ThePineapple - [Part 3/3] Blocking COVID Infections With Cannabinoids ?

[Part 3/3] Blocking COVID-19 infections with cannabinoids?

What you should know about cannabis and COVID-19

Of late, there has been a little bit of a media frenzy surrounding two recent scientific papers that provide us with data suggesting cannabinoids could be used to block the coronavirus (SARS-CoV-2) from binding its target cells and trigger an innate immune response. In other words, potentially mitigating COVID-19 infections in the early stages. This has naturally led to a lot of excitement but also a lot of wrong conclusions, because the conversation often fails to provide the right context within the overall big picture of COVID.  If you have arrived at this article after reading part 2 then you should be properly prepared to go over the new and exciting cannabinoid research that we will discuss below. Otherwise, I suggest you start there before continuing with the analysis of those research papers below.

Part 1: What you should know about Cannabis and COVID-19

Part 2: The COVID side of this story

Part 3: Blocking COVID infections with cannabinoids ? <--- you are here

So far, everything I have been telling you about concerns the full blown COVID-19 disease. Why it is dangerous, what some severe complications are and how cannabis can interact with drugs used to treat those complications. Those are all important, because that is what people are dying from and this information is the most relevant when you are already feeling sick and tested positive for COVID-19. But let’s circle back to the beginning. The first step of the disease is infection itself. Blood clots and cytokine storm only become a problem after you have been infected and after your immune system has failed to clear the infection. So blocking the infection in the first place would be great. This is where the two publications come in that made the news over the last few weeks. The first is a research paper with the title :

Cannabinoids Block Cellular Entry of SARS-CoV-2 and the Emerging Variants.  

van Breemen, R. B., Muchiri, R. N., Bates, T. A., Weinstein, J. B., Leier, H. C., Farley, S., & Tafesse, F. G. (2022). Journal of natural products, 85(1), 176–184.

The premise behind that research is simple. The virus needs to attach itself to the surface of a cell in order to infect it. The virus achieves this by binding with its own “spike” protein to the ACE2 receptor that sits on the surface of the target cell. So, if you can block the spike protein from binding the ACE2 receptor, well then the virus can no longer infect the cell. Small molecule blockers like this have been a valid strategy for fighting viral infections in the past like HIV or Hepatitis C.

In their paper the group from Oregon State University identified that the precursor acids of several cannabinoids (THCA-A, CBDA and CBGA) were able to bind to the s1 subunit of the viral spike protein. More importantly the group provided two sets of cell-culture data that supports the idea that not only do the cannabinoids bind to the virus' spike protein, but they are also able to interfere with the virus at the point of cell entry. In other words, block the virus from entering the cultured cells in vitro. This piece of information is what had the internet in a frenzy and made people believe that smoking cannabis or consuming edibles could prevent COVID-19 infections. This is not the case.

First, the cannabinoids that the authors talked about are cannabinoid acids. Those acids are lost in the process of heating them. That means if you smoke cannabis, or bake edibles the heat will cause those acids to be decarboxylated and your THCA turns into THC, CBDA into CBD and CBGA into CBG. However, the authors themselves showed that decarboxylated cannabinoids did not have the same binding affinity to the spike protein as those acids. So if you are “theoretically” looking to use cannabinoids to block the virus from entering your cells you would have to consume the acids directly. Second, all the data in this publication is in vitro data. In vitro means that all the experiments were done in a petri dish on a bench. It wouldn’t be the first time that you find a small molecule inhibitor in vitro, then test it in a living animal model, in vivo only to discover that the effect is lost, because instead of binding to your viral target it all gets stuck to serum albumin or something. This happens all the time. So on a tier list from discovery to human application this is the lowest tier possible. You discover something in vitro, then you bring it in vivo into animals, usually mice and rats, before you finally progress to the clinical trial stage, which by itself has another 3 phases.

At any one of those steps your treatment can fail. In fact, most fail. So that means that yes this is interesting data and someone should absolutely feed CBDA pills to some mice, but we are really getting ahead of ourselves here. Another question that remains unanswered is what happens if the virus mutates and the cannabinoid acids no longer fit the spike protein? After all, this is how newer virus variants are evading neutralizing antibodies still present from previous infections or vaccinations. The authors of the article recognize this possibility but argue that there might be less of a selective pressure against cannabinoids and so the hope is that future variants won’t adapt as quickly to the cannabinoid acid block than the neutralizing antibodies. But whether or not that is actually the case, we won’t be able to tell until someone designs an experiment to clarify this.So can cannabinoid acids block the virus from infecting cells in living humans ? - We don’t know yet. It is definitely strong maybe. Either way, the blocking ability of “neutralizing antibodies” created by vaccination still remains exponentially stronger. In general, there really isn’t anything that has a stronger binding affinity than an antibody for its antigen. So even if cannabinoid acids could interfere with the virus' ability to bind to the ACE-2 receptor in living humans like it did in cell-culture, then the question still remains how it compares to antibodies. The author’s argument that viruses might be less likely to adapt to cannabinoids than antibodies might be true. But at the moment we have no evidence to support this.

Now let’s have a look at the second paper that made a splash online and that I personally find a lot more compelling :

Cannabidiol Inhibits SARS-CoV-2 Replication and Promotes the Host Innate Immune Response.

Nguyen, L. C., Yang, D., Nicolaescu, V., Best, T. J., Ohtsuki, T., Chen, S. N., Friesen, J. B., Drayman, N., Mohamed, A., Dann, C., Silva, D., Gula, H., Jones, K. A., Millis, J. M., Dickinson, B. C., Tay, S., Oakes, S. A., Pauli, G. F., Meltzer, D. O., Randall, G., … Rosner, M. R. (2021). 2021.03.10.432967.

This research was actually already publicly available in pre-print online for the better part of a year, but it was only fully published on the 20th of January 2022. So it hit the mainstream news after the other one we just discussed, even though it came out first and is even referenced in the other paper. Go figure. What makes this paper more compelling to me is a that :

A) in addition to in vitro bench data that authors also provides supporting in vivo animal data, B) it provides a compelling mechanistic explanation on the gene level, C) and gives us a first glimpse that their findings may hold true in humans

But what are the actual findings ? Well, CBD has been previously shown to have antiviral properties against hepatitis C and other viruses. Therefore, the goal of this study was “to determine whether cannabidiol (CBD), a natural product extracted from the cannabis plant, has the potential to inhibit infection of cells by SARS-CoV-2.” To achieve this the authors first cultured three different human and monkey cell lines in the lab and infected them with synthetic SARS-CoV-2 pseudovirus after pre-treating the cells with either CBD or appropriate controls. As a side note, if you are wondering about what a pseudovirus is. Well, it is essentially a synthetic virus that can be created in a lab and has very similar properties to the real thing, while also being less dangerous to work with. This is important, since you would otherwise need a biosafety level 4 certification for your lab. S4 labs are rare and so the biomedical community came up with this workaround to allow more researchers to work on COVID-19. But let’s return to the findings. The author's key discovery is that CBD and its metabolite 7-OH-CBD were able to significantly reduce the ability of the virus to replicate inside the cultured cells. In contrast to the previous paper we discussed, the authors of this paper did not find that the virus was blocked from entering the cells. But rather that the virus was not able to replicate properly in cells that were pretreated with either CBD or 7-OH-CBD. At this point it should be pointed out that CBD and 7-OH-CBD were the only cannabinoids that showed the desired effect. Other cannabinoids like CBDA, CBDV or THC either showed very little activity, no activity at all or worse, in the case of THC, reversed the beneficial anti-viral properties recorded for CBD and 7-OH-CBD. So right off the bat this should tell you that the discoveries in those two papers do not apply to cannabis containing THC. But more on that later. First, let’s return to the data and discuss the findings in a little bit more detail. What makes this paper so compelling in my eyes is that the authors didn’t just stop at recording the effect of CBD on viral replication but came up with a good explanation as to how it all works and provided supporting evidence that might actually be a good kick-off point for a systematic clinical trial. 

The COVID causing virus is a single-stranded RNA virus. That means its genome is made of RNA rather than DNA. In our own human cells the genetic information is stored in the form of DNA. The DNA encodes the information for all the various proteins and enzymes in our body. But in order to create those proteins a complex intracellular protein synthesis machine has to read the DNA, transcribe the information into RNA, translate that into amino-acid strings and finally fold and assemble those strings into their proper 3-dimensional structures. The virus cannot do any of that by itself, so it hijacks our cell’s protein synthesis machinery in order to create and assemble its components. Sort of like a biological “man-in-the-middle” attack.

So where does CBD fit into this ? - You see, as with so many systems of the body the protein synthesis machinery of the cell is complex and highly regulated. That means along each step of the process the cell has “sensors” in place that allow it to quantify and monitor whether everything is functioning as it is supposed to. When stuff goes wrong with the protein synthesis machine, the sensors have the ability to detect this and trigger other internal mechanisms that can compensate and correct mistakes in order to return the cell to a state of homeostasis, or in the case of the cell’s protein system maintain the cells “proteostasis”. But as with many systems in the body, there is a limit to what those systems can compensate for, so if things go beyond its buffering capability then the cells will instead initiate their “self-destruct” mechanism, called “apoptosis” or “programmed cell death”.

Those of you who have been following the health content on thepineapple will probably see where I am going with this, because the idea of homeostasis is a recurring one and the red line that all of the medical cannabis articles have in common. So in this particular case, the authors discovered that CBD and 7-OH-CBD strongly activates a membrane bound RNA splicing enzyme called IRE1α. This enzyme is a critical component of the cell’s “unfolded protein response” which, as the name suggests, monitors how many unfolded proteins accumulate in the cell. As previously mentioned, this is one of those sensor systems that triggers the cell’s stress response when proteostasis is running out of whack. So when the virus infects a cell that is currently undergoing a stress response, then the virus' ability to replicate is impaired, as the cell’s protein machine is essentially in a sort of “homeostasis maintenance mode”. But this is not the only thing CBD appears to affect. Using expression assays the authors discovered that CBD also alters the cell’s cytokine expression profile. Cytokines, are signaling molecules that cells, especially cells of the immune system use to communicate with each other. As you remember from part 1 of this COVID-19 series. One of the big COVID-19 complications is a condition called “cytokine storm”, where infected cells release many conflicting cytokine signals that interfere with the immune response and cause massive inflammation in the tissue. Here CBD was able to almost entirely negate virus induced over-expression of cytokines in cell culture. Not only that but the cytokine expression was slanted towards interferon pathways. The virus usually suppresses interferon signaling pathways because those pathways are a critical component of the immune system’s antiviral (Th1) response and also activate RNA degradation systems within cells. You can imagine that if you are a single-stranded RNA virus, then you are in trouble when a cell you infected doubles-down on making RNA degrading enzymes.  

In a nutshell, this paper shows that CBD inhibits viral replication by triggering the host cell’s protein synthesis stress response as well as innate antiviral interferon pathways. But what about the future ? Can we use this as a treatment ? Well, that is a good question and the authors provided us with some data that suggests we might. 

Firstly, in addition to their in vitro cell culture data the research group also provided us with some preclinical animal data. This is exciting because unforeseen interactions within the whole animal often invalidate in vitro data. But in this case mice injected with escalating doses of 20 mg/kg or 80 mg/kg CBD showed a reduction of viral titers in a dose dependent way. Meaning, consistent with their in vitro data the virus was replicating at a lesser rate in mice pretreated with CBD. Secondly, oral solutions of CBD (100 mg/ml) have already been FDA approved for treatment of seizures in epilepsy patients. This is good news, because it means the step from bench to bedside is significantly shorter if we want to use CBD to treat COVID patients. But it also means that there are already a lot of patient records from people taking oral solutions of CBD right now. So the authors cross-referenced records of patients from the National COVID Cohort Collaborative (N3C) database to look for patients with histories of seizures that were also treated with CBD100. Statistical analysis of the data suggests that treatment with CBD100 lowers the risk of a COVID-19 infection by about 10-fold. This supports the idea that oral CBD solutions might have protective properties that match what the authors discovered in their experiments. Now, to be clear this is far from conclusive.  Especially, since another previous gold standard clinical trial (Crippa et al. 2021) could not corroborate these observations. The trial didn’t make a splash on social media, but was excellently designed. So does that mean CBD doesn’t work ? It means we need to compare those results carefully and design experiments to clarify. Animal models are only a stepping stone towards human application. The biological differences between humans and mice/rats often lead to opposite results. But the discrepancies between these studies may also simply lie with the mode of administration & dosage differences.
There is an excellent “Letter to the Editors” written by Professor Luis Vitetta (et al.) of The University of Sydney that was published very recently onApr 1, 2022. He goes over the differences between the scientific work we discussed in this article and the Crippa et al. clinical trial. The details go beyond the scope of this article, but his arguments are plausible. Suffice it to say the fact that there are inconsistencies that we need to understand. It goes without saying that what we really need is better access to cannabis and more funding for researchers in the field so that scientists and clinicians can produce more organized clinical trials that hopefully manage to clear things up. 

In the words of the authors

Finally, I am going to leave you with excerpts from the research article in the words of the authors themselves, because those thoughts were clearly aimed at a broader audience in an attempt to avoid sensationalized re-broadcasting of their findings by the mainstream media. So I feel compelled to pass them along :

"This study highlights CBD as a potential preventative agent for early-stage SARS-CoV-2 infection and merits future clinical trials”

“We caution against use of non-medical formulations including edibles, inhalants or topicals as a preventative or treatment therapy at the present time.”

“With proper formulation, quality control and delivery, CBD could be used prophylactically in contrast to recent antiviral drugs. Multiple means of CBD ingestion are possible, including potential for inhalation and nasal delivery. CBD blocks viral replication after entry into cells and, thus, is likely to be effective against viral variants with mutant spike proteins. Unlike drugs such as remdesivir or antiviral antibodies, CBD administration does not require injection in hospital settings. Finally, CBD is associated with only minor side effects.”

"As CBD is widely sold as a preparation in an edible oil, we analyzed flavored commercial hemp oils and found a CBD content of only 0.3% in a representative sample. The purity of CBD and the chemical composition of the materials labeled as CBD are also important, especially in light of our findings suggesting that other cannabinoids such as THC might act to counter CBD antiviral efficacy. This essentially eliminates the feasibility of marijuana serving as an effective source of antiviral CBD, … "


  1. van Breemen, Richard B et al.“Cannabinoids Block Cellular Entry of SARS-CoV-2 and the Emerging Variants.”Journal of natural products vol. 85,1 (2022): 176-184. doi:10.1021/acs.jnatprod.1c00946
  2. Nguyen, Long Chi et al. “Cannabidiol Inhibits SARS-CoV-2 Replication and Promotes the Host Innate Immune Response.” bioRxiv : the preprint server for biology 2021.03.10.432967. 10 Mar. 2021, doi:10.1101/2021.03.10.432967. Preprint.
  3. Crippa, José Alexandre S et al. “Cannabidiol for COVID-19 Patients with Mild to Moderate Symptoms (CANDIDATE Study): A Randomized, Double-Blind, Placebo-Controlled Clinical Trial.” Cannabis and cannabinoid research, 10.1089/can.2021.0093. 7 Oct. 2021, doi:10.1089/can.2021.0093
  4. Vitetta, Luis et al. “Re: "Cannabidiol for COVID-19 Patients with Mild to Moderate Symptoms (CANDIDATE Study): A Randomized, Double-Blind, Placebo-Controlled Clinical Trial" by Crippa et al.” Cannabis and cannabinoid research, 10.1089/can.2022.0034. 1 Apr. 2022, doi:10.1089/can.2022.0034