Zalsupindole — Safety, Research, Risks & Legal Status

Not medical advice. Zalsupindole is discussed here for informational and harm-reduction purposes only. We do not endorse use, and any dosing context is informational, not a protocol.

Also known as	DLX-001; AAZ-A-154
Category	Research Chemical
Chemical class	Substituted isotryptamine; (R)-5-methoxy-N,N-dimethyl-alpha-methylisotryptamine
Developer	Delix Therapeutics, Inc. (academic origin: Olson Lab, UC Davis)
Development codes	DLX-001, AAZ-A-154
Current clinical stage	Phase 2 (FDA IND cleared late 2025); Phase 1b MDD cohort completed
Primary receptor targets	5-HT2A/C partial agonist; 5-HT2B antagonist
Key distinguishing feature	Non-hallucinogenic neuroplastogen - no psychotomimetic effects observed in 120+ Phase 1 subjects
US legal status	Investigational drug in the United States. Not currently listed on DEA controlled substance schedules. Clinical use is restricted to FDA-cleared Investigational New Drug (IND) trials. Not approved for any therapeutic indication. Not available for human consumption outside of regulated clinical research.

What is Zalsupindole?

Zalsupindole is an orally active substituted isotryptamine derivative developed as a non-hallucinogenic neuroplastogen - a compound designed to promote structural and functional neuroplasticity through serotonergic mechanisms without producing the hallucinogenic, dissociative, or psychotomimetic effects associated with classical psychedelics or ketamine. It was first synthesized in 2019 in David E. Olson's laboratory at UC Davis and is currently under clinical development by Delix Therapeutics, Inc. As of late 2025 it has completed Phase 1b in a major depressive disorder cohort and received FDA clearance to proceed to Phase 2.

How it works

Zalsupindole acts as a low-potency partial agonist at 5-HT2A and 5-HT2C serotonin receptors and as an antagonist at 5-HT2B receptors. This receptor profile is proposed to engage neuroplasticity-promoting serotonergic signaling while avoiding the full agonism at 5-HT2A associated with hallucinogenesis. In preclinical models, it increases dendritic spine density in the prefrontal cortex and promotes structural and functional neuroplasticity at a magnitude described as comparable to or exceeding that of ketamine, psilocybin, and DMT - without observed psychotomimetic effects. The precise mechanism underlying the dissociation between neuroplastogenic activity and hallucinogenic liability at this receptor profile remains an active area of investigation.

Background & history

Zalsupindole was first synthesized in 2019 in the Olson laboratory at UC Davis as part of a broader program to identify "psychoplastogens" - compounds that promote neuroplasticity through psychedelic-adjacent mechanisms without the perceptual and safety liabilities of classical psychedelics. Initial preclinical findings were published beginning in 2021 in ACS Chemical Neuroscience, demonstrating cortical neuritogenesis in vitro and dendritic spine density changes in vivo. Delix Therapeutics advanced the compound into human trials; Phase 1 enrolled over 120 subjects across a dose range of approximately 2-360 mg oral. Phase 1b in a major depressive disorder cohort (n=18) was completed in 2025, with a positive efficacy signal announced in October 2025. FDA IND clearance for a Phase 2 trial - including a notable at-home administration arm - was announced concurrently. The compound remains early-stage and no regulatory approval for any indication has been sought or granted.

What the research says

Human clinical evidence is limited to Phase 1 safety/tolerability data and a small Phase 1b efficacy signal. Phase 1 established tolerability across doses up to 360 mg oral in over 120 subjects, with no serious adverse events reported. Phase 1b (n=18, MDD) reported a positive efficacy signal as of October 2025 - this cohort is too small to draw efficacy conclusions and no peer-reviewed Phase 1b publication appears to have been indexed at the time of this entry. Phase 2 design has received FDA clearance; trial completion and results are pending. Preclinical evidence in rodent models demonstrates neuroplasticity effects (dendritic spine density, neuritogenesis) with published data in ACS Chemical Neuroscience. No controlled human efficacy data yet exists. The absence of hallucinogenic effects in Phase 1 subjects is a notable and consistent finding across all reported human exposure, though the mechanistic explanation remains incompletely characterized.

Reported effects

Promoted neuroplasticity in preclinical models (dendritic spine density, cortical neuritogenesis) - not yet confirmed in human imaging studies
No hallucinogenic or dissociative effects reported across 120+ human subjects in Phase 1 - a distinguishing characteristic relative to classical psychedelics
Preliminary antidepressant signal in Phase 1b MDD cohort (n=18) - very early, not confirmatory
Rapid onset of symptom reduction reported in Phase 1b depression cohort - mechanism and durability unclear at this stage
Dose-dependent mild adverse effects: nausea, headache, dizziness - all described as self-resolving
Serotonergic activity (5-HT2A/C partial agonism) - functional downstream effects in humans remain under characterization

Dosing & administration (informational)

Phase 1 dose escalation studied oral doses ranging from approximately 2 mg to 360 mg; this range is reported as generally well-tolerated in that trial context. These figures are provided for informational and scientific reference only - they do not constitute dosing guidance, a protocol, or a recommendation of any kind. Zalsupindole is an unapproved investigational drug; no safe or effective dose has been established outside of the clinical trial setting. Anyone with questions about participation in trials or therapeutic options should consult a licensed clinician.

This is general research/context information, not medical advice or a recommended protocol.

Safety & side effects

Mild adverse effects reported in Phase 1: nausea, headache, dizziness - dose-dependent, self-limiting, no serious adverse events through 360 mg oral
No hallucinogenic, dissociative, or psychotomimetic effects observed in over 120 Phase 1 subjects - this is a key differentiator but long-term data are absent
5-HT2B antagonism may be relevant to cardiac safety (5-HT2B agonism is associated with valvulopathy in drugs such as fenfluramine) - chronic exposure safety has not been established in humans
Phase 2 trial will provide longer-duration and larger-cohort safety data; current human safety dataset is limited to short-term exposure
No data on drug-drug interactions, pregnancy, hepatic/renal impairment, or long-term neurological effects in humans
As with all early-phase investigational compounds, the full adverse effect profile is not yet characterized - unknown risks exist beyond those detected in small early trials

Drug & supplement interactions

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Who should avoid it

Concurrent use with monoamine oxidase inhibitors (theoretical serotonin toxicity risk)
Concurrent use with other serotonergic drugs without medical supervision
Use outside of regulated clinical trial settings - compound is unapproved and uncharacterized for general human use
Any gray-market or unverified sourcing - identity and purity cannot be confirmed outside clinical supply chains

How it is commonly combined

No data. Zalsupindole has not been studied in combination with other compounds in human trials. Stacking information is not available and combinations should not be extrapolated from the preclinical or Phase 1 data.

Legal & regulatory. Investigational drug in the United States. Not currently listed on DEA controlled substance schedules. Clinical use is restricted to FDA-cleared Investigational New Drug (IND) trials. Not approved for any therapeutic indication. Not available for human consumption outside of regulated clinical research.

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Frequently asked questions

What makes zalsupindole different from classical psychedelics like psilocybin?

Structurally, zalsupindole is an isotryptamine derivative engineered to act as a low-potency partial agonist - rather than a full agonist - at 5-HT2A receptors, and to add 5-HT2B antagonism. In Phase 1, no hallucinogenic or dissociative effects were reported across 120+ subjects, in contrast to psilocybin and DMT which reliably produce perceptual distortion at neuroplasticity-relevant doses. Whether this pharmacological distinction fully explains the absence of hallucinogenesis, or whether other structural features contribute, is not yet resolved.

Is there human evidence that zalsupindole works for depression?

Only very preliminary data exist. A Phase 1b open-label cohort of 18 patients with major depressive disorder reported a positive efficacy signal as of October 2025. This sample size is far too small to establish efficacy, and no peer-reviewed publication of this data was available at the time of this entry. Phase 2 trials are required to generate controlled evidence. The preclinical neuroplasticity findings are robust but do not confirm antidepressant efficacy in humans.

Can I get zalsupindole outside of a clinical trial?

No. Zalsupindole is an unapproved investigational drug. It is not commercially available, not sold by any legitimate supplier, and has no established access pathway outside of Delix Therapeutics' clinical trials. Any material offered outside of that context cannot be verified and carries unknown risks.

What is the recommended dose of zalsupindole?

No dose has been established for any therapeutic use. Phase 1 explored a range from approximately 2 to 360 mg orally for safety characterization purposes. Providing or following a dosing protocol for zalsupindole is not appropriate outside of a supervised clinical trial. Consult a clinician or inquire about clinical trial participation if you have a medical interest.

Is zalsupindole a controlled substance?

As of the time of this entry, zalsupindole is not listed on DEA controlled substance schedules. It is classified as an investigational drug under FDA IND authorization. Regulatory status is subject to change as development progresses; it does not imply the compound is legal to possess or use outside of a clinical trial.

How does zalsupindole compare to ketamine for depression?

Direct comparative human data do not exist. In preclinical models, zalsupindole has been reported to promote neuroplasticity at a magnitude described as comparable to ketamine. The key proposed advantage is the absence of dissociative and hallucinogenic effects that require ketamine infusions to be administered in monitored clinical settings. Whether this translates to comparable or superior efficacy in humans is unanswered pending Phase 2 results.

References & further reading

PubMed: zalsupindole OR DLX-001 OR AAZ-A-154 (ACS Chemical Neuroscience, Olson lab, 2021 onward)
PubMed: psychoplastogen neuroplasticity non-hallucinogenic tryptamine Olson UC Davis
ClinicalTrials.gov: DLX-001 Delix Therapeutics depression Phase 2 (search Delix or DLX-001 for current NCT numbers)
ClinicalTrials.gov: zalsupindole neuroplastogen major depressive disorder
PubMed: isotryptamine 5-HT2A partial agonist dendritic spine plasticity depression