# Research Peptide Fundamentals research peptides — Peptide Research Alliance > An independent literature digest of the most-studied research peptides — BPC-157, Retatrutide, Ipamorelin, GHK-Cu, and NAD+ — summarized from peer-reviewed research across tissue repair, the growth-hormone axis, metabolic science, longevity biology, and cellular energy. An independent literature desk covering the five most-discussed research compounds across categories: what each one is, how it is described to work, and what the peer-reviewed evidence actually shows. ## The short version This desk covers five compounds that come up repeatedly in discussions of research peptides and cellular health: BPC-157, Retatrutide, Ipamorelin, GHK-Cu, and NAD+. They are not a single category — they work through entirely different mechanisms, have different regulatory statuses, and have very different amounts of human evidence behind them. What they share is that they are among the most actively discussed compounds in research communities, and that the published literature on each of them is often misread. A *peptide* is a short chain of amino acids — the same building blocks that make up proteins, only far smaller. Some peptides act on specific receptors; some modulate enzymes; some carry minerals to cells. NAD+ is not a peptide at all — it is a coenzyme found in every living cell. Each compound on this desk gets its own page: what it is, how it is described to work, what the evidence actually says, and where the honest uncertainties are. We cite studies by number and link all of them on the [references](/references) page. We sell nothing, prescribe nothing, and list no human doses. ## The five research areas this desk covers The five compounds on this desk represent five distinct research categories: - [**BPC-157**](/bpc-157) — *Tissue repair and cytoprotection.* A synthetic 15-amino-acid peptide derived from a sequence in human gastric juice protein. In animal models it is studied primarily for angiogenesis-driven tissue healing [4][6]. Its human evidence base is extremely thin — as of 2025 only three small pilot studies exist [2] — and it is not an approved drug anywhere. - [**Retatrutide**](/retatrutide) — *Metabolic and weight-loss pharmacology.* An investigational triple-agonist compound targeting the GIP, GLP-1, and glucagon receptors simultaneously [8][11]. Phase 2 trials in humans documented up to ~24% body-weight loss at 48 weeks [11] and an 82% liver-fat reduction at 24 weeks in those with liver steatosis [10]. It is not yet approved anywhere and remains in Phase 3 trials. - [**Ipamorelin**](/ipamorelin) — *Growth hormone axis.* A selective synthetic pentapeptide agonist of the ghrelin / growth hormone secretagogue receptor (GHS-R1a), notable for selectively triggering GH release without the cortisol or prolactin elevation seen with related peptides [16]. Its one Phase 2 human trial, in postoperative ileus, did not meet its primary endpoint [15]. - [**GHK-Cu**](/ghk-cu) — *Skin biology and matrix remodeling.* A copper-chelated tripeptide (Gly-His-Lys) found endogenously in human plasma and collagen, studied in topical skin trials for collagen stimulation, wrinkle reduction, and hair follicle support [18][21]. It is the compound on this desk with the most direct human evidence — though that evidence is concentrated in small topical studies. - [**NAD+**](/nad) — *Cellular energy and longevity biology.* A dinucleotide coenzyme central to cellular energy production and the activity of DNA-repair and gene-regulation enzymes. Tissue NAD+ declines with aging; oral precursors NMN and NR demonstrably raise blood NAD+ in humans [24][27], though whether this translates to meaningful clinical outcomes remains under investigation [23]. [Compare these peptides](/compare) side by side across class, evidence maturity, and regulatory status. ## What the phrase 'research peptide' actually means The label *research peptide* is a legal and regulatory designation, not a quality marker. It means the compound has been synthesized and studied in laboratory or clinical-trial settings but has not been approved by any regulator — the FDA, EMA, or equivalent — as a medicine for human use. Under this designation, compounds are sold legally for laboratory research only. This matters practically because it means: no verified human dosing protocols; no clinical quality-assurance requirements on products sold outside trials; no long-term human safety data in many cases; and, for some compounds, prohibition in organized sport under the World Anti-Doping Agency code. The term is not uniform across all five compounds on this desk. Retatrutide is an *investigational drug* with an active FDA IND and a Phase 3 trial program. GHK-Cu is simultaneously a legal cosmetic ingredient (when applied topically) and a research peptide when used by other routes. NAD+ is a *dietary supplement* in most markets, not a peptide, and not a research chemical in the conventional sense. BPC-157 and Ipamorelin are research chemicals with no approved therapeutic indication and no successful late-phase human trial. Each page on this desk specifies the relevant regulatory status for that compound. ## How this desk reads the literature Peptide Research Alliance is a cross-referenced literature digest. Each compound page summarizes the peer-reviewed studies relevant to that compound, cites them by numbered superscript, and links to a shared [references](/references) list covering all five compounds. Where evidence is predominantly animal, we say so. Where a human trial is the only data point and it failed its primary endpoint, we say so. Where a compound's research record comes substantially from a single investigator or group, we note it. Where marketed claims exceed what the published evidence supports, we say so plainly — because that gap is part of the accurate picture, not a footnote to it. We do not recommend, prescribe, or sell. The aim of this desk is a precise, well-cited map of what is known, so that the distance between current evidence and current marketing is visible. --- An independent literature digest of peer-reviewed research — definitional, cited, and free of products, prescriptions, and dosing recommendations.