- Nitric oxide is a colorless, tasteless and short-acting gas which widens blood vessels in the lungs when inhaled.
- It was in the 90s that nitric oxide also played a central role in the development of the erectile dysfunction drug Viagra.
- To date, there are no approved treatments for the coronavirus.
Medical researchers are testing whether inhaled nitric oxide could help treat patients with the coronavirus.
A range of studies and clinical trials underway at Massachusetts General Hospital aims to find out if the familiar treatment can help save those who are sick, prevent people from being intubated and potentially even keep health care workers infection-free.
As of Friday, more than 3.25 million people had contracted Covid-19 worldwide, with 233,439 deaths, according to data compiled by Johns Hopkins University.
The U.S. alone is grappling with roughly one-third of all reported coronavirus cases, having surpassed the milestone of 1 million infections earlier this week.
The outbreak of the virus, which first emerged in late 2019, has meant countries around the world have effectively had to shut down. Confinement measures have been implemented in 187 countries or territories in an effort to try to slow the spread of the pandemic.
There are no known vaccines or specific antiviral medicines against Covid-19. But, scientists across the globe are trying to fast-track work on effective treatment. U.S. health officials say developing a vaccine will take at least 12 to 18 months.
What is nitric oxide?
Nitric oxide is a colorless, tasteless and short-acting gas which widens blood vessels in the lungs when inhaled. It is frequently used as the first line of treatment for oxygen-deprived premature babies.
The compound simply consists of one-part nitrogen and one-part oxygen — the two most common gases in the atmosphere.
In 1998, pharmacologist Louis Ignarro shared the Nobel Prize for uncovering nitric oxide as a signaling molecule in the cardiovascular system. It was subsequently approved by the U.S. Food and Drug Administration in 1999 and physicians have used the compound for a wide range of medical conditions ever since.
It was in the 90s that nitric oxide also played a central role in the development of the erectile dysfunction drug Viagra, as the blue pill's main ingredient, sildenafil, makes the relaxing effect of the nitric oxide in the body more potent and increases blood flow.
How does it work?
Stuart Harris, an attending physician at Massachusetts General Hospital, told CNBC via telephone that four studies were underway to explore whether inhaled nitric oxide could be harnessed to treat the coronavirus.
In each of the studies, Harris said the hospital was looking at a few different outcomes, including trying to keep people alive in the intensive care unit, working to prevent people from being intubated and seeking to ensure health care workers do not get the disease.
"The lungs you can think of as a marketplace bringing together air and blood," Harris said. The way that Covid-19 is "most likely" to be fatal is it impairs that marketplace and prevents the blood from providing the body with enough oxygen.
"Nitric oxide is a smooth muscle relaxer. So, the typically very low-pressure blood vessels in the lungs, it relaxes (them) and it helps get blood to places that the nitric oxide is going to. Essentially, it produces an efficient marketplace so the lungs can do their job," he explained.
Preliminary data has suggested that inhaled nitric oxide could have a virus-killing effect on the coronavirus, Massachusetts General Hospital says in an online statement. It is due to the genomic similarities between Covid-19 and those that caused the SARS and MERS outbreaks. Studies during the SARS outbreak in 2004 to 2005 demonstrated that nitric oxide was effective in killing that virus.
To be sure, the effectiveness of nitric oxide in treating the new coronavirus has not been studied before.
The FDA has been engaged in ongoing discussions with Gilead to make remdesivir available to Covid-19 patients after early results of a drug trial had shown improvement among patients.
But, to date, there are no approved treatments for the coronavirus.
When asked whether he believed nitric oxide studies could lead to an effective coronavirus treatment, Harris replied: "We don't know and that's why we do studies. But, it is something that definitely bears looking closely at and if we look at the panoply of other studies being done, frankly, I put more money on the mechanisms we are proposing than some of the others."
Separately, researchers cut short a study testing anti-malaria drug chloroquine as a potential Covid-19 treatment last week.
The drug gained widespread international attention after two small studies published in France last month found the coronavirus infection cleared a lot faster for patients taking it when compared to a control group.
However, citing a high risk of death, scientists have now scrapped the trials, warning it should prompt some degree of skepticism from the public toward enthusiastic claims of the drug. President Donald Trump had touted chloroquine as a potential "game changer" in the fight against the virus.
— CNBC's Berkeley Lovelace Jr. contributed to this report.