Pfizer Launched Phase 3 Trial for Ibuzatrelvir, New Oral Antiviral for COVID-19 Treatment

Pfizer has initiated a Phase 3 clinical trial to evaluate the safety and efficacy of ibuzatrelvir, a new oral antiviral treatment for COVID-19. This study aims to determine whether ibuzatrelvir can effectively treat high-risk patients who are not hospitalized but at risk of severe disease progression.

The trial, titled “An Interventional Efficacy and Safety, Phase 3, Double-Blind, 2-Arm Study to Investigate Orally Administered Ibuzatrelvir Compared with Placebo in Non-Hospitalized Symptomatic Adult and Adolescent Participants with COVID-19 Who Are at High Risk of Progressing to Severe Illness” (ClinicalTrials.gov ID NCT06679140), will provide important data on the potential of ibuzatrelvir as an alternative to current COVID-19 treatments.

Unlike PAXLOVID (nirmatrelvir-ritonavir), the current standard treatment, ibuzatrelvir is designed to be taken alone. This could reduce the risk of drug-drug interactions associated with ritonavir and address the taste disturbances reported by some patients taking PAXLOVID.

In an email interview with Charlotte Allerton, head of discovery and early development at Pfizer, we discussed how ibuzatrelvir differs from PAXLOVID regarding drug interactions and taste disturbance. She explained, "PAXLOVID is a co-packaged combination of nirmatrelvir and ritonavir. Nirmatrelvir is designed to inhibit viral replication by targeting the SARS-CoV-2 main protease. The low dose of ritonavir is co-administered to slow the metabolism of nirmatrelvir, ensuring it remains active in the body for a longer time at higher concentrations."

She continued, “Ibuzatrelvir is a second-generation investigational treatment that has the potential to treat COVID-19 as a single oral agent. This could reduce the risk of drug-drug interactions associated with ritonavir and eliminate the taste disturbance linked to PAXLOVID. Furthermore, data from a pharmacokinetic study suggest that ibuzatrelvir may also mitigate interactions with drugs metabolized by CYP3A4 enzymes.”

Study Design and Objectives

The Phase 3 trial will enroll adults and adolescents diagnosed with COVID-19 who are not hospitalized. Participants will be randomly assigned to receive either ibuzatrelvir or a placebo for five days. The primary endpoint of the study is to assess the proportion of participants who experience COVID-19-related emergency department visits, hospitalization, or death within 28 days. Secondary endpoints include symptom resolution time, viral load reduction, and the incidence of Long COVID symptoms.

We further discussed the key efficacy and safety endpoints of the trial with Allerton, who noted, “This is a Phase 3, superiority, adaptive, randomized, double-blind, placebo-controlled, multicenter study. It will assess the efficacy, safety, and tolerability of ibuzatrelvir in non-hospitalized, symptomatic adult and adolescent participants who are at high risk of progressing to severe illness.”

She added, “Approximately 2,330 eligible participants will be enrolled. They must have a confirmed SARS-CoV-2 diagnosis within one day prior to randomization, with symptoms onset within five days. Participants will be randomized 1:1 to receive either ibuzatrelvir or placebo twice daily for five days.”

After the five-day treatment phase, participants will be monitored for safety and efficacy endpoints for up to 24 weeks. The primary outcome measure will be the proportion of participants with COVID-19-related emergency department visits, all-cause hospitalization, and all-cause mortality.

Simplified Treatment Option

Ibuzatrelvir is a second-generation antiviral that targets SARS-CoV-2, the virus responsible for COVID-19. By removing the need for ritonavir co-administration, ibuzatrelvir could simplify the treatment regimen, particularly for patients who require extended antiviral treatment or who are sensitive to drug interactions.

Throughout the trial, participants will be monitored for key health outcomes, including symptom resolution, viral load reduction, and adverse events related to the treatment. Secondary endpoints will track the incidence of cardiovascular, renal, and pulmonary complications, as well as signs of Long COVID up to 24 weeks after treatment.

Ongoing Need for COVID-19 Treatments

As COVID-19 continues to evolve, having a range of effective treatment options remains critical. While PAXLOVID remains the primary antiviral treatment for high-risk patients, new therapies like ibuzatrelvir are necessary to meet patients' evolving needs, especially as new variants emerge.

Allerton also discussed how ibuzatrelvir could help address future challenges in COVID-19 treatment. She explained, “Current variants of concern arise due to mutations in the spike protein of the SARS-CoV-2 virus. However, like PAXLOVID, ibuzatrelvir works intracellularly by inhibiting the highly conserved Mpro protease of the SARS-CoV-2 virus to block viral replication. This mechanism suggests that ibuzatrelvir, like PAXLOVID, will remain effective against current variants of concern.”

The Phase 3 trial of ibuzatrelvir is expected to provide valuable insights into how this new treatment compares to existing options in reducing disease severity, preventing hospitalization, and improving patient outcomes. The results from this trial will help shape strategies for managing COVID-19.

Reference

Pfizer. A Study to Learn About a Study Medicine Called Ibuzatrelvir in Adult and Adolescent Patients With COVID-19 Who Are Not Hospitalized But Are at Risk For Severe Disease. Clinicaltrials.gov. November 4, 2024. Accessed December 24, 2024. https://clinicaltrials.gov/study/NCT06679140#study-plan