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Research library

Peptide research library — what the literature actually says.

A citation index for the compounds most often discussed in peptide research. Each entry states the evidence level, what published work establishes, what it does not, and links every reference straight to PubMed so you can read the primary source yourself.

How to use this page

Most peptide claims circulating online trace back to a handful of papers, and many of those papers are rodent studies presented as if they were clinical results. This index separates the two. 14 compounds, 19 references, every one openable on PubMed. Nothing here is a recommendation, a protocol or a dosing guide.

Compound index

Semaglutide

Human clinical trials

Also described as: GLP-1 receptor agonist

A long-acting glucagon-like peptide-1 (GLP-1) receptor agonist studied extensively in randomised controlled trials for glycaemic control and body-weight reduction.

What the literature supports

Large phase 3 programmes (SUSTAIN, STEP) report reductions in HbA1c and body weight versus placebo, with gastrointestinal effects as the most frequently reported adverse events.

What remains unestablished

Long-term outcomes beyond published trial windows, effects of weight regain after discontinuation, and effects outside strictly supervised clinical settings are areas of ongoing study.

Tirzepatide

Human clinical trials

Also described as: Dual GIP/GLP-1 receptor agonist

A single molecule that activates both the GIP and GLP-1 receptors, investigated in the SURPASS and SURMOUNT trial programmes.

What the literature supports

Published phase 3 data report dose-dependent reductions in body weight and HbA1c, with a tolerability profile dominated by gastrointestinal effects during dose escalation.

What remains unestablished

The relative contribution of GIP versus GLP-1 receptor activity to the observed effects remains an active research question.

Retatrutide

Human clinical trials

Also described as: Triple GIP/GLP-1/glucagon receptor agonist

An investigational triple-agonist peptide reported in phase 2 studies; not an approved medicine in any jurisdiction at the time of writing.

What the literature supports

Phase 2 results describe dose-dependent weight reduction over 48 weeks with a gastrointestinal-dominant adverse-event profile.

What remains unestablished

Phase 3 outcome data, long-term safety, and comparative effectiveness against dual agonists are not yet published.

BPC-157

Animal & in-vitro

Also described as: Body protection compound, pentadecapeptide

A synthetic peptide sequence derived from a fragment of human gastric juice protein, studied almost entirely in rodent models of tissue injury.

What the literature supports

Published rodent studies report effects on tendon, muscle and gastrointestinal healing endpoints, with proposed mechanisms involving angiogenesis and nitric-oxide signalling.

What remains unestablished

There are no large published randomised human trials. Pharmacokinetics, oral bioavailability and long-term safety in humans are unestablished.

GHK-Cu

Animal & in-vitro

Also described as: Copper tripeptide-1

A naturally occurring copper-binding tripeptide (glycyl-L-histidyl-L-lysine) studied mainly in dermatological and gene-expression contexts.

What the literature supports

In-vitro work reports modulation of a broad set of genes associated with tissue remodelling; topical cosmetic studies report skin-quality endpoints.

What remains unestablished

Systemic administration in humans is not well characterised, and copper-load considerations are rarely addressed in the available literature.

Thymosin beta-4 / TB-500

Animal & in-vitro

Thymosin beta-4 is an actin-sequestering peptide; TB-500 is a synthetic fragment of it used in laboratory work.

What the literature supports

Preclinical studies report roles in cell migration, angiogenesis and wound-repair models.

What remains unestablished

Human efficacy data are limited to small early-phase studies; the fragment and the full peptide are frequently conflated in non-scientific sources.

Ipamorelin

Animal & in-vitro

Also described as: Growth hormone secretagogue

A selective ghrelin-receptor agonist characterised in the late 1990s as a growth-hormone releasing peptide with limited effect on cortisol or prolactin.

What the literature supports

Original pharmacology work describes selective GH release in rodent and swine models.

What remains unestablished

There is no approved human indication and no long-term human safety dataset.

CJC-1295 / Tesamorelin

Human clinical trials

Also described as: GHRH analogues

Both are analogues of growth-hormone-releasing hormone. Tesamorelin has been studied in registered clinical trials; CJC-1295 in early pharmacokinetic work.

What the literature supports

Tesamorelin trials report reductions in visceral adipose tissue in HIV-associated lipodystrophy. CJC-1295 studies describe sustained elevation of GH and IGF-1 after single doses.

What remains unestablished

Outcomes in healthy populations, and long-term consequences of sustained IGF-1 elevation, are not established.

MOTS-c

Animal & in-vitro

Also described as: Mitochondrial-derived peptide

A peptide encoded in mitochondrial DNA, described as a regulator of metabolic homeostasis.

What the literature supports

The original characterisation reports effects on insulin sensitivity and AMPK signalling in mouse models.

What remains unestablished

Human dosing, bioavailability and clinical endpoints remain largely unstudied.

SS-31 / Elamipretide

Human clinical trials

A mitochondria-targeting tetrapeptide that associates with cardiolipin on the inner mitochondrial membrane.

What the literature supports

Mechanistic work describes stabilisation of cardiolipin and improved mitochondrial bioenergetics; several early-phase human trials have been conducted in mitochondrial disease.

What remains unestablished

Phase 3 efficacy has not been consistently demonstrated across indications.

PT-141 / Bremelanotide

Human clinical trials

A melanocortin-receptor agonist studied in randomised trials for hypoactive sexual desire disorder in premenopausal women.

What the literature supports

The RECONNECT phase 3 studies report modest improvements on validated desire and distress scales, with nausea and flushing as common adverse events.

What remains unestablished

Effects in other populations and with off-label dosing patterns are not characterised.

MK-677 / Ibutamoren

Human clinical trials

An orally active, non-peptide ghrelin-receptor agonist — often grouped with peptides despite being a small molecule.

What the literature supports

Year-long human studies report sustained increases in GH and IGF-1 and increases in fat-free mass, alongside increased appetite and reduced insulin sensitivity in some participants.

What remains unestablished

Functional outcome benefits have not been consistently demonstrated, and long-term metabolic consequences remain debated.

Epitalon

Early / limited

Also described as: Epithalon, AEDG tetrapeptide

A synthetic tetrapeptide investigated primarily by a small number of research groups in relation to telomerase activity and ageing models.

What the literature supports

In-vitro reports describe telomerase activation in human fibroblast cultures.

What remains unestablished

Independent replication is sparse, and the available human literature does not meet the standard of controlled clinical evidence.

Frequently asked questions

What does 'evidence level' mean on this page?+

Human clinical trials means randomised or controlled studies in people have been published. Animal & in-vitro means the published work is confined to laboratory or animal models. Early / limited means the literature is sparse or largely un-replicated.

Why are there no dosing instructions in this library?+

Because none of these materials are medicines and this site does not supply anything for human use. Dosing guidance would be clinical advice, which is outside the scope of an educational reference.

Why do animal results not transfer directly to humans?+

Rodent physiology differs in metabolic rate, receptor distribution and clearance. A positive rodent endpoint establishes a hypothesis worth testing, not an expected human outcome.

How should a reference be checked?+

Open the PubMed link, read the abstract's methods line first — species, sample size, control arm, duration — then read the limitations section of the full text. A citation is only as strong as its study design.

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