Tune Therapeutics Presents Positive Phase 1b/2a Proof of Concept Data on TUNE-401: a First-in-Class Epigenetic Silencer for Patients with Hepatitis B at EASL 2026 – FirstWord Pharma

Tune Therapeutics has released positive proof-of-concept data from its Phase 1b/2a clinical trial of TUNE-401, a first-in-class epigenetic silencer designed to treat patients with chronic hepatitis B. The findings were presented on May 30, 2026, at the European Association for the Study of the Liver (EASL) 2026 congress, marking a significant technical milestone in the effort to achieve a functional cure for the virus.

TUNE-401 targets the persistent reservoir of the hepatitis B virus (HBV) by utilizing epigenetic silencing. Unlike traditional gene-editing technologies that physically cut or alter the DNA sequence, epigenetic silencers modify the chemical markers on the DNA to turn off specific genes without changing the underlying genetic code. In the case of HBV, the therapy aims to silence the covalently closed circular DNA (cccDNA), which is the stable form of the virus that persists in the nuclei of infected liver cells.

The Technical Challenge of HBV cccDNA

The primary obstacle to curing hepatitis B is the stability of cccDNA. Current standard-of-care treatments, such as nucleoside analogs, are effective at suppressing viral replication and reducing the risk of liver cirrhosis and hepatocellular carcinoma, but they rarely result in a complete cure. This is because they do not eliminate the cccDNA reservoir, meaning the virus can reactivate if treatment is discontinued.

TUNE-401 addresses this by employing a programmable platform that directs silencing machinery to the HBV genome. By inducing a repressed chromatin state, the therapy prevents the virus from transcribing its genes, effectively muting the viral activity within the hepatocyte. This approach seeks to reduce the production of viral proteins, such as the surface antigen (HBsAg), which are known to exhaust the patient’s immune response and prevent the body from clearing the infection naturally.

Phase 1b/2a Trial Outcomes

The Phase 1b/2a trial was designed to evaluate the safety, tolerability, and preliminary efficacy of TUNE-401. According to the data presented at EASL 2026, the therapy demonstrated a positive proof-of-concept, indicating that the epigenetic silencing mechanism is active in humans and capable of reducing viral markers.

The trial’s focus on proof-of-concept is critical because it validates the delivery system and the precision of the epigenetic targeting. The data suggest that TUNE-401 can achieve a reduction in viral load and antigen levels, which are the primary biomarkers used to determine if a patient is moving toward a functional cure. A functional cure is defined as the loss of HBsAg from the blood, accompanied by a durable suppression of HBV DNA, regardless of whether the cccDNA is entirely eradicated from every cell.

Industry Context and the Path to Functional Cure

The development of TUNE-401 places Tune Therapeutics within a competitive landscape of companies pursuing non-traditional HBV therapies. Other modalities being explored include RNA interference (RNAi) and antisense oligonucleotides (ASOs), both of which target viral transcripts. However, epigenetic silencing is distinct because it acts further upstream at the DNA level, potentially offering a more durable effect by locking the viral genome in an inactive state.

The broader biotech industry views the ability to silence cccDNA as a prerequisite for the next generation of HBV medicine. If TUNE-401 can maintain long-term silencing, it could reduce the necessity for lifelong medication, which is the current reality for millions of patients worldwide. The technical success of this phase of the trial provides a framework for dosing and safety that will inform subsequent, larger-scale efficacy studies.

Following the presentation of these results, the next steps for TUNE-401 will likely involve expanding the patient cohort to determine the optimal dose for maximizing HBsAg loss and evaluating the long-term durability of the silencing effect. The company’s progress indicates a shift toward precision epigenetic medicine, moving the field closer to a therapeutic reality where chronic viral infections can be managed or cured through genomic regulation rather than continuous chemical suppression.