What Is Xanomeline? A New Treatment for Schizophrenia

Xanomeline is a drug that activates muscarinic acetylcholine receptors in the brain, and it represents the first genuinely new mechanism for treating schizophrenia in over seven decades. Every antipsychotic on the market until now has worked by blocking dopamine receptors. Xanomeline does not. Instead, it stimulates a different signaling system, the cholinergic system, by targeting two specific receptor subtypes called M1 and M4. Combined with a second drug called trospium chloride to manage its gut-related side effects, it was approved by the U.S. Food and Drug Administration in 2024 under the brand name Cobenfy.

How Xanomeline Works in the Brain

The central idea behind xanomeline is that schizophrenia involves more than just excess dopamine. Muscarinic receptors, particularly the M1 and M4 subtypes, play key roles in regulating both glutamate and dopamine signaling in the brain.¹ Xanomeline crosses the blood-brain barrier and directly stimulates these receptors.²

The M1 receptor is concentrated in the prefrontal cortex, a brain region critical for working memory, planning, and cognitive flexibility. People with schizophrenia show deficits in M1 receptor signaling in this area.³ In animal research, activating M1 receptors in the prefrontal cortex improved the firing patterns of neurons involved in spatial memory, essentially sharpening the signal that those cells carry.⁴ This is one reason researchers have been hopeful that xanomeline could address the cognitive and “negative” symptoms of schizophrenia (things like social withdrawal and flat emotional expression), which existing drugs handle poorly.

The M4 receptor, on the other hand, appears to indirectly dial down dopamine activity in the striatum, a brain region tied to psychosis. Research has shown that M4 receptors on a specific class of neurons in the striatum trigger a cascade involving the endocannabinoid system that produces a sustained reduction in dopamine release.⁵ So rather than blocking dopamine receptors directly, as every existing antipsychotic does, xanomeline turns down the dopamine tap upstream. This is a fundamentally different strategy, and it is why the drug has generated so much attention in psychiatry.

Why Xanomeline Needed a Partner Drug

Xanomeline itself is not new. It was first studied in the 1990s as a potential treatment for Alzheimer’s disease. In those early trials, it showed intriguing effects on behavioral symptoms like hallucinations, delusions, and agitation in Alzheimer’s patients.⁶ But development stalled because muscarinic receptors are not just in the brain. They are spread throughout the body, especially in the gut, bladder, and salivary glands. Activating those receptors outside the brain caused severe gastrointestinal problems: nausea, vomiting, diarrhea, and excessive salivation that many people could not tolerate.⁷ For years, xanomeline sat on the shelf as a drug with promising brain effects but unacceptable body-wide side effects.⁸

The workaround was to pair it with trospium chloride, a muscarinic receptor blocker that cannot cross the blood-brain barrier.⁹ Trospium stays in the body’s periphery and counteracts xanomeline’s activation of muscarinic receptors in the gut and other organs, while leaving xanomeline free to do its work in the brain. Phase 1 testing confirmed that adding trospium reduced the cholinergic side effects that had previously made xanomeline unusable.¹⁰ This combination, known during development as KarXT and later branded Cobenfy, is what ultimately made it to market.

Results From the Clinical Trials

The pivotal evidence came from the EMERGENT series of randomized, placebo-controlled trials in adults with schizophrenia. In the EMERGENT-2 trial, xanomeline-trospium reduced scores on the standard measure of schizophrenia symptoms (the PANSS total score) by about 21 points from baseline over five weeks, compared to roughly 12 points in the placebo group.¹¹ That roughly 10-point gap between drug and placebo, with a moderate effect size, is in the same ballpark as other antipsychotics but achieved through an entirely different mechanism. All secondary measures favored the drug over placebo as well.¹²

A separate trial, EMERGENT-3, confirmed these results with a statistically significant 8.4-point advantage over placebo in PANSS total score at five weeks, and meaningful reductions on both positive symptoms (like hallucinations and delusions) and other symptom domains.¹³ A meta-analysis of the trial data found that symptom improvements were noticeable as early as two weeks after starting treatment, and that xanomeline-trospium also helped negative symptoms in patients who had prominent negative symptoms at baseline, and cognitive symptoms in patients who started out cognitively impaired.¹⁴

The Side Effect Profile

This is where xanomeline-trospium stands apart from traditional antipsychotics in a way that matters enormously to patients. Standard antipsychotics, because they block dopamine receptors, come with a well-known burden of side effects: weight gain, metabolic problems (rising blood sugar and cholesterol), movement disorders like tremor and stiffness, hormonal disruption from elevated prolactin, and sedation. These side effects are a major reason people stop taking their medications, and non-adherence is one of the biggest drivers of relapse in schizophrenia.¹⁵

Xanomeline-trospium’s side effects look very different. Across the pooled EMERGENT trial data, the most common issues were gastrointestinal: nausea (about 17% versus 3% on placebo), constipation (15% versus 5%), dyspepsia (about 12% versus 2%), vomiting (about 11% versus 1%), and dry mouth (5% versus 2%).¹⁶ These were almost all mild or moderate, and many were transient, resolving as treatment continued. Perhaps more striking is what the drug did not cause. A systematic review found that xanomeline-trospium was not associated with clinically meaningful motor symptoms, elevated prolactin, or the kind of metabolic syndrome that makes second-generation antipsychotics so problematic. The risk of gaining 7% or more of body weight was actually lower in people taking xanomeline-trospium than in those taking placebo.¹⁴

That said, the drug is not free of concerns. Hypertension showed up in trial data, and some gastrointestinal effects, while tolerable for most people, were common enough that roughly half of people in the longer-term studies did not complete the full trial duration.¹⁷ Some of that attrition was not due to side effects specifically, but it is worth keeping in mind.

Longer-Term Data

The acute trials were only five weeks long, which is standard for schizophrenia drug approval but leaves open the question of what happens over months and years. Two open-label extension studies have now followed people taking xanomeline-trospium for up to a year. In one 52-week trial, the most common side effects remained gastrointestinal (nausea, vomiting, constipation) and were mostly mild or moderate. No new safety concerns emerged beyond what was seen in the short-term trials, and the drug was not associated with clinically meaningful weight gain, motor symptoms, or metabolic deterioration.¹⁸

Symptom improvement continued to deepen over the longer treatment period. People who had responded during the original five-week trials showed further reductions in PANSS scores out to week 52, reaching an average improvement of more than 30 points from baseline.¹⁸ A larger open-label study of 566 participants over 52 weeks showed a similar pattern of improving symptoms alongside a manageable side effect profile, though about half of participants did discontinue during the trial for various reasons.¹⁷ Open-label studies do not have the rigor of blinded, placebo-controlled trials, so these results need to be interpreted with that in mind. But the absence of weight gain and metabolic side effects holding up over a year is genuinely reassuring, given how devastating those effects are with many existing antipsychotics.

What Patients Actually Report

Clinical trials measure symptom scores, but what matters to people living with schizophrenia is how a medication affects their daily life and whether it feels worth taking. A qualitative study asked participants who had taken xanomeline-trospium in clinical trials about their experience. On average, participants rated their satisfaction with the drug at 8.1 out of 10, compared to about 6 out of 10 for their previous antipsychotic treatments. Over 93% said they would recommend xanomeline-trospium to a friend or family member.¹⁹

Those numbers reflect something that is hard to capture in PANSS scores. When your antipsychotic makes you gain 30 pounds, feel sedated, or develop involuntary movements, the medication itself becomes a source of distress and stigma. A drug that controls symptoms without those particular burdens could meaningfully change whether people stick with treatment. Better adherence over time generally means fewer psychotic relapses, fewer hospitalizations, and more independence.

What About Treatment-Resistant Schizophrenia

One question that comes up quickly is whether xanomeline-trospium helps people who have not responded to existing antipsychotics. Clozapine is currently the only drug with established evidence for treatment-resistant schizophrenia, and even clozapine does not work for everyone. Early case reports of adding xanomeline-trospium to clozapine in people with clozapine-resistant illness have been mixed. In one case, a patient with clozapine dose limitations was ultimately stabilized on a combination of clozapine and xanomeline-trospium, though she also needed electroconvulsive therapy for full benefit. In another case, the combination caused increased salivation and no clear improvement, and the xanomeline-trospium was discontinued.²⁰

Two case reports are far too little to draw any real conclusions. But they highlight an important limitation: the EMERGENT trials enrolled people with active symptoms who were not on clozapine, so the drug’s evidence base does not yet extend to the most difficult-to-treat patients. Whether xanomeline-trospium works as monotherapy or as an add-on in treatment-resistant cases will need dedicated studies.

FDA Approval and Where It Fits

The FDA approved xanomeline-trospium (branded as Cobenfy) in 2024 for the treatment of schizophrenia in adults.²¹ This made it the first antipsychotic approved with a non-dopamine mechanism, a milestone that has been described repeatedly as the first truly new approach to psychosis since chlorpromazine in the 1950s.²²

That framing, while technically accurate, deserves some context. Cobenfy’s clinical trial performance in terms of symptom reduction is broadly comparable to existing antipsychotics, not dramatically superior. Its advantage is its side effect profile, which avoids the metabolic and motor problems that plague dopamine blockers. For many patients and clinicians, that difference alone is reason enough to try it, especially for people who have stopped previous medications because of weight gain or movement disorders. But it is not a cure, and the trials tested it in relatively uncomplicated populations (acute schizophrenia exacerbations in people who were not on clozapine). How it performs in the messy complexity of real-world schizophrenia treatment, as a long-term medication across diverse patients, is still being learned.

Other Muscarinic Drugs in Development

Xanomeline-trospium’s approval has validated the muscarinic receptor approach and opened the door for other companies to pursue the same pathway with different strategies. One notable drug in development is emraclidine, which takes a more targeted approach by selectively boosting M4 receptor activity without directly activating M1. The idea is that focusing on M4 alone could retain the antipsychotic effect (through downstream reduction of dopamine signaling) while potentially avoiding side effects linked to broad muscarinic activation.²³ Emraclidine is in Phase 2 trials for both schizophrenia and psychosis associated with Alzheimer’s disease.

This kind of pharmacological refinement is common after a first-in-class drug reaches the market. The first drug proves the concept works in humans; the next generation tries to improve on specificity, tolerability, or dosing convenience. Whether M4-selective drugs will prove better, worse, or simply different from xanomeline-trospium remains to be seen. But the broader shift is clear: after decades of dopamine-centric drug development, the muscarinic system has become one of the most active areas of schizophrenia research, with multiple compounds and approaches being tested simultaneously.

The Trospium Piece and Anticholinergic Concerns

One aspect of xanomeline-trospium that generates questions is the trospium component itself. Trospium is a muscarinic blocker, the same class of drug that in other contexts is associated with cognitive impairment, particularly in older adults. There is growing concern in geriatric medicine about anticholinergic burden, the cumulative cognitive harm from taking drugs that block acetylcholine activity. So how does a drug that combines a muscarinic activator with a muscarinic blocker avoid this problem?

The answer comes back to the blood-brain barrier. Trospium does not enter the brain in meaningful amounts.⁹ Its anticholinergic effects are confined to the gut, bladder, and other peripheral organs, which is exactly where it is meant to act, muting the nausea and GI distress that xanomeline would otherwise cause. In the brain, xanomeline gets to work unopposed. The 52-week safety data did not show cognitive worsening, and in fact patients with baseline cognitive impairment showed some improvement.¹⁴ Still, as the drug enters wider use, monitoring for any unexpected cognitive effects, particularly in older patients or those taking other anticholinergic medications, will be important.

The Alzheimer’s Disease Connection

Xanomeline’s story began with Alzheimer’s disease, and that thread has never fully gone away. The original Alzheimer’s trials in the 1990s showed that the drug reduced behavioral symptoms like hallucinations, delusions, and agitation in a dose-dependent manner.⁶ Those psychiatric benefits in a dementia population were actually what tipped off researchers to xanomeline’s potential in schizophrenia. The observation that a drug originally designed for memory problems also quieted psychosis suggested it was hitting something fundamental about how the brain generates psychotic symptoms.

Psychosis in Alzheimer’s disease is a significant clinical problem with few good treatment options. Existing antipsychotics carry black-box warnings about increased mortality in elderly dementia patients. A muscarinic-based approach that avoids dopamine blockade could theoretically be safer in this population. Emraclidine, the M4-selective compound mentioned earlier, is being studied specifically for Alzheimer’s-related psychosis alongside its schizophrenia program.²³ Whether xanomeline-trospium itself will be tested or approved for dementia-related psychosis is an open question, but the pharmacological logic for trying is strong.