Compare the research, not the marketing.
The comparisons people ask about most — neutral, evidence-based, and free of recommendations.
BPC-157
A synthetic 15-amino-acid peptide derived from a partial sequence of a protein found in human gastric juice, studied for tissue repair and gut-related endpoints.
TB-500
A synthetic fragment of thymosin beta-4 (the actin-binding region), studied for cell migration and wound-healing endpoints.
How they differ
The two peptides are often grouped together as "healing" compounds but act through different proposed pathways. BPC-157 has been described in animal studies as upregulating growth-factor and nitric-oxide signaling and promoting angiogenesis, with reported effects on the VEGFR2 pathway and on tendon-derived fibroblast outgrowth. TB-500 is the synthetic fragment corresponding to the actin-binding domain of thymosin beta-4; the parent molecule regulates actin polymerization, which in preclinical models influences cell migration, angiogenesis, and inflammation. In short, BPC-157 is studied largely around cytoprotection and growth-factor signaling, while TB-500 is studied around actin dynamics and cell motility.
What the research says
Both compounds are supported almost entirely by in-vitro and rodent data, not human clinical trials. BPC-157 has a comparatively larger preclinical literature spanning gastrointestinal, tendon, ligament, and muscle injury models (much of it from a single research group led by Sikiric and colleagues), which reviewers have noted as a concentration of the evidence in relatively few labs. TB-500 research draws on the broader thymosin beta-4 literature; full-length thymosin beta-4 has been examined in early human studies for indications such as dry eye and dermal wounds, but the injectable TB-500 fragment sold for research use has minimal direct human data. Neither compound has an established human safety or efficacy profile from controlled clinical trials.
Most studied for
BPC-157 is most studied for gastrointestinal protection and musculoskeletal (tendon, ligament, muscle) repair in animal models. TB-500 is most studied for wound healing, cell migration, and cardiac and dermal tissue repair, largely extrapolated from thymosin beta-4 research.
Bottom line
Both BPC-157 and TB-500 are frequently paired in the "tissue repair" category, but their evidence bases are predominantly preclinical, and neither has completed human clinical trials establishing efficacy or safety. BPC-157 has a larger animal literature concentrated in a limited number of labs; TB-500 borrows credibility from the broader thymosin beta-4 record while having little direct human data itself. Both are Category 2 and appear on the FDA PCAC July 23-24, 2026 docket, where a non-binding vote will consider recommending them toward the 503A Bulks List; even a favorable vote is an early step, with a realistic timeline of 12-18 months minimum before any legal compounding availability.
Semaglutide
A GLP-1 receptor agonist approved as a finished pharmaceutical for type 2 diabetes and for chronic weight management.
Tirzepatide
A dual GIP and GLP-1 receptor agonist approved as a finished pharmaceutical for type 2 diabetes and for chronic weight management.
How they differ
Semaglutide is a single-agonist that activates the GLP-1 receptor, enhancing glucose-dependent insulin secretion, slowing gastric emptying, and acting on central appetite pathways. Tirzepatide is a dual agonist that activates both the GLP-1 receptor and the GIP (glucose-dependent insulinotropic polypeptide) receptor. The addition of GIP activity is the primary mechanistic distinction; in the published trial program this dual mechanism is associated with differences in metabolic and weight endpoints compared with GLP-1 agonism alone.
What the research says
Both are supported by large randomized controlled human trials, which is what separates them from the research-use-only peptides. Semaglutide's evidence includes the SUSTAIN (diabetes), STEP (weight management), and SELECT (cardiovascular outcomes) programs. Tirzepatide's evidence includes the SURPASS (diabetes) and SURMOUNT (weight management) programs. A head-to-head diabetes trial (SURPASS-2) reported greater A1c and body-weight reductions with tirzepatide than with a semaglutide comparator arm. Gastrointestinal effects (nausea, vomiting, diarrhea) are the most commonly reported adverse events for both classes in trials.
Most studied for
Semaglutide is most studied for glycemic control in type 2 diabetes, chronic weight management, and, more recently, cardiovascular risk reduction. Tirzepatide is most studied for glycemic control in type 2 diabetes and chronic weight management, with an expanding trial program in related metabolic conditions such as obstructive sleep apnea and heart failure with preserved ejection fraction.
Bottom line
Semaglutide and tirzepatide are both FDA-approved finished drugs with extensive randomized human trial evidence, which places them in a fundamentally different evidence tier from the unscheduled research peptides. They differ mechanistically in that tirzepatide adds GIP-receptor activity to GLP-1 agonism, and head-to-head trial data in diabetes reported larger reductions in A1c and body weight for tirzepatide. Both carry well-characterized gastrointestinal side-effect profiles. Neither is part of the 503A compounding-bulks conversation. This summary describes published trial findings and does not constitute medical advice.
CJC-1295
A synthetic analog of growth-hormone-releasing hormone (GHRH) designed for an extended half-life, studied for stimulating growth-hormone release.
Ipamorelin
A selective growth-hormone secretagogue (ghrelin-receptor agonist) studied as a pulsatile growth-hormone releaser.
MK-677 (ibutamoren)
An orally active, non-peptide ghrelin-receptor agonist studied for sustained increases in growth hormone and IGF-1.
How they differ
These three act on the growth-hormone axis through two different receptor systems. CJC-1295 is a GHRH analog that stimulates the pituitary via the GHRH receptor; its design extends the half-life relative to native GHRH. Ipamorelin and MK-677 both act on the ghrelin/growth-hormone-secretagogue receptor rather than the GHRH receptor. Ipamorelin is a peptide reported in preclinical work to be a selective secretagogue that raises growth hormone without strongly affecting cortisol or prolactin, and produces a pulsatile release. MK-677 is a non-peptide, orally bioavailable secretagogue that produces a more sustained elevation of growth hormone and IGF-1. GHRH-pathway and ghrelin-pathway agents are sometimes studied in combination in preclinical settings because they act on complementary receptors.
What the research says
The three differ notably in how much human data exists. CJC-1295 and ipamorelin are supported mainly by early pharmacology studies and preclinical work; the injectable versions circulating for research use lack large controlled efficacy or long-term safety trials. MK-677 (ibutamoren) has the most human pharmacology data of the three, having been evaluated as a pharmaceutical candidate in clinical studies examining growth hormone and IGF-1 levels, body composition, and older-adult and catabolic populations; reported effects in those studies include increased appetite, fluid retention, and changes in insulin sensitivity. None of the three is FDA-approved, and MK-677 remains an investigational compound that did not reach approval.
Most studied for
CJC-1295 is most studied for prolonging GHRH-driven growth-hormone release. Ipamorelin is most studied as a selective, pulsatile growth-hormone secretagogue with a comparatively clean receptor-selectivity profile in preclinical work. MK-677 is most studied for orally sustained elevation of growth hormone and IGF-1, with human research touching on body composition, appetite, and conditions involving muscle loss.
Bottom line
All three influence the growth-hormone axis but through different mechanisms: CJC-1295 via the GHRH receptor, and ipamorelin and MK-677 via the ghrelin/secretagogue receptor. The evidence base is uneven: CJC-1295 and ipamorelin rest largely on preclinical and early pharmacology data, whereas MK-677 has more extensive human pharmacology data from its history as an investigational drug candidate. None is FDA-approved and none appears on the July 2026 PCAC docket; all are best described as unscheduled/research-use-only. This is an evidence summary and not a recommendation.
GHK-Cu (topical)
A naturally occurring copper-binding tripeptide (glycyl-L-histidyl-L-lysine) complexed with copper, applied to the skin and widely used as a cosmetic ingredient.
GHK-Cu (injectable)
The same copper-peptide complex prepared for injection and sold for research use, rather than as a topical cosmetic.
How they differ
The molecule is identical in both cases; the meaningful difference is the route of administration and therefore the exposure and evidence context. Topically, GHK-Cu is studied as a skin-active copper peptide reported in the literature to influence dermal remodeling, collagen and glycosaminoglycan synthesis, and antioxidant and wound-related signaling at the site of application. Injectable use would introduce the same peptide systemically, but the pharmacokinetics, distribution, and safety of systemic GHK-Cu dosing in humans have not been characterized in the way the topical cosmetic route has.
What the research says
This is the central distinction between the two. Topical GHK-Cu has a body of human cosmetic and dermatologic data, including studies and formulation research reporting effects on skin appearance, firmness, fine lines, and wound-related endpoints when applied to the skin. Injectable GHK-Cu, by contrast, is largely unstudied in humans: it lacks controlled clinical trials establishing systemic efficacy or safety, and much of what is cited for it is extrapolated from in-vitro work or from the topical literature rather than from studies of injection in people.
Most studied for
Topical GHK-Cu is most studied for cosmetic skin endpoints such as skin firmness, appearance of fine lines and wrinkles, and support of wound healing at the application site. Injectable GHK-Cu is discussed in research-use contexts for systemic tissue-repair and anti-inflammatory hypotheses, but these applications rest on preclinical and mechanistic reasoning rather than human evidence.
Bottom line
GHK-Cu is the same copper-peptide molecule in both forms, so the comparison is really about route and evidence. Topical GHK-Cu has genuine human cosmetic and dermatologic data supporting effects on skin appearance and wound-related endpoints at the application site. Injectable GHK-Cu is largely unstudied in humans and lacks controlled clinical trials on systemic safety or efficacy, meaning its claims are extrapolated rather than directly demonstrated. GHK-Cu is not on the July 2026 PCAC docket and is best described as unscheduled/research-use-only in its injectable form. This is an evidence summary, not medical advice.
Semax
A synthetic peptide derived from a fragment of adrenocorticotropic hormone (ACTH 4-10) with an added stabilizing sequence, studied for cognitive and neuroprotective endpoints.
Selank
A synthetic analog of the immunomodulatory peptide tuftsin, studied for anxiety-related and neuroregulatory endpoints.
How they differ
Both are short synthetic peptides developed in Russia and studied as "nootropic" or neuroregulatory agents, but they derive from different parent molecules and are studied around different endpoints. Semax is based on an ACTH(4-10) fragment and is reported in preclinical work to influence brain-derived neurotrophic factor (BDNF) expression and related neurotrophic and neuroprotective signaling. Selank is a synthetic analog of the immune peptide tuftsin and is studied more for anxiolytic and neuroimmune effects, with preclinical reports involving GABAergic and monoaminergic modulation and expression of BDNF. In brief, Semax is oriented toward cognition and neuroprotection, and Selank toward anxiety and neuroimmune regulation.
What the research says
The evidence for both consists largely of preclinical studies plus a regional clinical literature, much of it published in Russia where the peptides have a history of registered medical use; this literature is generally smaller, older, and less represented in large Western randomized trials. Semax has reported human research in contexts such as cognition, ischemic stroke, and attention; Selank has reported human research in anxiety-related and adaptive contexts. Neither has the large, multi-center randomized-controlled-trial base seen with FDA-approved drugs, and both are best treated as compounds with early and geographically concentrated human data.
Most studied for
Semax is most studied for cognitive performance, attention, and neuroprotection, including stroke-related research in its regional literature. Selank is most studied for anxiety-related endpoints and neuroimmune modulation, and is often framed as a non-sedating anxiolytic candidate in preclinical and early clinical work.
Bottom line
Semax and Selank are both short synthetic neuroactive peptides with overlapping "nootropic" framing but different origins and target endpoints: Semax (from an ACTH fragment) is studied more for cognition and neuroprotection, and Selank (a tuftsin analog) more for anxiety and neuroimmune effects. Their human evidence is early and concentrated in a regional literature rather than large Western randomized trials. A key regulatory distinction as of July 2026 is that Semax appears on the FDA PCAC July 23-24, 2026 docket (a non-binding early-stage vote toward the 503A Bulks List, with 12-18 months minimum to any legal compounding availability even if favorable), while Selank is not on that docket and remains unscheduled/research-use-only. This is an evidence summary and not a recommendation.