Atea Pharmaceuticals, Inc. provided an update on the company's clinical development priorities for 2022, including broadening its portfolio to include Phase 2 programs across three severe viral diseases. Atea is planning a global Phase 2 outpatient trial for bemnifosbuvir (AT-527) in COVID-19 that is designed to support anticipated combination trials. The Company is also initiating development of ruzasvir (RZR), a Phase 2-ready, next generation NS5A inhibitor in-licensed from Merck, in combination with bemnifosbuvir as a pan-genotypic regimen for the treatment of hepatitis C (HCV).

In addition, Atea is advancing AT-752 to a Phase 2 proof-of-concept program for the treatment of dengue fever. Building on the positive findings from Phase 2 clinical studies of bemnifosbuvir in high-risk patients with mild or moderate COVID-19, Atea plans to initiate a Phase 2 outpatient study designed to support anticipated clinical trials in combination with a protease inhibitor. This Phase 2 trial is designed to obtain additional safety, tolerability and virology data using a formulation with faster dissolution and absorption to enrich the data set from the previous Phase 2 studies.

This trial is expected to enroll up to 200 high-risk outpatients with mild to moderate COVID-19. The Company expects to report topline data from this Phase 2 study in late 2022. The Phase 2 outpatient study replaces the Phase 2 study in hospitalized patients which Atea is currently closing out.

In addition to the clinical development of bemnifosbuvir, Atea is initiating preclinical in vitro combination studies of bemnifosbuvir with protease inhibitors to explore antiviral synergy and mitigation of potential viral resistance in connection with the use of protease inhibitors for the treatment of COVID-19. Atea is announcing that it has obtained exclusive worldwide rights to develop, manufacture and commercialize RZR, an oral NS5A inhibitor, through a recently completed license agreement with Merck. Under the terms of the agreement, Atea will pay Merck an upfront payment and Merck is eligible to receive additional payments associated with the achievement of certain development and commercial milestones as well as tiered royalties on product sales.

RZR has demonstrated highly potent antiviral activity in the picomolar range in preclinical studies. Clinical studies of RZR conducted by Merck showed a > 3 log10 viral load decline in HCV-infected patients as monotherapy. RZR has been administered to over 1,250 HCV-infected patients at daily doses of up to 180 mg for up to 24 weeks and has demonstrated a favorable safety profile with no consistent treatment-related changes in laboratory parameters.

RZR's pharmacokinetic (PK) profile supports once-daily dosing. Bemnifosbuvir has been shown to be approximately 10-fold more active than sofosbuvir (SOF) in vitro against a panel of laboratory strains and clinical isolates of HCV genotypes 1–5. In vitro studies demonstrated bemnifosbuvir remained fully active against SOF resistance-associated strains (S282T), with up to 58-fold more potency than SOF. Bemnifosbuvir has been shown to be generally well tolerated in more than 480 subjects (including healthy volunteers and patients with HCV or COVID-19).

Bemnifosbuvir's PK profile supports once-daily dosing for the treatment of HCV. Atea successfully completed the Phase 1 clinical trial of AT-752. In the Phase 1 trial, AT-752 was well tolerated in 64 healthy subjects who were administered either single or multiple doses.

No premature discontinuations due to adverse events or serious adverse events were reported and most adverse events were mild and there were no changes in laboratory parameters. Atea plans to initiate a global Phase 2 proof-of-concept trial and a human challenge study in the US during the first half of 2022. Atea expects to report results from these studies in late 2022.