# Research Peptide Fundamentals research peptides — Peptide Scienes > Peptide Scienes investigates Research Peptide Fundamentals research peptides across four unrelated pharmacological families — CJC-1295, GHK-Cu, semaglutide, and tesamorelin — tracing every claim back to its citation. An independent digest, not a vendor or clinic. An investigative reading file on CJC-1295, GHK-Cu, semaglutide, and tesamorelin — four research peptides from at least three unrelated pharmacological families, read against the studies that actually exist. ## The short version Peptide Scienes is a working file on four research peptides that get lumped together under one loose label — "research peptides" — even though they come from entirely different corners of biology. A *peptide* is simply a short chain of amino acids, the building blocks of proteins; a *receptor* is the docking site on a cell that a peptide has to fit into before it can do anything. Two of the four peptides here, CJC-1295 and tesamorelin, both target the same receptor — the one that tells the pituitary gland to release growth hormone — but arrived at very different regulatory fates. GHK-Cu is a naturally occurring copper-binding tripeptide best documented in skincare, not in a syringe. Semaglutide is the odd one out: an FDA-approved prescription medicine with a research base an order of magnitude larger than the other three combined. This file traces where the evidence for each one actually comes from, in plain language, with the underlying studies cited by number. It does not recommend a dose for anyone, and it does not sell anything. ## The science of research peptides, explained Why do CJC-1295, GHK-Cu, semaglutide, and tesamorelin all end up filed under the same heading? That is the actual reporting question behind this site. "Research peptide" is a marketing category more than a scientific one — it describes how something is sold, not what it does. Follow the actual mechanism of each compound and the four pull apart into three unrelated stories: two growth-hormone-releasing hormone (GHRH) analogs that persuade the pituitary gland to release more of its own growth hormone, a copper-binding tripeptide that occurs naturally in blood plasma and skin, and an incretin mimetic that has become one of the most studied classes of medicine in the world. Following each story to its actual citations is where this file spends its time. CJC-1295 and tesamorelin bind the same growth-hormone-releasing hormone receptor, and yet one is a discontinued research chemical with a documented cautionary history and the other is an FDA-approved drug for a single narrow indication [1][18][19]. GHK-Cu has one of the deepest cell-biology literatures of any peptide on this desk and one of the thinnest human-trial literatures for any use beyond topical skincare [6][7]. Semaglutide sits at the other extreme: a compound with multi-thousand-participant randomized trials behind almost every claim made about it, and a 2025 head-to-head trial against tirzepatide that quietly changed how confidently those claims can now be stated [13][15][16]. The gaps are not hidden here — they are the story. ## What are research peptides? In the loosest sense, a "research peptide" is any peptide sold for laboratory study rather than as an approved medicine — a category defined by its supply chain, not its chemistry. Peptides are strings of amino acids linked in a specific sequence; some occur naturally in the body (GHK-Cu is one, released when a certain kind of collagen breaks down), and some are synthetic analogs engineered to resist the enzymes that would normally break a natural hormone down within minutes (CJC-1295 and tesamorelin are both built this way, off the same growth-hormone-releasing hormone template). The regulatory story varies enormously within the category. Semaglutide, despite starting life in exactly this kind of laboratory pharmacology, is now an approved prescription medicine on the strength of clinical trials involving tens of thousands of people [15]. Tesamorelin cleared an FDA approval for one specific condition [19]. CJC-1295 and GHK-Cu, by contrast, remain outside any approved human-use pathway for the systemic uses discussed on this site — which is why the phrase "research chemical, not for human consumption" recurs across their pages. ## Where the science is solid, and where it thins out Reading these four compounds side by side surfaces an uncomfortable but useful pattern: the peptides with the biggest online reputations are not always the ones with the biggest evidence base. Semaglutide's file is built on randomized trials with thousands of participants and years of follow-up [14][15][16]. Tesamorelin's is built on a real but narrow set of trials in one patient population, repeatedly confirmed by a 2026 meta-analysis [18]. CJC-1295's human evidence is decades old, small, and limited to short-term pharmacokinetics in a few dozen healthy adults [3][4][5]. GHK-Cu's evidence is almost inverted — enormous depth in cell and gene-expression studies, and comparatively little in controlled human trials outside topical cosmetics [7][9]. None of that means the thinner files are wrong. It means the confidence this site attaches to each claim is calibrated to the evidence actually cited, not to how popular a compound is in comment sections. Read each compound's own page for the specific studies behind that calibration. --- An investigative reading file on research peptides — every claim traced to its source, every gap named, revised whenever the record moves.