Nootropic Peptides: A Research Overview

Key Takeaways

• Superpower does not offer or prescribe any of the compounds profiled in this article. This is an educational resource only.
• Compounds covered: Semax, selank, P21, dihexa
• Goal area: Cognitive function and preclinical neuroprotection research
• Evidence range: Ranges from limited human neuroimaging studies (semax, selank) to animal-only data (P21, dihexa)
• Regulatory range: None of the four compounds is FDA-approved. Semax was removed from the FDA's Category 2 interim-review list on April 22, 2026. Selank has never been on the Category 1 positive list. Neither semax nor selank meets the statutory pathways for 503A bulk drug substance compounding. P21 and dihexa are research-only compounds with no human-use regulatory pathway.
• Key biomarkers for cognitive health: TSH, vitamin B12, IGF-1, hs-CRP, comprehensive metabolic panel
• As of April 2026: None of the compounds profiled in this article are FDA-approved for any cognitive indication, and there is no clearly lawful US pathway to obtain any of them for human use at this time.
• Bottom line: Evidence for all four compounds is preliminary; none have completed Phase 2 or Phase 3 human trials for cognitive endpoints in healthy adults.

Note on classification language: "Type A/B/C/D/E" is not an FDA classification system. This article uses plain-language FDA terminology (FDA-approved; Category 1/Category 2 bulk drug substance lists; research-only/RUO) instead.

Understanding Cognitive Enhancement: The Biology

Cognitive function in the neurological sense is not a single process. It encompasses several distinct domains: working memory (the temporary holding and manipulation of information), episodic memory (the encoding and retrieval of personal events), sustained attention, executive function (planning and decision-making), and processing speed. Each depends on overlapping but distinguishable neural circuits. Two systems are particularly relevant to the peptides discussed on this page.

The first is the neurotrophic signaling system, centered on brain-derived neurotrophic factor (BDNF) and its high-affinity receptor trkB. BDNF supports neuronal survival, promotes synaptogenesis (the formation of new synaptic connections), and is necessary for long-term potentiation — the electrophysiological basis of memory consolidation. BDNF levels decline with age, chronic stress, poor sleep, and certain metabolic conditions. Compounds that upregulate BDNF or mimic its downstream effects represent one mechanistic category within the neuropeptide research space.

The second system is monoaminergic neurotransmission — specifically the dopaminergic and serotonergic pathways that govern attention, motivation, and mood. Suboptimal dopaminergic signaling in the prefrontal cortex is associated with reduced working memory capacity. Anxiety, mediated partly through disrupted GABAergic tone, further impairs prefrontal function, which is why compounds with anxiolytic properties may show indirect cognitive effects in high-stress conditions.

A third and emerging system is the hepatocyte growth factor (HGF) and c-Met receptor axis, implicated in synaptogenesis and neuroplasticity. This pathway is the proposed target of dihexa and represents a distinct mechanistic category from the BDNF and monoamine systems.

Peptides are structurally well-suited to interact with these systems because their small size and high receptor selectivity allow targeted signaling — but blood-brain barrier penetration remains a pharmacological constraint for most. Intranasal delivery routes have been investigated for some neuropeptides precisely because this route bypasses hepatic first-pass metabolism and may facilitate central nervous system access.

Nootropic Peptides: A Quick Comparison

The following peptides have published evidence relevant to cognitive function and neuroprotection in preclinical models. They are listed by strength of available clinical evidence, from most-studied to least.

• Compound: Semax
  Proposed mechanism in preclinical models: ACTH(4-10) analog; has been reported to upregulate BDNF and trkB in hippocampus and basal forebrain, and to activate dopaminergic and serotonergic systems in rodents
  Evidence: Limited human studies (stroke recovery, neuroimaging in healthy subjects); no Phase 2 or Phase 3 RCT for cognitive use in healthy adults
  FDA status: Not FDA-approved for any indication. Removed from the FDA Category 2 interim-review list on April 22, 2026; not on Category 1 positive list; does not meet 503A bulk drug substance statutory pathways
  SP availability: Not available through Superpower
  Route in research reports: Intranasal spray
• Compound: Selank
  Proposed mechanism in preclinical models: Tuftsin analog; has been reported to modulate GABAergic neurotransmission and to upregulate BDNF in hippocampus and prefrontal cortex; evaluated in preclinical models for effects on GABAergic neurotransmission
  Evidence: Limited human neuroimaging data; anxiolytic-related evidence in clinical populations outside the US; no Phase 2 or Phase 3 RCT for healthy-adult cognitive use
  FDA status: Not FDA-approved for any indication. Not on Category 1 positive list; does not meet 503A bulk drug substance statutory pathways
  SP availability: Not available through Superpower
  Route in research reports: Intranasal spray
• Compound: P21
  Proposed mechanism in preclinical models: CNTF-derived tetrapeptide; has been reported to promote hippocampal neurogenesis, synaptic density, and BDNF expression in animal models
  Evidence: Animal studies only — no completed human clinical trials
  FDA status: Not FDA-approved for any medical use; research-only compound with no human-use regulatory pathway
  SP availability: Not available through Superpower or any licensed prescriber for this use
  Route in research reports: Subcutaneous injection (animal studies); human route and dosing not established
• Compound: Dihexa
  Proposed mechanism in preclinical models: Angiotensin IV analog; has been reported to activate the HGF/c-Met receptor system and to promote synaptogenesis in preclinical models
  Evidence: Animal studies only — no completed human clinical trials
  FDA status: Not FDA-approved for any medical use; research-only compound with no human-use regulatory pathway
  SP availability: Not available through Superpower or any licensed prescriber for this use
  Route in research reports: Oral and subcutaneous in animal studies; human pharmacokinetics not established

Compounds listed as 'research-only' have not completed the clinical trial process required for FDA approval. They are not legal to prescribe or sell for human use in the US. Some research-only compounds are sold as Research Use Only (RUO) reagents with labeling stating they are "not for human consumption." An RUO label does not confer any legal pathway for human use. FDA has repeatedly taken enforcement action against sellers of RUO-labeled compounds marketed to or purchased by consumers for self-administration, under the intended use doctrine (21 C.F.R. § 201.128). Buying and self-administering an RUO-labeled peptide is not a legal alternative to an approved drug or a compounded prescription. Their inclusion here is for educational context only.

Nootropic Peptides: Individual Profiles

Each compound below has a distinct mechanism and a distinct evidence base. Cross-compound comparisons are not meaningful because the research has used different models, different populations, different endpoints, and different doses.

Semax

Semax is a synthetic heptapeptide analog of the ACTH(4-10) sequence, originally developed in the Soviet Union by the Moscow State University peptide chemistry group. Its proposed mechanism in preclinical models centers on the neurotrophic pathway: Dolotov and colleagues published work in Brain Research in 2006 reporting semax regulation of BDNF/trkB in the rat hippocampus following intranasal delivery. A companion study by Dolotov and colleagues in the Journal of Neurochemistry in 2006 linked semax BDNF synthesis in rat astrocytes, suggesting dual neuronal and glial mechanisms. Tsai, writing in Medical Hypotheses in 2007, proposed semax ACTH(4-10) analogue for ADHD [hypothesis/review, not primary animal-model data]. Beyond BDNF, Eremin and colleagues, publishing in Neurochemical Research in 2005, reported evidence that semax activates dopaminergic and serotonergic systems in rodents — a mechanism that research literature has associated with attentional effects and that distinguishes it from classical stimulants, which act primarily through catecholamine release rather than neurotrophic modulation.

Manchenko and colleagues, publishing in Rossiiskii Fiziologicheskii Zhurnal Imeni I.M. Sechenova in 2010, reported nootropic and analgesic effects of semax across routes of administration in a rat model — a preclinical finding, not data from healthy adults pursuing cognitive enhancement. Russian clinical-setting stroke-recovery reports on semax exist in the non-English literature but are typically observational or small-cohort reports rather than FDA-standard adequate and well-controlled trials, and none are indexed here as primary citations. Throughout this article, "Russian clinical experience" refers to observational, clinical-setting, and small-cohort reports associated with semax's and selank's foreign regulatory registrations — not to FDA-standard adequate and well-controlled trials under 21 C.F.R. § 314.126. Neuroimaging evidence in healthy subjects was provided by Panikratova and colleagues, whose 2020 paper in Doklady Biological Sciences used functional connectomics to document that semax and selank affect resting-state networks in ways consistent with their proposed mechanisms. [Limited human neuroimaging data; no Phase 2 or Phase 3 RCT for healthy-adult cognitive use] Semax is not FDA-approved for any indication. Its use for cognitive enhancement has not been approved by the FDA, and the safety and efficacy for this use have not been established through adequate and well-controlled clinical trials. On April 22, 2026, the FDA removed semax from the Category 2 list of bulk drug substances under evaluation for 503A compounding; semax is not on the FDA Category 1 positive list, is not the subject of a USP/NF monograph, and is not a component of any FDA-approved drug. As a result, 503A compounding of semax from bulk is not currently a clearly lawful pathway in the United States. Semax is not available through Superpower.

Selank

Selank is a synthetic analog of the endogenous immunopeptide tuftsin (Thr-Lys-Pro-Arg), extended to a heptapeptide and originally developed in Russia for anxiolytic applications. Its primary proposed cognitive-related mechanism in preclinical models operates through GABAergic modulation: Filatova and colleagues, publishing in Frontiers in Pharmacology in 2017, reported that selank affects GABAergic-related genes in IMR-32 cells, and a 2016 paper by Volkova and colleagues in the same journal showed GABAergic gene regulation more broadly (Kolomin T is shared senior author across these studies). Vyunova and colleagues, reviewing the molecular aspects of selank's biological activity in Protein and Peptide Letters in 2018 (PMID 30255741), characterized selank's anxiolytic mechanisms in detail. In preclinical models, selank has been reported to have cognitive-related effects that may be mediated partly through BDNF: Kolik and colleagues, publishing in the Bulletin of Experimental Biology and Medicine in 2019, reported that selank attenuated ethanol-induced memory impairment through BDNF-related content changes in the hippocampus and prefrontal cortex.

Zozulia and colleagues, writing in Zhurnal Nevrologii i Psikhiatrii Imeni S.S. Korsakova in 2008, selank in generalized anxiety disorder therapy. The anxiolytic-related signal has been discussed in relation to cognitive performance, as GABAergic tone in the prefrontal cortex is associated with working memory capacity under stress conditions, and Kasian and colleagues, publishing in Behavioural Neurology in 2017, showed that selank enhances diazepam's anxiolytic effect under unpredictable chronic mild stress, indicating a pharmacodynamic interaction with GABAergic signaling, which has implications for concurrent GABAergic drug use (see Safety Considerations). The neuroimaging study by Panikratova and colleagues in 2020 also documented selank's whole-brain network effects alongside semax. [Limited human data; primarily preclinical; no Phase 2 or Phase 3 RCT for healthy-adult cognitive use] Selank is not FDA-approved for any indication. Its use for cognitive enhancement has not been approved by the FDA. Selank is not on the FDA Category 1 positive list, is not the subject of a USP/NF monograph, and is not a component of any FDA-approved drug; 503A compounding of selank from bulk is not a clearly lawful pathway in the United States. Selank is not available through Superpower.

P21

P21 (also published as P021) is a tetrapeptide derived from the active domain of ciliary neurotrophic factor (CNTF), developed to deliver neurotrophic activity with better CNS penetration than full-length CNTF. The foundational cognitive-related evidence comes from Blanchard and colleagues, whose work published in the Journal of Alzheimer's Disease in 2010 reported improved hippocampal neurogenesis in mice. Baazaoui and Iqbal, publishing in Alzheimer's Research & Therapy in 2017, showed P021 attenuated synaptic deficits in an Alzheimer's disease mouse model. Rockenstein and colleagues, publishing in the Journal of Alzheimer's Disease in 2011, CNTF-derived peptides and cerebrolysin compared in an Alzheimer's disease transgenic mouse model, providing direct preclinical evidence for P021 alongside a comparator neuropeptide. [Animal study only — no completed human clinical trials]

This compound has not been approved by the FDA for any medical use. The evidence cited here is from animal studies only. P21 is not available through Superpower or any licensed prescriber for this use. Inclusion is for educational context only.

Dihexa

Dihexa is a small-molecule angiotensin IV analog, orally active in animal models, developed to target the hepatocyte growth factor (HGF) and c-Met receptor system for procognitive effects in preclinical research. Benoist and colleagues, publishing in the Journal of Pharmacology and Experimental Therapeutics in 2014, characterized dihexa's synaptogenic mechanism — a distinct mechanism from the BDNF and GABAergic pathways targeted by semax and selank. Wright and colleagues, in a 2015 review in Progress in Neurobiology, angiotensin IV analogs for Alzheimer's research, though no human clinical trial has been completed. Sun and colleagues, publishing in Brain Sciences in 2021, reported PI3K/AKT signaling effects in mice. [Animal study only — no completed human clinical trials]

This compound has not been approved by the FDA for any medical use. The evidence cited here is from animal studies only. Dihexa is not available through Superpower or any licensed prescriber for this use. Inclusion is for educational context only.

Regulatory Status at a Glance

As of April 2026, the compounds discussed in this article carry different regulatory statuses. These distinctions matter when discussing any of them with a healthcare provider.

• Semax: Not FDA-approved for any indication. Removed from FDA Category 2 (under-evaluation bulk drug substance list) on April 22, 2026; not on FDA Category 1 (positive) list; not the subject of a USP/NF monograph; not a component of any FDA-approved drug. 503A compounding of semax from bulk drug substance is not a clearly lawful pathway in the United States. Registered in Russia for certain neurological conditions; a foreign regulatory registration does not confer FDA-approved status and does not establish any US regulatory pathway for prescription, compounding, or marketing.
• Selank: Not FDA-approved for any indication. Not on FDA Category 1 list; not the subject of a USP/NF monograph; not a component of any FDA-approved drug. 503A compounding of selank from bulk is not a clearly lawful pathway in the United States. Registered in Russia for anxiolytic use; a foreign regulatory registration does not confer FDA-approved status and does not establish any US regulatory pathway for prescription, compounding, or marketing.
• P21: Research-only; not approved for human use; not available by prescription in the US; no human-use regulatory pathway.
• Dihexa: Research-only; not approved for human use; not available by prescription in the US; no human-use regulatory pathway.

Compounds listed as 'research-only' are not legal to prescribe, compound, or sell for human use in the US. Their presence in this article is for educational context only. An RUO (Research Use Only) label does not confer any legal pathway for human use; FDA has taken enforcement action under the intended use doctrine (21 C.F.R. § 201.128) against sellers whose RUO-labeled products are marketed to or purchased by consumers for self-administration.

A survey by Vanhee and colleagues published in Drug Testing and Analysis in 2020 found cognitive peptides in seized preparations sold outside licensed channels — a finding that underscores the sourcing risks associated with unregulated nootropic peptide products. Mendias and Awan, writing in Sports Medicine in 2026, reviewed unapproved peptide therapies for athletes, characterizing safety and regulatory concerns that the authors note are applicable to the broader unapproved-peptide market.

Considerations When Comparing Nootropic Peptides

Direct comparison between semax, selank, P21, and dihexa is not straightforward — they have been studied in different species, at different doses, and using different endpoints. Inferring relative effectiveness from separate preclinical studies is methodologically unreliable. A licensed provider evaluating a patient for a compound in this category would consider several factors before any discussion could proceed.

Your specific cognitive sub-goal: Anxiety-related cognitive concerns and attention concerns under stress have been discussed in research literature separately from age-related memory decline or neurodegeneration risk. Selank's GABAergic profile and semax's BDNF-related profile represent different mechanistic categories in the preclinical literature, though none of these compounds has established human clinical utility.

Existing health conditions and biomarker profile: Hypothyroidism, vitamin B12 deficiency, insulin resistance, and chronic inflammation each produce measurable cognitive effects. Before any neuropeptide is considered, a provider will typically rule out or address these reversible contributors. A baseline TSH and vitamin B12 level are among the first steps in a cognitive evaluation.

Evidence level comfort: Semax and selank have at least limited human data, including neuroimaging studies in healthy subjects. P21 and dihexa have no published human data at any dose. A provider will factor the evidence gap into any discussion. Research-only compounds are not available through licensed prescribers regardless of individual preferences.

Route and protocol preferences: Semax and selank are administered intranasally — a route with specific compliance and dose-consistency considerations. P21 and dihexa routes in humans are not established from any clinical trial.

Regulatory status: Neither semax nor selank meets the statutory pathways for 503A bulk drug substance compounding (no USP/NF monograph, not a component of an FDA-approved drug, not on the FDA Category 1 positive list); semax was further removed from the FDA Category 2 interim-review list on April 22, 2026. P21 and dihexa are research-only compounds with no human-use regulatory pathway. For all four compounds, there is no clearly lawful US prescribing or compounding pathway at this time. This is not a marginal consideration — it determines what conversation with a provider is legally possible.

This is not an exhaustive list of clinical considerations. A licensed provider will evaluate your full health history, current medications, and baseline lab results before recommending any compound.

Safety Considerations

Safety data for nootropic peptides as a class is limited by the absence of completed Phase 2 or Phase 3 human trials for any compound in this article. The compounds are not equivalent in their risk profiles, and generalizations across the category are not warranted.

For semax and selank, human safety reporting exists primarily from Russian clinical experience and the neuroimaging studies. These data sets do not meet the sample sizes or systematic adverse-event reporting standards of FDA-reviewed clinical trials. For P21 and dihexa, no human safety data has been published.

Contraindications that apply broadly to this compound class include:

• Pregnancy and breastfeeding — no reproductive safety data exists for any compound in this category
• Active or history of CNS malignancy — compounds interacting with growth factor pathways (particularly those targeting BDNF-trkB or HGF-c-Met) carry theoretical concern regarding proliferative signaling; not specifically studied in these populations
• GABAergic interaction signal (mechanistic): selank's GABAergic-modulation mechanism raises a theoretical interaction with benzodiazepines, barbiturates, and other GABA modulators; the 2017 study by Kasian and colleagues documented synergistic enhancement of diazepam's effect in preclinical models. This is a mechanism-level observation; selank does not have a clearly lawful US human-use pathway, so clinical co-administration scenarios are not currently foreseeable in US practice.
• Unregulated sourcing — products purchased outside licensed pharmacy channels carry contamination and dosing risks documented in the Vanhee 2020 survey

For compound-specific safety profiles, individual compound pages will be available as the peptides cluster expands.

What to Test Before Starting Nootropic Peptides

Regardless of which compound you and your provider discuss, baseline biomarker testing establishes a measurable starting point. Without it, there is no objective way to assess whether a compound is producing the expected physiological changes — or whether the cognitive concern that drove the search reflects an underlying and potentially reversible condition rather than a peptide deficiency.

• TSH (thyroid-stimulating hormone): Measures the pituitary's signal to the thyroid. Why it matters for cognitive health: hypothyroidism produces cognitive slowing, memory impairment, and brain fog that can be mistaken for primary cognitive decline. TSH testing is the first-line screen for thyroid-driven cognitive symptoms and should precede any neuropeptide conversation.
• Vitamin B12: Measures circulating B12, essential for myelin synthesis and neuronal function. Why it matters: B12 deficiency produces progressive cognitive impairment, peripheral neuropathy, and fatigue — all reversible with supplementation. Vitamin B12 testing is especially relevant for individuals over 50 or those on acid-suppressing medications, which impair B12 absorption.
• IGF-1: The primary downstream marker of growth hormone axis activity. Why it matters for cognitive health: IGF-1 has neurotrophic functions in the central nervous system, supporting hippocampal neurogenesis and synaptic maintenance. Measuring IGF-1 levels provides context for GH-axis function, relevant when evaluating compounds that interact with neurotrophic pathways.
• hs-CRP: A sensitive marker of systemic inflammation. Why it matters: neuroinflammation is a recognized contributor to cognitive decline, and elevated systemic inflammation is associated with worse cognitive aging trajectories. High-sensitivity CRP provides an objective reference for inflammatory burden at baseline.
• Fasting glucose and HbA1c: Measures current and 3-month average blood glucose. Why they matter: insulin resistance impairs hippocampal function and is associated with accelerated cognitive decline. Measuring fasting glucose and HbA1c establishes the metabolic context before attributing cognitive concerns to a peptide target.
• Comprehensive metabolic panel (including ALT, AST, eGFR): Liver and kidney function markers. Why they matter: injectable peptide compounds are metabolized and cleared through the liver and kidneys; impaired organ function affects both pharmacokinetics and safety context.

TSH, vitamin B12, IGF-1, hs-CRP, and a metabolic panel covering liver and kidney function establish the cognitive health baseline that makes any subsequent change attributable to a known starting point. Testing these neurotransmitter and cognitive longevity markers before any intervention creates the reference dataset that a follow-up evaluation requires.

US Regulatory Status and Access

Semax and selank are not FDA-approved, are not on the FDA Category 1 positive list for 503A bulk compounding, and do not meet the other statutory 503A bulk pathways (USP/NF monograph, component of an FDA-approved drug). Semax was removed from the FDA Category 2 interim-review list on April 22, 2026. As a result, there is no clear lawful US pathway to obtain these compounds for human use at this time.

P21 and dihexa have never had a human-use regulatory pathway and are research-only compounds, not legal to prescribe, compound, or sell for human use. Any product sold online as semax, selank, P21, or dihexa operates outside FDA oversight and carries contamination, identity, purity, and dosing risks documented in the Vanhee 2020 survey. An RUO label on a product does not make it legal for human use.

For any cognitive concern, the appropriate starting point is a provider evaluation, not a supplier search. A provider can assess whether the cognitive concern being explored has a more immediately addressable cause — a thyroid issue, a B12 deficiency, a metabolic pattern — before any unapproved peptide compound enters the discussion.

Understanding Your Baseline

With four compounds profiled here — each targeting a different pathway and carrying a different evidence level — the question of which one is relevant to a specific individual cannot be answered without knowing where that individual's biology currently stands. A TSH that reveals subclinical hypothyroidism, a B12 level in the deficiency range, or an hs-CRP above the reference range each points toward a more clinically tractable intervention than an unregulated peptide with animal-only evidence. Baseline data is what transforms a general interest in cognitive support into a specific clinical conversation.

That principle — test first, then decide — is central to Superpower's approach to preventive health. Whether the conversation with your provider leads to addressing a reversible metabolic contributor, discussing a compounded neuropeptide with limited human data, or pursuing a different approach entirely, the starting point is the same: knowing where your biomarkers stand.

IMPORTANT SAFETY INFORMATION

Semax is not approved by the FDA for any indication. On April 22, 2026, the FDA removed semax from the Category 2 list of bulk drug substances under evaluation for 503A compounding. Semax is not on the FDA Category 1 positive list, is not the subject of a USP/NF monograph, and is not a component of any FDA-approved drug; 503A compounding of semax from bulk drug substance is not currently a clearly lawful pathway in the United States. Its use for cognitive enhancement has not been approved by the FDA, and the safety and efficacy for this use have not been established through adequate and well-controlled clinical trials. Superpower does not offer semax. Always consult a licensed healthcare provider before initiating any peptide therapy. Common reported effects in Russian clinical experience include mild headache and transient nasal irritation with intranasal administration; systematic adverse event data meeting FDA standards does not exist for healthy-population cognitive use.

Selank is not approved by the FDA for any indication. Selank is not on the FDA Category 1 positive list, is not the subject of a USP/NF monograph, and is not a component of any FDA-approved drug; 503A compounding of selank from bulk drug substance is not a clearly lawful pathway in the United States. Its use for cognitive enhancement or anxiety has not been approved by the FDA, and the safety and efficacy for this use have not been established through adequate and well-controlled clinical trials. Superpower does not offer selank. Potential interaction risk with GABAergic medications (including benzodiazepines) has been documented in preclinical studies.

P21 is not approved by the FDA for any medical use. Research on P21 has been limited to laboratory and animal studies, with no human clinical trial data available. Its safety, efficacy, appropriate dosing, and long-term effects in humans have not been established. P21 is not prescribed, compounded, or dispensed through Superpower. This section is provided for educational purposes only and does not constitute medical advice or an endorsement of use.

Dihexa is not approved by the FDA for any medical use. Research on dihexa has been limited to laboratory and animal studies, with no human clinical trial data available. Its safety, efficacy, appropriate dosing, and long-term effects in humans have not been established. Dihexa is not prescribed, compounded, or dispensed through Superpower. This section is provided for educational purposes only and does not constitute medical advice or an endorsement of use.

For FDA-approved prescribing information for any approved prescription drug, see dailymed.nlm.nih.gov. For FDA guidance on human drug compounding and peptide compounding, see fda.gov/drugs/human-drug-compounding. None of the compounds discussed in this article has FDA-approved prescribing information to cite.