Australia’s drugs regulator has for the first time approved oral treatments for Covid-19 which should help address supply shortages of other treatments.
The approval applies to two drugs – Paxlovid and Lagevrio. They have been “provisionally” approved, which means they can be administered by health professionals in limited circumstances but the manufacturers must submit further data as the drugs are used more widely.
The director of infectious diseases at Mater Health Services, associate professor Paul Griffin, said on Thursday: “We’ve got great safe and effective vaccines. We’ve got intravenously administered antivirals and monoclonal antibodies, which have certainly helped us. But what we’ve been missing right now is an oral therapy that changes the course of the Covid illness.”
How do the drugs work?
They both stop the virus from reproducing readily in cells of the body – and they do that in slightly different ways.
Lagevrio causes errors during the viral replication process “to the point where the virus is no longer viable and doesn’t survive that process,” Griffin said. Paxlovid blocks a critical enzyme – a protease – that the virus needs to replicate itself.
Either medicine should ideally be administered as soon as possible after diagnosis and within five days of the onset of symptoms. The medicines are taken twice a day for five days. In clinical trials, both drugs were very effective in reducing rates of death.
Who will benefit?
The treatments can only be given to adults with Covid-19 who do not yet require oxygen but who are at increased risk of progression to hospitalisation or death – for example, the elderly or immunocompromised. This is also the case for other treatments available.
But until now, those treatments had to be delivered through intravenous infusion in a hospital or other medical setting, or through consecutive intramuscular injections. There have also been supply shortages of some of these treatments.
“The oral therapies are going to be easier to use,” Griffin said.
“They’re going to be easier to get to people earlier, which is really important with all these kinds of interventions. How quickly we give them can in many ways determine how well they work.
“This also reduces the burden on the healthcare system as these oral therapies can be very much community focused, rather than requiring a hospital bed and resources to administer.”
It will have a clear benefit for people in aged care, who won’t have to be transferred to hospital for intravenous treatment.
Resistance to virus mutations
A research fellow in clinical pharmacology at Flinders University, associate professor Andrew Rowland, said most existing Covid-19 treatments and vaccines targeted the virus’s spike protein.
“Paxlovid is an important new treatment for Covid patients as it targets a unique process in Covid replication that is not related to the spike protein,” he said. “This means that Paxlovid is less likely to lose efficacy due to mutations in the spike protein, which to date have been associated with the major variants including Delta and Omicron”.
When will they be used?
The Australian government has secured 500,000 treatment courses of Paxlovid and 300,000 courses of Lagevrio for supply during 2022, with the first deliveries due in the coming weeks.
Are they a vaccine alternative?
No Covid treatments are an alternative to vaccination. Not only are treatments reserved for the most at-risk cases but there may also continue to be supply shortages of treatments throughout the pandemic. Importantly, treatments only work for a short period of time, whereas vaccines provide longer-lasting protection.
“Vaccines work so tremendously well at stopping people progressing to severe disease but also preventing people from getting the infection and passing it on,” Griffin said. “These drug therapies certainly won’t do all those things. They’re an added tool to vaccination that will make a huge difference to the most vulnerable.”
Rowland added that the drugs were also expensive.
“Currently a disproportionate number of patients being treated for Covid with monoclonal antibodies in the community, being admitted to hospital, and requiring ICU beds are unvaccinated,” he said.
“The expense of supplying Paxlovid to these Australians will place a further burden on an already overstretched healthcare system. We can afford to vaccinate 32 children for the cost of treating one person with Paxlovid.”