# Research Peptide Fundamentals research peptides — peptidespodcast > Research Peptide Fundamentals research peptides: a guided tour of the research-peptide landscape covering BPC-157, CJC-1295, Retatrutide, GHK-Cu, Thymosin Alpha-1, and NAD+. Peer-reviewed citations, plain-English summaries, no products. A guided tour of the research-peptide landscape — what six of the most-studied compounds are, how they work, and what the published evidence actually shows. Citations, not prescriptions. ## The short version This desk is a reading guide, not a store. It gathers what the published scientific literature actually says about six compounds that come up repeatedly in research-peptide conversations: [BPC-157](/bpc-157), [CJC-1295](/cjc-1295), [Retatrutide](/retatrutide), [GHK-Cu](/ghk-cu), [Thymosin Alpha-1](/thymosin-alpha-1), and [NAD+](/nad). A *peptide* is a short chain of amino acids — the same building blocks as proteins, but far smaller. The compounds on this desk range from three amino acids (GHK-Cu) to 39 (Retatrutide). NAD+ is technically a coenzyme, not a peptide at all, but it belongs here because the research questions around it overlap closely with the others. The six cover five major areas of investigation: tissue repair and cytoprotection (BPC-157), the growth-hormone axis (CJC-1295), metabolic and weight research (Retatrutide), skin and matrix biology (GHK-Cu), immune modulation (Thymosin Alpha-1), and cellular energy metabolism and longevity (NAD+). None is an approved drug for the indications most often discussed in research communities, and several are explicitly not approved anywhere. This guide tells you what was studied, in which species, and how far the evidence reaches — and no more. ## What are research peptides? A *research peptide* is a synthetic compound built from amino-acid sequences — sometimes found in nature, sometimes engineered — that has been studied in laboratory and animal models but has not completed the regulatory pathway to become an approved drug for most uses. Manufacturers and suppliers describe them as for laboratory research use only. That framing matters. It means dosing in humans, long-term safety profiles, and real-world effectiveness outside controlled trials are usually unestablished. When this desk reports a number, it reports it the way the study did: for example, *a mean body-weight change of -24.2% at 48 weeks in 338 adults with obesity* [16] — not as a recommendation for anything outside that specific trial population. Where a study was done in rats, mice, or cell cultures rather than people, we say so clearly. Research peptides exist on a regulatory spectrum. Some, like Retatrutide, are active investigational drugs in large Phase 3 trials. Others, like BPC-157, have almost no human data at all. A few, like Thymosin Alpha-1 (thymalfasin), are approved as drugs in dozens of countries but not in the United States. GHK-Cu is a legal cosmetic ingredient when applied topically, but injectable use is unapproved. NAD+ is sold as a dietary supplement. Understanding where each compound sits on that spectrum is part of reading the literature accurately. ## How these six compounds fit the landscape The six compounds on this desk were chosen because they represent distinct areas of the research-peptide space and are among the most-searched and most-discussed in the literature. - [**BPC-157**](/bpc-157) is the featured lead — a stable gastric pentadecapeptide with the deepest animal-model record among all research peptides, and angiogenesis (new blood-vessel growth) as its best-characterized mechanism [4]. As of 2025 reviews, only three small human pilot studies exist [2]. - [**CJC-1295**](/cjc-1295) is a long-acting analog of growth-hormone-releasing hormone. A 2006 human pharmacology trial showed it raised GH 2- to 10-fold and IGF-1 1.5- to 3-fold for up to 11 days from a single dose [11]. It was never approved; its original DAC program was discontinued. - [**Retatrutide**](/retatrutide) is an investigational triple-receptor agonist targeting GIP, GLP-1, and glucagon receptors simultaneously. Phase 2 data in 338 adults showed a mean -24.2% body-weight reduction at 48 weeks [16] — the most striking clinical signal on this desk — but it is still in Phase 3 trials as of 2026. - [**GHK-Cu**](/ghk-cu) is a copper tripeptide that stimulates dermal fibroblasts to synthesize collagen, elastin and glycosaminoglycans, and it has a long topical cosmetic safety record [21]. A 6-month hair-loss RCT showed statistically significant hair-count increases versus placebo [20], making it the compound here with the broadest controlled human evidence. - [**Thymosin Alpha-1**](/thymosin-alpha-1) (thymalfasin) is a 28-amino-acid thymic peptide that modulates dendritic cells, T-cell maturation, and innate-adaptive immune balance. It is approved as a drug in over 35 countries [24], but the 2025 Phase 3 TESTS trial in sepsis found no significant mortality benefit [23] — a cautionary example of rigorous late-phase evidence tempering earlier optimism. - [**NAD+**](/nad) is included as the outlier: a coenzyme, not a peptide, but one of the most-studied compounds in longevity biology. Its tissue levels decline with age, and precursor supplementation with NMN or NR raises blood NAD+ reliably in human trials [29][32], though whether that translates to meaningful clinical outcomes remains an open question [28]. Use the compound pages to go deeper, or [compare these peptides](/compare) side by side across class, mechanism, evidence maturity, and regulatory status. ## How this desk reads the literature peptidespodcast is a cross-referenced literature digest. Each compound page cites peer-reviewed studies, species-by-species, and the citations link to a shared [references list](/references) aggregating every source across all six compounds. Where the evidence is preclinical, from a single lab, or preliminary, we say so in the same sentence — that context is as important as the finding itself. We do not sell anything. We do not give medical advice. We do not list doses. The aim is a precise, quiet map of what the published science shows, so anyone can see where the evidence is solid and where it remains mostly animal data or early-phase signals. Claims that go further than the cited evidence should be read with skepticism — including claims on this site, which you should always trace back to the primary source. --- An independent literature digest — summarizing published research on research peptides, nothing more, nothing less.