NSI-189

A hippocampal-neurogenesis drug candidate that ran real depression trials, missed its primary endpoints, and migrated to research-chem shelves on the strength of its mechanism story and secondary-measure signals.

NSI-189 was developed as an antidepressant on an unusual premise: rather than acting on serotonin or noradrenaline signalling like conventional antidepressants, it was reported to stimulate neurogenesis — the growth of new neurons in the hippocampus — and to increase hippocampal volume. That framing is why it retained a following among people interested in cognition after its clinical programme did not succeed.

Phase 1 and 2 trials exist and are published — the honest reading is a failed program, not a suppressed success: the Phase 2 trial missed its primary endpoint, and secondary findings were exploratory without a consistent dose-response. The neurogenesis mechanism is validated in animals, unproven as a human therapeutic lever.

• It has genuine human trial data, which distinguishes it from most research chemicals here. A phase II study in major depressive disorder did NOT meet its primary endpoint.
• Some secondary and patient-reported measures moved in that trial, which is the basis of the continued interest — secondary endpoints in a trial that missed its primary are hypothesis-generating, not evidence of efficacy.
• NONE SHOWN for cognitive enhancement in healthy people. It was never studied for that.
• Development did not proceed to approval. It is not an approved medicine anywhere.
• The neurogenesis mechanism itself rests on preclinical work; increased hippocampal volume has not been established as a clinical benefit in people.

Orally active, with human pharmacokinetics characterised to some degree through the abandoned trial programme — more than most compounds in this section can claim. What is sold is research-chemical supply of unverified identity and purity rather than clinical-grade material.

The trial record is short-duration; long-term use has no data. Trial-reported effects were mild (headache, dry mouth), but self-treating mood with an antidepressant-class compound outside any care context — especially alongside other serotonergic or stimulant compounds — is unmonitored psychiatry.

• Anyone self-treating depression with it instead of seeking treatment that has evidence and monitoring behind it
• Anyone taking psychiatric medication, without their prescriber
• Anyone pregnant or breastfeeding
• Anyone unwilling to accept unverified research-chemical supply

• No characterised human interaction profile exists outside the trial programme.
• Any psychiatric medication — combining an unstudied compound with prescribed treatment is a conversation for the prescriber, not a self-directed experiment.

• There is no established monitoring for an unapproved compound outside a trial setting.
• Mood, honestly and preferably with someone else's input, since this was developed as an antidepressant and anyone self-treating depression with it is doing so without any of the safeguards a trial or a prescriber provides.
• Anyone using it for depression is the person this entry is most concerned about: depression has treatments with real evidence and real monitoring, and a compound that missed its primary endpoint is not one of them.

No withdrawal syndrome is described. The concern worth naming is different: anyone who has been using it to manage depression is stopping something that was never shown to work, and the underlying depression is still there. That is a reason to see someone rather than to try the next compound.

US: unapproved, unscheduled; research-chemical market.

Papers about this compound, not proof of the claims above. A title says what was studied, which is sometimes a negative result or a different question entirely.

• A phase 2, double-blind, placebo-controlled study of NSI-189 phosphate, a neurogenic compound, among outpatients with major depressive disorder
  Mol Psychiatry, 2020
• A Phase 1B, randomized, double blind, placebo controlled, multiple-dose escalation study of NSI-189 phosphate, a neurogenic compound, in depressed patients
  Mol Psychiatry, 2016
• NSI-189 phosphate, a novel neurogenic compound, selectively benefits moderately depressed patients: A post-hoc analysis of a phase 2 study of major depressive disorder
  Ann Clin Psychiatry, 2020

• The neurogenic compound, NSI-189 phosphate: a novel multi-domain treatment capable of pro-cognitive and antidepressant effectsExpert Opin Investig Drugs · 2017
• NSI-189 phosphate, a novel neurogenic compound, selectively benefits moderately depressed patients: A post-hoc analysis of a phase 2 study of major depressive disorderAnn Clin Psychiatry · 2020
• NSI-189, a small molecule with neurogenic properties, exerts behavioral, and neurostructural benefits in stroke ratsJ Cell Physiol · 2017
• Enhancement of Mitochondrial Function by the Neurogenic Molecule NSI-189 Accompanies Reversal of Peripheral Neuropathy and Memory Impairment in a Rat Model of Type 2 DiabetesJ Diabetes Res · 2022
• Enhancement of synaptic plasticity and reversal of impairments in motor and cognitive functions in a mouse model of Angelman Syndrome by a small neurogenic molecule, NSI-189Neuropharmacology · 2019
• Amelioration of Both Central and Peripheral Neuropathy in Mouse Models of Type 1 and Type 2 Diabetes by the Neurogenic Molecule NSI-189Diabetes · 2019
• A phase 2, double-blind, placebo-controlled study of NSI-189 phosphate, a neurogenic compound, among outpatients with major depressive disorderMol Psychiatry · 2020
• Remediation of Radiation-Induced Cognitive Dysfunction through Oral Administration of the Neuroprotective Compound NSI-189Radiat Res · 2018
• A Phase 1B, randomized, double blind, placebo controlled, multiple-dose escalation study of NSI-189 phosphate, a neurogenic compound, in depressed patientsMol Psychiatry · 2016
• A Phase 1B, randomized, double blind, placebo controlled, multiple-dose escalation study of NSI-189 phosphate, a neurogenic compound, in depressed patientsMol Psychiatry · 2016
• Neuroprotective efficacy of P7C3 compounds in primate hippocampusTransl Psychiatry · 2018
• Mitochondrial dysfunction following repeated administration of alprazolam causes attenuation of hippocampus-dependent memory consolidation in miceAging (Albany NY) · 2023