Study: 15-Day Paxlovid Regimen Ineffective for Long COVID

A Phase II study from Stanford Medicine has revealed that Pfizer's oral antiviral Paxlovid (nirmatrelvir/ritonavir) does not significantly improve symptoms in patients suffering from long COVID. This research was published in JAMA Internal Medicine on Friday.

The trial's findings indicated that after 10 weeks, Paxlovid did not significantly reduce the severity of the six primary symptoms of long COVID compared to placebo and ritonavir. These primary symptoms include fatigue, brain fog, shortness of breath, body aches, gastrointestinal issues, and cardiovascular symptoms.

Moreover, Paxlovid failed to show a significant difference from placebo in addressing fatigue, shortness of breath, physical function, and cognitive function. Patients recorded similar scores on the Patient Global Impression of Severity and Patient Global Impression of Change inventories, which are patient-reported measures used to evaluate treatment effects.

This Pfizer-funded Phase II STOP-PASC trial is noted as the first investigation of Paxlovid for long COVID by Stanford Medicine. Despite the absence of significant efficacy indicators, the Paxlovid regimen, which involved twice-daily treatment over 15 days, was deemed safe. Adverse events were generally low-grade and comparable between the treatment and placebo groups.

Upinder Singh, the study's senior author and co-principal investigator, commented that the absence of a clinical response in this study does not preclude the possibility of discovering clinical benefits in the future. Singh emphasized that the study did not fully resolve all uncertainties surrounding the treatment of long COVID. He raised questions such as whether patients with symptoms persisting for a shorter period should have been tested or if a longer treatment duration was necessary. Additionally, Singh pondered whether the study targeted the right patient population or if only certain symptoms might respond to antiviral treatment.

Despite these uncertainties, Singh and the team confirmed the safety of a prolonged Paxlovid regimen, which in this study was administered for three times the duration recommended for acute COVID-19. This finding could be significant for patients needing extended antiviral treatment, particularly those who are immunocompromised.

Long COVID, scientifically referred to as the post-acute sequelae of SARS-CoV-2 infection, encompasses a wide range of symptoms that manifest at least three months after the initial COVID-19 infection. Approximately 10% to 20% of individuals who had COVID-19 develop long COVID. In the United States, this translates to tens of millions of people, as reported by Stanford Medicine.

However, defining long COVID remains challenging, with over 200 potential symptoms associated with the condition. The underlying mechanisms of the disease are also diverse and complex, complicating drug development efforts. Currently, there are no FDA-approved treatments specifically for long COVID.

The study's findings contribute to the ongoing research and understanding of long COVID and the potential role of antiviral treatments. While Paxlovid did not demonstrate significant efficacy in this trial, the established safety profile for extended use may have implications for future treatment strategies, particularly for those who require prolonged antiviral exposure.

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