PepRank

Dihexa

Also: PNB-0408 · N-hexanoic-Tyr-Ile-(6) aminohexanoic amide

MemoryFocusOral / Topical / Injection

Angiotensin-IV analogue claimed as potent synaptogenic; hyped, not evidenced in humans.

Safety tier
Avoid
strict bar
Positive
50%
of 30 reports
Per month
≈ €13–53
by mouth
Rank
#35
of 61 research peptides

At a glance

Access
Grey market
OralFelt in 1–2 h
TopicalFelt in 1–2 h
Strict case
Activates the oncogenic HGF/c-Met pathway, has no human safety data, and its foundational studies are under expressions of concern.
Best effects
Energy and mental clarity · faster learning/recall · effects persist between doses (long half-life)
Downsides
Irritability/anger · no effect for many · dosing confusion across routes
Typical use
5-20 mg/day oral or transdermal (community), often intermittent. Users report 2.6–4.9 mg/day (median 4.3 mg, n=6).
Stacked with
Stacked with
Modafinil or ADHD stimulants: Commonly combined for study sessions; NooTopics regulars call pairing a plasticity drug with stimulants reckless. · Semax / Cerebrolysin / P21: Grouped in "brain repair" stacks for TBI or burnout, usually run one at a time to tell effects apart. · Eutropoflavin or tropoflavin: TrkB agonists stacked with it by chess and memory self-testers.

Safety

Watch
Acts on the HGF/c-Met pathway, a well-known oncogenic driver (tumour growth, invasion, angiogenesis); no carcinogenicity data · FDA found no human exposure data at all · the founding research (Harding/Athira) received expressions of concern; the related drug fosgonimeton failed its phase 2/3 Alzheimer's trial (2024) · theoretical maladaptive plasticity, made worse when stacked with stimulants
Tier by safety barStrict AvoidBalanced AvoidEvidence only Caution
  • Seen harm1 of 3
  • Mechanism2 of 3
  • Data gap3 of 3
  • Silent harm3 of 3
  • Product2 of 3
Never if
Active cancer or a history of cancer · Pregnancy or breastfeeding (no human reproductive data)
Why each score
Seen harm 1/3
FDA found no human exposure data. One first-hand report claims lasting interference with language learning years later, which is isolated and unverifiable; others describe irritability and fatigue. FDA: bulk drug substances that may present significant safety risks (category 2 and withdrawn nominations) ↗r/Biohackers: self-reported lasting interference with language learning after dihexa ↗
Mechanism 2/3
Marketed as a potentiator of HGF/c-Met, an oncogenic pathway, but the paper showing that mechanism in vivo was retracted in 2025 and others by the same group carry expressions of concern; the pathway concern remains credible but no longer demonstrated for dihexa. Retraction notice (2025): Benoist et al. 2014, the dihexa HGF/c-Met mechanism paper (JPET) ↗Retraction Watch 2021: four papers by the Athira CEO earn expressions of concern ↗
Data gap 3/3
No human safety data, and no chronic toxicity or carcinogenicity study; the nearest relative, fosgonimeton, failed a 554-patient Alzheimer trial that excluded anyone with recent cancer. FDA: bulk drug substances that may present significant safety risks (category 2 and withdrawn nominations) ↗LIFT-AD (NCT04488419): fosgonimeton, an HGF/MET modulator, n=554, failed ↗
Silent harm 3/3
Tumour promotion through c-Met signalling would be silent and delayed.
Product 2/3
Mostly oral capsules or powder from research-chemical vendors, plus DMSO transdermal solutions; a few inject it.

User reports

All 30 reports →
Users report
Polarised: many report energy, faster learning, recall and even chess-rating gains within hours of a dose; others feel nothing even at 30 mg, perhaps 15-25%. Side effects are frequent: insomnia or 3 am waking, or the opposite (exhaustion, dozing off), anger/irritability and emotional flattening. One user reports permanent language interference after months of use and one heard voices falling asleep; commenters also warn of 'aberrant learning' and the cancer mechanism.
Glowing 5Positive 10Mixed 3Nothing 4Negative 6Bad reaction 2
  • r/Cerebrolysin· · 16 upvotesOriginal ↗

    I am on week 5 of a once weekly Dihexa cycle. So far I have noticed major improvements in athletic ability in rock climbing / basketball & ability to learn to drive a Truck and remember things needed to pass the written tests in CDL school.

    GlowingMemory · 10 mg once weekly in DMSO · Topical · 8-week cycle

    learning to drive a truck for a CDL licence

  • r/Biohackers· · 16 upvotesOriginal ↗

    It is super-effective for increasing memory acquisition (especially for language or stuff like programming), so effective that I have to avoid filling my brain with trash information for the duration of effects.

    GlowingMemory · Topical

  • r/NooTopics· · 13 upvotesOriginal ↗

    Dihexa causes additional flatness. Ketamine can help with apathy and anhedonia.

    NegativeMood

    anhedonia; confirms in a reply it was "strongly so" for them

Where to buy

All 8 offers →
Getting it
Research-chemical and peptide vendors sell powder, capsules and DMSO/transdermal solutions; some US telehealth clinics route it through compounding pharmacies (one user paid $355 for 30 days of capsules) despite its FDA Category 2 status.

A month at 5–20 mg/day costs ≈ €13–53 from PGL Chemie at €0.089/mg, as no shop scoring 4 of 5 on trust lists it. At the 2.6–4.9 mg/day users report, ≈ €7–13.

No trusted shop in the EU lists it; every listing is on the buy page.

Studies

Evidence
Animal only
3 more studies and 3 sources

Sources

Molecule

Sequence
YI
Length
2 amino acids
Modifications
N-hexanoyl-Tyr-Ile-(6-aminohexanoic) amide; angiotensin IV derived, largely non-peptidic

Sequence

The peptide's chain of amino acids from its start (the N-terminus) to its end, one bead and one letter for each: A alanine, C cysteine, D aspartic acid, E glutamic acid, F phenylalanine, G glycine, H histidine, I isoleucine, K lysine, L leucine, M methionine, N asparagine, P proline, Q glutamine, R arginine, S serine, T threonine, V valine, W tryptophan, Y tyrosine. A modification such as an N-acetyl cap or a C-terminal amide changes how long it lasts in the body. Length tells related peptides apart, from a two-residue dipeptide like carnosine to a 43-residue protein like thymosin beta-4, and predicts neither effect nor safety.

Report grades

Every first-hand Reddit or X report is graded on its own, from glowing through positive, mixed, nothing and negative to bad reaction, and the bar shows how those grades split. Posts that look vendor-adjacent stay on the peptide's page but are left out of the counts.

GlowingPositiveMixedNothingNegativeBad reaction

% positive

The share of a peptide's graded Reddit and X reports that are glowing or positive, vendor-adjacent posts left out. A peptide with few reports is pulled toward the average of all reports, as if it had eight average ones besides its own, so two glowing posts cannot top the list. Peptides rank by this figure, those with no graded report yet after those with one, and Avoid ones after every other entry.

Researcher estimate

No first-hand report of this peptide has been graded yet, so the figure is the researchers' own rating out of 10 from what they read about it. It ranks after every peptide with graded reports until its own arrive.

Safety tier

Each peptide is tiered Clean, Caution or Avoid from its five risk axes under the chosen safety bar. An Avoid peptide carries a real risk of harm, a plausible route to serious harm rather than mere unpleasantness, so it stays listed with the reason but ranks behind every other entry, however good its reviews.

Safety bar

The safety bar sets how much risk it takes to rate a peptide Avoid. Strict: out on any serious mechanism with little human data, or any documented serious harm. Balanced: out on documented serious harm (unless it is obvious, reversible and from a regulated product), or a serious mechanism whose harm would be silent with no human data at all. Evidence only: out only on documented serious harm in humans that is lasting, delayed or from grey-market product.

Seen harm

Documented serious adverse events in humans, from 0 for none despite real exposure to 3 for deaths or several well-documented serious harms. Serious means a hospital or emergency visit or harm lasting weeks, so a headache or a bad night does not count.

Mechanism

A plausible biological route to serious harm at the doses people use, such as growth-factor signalling, hormone-axis suppression, heart or blood-pressure effects or immune activation. It runs from 0 when none is known to 3 when a dangerous pathway has been shown in living animals.

Data gap

How little human safety data exists for the molecule actually sold, from 0 for an approved drug with large trials and years of use to 3 for no human safety data at all. A modified analogue does not inherit its parent's trials.

Silent harm

Whether the feared harm would show quickly or stay hidden, from 0 when it is obvious and goes on stopping to 3 when it is silent and delayed, like tumour promotion or slow organ damage. User reports cannot reveal a harm that takes years to appear, so a high score here limits what good reviews can tell you.

Product

The risk of what people actually buy, from 0 for a regulated pharmacy or supplement product taken by mouth or on the skin to 3 for a grey-market injectable. In one dataset of 6,441 grey-market samples, 42–71% failed basic quality criteria and 15% carried endotoxin; taken by mouth or in the nose, a pack avoids the injection risks.

Evidence

The strongest kind of study behind the peptide's effects, from an approved drug through human controlled trials and small human studies to animal work or nothing of its own. Animal results often fail to carry over to people.

Access

How people get it: as an approved drug, a compounded prescription, an over-the-counter supplement or from the grey market, where nobody checks the vial. The channel decides both the legal position and the risk of a bad batch.

Price per month

Thirty days of the typical dose, from its low end to its high end, priced at the listing a careful buyer would choose: in stock, from a shop scoring 4 of 5 on trust (third-party tested where no score is set), failing that 3, a pure pack before a blend, a European shop first, then the cheapest per mg. The range is the dose's, not the shops'. A per-dose amount counts once a day unless the dose says otherwise. Prices are in euros at ECB rates of 2026-10-29, before shipping; the shop table keeps each listing's price per mg, per gram for bulk supplements. Where no listing can be priced the researchers' own estimate stands in, and says so.

Dose users report

The middle half of the daily doses stated in at least five first-hand reports, vendor posts left out. Where its middle sits more than twice above or below the declared dose, the month is priced at it as well, since what people take is what they pay for.

Shop trust

Each shop's trust on a 1–5 scale, read from its testing and its reputation: 1 for serious red flags (fabricated COAs, scam reports, impersonation, a closed shop), 2 for no public testing, a new shop or active complaints such as seized parcels, 3 for its own COAs or a short track record, 4 for verified third-party testing or a strong reputation, and 5 for third-party batch reports that name the shop, with years of good independent reputation. A shop without a score counts third-party batch testing as 4, its own COAs as 3 and no public tests as 2.

Best value

Within a category or a goal, a peptide that no other beats on both counts: none is rated more positively for the same or a lower monthly price, and none costs less for the same or a higher rating. The chart joins these into the best-value line; the cheapest of them and the best-rated of them both make it, so the line spans the trade-off from cheap to best. Avoid entries never count, and a peptide needs both a % positive and a price to be compared.

Testing

Whether the shop publishes lab results: third-party tested means an independent lab checks each batch, own COA means the shop's own certificate of analysis, and no public tests means neither. A certificate shows purity, not safety.

Added peptide

Some packs sold under one peptide's name hold a second one, such as 5 mg GHK-Cu in a nasal kit, stated only in the description. Sprayed in the nose or injected it reaches the blood like an injection, so it carries the risk of that route and is tiered as the injectable form, whatever its tier on the skin. A pack whose page gives no contents list may hold more than its name.