Xanomeline and Trospium Chloride: Mechanism of Action, Clinical, and Translational Science

Xanomeline-trospium chloride (Cobenfy, formerly KarXT) is a first-in-class, oral central M1/M4 muscarinic receptor agonist approved for the treatment of schizophrenia in adults. Cobenfy represents a paradigm shift by avoiding direct dopamine D2 receptor blockade and thus significantly reduces the burden of metabolic, extrapyramidal, and sedative side effects observed in standard first and second-generation antipsychotics. Trospium chloride is a peripheral muscarinic antagonist with negligible blood-brain barrier penetration. Cobenfy is co-formulated with trospium to minimize peripheral cholinergic effects caused by xanomeline. Under fasting conditions, xanomeline and trospium reach peak plasma concentrations (T_max) in 2 and 1 h, and maximum concentrations (C_max) of 1955 and 5787 pg/mL, respectively. While food intake does not change xanomeline pharmacokinetics, it reduces trospium C_max by around 70%. Xanomeline has a high volume of distribution (10,800 L) and is metabolized by several cytochrome P450 (CYP) enzymes. Trospium is a P-glycoprotein (P-gp) substrate and is 85% eliminated in feces. In phase III clinical trials (EMERGENT-2, EMERGENT-3), Cobenfy significantly reduced PANSS total scores (least squares mean difference -9.6 and -8.4, respectively; p < 0.0001) compared to placebo. Treatment-emergent adverse events were primarily mild to moderate in severity and were mainly transient nausea (19%), constipation (17%), dyspepsia (15%), and vomiting (14%). Discontinuation rates due to adverse events were low (6.2% vs. 5.2% for placebo), and Cobenfy was not associated with weight gain, extrapyramidal symptoms, or cardiometabolic risks seen in conventional antipsychotics.