PROGRAM
INDICATION
PRECLINICAL
IND ENABLING
PHASE 1
PHASE 2
PHASE 3
ART5803
  • ANRE
  • Autoimmune Psychosis
  • Study ART5803-201
  • ANRE
  • Study ART5803-202
  • Schizophrenia
ART5900 (BBB Technology)
  • Anti-NMDAR
    Autoimmunity
Study ART5803-201 is an open label Phase 2a signal seeking study in acute and chronic ANRE patients and psychosis patients that exhibit anti-NMDAR autoimmunity, actively enrolling patients in Korea.

Study ART5803-202 is a randomized, placebo-controlled Phase 2 study in ANRE patients planned to initiate enrollment in the USA in 2H2026.

About ANRE

Anti-NMDA receptor encephalitis (ANRE) is a rare, potentially lethal, poorly managed, and often misdiagnosed neurological disease. ANRE is caused by pathogenic autoantibodies that bind to and crosslink NMDA receptors in the brain, leading to receptor internalization and synaptic dysfunction. The result is a range of debilitating neuropsychiatric symptoms including psychiatric and behavioral alterations, cognitive decline, seizures, coma, and diminished autonomic function. A significant percentage of ANRE patients are pediatric, where NMDA receptor-specific autoantibodies can also result in neurological development deficits. There are no approved therapies for this disease, and current treatments rely on broad immunosuppressive agents, which are associated with delayed efficacy and significant side effects.

About Autoimmune Neuropsychiatric Disease

Recent findings have identified anti-NMDA receptor autoantibodies in additional neurological and psychiatric diseases such as schizophrenia, depression, bipolar disorder and dementia. Arialys is initiating clinical assessment of ART5803 in ANRE and anti-NMDA receptor autoantibody-positive psychosis and plans future development in a subpopulation of schizophrenia patients. The company has used a proprietary high-throughput and highly sensitive assay to screen patient samples for NMDA receptor autoantibodies; identifying disease indications and subpopulations for clinical development.

About ART5803

Arialys scientists used crystallographic structures and pharmacological assessments to develop ART5803, the first precision therapeutic directly targeting the pathological effects of autoantibodies on the NMDA receptor. ART5803 is a humanized, monovalent monoclonal antibody. In preclinical models, ART5803 rapidly reversed behavioral symptoms caused by NMDAR autoantibody pathogenicity. Arialys has completed Phase 1 SAD and MAD clinical assessments in healthy volunteers. ART5803 demonstrated safety, pharmacokinetics, and CNS penetration conducive to further clinical assessment. Arialys has received Orphan Drug Designation and Rare Pediatric Designation from the U.S. FDA for ART5803. ART5803 has now entered Phase 2 clinical development.

About ART5900

Arialys has developed proprietary blood-brain barrier (BBB) penetrant technology. ART5900 combines the precision and specificity of ART5803 for targeting the NMDA receptor with demonstrated, significantly higher BBB penetrance. Potential future applications of ART5900 include lower dose, outpatient or self-administration of a precision therapeutic for the treatment of chronic anti-NMDAR autoimmunity.

Publications and Presentations

Matsumoto M, Maurer M, Purcell A, Singh A, Bilic S, Jefson M, Flynn P. ART5803, a first-in-class precision medicine to treat anti-NMDA receptor encephalitis: First-in-human Phase 1 clinical safety and pharmacokinetic profile. Poster presented at: 78th American Academy of Neurology (AAN) Annual Meeting; April 18–22, 2026.

View poster.

Yamaki S, Kazimi R, Eastman V, Martinez A, Razai A, Snipas S, Jefson M, Flynn P, Rohleder C, Koethe D, Leweke FM, Hattori K, Matsumoto M. A novel ELISA for semi-quantitative detection of IgG, IgA, and IgM autoantibodies targeting the N-terminal domain of the GluN1 subunit of NMDA receptors in neuropsychiatric and neurologic disorders. Poster TU192 presented at: 64th American College of Neuropsychopharmacology (ACNP) Annual Meeting; January 12–15, 2026.

View poster.

Kanno A, Kito T, Maeda M, et al. Monoclonal humanized monovalent antibody blocking therapy for anti-NMDA receptor encephalitis. Nature Communications. 2025;16:5292.

Read publication.

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