Peptides: Product Overview
Peptides are short chains of amino acids, the same building blocks that make up proteins. Many of the body’s own signaling molecules are peptides, including insulin, oxytocin and GLP-1. Since insulin was introduced a century ago, more than 80 peptide drugs have reached the market for conditions including diabetes, cancer, osteoporosis and HIV.
Product profile
| Attribute | Detail |
|---|---|
| What they are | Chains of amino acids joined by peptide bonds |
| Typical size | 2 to about 50 amino acids. Longer chains are usually called proteins. |
| Where they come from | Made by the body, released from food proteins during digestion, or manufactured by fermentation or chemical synthesis |
| Common forms | Prescription injections, oral tablets, topical creams and serums, food supplements such as collagen peptides |
| Usual route for drugs | Injection under the skin. About 90% of peptide drugs are injected because digestion breaks most peptides down. |
| Well-known examples | Insulin, semaglutide, tirzepatide, leuprolide, oxytocin, collagen peptides, GHK-Cu |
Where peptides sit among medicines. Peptides are larger than conventional small-molecule drugs and smaller than biologics such as antibodies. Compared with small molecules, they’re often more potent and more selective for their target. Compared with antibodies, they’re cheaper to produce and can reach some tissues more easily. Their main weaknesses are short survival in the body and poor absorption when swallowed.
Size classes. By common convention, oligopeptides have about 2 to 20 amino acids, polypeptides about 20 to 50, and proteins more than 50. The boundaries aren’t strict, and usage varies between fields.
Chemistry basics
A peptide bond forms when the carboxyl group (-COOH) of one amino acid joins the amino group (-NH₂) of the next, releasing one molecule of water. It’s called a condensation reaction.
amino acid 1 + amino acid 2 → dipeptide (joined by a peptide bond) + H₂O
Each amino acid inside the chain is called a residue. Every chain has two distinct ends: the N-terminus, with a free amino group, and the C-terminus, with a free carboxyl group. Sequences are written from the N-terminus to the C-terminus.
At the body’s normal pH of about 7.4, free amino acids exist mostly as zwitterions. That means they carry both a positive charge (-NH₃⁺) and a negative charge (-COO⁻) at the same time.
A peptide’s activity depends on its sequence and on the shape that sequence folds into. Short peptides are flexible. Longer ones can form helices or sheets, and some are locked into rings by chemical bridges, which can make them more stable.
Biological classes and how they work
Many bioactive peptides sit inactive inside larger proteins until digestion, fermentation or enzyme processing releases them. These hidden fragments are sometimes called cryptides. Sources include milk casein, collagen, soy, legumes and fish.
Metabolic and appetite peptides. GLP-1 and GIP are gut hormones released after meals. Drugs that mimic them, such as semaglutide and tirzepatide, increase glucose-dependent insulin release, slow gastric emptying and act on appetite centers in the brain. This is the most clinically proven peptide class.
Collagen peptides. Hydrolyzed collagen isn’t fully broken down to single amino acids. A randomized crossover study confirmed that small hydroxyproline-containing peptides, mainly Pro-Hyp and Hyp-Gly, reach the bloodstream after ingestion. The proline and hydroxyproline ring structures help them resist digestive enzymes. In lab studies, Pro-Hyp increased the growth of skin fibroblasts, the cells that make collagen.
GHK-Cu (copper tripeptide). GHK (glycyl-histidyl-lysine) is a tripeptide first identified in human plasma in the 1970s. It binds copper tightly, and plasma levels fall with age. In cultured fibroblasts it stimulated collagen synthesis. An analysis of the Broad Institute Connectivity Map suggested that GHK changes the expression of about 31% of human genes, more than 4,000, in cell lines. That figure comes from computer-based gene profiling, much of it by the peptide’s discoverer, and hasn’t been confirmed directly in people.
Antimicrobial peptides. These are part of the body’s innate defenses. They’re usually positively charged and have both water-loving and fat-loving regions. The positive charge draws them to the negatively charged membranes of bacteria, where they open pores and break the cell apart.
Blood pressure peptides. Some peptides released from food proteins inhibit angiotensin-converting enzyme (ACE), the enzyme that makes the blood-vessel-narrowing hormone angiotensin II. That’s the same target as ACE inhibitor drugs, though food peptides are far weaker.
Antioxidant peptides. Certain peptides with hydrophobic and aromatic amino acids have been reported in lab studies to interfere with the Keap1 protein. That frees Nrf2 to switch on the cell’s own antioxidant enzymes.
Common peptides at a glance
The evidence behind popular peptides varies enormously, from trials in thousands of people to a handful of animal studies.
| Peptide | Class | What it’s used or studied for | Human evidence |
|---|---|---|---|
| Semaglutide | GLP-1 receptor agonist | Type 2 diabetes, weight management | Strong: large Phase 3 trials |
| Tirzepatide | Dual GIP and GLP-1 receptor agonist | Type 2 diabetes, weight management, sleep apnea | Strong: large Phase 3 trials |
| Retatrutide | Triple GLP-1, GIP and glucagon receptor agonist | Obesity, type 2 diabetes | Phase 3 trials, still investigational |
| Tesamorelin | Growth hormone-releasing hormone analog | Reducing excess abdominal fat in HIV-associated lipodystrophy | Moderate: randomized controlled trials |
| Sermorelin | Fragment of growth hormone-releasing hormone (amino acids 1 to 29) | Formerly used to diagnose and treat growth hormone deficiency in children | Moderate: older human trials |
| Collagen peptides | Hydrolyzed collagen | Skin, joint and connective tissue support as a supplement | Moderate: human trials, mostly small and often industry-funded |
| GHK-Cu | Copper-binding tripeptide | Topical skin products, wound care research | Limited: small topical studies, mostly lab and gene-profiling data |
| BPC-157 | Synthetic 15-amino-acid fragment of a gastric protein | Tendon, ligament, muscle and gut repair | Very limited: 35 animal studies and 1 small human case series |
| TB-500 | Synthetic fragment of thymosin beta-4 | Soft tissue repair | Very limited: preclinical only |
| CJC-1295, ipamorelin | Growth hormone secretagogues | Raising growth hormone release | Limited: early human pharmacology, no completed efficacy trials |
How peptides are made
| Method | How it works | Typical products |
|---|---|---|
| Enzymatic hydrolysis | Enzymes or fermentation break food proteins into short peptides | Collagen peptides, milk and soy peptides |
| Recombinant production | Engineered microbes or cells produce the peptide | Insulin, first made this way in 1982 |
| Solid-phase peptide synthesis (SPPS) | Amino acids added one at a time on a solid support | Most synthetic peptide drugs and research peptides |
| Native chemical ligation (NCL) | Two unprotected peptide segments joined in water | Long peptides and small proteins beyond SPPS range |
Solid-phase peptide synthesis. Developed by Robert Bruce Merrifield, who won the 1984 Nobel Prize in Chemistry for it. The first amino acid is anchored by its C-terminus to an insoluble resin bead, and the chain is built toward the N-terminus:
- Remove the temporary protecting group, usually Fmoc, from the end of the growing chain.
- Activate the next protected amino acid with a coupling reagent.
- Couple it to the chain, forming a new peptide bond.
- Repeat until the sequence is complete, then cleave the peptide from the resin and remove the side-chain protecting groups.
Each cycle leaves a small fraction of incomplete or misjoined chains, and long sequences tend to clump. Yields fall sharply beyond about 50 residues, so purification by HPLC is essential.
Native chemical ligation. For longer chains, two separately made segments are joined in a neutral water-based buffer. One segment ends in a thioester and the other starts with cysteine. The cysteine’s sulfur first attacks the thioester, often sped up by a catalyst such as MPAA. The link then rearranges itself into a normal peptide bond, leaving no trace at the junction. Repeating this lets chemists build small proteins of a few hundred residues.
Delivery and bioavailability
Most peptide drugs are injected because the digestive tract is built to break peptides down. A swallowed peptide faces two kinds of barrier.
| Barrier | What happens |
|---|---|
| Chemical and enzymatic | Stomach acid unfolds peptides. Pepsin in the stomach, then trypsin, chymotrypsin and elastase in the small intestine, cut them apart. Enzymes on the gut lining finish the job. |
| Physical | A mucus layer traps large molecules. Gut lining cells are sealed by tight junctions, and most peptides are too large and too water-loving to pass through cell membranes. |
What helps a peptide survive. Very short peptides and those rich in proline or hydroxyproline resist digestion better. That’s why collagen dipeptides such as Pro-Hyp reach the blood intact.
Oral permeation enhancers. Two approaches have made some oral peptide drugs possible:
- SNAC (sodium N-[8-(2-hydroxybenzoyl)amino]caprylate) is the enhancer in oral semaglutide tablets. It works locally in the stomach, buffering acid around the tablet and helping the intact peptide cross the stomach lining through the cells themselves.
- Sodium caprate (C10), a medium-chain fatty acid salt, works mainly between cells by briefly loosening the tight junctions.
Making injections last longer. Peptides naturally clear from the body within minutes to hours. Common fixes include attaching a fatty acid chain that binds albumin, as in semaglutide and tirzepatide, which allows once-weekly dosing. Others include swapping in unnatural amino acids, locking the chain into a ring, or attaching polyethylene glycol (PEG).
Evidence and quality
The animal-to-human gap. Promising animal results don’t establish human dose, benefit or long-term safety. BPC-157 is the clearest example. A 2025 systematic review in the HSS Journal found 36 studies: 35 in animals and 1 in humans. The human study was a retrospective review of 12 people with chronic knee pain given a single injection, and 7 reported relief lasting more than six months. The review found a half-life of under 30 minutes and no human safety data.
Quality of unregulated products. Many peptides sold online are labeled “for research use only” and made without pharmaceutical manufacturing controls, inspections or batch testing. A 2026 analysis of more than 6,000 independent test reports examined the purity, actual amount of peptide and bacterial endotoxin in these products. Clinicians have reported vials containing far less peptide than labeled, and toxic impurities such as arsenic at up to 10 times acceptable levels.
The main quality problems found in unregulated peptides:
- Wrong or missing peptide, truncated chains or incorrect sequences left over from synthesis
- Less or more peptide than the label states
- Bacterial endotoxins or leftover chemicals from manufacturing
- No sterility assurance for products meant to be injected
What a full quality check covers. Identity confirmed by mass spectrometry, purity by HPLC, a measured content assay (purity alone doesn’t show how much peptide is in the vial), endotoxin testing and sterility testing, all tied to the specific batch.
This article is for educational purposes only and does not replace medical advice. Speak with your licensed physician about peptide therapies that are available to you in the Philippines and suited to your health history.
