The GLP-1 drug class is expanding faster than anyone is explaining it clearly. New mechanisms, new approvals, pipeline drugs that will matter in two years, patient communities figuring out practical questions that clinical trials don't ask — and almost no single place that organizes all of it in a way that's actually useful to the person deciding whether to start Wegovy or switch to Mounjaro.
GLP Dex is an attempt to build that layer. Not a news site. Not a pharmaceutical database. A structured, opinionated reference organized around how the drugs actually work and what people actually need to know.
What we're building
Four distinct arms, each with a different job.
GLP Dex — the drug reference
The menu. Eighteen drug profiles organized by receptor family — single agonists, dual agonists, triple, oral, emerging. Each profile follows the same structure so they're comparable: at a glance, mechanism, trial data, dosing, development status, safety. Rarely updated once a drug is stable, because the science doesn't change. The place to go when you want to know what a specific drug actually is and how it compares to the alternative your doctor mentioned.
GLP Science — the education layer
The biology behind the taxonomy. How GLP-1R, GIPR, and GCGR work, what happens when you combine them, why the class evolved from single to dual to triple agonism, what the oral shift means mechanically. Written for people who want to understand the science rather than just read the trial numbers. Stable reference content — the receptors haven't changed.
GLP-1 Guide — curated practical knowledge
The content that doesn't come from the clinical trial but matters just as much. What to eat. How to protect muscle. What the side effects actually mean and how long they last. Distilled from clinician content, patient community data, and the research that connects the two. For people on a GLP-1 drug or seriously considering one — the questions that don't get answered in a 10-minute appointment.
The Vision — editorial
This series. Where the thinking about what GLP Dex is and should be gets written down. The agent design, the knowledge architecture, the product decisions and why we made them. Less a public roadmap than an honest record of how this is being built and what we think it's for.
Why now
The GLP-1 class is at an inflection point. A drug that was mostly used for diabetes five years ago is now central to conversations about obesity, cardiovascular disease, MASH, addiction, and potentially neurodegeneration. The pipeline is deep — several drugs in late-stage trials that will matter significantly in the next two to four years. And patients are navigating this landscape with scattered information: Reddit threads, manufacturer websites, TikTok explainers that range from excellent to dangerous.
The gap between what's known and what's accessible isn't a content problem. It's a structure problem. The information exists. It's not organized in a way that helps people make decisions.
Summary(The short version)
GLP Dex is a structured drug intelligence layer for the GLP-1 class — a drug reference that doesn't change often, a science layer that explains the biology, a practical guide distilled from clinical and community knowledge, and an editorial layer where the product thinking lives. Each piece has a distinct job. The agent is the interface that connects them.
This post is the foundation for the GLP Dex series. Before reading any individual drug profile, it helps to understand the three receptors that define the entire landscape, what happens when you activate them, and why the combination of targets determines a drug's mechanism and clinical character.
The incretin system
"Incretin" is a portmanteau of "intestinal secretion of insulin" — it refers to hormones released by the gut after eating that amplify the pancreas's insulin response before blood glucose even peaks. The discovery that gut hormones could enhance insulin secretion by 50–70% (the "incretin effect") was foundational to the entire field.
The two primary incretins are:
- GLP-1 (glucagon-like peptide-1) — secreted by L-cells in the distal small intestine and colon within minutes of eating. Stimulates insulin secretion, suppresses glucagon, slows gastric emptying, and acts on the brain to reduce appetite.
- GIP (glucose-dependent insulinotropic polypeptide) — secreted by K-cells in the proximal small intestine. Also stimulates insulin, but its role in weight loss was thought to be neutral or opposing for decades — this turned out to be more complicated than expected.
Both hormones are cleared within minutes by the enzyme DPP-4 (dipeptidyl peptidase-4), which is why native GLP-1 can't be used as a drug directly — it's gone too fast.
Definition(Incretin effect)
The observation that the same rise in blood glucose causes a much larger insulin response when glucose is delivered orally (triggering gut hormone release) versus intravenously. The difference — typically 50–70% of total insulin secretion — is attributable to GLP-1 and GIP. People with type 2 diabetes show a diminished incretin effect, which is why restoring it pharmacologically is effective.
The three receptors
Every GLP-1 drug is defined by which of these three receptors it targets and how strongly.
GLP-1R (GLP-1 receptor)
The primary target of every drug in this class. GLP-1R is a G protein-coupled receptor (GPCR) expressed in the pancreas, brain, gut, heart, kidneys, and lungs. Activation drives:
- Insulin secretion — glucose-dependent: only triggers insulin release when blood glucose is elevated, which is why GLP-1 drugs have low hypoglycemia risk on their own
- Glucagon suppression — reduces glucagon from pancreatic alpha cells, which otherwise drives glucose production in the liver
- Gastric emptying delay — slows how fast food leaves the stomach, blunting post-meal glucose spikes
- Satiety signaling — acts on the hypothalamus and brainstem to reduce appetite and food intake; this is the primary mechanism of weight loss
GIPR (GIP receptor)
The second target added in dual and triple agonists. GIPR is expressed in the pancreas, fat tissue, bone, and brain. The conventional view was that GIP was redundant with GLP-1 for insulin secretion and had no useful weight-loss effect — even that GIP receptor activation might oppose weight loss.
Tirzepatide's Phase 3 data upended this. GLP-1/GIP dual agonism consistently outperforms GLP-1 alone on weight loss (20–22% vs 15% for semaglutide). The current understanding is that GIPR activation in fat tissue and the brain synergizes with GLP-1R signaling in ways that are still being worked out mechanistically.
Intuition(Why GIP's role surprised everyone)
Early GIP agonist experiments in rodents showed weight gain, not loss — which convinced researchers for years that GIP was the "unhelpful" incretin. What changed: tirzepatide's real-world efficacy data forced a reexamination. Current evidence suggests that at high receptor engagement levels, GIPR in the brain and adipose tissue actually enhances the GLP-1 satiety signal. The rodent findings may have reflected species differences or dose-dependent effects. The lesson: receptor biology in isolation doesn't always predict what happens when two signals are combined.
GCGR (glucagon receptor)
The most potent lever for metabolic rate and liver fat. Glucagon is canonically a counter-regulatory hormone — it raises blood sugar by driving hepatic glucose production. This is why it's used to treat hypoglycemia.
But glucagon receptor activation also:
- Increases energy expenditure — raises resting metabolic rate, an effect GLP-1 agonism alone doesn't have
- Drives hepatic fat oxidation — mobilizes fat from the liver, which is why glucagon co-agonism is particularly interesting for MASH (metabolic dysfunction-associated steatohepatitis)
- Reduces food intake — through central nervous system effects
Adding GCGR to GLP-1R agonism (dual) or GLP-1R + GIPR (triple) theoretically addresses the metabolic rate component that limits weight loss with GLP-1 alone: the body's adaptive response to caloric restriction reduces energy expenditure, partly counteracting weight loss. Glucagon receptor activation pushes back against that adaptation.
Why receptor combinations define the landscape
The entire GLP-1 drug taxonomy flows from these three receptors:
| Class | Targets | Example drugs |
|---|---|---|
| Single GLP-1 agonist | GLP-1R | Semaglutide, liraglutide, exenatide |
| Dual GLP-1/GIP | GLP-1R + GIPR | Tirzepatide, VK2735, olatorepatide |
| Dual GLP-1/glucagon | GLP-1R + GCGR | Survodutide, pemvidutide, mazdutide |
| Triple agonist | GLP-1R + GIPR + GCGR | Retatrutide |
| Amylin combos | GLP-1R + AMYR | CagriSema (semaglutide + cagrilintide) |
Adding receptors generally increases efficacy — trial data follows a rough pattern where triple > GLP-1/GIP dual > GLP-1/glucagon dual > single GLP-1 for percent weight loss. But more targets also means more complexity in tolerability, and the glucagon component in particular requires careful titration because of its glucose-raising effect.
Molecular scaffolds: peptide vs non-peptide
A second axis that cuts across the receptor taxonomy: how the drug is built.
Peptide-based drugs are synthetic analogs of GLP-1 or related peptides — modified to resist DPP-4 degradation and extend half-life from minutes to days or weeks. They require injection because peptides are broken down in the gut before reaching circulation. Most approved and pipeline drugs are peptide-based.
Non-peptide small molecules are orally bioavailable because they're small enough to survive gut transit and don't have the structural features that DPP-4 targets. Orforglipron and aleniglipron are the leading examples. They trade some potency for convenience — and potentially for cost, since peptide manufacturing is expensive and a current bottleneck for Ozempic/Wegovy supply.
Definition(GLP-1 receptor agonist (GLP-1RA))
Any drug that activates the GLP-1 receptor to produce GLP-1-like effects. Used as a class label that encompasses single, dual, and triple agonists as long as GLP-1R is one of the targets. Sometimes used interchangeably with "incretin mimetic" though that term technically includes DPP-4 inhibitors (which work by blocking GLP-1 breakdown rather than mimicking it directly).
How to read the drug profiles
Each drug profile in this series follows the same structure so they're comparable at a glance:
- At a glance — targets, company, approval status, modality
- How it works — mechanism specific to this drug's receptor profile
- Trial data — key phase, efficacy numbers, trial names
- Dosing and administration — frequency, route, titration
- Development status — filing status and timeline
- Compared to alternatives — how it sits relative to 1-2 closest comparators
- Safety profile — what's been reported in trials
The series is organized by receptor family rather than alphabetically or by approval date, because mechanism is the most useful axis for understanding why each drug exists and what it's trying to do differently.
Summary(The short version)
GLP-1 drugs work by binding receptors that normally respond to gut hormones released after eating. The GLP-1 receptor drives insulin secretion, appetite suppression, and gastric slowing. Adding GIP receptor engagement (dual agonism) amplifies weight loss beyond what GLP-1 alone achieves. Adding glucagon receptor engagement raises metabolic rate and targets liver fat. Triple agonism hits all three. The drugs are either peptide-based (injectable) or small-molecule non-peptide (oral). Every drug in this series is a variation on which of these levers it pulls and how hard.