Atea Pharmaceuticals, a late-stage clinical biopharmaceutical company focused on developing oral antiviral therapies for serious viral diseases, has initiated a first-in-human Phase 1 clinical trial of AT-587, an investigational oral nucleotide analogue being developed for the treatment of Hepatitis E Virus (HEV) infection.

The randomised, double-blind, placebo-controlled, sequential dose-escalation study will assess the safety, tolerability and pharmacokinetics (PK) of AT-587 in healthy volunteers. The trial comprises Single Ascending Dose (SAD) and Multiple Ascending Dose (MAD) components, along with an embedded food-effect assessment.

In the first part of the study, participants will receive single ascending doses of AT-587 under fasting conditions, with one cohort also evaluated under fed conditions to determine the impact of food on drug absorption. The second part will evaluate multiple ascending doses administered once or twice daily over seven days, with dose escalation guided by emerging safety and pharmacokinetic data.

AT-587 is being developed to address the lack of approved therapies for hepatitis E, a liver disease that can lead to chronic infection, cirrhosis and liver failure, particularly among immunocompromised patients, including transplant recipients and individuals receiving immunosuppressive therapies.

The company's decision to advance AT-587 into clinical development follows encouraging preclinical findings presented at the EASL Congress 2026. According to Atea, the candidate demonstrated potent antiviral activity against HEV, showing 30- to 150-fold greater in vitro potency than the currently used off-label therapies, sofosbuvir and ribavirin, while exhibiting no observed toxicity in laboratory studies.

Additional preclinical data demonstrated that AT-587 significantly reduced HEV RNA levels in an HEV genotype 3 animal model and retained antiviral activity against clinical resistance variants associated with ribavirin and sofosbuvir. The investigational therapy also showed activity against other RNA viruses, including flaviviruses, rubella and chikungunya.

Commenting on the milestone, Jean-Pierre Sommadossi, PhD, Founder and Chief Executive Officer of Atea Pharmaceuticals, said the initiation of the Phase 1 study represents an important step toward addressing a significant unmet medical need for patients living with chronic HEV, particularly immunocompromised individuals who face an increased risk of progressive liver disease.

Hepatitis E remains an under-recognised global health challenge, with an estimated 20 million acute infections annually. While most infections are self-limiting, chronic disease can occur in immunocompromised patients, highlighting the need for effective antiviral therapies. Atea's initial clinical development programme for AT-587 will focus on treating chronic HEV infection in immunocompromised patients, a population for whom no approved antiviral treatment currently exists.