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Cerlapirdine was Pfizer's 2010s-era entry into the crowded field of 5-HT6 receptor antagonists chasing Alzheimer's disease, following the same mechanistic bet as idalopirdine and intepirdine: blocking 5-HT6 was thought to indirectly boost cortical acetylcholine and glutamate release and improve cognition. Pfizer ran a Phase II trial specifically in mild-to-moderate Alzheimer's patients who had existing neuropsychiatric symptoms while already stable on donepezil, a narrower bet aimed at the behavioral side of dementia rather than memory alone. The trial, published in 2018, did not separate cerlapirdine from placebo, closing out Pfizer's 5-HT6 program alongside the broader failure of the entire drug class across multiple companies in the same period.
- selective 5-HT6 receptor blockade with characterized CNS receptor occupancy in humans
- targeted neuropsychiatric symptoms of dementia specifically, not just memory
- well-characterized metabolism and drug interaction profile from Pfizer's clinical pharmacology work
- Pfizer aimed cerlapirdine's pivotal trial specifically at Alzheimer's patients with agitation and psychiatric symptoms, not just memory loss, betting the 5-HT6 mechanism would help the behavioral side of the disease. It didn't beat placebo either way.
Mechanism
Cerlapirdine is a selective 5-HT6 receptor , designed to indirectly enhance cortical and hippocampal and release by blocking 5-HT6-mediated inhibitory tone.
Safetyrisks and cautions, not medical advice
Adverse events landed at 46 percent on cerlapirdine against 45 percent on placebo across 186 randomised patients, and serious events at 5.5 percent against 3.2 percent, which is about as close to no difference as a trial this size can show. Nothing in the twelve weeks of safety data explains why it failed; the study was halted for futility rather than for harm. One death occurred in the treatment arm, a traffic accident during a washout period off active drug. Exposure beyond three months has never been studied in anyone.
History
Developed by Pfizer in the 2010s; tested in a Phase II trial in mild-to-moderate Alzheimer's disease patients with neuropsychiatric symptoms on stable donepezil, published in 2018 as a negative result.
Subjective profileweighing the evidence above
A well-run trial for a mechanism the entire 5-HT6 antagonist class failed to validate in Alzheimer's disease.
Resources
This entry is here for reference.
Research
- 2018first citedA Phase 2 clinical trial of PF-05212377 (SAM-760) in subjects with mild to moderate Alzheimer's…
- 2023most recentProgress in Investigational Agents Targeting Serotonin-6 Receptors for the Treatment of Brain D…
- 1.A Phase 2 clinical trial of PF-05212377 (SAM-760) in subjects with mild to moderate Alzheimer's disease with existing neuropsychiatric symptoms on a stable daily dose of donepezil
- 2.Metabolism of a 5HT(6) Antagonist, 2-Methyl-1-(Phenylsulfonyl)-4-(Piperazin-1-yl)-1H-Benzo[d]imidazole (SAM-760): Impact of Sulfonamide Metabolism on Diminution of a Ketoconazole-Mediated Clinical Drug-Drug Interaction
- 3.Progress in Investigational Agents Targeting Serotonin-6 Receptors for the Treatment of Brain Disorders
3 listed here; entry last updated July 2026
Reviews
My notesprivate to this device
FAQ
How is cerlapirdine different from idalopirdine or masupirdine?
All three are 5-HT6 receptor antagonists studied for Alzheimer's disease cognition in roughly the same era, from different companies (Pfizer, Lundbeck, and Suven/Harmony respectively). All three ultimately failed to show clear efficacy in late-stage trials.
Why was cerlapirdine tested alongside donepezil?
The trial design added cerlapirdine on top of a stable donepezil dose in patients with neuropsychiatric symptoms, testing whether 5-HT6 blockade could help the behavioral/psychiatric side of Alzheimer's beyond what a cholinesterase inhibitor alone provides.
Limitations of the evidence
- did not separate from placebo on its primary neuropsychiatric/cognitive endpoints
Notes and cautions
- P-glycoprotein substrate status limited and complicated CNS exposure in some patients