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T-817MA, later given the generic name edonerpic maleate, was developed by Toyama Chemical (subsequently absorbed into Fujifilm's pharmaceutical division) as a neurotrophic and neuroprotective small molecule aimed squarely at Alzheimer's disease, but built on a different premise than amyloid-clearing antibodies: promote neurite outgrowth and protect synapses from amyloid-beta toxicity directly. It advanced through multiple Phase II trials in Japan, the US and Europe, including a joint program with the Alzheimer's Disease Cooperative Study, and produced a real biomarker signal, dose-dependent drops in cerebrospinal fluid tau. That biomarker success never translated into a clinical cognitive benefit large enough to justify a Phase III program, and the compound was shelved, joining the long list of tau- and neuroprotection-targeted Alzheimer's candidates that moved the numbers without moving the patient.
- promoted neurite outgrowth in preclinical neuronal models
- protected against amyloid-beta-induced neurotoxicity in lab studies
- restored parvalbumin-positive GABAergic neuron deficits in a schizophrenia-relevant animal model
- produced statistically significant dose-dependent reductions in CSF tau in a Phase II trial
- promotes neurite outgrowth rather than simply clearing amyloid plaques
- protects against amyloid-beta-induced synaptic dysfunction in preclinical models
- supported microglial amyloid-beta clearance in cell-based experiments
- T-817MA's real molecular target, the microtubule-regulating protein CRMP2, was only nailed down in published mechanism papers years after its Phase II Alzheimer's trial had already failed and ended the program.
- T-817MA showed statistically significant, dose-dependent drops in cerebrospinal fluid tau in its Phase II Alzheimer's trial, one of the clearer biomarker signals in that trial's history.
- It was studied jointly with the US Alzheimer's Disease Cooperative Study (ADCS), a rare case of a Japanese-developed CNS candidate running trials through a major American academic consortium.
Mechanism
Neurotrophic and neuroprotective small molecule that promotes neurite outgrowth and protects synapses against oligomeric amyloid-beta-induced disruption of ; reduces phosphorylated and total tau in cerebrospinal fluid and promotes microglial phagocytosis of amyloid-beta in cell models.
Safetyrisks and cautions, not medical advice
Gastrointestinal side effects were real enough to roughly triple the dropout rate in the largest trial. Over 52 weeks in 482 patients with mild to moderate Alzheimer's, 4.4 percent on placebo stopped for adverse events against 13.9 and 14.6 percent on the two edonerpic doses, with diarrhoea and vomiting the most frequent events and appearing early. The investigators' own summary was that it looked safe and tolerable while showing no evidence of a clinical effect. Exposure otherwise tops out at about a year, all of it in older adults with dementia, so nothing is established for healthy or younger people.
History
Discovered by Toyama Chemical (Japan); advanced through Phase II trials in Japan, the US (with the Alzheimer's Disease Cooperative Study, NCT00663936 and NCT02079909) and Europe for mild-to-moderate Alzheimer's disease; showed dose-dependent tau biomarker changes but failed to demonstrate sufficient clinical cognitive benefit and was not advanced to Phase III.
Subjective profileweighing the evidence above
A genuine biomarker success and a genuine clinical-benefit failure, the kind of Alzheimer's candidate that moves tau numbers in the right direction without moving cognition enough to matter.
Resources
This entry is here for reference.
Research
- 2005first citedA novel neurotrophic agent, T-817MA [1-{3-[2-(1-benzothiophen-5-yl) ethoxy] propyl}-3-azetidino…
- 2019most recentNovel synaptic plasticity enhancer drug to augment functional recovery with rehabilitation
- 1.A novel neurotrophic agent, T-817MA [1-{3-[2-(1-benzothiophen-5-yl) ethoxy] propyl}-3-azetidinol maleate], attenuates amyloid-beta-induced neurotoxicity and promotes neurite outgrowth in rat cultured central nervous system neurons.
- 2.T-817MA, a novel neurotrophic compound, ameliorates phencyclidine-induced disruption of sensorimotor gating
- 3.Novel synaptic plasticity enhancer drug to augment functional recovery with rehabilitation
- 4.Effects of the neurotrophic agent T-817MA on oligomeric amyloid-β-induced deficits in long-term potentiation in the hippocampal CA1 subfield.
- 5.T-817MA, a neuroprotective agent, attenuates the motor and cognitive impairments associated with neuronal degeneration in P301L tau transgenic mice
- 6.Pharmacological properties of T-817MA, a novel neurotrophic agent, for treatment of Alzheimer's disease
6 listed here; entry last updated August 2026
Reviews
My notesprivate to this device
FAQ
Is edonerpic maleate the same drug as T-817MA?
Yes, edonerpic maleate is the later-assigned name for the same compound originally studied as T-817MA.
Why did T-817MA fail its Alzheimer's trial if the preclinical data looked strong?
The Phase II trial did not separate from placebo on cognitive measures, a common outcome for Alzheimer's candidates that show promise in animal models but face a much harder bar in heterogeneous human disease populations.
Did T-817MA ever get approved?
No. It completed Phase II trials for mild-to-moderate Alzheimer's disease in Japan, the US and Europe, showed biomarker changes but not enough clinical benefit, and was not advanced to Phase III or approved.
How is it different from amyloid-clearing drugs like aducanumab?
T-817MA does not target amyloid plaques directly; it aims to protect synapses and promote neurite growth in the presence of amyloid-beta toxicity, and separately reduces tau markers, a mechanistically distinct approach.
Limitations of the evidence
- Phase II Alzheimer's trial did not show significant cognitive improvement over placebo
- no approved human safety/side-effect profile since it never reached market
- did not demonstrate sufficient clinical cognitive benefit to advance to Phase III
- never approved or marketed anywhere
- human safety data exists only from completed Phase II trials, not long-term use
- development appears discontinued as of the mid-2010s