What are peptides? History, approved drugs and research peptides

What are peptides?

A peptide is a short chain of amino acids. Picture a string of beads: each bead is an amino acid, and the beads are joined one after another. The order of the amino acids decides what a peptide does, so two peptides of the same length can act completely differently in the body.

The body makes peptides all the time, and many hormones are peptides. According to Fimea, the Finnish medicines agency, peptides are used in legal medicines such as insulins and certain diabetes and weight management medicines [35]. Oxytocin is used as a medicine to induce labour, and vasopressin constricts blood vessels and reduces urine output [16].

So the word "peptide" does not tell you whether a substance is safe, effective or legal. It only tells you what kind of molecule it is. The same word covers a prescription medicine from a pharmacy and a powder ordered online whose contents nobody can vouch for [35].

Read more: Glossary: amino acid, peptide, marketing authorisation | Peptides A-Z

Peptides vs proteins and amino acids: what is the difference?

An amino acid is a single bead. A peptide is a short string of a few to a few dozen amino acids. When the chain is much longer and folds into a complex three-dimensional shape, we call it a protein. The cut-off is a convention and is often put at about 50 amino acids.

Some sizes for comparison: elamipretide has four amino acids, oxytocin nine and tesamorelin 44 [16, 22, 28]. Insulin sits near the border. Frederick Sanger received the 1958 Nobel Prize in Chemistry for his work on the structure of proteins, especially that of insulin [11], and in drug development insulin is treated as the starting point of peptide drugs [1].

Antibodies are much larger proteins. That is why apitegromab and garetosmab, both approved in 2026, are antibodies, not peptides [31, 34]. Likewise, orforglipron acts on the same receptor as the GLP-1 peptides, but it is a small molecule, not a peptide [29].

Read more: Collagen peptides | Peptides in skincare | Collagen and peptides for skin: what the research shows

How do peptides work in the body?

A peptide binds to a receptor on a cell's surface a bit like a key in a lock, and the cell changes what it does. Because peptides are precise keys, they have become an attractive target for drug development [1].

Peptides also have weaknesses. Digestion breaks them down easily, so many peptide medicines are injected rather than taken as tablets, and many peptides are broken down quickly in the body [1]. That is why modified versions have been developed as medicines. For example, octreotide is a modified eight-amino-acid version of the hormone somatostatin, and in rats and monkeys it acted much longer than the natural hormone [20]C. Semaglutide's long action comes from binding to albumin in the blood [16]official.

History 1921-1984: from insulin to peptide synthesis

In 1921 Frederick Banting and the student Charles Best studied a pancreatic extract that lowered blood sugar in dogs, working in J.J.R. Macleod's laboratory at the University of Toronto [5]. Purifying the extract was mainly the work of the biochemist J.B. Collip [5]. In January 1922 at Toronto General Hospital the extract was given to 14-year-old Leonard Thompson, who was close to death from diabetes, and his condition improved [4, 6]. The group published its first patient results in March 1922 [4].

The 1923 Nobel Prize in Physiology or Medicine went to Banting and Macleod "for the discovery of insulin" [7]. Banting gave half of his prize money to Best, and Macleod gave half of his to Collip [5]. Cooperation with the drug company Eli Lilly improved production, and insulin was at first made from animal pancreas [5].

The next big step was making peptides by chemistry. In 1953 Vincent du Vigneaud's group worked out the amino acid sequence of the pituitary hormone oxytocin and published its synthesis the same year [8, 42]. The group was studying vasopressin at the same time [9]. Du Vigneaud received the 1955 Nobel Prize in Chemistry, cited "especially for the first synthesis of a polypeptide hormone" [10]. In 1958 Sanger was honoured for the structure of insulin [11].

In 1963 Bruce Merrifield published a method in which a peptide is built one amino acid at a time on a solid resin [12]. Merrifield received the 1984 Nobel Prize in Chemistry for the method [13]. The 1977 Nobel Prize in Physiology or Medicine went to discoveries about the peptide hormone production of the brain (Guillemin and Schally) and to radioimmunoassays of peptide hormones (Yalow) [14].

In 1982 the FDA approved Humulin, human insulin produced in bacteria by genetic engineering [16]. It was the first commercial health care product made with recombinant DNA technology [15].

History 1985-2022: from GnRH analogues to GLP-1 drugs

The brain's peptide hormones became templates for medicines. Leuprolide is a synthetic nine-amino-acid analogue of gonadotropin-releasing hormone (GnRH), approved by the FDA in 1985 [16]. GnRH analogues are used for example in prostate cancer and endometriosis [16]. The somatostatin analogue octreotide was approved in 1988 for acromegaly and for symptoms of hormone-producing tumours [16, 20].

Nature provided more models. In 1992 a peptide called exendin-4 was described from the venom of the Gila monster (Heloderma suspectum) [18], and its synthetic version exenatide was approved by the FDA on 28 April 2005 for type 2 diabetes [16, 19]. It was the first GLP-1 receptor agonist approved by the FDA [16].

Then came the GLP-1 era. The FDA approved liraglutide for diabetes in 2010 and for weight management in 2014, semaglutide (Ozempic) on 5 December 2017 and for weight management (Wegovy) in 2021, and tirzepatide (Mounjaro) on 13 May 2022 and for weight management (Zepbound) in 2023 [16]. In the EU the corresponding first central authorisations were Victoza in 2009, Ozempic in 2018 and Mounjaro in 2022 [17]. In the STEP 1 trial semaglutide lowered body weight over 68 weeks by 14.9% on average, placebo by 2.4% [25]A.

Tesamorelin is a 44-amino-acid analogue of growth hormone-releasing hormone (GHRH) [22]. The FDA approved it on 10 November 2010 to reduce excess abdominal fat in HIV-infected patients with lipodystrophy [16, 22]official. In a randomised trial in 412 patients with HIV, visceral fat fell by 15.2% over 26 weeks with tesamorelin and rose by 5.0% with placebo [21]A. In the EU the marketing authorisation application was withdrawn in 2012, when the provisional view of the EMA's medicines committee was that it could not have been approved [17, 23]regulator. So tesamorelin is a legal prescription medicine in the United States, but it has no central EU marketing authorisation.

Not every approved peptide stays on the market. Sermorelin (Geref) was approved in the United States in 1990 [16], but it was later discontinued. In 2013 the FDA determined that it was not withdrawn from sale for reasons of safety or effectiveness [24]regulator.

Read more: Weight-loss drugs (GLP-1) guide | Ozempic vs Wegovy vs Mounjaro: what is the difference? | Upcoming weight-loss drugs | Tesamorelin | Sermorelin | Oxytocin

What is changing: the newest approvals 2025-2026

Elamipretide (Forzinity) is a four-amino-acid peptide that the FDA approved on 19 September 2025 under accelerated approval to improve muscle strength in Barth syndrome in patients weighing at least 30 kg [16, 28]official. Accelerated approval means the benefit still has to be confirmed in a further trial [28]. Ten patients entered the open-label extension; among the eight who stayed in for 168 weeks, the six-minute walk distance improved by 96.1 metres on average [27]B.

Orforglipron (Foundayo) was approved in the United States on 1 April 2026 for obesity, and for overweight with a weight-related condition [16, 30]. It is not a peptide but a small molecule taken by mouth that acts on the GLP-1 receptor [29]. In the ATTAIN-1 trial with 3,127 participants, weight fell over 72 weeks by 11.2% on average with the highest dose and by 2.1% with placebo [29]A.

Garetosmab (Pasatru, approved 19 August 2026) and apitegromab (Isembyld, approved 11 September 2026) are antibodies, not peptides [16, 31, 32, 33]. Garetosmab is approved for the rare disease FOP, in which bone forms in connective tissue [34]official. Apitegromab is approved for spinal muscular atrophy (SMA) [31]official, and in a phase 3 trial in 188 patients motor function in those aged 2-12 improved more than with placebo, with the two doses combined [32]A. In the EU the marketing authorisation application for apitegromab was withdrawn on 13 August 2026 [17].

The status of research peptides is also being debated in the United States. In July 2026 the FDA's Pharmacy Compounding Advisory Committee discussed BPC-157, TB-500, KPV and MOTS-c [39]. A committee discussion is not an approval, and none of these substances is in the FDA database of approved drugs [16, 39].

Read more: SS-31 (elamipretide) | MOTS-c | TB-500 | KPV | News

Approved peptide drugs: 36 examples

The table lists 36 peptide drugs from oldest to newest. The FDA column is the year of the oldest approved original application in the Drugs@FDA database [16]. For old medicines this is not necessarily the first year of use: insulin was in use in the 1920s, but the table shows the approval of human insulin made by genetic engineering [5, 16]. The EU column is the first central EU marketing authorisation in the EMA database [17]. A dash means there is no central authorisation; the medicine may still have national authorisations in EU countries. Brand names are examples, and the list is not complete.

Four types of peptide products under one word

The word "peptide" turns up in very different places. It helps to keep them apart, because different rules apply to each:

• Food and supplements. Collagen peptides are sold as food supplements; our collagen peptides page covers them in detail.
• Cosmetics. Skin creams contain peptides, for example copper peptide. They are cosmetics, not medicines. The same substance can still be a cosmetic in a cream but a medicine in Finland as an injectable product: GHK-Cu is on Fimea's medicines list [37], even though copper peptide creams are sold as cosmetics, and according to Fimea a product injected through the skin can be a medicine [35].
• Approved medicines. They have passed clinical trials and received a marketing authorisation, and they are available on prescription [16, 17]. Examples are in the table above.
• Research peptides. Powders are sold online with labels saying "for research use only". According to Fimea, that means the product is not intended for humans [35].

Read more: GHK-Cu (copper peptide) | What blends are

Approved medicines vs research peptides: quality and the grey market

An approved medicine has a marketing authorisation. Before that, a regulator has weighed the benefits and harms from the trial data, and manufacturing quality is supervised. According to Fimea, the efficacy, safety and quality of legal medicines are checked before use [35]. In Finland, selling a medicinal product requires a marketing authorisation or registration [36].

A research peptide has no marketing authorisation. According to Fimea, there is no reliable information on the content, quality or safety of products sold as peptides, an unauthorised product may contain a different substance from the one on the package, and in injectable products impurities such as endotoxins can cause serious harm [35]. The FDA warns of the same: a weight-loss drug bought online may be counterfeit or contain the wrong ingredient or the wrong amount of active ingredient [40].

The same name does not make the same product. Semaglutide from a pharmacy is an authorised medicine, but a vial of semaglutide bought online "for research use" is not [35, 40]. According to the FDA, retatrutide has not been found safe and effective for any condition [40].

In Finland many research peptides are classified as medicines. Annex 1 A of Fimea's medicines list includes for example BPC 157, TB-500, CJC-1295, GHK-Cu and ipamorelin [37]. The WADA Prohibited List names BPC-157 as an example of a substance with no approval by any regulatory health authority for human therapeutic use [41]. In the United States, the FDA's compounding page (updated April 2026) lists BPC-157, TB-500, CJC-1295 and injectable GHK-Cu in the table "nominated but withdrawn" [38], and none of them is in the FDA database of approved drugs [2, 16].

• Approved peptide medicines (in at least one country): semaglutide, tirzepatide, liraglutide, oxytocin, tesamorelin (US), bremelanotide (US), elamipretide (US) [16, 17].
• Research peptides not found in the FDA or EMA databases of approved medicines: BPC-157, TB-500, CJC-1295, ipamorelin and retatrutide [16, 17, 40, 41].

Read more: BPC-157 | Retatrutide | CJC-1295 | Ipamorelin | How to read a COA | Melanotan II | Kisspeptin | Thymosin alpha-1

Legal status in Finland, the EU and other countries

In Finland the key question is whether a product is a medicine. According to Fimea, a product injected through the skin can be a medicine in Finland [35], and selling a medicinal product to the public requires a marketing authorisation or registration [36]. The Medicines Act also has narrow exception routes, such as a special permit from Fimea [36], but we found no public case of a research peptide being obtained in Finland that way.

In the EU, new medicines usually receive their marketing authorisation through the EMA. Tesamorelin and bremelanotide have no central EU authorisation, even though they are prescription medicines in the United States [16, 17, 23].

In the United States approved peptides are legal prescription medicines, for example tesamorelin since 2010 [16, 22]. Research peptides such as BPC-157 and TB-500 are not in the FDA database of approved drugs [2, 16].

Read more: Are peptides legal in Finland? | Are peptides legal in Europe? | Travelling with peptides

Peptides in sport and doping tests

A marketing authorisation does not make a substance allowed in sport. On the WADA 2026 Prohibited List, analogues of growth hormone-releasing hormone such as CJC-1295, sermorelin and tesamorelin, as well as ipamorelin, are in class S2, and insulins in class S4 [41]. Class S0 bans substances with no approval by any regulatory health authority for human therapeutic use and names BPC-157 as an example [41]. The 2026 list does not mention GLP-1 drugs [41].

What the research shows: levels of evidence

Evidence is a staircase. The higher you go, the more a result can be trusted for people. On this site, the letter after a claim tells you what kind of evidence it rests on:

• A Randomised controlled human trial or a meta-analysis of such trials. Some get the substance, some a placebo. Example: the tesamorelin trial in 412 patients with HIV [21]A.
• B Observational human study or a small open study without a comparison group. Example: the open-label elamipretide extension, which 10 patients entered [27]B.
• C Animal study. Many substances that look promising in animals do not work in people.
• D Cell or laboratory study. A starting point, not proof.
• E, not peer-reviewed A company release, conference abstract or registry entry. The result may change once it is published after review.
• official The authorised summary of product characteristics or package leaflet. It tells you what has been approved, but it is not research evidence itself.
• regulator A regulator's assessment or decision. It tells you what has been decided, but it is not research evidence itself.

Research vs marketing: three questions to ask of any claim

For example, BPC-157 has many animal studies but only a few small pilot studies in humans [2, 3]. So the phrase "studies show" tells you little unless you know who the studies were done on. Always ask:

• Humans or animals? A rat result is not a human result.
• How many people, and compared with what? Ten people's experience without a comparison group is different from a placebo-controlled trial with hundreds.
• Who benefits? Is a seller writing, is the author earning a commission, who funded the study?

Read more: BPC-157: user experiences

Side effects and risks

The side effects of an approved medicine are listed in its package leaflet. For example, in the STEP 1 trial the most common side effects of semaglutide were nausea and diarrhoea [25]A. In the tesamorelin trial adverse events did not differ significantly, but more patients stopped because of adverse events in the tesamorelin group [21]A, and according to the label long-term cardiovascular safety has not been established [22]official.

Much less is known about the harms of research peptides. According to Fimea, their possible harms and long-term effects may be unknown, and using them can delay getting proper help [35]. The human studies of BPC-157 are so small that they cannot show rare or long-term harms [2, 3].

Read more: Side effects: what studies report | Bacteriostatic water and reconstitution

Who can get peptide medicines?

A peptide medicine is prescribed for a specific indication, and the doctor judges whether it suits the patient. Indications can be very narrow. Tesamorelin is approved only for excess abdominal fat linked to lipodystrophy in people with HIV, and according to the label not for weight loss [22]official. Elamipretide is approved only for Barth syndrome [28]official, and apitegromab only for SMA patients who already receive an SMN2-targeted treatment [31]official.

Read more: Weight-loss drug cost, reimbursement and prescription routes | Weight-loss drugs without a prescription: risks and the law

Key takeaways

• A peptide is a short chain of amino acids, and many of the body's hormones are peptides.
• The history of peptide drugs began with insulin: the first patient in January 1922 and a Nobel Prize in 1923 [1, 4, 6, 7].
• There are dozens of approved peptide medicines, and GLP-1 drugs are the best known [1, 16].
• Research peptides have no marketing authorisation, and Fimea warns against using injectable peptides bought online [35].