NSI-189

NSI-189 (chemical name: (4-benzylpiperazin-1-yl)-[2-(3-methyl-butylamino)pyridin-3-yl]methanone, administered as the phosphate salt) is a synthetic small molecule classified as a nicotinamide-pyrazine hybrid. Its primary proposed mechanism is stimulation of neurogenesis in the adult hippocampus, a region implicated in mood regulation and episodic memory.

Preclinical work demonstrated that NSI-189 promotes proliferation of human hippocampus-derived neural stem cells in vitro and increases dentate gyrus neurogenesis in rodent models. The precise molecular binding target has not been fully established. NSI-189 does not appear to directly bind the extracellular domain of TrkB (the primary receptor for brain-derived neurotrophic factor), yet downstream TrkB and Akt signaling pathway activation has been documented in Angelman Syndrome and diabetic mouse models, indicating an indirect mechanism of neurotrophic enhancement.

Key downstream effects observed in animal models include: • Preservation of synaptic proteins synaptophysin and PSD95 in hippocampal tissue • Improved mitochondrial respiratory capacity in primary sensory neurons • Protection of hippocampal CA1 and dentate gyrus volume against diabetes-related atrophy

NSI-189 does not inhibit serotonin, norepinephrine, or dopamine reuptake, distinguishing it from all currently approved antidepressants. It was designed to address hippocampal atrophy, a structural feature associated with chronic major depressive disorder, rather than acutely modulating monoamine tone.

Human evidence consists of two sponsor-funded controlled trials, both in major depressive disorder (MDD) and published in Molecular Psychiatry.

The Phase 1b trial enrolled 24 inpatients with MDD, assigning participants in three sequential cohorts to 40 mg orally once, twice, or three times daily (up to 120 mg/day) or placebo for 28 days, with a 56-day post-treatment follow-up. The primary safety objective was met with no serious adverse events. Self-rated symptom scales showed preliminary efficacy signals that persisted through the post-treatment follow-up period. Structural MRI suggested a possible increase in hippocampal volume in treated participants, but the n=24 sample precludes firm conclusions.

The Phase 2 trial (NCT02695472; Papakostas et al., Molecular Psychiatry 2020) randomized 220 outpatients with MDD to NSI-189 40 mg/day, 80 mg/day, or placebo for 12 weeks using a sequential parallel comparison design. The primary endpoint (MADRS score reduction) was not met at either dose (40 mg: pooled mean difference -1.8, p=0.22; 80 mg: -1.4, p=0.34). The Hamilton Depression Rating Scale was similarly non-significant. However, the 40 mg dose reached significance on three secondary patient-rated measures: Symptoms of Depression Questionnaire (p=0.04), Cognitive and Physical Functioning Questionnaire (p=0.03), and QIDS-SR in Stage 2 (p=0.04). CogScreen cognitive testing showed significant improvements in executive function and delayed memory recall at 40 mg (Cohen's d 0.12-1.12). Notably, the 80 mg dose consistently underperformed the 40 mg dose, a dose-response reversal that has not been explained.

Preclinical evidence spans diabetic mouse models, Angelman Syndrome mice, a 5xFAD Alzheimer's model, and a rat stroke model, all showing neurogenic or neuroprotective effects. No Phase 3 trials have been registered as of 2026; Neuralstem's clinical development program appears discontinued. NSI-189 has not been approved by any regulatory authority for any indication.

Typical dosage: Research protocols vary (research).

In the Phase 1b trial, three escalating oral dose levels were tested: 40 mg once daily, 40 mg twice daily (80 mg/day total), and 40 mg three times daily (120 mg/day total), all for 28 days. The Phase 2 trial used fixed oral doses of 40 mg once daily and 80 mg once daily for 12 weeks. The 40 mg once-daily dose showed the most favorable efficacy profile; the 80 mg arm performed worse on both primary and secondary endpoints in the Phase 2 data. The estimated plasma elimination half-life of NSI-189 phosphate is approximately 17.4 to 20.5 hours, pharmacokinetically consistent with once-daily oral administration.

Self-experimenter communities (anecdotal only) most commonly reference 40 to 80 mg per day orally, mirroring Phase 2 trial doses. Some individuals describe beginning at 20 mg daily and titrating upward over one to two weeks to assess tolerability before increasing to 40 mg. Anecdotally reported cycle durations range from four weeks to several months, but no controlled evidence supports any specific cycle length or rotation protocol.

NSI-189 is not approved by any regulatory authority. No established therapeutic dose exists outside the research setting. All dosing information above reflects clinical trial parameters or informal, uncontrolled community reports only. This content is for educational purposes and does not constitute medical advice. Consult a qualified healthcare professional before considering any investigational compound.

No compound-specific stability data has been identified for this peptide. The general lyophilized-peptide handling framework applies — see Storage & handling for temperature, reconstitution diluent, and beyond-use dating principles.

No peer-reviewed or controlled studies have evaluated NSI-189 in combination with any other compound in humans. All reported combination practices are anecdotal and should not be treated as evidence-based.

Community reports describe pairing NSI-189 with noopept or piracetam-class compounds, with the theoretical rationale that NSI-189 supports hippocampal neurogenesis while racetam compounds modulate AMPA receptor sensitivity. This mechanistic pairing is entirely speculative. Other anecdotal accounts mention concurrent use of modafinil for wakefulness, or choline precursors such as alpha-GPC or CDP-choline to offset reported cognitive blunting. A small number of self-experimenters report pairing with standard antidepressants, though the interaction profile is completely unknown and the rationale is not supported by trial data.

No human safety data exists for NSI-189 in any combined regimen, and no pharmacokinetic or pharmacodynamic interaction studies have been conducted.

NSI-189 is not currently FDA-approved for any indication. It is generally classified as a research compound. Regulatory status varies by country.

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Reported side effects: Experimental. Side effects under investigation

Across the Phase 1b and Phase 2 clinical trials, covering oral exposures of up to 120 mg/day for up to 12 weeks, no serious adverse events were recorded. A noteworthy finding in the Phase 2 trial was that discontinuation due to intolerance was lower in both active arms than in the placebo group (placebo 18.9%, 40 mg arm 9.1%, 80 mg arm 2.3%; p=0.013), suggesting tolerability was not a limiting factor. Treatment-emergent adverse events in controlled studies included headache, dizziness, somnolence, and nausea at rates not substantially exceeding placebo. The Phase 1b trial documented EEG changes, primarily increased high-frequency alpha-wave activity, in treated participants; the clinical significance of this finding remains unclear.

Anecdotal community reports describe a wider array of adverse effects not well-characterized in the controlled trial data: anxiety, irritability, emotional blunting or flat affect, insomnia, paresthesia, and gastrointestinal upset. Some users report initial benefits followed by diminishing effects over weeks. These reports are uncontrolled and subject to significant confounding.

Critical safety limitations apply. The longest controlled human exposure was 12 weeks, and no long-term safety data exist. The consequences of chronically stimulating hippocampal neurogenesis in humans are unknown. No established drug-drug interaction profiles, formal contraindications, or pregnancy or lactation safety data have been published. When sold as a research chemical, NSI-189 is not subject to pharmaceutical-grade quality control or regulatory purity standards.