An experimental cancer drug derived from a poisonous plant could stop Covid-19 in its tracks, researchers believe.
Nottingham University academics claim thapsigargin should be effective against the coronavirus behind the pandemic and others that cause common colds.
The drug, derived from the ‘deadly carrot’ thapsia plant — which is deadly to cattle and sheep and found in the western Mediterranean, is being trialled against prostate cancer.
But researchers testing the treatment on animals have found it may be able to stop infection with the SARS-CoV-2 coronavirus, which causes Covid.
Experimental cancer drug thapsigargin derived from derived from the ‘deadly carrot’ thapsia plant (pictured) could stop Covid-19 in its tracks, researchers believe
Trials also found the drug — which humans will be able to take as a pill if proven to work — to be effective against coronaviruses that cause the common cold, as well as respiratory syncytial virus (RSV) and influenza.
Researchers believe the drug’s effectiveness against a range of respiratory viruses could make it particularly useful in the coronavirus pandemic.
Rather than targeting coronavirus specifically, the antiviral could be used to inhibit the development of a range of viruses that trigger similar symptoms.
What is ‘the ‘deadly carrot’ thapsia plant and how has it been used in medicine?
The ‘deadly carrot’ thapsia garganica in bloom
Thapsia garganica is a flowering plant found in the western Mediterranean coasts.
The plant has long been used in traditional medicine, including as a pain reliever in Algeria.
But it gained its common name, the deadly carrot, from its toxicity to sheep and cattle in ancient Greece
Thapsigargin is a chemical compound isolated from the plant, which has been used in cancer research.
Johns Hopkins University oncologist Samuel Denmeade spent 15 years engineering the compound from the plant.
In cancer research, the drug was found to be effective by passing through cell membranes and shutting down calcium pumps.
Trial have found it to be safe in humans at much higher dose levels than required for its antivral use.
To induce an antiviral state, a much smaller dose of the drug is needed.
This broad applicability could also make the drug effective against future ‘Disease X’ pandemics, according to researchers.
Professor Kin-Chow Chang, one of the lead researchers, admitted that more testing is ‘clearly needed’ — no evidence exists that it will work on humans.
But he said ‘findings strongly indicate thapsigargin and its derivatives are promising antiviral treatments against Covid and influenza’.
The antiviral was found to be effective at blocking symptoms when used before or during active infection in petri dish tests and on mice.
It costs around £76 ($104) per 1mg for use in experimental research currently but its cost would reduce drastically if it went into full production. Flu antivirals can require between 200mg to 800mg per dose.
The compound could be readily made in bulk in laboratories, rather than harvesting directly from the plant, and stored without deep freezing requirements.
No antivirals have yet been approved for coronavirus and only a handful of drugs have been proven to cut the risk of dying in critically-ill patients.
Antivirals licensed for flu target a part of the virus to stop or slow down its ability to make copies of itself inside infected cells.
But thapsigargin works by triggering a range of host cellular responses rather than targeting the virus itself.
In other words, the drug makes cells better able to fight off invading viruses using the immune system’s natural ability.
These responses disrupt the reproduction cycle of the virus at several places at the same time, preventing the virus from replicating and taking hold.
This makes the drug particularly valuable against new strains because mutations in one part of the virus’ reproduction cycle should not reduce its effectiveness.
Lab tests on cells showed the drug stopped a virus from making new copies of itself within just 30 minutes — and it did not wear off for two days.
Professor Chang said: ‘Whilst we are still at the early stages of research into this antiviral and its impact on how viruses such as Covid-19 can be treated, these findings are hugely significant.
‘The current pandemic highlights the need for effective antivirals to treat active infections, as well as vaccines, to prevent the infection.
‘Given that future pandemics are likely to be of animal origin, where animal to human (zoonotic) and reverse zoonotic (human to animal) spread take place, a new generation of antivirals, such as thapsigargin, could play a key role in the control and treatment of important viral infections in both humans and animals.’
The study was a collaborative project by the University of Nottingham (pictured), the Animal and Plant Health Agency (APHA), China Agricultural University and the Pirbright Institute
Professor Mark Woolhouse last week suggested another pandemic-causing ‘Disease X’ could be around the corner – and it is a matter of ‘when, not if’.
The expert in infectious disease epidemiology at the University of Edinburgh said that pandemic flu is at the top of the list for outbreaks to be concerned about, but he added that there is a whole range of other viruses to be aware of.
Mr Woolhouse revealed he and other colleagues got the World Health Organisation to add Disease X to its list of priority diseases four years ago.
He said: ‘We thought that the next emerging pandemic might be a virus that we don’t even know about yet – quite frankly we thought it was the most likely scenario.’