PepRank

P21 (P021)

43%positive15 reports

Also: Peptide 021 · adamantylated CNTF-derived tetrapeptide

CautionMemoryFocusNasal / Oral / Injection

CNTF-derived neurogenic peptide from Alzheimer's mouse work; grey market only.

DGGL · P021: Ac-Asp-Gly-Gly-Leu-adamantylglycine-NH2 (non-standard C-terminal residue); CNTF-derived (4 residues)

DGGL P021: Ac-Asp-Gly-Gly-Leu-adamantylglycine-NH2 (non-standard C-terminal residue); CNTF-derived

#22 of 61 research peptides · updated
Access
Grey market
Cost / month
≈ €45–180
researchers' estimate; no listing to price
NasalFelt in 20 min – 1 h
15 user reports
Positive 6Mixed 4Negative 3Bad reaction 2

  • r/Biohackers· · 6 upvotesOriginal ↗

    P21 is a mystery peptide, but based on my experience of continuous use, it seems to somewhat relieve depressive symptoms.

    PositiveMood · continuous use

  • r/NooTopics· · 4 upvotesOriginal ↗

    I've used P21 and Adamax, would rate both a 7/10, Cerebro/Cortex as close to 10 as anything I've tried.

    PositiveFocus

  • r/Cerebrolysin· · 1 upvotesOriginal ↗

    My p21 experience was convoluted with p22-28. I ended up getting extremely angry, which is unlike me.

    Negative

    taken together with PE-22-28

Strict case
No human safety data; deliberately drives neurogenesis via a growth-factor pathway, and products are of uncertain identity.
Users report
Sparse (under 20 first-hand Reddit reports), about half positive: more stamina for studying, presence and less anxiety, TBI recovery, usually rated below genuine Cerebrolysin. Others report panic on injection, nightmares, sleepiness, anger, lingering head heat, tinnitus or mild hair shedding, and tolerance comes fast. One unverified user describes near-blindness (suppressed cone responses on mfERG) after 7.5 months of nasal use. Few report outright nothing, though many call it subtle; vendor identity confusion is common.
Best effects
Study stamina/persistence · being 'in the moment', less overthinking · mild stimulation
Downsides
Acute panic/anxiety after injection · head warmth, tinnitus · irritability/anger · mild hair shedding · rapid tolerance
Watch
No human data of any kind; neurogenic/neurotrophic (CNTF/LIF pathway) effects with unknown long-term consequences · grey-market identity unclear (with or without adamantane)
Evidence
Animal only
Typical use
500 mcg-1 mg/day nasal or subq (community, wide range).
Getting it
Research-peptide vendors only (first Ceretropic and its Mexican reseller, now Chinese suppliers and 'research use' shops). Products disagree on whether the adamantane group is present, and at least one vendor admitted its P21 was not the real sequence.
Stacked with
Semax: Users combine them in one syringe or spray and describe the mix as more stimulating than either alone. · Cerebrolysin: Often run alongside or instead of it; several users who tried both preferred genuine Cerebrolysin. · PE-22-28: One user who took both became uncharacteristically angry.

User reports 17

  • r/Biohackers· · 6 upvotesOriginal ↗

    P21 is a mystery peptide, but based on my experience of continuous use, it seems to somewhat relieve depressive symptoms.

    PositiveMood · continuous use

  • r/NooTopics· · 4 upvotesOriginal ↗

    I've used P21 and Adamax, would rate both a 7/10, Cerebro/Cortex as close to 10 as anything I've tried.

    PositiveFocus

  • r/NooTopics· · 3 upvotesOriginal ↗

    Less anxiety, more "in the moment" instead of overthinking, more relaxed in social situations, i think more focused too.

    PositiveAnxiety · Nasal · 2 nasal spray bottles

    used to repair possible damage from heavy drinking when young

  • r/Cerebrolysin· · 3 upvotesOriginal ↗

    P21 rocks but if you have serious issues you will need a lot of it. It makes my hair fall out too a little. For me it’s worth it but ymmv.

    PositiveNasal

    chronic sinus infection with mould biofilm

  • r/Peptidesource· · 2 upvotesOriginal ↗

    Semax didn't do anything for me. P21 knocked my tbi back to where it belongs. I stayed on it for too long though.

    PositiveRecovery · Injection

    traumatic brain injury; Semax alone did nothing

  • r/visualsnow· · 2 upvotesOriginal ↗

    I’ve been on p21 for 3 weeks and had a seizure that gave me a concussion 48 hours ago. I needed stitches. My mental clarity resumed much faster than normal.

    PositiveRecovery · 3 weeks

    TBI, epilepsy and amnesia; had a seizure with concussion while on P21 (pre-existing epilepsy), then doubled the dose

  • r/NooTopics· · 4 upvotesOriginal ↗

    I used 1mg per spray and the effects were quite noticeable initially. I got a tolerance to the stimulating effects because and this led me to overuse my rations for the day by a lot. It's very easy to overuse.

    MixedFocus · 1 mg per spray; later 3-4 mg/day · Nasal

    tried several Chinese vendors; stacks with stimulants

  • r/Biohackers· · 3 upvotesOriginal ↗

    literally seconds after the injection, I got hit by a massive panic attack. It came out of nowhere and lasted for about an hour. Heart racing, pure fight-or-flight mode. But then, as soon as it faded, it was replaced by a huge smile and a sudden burst of “feel-good” energy.

    MixedEnergy · 600 mcg · Injection · 2 days

  • r/NooTopics· · 1 upvotesOriginal ↗

    Honestly no would rather stick to cerebrolysin I felt the benefits more that p-21. I’ve been taking ever pharm as cerebrolysin. Noticed a big difference like it was night and day

    MixedFocus

    sold as "p21 adamantane"; positive sensation at the back of the head on the first dose

  • r/visualsnow· · 1 upvotesOriginal ↗

    P21 made me anxious af during the treatment and some time after but I feel like my brain got good benefits

    Mixed

  • r/Cerebrolysin· · 1 upvotesOriginal ↗

    My p21 experience was convoluted with p22-28. I ended up getting extremely angry, which is unlike me.

    Negative

    taken together with PE-22-28

  • r/NooTopics· · 1 upvotesOriginal ↗

    I am still unsure about the P21, it’s giving me nightmares, I tried dosing down but it might just be wrong for my system.

    NegativeSleep

  • r/Biohackers· · 1 upvotesOriginal ↗

    It makes me sleepy at 333mcg

    Negative333 mcg

  • r/Biohackers· · 1 upvotesOriginal ↗

    I took a week of p21 and got good effects (mid) but now my head is hot and i haven't taken it for the past 3 days but the hotness is still there. I took a different source p21 6 months ago and the positive effects were stronger although it also left me with a tinnitus for 4 days...

    Bad reaction1 week (two courses from different sources, 6 months apart)

  • r/NooTopics· · 1 upvotesOriginal ↗

    Used 200mg of intranasal p21 purchased from Mexican cuuerpoymente back when they shipped to usa. After 7.5 months of use terrible visual side effects like after images, glare, halos, blurred vision and difficulty focusing and accommodating.

    Bad reaction200 mg total · Nasal · 7.5 months

    unverified; bought from the Mexican reseller of Ceretropic products; says he knows six others with milder vision problems and has been accused of being a paid detractor

  • r/Cuerpoymente· · 1 upvotesOriginal ↗

    I’ve been using P21 and Semax for about a week now and so far getting good results

    Positive1 week · vendor-adjacent

    posted in the vendor's own subreddit; P21 taken with Semax

  • r/Cuerpoymente· · 1 upvotesOriginal ↗

    Hey, ive been using p21 and its great.

    Positivevendor-adjacent

    posted in the vendor's own subreddit

Safety

Tier by safety barStrict CautionBalanced CautionEvidence only Caution

Seen harmMechanismData gapSilent harmProduct

Seen harm 1/3
No human study exists. One first-hand report describes near-blindness with suppressed cone responses on electroretinography after 7.5 months of nasal use, unresolved after a year, from a vendor of uncertain identity; isolated and unverified. r/NooTopics: near-blindness with suppressed cone responses after 7.5 months of intranasal P21 ↗
Mechanism 1/3
A CNTF-derived peptidomimetic built to raise BDNF and neurogenesis without CNTF's gp130 signalling, the source of full CNTF's anorexia and muscle loss; up to 18 months of rodent dosing caused no tumours or weight loss, so the concern is speculative. ADDF Cognitive Vitality report on P021: no human studies; 18-month rodent dosing without tumours ↗Kazim et al. 2014: chronic oral P021 in 3xTg-AD mice (PubMed 25046994) ↗
Data gap 3/3
No human data of any kind, and vendors disagree on whether the adamantane group is present. ADDF Cognitive Vitality report on P021: no human studies; 18-month rodent dosing without tumours ↗
Silent harm 1/3
Reported effects (panic, head heat, tinnitus) are felt within days, though the isolated visual report developed over months.
Product 2/3
Grey-market nasal sprays, capsules or vials, with the molecule's identity disputed between vendors.
Never if
Pregnancy or breastfeeding (no human reproductive data)

Where to buy 0 in Europe · 3 total

ShopFormPricePer mgTesting
Nootropic SourceUSpowder · 50 mg€5864.95 USD€1.17/mgOwn COA
Nootropic SourceUSspray · 50 mg€7279.95 USD€1.44/mgOwn COA
SwissChemsUSpowder · 5 mg€103114.95 USD€21/mgThird-party testedout of stock

Studies 5

Sources 2

More in Neuroprotection & repair all 10 →

  1. 1ARA-290 QEQLERALNSS (11 residues) Caution Injection≈ €180–630 / month56%positive40 reportsNon-erythropoietic EPO-derived peptide for small-fibre neuropathy pain.
  2. 2Cortexin Caution Injection≈ €36–90 / month50%positive20 reportsRussian brain-cortex extract, Cerebrolysin cousin; 10-day IM courses.Animal-brain extract given by injection: immune/allergic and theoretical prion risk, and it shares Cerebrolysin's SAE signal.
  3. 3NAP / Davunetide NAPVSIPQ (8 residues) Clean Nasal2/10estimateADNP-derived microtubule-stabilising peptide; safe in a large trial but ineffective.
  4. 4Dihexa YI (2 residues) Excluded Oral / Topical / Injection≈ €13–53 / month50%positive30 reportsAngiotensin-IV analogue claimed as potent synaptogenic; hyped, not evidenced in humans.Activates the oncogenic HGF/c-Met pathway, has no human safety data, and its foundational studies are under expressions of concern.
  5. 5Humanin MAPRGFSCLLLLTSEIDLPVKRRA (24 residues) Excluded Injection43%positive1 reportsMitochondrial-derived cytoprotective peptide; anti-Alzheimer's in animals only.Its anti-apoptotic action helps glioma cells survive chemotherapy in animal studies, and there is no human data.
  6. 6FGL EVYVVAENQQGKSKA (15 residues) Excluded Nasal / Injection43%positive1 reportsNCAM mimetic that activates FGF receptors; rodent memory data only.Agonist of the mitogenic FGF receptor, with only phase-1 data and no users to learn from.
  7. 7Cerebrolysin Excluded Nasal / Injection / IV≈ €140–540 / month40%positive29 reportsPig-brain peptide mix for stroke/TBI; strong anecdotes, real safety questions.Cochrane found more non-fatal serious adverse events than placebo; animal-derived injectable with allergy/immune reaction risk.
  8. 8Corticotropin (repository ACTH gel) Excluded Injection43%positive15 reportsPituitary hormone gel approved for MS relapses; works like steroids, costs like a luxury car.Drives the adrenals to flood the body with cortisol, so it carries the corticosteroid label warnings (infection, Cushing's syndrome, adrenal insufficiency on withdrawal, GI perforation, psychosis, high blood pressure and glucose, bone loss) plus anaphylaxis. A prescription relapse treatment under a neurologist, not something to take outside one.
  9. 9Glatiramer acetate Excluded Injection37%positive24 reportsApproved MS drug made of random myelin-mimicking peptide chains; modest relapse cut, injection burden.Prescription immunomodulator for relapsing MS with an FDA boxed warning for anaphylaxis (82 cases, 6 deaths reported to 2024, some years into treatment), plus label warnings for liver injury and skin necrosis. Worth it for MS under a neurologist; not a self-directed peptide.

Sequence beads

Each bead is one amino acid in the peptide's chain, coloured by its side chain: grey for non-polar, cyan for polar, blue for positively charged and fuchsia for negatively charged. Length and mix tell related peptides apart at a glance, from a two-residue dipeptide like carnosine to a 43-residue protein like thymosin beta-4. The colours describe chemistry only and predict neither effect nor safety.

non-polarpolarpositivenegative

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. Kept peptides rank by the same reports' mean grade, shrunk the same way, and excluded ones follow in that order.

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 alongside the computed scores until reports arrive.

Safety tier

Each peptide is tiered clean, caution or excluded from its five risk axes under the chosen safety bar. An excluded peptide has a plausible route to serious harm, 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 exclude a peptide. 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.

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.

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.