TGA grants provisional approval to oral COVID-19 treatments

At last, some good news on the COVID front: the Therapeutic Goods Administration (TGA) has provisionally approved the first oral antiviral treatments for COVID-19.

Federal Health Minister Greg Hunt has confirmed the government has acquired 500,000 courses of Pfizer’s Paxlovid, and 300,000 courses of Merck Sharp & Dohme’s Lagevrio (molnupiravir), with the first deliveries of both medicines anticipated to arrive in the country in coming weeks.

While attention has lately focused on booster schedules and the necessity of addressing global vaccine equity, these novel effective treatments are crucial additional tools in our arsenal.

The medications hold the promise of significantly reducing the risk of progression to severe disease, potentially enabling many more cases to be treated as outpatients and easing the pressure on our beleaguered hospitals and medical staff.

“This is such a fantastic advancement and opportunity for effective treatments, designed and tested to specifically target SARS-CoV-2, that can be easily accessed as oral, take-home formulations,” says Associate Professor Jill Carr, laboratory head in microbiology and infectious diseases in the College of Medicine and Public Health at Flinders University.

Both medications work by inhibiting the replication ability of the SARS-CoV-2 virus.

“Molnupiravir targets the machinery that replicates the viral genome, while Paxlovid targets the viral protease that is essential for infectivity and is formulated with ritonavir, which ‘boosts’ the therapeutic levels of the active drug,” explains Carr.

Associate Professor Andrew Rowland, Beat Cancer Project mid-career research fellow in clinical pharmacology at Flinders University, adds that Paxlovid targets a unique process in COVID replication that is unrelated to spike proteins, which are the target of most other COVID treatments and vaccines.

“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,” he says.

Both are designed to be taken every 12 hours over five days from the onset of symptoms, before viral loads reach levels associated with severe disease.

Hunt has flagged that these treatments won’t be available for everyone who contracts COVID-19, being reserved instead for vulnerable patients most at risk of severe disease, including the elderly and those in aged care.

While the arrival of these new treatments offers a significant opportunity to reduce the impact of COVID-19, the medical regulator has stressed that they do not represent a substitute for vaccines.

In a recent interview with Cosmos, Monash University Malaysia molecular virologist Dr Vinod Balasubramaniam reiterated this point.

“Vaccines offer long-term, robust and durable protection via immunological memory against COVID-19 before the real infection itself, training our body to be ever ready to fight this disease – something an antiviral pill could not provide,” he said. 

“Vaccination should remain the long-term priority for governments worldwide in the fight against this pandemic. But antiviral strategies should be added as part of our portfolio to fight COVID-19 and future pandemics to give a synergistic effect that will have a better outcome.”

There is additional good news from the TGA on vaccines: Australia will soon offer four different vaccines, with the regulator also provisionally approving the Novavax jab.

Hunt is hopeful this latest vaccine – the only protein-based jab available – will help to encourage the reluctant 5% of Australians aged 16 and over who remain unvaccinated to step up for their first shot.

Novavax has only applied for its vaccine to be used for primary vaccination courses, meaning it will need to apply for further TGA approval before being use for booster shots.