Why Peptides Are Everywhere Now: What the Research Shows

Peptides are everywhere in part because GLP-1 medicines for adults became household names, on top of a peptide drug field that has grown since insulin. That attention describes human medicine. It says very little about whether any one peptide does anything in a dog, cat or horse.

How big is the peptide field?

Large in people, and still growing. A 2021 perspective counted more than 80 peptide drugs on the market since insulin arrived almost a century ago, for conditions that include diabetes, cancer, osteoporosis and chronic pain (Muttenthaler et al., 2021, Nature Reviews Drug Discovery). A 2018 review by authors at an industry research institute put the figure at more than 60 in the United States and other major markets, with more than 150 in active development (Lau and Dunn, 2018, Bioorganic & Medicinal Chemistry). A 2025 review counted more than 40 reaching clinical use in the last decade alone (Jülke and Beck-Sickinger, 2025, Peptides).

The counts differ by review, so read them as a direction rather than a tally. All describe medicines made for people.

Why do drug developers like peptides?

Selectivity is one answer. A review in BioFactors describes peptides as able to reach binding surfaces that small molecules struggle to disrupt, with appropriate affinity and specificity (Anand et al., 2023, BioFactors).

The limits are documented just as clearly. A 2025 review says limited metabolic stability and bioavailability have to be addressed, and lists backbone changes, cyclization and added stabilizing groups as ways to extend half-life (Jülke and Beck-Sickinger, 2025, Peptides). The authors of a dog study note that the body's own GLP-1 is rapidly inactivated by an enzyme (Oda et al., 2013, Research in Veterinary Science).

Delivery is a second limit, and another dog study put numbers on it. In beagles, absolute bioavailability of liraglutide was 0.006% by mouth and 0.03% through the nose, measured against an intravenous reference. The abstract does not give the number of dogs (Sauter et al., 2019, Bioanalysis).

What did the GLP-1 trials actually show?

The best-known peptide drugs are GLP-1 medicines, and one large trial shows what they did in people. STEP 1 enrolled 1,961 adults with obesity or overweight and without diabetes, and randomly assigned them to 68 weeks of semaglutide or placebo, with lifestyle intervention in both groups. Mean body weight fell 14.9% on semaglutide and 2.4% on placebo. Nausea and diarrhea were the most common adverse events, and 4.5% of the semaglutide group stopped because of gastrointestinal events, against 0.8% on placebo. The trial was funded by Novo Nordisk (Wilding et al., 2021, New England Journal of Medicine).

That is a result in adults, not in pets.

What peptide research exists in dogs, cats and horses?

Some, and it is narrow. A 2021 review surveyed antimicrobial peptides in domestic animals, including horses, dogs and cats, and examined their use as potential therapeutics in veterinary medicine (Valdez-Miramontes et al., 2021, Peptides).

Most of the pet studies cited here cover GLP-1 drugs in cats, and they show how results shift. In six healthy cats, glucose tolerance improved by a median of 33% and insulin concentrations rose three weeks after an extended-release exenatide injection (Rudinsky et al., 2015, Domestic Animal Endocrinology). Longer trials in cats with diabetes were less clear. A 16-week pilot trial of 30 cats with newly identified diabetes added exenatide or placebo to insulin and a low-carbohydrate diet. Remission came in 40% of the exenatide cats and 20% of controls, a gap that was not statistically significant (Riederer et al., 2016, Journal of Veterinary Internal Medicine). In a placebo-controlled trial of 22 cats already in remission, exenatide did not change how long remission lasted, 662 days against 669 at the median, though hemoglobin A1c rose on placebo and stayed flat on exenatide (Gilor et al., 2025, Journal of Veterinary Internal Medicine).

In 12 obese but otherwise healthy cats, 12 weeks of exenatide did not change insulin, glucose or glucose tolerance compared with placebo, and weight loss of 5.1% against 3.2% fell short of statistical significance (Hoelmkjaer et al., 2016, PLOS ONE).

Dog work is smaller. Liraglutide lowered the glucose curve by 13.8% in five healthy dogs during an oral glucose test, and by 46.0% in four dogs with type 1 diabetes that were also receiving insulin, compared with insulin alone (Oda et al., 2013, Research in Veterinary Science). That is nine dogs in short experiments.

Horses have a small study too. In a crossover study of six horses, two with normal insulin regulation and four with mild insulin dysregulation, exenatide given before an oral sugar test lowered the insulin response by 20% over four hours and raised estimated insulin sensitivity about threefold (Stefanovski et al., 2022, BMC Veterinary Research).

What the research did not show

The pet studies above share two limits.

They were small. The cat, dog and horse trials above enrolled between 6 and 30 animals and followed them for between two hours and two years.

They tested named products. Exenatide, extended-release exenatide and liraglutide are different products, and a result for one cannot be assumed to transfer to another. None of the pet studies cited here tested semaglutide, the drug in the headline trial.

What popularity does not tell you

A molecule class being important says nothing about whether any one peptide works in a dog, cat or horse. "Peptide" names a structure, a short chain of amino acids, not a function. The more than 40 drugs counted in the 2025 review target different structures, from receptors to pathogens (Jülke and Beck-Sickinger, 2025, Peptides), so a result for one cannot be assumed for another.

Even within one peptide, the answer changes with species, condition and formulation. Exenatide improved glucose tolerance in healthy cats, left insulin unchanged in obese cats and did not lengthen remission in cats already in diabetic remission. That is three different answers about one molecule in one species.

A matching sequence does not settle it either. The authors of the dog study describe liraglutide as sharing 100% amino acid sequence homology with canine GLP-1, and then tested it in nine dogs (Oda et al., 2013, Research in Veterinary Science). A match is a reason to run a study. It is not the result.

Conversation volume is not evidence in your species. The best-known trial enrolled 1,961 adults, and its findings belong to adults.

Where your veterinarian fits in

Bring three things: the exact name of the peptide as written at its source, where you read about it, and a list of everything your animal currently receives, supplements included. Then ask which species the research was done in, whether any study exists in an animal like yours, and what your veterinarian would watch for.

Your veterinarian can also tell you whether a veterinary-labeled option exists for the situation you have in mind, and whether a specialist should weigh in. Your veterinarian knows your animal's history in a way a headline cannot.

Where to go from here

If you want the basics first, start with what peptides are and how pet-related research reads. Two single-peptide reads apply the same species-by-species lens: one on research in dogs and one on research in horses.