Prior studies demonstrated the antipsychotic activity of the dual M1/M4 preferring muscarinic receptor agonist xanomeline 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 side effects due to peripheral muscarinic receptor activation. The efficacy and safety of KarXT in schizophrenia were demonstrated in the 5-week, randomized, double-blind, placebo-controlled EMERGENT-1 (NCT03697252), EMERGENT-2 (NCT04659161), and EMERGENT-3 (NCT04738123) trials.

The EMERGENT trials randomized people with a recent worsening of positive symptoms warranting hospitalization, Positive and Negative Syndrome Scale (PANSS) total score ≥80, and Clinical Global Impression–Severity (CGI-S) score ≥4. KarXT dosing (xanomeline/trospium) started at 50 mg/20 mg twice daily (BID) and increased to a maximum of 125 mg/30 mg BID. In each trial, the primary efficacy endpoint was change from baseline to week 5 in PANSS total score. Other efficacy measures included change from baseline to week 5 in PANSS positive subscale, PANSS negative subscale, PANSS Marder negative factor, and CGI-S scores. Data from the EMERGENT trials were pooled, and efficacy analyses were conducted in the modified intent-to-treat population, defined as all randomized participants who received ≥1 trial drug dose and had a baseline and ≥1 postbaseline PANSS assessment.

The pooled analyses included 640 participants (KarXT, n=314; placebo, n=326). Across trials, KarXT was associated with a significantly greater reduction in PANSS total score at week 5 compared with placebo (KarXT, -19.4; placebo, -9.6 [least squares mean (LSM) difference, -9.9; 95% CI, -12.4 to -7.3; P<0.0001; Cohen’s d, 0.65]). At week 5, KarXT was also associated with a significantly greater reduction than placebo in PANSS positive subscale (KarXT, -6.3; placebo, -3.1 [LSM difference, -3.2; 95% CI, -4.1 to -2.4; P<0.0001; Cohen’s d, 0.67]), PANSS negative subscale (KarXT, -3.0; placebo, -1.3 [LSM difference, -1.7; 95% CI, -2.4 to -1.0; P<0.0001; Cohen’s d, 0.40]), PANSS Marder negative factor (KarXT, -3.8; placebo, -1.8 [LSM difference, -2.0; 95% CI, -2.8 to -1.2; P<0.0001; Cohen’s d, 0.42]), and CGI-S scores (KarXT, -1.1; placebo, -0.5 [LSM difference, -0.6; 95% CI, -0.8 to -0.4; P<0.0001; Cohen’s d, 0.63]).

In pooled analyses from the EMERGENT trials, KarXT demonstrated statistically significant improvements across efficacy measures with consistent and robust effect sizes. These findings support the potential of KarXT to be first in a new class of medications to treat schizophrenia based on muscarinic receptor agonism and without any direct dopamine D2 receptor blocking activity.

Karuna Therapeutics