Different Causes, Similar Psychiatric Symptoms: Protecting the Receptor

Similar hallucinations or delusions do not necessarily arise through the same mechanisms. Research into autoimmune psychiatric symptoms is seeking to turn those differences into treatment options.

An Australian clinical study investigated patients with psychotic symptoms. Some patients judged to have an autoimmune condition—based on antibody tests, cerebrospinal fluid findings, the course of their symptoms and other evidence—improved after immunotherapy. The presence of an antibody in blood was not, by itself, used to decide who should receive treatment. Clinical study ↗

In anti-NMDA receptor encephalitis, pathogenic antibodies cross-link receptors and cause them to be drawn from the neuronal surface into the cell. Even if receptors are being produced, losing them from the places where they function changes how signals are transmitted. In cultured neurons, removing patient antibodies from the culture medium allowed receptor localization at synapses to recover. Basic research ↗

That mechanism has prompted the development of a drug intended to protect receptors from pathogenic antibodies, rather than reduce the antibodies themselves.

ART5803 is a “one-armed” antibody that does not cross-link receptors. It binds to the receptor and interferes with the action of pathogenic antibodies without impairing receptor function in the experimental systems studied. Improvements in behavioral and motor abnormalities have also been reported in marmosets given pathogenic antibodies. Preclinical research ↗

In June 2026, its developer, Arialys, announced that the first patient had received ART5803 in a Phase 2a trial in South Korea. The drug has entered the stage of testing efficacy in patients; a treatment benefit has not yet been established. Clinical development announcement ↗

“Can measuring brain function help us choose an antidepressant?” ↗ examined an attempt to predict patients' responses and use those predictions to select a drug. Here, the aim is to identify patients whose apparently similar symptoms involve autoimmunity against a receptor, and then interrupt that process.

Differences that remained hidden when patients were grouped by symptoms are now informing the design of a specific drug. Alongside the question of how to measure the brain to choose a treatment, another approach is taking shape: distinguish the causes that treatment needs to address.