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Linopirdine took a completely different route to boosting acetylcholine than anything else in this collection; instead of blocking the enzyme that breaks ACh down, DuPont built it to block KCNQ2/KCNQ3 potassium channels, the so-called M-channel, which in turn triggers broad neurotransmitter release, acetylcholine included, across the brain. Preclinical work in the late 1980s looked strong enough that DuPont pushed it into Alzheimer's clinical trials, but the results in patients were equivocal; the drug needed high doses to meaningfully block the M-current, and those doses caused cholinergic overstimulation side effects like tremor. The program was ultimately discontinued, but linopirdine's real legacy is scientific rather than commercial, it became the founding tool compound for an entire generation of KCNQ channel research, directly enabling more selective descendants like XE-991 and eventually helping validate KCNQ as a target that led to the anticonvulsant retigabine.
- improved performance in rodent tests of learning and memory via cholinergic release enhancement
- distinct non-receptor mechanism (Kv7/M-current blockade) offering an alternative to agonist-based cholinergic drugs
- became a foundational pharmacology tool compound for studying M-current in neurons
- increased acetylcholine release in rat brain tissue and improved performance in animal learning and memory models
- highly selective in vitro for KCNQ2/KCNQ3 (M-current) channels over other voltage-dependent and calcium-activated potassium currents
- required high doses for meaningful M-current blockade, and those doses caused cholinergic hyperstimulation side effects including tremor in clinical testing
- Linopirdine's more selective chemical descendant, XE991, outlived the original drug by decades and is still a standard reagent in electrophysiology labs for blocking M-current.
- Linopirdine's most lasting contribution to medicine may be indirect, its research spurred more selective KCNQ-channel tool compounds and helped validate KCNQ as a drug target years before the anticonvulsant retigabine reached the market.
Mechanism
Blocks the M-current generated by neuronal KCNQ2/KCNQ3 potassium channels; this depolarizing effect increases the release of and other neurotransmitters from presynaptic terminals rather than inhibiting directly.
Dosingtypical ranges, not medical advice
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Safetyrisks and cautions, not medical advice
Headache was the one complaint that stood out in the Phase 1 work, which gave single doses of up to 55 mg to sixty-four healthy young and elderly men and found no clinically important change in vital signs, electrocardiograms, electroencephalograms or laboratory values. A 382-patient trial then ran 30 mg three times daily for six months in Alzheimer's disease without a tolerability problem surfacing in the published report; the drug simply did not work. Its half-life in people is short, often under an hour, and no long-term human exposure data exists.
History
Developed by DuPont in the late 1980s; entered Alzheimer's disease clinical trials but produced equivocal efficacy results linked to a narrow dose window between M-current blockade and cholinergic side effects, leading to discontinuation. It remains widely used today purely as a laboratory research tool.
Subjective profileweighing the evidence above
A mechanistically distinct Alzheimer's candidate whose lasting contribution ended up being lab-bench pharmacology rather than a clinic-ready drug.
Resources
This entry is here for reference.
Research
- 1994first citedLinopirdine (DuP 996) improves performance in several tests of learning and memory by modulatio…
- 2005most recent[3H]linopirdine binding to rat brain membranes is not relevant for M-channel interaction
- 1.Linopirdine (DuP 996) improves performance in several tests of learning and memory by modulation of cholinergic neurotransmission
- 2.[3H]linopirdine binding to rat brain membranes is not relevant for M-channel interaction
- 3.Selectivity of linopirdine (DuP 996), a neurotransmitter release enhancer, in blocking voltage-dependent and calcium-activated potassium currents in hippocampal neurons
3 listed here; entry last updated August 2026
Reviews
My notesprivate to this device
FAQ
Is linopirdine still used today?
Not as a drug candidate, but its more selective descendant, XE991, is still widely used in neuroscience labs as a standard tool for blocking M-current potassium channels in electrophysiology experiments.
How does linopirdine's mechanism differ from cholinesterase inhibitors like donepezil?
Cholinesterase inhibitors slow the breakdown of acetylcholine already released into the synapse. Linopirdine instead blocks Kv7/M-current potassium channels to increase how much acetylcholine gets released from nerve terminals in the first place.
Is linopirdine used for anything today?
It is not used clinically; it remains a standard laboratory research tool for studying KCNQ (M-current) potassium channel pharmacology in neuroscience labs.
How is linopirdine different from acetylcholinesterase inhibitors like donepezil?
It does not block the enzyme that breaks down acetylcholine at all; instead it blocks a potassium channel that, when blocked, promotes broader release of acetylcholine and other neurotransmitters from nerve terminals.
Limitations of the evidence
- narrow therapeutic window between neurotransmitter-release benefit and channel-blockade side effects
- not established as safe or effective enough in humans to reach approval
Adverse effects
- required high doses for meaningful M-current blockade, and those doses caused cholinergic hyperstimulation side effects including tremor in clinical testing