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The Book of Peptides

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Not medical advice

The Book of Peptides is not a clinic and not your doctor. We do not sell, prescribe, recommend, or personalize any compound, and no grade or ranking here is an endorsement. None of the compounds covered are approved for the uses described here by the U.S. FDA, Australia's Therapeutic Goods Administration (TGA), New Zealand's Medsafe, or the equivalent regulator in most other countries.

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Most are sold for laboratory research only, a few are prescription-only drugs, and some are controlled substances or banned in sport. Possessing or administering an unapproved compound outside an authorized setting may be unlawful wherever you live. Nothing here is a recommendation to buy, possess, or self-administer anything. Consult a licensed physician before any decision involving peptide use.

Most are sold for laboratory research only, a few are prescription-only drugs, and some are controlled substances or banned in sport. Possessing or administering an unapproved compound outside an authorized setting may be unlawful wherever you live. Nothing here is a recommendation to buy, possess, or self-administer anything. Consult a licensed physician before any decision involving peptide use.

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Book Three · Discovery stories

Knowledge & history

Every compound has an origin — a lab accident, a snail's venom, a Nobel snub. These are the discovery stories, and each “fun fact” carries a verdict on whether it actually happened the way it's told.

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Category
Category
Verdict
Metabolic & Fat-Loss · 6 stories
1992
01

Exendin-4

the drug we now know as Byetta / exenatide

The molecule that first proved the entire GLP-1 drug class could actually work was fished out of the venom of a Gila monster — a desert lizard that eats maybe five or six meals a year.

Embellished
2012
02

Semaglutide

why "Ozempic" is not the drug's real name

The drug class behind the world's biggest weight-loss boom was cracked open by a venomous desert lizard that can go months between meals without its blood sugar ever crashing.

Embellished
2009
03

Liraglutide

the daily shot before the weekly one

The chemist who engineered liraglutide — the molecule that became the blueprint for Ozempic — was originally hired by Novo Nordisk to work on laundry-detergent enzymes, with nothing to do with diabetes at all.

Embellished
2022
04

Tirzepatide

the "twincretin"

For nearly three decades, GIP was diabetes research's discarded hormone — some labs were even trying to block it, not boost it — until an Indiana University peptide chemist bet that fusing it into one molecule with GLP-1 would outperform either alone.

Embellished
1921
05

Insulin

the first modern peptide drug

Everyone knows insulin's discoverers sold the patent for a dollar. Almost no one can point to where Banting said it "belongs to the world" — and the dollar never made insulin cheap.

Embellished
2019
06

Retatrutide

the "triple-G"

Glucagon entered medicine in 1923 as an impurity — the hyperglycemic junk fouling early insulin extracts, named for driving blood sugar up. A century later, chemists built it into a diabetes drug on purpose.

Embellished
Healing & Recovery · 3 stories
1991
01

BPC-157

the "Wolverine peptide"

Officially, the "BPC" in BPC-157 stands for "Body Protection Compound" — but the Croatian scientists who isolated it during Yugoslavia's violent collapse privately called it "Boze Pomozi," meaning "God help us."

Embellished
1991
02

TB-500

Thymosin Beta-4, and a horse-racing doping scandal

The molecule now smuggled into racehorses under the street name "TB-500" spent its first decade as a case of mistaken identity — sequenced in 1981 as a thymic immune hormone, it turned out in 1991 to be a completely different, already-known protein wearing a lab-coat alias.

Embellished
1973
03

GHK-Cu

the copper peptide found in your own blood plasma

GHK-Cu wasn't discovered in a skincare lab — a UCSF grad student found it by bathing old human liver cells in young donors' blood plasma and watching them start acting young again.

Embellished
GH Secretagogues · 4 stories
1998
01

Ipamorelin

designed to be the "clean" one

Ipamorelin's family tree began with a working drug for a lock nobody had found yet — in the late 1970s, a Tulane opioid researcher noticed his painkiller peptides were quietly dumping growth hormone into pituitary cells, two full decades before science identified the receptor they pulled on or ghrelin, the hormone that normally pulls it.

Embellished
2005
02

CJC-1295

the modification that turned minutes into days

The DAC modification took growth hormone-releasing hormone's natural half-life — about seven to ten minutes — and stretched it to six to eight days, by chemically hijacking a ride on the same albumin protein that ferries fatty acids through your bloodstream.

Embellished
1990
03

Sermorelin

the GHRH analog that had an FDA-approved life and death

Scientists spent nearly two decades hunting for the hormone that tells the pituitary to release growth hormone — and it finally turned up not in the brain, where it belonged, but leaking out of a tumor in a patient's pancreas.

Verified
1996
04

MK-677

the failed osteoporosis drug that became a bodybuilding staple

Merck's chemists built a drug that perfectly fit a lock three years before anyone on Earth knew what the key looked like.

Embellished
Longevity & Cellular Health · 4 stories
1980s
01

Epitalon

Soviet science and the pineal gland

Epitalon was synthesized, patented, and studied for roughly thirty years as a "pineal longevity peptide" before anyone proved its four-amino-acid sequence was actually present in the pineal extract it was designed to mimic — that confirmation didn't arrive until a 2017 mass-spectrometry paper, from the very lab that invented it.

Embellished
1982
02

Thymalin

a Soviet military thymus extract

A drug now used in Russia to treat immune aging began as a classified Cold War project to keep Soviet submarine crews from aging too fast at their posts — and its raw material was calf thymus glands, a leftover from the Soviet meat industry.

Embellished
2015
03

MOTS-c

a hormone from the other genome

MOTS-c is written into the mitochondrial genome — but no mitochondrion can build it. Read with the organelle's own genetic code, the gene collapses into tandem start and stop codons, so the transcript has to be shipped out and translated by the cell's ordinary ribosomes.

Embellished
2004
04

SS-31

the painkiller that missed

Elamipretide began as a failed painkiller, spent a decade filed in the literature as a free-radical scavenger before the mechanism work reattributed its action to a lipid it binds, and reached the US market in September 2025 on a twelve-patient trial that had missed both of its primary endpoints.

Embellished
Muscle-Building · 2 stories
1992
01

IGF-1 LR3

the doping-scandal peptide

The "Long" in IGF-1 LR3 was never meant to make it stronger — those 13 extra amino acids, borrowed from pig growth hormone, were tacked on just to help the protein fold correctly inside a vat of E. coli; that they also blocked the very proteins that normally neutralize IGF-1, tripling its potency, was the accident.

Embellished
1997
02

Follistatin 344

the mice with double the muscle

In 1997 a Johns Hopkins geneticist deleted a single gene from a mouse and it grew up looking like a cartoon bodybuilder — roughly double the muscle of its littermates — because that gene, which he named "myostatin," turned out to be the body's own brake pedal on muscle growth.

Embellished
Immune-Modulating · 2 stories
1977
01

Thymosin Alpha-1

the other half of the thymus story

Thymosin alpha-1 and thymosin beta-4 were pulled from the exact same batch of calf-thymus extract and share nothing but a name — one is a 28-amino-acid immune peptide that switches on dendritic cells, the other a 43-amino-acid actin-binder whose day job is cell migration and tissue repair, not immune signaling.

Embellished
1995
02

LL-37

the antimicrobial peptide your own skin makes

Your skin manufactures its own antibiotic — two leucines opening a 37-residue chain, which is literally what "LL-37" means — and in psoriasis your immune system turns that very molecule into a weapon against you.

Embellished
Cognitive & Neuroprotective · 4 stories
1982
01

Semax

a Cold War stroke drug repurposed as a nootropic

Semax is a fragment of the same pituitary hormone that floods your body in a crisis — too short to set off the alarm, yet — as the 1984 paper that first studied it put it — "a stimulator of learning with prolonged action".

Embellished
1990s
02

Selank

Semax's calmer sibling

Selank's chief ingredient, tuftsin, wasn't named for anything Russian at all — it's named after Tufts University in Boston, where it was discovered in 1970.

Embellished
1949
03

Cerebrolysin

pig brains and Austrian pharmacology

The "brain drug" that longevity influencer Bryan Johnson injected on camera in 2024, sending it viral among biohackers, is at its chemical core a 1950s soup of enzymatically digested pig brains.

Embellished
1977
04

DSIP

the sleep factor with no gene

DSIP was named in 1977 for the brainwave it was supposed to produce, and when the question was last reviewed, nearly thirty years on, no gene, precursor or receptor had been found.

Embellished
Sexual Health & Hormonal · 4 stories
1996
01

PT-141

the accidental side effect of a tanning drug

A drug engineered to help a fair-skinned Arizona professor tan without sunlight and dodge melanoma ended up, purely by clinical accident, becoming the first on-demand FDA-approved treatment for low sexual desire in women.

Embellished
1980s
02

Melanotan II

the sunless-tan peptide that never got approved

Melanotan II was built to give pale, burn-prone skin a tan without the sun — it never got approved as a tanning drug, but two of its molecular offspring did: one now treats a rare light-sensitivity disorder, the other treats low sexual desire in women.

Embellished
1996
03

Kisspeptin

named after Hershey's Kisses

A gene named as an inside joke about a small-town chocolate factory turned out, seven years later, to be the master switch that starts human puberty.

Verified
1953
04

Oxytocin

the "love hormone"

The first peptide hormone humanity built from scratch was synthesized by a chemist who — by his own account — spent his wartime teenage summers milking cows, the one job oxytocin makes possible in the first place.

Embellished
Specialty & Bioregulators · 2 stories
1984
01

GHRP-6

the secretagogue that also made people hungry

Bowers spent roughly fifteen years insisting his lab-made peptide had to be mimicking a real hormone nobody had found yet — and in 1999 a Japanese team pulled that hormone out of ground-up rat stomachs and named it "ghrelin," after the Proto-Indo-European root for "grow."

Embellished
1990
02

AOD-9604

a fragment of a fragment

AOD-9604 flunked the one job it was built for — shrinking waistlines in a 536-person obesity trial — yet outlived that failure for nearly two decades, sold worldwide in gray-market fat-loss vials on the strength of trial data showing a safety profile indistinguishable from placebo.

Embellished