The Medicines and Healthcare products Regulatory Agency (MHRA) will look at new data requested by US authorities on “COVID-19 rebound” in patients treated with the antiviral treatment Paxlovid (nirmatrelvir and ritonavir; Pfizer).
In a statement to The Pharmaceutical Journal, a spokesperson for the MHRA said that the regulator may also consider data on rebound infections from the PANORAMIC trial, when the data are available.
The Pharmaceutical Journal revealed in May 2022 that the MHRA had received a “small number” of Yellow Card reports of people who have tested positive for COVID-19 after completing treatment with Paxlovid.
After these reports — and others in the United States — the US Food and Drug Administration (FDA) has demanded new trials. In a letter dated 5 August 2022, the FDA asked manufacturer Pfizer to conduct a double-blind, randomised, controlled trial in patients with COVID-19 rebound, following a first treatment course of Paxlovid, to see the effects of a second five-day treatment course.
It said Pfizer must make topline results available by 30 September 2023 and the trial is a condition of the continuing emergency use authorisation of the drug.
The FDA also requested a trial to evaluate different durations of treatment in immunocompromised people with mild-to-moderate COVID-19, with the same deadline.
The MHRA issued a conditional marketing authorisation for Paxlovid in December 2021 in England, Scotland and Wales, and a Regulation 174 authorisation in Northern Ireland, to ensure supply across the UK. Under the authorisation, a five-day course of Paxlovid is indicated for treatment of COVID-19 in adults who do not require supplemental oxygen and who are at risk of progression to severe COVID-19.
In the MHRA’s statement, the spokesperson said: “We will be looking at all available data, including data from the FDA-requested trial. In the UK, there is an ongoing trial, PANORAMIC, which may generate data on rebound infections and we will also consider this when data become available.
“We will seek independent, expert advice from the Commission on Human Medicines if we conclude that any further action is needed.”
In May 2022, Albert Bourla, the chief executive of Pfizer, said in an interview that patients who experience COVID-19 viral rebound can simply take another course of Paxlovid.
Recurrence of COVID-19 after recovery may be higher than expected. One unpublished study, carried out in March to May 2022, found that 4% of untreated people had a recurrence of viral COVID-19 after recovery, compared with 27% of people treated with Paxlovid. However, this was not a randomised controlled trial and there were major differences between the treated and untreated groups — notably that untreated people were much younger.