What Are Peptides Used For? An Evidence-Based Primer

The word "peptide" gets thrown around in clinics, gyms, and biotech press releases as if it described a single thing. It does not. Peptides are a sprawling class of short amino-acid chains, and the answer to what are peptides used for now spans diabetes, obesity, oncology, infectious disease, and a fast-growing research literature on tissue repair. This primer separates the approved, the in-trial, and the speculative.

Key takeaways#

• Peptides have been in clinical use since 1922, when insulin became the first peptide therapeutic. Roughly 100 peptide drugs are now approved globally.

• There are currently more than 400 peptide drugs under global clinical development with over 60 already approved for clinical use in the United States, Europe and Japan.

• The largest approved categories are metabolic (insulin, GLP-1 agonists), oncology (somatostatin analogues, peptide receptor radionuclide therapy), and antimicrobial (polymyxins, bacitracin).

• Semaglutide, a GLP-1 peptide, produced roughly 14.9% mean body-weight reduction at 68 weeks in the STEP 1 trial.

• Tesamorelin is the only FDA-approved peptide for HIV-associated lipodystrophy; it is weight-neutral and not indicated for general weight loss.

• Recovery-focused peptides like BPC-157 show strong preclinical signal but lack robust human trials.

Peptides are a century-old drug class, not a recent trend#

The framing of peptides as a "new" wellness category obscures their long pharmaceutical history. Peptides have been used in therapy for a century now, since the moment when a team of Canadian researchers discovered the therapeutic potential of insulin for the treatment of type 1 diabetes. Since then, the class has expanded dramatically. Therapeutic applications of peptides represent a research field of growing interest, as testified by the 26 peptides approved as drugs between 2016 and 2022 by the Food and Drug Administration, with more than 200 peptides in clinical development, and with another 600 peptides undergoing preclinical studies.

This matters because it sets the right expectation. Peptides are not a fringe modality. They are a mature drug class with well-characterised manufacturing, regulatory pathways, and side-effect profiles for the molecules that have cleared trials. What is newer is the gap between approved peptides and the much larger pool of research-grade peptides that have generated promising preclinical data without yet completing the clinical work.

Metabolic disease is the largest approved use case#

If you ask what are peptides used for in volume terms, the answer is metabolic disease. Insulin alone is dispensed to tens of millions of people. The newer story is the GLP-1 receptor agonist class. In 2019, marketing approval was granted for oral semaglutide, the world's first glucagon-like peptide-1 receptor agonist (GLP-1RA) approved for the treatment of type 2 diabetes.

The weight-management data turned the category into a household name. In the STEP 1 trial published in NEJM, researchers enrolled 1961 adults with a body-mass index of 30 or greater (or ≥27 with at least one weight-related coexisting condition), who did not have diabetes, and randomly assigned them, in a 2:1 ratio, to 68 weeks of treatment with once-weekly subcutaneous semaglutide (at a dose of 2.4 mg) or placebo, plus lifestyle intervention. The coprimary end points were the percentage change in body weight and weight reduction of at least 5%. The cardiovascular follow-up confirmed the metabolic benefit translated to hard outcomes. Semaglutide, a long-acting analogue of GLP-1, administered at a dose of 2.4 mg subcutaneously once weekly for 104 weeks, was found to reduce body weight by a mean of 15.2% among patients with overweight or obesity who did not have diabetes.

Research suggests the metabolic peptide story is still expanding. The SELECT cardiovascular trial extended the indication into secondary prevention, and ongoing work in type 1 diabetes and osteoarthritis is mapping further use cases. The mechanism is straightforward: GLP-1 analogues mimic the endogenous incretin hormone, slowing gastric emptying and reducing appetite via central pathways.

Oncology and antimicrobial peptides are the older, quieter workhorses#

Outside metabolic medicine, peptides have been doing unglamorous work for decades. The discovery and use of antibiotics containing non-protein polypeptide chains have been a significant advancement in the fight against bacterial infections. These polypeptide antibiotics, which include actinomycins, bacitracin, colistin A, colistin B, polymyxin B1, and polymyxin B2, have shown effectiveness against both Gram-negative and Gram-positive bacteria.

In oncology, peptides serve two distinct roles. Peptides have been widely explored and applied in cancer therapy. On the one hand, peptides can directly kill tumour cells; on the other hand, as tumour-targeting peptides or peptide vaccines, they can enhance the therapeutic effect. Somatostatin analogues like octreotide and lanreotide treat neuroendocrine tumours by binding receptors expressed on the cancer cells themselves. Research has shown that radiolabelled peptide analogues can carry targeted radiation directly to receptor-positive tumours, a platform now formalised as peptide receptor radionuclide therapy.

The administration reality of these approved peptides is worth noting. Therapeutic peptides administered as injectables remain the most commonly used dosage forms, particularly in the form of subcutaneous, intravenous, or intramuscular injections. Oral bioavailability remains the field's hardest unsolved problem, which is why most peptides on the market still require injection.

Hormone-axis peptides target specific endocrine signals#

A third category of approved peptides modulates hormonal signalling. Tesamorelin is the cleanest example. According to the FDA prescribing information, EGRIFTA WR (tesamorelin for injection) is approved in the U.S. for the reduction of excess abdominal fat in HIV-infected adult patients with lipodystrophy. It is a growth hormone-releasing factor (GHRF) analog that acts on pituitary cells in the brain to stimulate the production and release of endogenous growth hormone.

The hedged framing here is important. Long-term cardiovascular safety of tesamorelin has not been established. Consider risk/benefit of continuation of treatment in patients who have not had a reduction in visceral adipose tissue. It is not indicated for weight loss management as it has a weight-neutral effect. Despite frequent off-label marketing in wellness circles, the approved indication is narrow, and the regulatory record is explicit about what the molecule has and has not been shown to do.

Other hormone-axis peptides include GnRH analogues (leuprolide, triptorelin) used in prostate cancer and endometriosis, and growth-hormone-releasing peptides like ipamorelin and CJC-1295 that are not approved medicines. CJC-1295 combined with ipamorelin showed significantly improved maximum tetanic tension in murine models with glucocorticoid-induced muscle loss, but these findings are limited to animal studies.

Recovery and tissue-repair peptides are not yet approved for these uses#

The fastest-growing search interest sits in a category that has no FDA approvals: peptides studied for tissue repair, tendon healing, and gut integrity. BPC-157 is the most-discussed example, and the evidence base illustrates the pattern across this whole subcategory.

Preclinical data points to broad activity. Experimentally it was demonstrated to enhance the healing of different wounds, such as gastric ulcer, skin, cornea, muscle, colon-colon anastomosis, colocutaneous fistula, and segmental bone defect. It was also found to accelerate the healing of transected rat Achilles tendon and medial collateral ligament of knee. Preliminary evidence from a 2025 systematic review summarises the state of play: the review looked at 36 studies published from 1993 to 2024. The findings showed that BPC-157 helps promote healing by boosting growth factors and reducing inflammation. It has improved outcomes in muscle, tendon, ligament, and bone injury models in animals. In one human study, 7 out of 12 people with chronic knee pain felt relief for over six months after receiving one BPC-157 knee injection. Animal studies showed no harmful effects, but there is no clinical safety data in humans.

That last line is the whole story. A recent orthopaedic primer was blunt: while peptide therapy may possess significant therapeutic and regenerative potential, it is critical that orthopaedic and sports medicine providers understand the current lack of evidence to support the clinical use of these peptides. Despite the popularity of these peptides in mainstream media and among patients, significant research regarding the safety and efficacy of these therapeutic methods is required before definitive recommendations can be made. The same review noted that GHK-Cu showed promise in wound healing and anti-inflammatory effects, but no clinical data support its use for musculoskeletal conditions.

The honest summary: research-grade recovery peptides are associated with biologically plausible mechanisms and consistent animal data, but they have not crossed the threshold of human trial evidence that would let a clinician recommend them as therapy. They are research tools, used by individuals at their own risk, with availability through specialised research-chemical suppliers rather than pharmacies.

What unites the approved peptides: targeted mechanisms, not blunt action#

Across diabetes, oncology, infection, and endocrinology, the reason peptides have been viable as drugs comes down to the same property. In recent years, peptides smaller size and balance of conformational rigidity and flexibility have made them promising candidates for targeting challenging binding interfaces with satisfactory binding affinity and specificity. Studies have shown that this binding selectivity translates to lower off-target effects than many small molecules, which is part of why the development pipeline keeps expanding.

The trade-off is that peptides are fragile. They get degraded by proteases, they cross membranes poorly, and most cannot be taken orally without engineering tricks. That is why GLP-1 oral formulations were a bigger pharmaceutical event than they looked from the outside, and why most peptides in clinical use are still injected.

The right framing closes the gap between hype and reality#

The honest answer to what are peptides used for is layered. A small set treats serious disease with regulatory backing and decades of evidence. A larger set is in active clinical development with strong but unfinished data. A third set is preclinical, intriguing, and frequently misrepresented by people selling things. Knowing which category a given peptide sits in is the entire skill, and it pairs naturally with the overview of what peptide therapy means in practice. Klarovel exists to make that distinction practical: protocol templates that respect the evidence and dose-tracking that respects your data. Klarovel does not sell, source, or fulfil peptides; the clinical layer is the entire product. Start with how it works, check your numbers in the peptide calculator, and register when you want the protocol layer wired up.