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 Several recent laboratory studies of cannabidiol, or CBD, have shown
promising results, attracting media attention.
However, many other potential COVID treatments that showed promise
in test tubes, from hydroxychloroquine to various drugs used to
treat cancer and other diseases, ultimately failed to show benefit
for COVID-19 patients once studied in clinical trials.
Marsha Rosner of the University of Chicago led a team that found CBD
appeared to help curb SARS-CoV-2 in infected cells in laboratory
experiments. "Our findings do not say this will work in patients.
Our findings make a strong case for a clinical trial," she said.
Using small doses of highly purified CBD that approximate what
patients receive in an oral drug already approved for severe
epilepsy, Rosner and colleagues found that CBD did not keep the
coronavirus from infecting cells in test tubes.
Rather, it acted soon after the virus entered the cells, blocking it
from making copies of itself in part via effects on the inflammatory
protein interferon. They found similar effects in infected mice,
according to a report in Science Advances
https://www.science.org/doi/10.1126/
sciadv.abi6110.
When they looked at a group of adults with severe epilepsy, the
researchers found those who were taking the approved CBD drug had
lower rates of COVID-19. But a backward look at a small number of
patients does not yield conclusive information. Only randomized
clinical trials can do that, Rosner said.
"I know my message is not something people want to hear," she said.
Small doses of tetrahydrocannabinol (THC) - the marijuana ingredient
that causes the high - cannabidiolic acid (CBDA), cannabidivarin (CBDV),
cannabichromene (CBC), and cannabigerol (CBG) did not keep the virus
out of cells or prevent it from replicating, her team found.
"Not only did THC not work, but combining it with CBD prevented CBD
from working," Rosner said.
NO COVID CURES AT CBD DISPENSARY
A separate team reported recently in the Journal of Natural Products
that high doses of CBG and CBDA do prevent the coronavirus from
breaking into cells.
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 Richard van Breemen from
Oregon State University told Reuters that the
doses his team tested were non-toxic to cells.
It is not clear yet that similarly high doses
would be safe for humans, his team said.
"You want the lowest possible effective dose,"
Rosner said, because of potential side effects
as the drug is filtered through the liver.
The CBD her team tested was more than 98% pure,
while purity in commercial products is far
lower. "People should not run out and get CBD
from their favorite dispensary," she said.
CBD products have become widely available in
many forms and have been touted - often without
proof from clinical trials - as treatments for
pain and other ailments.
Small CBD trials in humans with COVID-19 are
underway.
In one completed study, researchers in Brazil
randomly assigned 105 patients with mild or
moderate COVID-19 to receive CBD or a placebo
for 14 days along with standard care. The CBD
had no apparent effect, according to an October
report in Cannabis and Cannabinoid Research
https://www.liebertpub.com/doi/10.1089/
can.2021.0093.
In a proof-of-concept study at Sheba Medical
Center in Israel, researchers are randomly
assigning patients with mild COVID to receive
CBD or a placebo.
An early-stage trial at Rabin Medical Center,
also in Israel, aims to test the effect of CBD
in severely or critically ill patients. However,
study leader Dr. Moshe Yeshurun told Reuters
that accruing participants has been difficult
because the current Omicron-driven coronavirus
wave "consists mostly of patients with mild to
moderate disease."
Rosner's team is exploring the possibility of a
clinical trial that would likely focus on
asymptomatic or mild cases of COVID. Meanwhile,
she is concerned that media reports overstating
the potential of cannabinoids will lead people
to self-medicate with CBD, stop using masks and
avoid vaccines.
"We would love to be able to say specifically"
that a certain dose of cannabinoids is helpful,
she said, but at this point, "vaccine-induced
antibodies and antibody drugs are much more
effective at blocking infection."
(Reporting by Nancy Lapid; Editing by Michele
Gershberg and Bill Berkrot)
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