Cannabidiol (CBD) has become the most well-known non-intoxicating cannabinoid found in Cannabis sativa. It is also the subject of some controversy, as many advocates of plant-based medicines and cannabis in particular tout its myriad health benefits, while detractors note that there is limited evidence to support many of these claims. That being said, the United States Food and Drug Administration has approved its use (under the name Epidiolex®) for the treatment of specific types of epilepsy. Therefore, to deny its therapeutic value for specific conditions would be a mistake, but one should always be cautious about believing some of the hype about CBD.
That said, a new preprint study from the University of Chicago has found that CBD may prevent sustained SARS-CoV-2 infection. Researchers pretreated A549 human lung carcinoma cells with 0-10 μM of cannabinoid formulas for two hours, and then infected the cells with SARS-CoV-2. After 48 hours, they examined the cells for expression of the SARS-CoV-2 spike protein. What they found was that CBD had similar efficacy as other antivirals (URMC-099 and KPT-9274), and that it was at its most effective when it was administered without other cannabinoids. Additionally, one of the primary metabolites of CBD, 7-hydroxy-cannabidiol (7-OH-CBD), demonstrated similar efficacy and occurs in significantly higher blood plasma concentrations than its parent compound. CBD shows a maximal concentration in the nM range, while 7-OH-CBD has a maximal concentration in the μM range.
The team then examined a cohort of human patients who had been taking CBD and compared them to a cohort of patients who had similar demographic characteristics, clinical comorbidities, and medication histories. Records indicated that only 1.2% of the CBD group had tested positive for COVID-19. Within the non-CBD group, 12.2% had tested positive for COVID-19.
Researchers are still trying to fully understand the mechanism of action behind this phenomenon. What appears to be clear is that CBD’s antiviral effects are not mediated through cannabinoid receptors. Rather, CBD appears to prevent viral protein translation and associated cellular changes by amplifying intracellular interferon signaling pathways and suppressing SARS-CoV-2-induced changes in gene expression. In other words, CBD does not prevent viruses like SARS-CoV-2 from attaching to receptor proteins and infecting individual cells. It boosts the expression of the body’s natural defenses within the cell (whereas SARS-CoV-2 reduces the expression of these defenses), thereby preventing the virus from successfully hijacking the cellular mechanisms that allow for replication. As it does not target the viral spike protein, this suggests CBD might be effective at preventing the spread of SARS-CoV-2 variants, as well as other viruses. Perhaps most importantly, CBD is relatively inexpensive, widely available, and has a very good safety profile.
As noted above, these findings are still preliminary and need to be peer reviewed, but do seem extremely promising.
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