Potential for significant clinical impact.

Bemnifosbuvir has a unique mechanism of action, with dual targets including chain termination (RdRp) and NiRAN inhibition, which has the potential to create a high barrier to resistance.

A scientist operating an analytical instrument in a laboratory environment.


Bemnifosbuvir addresses the key challenges of COVID-19.

Although vaccines play an important role in improving a patient’s chance of experiencing a milder form of COVID-19, as a result of the continuing ability of SARS-CoV-2 to evade vaccines and monoclonal antibodies combined with the limitations of current antivirals, there remains a continuing need for new, oral antiviral treatment options with improved profiles.

Bemnifosbuvir is an oral, direct-acting antiviral drug candidate that is being evaluated for COVID-19 in the global Phase 3 SUNRISE-3 registrational trial.

Our most advanced product candidate, bemnifosbuvir, is an oral direct-acting antiviral, which is being developed as monotherapy and potential combination therapy for COVID-19. Our COVID-19 strategy for bemnifosbuvir focuses on the highest current unmet medical need. Our goal is to deliver a safe, effective and convenient treatment option for people that remain vulnerable to hospitalization or death.

clinical trial logo for sunrise-3 covid-19 trial atea pharma

Similar to Tamiflu®

Complementary medical intervention to vaccination

Significant advantages vs antibodies

Oral administration has significant advantages:

  • convenient for patients and healthcare workers
  • global reach
  • manufacture
  • scale-up
  • cost
Effective vs. mutations

Highly-conserved target has potential to enable antiviral activity in the presence of multiple variants

anticipated to be effective again st future coronaviruses

Antiviral activity against potential future coronaviruses beyond SARS-CoV-2 anticipated

About the Bemnifosbuvir Phase 3 SUNRISE-3 Trial

SUNRISE-3 is a randomized, double-blind, placebo-controlled, global Phase 3 trial is evaluating bemnifosbuvir or placebo administered concurrently with locally available standard of care (SOC). The study is designed to enroll at least 1,500 high-risk, non-hospitalized patients with mild or moderate COVID-19, with a global footprint of approximately 300 clinical trial sites in the United States, Europe, Japan and rest of the world. Patients will be randomized 1:1 to receive either bemnifosbuvir 550 mg twice-daily (BID) plus locally available SOC or placebo BID plus locally available SOC for five days.

This trial will be comprised of two populations derived from the type of SOC received. First, a “supportive care population” (the patient does not qualify for an authorized oral antiviral treatment or is in a region where oral antivirals are not locally available) which will assess bemnifosbuvir given as monotherapy. Second, a “combination antiviral population” which will assess combination therapy, being bemnifosbuvir plus SOC, if the SOC includes treatment with other COVID-19 antivirals.

The primary endpoint of SUNRISE-3, evaluating bemnifosbuvir as monotherapy, is all-cause hospitalization or death through Day 29 in the supportive care population of at least 1,300 patients. Secondary endpoints in the supportive care and combination antiviral populations include: COVID-19 complications, medically attended visits, symptom rebound / relapse and viral load rebound. Hospitalization and death have been the endpoints highly preferred by regulatory agencies, including the U.S. Food and Drug Administration.

The patient population will consist of those at high risk for disease progression, including patients ≥ 80 years old, patients ≥ 65 years old with at least one major risk factor, and immunocompromised patients ≥ 18 years old, all regardless of COVID-19 vaccination status.

Learn More About SUNRISE-3

Topline Efficacy Results from Phase 3 MORNINGSKY Trial

In a topline analysis of data from the MORNINGSKY trial, which was closed out early, the primary endpoint, time to symptom alleviation, was not achieved. However, a 71% reduction in hospitalization (2.9% versus 10%) was observed (p=0.047, unadjusted, exploratory) in the bemnifosbuvir arm (n=137) versus placebo (n=70). There were no deaths in the trial. Hospitalization and death are study endpoints have been preferred by the U.S. Food and Drug Administration and other regulatory authorities.

The MORNINGSKY trial enrolled a broad patient population of whom approximately 50% were high risk and 50% were standard risk; 28% of patients were vaccinated; and 56% were seropositive at baseline. Consistent with previous studies, bemnifosbuvir 550 mg twice-daily (BID) was generally safe and well tolerated. There were no drug-related serious adverse events. Adverse events leading to treatment discontinuation were 3% for bemnifosbuvir versus 7% for placebo and there were no gastrointestinal-related events leading to treatment discontinuation.

  • Risk of hospitalization was 71% lower for bemnifosbuvir vs. placebo

  • No deaths were observed in study

In Vitro Results Against COVID-19 Variants

AT-511, the free base of bemnifosbuvir, has been shown to be a potent inhibitor of SARS-CoV-2 in vitro. New results demonstrated that AT-511 retained potent antiviral activity against the SARS-CoV-2 Omicron subvariants BA.4 and BA.5. AT-511 has previously demonstrated in vitro potent antiviral activity against other variants of concern and/or of interest, including Alpha, Beta, Gamma, Epsilon, Delta and Omicron subvariants BA.1 and BA.2.