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Compare compounds, understand the differences, and explore the original studies behind them.
Research reviewed October 15, 2026. Start with the overview, then explore the evidence and sources.
Stages summarize the study designs available for the identified material in this selection. Human stages require studies in which people received that material; measuring the body’s own peptide or testing a different analogue does not qualify. Controlled studies can measure hormone responses or other biological changes, as well as clinical outcomes. A higher stage can include unsuccessful trials; the adjacent summary explains the findings and limitations.
Multiple reports from one trial count as one study for this classification. The selected-report totals below describe library coverage. Outcome-specific certainty would require a separate assessment of study limitations, consistency, applicability, precision and publication bias.
Epitalon is the four-amino-acid peptide Ala-Glu-Asp-Gly (AEDG), with free ends shown as H-Ala-Glu-Asp-Gly-OH.
Thymosin α1; thymalfasin is the chemically synthesized peptide
Epitalon is studied in telomere biology, animal aging and melatonin-related physiology. A small human study measured a melatonin breakdown product and genes involved in daily body rhythms. Human longevity reports using the pineal extract Epithalamin concern a different preparation.
Thymosin α1 is studied as an addition to conventional sepsis care and in chronic hepatitis B. Sepsis trials follow survival and immune-cell measurements; the hepatitis study tests sustained changes in viral markers. Laboratory work investigates how the peptide changes immune-cell responses.
The categories describe the most advanced study designs selected for this library. Each summary explains what was measured and what remains uncertain.
One controlled human study
One small placebo comparison in women, mainly night-shift workers, reported increased urinary levels of a melatonin breakdown product and changes in genes involved in daily rhythms. Sleep and survival were unmeasured; blinding and safety reporting were unclear. The mouse lifetime study did not establish an increase in mean lifespan. Human Epithalamin-extract results concern a different preparation.
Multiple controlled human studies
ETASS recorded fewer deaths with thymosin α1 plus standard sepsis care than standard care alone; the difference was uncertain. In TESTS, deaths were slightly less frequent than with placebo, without established survival benefit. In hepatitis B, more recipients had sustained undetectable viral DNA and a negative viral-protein test at follow-up than with placebo; that difference was also uncertain.
Extract composition, defined peptide sequence and salt form determine which studies belong to each material.
Epithalon/Epitalon is the four-residue sequence AEDG. Its free base and acetate are separate forms. Epithalamin is a pineal extract; the older mortality report of that extract cannot establish a synthetic-AEDG effect.
Thymosin alpha-1 is an N-acetylated 28-residue peptide, with thymalfasin its synthetic counterpart. Thymalin is a separate thymus extract. Its older longevity observations cannot be assigned to thymosin alpha-1.
Telomere maintenance and immune-cell regulation involve different systems and measurements.
The corrected 2025 study found longer telomeres, the protective structures at chromosome ends, and increased activity of telomerase, an enzyme that maintains those ends, in normal-cell cultures after three weeks relative to untreated controls. Breast-cancer cell lines showed a different maintenance response involving alternative telomere lengthening.
Human and murine dendritic-cell experiments linked thymosin alpha-1 to immune priming and regulatory effects involving tryptophan breakdown, the inflammation-restraining signal IL-10 and regulatory T cells that help limit immune responses. The response included control of inflammation rather than uniformly raising immune activity.
Human biomarker changes and survival during sepsis are distinct outcomes; neither supplies a head-to-head anti-aging comparison.
FDA describes forty women with low urinary melatonin-metabolite values assigned to AEDG or saline placebo, with thirty-five additional age-normal reference women. After twenty days, metabolite output rose 1.7-fold with AEDG and remained unchanged with placebo. Sleep outcomes and systematic safety were not reported.
The corrected TESTS trial randomized 1,106 adults with sepsis and analyzed 1,089 who received study drug. By day twenty-eight, deaths were 127/542 with thymosin alpha-1 and 132/547 with saline placebo: hazard ratio 0.97 (95% confidence interval 0.76–1.24; P=0.82), leaving a mortality benefit unestablished.
A measured human concentration profile is different from a response measured days later in cells or urine.
FDA identified preliminary rabbit fluorescent-label distribution information without demonstrated specificity for intact Epitalon and no additional pharmacokinetic studies. The selected sources provide no validated human blood half-life.
In nine healthy volunteers comparing three subcutaneous formulations, serum concentrations peaked after one to two hours and elimination half-life was below three hours. Timosina produced higher exposure than Zadaxin and thymosin alpha-1-HLR, so this small study does not establish equivalence of every product.
Disease-specific safety follow-up and experimental aging findings cannot establish long-term safety or longevity in healthy adults.
The selected mouse study did not establish an increase in average lifespan, despite longer survival at the tail. The small human biomarker report lacked systematic safety data, and the cancer-cell telomere findings do not quantify cancer risk in people. FDA identifies substantial clinical and product-quality gaps.
In TESTS, any adverse event occurred in 66.4% with thymosin alpha-1 and 67.6% with placebo; serious events occurred in 26.8% and 29.3%. These differences remained uncertain during ninety-day follow-up in sepsis. FDA also identifies formulation and immune-reaction concerns for proposed compounded products.
The selected exact-peptide evidence provides little information about long-term clinical harms. Telomere maintenance is relevant to both normal-cell function and malignant-cell persistence. The cancer-cell results therefore leave a consequential safety question that requires further investigation; they supply no estimate of cancer incidence in exposed people.
Within TESTS's 90-day follow-up, at least one adverse event was reported in 360 of 542 active participants and 370 of 547 placebo participants. Serious events occurred in 145 and 160 participants, respectively. The study reported no unexpected serious event related to thymosin α1. These observations come from severely ill patients receiving trial material and extensive concurrent care. TESTS safety results.
These are selected reports; several reports can come from one trial or cohort. Counts describe this library’s coverage.
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Read how the compounds differ, what direct studies found, and which questions remain open.
BPC-157 has been studied in several animal injury models and a few small human reports. Research on the defined acetylated TB-500 fragment is largely analytical or laboratory work. A small 2026 rat study tested BPC-157 alongside a TB-500-labeled preparation, but the paper did not fully identify that preparation or establish a clear difference between the two compounds.
CJC-1295 with DAC was designed to bind albumin and prolong growth-hormone signaling, and early studies measured its persistence and hormone effects in healthy volunteers. Modified GRF(1–29) shares the modified GHRH core but lacks that extension; most selected reports concern chemical identification, leaving much less human pharmacology to compare.
Direct trials found greater average weight and blood-glucose reductions with tirzepatide at the formulations tested. Receptor biology, available products, approved uses, cardiovascular outcomes and tolerability add context when comparing the two medicines.
Liraglutide and semaglutide activate the same GLP-1 receptor. Direct trials found larger average weight and blood-glucose reductions with semaglutide under the protocols tested. The comparison explains those trials, formulation differences, tolerability and separate cardiovascular evidence.
ACHIEVE-3 directly compared oral orforglipron capsules with oral semaglutide tablets in adults with type 2 diabetes taking metformin. Orforglipron lowered average blood glucose more. More participants reported stomach or intestinal adverse events or stopped treatment because of adverse events, and the average pulse increase was larger with orforglipron. The results concern the trial formulations and strengths; weight-management products need separate context.
Dihexa is a defined synthetic peptidomimetic with rodent research and important publication warnings. Cerebrolysin is a porcine-brain-derived mixture with randomized human trials, including favorable rehabilitation findings and unsuccessful acute-stroke comparisons. There is no direct trial establishing which is more effective or safer, and neither a shared brain-research theme nor separate study results makes the preparations interchangeable.
Semax is a seven-amino-acid peptide with small human neurological and brain-imaging reports. Dihexa is an angiotensin-IV-derived peptidomimetic with rodent research, a formal concern on its early pharmacology report and a retracted mechanism paper. Their separate studies do not establish which improves human memory more, and neither record provides a dependable human half-life comparison.
Epitalon studies focus on telomere maintenance, while FOXO4-DRI studies test removal of senescent cells. Separate mouse results, failed cartilage improvement and a pulmonary-vessel harm signal do not establish which would improve human aging. Neither has a validated human blood half-life in the sources reviewed here.
FOXO4-DRI experiments test senescent-cell clearance; MOTS-c experiments examine metabolic adaptation and physical capacity. Separate mouse results and human endogenous-MOTS-c measurements do not establish a clinical aging or fitness ranking. A pulmonary-vessel harm signal for FOXO4-DRI and major native-MOTS-c safety gaps remain consequential.
Retatrutide activates GIP, GLP-1 and glucagon receptors; semaglutide activates GLP-1 receptors. Separate placebo-controlled obesity trials found substantial weight loss with each, but their percentages cannot establish which works better in a shared population. Semaglutide has approved products and cardiovascular-outcome evidence. Retatrutide remains investigational, with a direct semaglutide diabetes comparison registered but no result report located for this review.
Three direct trials have preliminary sponsor results. REDEFINE 4 in obesity failed to establish CagriSema noninferiority to tirzepatide for weight loss. In type 2 diabetes, higher-dose REIMAGINE 4 met weight noninferiority but failed the glucose criterion; lower-dose REIMAGINE 5 reported greater weight loss with CagriSema and met glucose noninferiority. Exact doses, populations and analysis assumptions determine what each result means.
GHK-Cu combines a three-amino-acid peptide with copper; BPC-157 is a separate fifteen-amino-acid peptide. GHK-Cu has been tested in specific topical skin and wound products, with mixed human results. BPC-157 has repair-related cell and animal findings and small human reports. No direct GHK-Cu–BPC-157 trial was identified, so these sources cannot establish which improves skin or injury recovery more.
Analytical studies identify TB-500 as the acetylated seven-amino-acid thymosin β4 fragment Ac-LKKTETQ. GHK-Cu is a copper-bound tripeptide studied in specific skin and wound preparations. TB-500 fragment findings involve analytical and cell studies; GHK-Cu has mixed human topical findings. Full-length thymosin β4 trials and ambiguously named products cannot establish a fragment-versus-GHK-Cu clinical ranking.
Semax and Selank are different seven-residue peptides with a shared Pro-Gly-Pro ending. Their patient studies addressed different conditions: stroke-related deficits for Semax and anxiety-related symptoms for Selank. A small study included both compounds and placebo in healthy participants, but measured brain-scan connectivity rather than clinical benefit. These sources cannot rank them as treatments for anxiety, cognition or stroke.
Oxytocin is an endogenous hormone with established obstetric uses; its sexual-function studies used particular nasal or vaginal preparations in distinct populations. Bremelanotide, also called PT-141, is a melanocortin-receptor agonist approved as Vyleesi for premenopausal women with acquired, generalized hypoactive sexual desire disorder. Separate trials cannot establish which is a better treatment for a shared patient group.
GHRP-6 and GHRP-2 are different six-residue peptides that stimulate growth hormone through the ghrelin-receptor system. Controlled GHRP-2 meal studies found greater food intake, while GHRP-6 has direct human peptide measurements and detailed endocrine experiments. These sources do not establish which produces more muscle, better recovery or a stronger appetite effect in a direct comparison.
Ipamorelin stimulates the ghrelin receptor; tesamorelin stimulates the growth hormone-releasing factor receptor. Ipamorelin’s bowel-surgery trial observed earlier meal tolerance but did not establish a benefit over placebo. Tesamorelin reduced visceral abdominal fat in adults with HIV lipodystrophy and has an approved product for that setting. Their trials do not establish relative muscle growth, recovery or general weight-loss effects.
BPC-157 and KPV have both been investigated in intestinal injury models, but they are different peptides with different experimental explanations. BPC-157, called BPC-15 in the rat report, reduced chemical colon injury when injected into the abdomen before the injury; KPV studies connected cellular peptide transport with reduced inflammation in mouse colitis. Neither literature establishes which is more effective or safer for human inflammatory bowel disease.
BPC-157 and LL-37 have been studied in wound-related research, but their results come from different settings. BPC-157 accelerated closure of chemical burns in rats. LL-37 has randomized topical ulcer trials in people: an early study found faster wound shrinkage, while the larger trial did not establish better complete closure overall. These sources do not compare the peptides directly or support a general healing ranking.
MOTS-c is a mitochondrial-encoded peptide studied in cells, mouse interventions and human measurements of the body’s own peptide. SS-31 is a development name for elamipretide, which acts at mitochondrial membranes and has controlled patient trials. Its large mitochondrial-myopathy trial did not establish better walking or fatigue, while its defined product has accelerated approval for muscle strength in Barth syndrome. These findings cannot rank the compounds for general energy, exercise or aging.
AOD9604 is a modified growth-hormone fragment whose oral obesity program failed to establish useful weight loss. Semaglutide activates the GLP-1 receptor and produced substantially greater weight reduction than placebo in STEP 1. No direct randomized comparison establishes their relative effect or safety; the informative contrast is between their different controlled human results.
Retatrutide activates GIP, GLP-1 and glucagon receptors; tirzepatide activates GIP and GLP-1 receptors. Both have substantial placebo-controlled weight-loss results, but the trials differ in duration, population and analysis. Retatrutide remains investigational in October 2026, and the registered direct TRIUMPH-5 comparison has no outcome result in the accessed official listing.
Retatrutide is one peptide activating GIP, GLP-1 and glucagon receptors. CagriSema combines the amylin analogue cagrilintide with semaglutide, a GLP-1 receptor agonist. Both have substantial placebo-controlled human weight-loss findings, including separate trials with type 2 diabetes, but no direct randomized comparison in the selected sources establishes which is more effective or safer. Both remain investigational as of October 2026.
CJC-1295 with a drug affinity complex (DAC) binds albumin, a blood protein, and stimulates the receptor for growth hormone-releasing hormone (GHRH). Small healthy-adult studies found prolonged growth hormone (GH) and insulin-like growth factor 1 (IGF-1) increases with this form. Ipamorelin acts through the ghrelin-receptor system; a human infusion study measured a shorter peptide half-life, and its bowel-surgery trial left clinical benefit uncertain. No cited trial establishes which improves muscle growth, recovery or longevity.
Hexarelin and ipamorelin stimulate growth hormone through the ghrelin-receptor system, but their research differs. Small human hexarelin experiments measured brief cardiac changes and a smaller growth hormone (GH) response during repeated exposure. Ipamorelin has animal selectivity data, a human infusion study and a postoperative trial with uncertain clinical benefit. These findings do not establish which provides better muscle growth or long-term safety.
Ipamorelin acts through the ghrelin-receptor system. Sermorelin is the amidated fragment containing the first twenty-nine residues of growth hormone-releasing hormone (GHRH) and stimulates its receptor. Ipamorelin’s postoperative trial left meal-tolerance benefit uncertain. Historical sermorelin research measured growth in children deficient in growth hormone (GH) and body composition in a small HIV study. Neither literature establishes superior healthy-adult muscle growth, recovery or anti-aging effects.
AOD-9604 is a modified fragment of growth hormone investigated for metabolic effects; its major oral obesity study did not establish greater weight loss than placebo. Tesamorelin stimulates growth hormone release and reduced fat around abdominal organs in adults with HIV and lipodystrophy. Its approved use concerns that specific fat distribution, with little overall weight change. The two compounds have not been compared directly in the selected trials.
Ipamorelin and GHRP-2 stimulate the ghrelin-receptor system. Their research differs: ipamorelin’s often-cited selectivity result comes from animals, and its human bowel-surgery trial left clinical benefit uncertain. GHRP-2 increased how much people ate in small controlled meal experiments. These findings do not establish a ranking for muscle growth, injury recovery or long-term safety.
Sermorelin is the amidated first twenty-nine residues of growth hormone-releasing hormone. Its studies include growth in children with diagnosed growth hormone deficiency. CJC-1295 with a drug affinity complex (DAC) is a modified albumin-binding analogue whose healthy-adult trials measured prolonged hormone increases. Their different molecular forms, populations and outcomes do not establish which improves adult strength, recovery or aging.
BPC-157 and ipamorelin intersect with growth-hormone biology at different points. BPC-157 increased growth-hormone receptors in rat tendon cells; ipamorelin stimulated growth-hormone release in human exposure research. BPC-157 also improved rat tendon-repair measurements, while ipamorelin’s postoperative meal-tolerance trial left benefit uncertain. These studies do not establish which improves human injury recovery or whether combining them helps.
GHK-Cu is a copper-bound tripeptide studied in connective-tissue biology and specific topical skin and ulcer preparations. Epithalon, also called Epitalon, is AEDG, a four-residue peptide studied in telomere maintenance and aging-related models. GHK-Cu’s human skin results vary by preparation and setting; Epitalon’s telomere findings do not establish human rejuvenation. No direct trial identified here ranks their effects on skin aging or longevity.
Epithalon, also called Epitalon, is the four-residue peptide AEDG studied in telomere and circadian biology. Thymosin alpha-1 is a separate N-acetylated 28-residue peptide with immune-cell experiments and controlled clinical trials. Its larger corrected sepsis trial did not establish a mortality reduction. Epitalon’s cellular and limited human-biomarker findings do not supply a human longevity benefit, and the two compounds have no direct clinical comparison in the sources reviewed here.
Bremelanotide and Melanotan II are related cyclic melanocortin peptides with different clinical evidence. The approved bremelanotide acetate injection improved desire and related distress in selected premenopausal women, while small Melanotan II studies measured pigmentation and acute erections in men. No selected head-to-head trial establishes a better or safer treatment.
Semax and bremelanotide are both short synthetic peptides related to hormone biology, but their studies ask different questions. Semax reports concern brain signaling and neurological illness; bremelanotide trials concern desire and related distress in premenopausal women with hypoactive sexual desire disorder, meaning persistent low desire that causes distress. No selected trial compares them for memory, stroke recovery or sexual symptoms.
Thymosin alpha-1 and LL-37 both participate in immune biology, but the selected clinical studies test different interventions. Thymosin alpha-1 was injected as an adjunct to sepsis care; synthetic LL-37 was applied to chronic leg ulcers. Larger trials did not establish the hoped-for overall mortality or ulcer-closure benefits, while earlier favorable findings and biological activity remain important to understand.