METABOLIC & WEIGHT RESEARCH / MATRIX
Four Peptides, Four Different Evidence Profiles
How a growth-hormone fragment, a triple incretin agonist, a GLP-1 benchmark, and a GHRH analogue differ in mechanism, trial results, and how much is actually proven.
The short version
This page lines up AOD-9604, retatrutide, semaglutide, and tesamorelin on the dimensions that matter most for reading their research honestly: mechanism class, most-studied application, evidence maturity, regulatory status, and the single biggest caution for each. The short version: three of the four have real, replicated human efficacy data behind them, retatrutide, semaglutide, and tesamorelin, and one does not, AOD-9604, despite a clean rodent mechanism. Only two are broadly FDA-approved, semaglutide and tesamorelin, one is investigational with strong Phase 2 numbers, retatrutide, and one was never approved for its intended use, AOD-9604. None of this is medical advice, and no dose is recommended anywhere on this desk.
The comparison matrix
| Dimension | AOD-9604 | Retatrutide | Semaglutide | Tesamorelin |
|---|---|---|---|---|
| Mechanism class | hGH C-terminal fragment; no GH-receptor binding; beta-3 adrenergic / lipogenesis pathway | GIP/GLP-1/glucagon triple receptor agonist | GLP-1 receptor agonist (single incretin arm) | GHRH receptor agonist (amplifies endogenous GH/IGF-1) |
| Most-studied application | General obesity (failed primary endpoint); preclinical osteoarthritis | Obesity, type 2 diabetes, metabolic liver disease | Type 2 diabetes, obesity, cardiovascular and kidney outcomes | HIV-associated lipodystrophy (visceral fat) |
| Evidence base | ~900-subject human safety program; efficacy not demonstrated; discontinued [3] | Phase 2 only, two pivotal trials plus a substudy; Phase 3 ongoing [8][9][10] | Large multi-indication Phase 3 RCTs; FDA-approved [14][15][16] | FDA-approved for one indication; 5-RCT meta-analysis [18] |
| Regulatory status | Never approved anywhere; program discontinued | Investigational; not approved anywhere as of mid-2026 | FDA-approved (multiple indications) | FDA-approved (HIV lipodystrophy only) |
| Key caution | Human weight-loss efficacy not demonstrated; gray-market quality unverified | Investigational status; dose-dependent heart-rate increase [9] | GI intolerance; substantial weight regain after stopping | Benefit does not persist after stopping [22]; narrow approved indication |
Mechanism class
The four compounds barely overlap mechanistically, which is itself informative. AOD-9604 and tesamorelin both trace back to the growth-hormone axis but work in opposite directions: AOD-9604 is a piece of growth hormone engineered to skip the growth-hormone receptor entirely, while tesamorelin activates the GHRH receptor to make the pituitary release more intact growth hormone. Semaglutide and retatrutide sit in the incretin family: semaglutide engages one receptor, GLP-1R, while retatrutide engages three, GLP-1R, GIPR, and GCGR, with measurably different potency at each, roughly 8.9x native GIP at the GIP receptor but only 0.3-0.4x at the other two [7]. Only semaglutide and retatrutide share a receptor target with each other, GLP-1R; the other pairings do not overlap at all.
Most-studied application
Semaglutide has the widest footprint by indication: type 2 diabetes, chronic weight management, cardiovascular-event reduction, kidney-disease-event reduction, and metabolic liver disease [14][15][16]. Retatrutide's trial program is narrower but growing: obesity, type 2 diabetes, and a metabolic-liver-disease substudy, all still Phase 2 [8][9][10]. Tesamorelin's approved use is the narrowest of the four, HIV-associated lipodystrophy specifically, though its evidence within that lane is dense [18][20][22]. AOD-9604's human program targeted general obesity and did not succeed [3]; a separate, much smaller preclinical line has explored joint cartilage [1].
Evidence maturity
This is where the four genuinely separate. Semaglutide has the deepest evidence: multi-thousand-participant randomized trials across several indications and years of post-marketing surveillance [14][15][16][17]. Retatrutide has two pivotal Phase 2 trials, 338 and 281 participants, plus a 98-person substudy, a real and fairly large evidence base, but one stage short of the confirmatory trials that would support approval [8][9][10]. Tesamorelin's evidence is smaller in absolute participant count but concentrated and consistent within its one approved indication, reinforced by a 2026 five-trial meta-analysis [18]. AOD-9604's evidence is the most lopsided: a large, roughly 900-subject, safety program that succeeded, paired with an efficacy result that did not [3], the textbook shape of a compound whose mechanism was real but whose clinical benefit wasn't.
Regulatory status
Semaglutide and tesamorelin are both FDA-approved prescription medicines, but at very different scope: semaglutide across type 2 diabetes, weight management, cardiovascular-risk reduction, and metabolic liver disease; tesamorelin for one narrow indication, HIV-associated lipodystrophy, with every other use off-label. Retatrutide is not approved anywhere as of mid-2026; it remains in Phase 3 trials, and material sold as research-grade retatrutide outside those trials carries no verified identity or purity, prompting FDA enforcement action against vendors in 2025 [6]. AOD-9604 was never approved for any indication; its anti-obesity development program was discontinued after its pivotal efficacy trial failed to reach statistical significance.
Key caution
Each compound carries a defining caveat. For AOD-9604, it is that a clean rodent mechanism did not survive human efficacy testing, and any current use is experimental with unverified gray-market material. For retatrutide, it is the combination of investigational status with a documented, dose-dependent heart-rate increase whose long-term cardiovascular meaning is still being studied in an ongoing dedicated trial [9]. For semaglutide, it is that gastrointestinal intolerance drives most discontinuations and that stopping treatment is followed by substantial weight regain, framing this as chronic rather than curative therapy. For tesamorelin, it is that its benefit is contingent on continued dosing, visceral fat measurably reaccumulates once treatment stops [22], and that its approval covers one specific population, not general fat loss. Read together, the pattern across all four is the same: mechanism, trial size, and regulatory status move together, and a compound sitting at the strong end of all three, semaglutide, looks nothing like one sitting at the weak end, AOD-9604.