THC is given in combination with CBD.
The authors of this study concluded that both CBD and Δ9-THC may have antiviral potential against SARS-CoV-2. The findings of this report lay the framework for the application of both cannabinoids in human clinical trials for the treatment of human Coronavirus infections. Dependent on the findings of future studies, CBD and Δ9-THC may be effective in isolation or when given in combination with other medications to treat Covid-19 patients.