Paxlovid misses endpoint in Phase II/III trial for post-exposure prophylactic use

Shares of Pfizer (NYSE: PFE) closed down 2.8% at $49.07 on Friday, after the US pharma giant released disappointing trial results on its antiviral treatment for COVID-19 patients in a prophylactic setting, dipping a further point to $4.50 pre-market today.

The fall came as Pfizer shared top-line results from the Phase II/III EPIC-PEP (Evaluation of Protease Inhibition for COVID-19 in Post-Exposure Prophylaxis) study evaluating Paxlovid (nirmatrelvir [PF-07321332] tablets and ritonavir tablets) for post-exposure prophylactic use. In this trial, compared to placebo, Pfizer observed risk reductions of 32% and 37% in adults who received Paxlovid for five and 10 days, respectively, to prevent infection. These results, however, were not statistically significant and, as such, the primary endpoint of reducing the risk of confirmed and symptomatic COVID-19 infection in adults who had been exposed to the virus through a household contact was not met.

Available safety data for Paxlovid has been generally consistent in more than 3,500 Paxlovid-treated participants across the EPIC-HR, EPIC-SR and EPIC-PEP studies, as well as in reported post-market safety experience. In EPIC-PEP, this safety profile remained generally consistent when Paxlovid was used for either five or ten days. Analyses of all secondary endpoints and sub-groups are ongoing, and results will be included in the publication or presentation of the final study results.