Retatrutide vs Semaglutide: Mechanisms, Trial Data & Differences

Semaglutide is a single-target GLP-1 receptor agonist, FDA-approved as Ozempic, Wegovy, and Rybelsus, with multiple completed Phase 3 trials behind it. Retatrutide is an investigational GLP-1/GIP/glucagon triple agonist still in Phase 3, which produced up to ~24% body-weight loss at 48 weeks in Phase 2. One is an approved drug; the other is a research compound.

TL;DR: Both are once-weekly injectable peptides for metabolic disease, but they sit at opposite ends of the evidence spectrum. Semaglutide hits one receptor (GLP-1), works mainly by suppressing appetite and slowing gastric emptying, and is backed by large Phase 3 RCTs showing ~15% weight loss (STEP program) plus a 20% reduction in cardiovascular events (SELECT). Retatrutide hits three receptors (GLP-1 + GIP + glucagon); the added glucagon arm drives direct fat oxidation and raises energy expenditure, which is why Phase 2 produced the highest weight loss (~24% at 48 weeks) of any obesity drug at that stage — but it has no completed Phase 3, no FDA approval, and no long-term safety data. If you want established efficacy and safety, semaglutide is the studied choice; retatrutide is a higher-ceiling bet that is still being proven. A vault-unique wrinkle: retatrutide’s incretin arms are glucose-dependent, so very-low-carb diets can blunt its mechanism more than semaglutide’s.

Research-use and educational content only. This article is not medical advice. Semaglutide is FDA-approved as the prescription drugs Ozempic, Wegovy, and Rybelsus — but gray-market or “research-only” semaglutide vials sold without a prescription are not approved products and are not quality-controlled to pharmaceutical standards. Retatrutide is not approved anywhere and is sold only as a research chemical. Nothing here is a recommendation to obtain or self-administer either compound outside a regulated medical setting. VialBase may earn a commission from vendor links on this page; see the disclosure under “Legal & Sourcing Reality.”

At a Glance

PubMed counts and trial figures are sourced from the VialBase research library (as of April 2026). Where a single non-peer-reviewed source is the basis for a number, it is flagged below.

What Is Semaglutide?

Semaglutide is a 31-amino-acid glucagon-like peptide-1 (GLP-1) receptor agonist developed by Novo Nordisk. It is a modified analog of human GLP-1(7–36) with roughly 94% sequence homology, engineered with an Aib substitution at position 2 (to resist DPP-4 breakdown) and a C-18 fatty-diacid chain attached via a linker at Lys26. That fatty-acid chain binds non-covalently to serum albumin, creating a depot effect that stretches the half-life to about 7 days — the basis for once-weekly dosing.

It is the most widely prescribed incretin therapy in the world and one of the most heavily studied peptides in clinical medicine, with over 4,500 PubMed publications as of April 2026. It is sold under three brand names: Ozempic (subcutaneous, type 2 diabetes), Wegovy (subcutaneous, chronic weight management), and Rybelsus (oral tablet, type 2 diabetes). Because it is an approved pharmaceutical, the regulatory and quality picture for the branded products is fundamentally different from research peptides — though, as covered below, gray-market “research” semaglutide vials are a separate and unapproved category.

What Is Retatrutide?

Retatrutide (development code LY3437943) is a 39-amino-acid triple hormone-receptor agonist from Eli Lilly that simultaneously activates the GIP, GLP-1, and glucagon receptors. It represents the current frontier of incretin pharmacology — the progression from single agonism (semaglutide) to dual agonism (Tirzepatide) to triple agonism. Like semaglutide, it is acylated with a fatty-acid chain for albumin binding, giving it a half-life of roughly 6 days and supporting once-weekly subcutaneous dosing.

The Phase 2 obesity data, published in the New England Journal of Medicine, showed up to 24.2% body-weight reduction at 48 weeks — the largest weight loss reported for any anti-obesity drug at that stage of development. As of April 2026 it has ~133 PubMed publications, and it is in the Phase 3 TRIUMPH program. It is not FDA-approved, has never been approved in any jurisdiction, and is available only through gray-market research-peptide channels. The defining feature is the third receptor: glucagon agonism adds a direct fat-burning, energy-expenditure component that GLP-1-only and GIP/GLP-1 dual agonists do not have.

Mechanism Differences

This is the core of the comparison. Both drugs share a GLP-1 backbone, but retatrutide adds two more receptor targets, and each addition changes the metabolic math.

Shared mechanism: GLP-1 agonism

Both compounds activate the GLP-1 receptor, a G-protein-coupled receptor expressed in the pancreas, brain, gut, heart, and kidneys. The GLP-1 arm:

• Suppresses appetite via hypothalamic signaling (arcuate and paraventricular nuclei), reducing hunger and the “food noise” users frequently describe.
• Enhances glucose-dependent insulin secretion — it stimulates insulin only when blood glucose is elevated, which is why hypoglycemia risk is low.
• Suppresses glucagon (in semaglutide’s case) in a glucose-dependent manner, lowering hepatic glucose output.
• Delays gastric emptying, prolonging satiety and blunting post-meal glucose spikes.

For semaglutide, this is essentially the whole story — it is primarily a centrally-acting appetite suppressant with favorable glucose handling, and its weight-loss effect is dominated by reduced intake.

What GIP adds (retatrutide, shared with tirzepatide)

The GIP receptor arm further potentiates glucose-dependent insulin secretion, improves insulin sensitivity in adipose tissue (possibly promoting favorable fat redistribution), and may attenuate GLP-1-mediated nausea — a possible reason multi-agonists can be better tolerated at high efficacy than GLP-1 mono-agonists.

What glucagon adds (unique to retatrutide)

This is the differentiator. Counter-intuitively, agonizing the glucagon receptor (rather than suppressing it, as semaglutide does indirectly) is therapeutic in this combination because the GLP-1/GIP arms keep blood glucose in check while glucagon does metabolic work:

• Hepatic fat oxidation: Glucagon stimulates fatty-acid oxidation and ketogenesis in the liver — it directly burns liver fat. This is why retatrutide is especially promising for MASH/MASLD (see trial data).
• Increased energy expenditure (thermogenesis): Glucagon raises resting energy expenditure, so the body burns more calories at rest. This adds a spend-more lever on top of the eat-less lever, attacking obesity from both sides. Semaglutide has no equivalent.
• Lipolysis: Mobilizes stored fat from adipose tissue.
• Amino-acid catabolism (the trade-off): Glucagon also promotes gluconeogenesis from amino acids, raising a theoretical concern about accelerated muscle-protein breakdown — i.e., more lean-mass loss. This is why higher protein intake and resistance training are emphasized even more heavily with retatrutide than with semaglutide.

The one-line summary: semaglutide makes you eat less; retatrutide makes you eat less and burn more. That dual mechanism is the leading explanation for retatrutide’s higher Phase 2 weight-loss ceiling — and for its distinct side-effect concerns.

Head-to-Head Trial Data

There is no published head-to-head RCT directly comparing retatrutide and semaglutide in the VialBase research library. The comparison below is cross-trial — different populations, durations, and endpoints — so the numbers are directional, not a clean apples-to-apples contest. Critically, the two compounds are at very different evidence maturities, which matters more than any single percentage.

Semaglutide — the STEP / SELECT programs (mature, Phase 3 + real-world)

Semaglutide’s evidence is the gold standard for the class: large, double-blind, placebo-controlled RCTs with cardiovascular outcome data — not just weight on a scale, but fewer heart attacks and strokes. STEP 4 also delivered the most important real-world lesson: stopping the drug reverses most of the benefit, which reframes both compounds as ongoing therapies rather than cures.

Retatrutide — Phase 2 + early Phase 3 (investigational)

Evidence-grading note (important). Retatrutide’s Phase 2 obesity [PMID 37366315], T2D [PMID 37385280], and MASLD [PMID 38858523] data are peer-reviewed NEJM- and Lancet-tier RCTs and should be treated as solid for what they measured — but they are Phase 2: smaller, shorter (36–48 weeks), and not designed to detect rare harms or cardiovascular outcomes. The Phase 3 TRIUMPH registrational program is real and several obesity arms have completed enrollment (its design is published [PMID 41090431]), but no peer-reviewed Phase 3 efficacy results exist yet. The headline ~29% figure comes from a single non-peer-reviewed source (a video analysis citing an unpublished topline readout), not from a journal article or a verifiable company release, and should be treated as unverified until Eli Lilly publishes the TRIUMPH results. Two distinguishing positives from the peer-reviewed Phase 2 set are worth noting: retatrutide had not reached a weight-loss plateau at 48 weeks (suggesting a higher ceiling), and its liver-fat reduction (>80%) exceeds what GLP-1 or GIP/GLP-1 agonists achieve — both consistent with the glucagon mechanism.

Bottom line on the head-to-head: On raw weight-loss percentage, retatrutide’s Phase 2 ceiling (~24%) beats semaglutide’s Phase 3 ceiling (~15%). But semaglutide has years of Phase 3 data, hard cardiovascular-outcome evidence, regulatory approval, and a known long-term safety profile. Retatrutide has a higher number and a thinner, earlier, partly-unverified evidence base. Higher ceiling, lower certainty.

Side Effect Profiles Compared

Both compounds share the GLP-1 class’s gastrointestinal signature; retatrutide layers glucagon-specific concerns on top. Direct comparison is again cross-trial, so incidence figures are not strictly equivalent.

Gastrointestinal (both)

GI effects are the dominant, expected, mostly-transient adverse events for both — worst during dose escalation, easing over time.

Interestingly, retatrutide’s nausea numbers read lower than semaglutide’s in these (non-matched) trials — possibly reflecting the GIP arm’s proposed anti-nausea effect, though cross-trial comparison can’t confirm this.

Lean-mass loss (both — slightly worse risk profile for retatrutide)

Both drugs cause loss of lean mass alongside fat. Semaglutide trials show ~39% of weight lost was lean mass; retatrutide Phase 2 body-composition data suggests ~40%, with an added mechanistic concern: the glucagon arm promotes amino-acid catabolism, so the theoretical risk of muscle loss is higher. Both warrant resistance training and adequate protein (semaglutide: ~1.2–1.6 g/kg/day; retatrutide protocols often push 1.5–2.0 g/kg/day).

Semaglutide-specific signals

• Pancreatitis (0.1–0.3%): discontinue if suspected.
• Gallbladder disease (cholelithiasis): increased with rapid weight loss.
• Thyroid C-cell tumors: boxed warning based on rodent studies (medullary thyroid carcinoma); contraindicated with personal/family history of MTC or MEN2.
• Acute kidney injury: reported, usually secondary to dehydration from GI effects.
• Diabetic retinopathy complications: reported in patients with pre-existing retinopathy (the VialBase library notes this; rapid glucose-lowering is the suspected driver).
• NAION (non-arteritic anterior ischemic optic neuropathy): a retrospective cohort study from Mass Eye and Ear (Hathaway et al., JAMA Ophthalmology 2024) found that patients prescribed semaglutide had a higher risk of NAION than matched patients on non-GLP-1 medications — with a markedly elevated hazard ratio in the diabetic and overweight/obese subgroups [PMID 38958939]. This is an association from observational data, not established causation, and the absolute risk is small (NAION is itself rare); subsequent pharmacovigilance and larger database studies have been mixed. It remains an active safety signal under regulatory review rather than a confirmed adverse effect.

Retatrutide-specific signals

• Heart-rate increase: mild, dose-dependent (+2–4 bpm), consistent with glucagon-mediated thermogenesis.
• Hepatic glucose output: glucagon drives gluconeogenesis, which could theoretically worsen hyperglycemia in poorly controlled T2D — but the GLP-1/GIP arms appear to counterbalance this in trials.
• Bone mineral density: rapid weight loss of this magnitude may affect bone; long-term data pending.
• The big one — unknowns: retatrutide has only 48-week Phase 2 safety data. There is no long-term safety profile, no cardiovascular-outcome data, and no rare-event surveillance comparable to semaglutide’s. This is the single most important asymmetry in the entire comparison.

Both share expected class contraindications: personal/family history of MTC, MEN2, pregnancy/breastfeeding. Retatrutide adds caution in severe hepatic impairment (glucagon-receptor activation).

The Carbohydrate Angle

This is a mechanism-driven distinction most competitor write-ups miss, and it favors a more nuanced read of “which is stronger.”

Retatrutide’s GLP-1 and GIP effects are glucose-dependent by design — incretin hormones evolved to fire when carbohydrates are consumed, triggering enhanced insulin secretion only when glucose is present. The practical consequence: very-low-carb, ketogenic, and carnivore diets can directly blunt retatrutide’s core insulin-sensitizing mechanism.

• On a ketogenic diet (<50 g carbs/day), pancreatic beta cells are primed to secrete insulin efficiently, but there is no glucose signal to trigger the enhanced incretin response (per Dr. Trevor Bachmeyer).
• Chronic low-carb dieting can induce physiological insulin resistance — muscles preferentially burn fat and resist glucose uptake — which works directly against retatrutide’s insulin-sensitizing intent.
• Eating carbohydrates also triggers endogenous GLP-1 and GIP release from intestinal L- and K-cells, creating a synergistic effect with the exogenous peptide.

How strong is this? Honestly: it is mechanistic reasoning plus practitioner observation, not a head-to-head clinical trial. The glucose-dependence of GLP-1/GIP insulinotropic action is well established pharmacology — incretins potentiate insulin secretion only when glucose is elevated. But the specific, frequently-circulated figure that incretin therapies show “~40% greater efficacy with moderate carb intake (120–150 g/day) versus low-carb (<50 g/day)” traces to a practitioner discussion (the Dr. Trevor Bachmeyer “Retatrutide Masterclass”), not to an identifiable peer-reviewed study; we were unable to verify a primary publication supporting that number and therefore present it as a hypothesis, not an established result. The practical “sweet spot” practitioners cite is 100–200 g carbs/day from whole-food sources (rice, potatoes, fruit) — reasonable as guidance, but unproven as a dose-response claim. None of the registered retatrutide or semaglutide trials controlled dietary carbohydrate as a variable, so the carb-sensitivity differential between the two compounds remains a mechanistic extrapolation awaiting direct study.

Why this matters for the comparison: because semaglutide works primarily as an appetite suppressant and depends less heavily on glucose-dependent insulin optimization, it appears less sensitive to dietary carbohydrate than retatrutide. This is the most likely explanation for anecdotal reports that “carnivore + retatrutide didn’t work, but semaglutide/tirzepatide did.” If a prospective user is committed to a ketogenic diet, semaglutide’s mechanism is less likely to be sabotaged by that choice — a genuinely practical decision factor.

A related vault-unique point: mitochondrial function is a prerequisite for GLP-1-agonist efficacy generally, but it matters most for retatrutide, because retatrutide leans hardest on fat oxidation (via the glucagon receptor) to do its work. Users who “do everything right” but respond poorly to retatrutide may have underlying mitochondrial dysfunction (driven by oxidative stress, inflammation, nutrient deficiencies, chronic caloric excess, or aging). The implication is to assess and support metabolic/mitochondrial health alongside any incretin therapy — and to expect retatrutide, specifically, to be the more “demanding” of the two on metabolic substrate and machinery.

Switching & Stacking Considerations

Do not stack them. Retatrutide and semaglutide have overlapping GLP-1 mechanisms; running them together adds GI toxicity and offers no clean additive benefit. The VialBase library is explicit that retatrutide should not be combined with semaglutide or Tirzepatide — these are alternatives, not components of a stack. The same applies to semaglutide and tirzepatide: patients switch between them for efficacy, they don’t run them concurrently.

Switching direction. The typical escalation ladder in this class is mono → dual → triple agonist (semaglutide → tirzepatide → retatrutide) as users seek more weight loss or hit a plateau. Because retatrutide is investigational, “switching to retatrutide” means moving from an approved drug to a research compound — a regulatory and safety downgrade even if the efficacy ceiling is higher. There is no published, validated cross-titration protocol between these compounds (none exists in the peer-reviewed literature or the VialBase library); the long half-lives (~6–7 days) mean meaningful overlap persists for weeks after stopping either one — the main pharmacokinetic caution when transitioning.

Adjuncts commonly paired with either (for side-effect management, not efficacy stacking):

• BPC-157 — gut protection / GI side-effect mitigation during titration (cited at 250–500 mcg/day in research contexts).
• Ipamorelin and/or CJC-1295 — GH-axis support to help preserve lean mass; the rationale is stronger for retatrutide given its glucagon-driven catabolism concern.
• TB-500 — sometimes cited with retatrutide for connective-tissue support against catabolic effects.
• NAD+ — metabolic / cellular-energy support during a caloric deficit (aligned with the mitochondrial point above).

These adjuncts are themselves research peptides (not FDA-approved for these uses), presented as educational context, not protocols.

Legal & Sourcing Reality

This is where the two compounds diverge most sharply, and where honest framing matters most. There are effectively three tiers of supply, and they are not equivalent.

1. Approved pharmaceuticals (semaglutide only). Ozempic, Wegovy, and Rybelsus are FDA-approved, prescription-only products manufactured to pharmaceutical standards. This is the only tier with full regulatory oversight, defined purity, and an established safety/quality chain. Semaglutide is also approved across the EU (EMA), UK (MHRA), Japan (PMDA), and 100+ countries. Retatrutide has no equivalent tier — it is not approved anywhere.

2. Compounded semaglutide (legally contested, evolving). Under FDA 503A, semaglutide was compoundable while on the drug-shortage list. The FDA has since stated the shortage is resolved and moved to restrict compounding, with litigation ongoing as of 2026. Compounded vials are cheaper than branded pens but occupy a shifting legal gray zone, and quality varies by pharmacy. Retatrutide is not legally compoundable — it has never been FDA-approved and has never been on any shortage list, so there is no 503A basis for it. The FDA has issued warning letters to research-peptide vendors selling retatrutide for human use.

3. Gray-market “research” vials (both — buyer beware). Both compounds are sold by research-peptide vendors labeled “for research use only, not for human consumption.” For retatrutide this is the only available channel, and there is no USP monograph or compendial standard for it — no official quality-control reference exists. For semaglutide, gray-market vials are explicitly not the approved product even though an approved product exists; buying “research” semaglutide does not get you Ozempic-grade material. In both cases, third-party testing (HPLC + mass spectrometry) with publicly posted certificates of analysis (COAs) is the single most important sourcing criterion, because purity and labeling accuracy vary widely.

Other status notes. Neither is a DEA-controlled substance. For sport: semaglutide is not prohibited by WADA (athletes may use with a valid prescription); retatrutide is not specifically named but is covered under WADA category S0 (non-approved substances) and athletes should avoid it.

For readers sourcing research-grade material, VialBase prioritizes vendors that publish third-party COAs and ship with cold-chain handling. Affiliate disclosure: VialBase may earn a commission if you purchase through vendor links, at no extra cost to you. This does not influence our research-based assessments. Approved-drug access (Ozempic/Wegovy/Rybelsus) should go through a licensed prescriber, not a research vendor.

Frequently Asked Questions

Is retatrutide stronger than semaglutide? On weight-loss percentage, yes — retatrutide’s Phase 2 produced ~24% body-weight loss at 48 weeks versus semaglutide’s ~15% in Phase 3 (STEP). But these are different trial stages: semaglutide’s number is from large, completed Phase 3 trials with safety and cardiovascular-outcome data, while retatrutide’s is earlier, smaller, and partly unverified.

Is retatrutide FDA-approved? No. Retatrutide is investigational and not approved in any country. It is in Eli Lilly’s Phase 3 TRIUMPH program, with an NDA submission expected around 2027 if results are positive. Semaglutide, by contrast, has been FDA-approved since 2017 (Ozempic), with Wegovy (2021) and Rybelsus (2019) following.

Why does retatrutide cause more weight loss? The third receptor. Both drugs suppress appetite via GLP-1, but retatrutide adds GIP (better insulin sensitivity) and glucagon agonism, which increases resting energy expenditure and directly oxidizes fat in the liver. Semaglutide only reduces intake; retatrutide reduces intake and increases energy expenditure.

Can I take retatrutide and semaglutide together? No. They share overlapping GLP-1 mechanisms, so combining them stacks gastrointestinal toxicity without a clean additive benefit. They are alternatives, not a stack — users switch between incretin drugs (typically mono → dual → triple agonist) rather than running them concurrently.

Does diet affect these drugs differently? Yes, and this is underappreciated. Retatrutide’s incretin (GLP-1/GIP) effects are glucose-dependent, so very-low-carb and ketogenic diets can blunt its mechanism; a moderate-carb intake (~100–200 g/day) appears to support efficacy. Semaglutide works more as a pure appetite suppressant and is less sensitive to carbohydrate intake.

Which has the worse side effects? Both share the GLP-1 class’s GI profile (nausea, diarrhea, vomiting, constipation), worst during titration. In cross-trial data, retatrutide’s nausea rates read somewhat lower (possibly the GIP arm’s effect), but retatrutide carries added concerns from glucagon — mild heart-rate increase, potential extra lean-mass loss, and, most importantly, no long-term safety data.

Will I keep the weight off if I stop? Probably not, for either drug. Semaglutide’s STEP 4 trial showed that stopping leads to regaining roughly two-thirds of the lost weight, and cardiometabolic gains reversed too. Both compounds appear to be ongoing therapies rather than one-time cures; the same maintenance dynamic is expected for retatrutide.

Is “research-grade” semaglutide the same as Ozempic? No. Gray-market semaglutide vials labeled “research use only” are not FDA-approved products and are not manufactured to pharmaceutical standards, even though an approved version (Ozempic/Wegovy/Rybelsus) exists. Approved semaglutide should be obtained through a licensed prescriber; research vials of either compound carry purity and labeling risks and should at minimum come with third-party COAs.

References

1. PMID: 33567185 — Wilding et al., N Engl J Med, 2021. Wilding JPH, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity. N Engl J Med. 2021;384(11):989–1002. STEP 1: semaglutide 2.4 mg → 14.9% body-weight loss vs placebo in overweight/obese adults without diabetes.
2. PMID: 33755728 — Rubino et al., JAMA, 2021. Rubino D, et al. Effect of Continued Weekly Subcutaneous Semaglutide vs Placebo on Weight Loss Maintenance in Adults With Overweight or Obesity: The STEP 4 Randomized Clinical Trial. JAMA. 2021;325(14):1414–1425. STEP 4: discontinuation regains ~two-thirds of lost weight.
3. PMID: 36216945 — Garvey et al., Nat Med, 2022. Garvey WT, et al. Two-year effects of semaglutide in adults with overweight or obesity: the STEP 5 trial. Nat Med. 2022;28(10):2083–2091. STEP 5: sustained 15.2% weight loss over 104 weeks.
4. PMID: 35015037 — Rubino et al., JAMA, 2022. Rubino DM, et al. Effect of Weekly Subcutaneous Semaglutide vs Daily Liraglutide on Body Weight in Adults With Overweight or Obesity Without Diabetes: The STEP 8 Randomized Clinical Trial. JAMA. 2022;327(2):138–150. STEP 8: semaglutide 2.4 mg (15.8%) vs liraglutide 3.0 mg (6.4%) head-to-head.
5. PMID: 37952131 — Lincoff et al., N Engl J Med, 2023. Lincoff AM, et al. Semaglutide and Cardiovascular Outcomes in Obesity without Diabetes. N Engl J Med. 2023;389(24):2221–2232. SELECT: 20% MACE reduction (HR 0.80, 95% CI 0.72–0.90) with semaglutide 2.4 mg in obesity with CVD, without diabetes.
6. PMID: 27633186 — Marso et al., N Engl J Med, 2016. Marso SP, et al. Semaglutide and Cardiovascular Outcomes in Patients with Type 2 Diabetes. N Engl J Med. 2016;375(19):1834–1844. SUSTAIN-6: 26% reduction in MACE (HR 0.74, 95% CI 0.58–0.95) in high-CV-risk T2D.
7. PMID: 38785209 — Perkovic et al., N Engl J Med, 2024. Perkovic V, et al. Effects of Semaglutide on Chronic Kidney Disease in Patients with Type 2 Diabetes. N Engl J Med. 2024;391(2):109–121. FLOW: 24% reduction in major kidney-disease events (HR 0.76, 95% CI 0.66–0.88) in T2D + CKD.
8. PMID: 38958939 — Hathaway et al., JAMA Ophthalmol, 2024. Hathaway JT, et al. Risk of Nonarteritic Anterior Ischemic Optic Neuropathy in Patients Prescribed Semaglutide. JAMA Ophthalmol. 2024;142(8):732–739. Retrospective Mass Eye and Ear cohort reporting an association between semaglutide prescription and NAION (observational; not established causation).
9. PMID: 37366315 — Jastreboff et al., N Engl J Med, 2023. Jastreboff AM, et al. Triple–Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial. N Engl J Med. 2023;389(6):514–526. Retatrutide Phase 2 obesity: up to 24.2% body-weight loss at 48 weeks (12 mg).
10. PMID: 37385280 — Rosenstock et al., Lancet, 2023. Rosenstock J, et al. Retatrutide, a GIP, GLP-1 and glucagon receptor agonist, for people with type 2 diabetes: a randomised, double-blind, placebo and active-controlled, parallel-group, phase 2 trial conducted in the USA. Lancet. 2023;402(10401):529–544. Retatrutide Phase 2 T2D: HbA1c reduction up to −2.02%; weight loss up to −16.94% (12 mg).
11. PMID: 38858523 — Sanyal et al., Nat Med, 2024. Sanyal AJ, et al. Triple hormone receptor agonist retatrutide for metabolic dysfunction-associated steatotic liver disease: a randomized phase 2a trial. Nat Med. 2024;30(7):2037–2048. Retatrutide Phase 2a MASLD: >80% relative liver-fat reduction at 12 mg over 48 weeks.
12. PMID: 35658024 — Jastreboff et al., N Engl J Med, 2022. Jastreboff AM, et al. Tirzepatide Once Weekly for the Treatment of Obesity. N Engl J Med. 2022;387(3):205–216. SURMOUNT-1 (tirzepatide) — included as dual-agonist context bridging semaglutide and retatrutide.
13. PMID: 41966712 — Zhang et al., Med, 2026. Zhang X, et al. MASH and liver fibrosis: clinical trials to watch. Med. 2026. Review of MASH clinical trials including semaglutide (59% resolution; conditional FDA approval context).
14. PMID: 41090431 — Giblin et al., Diabetes Obes Metab, 2026. Retatrutide for the treatment of obesity, obstructive sleep apnea and knee osteoarthritis: Rationale and design of the TRIUMPH registrational clinical trials. Diabetes Obes Metab. 2026. Cited for the existence and design of the Phase 3 TRIUMPH program only — this is a protocol/design paper, not an efficacy readout.
15. Retatrutide TRIUMPH Phase 3 first readout (~29% average weight loss / ~74 lb) — not peer-reviewed. This figure circulates from a single non-peer-reviewed source (a video analysis of an unpublished topline readout) and is not supported by any published trial or an Eli Lilly press release we could verify. Treat as unverified until Eli Lilly publishes the TRIUMPH results in a peer-reviewed journal.
16. Carbohydrate / incretin-efficacy figure (~40% greater efficacy with moderate vs low carb) — not independently verifiable. Attributed to the Dr. Trevor Bachmeyer “Retatrutide Masterclass” (YouTube); no primary peer-reviewed publication (the previously-cited “J Clin Endocrinol Metab 2022” could not be located) supports the specific figure. Presented in-text as a mechanistic hypothesis, not an established clinical result.
17. Internal: VialBase compound profiles for Semaglutide and Retatrutide; knowledge notes Retatrutide requires carbohydrates for optimal efficacy and Mitochondrial function is prerequisite for GLP-1-agonist efficacy. Practitioner context (carbohydrate/mitochondrial framing) attributed to Dr. Trevor Bachmeyer and presented as hypothesis, not trial data.