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TC-5619 was Targacept's alpha7 nicotinic acetylcholine receptor partial agonist, one of the most closely watched compounds of the alpha7-for-schizophrenia wave that swept through pharma in the early 2010s. An initial exploratory Phase II trial, run as an add-on to quetiapine or risperidone in schizophrenia outpatients, found statistically significant improvement on both a spatial-learning task (the Groton Maze Learning Task) and negative symptoms (SANS), enough of a signal that Targacept and its partner AstraZeneca pushed forward into a much larger, 477-patient, six-country Phase II trial. That bigger confirmatory study failed to replicate the earlier benefit, joining ABT-126, AQW051, and encenicline in the broader collapse of the alpha7 nicotinic hypothesis for schizophrenia cognition; AstraZeneca and Targacept discontinued the program not long after, and Targacept itself later folded into Catalyst Biosciences.
- significant improvement on the Groton Maze Learning Task and SANS negative symptom scores in an exploratory trial
- generally well tolerated with no clinically noteworthy safety findings
- add-on design meant it was tested alongside real-world antipsychotic regimens (quetiapine, risperidone)
- results added to a broader pattern of alpha7 nicotinic agonists failing to scale up
- Targacept, the company behind TC-5619, was a spinoff of R.J. Reynolds Tobacco's research division, which had studied nicotinic receptor pharmacology for decades before pivoting into CNS drug development.
Mechanism
Selective alpha7 receptor partial ; targets cholinergic circuits implicated in attention, working memory, and sensory gating deficits in schizophrenia.
Dosingtypical ranges, not medical advice
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Safetyrisks and cautions, not medical advice
Roughly 1,200 people took this drug across six registered trials in schizophrenia, adult ADHD and older adults with and without Alzheimer's disease, including 477 patients dosed daily for 24 weeks at 5 mg or 50 mg. The published verdict on all of it was that TC-5619 was generally well tolerated, with no adverse effect that separated it from placebo in a way worth naming. Nothing here suggests a hidden toxicity; the alpha-7 program collapsed on efficacy rather than on harm. What is missing is exposure beyond six months, because no trial ran longer and none is planned.
History
Developed by Targacept in partnership with AstraZeneca; a 185-patient exploratory Phase II trial showed significant cognitive and negative-symptom improvement, but a larger 477-patient confirmatory Phase II trial across six countries failed to replicate the effect, and the program was discontinued.
Subjective profileweighing the evidence above
The alpha7 nicotinic story's second act, and it ended the same way as the first: a promising small trial that a bigger trial couldn't back up.
Resources
This entry is here for reference.
Research
- 1.A Randomized Exploratory Trial of an Alpha-7 Nicotinic Receptor Agonist (TC-5619) for Cognitive Enhancement in Schizophrenia
- 2.Phase 2 Trial of an Alpha-7 Nicotinic Receptor Agonist (TC-5619) in Negative and Cognitive Symptoms of Schizophrenia
2 listed here; entry last updated August 2026
Reviews
My notesprivate to this device
FAQ
What is the Groton Maze Learning Task?
It's a computerized spatial working-memory and learning test (part of the CogState battery) where patients learn and recall a hidden path through a grid; TC-5619 showed significant improvement on it in the exploratory trial.
Is TC-5619 related to nicotine or smoking-cessation drugs?
It targets the same alpha7 nicotinic receptor that nicotine partially activates, but it was purpose-built as a selective cognitive-enhancement candidate for schizophrenia, not as a smoking-cessation aid.
Limitations of the evidence
- confirmatory larger Phase II trial failed to replicate the cognitive or negative-symptom benefit
- development discontinued without reaching Phase III
Adverse effects
- results added to a broader pattern of alpha7 nicotinic agonists failing to scale up