Arcturus Reports Interim Phase 2 ARCT-810 Data in OTC Deficiency, Unveils LUNAR 2.0 Delivery Platform
核心洞察
Arcturus Therapeutics (搜索) reported interim Phase 2 results showing ARCT-810 was generally safe and well tolerated in patients with ornithine transcarbamylase deficiency (搜索).
ARCT-810 reduced or maintained first morning fasting ammonia within the normal range, including during increases in participants' protein intake, and reduced glutamine.
The company introduced LUNAR 2.0 (搜索), a next-generation mRNA delivery platform showing 38- to 40-fold higher protein expression than prior lipids in non-human primate studies.
Arcturus Therapeutics (搜索) reported interim Phase 2 results for ARCT-810 in ornithine transcarbamylase (搜索) (OTC) deficiency, describing the investigational mRNA therapeutic as generally safe and well tolerated with encouraging activity across key urea cycle biomarkers. The San Diego company also introduced LUNAR 2.0 (搜索), its next-generation mRNA delivery platform, and outlined plans to fold a follow-on candidate, ARCT-2601 (搜索), into the same ongoing study.
In the Phase 2 study to date, ARCT-810 reduced and/or maintained first morning fasting ammonia within the normal range, including during increases in protein intake by participants. The therapy also reduced glutamine, with participants at the 0.5 mg/kg dose level achieving mean glutamine values within the normal range during treatment. Weight gain was observed in all participants.
"The ARCT-810 Phase 2 interim results validate Arcturus' mRNA liver therapeutics platform and the introduction of LUNAR 2.0 (搜索) marks the beginning of a new and exciting chapter for Arcturus," said Joseph Payne, President and CEO of Arcturus.
Biomarker Rationale in Urea Cycle Disorders
Arcturus frames first morning fasting ammonia as a key monitoring endpoint because hyperammonemia drives the neurocognitive morbidity associated with OTC deficiency. A post hoc analysis of more than 1,000 ammonia results from 114 patients with urea cycle disorder enrolled in four short-term ammonia scavenger switchover studies showed that first morning fasting plasma ammonia is the least variable of ammonia measurements and correlates well with ammonia AUC0-24, a predictor of hyperammonemia crisis risk (Lee et al., 2015).
Glutamine serves as a complementary biomarker of nitrogen buffering capacity. In urea cycle disorders, excess nitrogen is initially incorporated into glutamine, which rises as a compensatory mechanism before ammonia levels spike, making it more stable in patients who are not hyperammonemic. Glutamine assessments show significantly lower intra-subject variability than ammonia, 15% versus 56%, according to the company (Lee et al., 2016).
LUNAR 2.0 and the Next-Generation Candidate
LUNAR 2.0 (搜索) incorporates improved lipids and a formulation process specific to those lipids. In non-human primates, the platform demonstrated a 40-fold improvement over LUNAR 1.0 in expressing human erythropoietin. In a separate non-human primate study, LUNAR 2.0 exhibited 38-fold greater potency than ATX-95, the key lipid in ARCT-810, in expressing human ornithine transcarbamylase (搜索). Arcturus states that the platform unlocks therapeutic opportunities previously inaccessible, including phenylketonuria (搜索) (PKU) and gout (搜索).
"The greater than 30-fold improvement demonstrated by the next-generation platform is exciting and has the potential to translate into a more effective and more convenient therapy," said Dr. Marshall Summar, former founding member and Executive Committee member of the NIH Urea Cycle Disorders Consortium. "I believe ARCT-2601 (搜索) has the potential to become a new standard of care for OTCD patients, particularly in severe onset, if approved."
ARCT-2601 (搜索) is an intravenously administered mRNA therapeutic designed to express normal functional OTC enzyme in the liver. It has shown a similar safety profile to ARCT-810 in non-GMP preclinical studies. Following a Type C meeting in June, the FDA provided favorable feedback and regulatory-path clarity, and Arcturus plans to begin dosing ARCT-2601 near year-end in participants with OTC deficiency aged 12 years and older. The candidate will be integrated into the current ARCT-810 Phase 2 study under an amended protocol. Based on non-human primate data, Arcturus anticipates that ARCT-2601 will allow lower and/or less frequent dosing.
"Validating clinical data, a compellingly differentiated LUNAR 2.0 (搜索) mRNA delivery platform, and a proprietary AI computational engine, support the continued advancement of Arcturus' growing mRNA therapeutics pipeline, including ARCT-2601 (搜索), and the initiation of new programs, such as Phenylketonuria (搜索) (PKU) and Gout (搜索)," said Dr. Pad Chivukula, Chief Scientific Officer of Arcturus.
AI Acquisition to Support mRNA Design
Arcturus has entered a definitive agreement to acquire myNEO (搜索), an AI discovery company, subject to customary closing conditions. The transaction is expected to close in October. Arcturus has worked closely with myNEO since 2024. The acquisition brings a differentiated computational engine supported by proprietary intellectual property, intended to strengthen Arcturus' AI infrastructure by improving mRNA design quality and enhancing target identification.
Disease Burden and Current Standard of Care
OTC deficiency is the most common urea cycle disorder, a group of inherited metabolic liver disorders that impair removal of toxic waste products from protein digestion. The condition is caused by mutations in the X-linked OTC gene (搜索), leading to a non-functional or deficient OTC enzyme, and usually affects males more severely. OTC catalyzes conversion of toxic ammonia to urea for renal excretion; when this fails, patients face high ammonia levels, elevated blood glutamine with low to normal citrulline, and increased urine orotic acid. High blood ammonia can cause crises with seizures, progressive neurocognitive impairment, coma, and death.
Severe cases usually present early in life, while patients with milder symptoms may be diagnosed as adolescents or adults. There is no cure apart from liver transplant, which carries risks of surgical and postsurgical complications including organ rejection and requires lifelong immunosuppressant therapy. The current standard of care consists of a low-protein diet, substitution of essential amino acids, and nitrogen scavenging medications. Arcturus notes that this approach is challenging to maintain, may not prevent chronic neurotoxic effects, and does not address the underlying cause of disease. Approximately 10,000 people in Europe and the United States have OTC deficiency.
ARCT-810 holds Orphan Medicinal Product Designation and an approved pediatric investigation plan from the European Medicines Agency (搜索), plus Orphan Drug Designation, Fast Track Designation, and Rare Pediatric Disease Designation from the FDA. Both ARCT-810 and ARCT-2601 (搜索) use the company's LUNAR delivery technology to deliver OTC mRNA to hepatocytes.