The US Food and Drug Administration (FDA) has approved Cobenfy for the treatment of schizophrenia, marking the first novel mechanism of action in over 70 years for this condition. Developed by Karuna Therapeutics, now a part of Bristol Myers Squibb, Cobenfy targets muscarinic cholinergic receptors, offering a new approach to managing this complex psychiatric disorder.
Schizophrenia affects approximately 25 million people worldwide and is characterized by a range of symptoms, including positive symptoms like delusions and hallucinations, negative symptoms such as loss of pleasure and emotion, and cognitive deficits affecting memory and attention. Current treatments primarily focus on dopamine pathways, leaving a significant unmet need for therapies addressing the full spectrum of symptoms.
Cobenfy: A Dual-Action Approach
Cobenfy is an atypical antipsychotic comprised of two components: xanomeline and trospium. Xanomeline is an agonist of muscarinic M1 and M4 receptors in the central nervous system. Initially tested by Eli Lilly as a potential Alzheimer's treatment, xanomeline showed promise in reducing psychotic symptoms. However, its development was hindered by systemic side effects due to widespread receptor activation.
To address these side effects, Andrew Miller, now an advisor at Bristol Myers Squibb, combined xanomeline with trospium, a pan-muscarinic antagonist. Trospium selectively blocks muscarinic receptors in the periphery, minimizing systemic side effects while allowing xanomeline to exert its therapeutic effects in the brain. According to Ken Kramer, Vice President and Head of Medical Affairs, Neuropsychiatry Therapeutic Area at Bristol Myers Squibb, trospium's inability to cross the blood-brain barrier is key to this targeted action.
Clinical Trial Results
The FDA approval of Cobenfy was based on data from two Phase 3 trials, EMERGENT-2 and EMERGENT-3, each enrolling approximately 250 participants with schizophrenia. These placebo-controlled trials, lasting five weeks, used the Positive and Negative Syndrome Scale (PANSS) as the primary endpoint. Both trials demonstrated statistically significant improvements in PANSS scores in the Cobenfy groups compared to placebo.
The study populations were notably diverse, with Black or African American volunteers representing the largest racial group. This is particularly relevant given that Black individuals are 2.5 times more likely to be diagnosed with schizophrenia. While some gastrointestinal side effects were observed, the dropout rate in the Cobenfy groups was not significantly higher than in the placebo groups.
In the EMERGENT-2 study, participants also showed a significant improvement in negative symptoms, although this was not replicated in EMERGENT-3. This mixed result highlights the ongoing need for further research into the drug's effects on specific symptom domains.
Implications and Future Directions
Cobenfy's novel mechanism of action, targeting muscarinic acetylcholine receptors, offers a new avenue for treating schizophrenia. These receptors are thought to modulate dopamine release presynaptically, potentially providing a different approach compared to traditional dopamine-blocking antipsychotics. Margaret McNamara McClure, a psychologist at Fairfield University, emphasizes the need for longer-term data to fully assess Cobenfy's potential to improve functional recovery in patients.
Bristol Myers Squibb is continuing to investigate Cobenfy's effects, including potential benefits on cognitive symptoms through mechanisms independent of dopamine modulation. The company aims to provide comprehensive data to healthcare providers and patients to support informed treatment decisions.
