Eton Pharmaceuticals Announces Initiation of Clinical Study for Product Candidate ET-700

Eton Initiates Pilot Study for ET-700 in Wilson Disease

Eton Pharmaceuticals has initiated a pilot clinical study for ET-700, an extended-release zinc acetate formulation under development for Wilson disease. The study, conducted at Aarhus University Hospital, involves 36 healthy volunteers and compares ET-700 (75 mg twice daily) against GALZIN (50 mg three times daily) and a placebo. It utilizes 64Cu PET imaging to assess intestinal copper absorption, with the primary endpoint being the change in mean hepatic 64Cu standard uptake value. Topline results are expected in the second half of 2026, potentially leading to a pivotal study in early 2027. The company projects peak annual sales exceeding $100 million in the U.S. if approved.

• Eton Pharmaceuticals has commenced a pilot clinical study for its proprietary, patent-pending extended-release zinc acetate formulation, ET-700, targeting Wilson disease. This double-blinded, placebo-controlled trial is being conducted by the Department of Hepatology and Gastroenterology at Aarhus University Hospital in Denmark. The study aims to evaluate whether ET-700 can offer a more convenient, simpler dosing approach for this lifelong chronic therapy compared to existing treatments.
• The study design involves 36 healthy volunteers randomly assigned to one of three treatment groups: GALZIN 50 mg three times daily, ET-700 75 mg twice daily plus a placebo once daily, or a placebo three times daily. Intestinal copper absorption will be assessed using positron emission tomography (PET) scans with the radioactive tracer 64CuCl2. The primary endpoint is the change in mean hepatic 64Cu standard uptake value from pre- to post-intervention between the three groups over a four-week treatment period.
• Eton Pharmaceuticals anticipates releasing topline study results in the second half of 2026. Should these results be positive, the company plans to advance to a pivotal clinical study in early 2027. CEO Sean Brynjelsen highlighted ET-700's potential to significantly improve patient convenience and projected that, if approved, the product could achieve peak annual sales exceeding $100 million in the United States market.

Addressing Unmet Needs in Lifelong Wilson Disease Management

Current Wilson disease management faces substantial therapeutic and clinical challenges that impact patient outcomes and quality of care. These limitations span from medication efficacy issues to diagnostic complexities, creating significant unmet needs in lifelong disease management.

• Treatment efficacy and safety limitations - Current treatments, primarily metal chelating agents and antioxidants, demonstrate sub-optimal efficacy, limited blood-brain barrier transport, and systemic side effects, with penicillamine therapy associated with many adverse reactions including worsening of neurologic symptoms

• Poor medication adherence - Despite the critical role of adherence for adequate Wilson disease control, one-third of patients exhibit low adherence, which is a well-known contributor to unfavorable clinical outcomes and is significantly associated with younger age at evaluation, higher ALT, and higher exchangeable copper levels

• Adherence monitoring challenges - Measuring adherence in chronic Wilson disease patients remains challenging as no gold standard method is available, with limited agreement among different assessment methods and only 12% of patients classified as noncompliant by three different methods simultaneously

• Diagnostic delays and misdiagnosis - The diagnosis is frequently overlooked due to nonspecific symptoms and multisystem involvement that may mimic neurologic and psychiatric disorders, with up to two-thirds of Indian cases initially misdiagnosed and mean diagnostic delays of up to 2 years

• Limited evidence base and practice variability - There is a scarcity of randomized and high-quality studies to aid clinicians in management, with significant variability in initial therapies among California and European/Italian providers and differences in diagnosis and management approaches between North American and European society guidelines

• Insufficient exploration of combination therapies - Despite the wide use of combination therapy of chelators and zinc, this approach requires further exploration and evidence generation to optimize treatment protocols

ET-700 Pilot Study: Design to Improve Copper Absorption

The WTX101 phase 2 open-label study enrolled 28 patients aged ≥18 years with Wilson's disease across 11 hospitals in the USA and Europe. Participants were either treatment-naïve or had received no more than 24 months of prior chelator or zinc therapy, with Leipzig scores ≥4 and non-ceruloplasmin copper (NCC) concentrations ≥0.8 μmol/L. The study utilized response-guided individualized dosing, starting at 15-60 mg/day based on baseline NCC concentrations for the first 4-8 weeks, followed by dose adjustments through week 24. The primary endpoint measured change in baseline NCC concentrations corrected for copper in tetrathiomolybdate-copper-albumin complexes at 24 weeks, with treatment success defined as achieving normalized NCC (≤2.3 μmol/L) or ≥25% reduction from baseline.

The randomized, open-label, non-inferiority phase 3 trial comparing TETA4 to penicillamine recruited 53 patients aged 18-75 years with stable Wilson disease from 13 centers across Brazil, Europe, and the USA. Following a 12-week stability assessment period with predefined thresholds for serum NCC (25-150 μg/L), 24-hour urinary copper excretion (100-900 μg/24h), and ALT levels, stable patients were randomized 1:1 to continue penicillamine or switch mg-for-mg to TETA4. The primary endpoint assessed NCC by speciation assay at 24 weeks with a non-inferiority margin of -50 μg/L, estimated using a general linear model adjusted for baseline values, followed by a 24-week extension period.

Additional studies included long-term zinc therapy evaluations spanning up to 10 years in 141 patients, demonstrating median follow-up periods of 4.8 years overall, 6.5 years for presymptomatic patients, and 3.6 years for children. These studies utilized biomarker monitoring including 24-hour urinary copper and plasma copper measurements to assess treatment efficacy and maintenance therapy success. A smaller rTMS study employed a double-blind, randomized design in 60 patients with upper limb dystonia, utilizing objective muscle tension measurements with MyotonPRO devices alongside clinical scales including the Modified Ashworth Scale, Unified Wilson's Disease Rating Scale, Burke Fahn Marsden Scale, and Activities of Daily Living assessments.

ET-700's Place in the Evolving Wilson Disease Landscape

The treatment landscape for Wilson disease has undergone significant evolution over the past five years, marked by landmark clinical trial data that has established new therapeutic standards and revealed persistent gaps in care delivery. The most pivotal development was a randomized, open-label, non-inferiority phase 3 trial conducted across 15 healthcare centres in nine countries, which compared penicillamine with trientine tetrahydrochloride (TETA4) for maintenance therapy in 53 patients with stable Wilson disease. This study demonstrated that TETA4 was non-inferior to penicillamine at both 24 and 48 weeks, with mean differences in serum non-caeruloplasmin-bound copper of -9.1 μg/L and -15.5 μg/L respectively, while maintaining 100% clinical stability across all participants. Notably, penicillamine was associated with three serious adverse events including leukopenia and malignancies, while none were reported for TETA4, supporting improved safety profiles for newer formulations.

Real-world evidence has revealed concerning patterns in treatment utilization and outcomes that contrast sharply with clinical trial successes. Large-scale database studies from the United States identified only 15.1% of 5,376 Wilson disease patients receiving documented disease-specific treatment, with a standardized mortality ratio of 2.19 compared to the general population. French national registry data similarly showed that only 43.8% of 1,520 patients received Wilson disease-specific treatment at least once over a decade-long observation period. Treatment selection patterns demonstrated significant heterogeneity, with penicillamine monotherapy remaining the most common first-line approach (45.5%), followed by trientine monotherapy (26.1%), reflecting a persistent lack of consensus regarding optimal initial therapy selection among clinicians.

Emerging data on combination therapies and long-term outcomes have provided important safety signals that are reshaping treatment paradigms. A comprehensive systematic review of 17 combination therapy studies involving 1,056 patients revealed that combination therapies were significantly less effective for hepatic manifestations compared to neurological presentations (47.1% vs 78.6% efficacy). Most critically, combination therapy with penicillamine plus zinc sulfate resulted in a significantly higher mortality rate compared to other combination approaches (16.3% vs 4.7%), establishing important contraindications for specific drug combinations. These findings, combined with healthcare resource utilization data showing annual pharmacy costs averaging $157,505 for adherent patients, underscore the complexity of optimizing both clinical outcomes and economic sustainability in Wilson disease management.

Optimizing Wilson Disease Care with Extended-Release Zinc

The initiation of a pilot clinical study for ET-700 by Eton Pharmaceuticals signals a strategic move to refine the long-term management of Wilson disease, a severe and lifelong genetic disorder of copper metabolism. For patients living with this condition, consistent adherence to anticopper therapy is paramount to prevent devastating hepatic and neurological damage. While zinc compounds are the cornerstone of maintenance treatment, the current regimen often involves multiple daily doses, which can be a significant barrier to adherence over decades. An extended-release formulation, dosed twice daily, could dramatically improve patient convenience and compliance, potentially leading to better long-term outcomes and a higher quality of life.

This development is particularly interesting due to the innovative use of 64Cu PET imaging. By directly measuring intestinal copper absorption in healthy volunteers, the study aims to establish a clear mechanistic proof-of-concept early in development. This advanced imaging technique offers a precise, objective biomarker that could significantly de-risk and accelerate the path to pivotal studies, providing a quantifiable measure of the drug's impact on copper homeostasis.

However, the journey from a pilot study in healthy volunteers to a market-ready product for a rare disease is complex. Key considerations include:

• Translating Efficacy: Demonstrating that improved copper absorption in healthy individuals translates into superior or at least non-inferior clinical efficacy and safety in actual Wilson disease patients, who present with diverse and severe symptoms, will be crucial.

• Patient Recruitment: Recruiting a sufficient cohort for pivotal trials in a rare disease population, especially one with varied clinical presentations, poses a significant logistical challenge.

• Market Acceptance: Even with potential adherence benefits, a new, potentially higher-cost formulation must navigate reimbursement landscapes where patients already face hurdles in accessing existing prescription zinc therapies.

Ultimately, if ET-700 can successfully navigate these challenges and demonstrate a tangible benefit in patient care, it could establish a new standard for maintenance therapy in Wilson disease, offering a more patient-friendly option in a market with a clear, unmet need for optimized treatment regimens. This effort underscores the ongoing drive within pharma to enhance drug delivery and patient experience, even for established therapies in orphan indications.