The State of Peptides, 2026: What They Are, Who Is Fighting Over Them, and What Each One Can Prove

Creator: Inside Your Peptides
Published: 2026-08-22

the research desk43 sources, every identifier verifiedpublished 22 aug 202638 min readnot medical advice

The answer, first

The answer, first. A peptide is a short chain of amino acids, and US drug law draws the line at 40 residues — 40 or fewer and you are a drug, more than 40 and you are a biologic.

Of the seventeen compounds in the standard research catalogue, exactly two hold an FDA approval for the thing they are sold to do: tirzepatide and tesamorelin. Retatrutide has the trials but no filing.

Beyond those three, only thymosin alpha-1 reaches B, and only for hepatitis B. Everything else sits at C or below, and seven grade D — animal data, mechanism arguments, or nothing at all in a human being.

In July 2026 an FDA advisory committee voted to recommend six peptides for compounding against the written objection of FDA's own scientists. Nothing changed legally. Not one of them can be lawfully compounded today.

**fig 01**The boundary. Forty residues is where a peptide stops being a drug and becomes a biologic — one number, drawn in law rather than in chemistry, that decides which agency, which pathway and which statute applies.

key takeaways

Removal from FDA's Category 2 list in April 2026 was not a legalisation. Twelve peptides came off that list — including BPC-157, TB-500, KPV, MOTS-c, epitalon and semax — because the people who nominated them withdrew the nominations. They now sit in no category at all, which is worse, not better.
The July 2026 advisory vote was non-binding and went against FDA's own reviewers. The committee recommended six of seven peptides for the 503A bulks list. FDA's scientists had recommended against all seven in writing. Rulemaking is still required, and as of today no proposed rule exists.
TB-500 is not the molecule that was tested. Every human trial ran on full-length thymosin beta-4, a 43-amino-acid protein. What the market sells is Ac-LKKTETQ, a seven-residue fragment. The analytical literature states plainly that the fragment's biological effects have not been documented.
BPC-157 has no published randomised controlled trial in humans for any indication. The complete human record is an open-label bladder study in 12 women, a two-person safety report, and a retrospective knee series. That is the entire thing.
Injected NAD+ has never been tested in a controlled outcomes trial. A 2026 systematic review covering 113 studies found none. The single pharmacokinetic study found infused NAD+ is cleared from plasma so fast that levels do not rise for two hours.
The peptide with the deepest clinical file is also the one whose best trials came back flat. Thymosin alpha-1 has been through a 1,106-patient sepsis trial and a 552-patient hepatitis C trial. Both missed. Depth of evidence and strength of evidence are not the same thing.

A category error

Peptides are not one category moving together. Semaglutide and BPC-157 share a chemical class and nothing else that matters.

Not a lie. A category error.

The market talks about peptides as if they were one thing, graded on one ladder, moving together through one regulatory story. They are not.

Semaglutide and BPC-157 are both peptides in exactly the way that penicillin and a homeopathic remedy are both things you swallow. One has an approval, a phase 3 programme and a label listing its harms. The other has rodents.

This report does three jobs at once, because the questions arrive together. What is a peptide. What just happened in Washington. And what, compound by compound, can each one actually prove.

Nothing was legalised in 2026. Twelve peptides were shown the door.

How we graded

One A to E ladder for the whole field, applied to GLP-1 drugs and research tripeptides on identical terms.

Every grade below carries its reason on the same line. One ladder covers the whole field, and a GLP-1 drug is graded against the same bar as a research-catalogue tripeptide.

gradewhat it means

ARegulatory approval, or multiple adequately-powered trials agreeing with each other

BAt least one well-powered human randomised trial, with the direction replicated

CSmall or open-label human trials only

DAnimal or mechanism data only, with no controlled human outcome

EA claim the human trials have already killed

E is a verdict on a specific claim rather than a rank for a compound, which is why it does not appear in the headline count. Seven of the seventeen grade D. That is not us being harsh. That is the field.

**fig 02**The ladder. Five grades and seventeen compounds. Two stand on the top step, and the crowd is at the bottom — which is what an honest ladder looks like when nobody is graded generously.

Why 40 decides everything

Chemistry sets no size limit. US drug law draws the line at 40 residues, and that single number decides which agency, which pathway and which statute applies.

Chemistry sets no size limit. The IUPAC definition is simply two or more amino acids joined by amide bonds — nothing about where a peptide ends and a protein begins¹. Biochemistry teaching conventionally says 2 to 50 residues. US drug law says 40.

That last number is the one with consequences.

On March 23, 2020, the BPCI Act transition took effect. FDA's guidance is explicit: any amino acid polymer composed of 40 or fewer amino acids is outside the scope of the term protein².

Anything longer became a biologic regulated under the Public Health Service Act. Anything shorter stayed a drug, on the NDA pathway.

This is why semaglutide, at 31 amino acids, is a drug — and insulin, at 51, is a biologic. It is also why the entire research-peptide catalogue sits in drug territory, subject to the compounding statutes that are now the whole political fight.

Why almost all of them are injected. Peptides have oral bioavailability typically under 1%, sometimes under 0.1%⁴.

They face pepsin in the stomach, then trypsin, chymotrypsin, elastase and carboxypeptidases in the small intestine, then brush-border peptidases, then colonic microflora. Insulin is nearly completely degraded by trypsin, chymotrypsin and elastase within an hour under physiological conditions. Oral semaglutide achieves roughly 1% and is considered a triumph of formulation.

They also do not cross cell membranes well. Over 90% of clinical peptides act on extracellular targets for that reason³. Any vendor claim that a peptide resets gene expression is describing something that happens downstream of a receptor on the outside of a cell, not the peptide walking into the nucleus.

**fig 03**The peak. A purity certificate reports the area under one peak on one column. A deletion sequence, a diastereomer or a different peptide of similar hydrophobicity can sit inside that peak and never appear as a number.

What purity certificates actually certify. An HPLC chromatogram reading 99.2% is a peak-area ratio: the fraction of integrated area under the main peak, on one column, with one gradient.

It says nothing about which molecule that peak is. A deletion sequence that co-elutes, a diastereomer from racemisation, or a different peptide of similar hydrophobicity all hide inside that number.

FDA's own guidance on synthetic peptide generics recommends orthogonal analytical methods precisely because purity alone is insufficient, and names UHPLC-HRMS for impurity characterisation⁵.

Mass spectrometry supplies mass. MS/MS sequencing supplies sequence. Purity and identity are separate questions, and a certificate answering only the first has answered half.

And the two microbiology tests are not interchangeable. USP <85>, the bacterial endotoxin test, detects lipopolysaccharide from gram-negative bacteria using horseshoe crab lysate and returns a number in endotoxin units within hours.

USP <71>, the sterility test, cultures the product in two media for not less than 14 days to see whether anything grows⁶.

A product can pass one and fail the other. Neither certifies the other. Neither says anything about identity or purity. And <71> is destructive, so it cannot be run on the vial anyone actually holds.

One more thing worth stating because nobody in the market does: there is no published, peer-reviewed data on how specific research peptides degrade under freeze-thaw cycling, agitation, or light after reconstitution.

The general chemistry is well established — deamidation, peptide bond cleavage, oxidation, aggregation, all driven by temperature and moisture. The compound-specific numbers circulating as fact are not in the literature. They come from vendor pages.

reader skillsLooking at any of these compounds regardless? Read the certificate before the claim.The five measures a real COA carries, what most certificates skip, and how to verify one with the lab — in five minutes.→

The political heat

A three-year sequence, in order, ending with the fact that nothing has actually been legalised.

The peptide fight of 2025 and 2026 is a compounding fight. Under section 503A of the FD&C Act, a pharmacy can compound with a bulk substance only if it has a USP monograph, is a component of an approved drug, or appears on FDA's 503A bulks list⁷.

Section 503B does the same for outsourcing facilities. Nothing else is lawful.

**fig 04**The chamber. An advisory committee recommended six of seven peptides for the compounding list, against FDA's own reviewers in writing. The vote is non-binding, and rulemaking has not begun.

September 29, 2023 — the original ban. FDA placed kisspeptin-10 and ibutamoren into 503A Category 2, and GHRP-2, GHRP-6 and ipamorelin acetate into 503B Category 2, citing immunogenicity risk and inadequate safety data.

FDA's stated rationale for kisspeptin-10 remains on the page: compounded products may pose risk for immunogenicity for certain routes of administration and may have complexities with regard to peptide-related impurities and API characterization⁸.

January 7, 2025 — the door closes. FDA finalised its interim compounding policy at 90 FR 1136 and 90 FR 1130, and stated that it does not intend to place bulk drug substances nominated on or after January 7, 2025, into these categories⁹. The category machinery stopped accepting new entrants.

December 2024 to May 2025 — the GLP-1 wind-down. FDA declared the tirzepatide shortage resolved on December 19, 2024, and the semaglutide shortage resolved on February 21, 2025^12,13.

Compounding wind-downs ran to February 18 and April 22 for 503A pharmacies, March 19 and May 22 for 503B facilities. The Outsourcing Facilities Association sued in the Northern District of Texas on both.

Both district cases were terminated, the semaglutide one reported as a win for FDA. The Fifth Circuit heard argument around March 30, 2026, and as of today has not ruled.

September 2025 — the border tightens. FDA launched a GLP-1 API Green List on 5 September. Import Alert 66-80, the instrument that enforces it, is reported to have issued later that month¹⁴. The structure matters: 66-80 has no red list.

It operates on a green list of exempted manufacturers, and everything not on it is detained by default.

That is inverted logic compared to a normal import alert, and it is the mechanism doing the heavy lifting on GLP-1 API. The roster is small — 19 firms worldwide at the 27 July 2026 revision — and FDA revises it without notice, so treat any published count as a snapshot and read the alert itself for the current list. It was last revised on 21 August 2026.

February 27, 2026 — the political turn. HHS Secretary Robert F. Kennedy Jr., on the Joe Rogan podcast, said he expected FDA to change the status of about 14 peptides within a couple of weeks, described himself as a fan, and said he had used some himself.

April 15, 2026 — the event everybody misread. Twelve peptides came off FDA's Category 2 list: BPC-157, cathelicidin LL-37, dihexa, emideltide, epitalon, injectable GHK-Cu, KPV, PEG-MGF, melanotan II, MOTS-c, semax and TB-500. Vendor and clinic blogs sold this as a green light.

It was the opposite. The nominations were withdrawn by the nominators. As one legal analysis put it: removal from Category 2 does not render these bulk drug substances eligible for compounding under section 503A. They went from being inside the conversation to being outside it entirely.

May 12, 2026 — leadership churn. Commissioner Marty Makary, who had signed the GLP-1 crackdowns, resigned. Kyle Diamantas, previously the deputy commissioner for foods, became acting commissioner.

July 23–24, 2026 — the vote. FDA's Pharmacy Compounding Advisory Committee met on seven peptides¹⁰. FDA's own review team had recommended against all seven in writing.

On BPC-157 the briefing document is blunt: the substance is considered not well-characterized, there is a lack of evidence to support the effectiveness, and FDA proposes not adding BPC-157 free base or BPC-157 acetate to the 503A Bulks List¹¹.

The committee voted to recommend six of them anyway — BPC-157, KPV, TB-500, MOTS-c, semax and epitalon — rejecting only emideltide, on a split vote.

Observers reported an audible reaction in the room; a panel voting against FDA staff's written recommendation is close to unprecedented. It was also reported that many of the voting members consult for or are employed by companies positioned to dispense peptides.

The vote is non-binding. Changing the rule requires formal notice-and-comment rulemaking, or an act of Congress. No proposed rule has been published. Counsel estimates range from 8 to 12 months at the optimistic end to 12 to 24 months or longer.

August 1, 2026 — Louisiana goes live. Act 374 took effect, barring state licensing boards from prohibiting compounding of peptides not on FDA's Category 2 list¹⁶. Read literally, the April removal switches twelve compounds on in Louisiana.

But the Act's own text requires compliance with all applicable federal and state compounding laws, and federal law is unchanged. A state statute cannot license a federal violation. Expect this to be misread, loudly.

August 20, 2026 — the nominee. Dr. Heidi Overton was nominated as FDA Commissioner. She has reportedly expressed caution about easing restrictions on unapproved peptide injections, citing limited human safety and efficacy data.

So the position today, plainly: the liberalisation push comes from HHS. The commissioner who resisted it is gone. The acting commissioner is a food regulator. The nominee is sceptical. And the rulemaking that would actually legalise anything has not started.

Where enforcement is actually landing. Across the entire 2024–2026 warning-letter record, the recipients are GLP-1 sellers, SARM sellers and tianeptine sellers.

We located no warning letter naming BPC-157, TB-500, semax, selank or epitalon as the cited product. The classic research catalogue is not being policed by letter. It is being policed at the border and at the payment rail.

Customs and Border Protection at Cincinnati disclosed in March 2026 that since December 2025 it had intercepted over 300 master cartons concealing about 5,000 individual peptide shipments from China, each pre-labelled with its true intended recipient inside the consolidated box¹⁵.

That means the government holds roughly 5,000 US names and addresses from a single scheme.

And the research use only disclaimer does not work. FDA's language is near-identical across letters: despite statements on your product labeling marketing your products for Research Use Only, and not intended for human consumption, evidence obtained from your website establishes that your products are intended to be drugs for human use.

LegitScript, the certification body most card networks defer to, reached the same conclusion independently and went further — merchants using that language are, perhaps counterintuitively, more likely to be engaged in unapproved peptides sales¹⁷. The disclaimer is an underwriting red flag, not a shield.

The ranked field

Seventeen compounds graded for the route and purpose they are actually sold for. Two hold an approval, seven grade D.

Every compound below is graded for the route and purpose it is actually sold for. That distinction does most of the work.

GHK-Cu graded topically is a different question from GHK-Cu in a syringe. Aviptadil in an intracavernosal ED product is a different question from VIP injected subcutaneously for gut and airway inflammation.

Five rows below now carry a community file line — what our August 2026 sweep of the user communities adds to that row, read under the community evidence framework: adoption and tolerability signals, never efficacy.

#intervention · type · target · gradewhat the best evidence actually shows

01TirzepatideGIP + GLP-1 agonist · obesity and type 2 diabetesgrade A · approvedSURMOUNT-1, n=2,539, 72 weeks: −20.9% body weight at 15 mg versus −3.1% placebo. Approved 2022 for diabetes, 2023 for obesity, 2024 for sleep apnea¹⁸. Cannot: spare lean mass — a DXA substudy of 160 people found roughly 25% of the weight lost was lean tissue, and −10.9% lean mass at 72 weeks¹⁹ Community file: quieter food preoccupation is the #1 recurring report in our August 2026 GLP sweep — the phrase and its limits get a full report

02TesamorelinGHRH analogue · visceral fat in HIV lipodystrophygrade A · approvedFDA-approved 2010. Two phase 3 trials, n=412 and n=404: visceral fat −15.2% versus +5.0%, and −10.9% versus −0.6%^22,23. Cannot: work for general fat loss. The label states it is not indicated for weight loss, and the benefit reverses on stopping

03RetatrutideGIP + GLP-1 + glucagon agonist · obesitygrade B · strongPhase 2, n=338, 48 weeks: −24.2% at 12 mg versus −2.1% placebo. Four phase 3 trials completed²¹. Cannot: be bought legally. Approved nowhere, FDA filing planned Q1 2027, and every phase 3 figure is a sponsor press release rather than peer-reviewed data Community file: gray-market adoption is heavy [250 vendors tracked selling it] and the food-noise report recurs here too — with the vial-identity caveat carrying extra weight for an unapproved molecule [the community record]

04Thymosin α-1immune modulator · hepatitis B, sepsis, COVIDgrade B− / EHepatitis B: reported by its manufacturer as approved in 30-plus countries, though not in the US. The pivotal blinded phase III, n=97, missed at P=0.084. Sepsis, hepatitis C and COVID all grade E. Cannot: deliver on its reputation. TESTS, n=1,106: 28-day mortality HR 0.99, P=0.93²⁹

05Kisspeptin-10GnRH-axis stimulant · reproductive hormonesgrade C · acute onlyReplicated across at least six human studies: LH rose 4.1 to 12.4 IU/L at 1 µg/kg, testosterone up, pulse frequency up — but every one was small, n=4 to 29⁴². Cannot: be dosed chronically. Twice-daily dosing produced complete desensitisation within 14 days

06GHK-Cucopper tripeptide · skin remodelinggrade C topical / D injectedSystematic review to March 2026 found 20 studies, of which 18 were preclinical and 2 were randomised²⁸. Cannot: justify injection. Zero human trials of injected GHK-Cu exist, and FDA flagged the injectable route specifically Community file: strong satisfaction record on both routes, weakest attribution in our sweep — overnight glow reports are a vehicle tell, not remodeling [the community record]

07LL-37human cathelicidin · wound healing, infectiongrade C topical / D systemicFirst-in-man topical on venous ulcers, n=34: healing roughly six-fold faster at 0.5 mg/mL, p=0.003³¹. Cannot: replicate. The phase IIb, n=148, found no significant improvement in the full population, and no systemic human study exists at all³²

08CJC-1295 + ipamorelinGH secretagogues, sold blended · growth hormone axisgrade C hormones / D outcomesCJC-1295 with DAC raised GH 2 to 10-fold and IGF-1 1.5 to 3-fold. Ipamorelin has one PK study, n=40, single IV dose³⁵. Cannot: show a clinical result. The only CJC outcome trial was terminated in 2006 after a participant death and never published; ipamorelin's ileus RCT missed at p=0.15³⁴

09SemaxACTH fragment analogue · stroke recovery, cognitiongrade C · Russia onlyOn Russia's Vital and Essential Drugs list since 2019. Best stroke study: n=110, non-randomised, unblinded, confounded with rehabilitation timing. Cannot: travel. Zero non-Russian replication, zero registered trials on ClinicalTrials.gov, all clinical papers in one journal

10Selanktuftsin analogue · anxietygrade C · Russia onlyListed in Russian drug references as registered nasal drops, 0.15%, ATC N05BX — confirmable only in a commercial reference, not the state register. Largest monotherapy comparison: n=62 versus medazepam, effects similar. Cannot: prove itself against placebo. Not one of the three clinical studies has a placebo arm, and the developer co-authored all three⁴¹

11Epitalonsynthetic tetrapeptide · telomeres, longevitygrade DIndependently replicated in cell culture at Brunel in 2025 — but only n=11 ex vivo in humans, with telomeres rising in 5 and falling in 2^39,40. Cannot: claim lifespan. Rats showed no lifespan effect under standard lighting, and no human dosing trial has ever been published

12NAD+, injectedcofactor · anti-aging, energygrade DA 2026 PRISMA review of 113 studies found no outcomes trial of intravenous or intramuscular NAD+, ever, for any anti-aging indication³⁷. Cannot: do what it says. The one PK study found infused NAD+ rapidly and completely removed from the plasma for at least the first 2 hours

13BPC-157gastric pentadecapeptide · tendon, gut, joint healinggrade DNo published randomised trial in humans, any indication. The total human record is an n=12 open-label bladder pilot, an n=2 IV safety report, and an n=12 retrospective knee series²⁵. Cannot: point to a trial. The Pliva IBD programme is asserted in review articles by the discovering group and produced no retrievable results Community file: adoption at industrial scale [108 tracked vendors] and a two-sided tolerability record — modal report of nothing, a consistent minority cluster of anxiety, anhedonia and GI reactions [the community record]

14TB-5007-residue fragment · tendon and tissue repairgrade DZero human data on the molecule sold. Every trial used full-length thymosin β4, a 43-mer, and those largely missed their endpoints²⁶. Cannot: borrow that dossier. TB-500 is Ac-LKKTETQ, seven residues, and the analytical literature states its effects have not been documented Community file: rides with BPC-157 in the "Wolverine stack" folklore; the community record cannot separate the two compounds, and the fragment-vs-full-molecule problem above still applies

15KPVα-MSH tripeptide · gut inflammationgrade DTwo independent rodent colitis programmes and a clean PepT1 and NF-κB mechanism in vitro²⁷. Cannot: show up in a human. No trial of KPV exists anywhere on ClinicalTrials.gov — not a phase 1, not a case series

16MOTS-cmitochondrial-derived peptide · metabolic, exercise mimeticgrade DMouse administration data plus human correlation: exercise raises endogenous MOTS-c³⁶. Cannot: claim to be exercise in a vial. The one registered human trial was filed February 2026 by the same sponsor discredited elsewhere in this report, and reads out no earlier than 2027

17VIP, subcutaneousvasoactive intestinal peptide · gut and airway inflammationgrade DAviptadil is approved in Europe for erectile dysfunction — but as an intracavernosal product with phentolamine, a different route and formulation. Cannot: survive its own trials. NIH's TESICO, n=471, on IV aviptadil: mortality HR 1.04, P=0.78³³

### The approved tier

Tirzepatide is the strongest evidence in the catalogue and it is not close. A dual GIP and GLP-1 receptor agonist, approved for type 2 diabetes in May 2022, obesity in November 2023 and obstructive sleep apnea in December 2024.

SURMOUNT-1 randomised 2,539 people for 72 weeks and produced −20.9% body weight at the top dose¹⁸. SURMOUNT-5 beat semaglutide head-to-head, −20.2% versus −13.7%²⁰. A 13,299-patient cardiovascular outcomes trial met non-inferiority against dulaglutide and narrowly missed superiority.

The honest limits: discontinuation for adverse events is consistently higher than comparators, with a pooled relative risk of 1.32.

And the lean mass number is real — in the DXA substudy, roughly a quarter of the weight lost was lean tissue, a 10.9% reduction over 72 weeks¹⁹. The proportion is no worse than dieting. The absolute loss is much larger, because the total loss is much larger.

Tesamorelin is a stabilised GHRH analogue and the only growth-hormone-axis compound in this catalogue with an approval. That approval is narrow and specific: reduction of excess abdominal fat in HIV-infected adults with lipodystrophy, 2010.

Two phase 3 trials of 412 and 404 patients showed visceral adipose tissue falling 15.2% and 10.9% while subcutaneous fat was untouched²²; a pooled analysis of 806 randomised patients put the treatment effect at 15.4%. A 2019 trial in HIV-associated fatty liver, n=61, showed hepatic fat fraction down 37% relative²⁴.

Three things the label says that marketing does not²³. It is not indicated for weight loss — the drug is weight-neutral.

The benefit reverses: patients re-randomised to placebo regained 22 to 24 cm² of visceral fat. And while group-mean glucose did not move, 5% of treated patients versus 1% on placebo crossed HbA1c 6.5% by week 26, a hazard ratio of 3.3.

IGF-1 exceeded two standard deviations in 47% of patients, and the label states the consequences of prolonged elevation are unknown.

### The nearly-there tier

Retatrutide adds a glucagon receptor to the GIP and GLP-1 pair. The peer-reviewed phase 2, n=338, delivered −24.2% at 48 weeks²¹.

Four phase 3 trials have completed, with reported figures reaching −28.3% at 80 weeks and −30.3% at 104.

It grades B rather than A for two reasons: it is approved nowhere, with an FDA filing planned for the first quarter of 2027, and not one phase 3 trial has been peer-reviewed or posted results. Every number in circulation comes from a sponsor press release.

There is also a tolerability signal that did not appear in phase 2: dysesthesia — abnormal or painful touch sensation — running dose-dependently up to 20.9% at 12 mg against 0.7% on placebo, with discontinuation for adverse events reaching 18.2% at the top dose.

Thymosin alpha-1 is the instructive case in this whole report. It has more clinical depth than any other non-GLP-1 compound here: approvals its manufacturer reports across 30-plus countries — though not in the United States — dozens of trials, a genuine mechanism demonstrated in humans.

And its best-powered modern trials came back flat. The 1,106-patient TESTS sepsis trial found 28-day mortality hazard ratio 0.99, P=0.93, with no secondary outcome differing²⁹. A 552-patient hepatitis C phase 3 found sustained virological response 12.73% versus 10.47%, p=0.407.

A meta-analysis of 5,352 COVID patients gave mortality RR 1.03³⁰. Hepatitis B is the one place it holds a B-minus, and even there the pivotal blinded Western trial missed at P=0.084 and its own authors wrote that the results do not confirm observations of treatment efficacy reported in other clinical studies.

Kisspeptin-10 sits on one of the best-established mechanisms in this document — inactivating GPR54 mutations cause hypogonadotropic hypogonadism in humans, which is about as clean as target validation gets. Acute stimulation of LH, FSH and testosterone is replicated across at least six independent human studies.

It stops short of B because every one of them is small — n=4 to 29 — and none is a powered randomised trial. It is the best-replicated C in this ledger. The problem is time. Twice-daily dosing in women with hypothalamic amenorrhoea produced complete desensitisation by day 14.

The longest human exposure in the literature is eight weeks of twice-weekly dosing, in cohorts of five, with a 12-day intermittent study in seven men as the longest run of daily exposure⁴². Two phase 2 trials of Takeda's kisspeptin-receptor agonist TAK-448 were terminated for failing their primary endpoints.

### The thin-but-real tier

GHK-Cu is a copper-binding tripeptide whose collagen and glycosaminoglycan effects are plausibly established in preclinical work. A PRISMA review current to March 2026 found the entire aesthetic-medicine evidence base to be 20 studies, of which two were randomised trials²⁸. The topical case is thin but real.

The injectable case does not exist — no human trial of injected GHK-Cu has ever been run, and FDA drew its safety line in exactly the same place the evidence does. The widely repeated resets 4,000 genes framing traces to narrative review articles, not to experiments with clinical outcomes.

LL-37 is the human cathelicidin, and it is the clearest example in this catalogue of a compound that got better trials than most and then failed them. The first-in-man topical study on venous leg ulcers, n=34, was genuinely positive, with healing roughly six-fold faster at 0.5 mg/mL³¹.

But the dose-response was non-monotonic — the highest dose was no better than placebo — and the confirmatory phase IIb, n=148, found no significant improvement in the full study population³².

Worth knowing before injecting it: LL-37 is the standard agent used to induce rosacea-like inflammation in mouse models. It is not unidirectionally good.

CJC-1295 and ipamorelin are usually sold as a pair, and the pairing hides a problem. Every published human trial under the CJC-1295 name used the DAC version, with a half-life of 5.8 to 8.1 days³⁵.

What is typically sold as CJC no-DAC is a different pharmacokinetic animal entirely, and has no human interventional trial at all.

Even the DAC trials measured only serum hormones — no body composition, no strength, no sleep, no clinical endpoint. The one trial that measured an outcome, a phase 2 in HIV visceral obesity, was terminated in July 2006 after a participant death and never published its results.

Ipamorelin's own human record is one 40-subject PK study and a phase 2 in postoperative ileus that missed at 25.3 versus 32.6 hours, p=0.15³⁴; a 320-patient successor completed in 2014 and has never reported.

Semax and selank are the pair that most needs its context stated rather than argued. Both are real registered medicines in Russia — semax on the state Vital and Essential Drugs list since 2019, selank listed in Russian drug references as registered nasal drops.

That is a genuine regulatory fact and it is not nothing. But every clinical study for either compound is Russian-language, in the same journal, with the developer as a co-author, and none of selank's three anxiolytic studies has a placebo arm.

There are zero registered trials for either on ClinicalTrials.gov, and zero non-Russian clinical replication. A US pharmacology review characterised selank bluntly as one of the poorly studied Russian drugs inexplicably sold to US consumers as dietary supplements⁴¹.

### The mechanism tier

These six are sold on stories that are mechanistically coherent and clinically untested.

**fig 05**The fragment. Every trial ran on the 43-residue protein. What the market sells is seven residues from its actin-binding site, and no human study has ever bridged the gap.

BPC-157 carries the largest gap between market presence and evidence of anything here. The most recent independent systematic review screened from inception to June 2024, found 36 includable studies, and reported 35 preclinical and one clinical — that one retrospective, not randomised²⁵.

Its authors wrote that no clinical safety data were found. Only three BPC-157 records exist on ClinicalTrials.gov in total, and the one randomised trial among them belongs to a sponsor whose own registry portfolio includes a study explicitly titled Mock Study and re-registrations of large commercial trials it does not plausibly run. Registration on ClinicalTrials.gov is self-submitted. It is not vetting.

TB-500 is the cleanest documented evidence-transfer failure in the market. Thymosin beta-4 is a 43-amino-acid endogenous protein, and every trial — the ocular programme covering more than 1,600 patients, the wound trials, the cardiac work — used the full-length molecule.

TB-500 as sold is Ac-LKKTETQ, seven residues corresponding to the actin-binding site²⁶. FDA uses the distinction in its own compounding list. Any page citing thymosin beta-4 trial data to sell TB-500 has crossed a molecular boundary that has never been bridged in a human study.

And the borrowed dossier is not even strong: three phase 3 ocular trials missed their co-primary endpoints, and the one randomised cardiac trial, n=96, was negative on its overall comparison.

KPV has the best preclinical case of any D-grade compound in this report. The PepT1 uptake mechanism is properly demonstrated, NF-κB inhibition is a real finding from a real experiment in Gastroenterology, and two independent rodent colitis programmes in immunologically distinct models both showed benefit²⁷.

And then it stops. There is no human trial of KPV anywhere — not a phase 1, not a case series, not a registry entry.

Note also what the recent literature is about: almost all post-2016 KPV work is nanoparticle and hydrogel delivery science, which is what a field looks like when getting the free peptide to its target is the unsolved problem.

MOTS-c is a 16-amino-acid peptide encoded inside mitochondrial DNA, acting through AMPK³⁶.

The exercise-mimetic claim rests on administration in mice and correlation in humans — exercise raises endogenous MOTS-c, which is the reverse inference from the one being sold.

As of today there is no completed human interventional trial, no human efficacy data, no human safety data and no published human pharmacokinetics. The one registered human trial was filed in February 2026 — by the same sponsor whose BPC-157 entry is picked apart above, so treat even that as unconfirmed.

Epitalon requires a distinction most coverage misses. Epithalamin is a bovine pineal extract. Epitalon is a synthetic tetrapeptide designed from its amino acid composition. Every human clinical study we located used the extract, not the tetrapeptide.

The telomerase claim traces to a three-page 2003 note in a Russian journal reporting no sample size and no statistics⁴⁰. The rat lifespan work found no effect under standard lighting conditions.

There is one genuinely independent replication — a 2025 Brunel University study confirming telomere extension in cultured human cells, which carries a published figure-substitution correction³⁹ — and the part nobody quotes is that in cancer cell lines it worked through ALT activation, a telomere-maintenance mechanism used by roughly 10 to 15% of human cancers.

A compound that lengthens telomeres in malignant cells is a safety question, not a selling point.

NAD+ injected is the most confidently marketed compound with the least behind it. A 2026 PRISMA systematic review searching January 2010 to October 2025 across 113 studies stated flatly that no eligible outcomes trial has ever evaluated intravenous or intramuscular NAD+ for any anti-aging or wellness indication³⁷.

The one pharmacokinetic study found infused NAD+ is cleaved so rapidly that plasma levels do not rise for two hours.

Oral precursors are a genuinely different question with genuine data: nicotinamide riboside and NMN both reliably raise blood NAD+, and that target engagement is replicated. What raising it accomplishes is another matter, and the trials are below.

VIP graded honestly is two different compounds. Aviptadil combined with phentolamine, delivered intracavernosally, is an approved European erectile-dysfunction product with real efficacy data.

Aviptadil injected or infused systemically is a different story: NIH's TESICO trial, n=471, found no benefit in COVID respiratory failure, with the safety point estimates running the wrong way³³.

Inhaled aviptadil has one positive multicentre RCT, n=80, at p=0.049, which drew published methodological challenges, while every other inhaled trial was terminated or withdrawn. For pulmonary hypertension there has been no controlled chronic trial since the eight-patient open-label study in 2003.

What doesn't work

Not thin evidence. Claims that adequately powered human trials have already killed.

This section is the one that matters. These are not compounds with thin evidence. These are claims that adequately powered human trials have already killed.

Thymosin alpha-1 for sepsis. TESTS, 22 centres, 1,106 patients, double-blind, placebo-controlled. 28-day all-cause mortality 23.4% versus 24.1%, hazard ratio 0.99, P=0.93²⁹.

No secondary outcome differed. The earlier positive signal was single-blind with a confidence interval crossing 1, and pooled benefit in meta-analysis disappears once you restrict to high-quality trials — the classic signature of small-study effects.

Thymosin alpha-1 for hepatitis C and COVID-19. Phase 3, n=552: SVR 12.73% versus 10.47%, p=0.407. COVID meta-analysis, 5,352 patients: mortality RR 1.03, and the authors wrote that their results do not support the use of it in hospitalised adults³⁰.

Ipamorelin for postoperative ileus. Randomised, double-blind, placebo-controlled phase 2. Time to tolerating solid food: 25.3 hours versus 32.6, p=0.15³⁴. FDA's own assessment concluded the class has not been shown to improve postoperative ileus management. The 320-patient follow-up never reported, and the programme stopped.

Intravenous aviptadil for COVID-19. TESICO, NIH-run, n=471. Day-90 recovery odds ratio 1.11, P=0.54. Mortality hazard ratio 1.04, P=0.78³³. The 2025 meta-analysis of both randomised trials gives survival OR 1.01, p=0.93. Uncontrolled case series in the same literature reported 88.9% survival, which is a textbook demonstration of why case series mislead.

Oral nicotinamide riboside for insulin sensitivity. n=40, 12 weeks, 2,000 mg daily in obese sedentary men. Insulin sensitivity, endogenous glucose production, glucose disposal, glucose oxidation, resting energy expenditure, lipolysis, lipid oxidation and body composition — all unimproved³⁸. A clean, adequately designed null.

Oral NR for cognition. n=20 with mild cognitive impairment. Blood NAD+ rose 2.6-fold, p<0.001. Cognition did not move. The authors: NR did not alter cognition. Biology moved. The endpoint did not. That gap is the single most useful thing to hold in mind when reading any biomarker claim.

Broad metabolic benefit from oral NMN. A 2026 meta-analysis of 15 trials, doses 250 to 2,000 mg daily: no significant effect on body weight, BMI, fasting glucose, HbA1c, lipid profiles or systolic blood pressure. Diastolic pressure fell slightly. That is the whole result.

And one claim that is not a compound at all: that anything was legalised in 2026. It was not. Removal from Category 2 confers no compounding eligibility.

The July advisory vote is non-binding. Rulemaking has not begun. As one law firm's post-vote analysis put it, these peptides still cannot be lawfully compounded, and FDA can continue to take enforcement action.

One supply-chain number worth holding

Whether a compound works and whether the vial contains it are separate questions, and one preprint suggests the second fails often.

A preprint posted in April 2026 — not peer-reviewed, and that matters — analysed 6,441 consumer-marketed research peptide samples across fourteen compounds using a large independent testing dataset⁴³. Applying two acceptance frameworks, between 41.6% and 71.1% of samples failed basic quality criteria, and measurable endotoxin contamination was present in 15%.

Treat the figure as provisional until it clears peer review. But note what it is measuring: not whether these compounds work, which is the question the rest of this report answers. Whether the vial contains what the label says. Those are separate failures, and a compound can suffer both.

FAQ

Are peptides legal in the US in 2026?

It depends entirely on which peptide, and the catalogue splits three ways. Tirzepatide and tesamorelin are FDA-approved drugs available on prescription. Retatrutide is approved nowhere, with a filing planned for the first quarter of 2027.

Everything else in the standard research catalogue — BPC-157, TB-500, KPV, MOTS-c, epitalon, semax and the rest — are unapproved new drugs. They cannot be lawfully compounded, and they cannot lawfully be sold for human use.

Two events in 2026 are routinely misread as changing that and neither did: the April removal of twelve peptides from FDA's Category 2 list happened because the nominators withdrew their nominations, and the July advisory committee vote was non-binding with no proposed rule published since.

Selling with a research-use-only label changes nothing either; FDA has said so in near-identical language across the warning letters it has issued to peptide sellers.

Did the FDA approve BPC-157 in 2026?

No. Two separate things happened and both are routinely misreported as approval. In April 2026 BPC-157 was removed from FDA's Category 2 list, but that happened because the people who nominated it withdrew their nominations, which grants nothing — it moved the substance from inside the conversation to outside it entirely.

In July 2026 FDA's Pharmacy Compounding Advisory Committee voted 8 to 6 with one abstention to recommend adding it to the 503A bulks list, against the written recommendation of FDA's own review team, whose briefing document said the substance is considered not well-characterized and proposed not adding it.

That vote is non-binding. Changing the rule requires formal notice-and-comment rulemaking or an act of Congress, no proposed rule has been published, and counsel estimates run from 8 to 12 months at the optimistic end to 24 months or longer.

Is TB-500 the same as thymosin beta-4?

No, and this is the most consequential confusion in the market. Thymosin beta-4 is a 43-amino-acid endogenous protein, and every clinical trial ever run — the ocular programme covering more than 1,600 patients, the wound trials, the cardiac work — used the full-length molecule.

TB-500 as sold is Ac-LKKTETQ, a seven-residue fragment corresponding to the actin-binding site.

FDA uses the same distinction in its own compounding listings, and the analytical chemistry literature states directly that the fragment's biological effects have not been documented. Any page citing thymosin beta-4 trial data to sell TB-500 has crossed a molecular boundary that no human study has ever bridged.

It is also worth noting that the borrowed dossier is not strong even on its own terms: three phase 3 ocular trials missed their co-primary endpoints, and the one randomised cardiac trial in 96 patients was negative overall.

Does injectable NAD+ work?

There is no controlled human outcomes trial of injected NAD+ for any anti-aging or wellness indication. A 2026 PRISMA systematic review searching January 2010 to October 2025 across 113 studies stated flatly that no eligible outcomes trial has ever evaluated intravenous or intramuscular NAD+ for these purposes.

The single pharmacokinetic study that exists found infused NAD+ is cleaved so rapidly that plasma levels do not rise for at least the first two hours, which directly contradicts the mechanism it is marketed on.

Oral precursors are a genuinely different question with genuine data behind them: nicotinamide riboside and NMN both reliably raise blood NAD+, and that target engagement has been replicated.

What raising it accomplishes is another matter — a 12-week trial of 2,000 mg daily nicotinamide riboside in obese men improved nothing measured, and a cognition trial saw NAD+ rise 2.6-fold while cognition did not move.

Which peptides actually have human trials behind them?

Tirzepatide and tesamorelin hold FDA approvals with adequately powered phase 3 programmes: SURMOUNT-1 randomised 2,539 people for 72 weeks, and tesamorelin's two phase 3 trials enrolled 412 and 404. Retatrutide has a peer-reviewed phase 2 of 338 people and four completed phase 3 trials, none of which has published or posted results.

Thymosin alpha-1 has more clinical depth than any other non-GLP-1 compound here — a 1,106-patient sepsis trial and a 552-patient hepatitis C trial — and both of those missed, which is why depth and strength are not the same thing.

Kisspeptin-10 has acute human data replicated across at least six studies, but every one is small and none is chronic. Everything else in the standard catalogue rests on animal models, in-vitro work, or small uncontrolled series.

Why do so many of these grade D?

Because a D on this ladder means the evidence is animal, in-vitro, mechanistic or anecdotal, with no controlled human outcome — and for most of this catalogue that is an accurate description rather than a judgment.

BPC-157, KPV and MOTS-c all have coherent, well-executed preclinical work behind them. KPV in particular has a properly demonstrated PepT1 uptake mechanism, real NF-κB inhibition published in Gastroenterology, and two independent rodent colitis programmes in immunologically distinct models.

What none of them has is a human being in a controlled trial: there is no KPV trial anywhere on ClinicalTrials.gov, not a phase 1 and not a case series.

Grading them higher would require pretending that rodent data transfers reliably to humans, and it does not. Seven of seventeen at D is not us being harsh. It is the field.

References

All identifiers below were retrieved and verified. Where a claim could not be confirmed against a primary source, it has been softened or omitted rather than cited loosely.

IUPAC Gold Book, peptides [entry P04479] — DOI 10.1351/goldbook.P04479
FDA Guidance, The Deemed To Be a License Provision of the BPCI Act: Q&A, March 2020 — fda.gov
Wang L et al. Therapeutic peptides: current applications and future directions. Signal Transduct Target Ther 2022;7:48 — PMID 35165272
Baral KC, Choi KY. Barriers and strategies for oral peptide delivery. Pharmaceutics 2025;17:397 — PMID 40284395
FDA Guidance, ANDAs for Certain Highly Purified Synthetic Peptide Drug Products, October 2017 — fda.gov
USP General Chapter <71> Sterility Tests; USP <85> Bacterial Endotoxins Test
FDA, Bulk Drug Substances Nominated for Use in Compounding Under Section 503A — fda.gov
FDA, Certain Bulk Drug Substances That May Present Significant Safety Risks — fda.gov
90 FR 1136 — Compounding Using Bulk Drug Substances Under Section 503A, final guidance, 7 Jan 2025 — govinfo.gov
91 FR 20465 — PCAC meeting notice, Docket FDA-2025-N-6895, 16 Apr 2026
FDA, BPC-157 PCAC briefing document, 11 May 2026 — fda.gov
FDA, Declaratory Order: Resolution of Shortages of Tirzepatide Injection Products, 19 Dec 2024 — fda.gov
FDA, Declaratory Order: Resolution of Shortages of Semaglutide Injection Products, 21 Feb 2025 — fda.gov
FDA, Import Alert 66-80, Detention Without Physical Examination of GLP-1 Receptor Agonist Bulk Drug Substances — accessdata.fda.gov
CBP, Cincinnati CBP foils scheme to smuggle over 5,000 unapproved peptides, 31 Mar 2026 — cbp.gov
Louisiana SB 253 / Act No. 374, signed 22 May 2026, effective 1 Aug 2026
LegitScript, Understanding Peptides: A Q&A Guide for Payment Processors, Oct 2025 — legitscript.com
Jastreboff AM et al. Tirzepatide Once Weekly for the Treatment of Obesity [SURMOUNT-1]. N Engl J Med 2022;387:205-216 — PMID 35658024
Body composition changes during weight reduction with tirzepatide, SURMOUNT-1 DXA substudy. Diabetes Obes Metab 2025 — PMID 39996356
Aronne LJ et al. Tirzepatide as Compared with Semaglutide [SURMOUNT-5]. N Engl J Med 2025;393:26-36 — PMID 40353578
Jastreboff AM et al. Triple-Hormone-Receptor Agonist Retatrutide for Obesity, Phase 2. N Engl J Med 2023;389:514-526 — PMID 37366315
Falutz J et al. Metabolic effects of a growth hormone-releasing factor in patients with HIV. N Engl J Med 2007 — PMID 18057338
EGRIFTA SV prescribing information — accessdata.fda.gov
Stanley TL et al. Effects of tesamorelin on non-alcoholic fatty liver disease in HIV. Lancet HIV 2019;6:e821-e830 — PMID 31611038
Vasireddi N et al. BPC-157 systematic review. HSS J 2025;21:485-495 — PMID 40756949
Rahaman KA et al. Simultaneous quantification of TB-500 and its metabolites. J Chromatogr B 2024;1235:124033 — PMID 38382158
Dalmasso G et al. PepT1-mediated tripeptide KPV uptake reduces intestinal inflammation. Gastroenterology 2008;134:166-178 — PMID 18061177
Mokhtar J et al. The Regenerative Potential of GHK-Cu in Aesthetic Medicine. Aesthet Surg J 2026 — PMID 42619529
Wu J et al. The efficacy and safety of thymosin α1 for sepsis [TESTS]. BMJ 2025;388:e082583 — PMID 39814420
Shang W et al. Thymosin alpha-1 in COVID-19: meta-analysis. Int Immunopharmacol 2023;114:109584 — PMID 36527881
Grönberg A et al. Treatment with LL-37 is safe and effective in enhancing healing of hard-to-heal venous leg ulcers. Wound Repair Regen 2014;22:613-621 — PMID 25041740
Mahlapuu M et al. Evaluation of LL-37 in healing of hard-to-heal venous leg ulcers. Wound Repair Regen 2021;29:938-950 — PMID 34687253
Brown SM et al. Intravenous aviptadil and remdesivir for COVID-19 [TESICO]. Lancet Respir Med 2023;11:791-803 — PMID 37348524
Beck DE et al. Ipamorelin for postoperative ileus. Int J Colorectal Dis 2014;29:1527-1534 — PMID 25331030
Teichman SL et al. Prolonged stimulation of GH and IGF-I secretion by CJC-1295. J Clin Endocrinol Metab 2006;91:799-805 — PMID 16352683
Lee C et al. The mitochondrial-derived peptide MOTS-c promotes metabolic homeostasis. Cell Metab 2015;21:443-454 — PMID 25738459
Gallagher C, Emmanuel OO. NAD+ supplementation for anti-aging and wellness: PRISMA-guided systematic review. Ageing Res Rev 2026;116:103057 — PMID 41655607
Dollerup OL et al. A randomized placebo-controlled clinical trial of nicotinamide riboside in obese men. Am J Clin Nutr 2018;108:343-353 — PMID 29992272
Al-Dulaimi S et al. Epitalon increases telomere length in human cell lines. Biogerontology 2025;26:178 — PMID 40908429
Khavinson VK et al. Effect of Peptide AEDG on Telomere Length and Mitotic Index of Human Blood Lymphocytes. Bull Exp Biol Med 2019;168:141-144 — PMID 31761987
Doyno CR, White CM. Sedative-Hypnotic Agents That Impact GABA Receptors: Focus on Selank. J Clin Pharmacol 2021;61:S114-S128 — PMID 34396551
Yeung AC et al. Chronic subcutaneous kisspeptin-10 stimulates gonadotropin secretion for 12 days in healthy men. Eur J Endocrinol 2026;195:206-216 — PMID 42549827
Mendias CL, Awan TM. Evaluation of Research Grade Peptides Marketed Directly to Consumers. Preprint, April 2026 — DOI 10.20944/preprints202604.1748.v1 [not peer-reviewed]

Inside Your Peptides is independent. We sell nothing. We disclose every referral relationship where one exists. The report above contains no vendor link; the sourcing desk that follows it is separate, and disclosed. Grades and rankings follow the published criteria in our editorial policy, never referral terms.

This report is for research and educational purposes only. It is not medical advice. Nothing here is a dosing recommendation or a suggestion to obtain, possess or administer any compound. Several substances discussed are unapproved, prescription-only, or subject to active regulatory proceedings. Speak to a qualified clinician before making any decision about your health.

Peptides in 2026, graded.