The obesity-peptide field has a new naming game. After retatrutide's triple-agonist design reset expectations for how much weight a single molecule can shed, two experimental compounds picked up nicknames one number apart: bioglutide, tagged "GLP-4," and VRX-0075, tagged "GLP-5." The labels are informal shorthand for receptor count, not real drug classes — there is no receptor called GLP-4 or GLP-5. But the numbers point at something real: both compounds take retatrutide's three-receptor backbone and bolt on more.
What makes the pairing interesting is that they bolt on different receptors for different goals — and they sit at very different points on the development path. Bioglutide adds IGF-1 to preserve muscle, is dosed orally, and already has human Phase 1 and Phase 2 data behind it. VRX-0075 adds amylin and calcitonin to push weight loss further, is injectable, and so far exists only as a rat readout. Here is how the two stack up.
Research-context information only. Bioglutide (NA-931) and VRX-0075 are investigational drugs not approved by the FDA. Protocols, doses, and reactions reported below come from published clinical trials, conference abstracts, and self-reported community sources. This article reports what has been documented, not what should be done. Possession or use of investigational drugs outside an authorized clinical trial may be illegal in your jurisdiction. Consult a licensed physician for personal medical decisions.
GLP-4 vs GLP-5 at a Glance
Both compounds start from the same place — retatrutide's GLP-1 + GIP + glucagon core — and diverge from there.
| Bioglutide (NA-931) — "GLP-4" | VRX-0075 — "GLP-5" | |
|---|---|---|
| Agonist class | Quadruple agonist | Quintuple agonist |
| Receptors | IGF-1 + GLP-1 + GIP + glucagon | GLP-1 + GIP + glucagon + amylin + calcitonin |
| Added on top of retatrutide | IGF-1 (muscle preservation) | Amylin + calcitonin (satiety / weight loss) |
| Route | Oral, once-daily small molecule | Injectable, long-acting |
| Design goal | Preserve lean mass while cutting fat | Push weight loss past the triple-agonist ceiling |
| Evidence stage | Human Phase 1 + Phase 2 | Preclinical (rat) only |
| Weight-loss data | 13.8% at 13 weeks (Phase 2, reported) | Greater than retatrutide in obese rats (reported) |
The single most important row is the last two: bioglutide's numbers come from people, VRX-0075's come from rodents. That gap matters more than the one-receptor difference in their names.
The Shared Backbone: Why Both Start With Retatrutide
Retatrutide is the reference molecule this whole conversation is built around. Its triple-agonist design activates GLP-1, GIP, and glucagon receptors at once, and its trials reported weight loss in the mid-to-high 20s percent — among the deepest weight-loss figures reported for any single-molecule obesity agonist in trials to date. That made three receptors the new baseline.
Every leap in this class has come from adding an independent mechanism that doesn't overlap with the ones already there. Semaglutide (one receptor) reached roughly 15% in its trials; tirzepatide (two receptors) reported roughly 22.5%; retatrutide (three) reported the high 20s. Bioglutide and VRX-0075 are two different bets on what the fourth and fifth additions should be. Neither is trying to replace retatrutide's core — they are trying to extend it.
GLP-4: Bioglutide (NA-931) — Adds IGF-1, Oral, Human Data
Bioglutide, developed under the code NA-931, is the quadruple agonist. It keeps retatrutide's GLP-1, GIP, and glucagon targets and adds a fourth: IGF-1. The rationale reported for the IGF-1 arm is muscle preservation — a direct response to one of the main criticisms of aggressive GLP-1-class weight loss, which is that a meaningful share of the weight lost can be lean tissue rather than fat.
Two other features set it apart from most of the class. It is reported as an oral, once-daily small molecule rather than an injectable, and it is the more clinically advanced of the two compounds here. A Phase 1 study described roughly 10 to 13% body-weight reduction over 12 weeks (published in Endocrine Practice), followed by a Phase 2 trial (NCT06564753) that reported 13.8% weight loss at 13 weeks on a 150 mg/day oral dose — findings presented at the American Diabetes Association's 2025 Scientific Sessions as abstract 2189-LB (Diabetes). A separate ADA 2025 presentation, abstract 143-OR (Diabetes), reported that the weight lost came without the muscle loss typically flagged in incretin-class trials — the outcome the IGF-1 arm was designed to produce.
The through-line is that bioglutide is chasing quality of weight loss — fat down, muscle held — through an oral route, and it has human numbers to point to.
GLP-5: VRX-0075 — Adds Amylin + Calcitonin, Injectable, Rat-Only
VRX-0075 is the quintuple agonist. It also keeps retatrutide's GLP-1, GIP, and glucagon core, but the two receptors it adds are different: amylin and calcitonin, the same satiety-and-gastric-emptying axis that cagrilintide and eloralintide target. Where bioglutide's fourth receptor is about preserving muscle, VRX-0075's fourth and fifth are about driving deeper weight loss by stacking an independent satiety mechanism on top of the incretin backbone.
The evidence, though, sits an entire species behind bioglutide. VRX-0075's data comes from a diet-induced obese rat model presented at the American Diabetes Association's 2026 Scientific Sessions as late-breaking abstract 2839-LB, where the compound reportedly produced greater weight loss than retatrutide at matched molar doses. It is described as a long-acting injectable. There is no human dosing, safety, or efficacy data yet — the "beats retatrutide" headline applies strictly to rodents.
For a fuller breakdown of the VRX-0075 rat data, the receptor design, and where the quintuple-agonist class sits in the pipeline, see our dedicated deep dive: Quintuple Agonist Beats Retatrutide in Rats: VRX-0075.
More Receptors vs Further Along: The Real Trade-Off
The instinct is to assume the compound with more receptors is the more advanced one. Here the opposite is true. VRX-0075 targets five receptors to bioglutide's four, yet bioglutide is the one with human Phase 1 and Phase 2 readouts, while VRX-0075 remains a preclinical animal result. Receptor count is a design choice; clinical stage is what determines how much the numbers can be trusted.
That reframes the comparison. Bioglutide and VRX-0075 are not really competing for the same outcome. Bioglutide's reported Phase 2 figure of 13.8% at 13 weeks is a human number aimed at muscle-sparing fat loss via an oral route. VRX-0075's "greater than retatrutide" is a rat number aimed at maximum weight loss via injection. One is further down the evidence path; the other is aiming at a higher ceiling it has not yet tested in people. Animal weight-loss models routinely overstate what later shows up in human trials, and tolerability — especially for an amylin-containing molecule — is the make-or-break question no rat study answers.
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What You Can Actually Buy Today
Neither compound is in our vetted vendor lineup yet. Bioglutide and VRX-0075 are both investigational and both unapproved, and neither has an established presence in the research-peptide catalogs we track. Early gray-market listings for both are beginning to surface as they get attention; until a source we've vetted for identity and COA carries them, treat any current listing as unverified.
What is accessible is the shared backbone both compounds are built on. Retatrutide covers three of the four-or-five targets — GLP-1, GIP, and glucagon — and is the closest available analog to either molecule's core. It is widely stocked by research vendors while its Phase 3 program continues. For readers tracking the GLP-4 and GLP-5 story, retatrutide is the real-world reference point the whole class is measured against.