LY451646
ampa pam · antidepressant-like effects in forced swim and tail suspension tests class / ampa pamspec sheet6 rows
LY451646 was one of Eli Lilly's AMPA receptor potentiators explored as a fundamentally different kind of antidepressant, one that worked through fast glutamatergic signaling rather than the serotonin/norepinephrine route every SSRI and SNRI takes. It behaved like an antidepressant in classic rodent despair tests, and chronic dosing drove roughly a 45 percent jump in hippocampal progenitor cell proliferation along with increased BDNF and TrkB expression, the same neuroplasticity signature later associated with ketamine. Development stalled in the mid-2000s; LY451646 and its close relative LY451395 both showed intrinsic partial-agonist activity at high concentrations that raised seizure risk, a liability that appears to have kept it (and much of Lilly's ampakine series) out of the clinic. In hindsight it was chasing the same glutamate-antidepressant idea that ketamine would validate roughly a decade later, just through a different receptor.
- Antidepressant-like activity in standard rodent behavioral despair models
- Boosted hippocampal neurogenesis in chronic dosing studies
- Increased BDNF/TrkB signaling, a marker linked to plasticity-based antidepressant effects
- Worked through a mechanism independent of monoamine reuptake
- Intrinsic agonist activity at high concentrations raised epileptogenic concern
- LY451646 increased hippocampal cell proliferation by about 45 percent in chronic rodent dosing, one of the largest neurogenesis effects reported for any ampakine.
- Its close sibling compound LY451395 shared the same epileptogenic liability, suggesting it was a class-wide problem for Lilly's high-potency AMPA potentiators.
Mechanism
Positive modulator of receptors that slows receptor desensitization; at higher concentrations it also shows some intrinsic activity, a property linked to epileptogenic risk.
Safetyrisks and cautions, not medical advice
Seizure risk is the specific thing on this compound's record. Unlike a clean positive modulator, LY451646 opens AMPA receptors on its own at higher concentrations, and a later Takeda programme benchmarked its own candidate against it on exactly that point, reporting lower seizure risk and a less bell-shaped dose response than LY451646 in both rodents and monkeys. No person has been dosed in any published trial, so nobody can quote a tolerable dose, and where that margin sits in a human brain is unknown.
History
Characterized in Lilly's rodent hippocampal studies published 2002-2003; no evidence of it advancing into human clinical trials was found; effectively shelved as a research tool by the mid-2000s.
Subjective profileweighing the evidence above
A glutamate-antidepressant idea that was scientifically ahead of its time and got stopped by its own seizure risk before anyone could prove it in people.
Resources
This entry is here for reference.
Research
- 1.Chronic AMPA receptor potentiator (LY451646) treatment increases cell proliferation in adult rat hippocampus
- 2.An AMPA receptor potentiator modulates hippocampal expression of BDNF: an in vivo study
2 listed here; entry last updated August 2026
Reviews
My notesprivate to this device
FAQ
Did LY451646 ever reach human trials?
No completed human trial data has been published; it appears to have stayed a preclinical rodent research compound before Lilly moved on from it.
Why is LY451646 relevant to today's ketamine-era antidepressants?
It hit the same BDNF/neuroplasticity pathway that made ketamine famous as a fast-acting antidepressant, just via AMPA receptor potentiation instead of NMDA blockade, years before that mechanism became mainstream psychiatry.
Limitations of the evidence
- No published human safety or tolerability data
- Development discontinued before any confirmed clinical use
Adverse effects
- Intrinsic agonist activity at high concentrations raised epileptogenic concern