Clinical Summary: Antipsychotic Efficacy of KarXT (Xanomeline−Trospium): Post Hoc Analysis of Positive and Negative Syndrome Scale Categorical Response Rates, Time Course of Response, and Symptom Domains of Response in a Phase 2 Study
Acute schizophrenia still relies on dopamine D2-blocking antipsychotics, which leave many clinicians balancing symptom control against extrapyramidal effects, prolactin elevation, and tardive dyskinesia risk. This analysis asks a practical question for inpatient care: how often KarXT produces clinically meaningful PANSS response, how quickly that response emerges, and whether benefit extends beyond positive symptoms.
Key Findings
- At the week 5 study endpoint, 59.0% (n = 49) of KarXT patients met the ≥ 20% PANSS response threshold and 15.7% (n = 13) met the ≥ 50% threshold; the proportion of KarXT patients responding was consistently higher than the proportion of placebo patients across all 4 thresholds (nominal P < .05 for all response criteria).
- The corresponding NNTs (95% CI) at week 5 were NNT = 3 (3–5) for ≥ 20%, NNT = 4 (3–7) for ≥ 30%, NNT = 7 (4–20) for ≥ 40%, and NNT = 11 (6–145) for ≥ 50% improvement in PANSS total score between baseline and week 5.
- For onset of benefit, the ≥ 20% and ≥ 30% PANSS response thresholds showed significant differences favoring KarXT by week 2, whereas the ≥ 40% and ≥ 50% thresholds did not reach P < .05 until week 4.
- Patients in the KarXT group showed significant improvement over placebo from baseline to week 5 in all 5 PANSS Marder factors, with effect size differences at week 5 ranging from 0.48 to 0.66.
- Between-group differences between KarXT and placebo were significant starting at week 2 for all 5 PANSS Marder factors.
In acutely psychotic adults with schizophrenia, KarXT produced clinically meaningful short-term symptom response versus placebo, with separation by week 2 for lower PANSS response thresholds and broad improvement across all 5 PANSS symptom domains. The most practical benchmark is an NNT = 3 (3–5) for a ≥ 20% PANSS response by week 5.
Practice Implications
- Set early expectations for inpatient treatment: some clinically meaningful PANSS improvement can be detected by week 2, but larger response thresholds (≥ 40% and ≥ 50%) were not separated from placebo until week 4.
- Use response thresholds to frame discussions with teams and patients: by week 5, 59.0% (n = 49) achieved a ≥ 20% PANSS response, while 15.7% (n = 13) achieved a ≥ 50% response, so more stringent improvement is less common over 5 weeks.
- When judging benefit, look beyond positive symptoms alone; KarXT improved all 5 PANSS Marder factors, including disorganized thought, uncontrolled hostility, and anxiety/depression, with significant between-group differences starting at week 2.
- Apply these data to the right setting: this was 5 weeks of inpatient treatment in acutely psychotic adults with schizophrenia, not evidence for long-term maintenance, treatment-resistant schizophrenia, or head-to-head performance against marketed antipsychotics.
