DS5 Preclinical

What It Is

DS5 (also written DS-5, and occasionally expanded as "Dihexa Semax 5") is a pre-mixed research-peptide product sold by a subset of research-chemical vendors. It contains two peptides in one vial: dihexa (PNB-0408) — the angiotensin IV-derived hexapeptide analog developed at Washington State University — and semax (Met-Glu-His-Phe-Pro-Gly-Pro) — the Russian ACTH(4-10) heptapeptide analog developed at the Institute of Molecular Genetics of the Russian Academy of Sciences. The "5" in the name is a vendor convention rather than a defined pharmacologic standard; concentrations and ratios vary between vendors.

The rationale for the blend, as marketed, is a "dual-axis neurotrophic stack": dihexa engages the hepatocyte growth factor (HGF) / c-Met receptor system proposed to drive synaptogenesis; semax modulates brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) through melanocortin pathways. Two different upstream neurotrophic signals, converging on overlapping downstream cognitive substrates. In theory, combining them produces additive or synergistic cognitive enhancement while exploiting different receptor systems to avoid tolerance at either.

In practice, DS5 is not a validated protocol. There are no published clinical trials of the combination, no dose-response data for the blend, and no formal safety characterization of the co-administered peptides. The individual components have their own — and very different — evidence profiles. Semax has approximately 30 years of Russian clinical use and a published evidence base in stroke recovery, cognitive impairment, and ADHD-type presentations. Dihexa's evidence base is considerably more compromised: its foundational 2014 mechanism paper (Benoist et al., PMID 25187433) was formally retracted in April 2025 after the Leen Kawas image-manipulation investigation, and Athira Pharma's fosgonimeton — the prodrug analog that represented dihexa's largest clinical translation — failed its LIFT-AD Phase 2/3 trial in late 2024. See the dihexa and semax individual profiles for the complete picture on each component.

DS5 is typically supplied as an intranasal solution, following the semax convention of intranasal delivery. That is an unusual choice for dihexa specifically — dihexa was engineered at WSU for oral bioavailability and BBB permeability, not intranasal absorption, and there is no human pharmacokinetic data on intranasal dihexa. Intranasal semax is well-studied at the bioavailability level. The combined intranasal bioavailability of the DS5 blend is uncharacterized for its dihexa component. This is an important and under-discussed limitation.

Mechanism of Action

DS5's proposed mechanism is the union of two independent pathways, with the explicit theory that the non-overlapping receptor targets produce additive or synergistic effects.

• Dihexa — HGF/c-Met positive modulation (proposed, with caveats) — Dihexa is proposed to act as a positive allosteric modulator of HGF at the c-Met receptor, amplifying HGF-mediated synaptogenesis and dendritic spine formation. In hippocampal culture, dihexa has been reported to induce spinogenesis at picomolar concentrations — the source of the "10 million times more potent than BDNF" claim. Important caveats: the central mechanism paper (Benoist 2014) was retracted in April 2025; the 2013 dose-finding paper (McCoy 2013) carries an expression of concern; and the largest clinical translation (fosgonimeton) failed. A few independent replications exist (Uribe 2015 hair cells, Sun 2021 APP/PS1 mice).
• Semax — BDNF/NGF upregulation via melanocortin signaling — Semax is a heptapeptide analog of ACTH(4-10) that lacks ACTH's corticotropic activity. It upregulates BDNF and NGF expression in hippocampus and cortex (Dolotov et al. 2006), modulates neurotrophin release in limbic circuitry, enhances serotonergic and dopaminergic tone, and has documented anti-amnestic and neuroprotective effects in animal stroke models. Unlike dihexa, the mechanistic evidence for semax has not been compromised by retractions or clinical failures.
• Dual-receptor non-overlap — The HGF/c-Met and melanocortin systems are biologically distinct: different receptor classes, different G-protein coupling, different downstream intracellular cascades. Combining them is not pharmacologically redundant at the receptor level. The assumption that this produces additive cognitive output is extrapolation, not demonstration.
• Shared downstream convergence — Both pathways ultimately feed into PI3K/Akt, MAPK/ERK, and CREB-mediated transcription of synaptic proteins — the canonical neurotrophic effector cascades. Theoretically, activating two independent upstream pathways could produce a stronger downstream transcriptional response than activating either alone. In practice, this has not been studied specifically for DS5.
• Different time courses — Semax's effects on BDNF are relatively acute (detectable within hours to days of dosing); dihexa's proposed synaptogenic effects, if they occur, would accrue over weeks. Proponents argue the blend therefore provides acute-plus-chronic cognitive scaffolding.
• Intranasal bioavailability mismatch — Semax has well-characterized intranasal absorption and direct nose-to-brain transport via olfactory bulb pathways. Dihexa, a lipophilic peptidomimetic engineered for oral and BBB permeability, has no published intranasal bioavailability data. Whether the dihexa fraction of an intranasal DS5 dose reaches brain in meaningful concentration is unknown.
• Tolerance and desensitization — Unstudied for the combination. Semax alone is generally considered non-tolerance-forming at typical doses; dihexa's tolerance profile is uncharacterized.

What the Research Shows

There is no peer-reviewed clinical research on DS5 as a combination. The available evidence is entirely at the individual-component level, and the two components have highly asymmetric evidence bases.

• Dihexa — foundational papers partly compromised — McCoy 2013 (PMID 23055539) is the dose-finding / procognitive paper that received an expression of concern. Benoist 2014 (PMID 25187433) was the HGF/c-Met mechanism paper; retracted April 2025. Independent replications: Uribe 2015 (PMID 25674052, hair cell preservation) and Sun 2021 (PMID 34827487, APP/PS1 mice with PI3K/Akt activation). No human trials of dihexa itself.
• Dihexa — clinical analog fosgonimeton failed LIFT-AD — Athira Pharma's phosphate prodrug analog of dihexa, fosgonimeton, was tested in NCT04488419 (LIFT-AD Phase 2/3) for mild-to-moderate Alzheimer's disease. Late-2024 topline: did not meet primary endpoint (Global Statistical Test combining cognition and function). This is the most direct human translation of the HGF/c-Met cognitive hypothesis available and it failed.
• Semax — Russian clinical evidence base — Semax has been clinically used and studied in Russia since its 1994 registration as a nasal spray. Published Russian-language trials cover acute and recovery-phase ischemic stroke, encephalopathy, ADHD-type presentations, age-related cognitive impairment, and ophthalmologic indications. Effect sizes are generally modest and the methodological rigor of the Russian literature does not map 1:1 onto Western regulatory standards, but the evidence base is substantially larger and less compromised than dihexa's.
• Semax — BDNF upregulation (independent) — Dolotov et al. 2006 (Doklady Biological Sciences) demonstrated BDNF and TrkB upregulation in rat hippocampus after intranasal semax, providing a mechanism-level foundation that has been confirmed by multiple independent groups.
• Semax — stroke recovery — Multiple Russian trials report faster neurological recovery with semax as an adjunct to standard-of-care stroke management, with effect sizes on NIHSS and disability scales. The independent methodological quality of these trials is mixed.
• Combination — nothing published — No PubMed-indexed peer-reviewed article, no ClinicalTrials.gov registration, no conference abstract, no vendor-sponsored white paper we can verify reports on the specific DS5 combination. The blend is a commercial construct, not a research-validated protocol.
• Anecdotal community reports — Reddit, peptide forum, and biohacker-community reports describe subjective cognitive benefit, calm focus, or post-concussion recovery support. These are entirely uncontrolled and subject to placebo, expectancy, and reporter-selection bias. They are not evidence in any rigorous sense.

Human Data

There is no human data on DS5 as a combination. Data for the individual components:

• Dihexa human trials — None. See the dihexa profile for the full picture on the clinical analog fosgonimeton (fosgonimeton Phase 1 NCT03298672 — safe; ACT-AD Phase 2 NCT04491006 — primary miss; SHAPE Phase 2 NCT04831281 — exploratory; LIFT-AD Phase 2/3 NCT04488419 — failed primary endpoint).
• Semax — Russian clinical experience — Semax (0.1%) is a registered intranasal spray in Russia for cerebral circulatory disorders; Semax (1%) is approved for ischemic stroke. Published Russian trials spanning three decades cover stroke, cognitive impairment, ADHD, encephalopathy, and ophthalmologic use. Independent Western replication at the Phase 3 level is limited.
• Semax — Gusev 2005 stroke trial — A Russian multicenter trial in acute ischemic stroke reporting neurological recovery benefit with semax vs placebo. Effect sizes modest; methodology does not meet Western regulatory-trial standards.
• Semax — cognitive / attention indications — Multiple smaller Russian studies in children with ADHD-type presentations and adults with mild cognitive impairment, reporting attention, memory, and behavioral improvements.
• DS5 combination — Zero published trials. Community anecdote only.

Dosing from the Literature

No formal dose-finding study exists for DS5. The doses below combine component-level data with common vendor concentrations.

Reconstitution & Storage

DS5 is typically supplied as a pre-formulated intranasal solution — no user reconstitution required. Some vendors supply lyophilized blend kits that require buffered-saline reconstitution.

• Intranasal delivery — Standard semax technique: one or two sprays per nostril with head upright, light sniff, no forceful inhalation. Rotate nostrils to limit mucosal irritation.
• Do not inject — Intranasal blends are not formulated for parenteral use. Injecting DS5 is not supported by any manufacturer or protocol.
• Temperature stability — Both peptides are relatively stable at 2–8°C in buffered solution; avoid freezing reconstituted solution (crystal formation can denature semax).
• Inspect — Clear, colorless solution at label concentration. Discard any cloudy, yellowed, or particulate-containing solution.

→ Use the Kalios Dosing Calculator for intranasal scheduling

Side Effects & Risks

Side effects reflect the combined profile of both components plus the risks specific to an unstandardized blend.

• Dihexa — theoretical c-Met cancer concern (the central risk) — c-Met is dysregulated in many human cancers where it drives proliferation, motility, and metastasis. Pharmacologically activating c-Met is the opposite direction of much of oncology drug development. The most important DS5 contraindication is any history of cancer, precancerous lesion, or family predisposition. Screen before initiation.
• Semax — nasal and ocular effects — Nasal irritation, mild congestion, transient headache, and occasional tearing are the most common semax-specific effects. Rare overstimulation or transient anxiety at higher doses.
• Combined neurotrophic overstimulation (theoretical) — Dual upstream neurotrophic activation is uncharacterized. Possible overstimulation of dendritic remodeling or aberrant synaptogenesis — theoretical and unquantified.
• Headache, fatigue, irritability — Reported community side effects shared across both components. Generally mild; dose-related.
• Sleep changes — Both components can affect sleep architecture. Vivid dreaming and either insomnia or increased sleep depth reported anecdotally.
• Blood pressure / cardiovascular — Dihexa is an angiotensin IV derivative; it does not directly activate AT1/AT2 receptors but angiotensin-pathway theoretical concerns exist. Monitor BP during extended use.
• Allergic / hypersensitivity reactions — Rare but possible with any peptide intranasal. Discontinue if rash, wheeze, facial swelling, or persistent mucosal inflammation occur.
• Drug interactions — Unstudied for the combination. Theoretical concerns with other neurotrophic peptides (cerebrolysin, selank), stimulants, and MAO inhibitors.
• WADA — Neither component is specifically named on the WADA Prohibited List as of 2026, but both are peptide-class compounds with growth-factor-adjacent mechanisms — tested athletes should assume S2 risk and consult federation.
• Sourcing and concentration variability — Pre-mixed blends have no standardized labeling enforcement. Vendor-to-vendor variance in dihexa/semax ratio and total peptide concentration is high. Third-party COA is the minimum verification floor; even then, stability of the blend over time is vendor-specific.
• Long-term safety unknown — The combination has no long-term human safety data. Extend-cycle use without breaks is not supported by any evidence.

Bloodwork & Monitoring

No formal DS5 monitoring guideline. Conservative monitoring combines the dihexa c-Met concern with standard peptide-protocol surveillance.

• Age-appropriate cancer screening (pre-initiation) — Mandatory due to the dihexa c-Met concern. Skin check, colonoscopy/mammography/PSA per age, CBC with differential to rule out occult hematologic abnormality.
• CMP — Baseline and every 8–12 weeks of continuous use.
• CBC with differential — Baseline and every 8–12 weeks.
• Blood pressure — Baseline and weekly for the first month; stable users can move to monthly monitoring. Dihexa's angiotensin-IV ancestry creates a theoretical BP signal.
• Cognitive baseline (objective) — A standardized cognitive test battery (Cambridge Brain Sciences, NIH Toolbox, or dual N-back baseline) gives an objective comparator. Subjective "feels sharper" is heavily placebo-confounded.
• Mood and sleep tracking — Both components can affect mood and sleep. Log subjectively weekly.
• Nasal exam — At 4 and 8 weeks. Persistent nasal inflammation or epistaxis warrants discontinuation.
• Periodic cancer re-screening — Long-term users should stay current on age-appropriate screening, not defer it because of a protocol.

Commonly Stacked With

→ Check compound compatibility in the Stack Builder

Regulatory Status

Related Compounds

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Next Steps

Key References

1. McCoy AT, Benoist CC, Wright JW, Kawas LH, Bule-Ghogare JM, Zhu M, Appleyard SM, Wayman GA, Harding JW. Evaluation of metabolically stabilized angiotensin IV analogs as procognitive/antidementia agents. J Pharmacol Exp Ther. 2013 Jan;344(1):141-54. PMID: 23055539. (Foundational dihexa paper — received expression of concern in 2021.)
2. Benoist CC, Kawas LH, Zhu M, et al. The procognitive and synaptogenic effects of angiotensin IV-derived peptides are dependent on activation of the hepatocyte growth factor/c-Met system. J Pharmacol Exp Ther. 2014 Nov;351(2):390-402. PMID: 25187433. RETRACTED April 2025.
3. Uribe PM, Kawas LH, Harding JW, Coffin AB. Hepatocyte growth factor mimetic protects lateral line hair cells from aminoglycoside exposure. Front Cell Neurosci. 2015 Jan 28;9:3. PMID: 25674052.
4. Sun X, Deng Y, Liang J, Lin Y, Song J, Zhao S, Zhuang G, Jia Z. AngIV-Analog Dihexa Rescues Cognitive Impairment and Recovers Memory in the APP/PS1 Mouse via the PI3K/AKT Signaling Pathway. Brain Sci. 2021 Oct 28;11(11):1421. PMID: 34827487.
5. Athira Pharma, Inc. Topline Results from Phase 2/3 LIFT-AD Clinical Trial of Fosgonimeton for Mild-to-Moderate Alzheimer's Disease. Press release, late 2024. (NCT04488419 — primary endpoint not met.)
6. Dolotov OV, Karpenko EA, Inozemtseva LS, Seredenina TS, Levitskaya NG, Rozyczka J, Dubynina EV, Novosadova EV, Andreeva LA, Alfeeva LY, Kamensky AA, Grivennikov IA, Myasoedov NF, Engele J. Semax, an analog of adrenocorticotropin (4-10), activates expression of BDNF in rat basal forebrain. Doklady Biol Sci. 2006;408:310-312.
7. Ashmarin IP, Nezavibatko VN, Myasoedov NF, Kamensky AA, Grivennikov IA, Ponomareva-Stepnaya MA, Andreeva LA, Kaplan AY, Koshelev VB, Ryasina TV. A nootropic adrenocorticotropin analog 4-10-semax (15 years experience in its design and study). Zh Vyssh Nerv Deiat Im I P Pavlova. 1997;47(2):420-430. (Semax development and mechanism review.)
8. Gusev EI, Skvortsova VI, Miasoedov NF, Nezavibat'ko VN, Zhuravleva EIu, Vanichkin AV. Effectiveness of semax in acute period of hemispheric ischemic stroke (a clinical and electrophysiological study). Zh Nevrol Psikhiatr Im S S Korsakova. 1997;97(6):26-34.
9. Gusev EI, Martynov MYu, Kostenko EV, Petrova LV, Bobyreva SN. The efficacy of semax in the treatment of patients at different stages of ischemic stroke. Zh Nevrol Psikhiatr Im S S Korsakova. 2018;118(3):61-68.
10. Levitskaya NG, Sebentsova EA, Andreeva LA, Alfeeva LYu, Kamensky AA, Myasoedov NF. Neuroprotective activity of the semax peptide in comparison with piracetam on the model of transient global ischemia. Bull Exp Biol Med. 2002;133(5):491-493.
11. Retraction Watch. Four papers by Athira CEO earn expressions of concern. September 24, 2021.
12. Retraction Watch. Biotech company agrees to pay four million dollars to settle data falsification allegations. January 7, 2025.
13. U.S. Department of Justice. Athira Pharma Agrees to Pay Multi-Million-Dollar Sum to Settle False Claims Act Allegations. Press release, January 2025.
14. FDA. Bulk Drug Substances Nominated for Use in Compounding — 503A and 503B Categories. FDA.gov. Updated 2025–2026.
15. WADA Prohibited List 2026. World Anti-Doping Agency.