Issue No. 01Foundations4 min readFebruary 28, 2026
What are peptides, really?
A plain-English introduction to the molecules at the center of modern personalized medicine.
What are peptides, really?
A plain-English introduction to the molecules at the center of modern personalized medicine.
pru
THE PRU BRIEF
FOUNDATIONS
ISSUE NO. 01
What are peptides, really?
A plain-English introduction to the molecules at the center of modern personalized medicine.
Dear Pru Community,
Welcome to The Pru Brief — our commitment to you that every issue will be clear, honest, and actually useful. No hype, no jargon left unexplained, no claims we can't back up.
We're starting at the very beginning, because "peptide" is one of those words that gets thrown around constantly and explained almost never. If you've been nodding along while secretly wondering what everyone is actually talking about, this one's for you.
So what is a peptide?
A peptide is a short chain of amino acids — the same building blocks that make up proteins — linked together in a specific sequence. Your body makes thousands of them naturally, and they have one main job: carrying instructions. They're signaling molecules, telling your cells and tissues what to do. Start repairing here. Release this hormone. Dial down that inflammation.
The difference between a peptide and a protein is mostly size. Proteins are large, complex structures folded into three dimensions. Peptides are smaller — typically fewer than 50 amino acids — which makes them easier for the body to absorb and act on quickly. You already know two of them: insulin, which manages blood sugar, and oxytocin, which plays a role in social bonding. Both are peptides your body produces on its own.
A foundational review in Drug Discovery Today by Fosgerau and Hoffmann (2015) described peptides as occupying a unique space in medicine — more targeted than small-molecule drugs, and easier to work with than large biologics, with generally favorable safety profiles. That combination is a big part of why the field has grown so quickly.
A SIMPLIFIED PEPTIDE CHAIN
Why is everyone talking about this now?
Two things happened at roughly the same time. First, the science of synthesizing peptides got dramatically better. A breakthrough by Nobel laureate Robert Bruce Merrifield in the 1960s — solid-phase peptide synthesis — made it possible to manufacture specific peptide sequences reliably and at scale. What used to take years in a lab can now be done far more efficiently, opening the door to a much wider range of therapeutic applications.
Second, the regulatory environment in the U.S. is shifting. The FDA is in the process of restoring access to a range of compounded peptides that were restricted in 2023 — which would allow licensed providers to prescribe them again through proper channels. At Pru, this is exactly the moment we were built for. More on that regulatory story in Issue 02.
What are they actually being used for?
This is where it gets interesting — because "peptide therapy" isn't one thing. Different peptide sequences do completely different things in the body. The categories below give you a sense of the range of active research areas and the compounds most commonly associated with each.
GROWTH & BODY COMPOSITION
Sermorelin · CJC-1295 · Ipamorelin · Tesamorelin
HEALING & RECOVERY
BPC-157 · TB-500 · Thymosin Beta-4
LONGEVITY & SKIN HEALTH
Epithalon · GHK-Cu · Thymalin
WEIGHT & METABOLISM
Semaglutide · Tirzepatide · AOD-9604
SEXUAL HEALTH
PT-141 · Kisspeptin
COGNITIVE FUNCTION
Selank · Semax · Dihexa
SLEEP QUALITY
DSIP · CJC-1295 · Ipamorelin
IMMUNE MODULATION
Thymosin Alpha-1 · LL-37 · Thymalin
These descriptions are for educational purposes only and do not constitute medical advice, diagnosis, or treatment recommendations. Individual suitability for any peptide therapy must be evaluated by a licensed clinician.
What to expect from this newsletter
Every issue will go deep on one thing: a specific peptide and what the research actually says about it, a regulatory update and what it means for you practically, a question we keep hearing from our members, or a behind-the-scenes look at how protocols get designed. The goal is always the same — information that's accurate, well-sourced, and worth your time.
WORTH READING
Fosgerau, K. and Hoffmann, T. (2015). Peptide therapeutics: current status and future directions. Drug Discovery Today, 20(1), pp. 122-128.