Peptides Guide | What to Know in 2024
Peptides have played an important role in medicine starting with the advent of insulin therapy in the 1920s. Since then, more than 60+ different peptides have been approved for used in the United States. Clearly peptides have been around in the research community for some time, but 2023 marks a major shift in which discussion of peptides has penetrated the mainstream. More than ever before, the public is aware of the benefits and potential of peptides in everything from reducing cancer risk to weight loss and sexual well-being. With increased public interest, increases in research funding are sure to come. As of 2018, there were more than 150 peptides in active development that had entered human clinical trials. That number has only increased since. This peptides guide looks at trends in peptides research and lists a few of the most popular peptide classes that you should know about in 2023.
What Are Peptides?
Peptides are basically shorter versions of proteins, which is to say chains of amino acids connected into a specific sequence. They are a naturally occurring product that, thanks to the miracles of modern science, can be synthesized in laboratories and on an industrial scale. Peptides, it turns out, are critical to a lot of signaling cascades within the body. They regulate energy balance, feeding behavior, sleep, fatigue, sexual arousal, brain function, and even how quickly we heal. Peptides have been shown to play important roles in the body’s response to exercise and injury. They even determine how quickly we age.
Trends in Peptide Research
As the ability to synthesize synthetic peptides has grown over the decades since the 1920s, something interesting has happened. Science has slowly but surely moved away from simply trying to mimic the structure of natural peptides, a practice which necessarily limited development to shorter peptides, and has instead focused on developing novel peptides that act on receptors of interest even if they bear no resemblance to native peptides.
Trend in peptide length by decade:
Source: Science Direct
On average, the development time for a peptide is about 9.4 years and there are often setbacks along the way. Sometimes, peptides that are rejected as unsuitable for use get a second chance when they are altered, combined with other peptides, or applied in a new setting. As the catalog of therapeutic peptides has grown, so too has the research grown with it. For instance, the rate of discovery of peptide-addressable targets for which no peptide has yet been discovered or developed has helped to spur a frenzy of research activity. For instance, development of a melanocortin 4 receptor (MC4R) agonist could be critical in the fight against obesity and is of intense research focus. Scientists have identified the receptor, now they are searching for a peptide that is specific for it. Additionally, peptide drug delivery techniques are constantly being advanced, making it possible for peptides that were once unstable, difficult to store, or complicated to administer to become more attractive as potential therapeutics.
The peptide categories discussed below are among the most hotly researched in the world. They contain peptides that have long been used in the clinical setting as well as peptides that are under active research. This is hardly an exhaustive list though. It is just a teaser to introduce the world of peptides research.
Peptides for Brain and Cognitive Health
Peptides that are active in the central nervous system can be broken down into two classes, those that treat dysfunction and those that enhance normal function. While it is true that most peptides span the gap between treatment and enhancement, it is useful to think of them in these terms.
Semax and Selank were both developed in Russia and were some of the earliest nootropics (cognitive enhancers) developed. Research shows that Selank works at the GABA receptor to reduce anxiety and alters the expression of nearly 36 different genes involved in learning. Thus, Selank is both a treatment of anxiety and a potential cognitive enhancer. Semax is valued for its ability to boost brain-derived neurotrophic factor (BDNF), which makes it a cognitive enhancer and allows it to protect the brain of stroke and other insult.
Other nootropic peptides include BPC 157, Cerebrolysin, Pinealon, Epitalon, and P21 to name a few. What is interesting about these peptides is that they enhance and protect cognitive health in different ways. This has helped to advance our understanding of how the brain works and has provided new fodder for probing the mechanisms of human cognition.
Peptides for Healing
The ability of certain peptides to regulate blood vessel growth, alter fibroblast responses, and stimulate extracellular matrix deposition makes them useful in accelerating healing and in improving the quality of wound repair.
BPC 157 has become a much-discussed peptide on podcasts and in other lay circles because it helps the body heal in a variety of ways. Derived from naturally occurring body protection compound, BPC 157 accelerates wound healing, promotes blood vessel growth, and even improves the immune response to injury. It is of interest in tendon and connective tissue healing as well as in the treatment of disorders of the GI tract (e.g. Crohn’s disease, ulcerative colitis). Other peptides with widely researched healing properties include TB-500 (43aa Thymosin Beta 4) and MGF.
GHK-Cu is a natural peptide that has wound healing and anti-inflammatory effects. It has been shown to suppress free-radical damage and is a potent stimulator of fibroblast activity. It is of particular interest for its ability to promote skin health and is known to counteract some of the side effects of chemotherapy.
Peptides for Longevity
One of the interesting things that peptides have helped to reveal is that aging is a biological process controlled, at least to some degree, by signaling cascades that can be altered. Peptides are important in these processes and their utilization in rodent models has resulted in remarkable benefits that slow or even reverse aging.
Sermorelin is probably the most famous anti-aging peptide and has been, more than once, referred to as the fountain of youth. Sermorelin is a natural growth hormone releasing hormone agonist and could easily be put into the muscle growth category, but its benefits are far more important than simply improving muscle mass. Research shows that sermorelin reduces scarring in the heart, improves renal function, fights the effects of dementia, and improves sleep. Sermorelin has been touted as a potential treatment for somatopause, the decline in growth hormone that occurs as we age and is linked to a lot of the dysfunction that plagues older individuals.
Peptides for Growth
Peptides for muscle growth often work by stimulating the growth hormone axis and thus increasing growth hormone production. This leads to increased muscle and bone growth along with increased fat burning. Of course, there are other ways to stimulate muscle growth, such as preventing muscle degradation and thus shifting the overall balance toward growth.
CJC 1295 is a synthetic derivative of growth hormone releasing hormone. This large peptide has been shown to increase GH release by as much as 10-fold. GHRP-2 and GHRP-6 also promote GH increases but they do so by acting at the ghrelin receptor rather than the growth hormone releasing hormone receptor. These peptides protect and enhance muscle structure, stimulate appetite, improve immune function, and alter sleep cycles. Ipamorelin, which is like GHRP-2 and GHRP-6, is highly selective. It is valued for all the above reasons, but also because it is especially beneficial for bone health.
Follistatin is a synthetic version of human follistatin and it works by neutralizing the enzyme myostatin. Myostatin is known to break down muscle protein and research has shown that animals lacking myostatin have twice as much muscle mass as others. Research shows that just eight weeks of follistatin treatment can increase muscle mass by 10%.
Peptides for Sexual Health
Drugs like Viagra and Cialis are known for their role in improving sexual function. They work by increasing blood flow to the genitals, but they are not effective for everyone. Research has shown that sexual arousal is a centrally controlled function of the melanocortin system. Peptides like melanotan 1, melanotan 2, and PT-141 operate on the melanocortin system. They increase sexual arousal in both men and women, but have also been shown to alter food cravings, help fight alcohol addiction, and regulate skin pigmentation. Peptides in this group have been developed to treat erectile dysfunction, female hypoactive sexual desire disorder, and certain skin conditions that make it difficult for people to be in the sun.
Peptides for Weight Loss
Weight loss and, in particular, targeted fat burning, have become major targets of peptide research in recent years. It has become clear to scientists that a great deal of energy balance is regulated by peptides and that a small shift in the levels of certain peptides can have a profound impact on whether the body stores or burns fat. Some peptides under development work with existing energy balance pathways to promote fat burning while others apply more novel approaches.
Adipotide targets the blood supply of adipocytes (fat cells) but not the blood supply of any other part of the body. By preventing blood from reaching fat cells, adipotide can help to reduce weight by as much as 25% in just three months. Because adipocytes are known to produce hormones that encourage further eating, the use of adipotide also reduces appetite and makes it easier to keep weight off.
AOD9604 is also a targeted fat burning peptide, but it works by stimulating specific arms of the growth hormone axis rather than by targeting blood supply to adipocytes. Research in rats shows that daily used can reduce body weight by as much as 50% in one month.
Tesamorelin, which is similar to sermorelin, has been approved for use in the treatment of HIV-associated lipodystrophy. The peptide can reduce adiposity by nearly 20% and can improve triglyceride levels. It is held up as a beacon of what effective peptide research and development can bring to market.
Peptides Research Summary
Above is a review of what peptides classes are of current interest in research settings. There is a great more that could be discussed in the realm of peptide research, but there isn’t room enough to do it. The literature on peptides and their potential benefits is vast. The above review was meant to hit the highlights and to outline some of the areas into which active research is paying dividends. The future of peptide therapeutics looks very bright with new tools and techniques being constantly developed for increasing the pace of discovery.
 J. L. Lau and M. K. Dunn, “Therapeutic peptides: Historical perspectives, current development trends, and future directions,” Bioorg. Med. Chem., vol. 26, no. 10, pp. 2700–2707, Jun. 2018, doi: 10.1016/j.bmc.2017.06.052.