In prior studies, the dual M1/M4 preferring muscarinic receptor agonist xanomeline demonstrated antipsychotic activity in people with schizophrenia and Alzheimer’s disease, but its further clinical development was limited primarily by gastrointestinal side effects. KarXT combines xanomeline and the peripherally restricted muscarinic receptor antagonist trospium chloride. KarXT is designed to preserve xanomeline’s beneficial central nervous system effects while mitigating adverse events (AEs) due to peripheral muscarinic receptor activation. The efficacy and safety of KarXT in schizophrenia was demonstrated in the 5-week, randomized, double-blind, placebo-controlled EMERGENT-1 (NCT03697252), EMERGENT-2 (NCT04659161), and EMERGENT-3 (NCT04738123) trials.

The EMERGENT trials enrolled people with a recent worsening of positive symptoms warranting hospitalization, Positive and Negative Syndrome Scale total score ≥80, and Clinical Global Impression–Severity score ≥4. Eligible participants were randomized 1:1 to KarXT or placebo. KarXT dosing (xanomeline/trospium) started at 50 mg/20 mg twice daily (BID) and increased to a maximum of 125 mg/30 mg BID. Safety was assessed by monitoring for spontaneous AEs after administration of the first dose of trial drug until the time of discharge on day 35. Data from the EMERGENT trials were pooled, and all safety analyses were conducted in the safety population, defined as all participants who received ≥1 dose of trial drug.

A total of 683 participants (KarXT, n=340; placebo, n=343) were included in the pooled safety analyses. Across the EMERGENT trials, 51.8% of people in the KarXT group compared with 29.4% in the placebo group reported ≥1 treatment-related AE. The most common treatment-relatedAEs occurring in ≥5% of participants receiving KarXT and at a rate at least twice that observed in the placebo group were nausea (17.1% vs 3.2%), constipation (15.0% vs 5.2%), dyspepsia (11.5% vs 2.3%), vomiting (10.9% vs 0.9%), and dry mouth (5.0% vs 1.5%). The most common treatment-related AEs in the KarXT group were all mild or moderate in severity.

In pooled analyses from the EMERGENT trials, KarXT was generally well tolerated in people with schizophrenia experiencing acute psychosis. These findings, together with the efficacy results showing a clinically meaningful reduction in the symptoms of schizophrenia, support the potential of KarXT to be the first in a new class of antipsychotic medications based on muscarinic receptor agonism and a well-tolerated alternative to currently available antipsychotics.

Karuna Therapeutics