Programs for ST-905 and ST-905 for Schizophrenia and Depression Launched by Syremis Therapeutics

Syremis Therapeutics announced programs for ST-905 and ST-901, 2 new drugs in schizophrenia and major depressive disorder, respectively.¹ These novel drugs will undergo research for treatment of schizophrenia, Alzheimer disease psychosis, and other neuropsychiatric conditions.

Syremis plans the lead program for ST-905, a dual M1/M4 muscarinic agonist in development for schizophrenia and other conditions. ST-905 research is currently in phase 1. Another program for ST-901, for the novel NMDA receptor antagonist, will advance. The drug is currently in studies that will enable an Investigational New Drug application. ST-901 research is intended for treatment of major depressive disorder and bipolar depression.

“Schizophrenia and Alzheimer’s disease psychosis remain two of the most challenging of all neuropsychiatric disorders, and the need for new and effective therapies could not be greater,” said Steve Paul, MD, Syremis’ co-founder and member of the board of directors, and former chief executive officer and chair of Karuna Therapeutics. “With its balanced M1/M4 profile and promising pharmaceutical properties, Syremis has the potential to build on important clinical progress and ultimately transform the treatment landscape for patients and their families,” he added in a press release.

ST-905 is a dual M1/M4 muscarinic agonist, with differentiated potency and favorable pharmaceutical properties. Activation of M1 and M4 receptors is thought to influence cortical and striatal signaling involved in cognition, psychosis, and mood regulation, potentially improving both positive symptoms and cognitive deficits without the extrapyramidal side effects commonly associated with antipsychotics. Because of its structure, the drug may be useful across multiple neuropsychiatric indications and symptom domains, with potential for oral dosing once-daily and a long-acting injectable formulation. Long-acting options are particularly relevant in schizophrenia, where medication nonadherence remains a major contributor to relapse, hospitalization, and functional decline. ST-901 is a novel NMDA antagonist intended to treat major depressive disorder and bipolar depression. NMDA receptor modulation has gained clinical relevance following the success of ketamine-based therapies, which have demonstrated rapid antidepressant effects in treatment-resistant depression.

“Syremis was founded with a shared vision to advance mental health care through innovation grounded in emerging scientific and clinical insights”, said Elisabeth Kogan, cofounder and chief executive officer of Syremis Therapeutics, in a press release. “We are excited to announce the Series A financing to rapidly advance our pipeline into clinical proof of concept,” she highlighted.

The programs underscore a renewed focus on mechanistically differentiated therapies that move beyond traditional dopaminergic and monoaminergic approaches, which have dominated psychiatric treatment for decades but often fail to address core symptoms or are limited by tolerability concerns. The company launched $165 million in financing, they announced in a press release. According to Syremis Therapeutics, phase 1 studies for ST-901 are expected to enter phase 1 development next year, and ST-905 ongoing phase 1 studies will continue.

References

1. Syremis Therapeutics launches with $165M to develop best-in-class medicine for mental health conditions. Press release. December 18, 2025. Accessed December 23, 2025. https://www.businesswire.com/news/home/20251218743253/en/Syremis-Therapeutics-Launches-with-%24165M-to-Develop-Best-in-Class-Medicines-for-Mental-Health-Conditions

2. Syremis Therapeutics Ltd. IVC Data and Insights. Accessed December 23, 2025. https://www.ivc-online.com/Google-Card?id=c5cc8be3-7ede-f011-b81b-00505695cd29