The numbers look promising: if high-risk patients are treated three days after their symptoms started, Paxlovid can reduce the risk of hospitalization or a fatal outcome by almost 90 percent compared to a placebo. And even if a patient doesn’t get the drug until five days after the onset of symptoms, their chances are not that much lower. The pharmaceutical company Pfizer reports in a press release.
Paxlovid gives reason for hope
For the infectious disease specialist Philipp Schommers from the Cologne University Hospital, this is clearly a reason for hope: “Unfortunately, we have not yet seen the original study data, only through the Pfizer press release. But if they turn out to be true, and we have this drug available in sufficient quantities in Germany, there could be a significant improvement to all previously known drugs, yes. “
In addition to its high level of effectiveness, it is primarily the form of administration that sets Pfizer’s antiviral drug apart from all other drugs that have been used in the clinic so far, says Philipp Schommers:
“The only thing we’ve had to treat early infected people where it has been seen to be effective, at least until Omikron came along, was monoclonal antibodies. And these antibodies could only ever be administered intramuscularly or intravenously – that is, they had to be injected. And most patients could not self-administer it. “
The first corona drug in pill form
Paxlovid, on the other hand, can simply be swallowed in pill form. Twice a day for five days. The doctor may prescribe it as soon as symptoms appear. This increases the likelihood that the drug will be able to stop the virus from spreading in the body in time, so that it does not even develop into a severe course, says the head of virology at Heidelberg University Hospital, Hans-Georg Kräusslich.
“It is not a drug that would be expected to provide a significant benefit to people who are critically ill in the intensive care unit. But it is certainly a drug that, if given early, can have a significant advantage in high-risk patients, i.e. older people or people with previous illnesses. “
Paxlovid prevents severe courses
The antiviral agent in the drug prevents the virus from multiplying in the body. To do this, it blocks a certain component of the pathogen’s molecular machinery: an enzyme that helps to bring the protein molecules of the virus into their final form. A so-called protease. The paxlovid active ingredient is therefore also referred to as a protease inhibitor.
Such protease inhibitors are already being used more frequently in the treatment of viral diseases, says Hans-Georg Kräuslich: “You have to develop it again for each new virus, they don’t work cross-wise, they don’t work against many different viruses. And that has now been achieved accordingly in this active ingredient against SARS-CoV-2. “
The protease inhibitor also works against the omicron variant
Monoclonal antibodies adhere to the spike proteins on the surface of SARS-CoV-2 and thus prevent it from docking on body cells. But because these grappling hooks are littered with mutations in the omicron variant, these defense molecules no longer fit. The omicron protease, on the other hand, only carries a single mutation. And therefore, paxlovid should continue to be highly effective during the omicron wave. In the biochemical experiment at least the active ingredient was able to block the omicron protease, explains Hans-Georg Kräusslich.
“We can therefore assume with a high degree of certainty that the currently circulating Omikron variant can still be effectively inhibited by this active ingredient. The extent to which resistances can then develop there in the future or not can hardly be predicted. “
The EMA is reviewing the approval of paxlovid
The European approval authority EMA is currently testing the drug in the accelerated rolling review process. The results of the clinical studies are made available to the authority as soon as they have been collected – and not only as a complete package at the end of the tests.
“In this respect, the hope is that the time frame for a possible approval will be shorter. It is difficult to predict whether that will be in January or a little later. At the moment, however, it can, if available, be used as emergency medication under the appropriate conditions. “
It is therefore questionable whether it can break a rapidly burning omicron wave. This is how Philipp Schommers from the Cologne University Hospital also sees it: “I believe that ultimately the best means of ending or fighting pandemics is still vaccinations – and now, probably, contact restrictions again soon. But if this drug is available in sufficient quantities, it will probably prevent hospital stays. Whether it can then relieve the health system as a whole depends of course on the level of the incidence. “
And that should increase sharply in the foreseeable future thanks to the Omikron variant.