Pfizer and MSD oral antivirals ‘a significant step forward’, says Dr Griffin

Pharma News: The new oral antiviral treatments, Pfizer’s Paxlovid (nirmatrelvir + ritonavir) and MSD’s Lagevrio (molnupiravir), have been approved by the Therapeutic Goods Administration (TGA) for the treatment of mild to moderate COVID-19 in Australia.

Dr Paul Griffin, Director of Infectious Diseases at Mater Health Services, Associate Professor of Medicine at the University of Queensland, and Medical Director and Principal Investigator at Q-Pharm, Nucleus Network, told Health Industry Hub “It’s great to now have two safe and effective oral options approved for use in Australia in mild-moderate COVID-19 positive patients at high risk of progressing to severe disease.”

In exploring the efficacy differences of these oral therapies, Dr Griffin said “While there may be a tendency to compare efficacy rates, it is important to point out that no head-to-head trials have been conducted to date and that any differences in the reported efficacy rates between the two therapies may possibly be accounted for by differences in other variables including the design and conduct of the trials themselves, the populations studied and their inherent risk and rates of COVID infection at the time, to name a few.

“They have different mechanisms of action, however fundamentally both work by stopping the virus replicating or reproducing. They are both a five day courses in total, with doses given orally twice a day. However, Paxlovid is three pills per dose and Lagevrio is four.

“In terms of differences, perhaps the main one is that Paxlovid has significant drug-drug interactions. This is clearly not a major concern and the component responsible for this, Ritonavir*, has been in use for the treatment of HIV for some time. However, prescribers not familiar with these will have to be educated to be on the lookout for drugs that may pose a problem.”

Dr Griffin added “Given the similarity between them, aside from the drug-drug interaction issue, it is likely that in fact logistical issues such as supply or availability will actually determine who receives which therapy. However, given they are both effective, patients should be happy to receive whichever is available to them first.

“As these therapies are given orally and therefore able to be utilised in the community, their approval is likely to represent a significant step forward in our ability to manage COVID-19 including reducing the chance of high-risk patients needing to go to hospital and progressing to more severe disease.”

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*AbbVie markets Ritonavir in Australia