The field of incretin-based therapeutics has undergone a remarkable transformation since the approval of exenatide in 2005. First-generation GLP-1 receptor agonists primarily targeted glucose homeostasis with modest weight-loss effects. Second-generation agents like semaglutide demonstrated that targeting the GLP-1 receptor with high potency and extended half-lives could yield substantial weight reduction of 12–17%. Now, third-generation multi-agonists — targeting two or three incretin and metabolic receptors simultaneously — are pushing efficacy boundaries toward and beyond what was once achievable only with bariatric surgery.
The year 2025 was transformative for the class, with 16.4% of all GLP-1-related clinical trials initiated during this period — the highest annual proportion on record. Two major trends are reshaping the pipeline: the development of oral small-molecule GLP-1 agonists that eliminate injection-related barriers, and unimolecular multi-receptor agonists that exploit synergistic signalling pathways across GLP-1, GIP, and glucagon receptors. The result is a therapeutic landscape with unprecedented depth and diversity.
Generational Evolution of Incretin Therapies
Exenatide, liraglutide — short-acting peptides, once/twice daily injection, 5–8% weight loss. Primary focus on glycaemic control in T2DM.
Semaglutide, dulaglutide — long-acting, once-weekly, 12–17% weight loss. Expanded indications to obesity and cardiovascular protection (SELECT trial).
Tirzepatide, retatrutide, CagriSema — multi-receptor agonists, 20–29% weight loss. Targets: obesity, MASH, CKD, OSA, heart failure, Alzheimer's disease.
Retatrutide (LY3437943)
Mechanism of Action
Retatrutide is a first-in-class, once-weekly, subcutaneous triple hormone receptor agonist — a single synthetic molecule that simultaneously activates the GIP, GLP-1, and glucagon receptors. The addition of glucagon receptor agonism is hypothesised to enhance energy expenditure, hepatic lipid oxidation, and thermogenesis beyond what GLP-1/GIP dual agonism alone can achieve.
Key Phase 3 Data — TRIUMPH-4 (December 2025)
In the first Phase 3 readout, TRIUMPH-4 (NCT05931367) evaluated retatrutide in adults with obesity/overweight and knee osteoarthritis over 68 weeks. The trial enrolled participants where 84% had a baseline BMI ≥35 kg/m². Both doses met all primary and key secondary endpoints:
- Weight loss (12 mg): −28.7% from baseline (average 71.2 lbs / 32.3 kg lost)
- Weight loss (9 mg): −26.4% from baseline (average 29.1 kg lost)
- Placebo: −2.1% (2.1 kg lost)
- WOMAC pain reduction (12 mg): −4.4 points (75.8% improvement from baseline)
- Pain freedom: 12–14% of retatrutide-treated patients reported complete freedom from knee pain versus 4.2% on placebo
- Cardiovascular markers: Significant reductions in non-HDL-C, triglycerides, hsCRP; systolic BP reduction of 14.0 mmHg at highest dose
Safety Profile
Gastrointestinal adverse events were consistent with the incretin class: nausea (43%), diarrhea (33%), vomiting (21%), and decreased appetite. Discontinuation rates due to AEs were 12.2% (9 mg) and 18.2% (12 mg) versus 4% on placebo. A new safety signal — dysesthesia (abnormal touch sensation) — was observed at rates of 8.8% (9 mg) and 20.9% (12 mg) versus 0.7% on placebo. These events were generally mild and rarely led to discontinuation.
Ongoing TRIUMPH Programme
- TRIUMPH-1/2: Obesity ± OSA basket trials (5 doses: 2, 4, 6, 9, 12 mg) — results expected 2026
- TRIUMPH-3: Obesity in patients with established CVD — results expected 2026
- TRIUMPH-5: Head-to-head vs tirzepatide in obesity
- TRIUMPH-6: Phase 3b weight maintenance study
- TRIUMPH-Outcomes: Event-driven CV/renal outcomes trial (MACE + CKD endpoints)
- MASLD/MASH trials: Evaluating liver-related outcomes
Projected Commercial Impact
Industry analysts project FDA approval in 2027, with forecast sales of approximately $15.6 billion by 2031. Seven additional Phase 3 readouts are expected throughout 2026.
Survodutide
Boehringer Ingelheim — GLP-1/Glucagon Dual Agonist
An oxyntomodulin-mimetic dual agonist. Phase 2 demonstrated up to 19.0% weight loss at 46 weeks (4.8 mg dose) with no plateau observed. Additionally showed remarkable MASH efficacy: 62% of patients on 4.8 mg achieved MASH improvement without fibrosis worsening. Three Phase 3 trials are underway: SYNCHRONIZE-1 (obesity ± comorbidities), SYNCHRONIZE-2 (obesity + T2DM), and SYNCHRONIZE-CVOT (CV outcomes).
VK2735
Viking Therapeutics — GLP-1/GIP Dual Agonist
Dual GLP-1/GIP receptor agonist available in both subcutaneous and oral formulations. Phase 2 VENTURE trial showed 14.7% weight reduction in just 13 weeks (15 mg SC) with no plateau observed. Additionally, 78% of prediabetic patients normalised glycaemic status. Oral formulation demonstrated 6.8% weight loss in 28 days (Phase 1). Phase 3 initiated in 2025; FDA approval projected 2028+.
MariTide (AMG 133)
Amgen — GLP-1 Agonist / GIP Antagonist
A novel bispecific antibody conjugate that combines GLP-1 receptor agonism with GIP receptor antagonism — a unique "activate/block" approach validated by human genetics. Phase 2 data demonstrated 20% weight loss at 52 weeks with monthly dosing, with no observed plateau. The monthly injection frequency is a major differentiator from weekly competitors.
Pemvidutide
Altimmune — GLP-1/Glucagon Dual Agonist
A once-weekly dual GLP-1/glucagon agonist with notable lean mass preservation (lean loss ratio of only 21.9%) and preferential visceral fat reduction. Phase 2 MOMENTUM showed 15.6% weight loss at 48 weeks (2.4 mg). Liver data is exceptional: 76.4% relative reduction in liver fat at 24 weeks. The VELOCITY Phase 3 programme includes trials for obesity, lipid lowering, liver fat, and body composition in older adults.
CT-388
Roche/Carmot Therapeutics — GLP-1/GIP Dual Agonist
A once-weekly subcutaneous unimolecular GLP-1/GIP agonist. Phase 1b data showed 18.8% placebo-adjusted weight loss at 24 weeks with mild-to-moderate GI side effects. Phase 1 demonstrated >8% weight loss in just 4 weeks. Currently in Phase 2 for both obesity and T2DM.
Mazdutide (IBI362)
Innovent Biologics — GLP-1/Glucagon Dual Agonist
A dual GLP-1/glucagon agonist with completed Phase 3 data from the GLORY-1 trial in Chinese adults with obesity. 610 participants were randomised to 4 mg, 6 mg, or placebo. Demonstrated significant weight loss with a profile consistent with the GLP-1 class. Additional Phase 3 trials are underway.
The development of oral GLP-1 agonists represents a pivotal shift in the treatment landscape. While oral semaglutide (Rybelsus) was the first oral GLP-1 RA, it is a peptide requiring specific dosing conditions (fasting, limited water). The next generation of oral agents includes non-peptide small molecules that can be taken without food restrictions and do not require refrigeration — dramatically improving patient convenience and potentially expanding the treatable population.
Orforglipron
Key Differentiators
- Non-peptide: Small molecule that does not require absorption enhancers or fasting
- Room temperature storage: No refrigeration required
- Once-daily dosing: Can be taken regardless of meals
- Oral bioavailability: Overcomes the limitations of peptide-based oral formulations
Phase 3 Efficacy — ATTAIN Programme
The ATTAIN-1 trial (NCT05869903) evaluated orforglipron at doses of 6 mg, 12 mg, and 36 mg versus placebo over 72 weeks in adults with obesity. All doses achieved significantly greater body weight reduction than placebo. At the highest 36 mg dose, patients achieved approximately 11% weight loss at 72 weeks.
In head-to-head trials for T2DM, orforglipron demonstrated superiority over semaglutide in HbA1c reduction and non-inferiority to AstraZeneca's dapagliflozin (Farxiga). Lilly has submitted an FDA application, with a potential approval decision anticipated in Q2 2026.
Safety Profile
The adverse event profile was consistent with the GLP-1 class, with predominantly gastrointestinal side effects (nausea, vomiting, diarrhea). Events were generally mild to moderate and decreased over time with dose escalation.
Oral Semaglutide 50 mg (Wegovy Pill)
Overview
Novo Nordisk launched a higher-dose oral semaglutide (50 mg) formulation for obesity in January 2026, building on the established oral semaglutide platform (Rybelsus, approved for T2DM at 7 and 14 mg). This higher dose aims to achieve weight-loss efficacy approaching the injectable Wegovy formulation. The oral Wegovy became the first oral GLP-1 RA approved for weight management.
The agent retains the peptide-based formulation requiring SNAC (sodium N-[8-(2-hydroxybenzoyl) amino] caprylate) absorption enhancer, fasting conditions, and limited water volume at dosing — positioning it as an intermediate option between injectable semaglutide and the truly meal-independent non-peptide oral agents.
Danuglipron
Development Status
Pfizer's small-molecule oral GLP-1 agonist demonstrated 8–13% placebo-adjusted weight loss at 32 weeks in Phase 2b. However, the twice-daily formulation was associated with high GI adverse event rates (nausea up to 73%, vomiting 47%) and significant discontinuation. Pfizer elected not to advance the twice-daily version into Phase 3 and is pursuing a once-daily formulation with improved tolerability. Dose optimisation studies are ongoing.
Oral Formulation Comparison
The oral GLP-1 landscape is rapidly maturing. Orforglipron (Lilly) leads in clinical development with FDA filing complete, followed by oral semaglutide 50 mg (Novo Nordisk, launched), and oral VK2735 (Viking, Phase 1/2). Each offers different trade-offs between potency, convenience, storage requirements, and dosing flexibility. The non-peptide agents (orforglipron, danuglipron) offer the greatest patient convenience with no fasting or water restrictions.
CagriSema (Cagrilintide + Semaglutide 2.4 mg)
Mechanism & Rationale
CagriSema is a once-weekly subcutaneous co-formulation combining cagrilintide (a long-acting amylin analogue) with semaglutide 2.4 mg. Amylin, a hormone co-secreted with insulin from pancreatic β-cells, complements GLP-1 signalling by activating distinct satiety pathways in the area postrema and the hypothalamus. This dual-mechanism approach produces additive — and potentially synergistic — effects on appetite suppression and energy balance.
REDEFINE Phase 3 Programme Results
- REDEFINE-1: CagriSema achieved 22.7% mean body weight loss at 68 weeks vs 16.1% with semaglutide alone — a statistically significant 6.6 percentage point advantage (p<0.001)
- 23% of CagriSema-treated patients achieved ≥30% weight loss
- Completers analysis: approximately 23% weight loss among those remaining on treatment
- Safety profile consistent with the GLP-1 class; no unexpected signals
Ongoing & Planned REDEFINE Trials
- REDEFINE-2: CagriSema in obesity + T2DM
- REDEFINE-4: Head-to-head comparison vs tirzepatide
- REDEFINE-11 (NCT07011667): Extended treatment duration and re-escalation strategies targeting >25% weight loss (initiated June 2025)
- REDEFINE-CVOT: Cardiovascular outcomes trial
Amycretin
Key Data
Unlike CagriSema (a two-molecule co-formulation), amycretin is a single peptide molecule engineered to activate both GLP-1 and amylin receptors. Early Phase 2 results generated significant excitement by demonstrating approximately 22% body weight reduction in just 36 weeks — matching CagriSema's 68-week efficacy in roughly half the time. If confirmed in larger trials, amycretin could represent a major advance in weight-loss velocity. Further Phase 2/3 data are anticipated.
| Agent | Company | Receptor Target(s) | Route | Phase | Key Efficacy | Key Trial(s) |
|---|---|---|---|---|---|---|
| Retatrutide | Eli Lilly | GIP + GLP-1 + GCGR | SC QW | Phase 3 | −28.7% (68 wk) | TRIUMPH 1–6, Outcomes |
| CagriSema | Novo Nordisk | GLP-1 + Amylin | SC QW | Filing | −22.7% (68 wk) | REDEFINE 1–4, 11, CVOT |
| Orforglipron | Eli Lilly | GLP-1 | Oral QD | Filing | −11% (72 wk) | ATTAIN 1–4 |
| Survodutide | Boehringer Ingelheim | GLP-1 + GCGR | SC QW | Phase 3 | −19.0% (46 wk) | SYNCHRONIZE 1–3 |
| VK2735 | Viking Therapeutics | GLP-1 + GIP | SC QW / Oral | Phase 3 | −14.7% (13 wk) | VENTURE, Phase 3 |
| Amycretin | Novo Nordisk | GLP-1 + Amylin | SC / Oral | Phase 2 | −22% (36 wk) | Phase 2 Obesity |
| MariTide | Amgen | GLP-1 ago / GIP antag | SC Q4W | Phase 2 | −20% (52 wk) | Phase 2 Obesity |
| CT-388 | Roche/Carmot | GLP-1 + GIP | SC QW | Phase 2 | −18.8% (24 wk) | Phase 1b/2 |
| Pemvidutide | Altimmune | GLP-1 + GCGR | SC QW | Phase 3 | −15.6% (48 wk) | VELOCITY 1–4 |
| Mazdutide | Innovent Biologics | GLP-1 + GCGR | SC QW | Phase 3 | Phase 3 data | GLORY-1, 2+ |
| Danuglipron | Pfizer | GLP-1 | Oral QD | Dose Opt. | −8–13% (32 wk) | Phase 2b |
| Oral Sema 50 mg | Novo Nordisk | GLP-1 | Oral QD | Approved | Phase 3 data | Launched Jan 2026 |
| Sema 7.2 mg | Novo Nordisk | GLP-1 | SC QW | Phase 3b | −18.7% (72 wk) | STEP UP |
Interpretation Caveats
Direct cross-trial comparisons have significant limitations. Trial populations, duration, dose escalation schedules, baseline BMI, and endpoint definitions vary substantially between studies. Only head-to-head trials (e.g., TRIUMPH-5 retatrutide vs tirzepatide; REDEFINE-4 CagriSema vs tirzepatide) can provide definitive comparative efficacy data. Weight-loss trajectory (rate and plateau status) is as clinically relevant as the final magnitude. *Amycretin's 22% at 36 weeks is particularly noteworthy given the shorter treatment duration.
Receptor Contributions to Metabolic Efficacy
Appetite suppression via hypothalamic and brainstem signalling. Glucose-dependent insulinotropic effect. Delayed gastric emptying. Cardioprotective effects (anti-inflammatory, endothelial function). Central mechanism for weight loss across all agents.
Enhanced insulin sensitivity and adipose tissue function. Potentiates GLP-1-mediated weight loss. May improve bone metabolism. Tissue-specific effects on fat distribution. Activated by tirzepatide, VK2735, CT-388. GIP antagonism (MariTide) also shows efficacy, suggesting complex receptor biology.
Hepatic lipid oxidation and increased energy expenditure via thermogenesis. Directly reduces liver fat content — critical for MASH. Synergises with GLP-1 for superior weight loss. Activated by retatrutide, survodutide, pemvidutide, mazdutide.
Complementary satiety pathway via area postrema activation. Slows gastric emptying and reduces postprandial glucagon. Works through distinct neural circuits from GLP-1, enabling additive appetite suppression. Targeted by CagriSema and amycretin.
The rationale for multi-receptor agonism extends beyond simple additive pharmacology. GLP-1 + GIP co-agonism (tirzepatide model) exploits complementary incretin pathways to enhance insulin sensitivity and potentiate weight loss. GLP-1 + glucagon co-agonism (survodutide, pemvidutide) adds direct hepatic lipid metabolism and thermogenesis — particularly valuable for MASH and visceral adiposity. GLP-1 + GIP + glucagon triple agonism (retatrutide) combines all three mechanisms, producing the highest weight-loss magnitudes observed to date.
Emerging research on biased agonism — where different ligands preferentially activate G-protein versus β-arrestin signalling pathways — may enable future agents to retain efficacy while reducing gastrointestinal side effects. Understanding these intracellular signalling distinctions represents a key frontier in next-generation drug design.
Common Class Effects (All GLP-1-Based Agents)
- Nausea: 20–50% (typically decreasing with continued use)
- Vomiting: 10–25%
- Diarrhoea: 15–35%
- Constipation: 10–25%
- Decreased appetite: Common and often therapeutically beneficial
- Injection site reactions: Mild with SC formulations
- Heart rate increase: 2–9 bpm (generally asymptomatic)
Gallbladder & Pancreatic
- Increased rates of cholelithiasis/cholecystitis with greater weight loss
- No significant increase in pancreatitis vs placebo in large trials
- Monitoring recommended for symptoms of gallbladder disease
Emerging Safety Signals — Novel Agents
- Retatrutide — Dysesthesia: Abnormal touch sensation reported in 8.8% (9 mg) to 20.9% (12 mg) vs 0.7% placebo in TRIUMPH-4. Not seen in Phase 2. Generally mild, rarely led to discontinuation. Unique to the triple agonist — mechanism unclear, may relate to glucagon receptor effects.
- Perceived excessive weight loss: Some discontinuations in TRIUMPH-4 attributed to weight loss velocity exceeding patient expectations, particularly at lower baseline BMIs
- Lean mass loss: A class concern — typically 20–30% of total weight lost is lean mass. Pemvidutide may preserve more lean mass (lean loss ratio 21.9%, better in patients ≥60 years). Exercise and protein intake remain essential adjuncts.
Discontinuation Rates
- Retatrutide: 12.2% (9 mg), 18.2% (12 mg) due to AEs
- Danuglipron (BID): High discontinuation → reformulation required
- Most agents: dose-escalation protocols mitigate early GI events
Clinical Monitoring Recommendations for Novel Agents
As these agents advance, clinicians should maintain vigilance for novel safety signals beyond the established GLP-1 class profile. Retatrutide's dysesthesia signal warrants careful monitoring in upcoming TRIUMPH readouts. All patients on potent weight-loss agents should be monitored for nutritional deficiencies, gallbladder symptoms, lean mass preservation (consider DXA scanning), and psychological wellbeing related to rapid body composition changes. Dose-dependent effects and adequate escalation schedules remain critical to tolerability.
Cardiovascular Disease
SELECT trial demonstrated semaglutide reduces MACE by 20% in obese adults with established CVD. TRIUMPH-Outcomes and SYNCHRONIZE-CVOT are evaluating next-gen agents for CV endpoints. Tirzepatide CV outcomes trials (SURPASS-CVOT) are ongoing with completion expected 2027.
MASH / Liver Disease
Semaglutide 2.4 mg received FDA accelerated approval for MASH (August 2025, ESSENCE trial). Survodutide demonstrated 62% MASH improvement in Phase 2. Pemvidutide achieved 76% liver fat reduction at 24 weeks. Retatrutide's glucagon component provides direct hepatic benefit.
Obstructive Sleep Apnoea
Tirzepatide is approved for moderate-to-severe OSA in obese adults (2024). Retatrutide's TRIUMPH programme includes nested OSA protocols within the basket trial design. Weight-independent mechanisms may contribute to improved AHI scores.
Neurological Disorders
Multiple trials are investigating GLP-1 RAs in Alzheimer's disease and Parkinson's disease, leveraging neuroprotective, anti-inflammatory, and brain energy metabolism properties. Completion of Alzheimer's trials will establish disease-modifying potential.
Musculoskeletal Disease
TRIUMPH-4 demonstrated significant improvement in knee OA pain (76% WOMAC improvement) and physical function with retatrutide. 12–14% of treated patients achieved complete pain freedom. Chronic low back pain is also under investigation.
Chronic Kidney Disease
The FLOW trial showed semaglutide reduced renal composite endpoints in CKD patients. Tirzepatide is being studied in CKD (TREASURE CKD). TRIUMPH-Outcomes and SYNCHRONIZE-CVOT include renal endpoints. GLP-1 RAs enhance renal perfusion via ANP signalling.
Heart Failure (HFpEF)
STEP-HFpEF trials demonstrated semaglutide improves NYHA functional class (32.6% vs 21.5% improved by ≥1 class). Wegovy resubmitted for HFpEF indication. GLP-1 agents may address the obesity-HFpEF phenotype directly.
Long COVID
Scripps Research initiated the LoCITT digital clinical trial exploring tirzepatide for long COVID symptom relief, leveraging anti-inflammatory effects. Remote trial design with wearable devices and home-delivered medications represents a novel trial paradigm.
Research Frontiers
Understanding β-arrestin vs G-protein signalling pathways to design agents with enhanced therapeutic windows and reduced GI side effects.
Strategies to preferentially preserve lean mass during pharmacological weight loss: combination with myostatin inhibitors, exercise prescriptions, protein targets, anabolic adjuncts.
Monthly (MariTide) and potentially quarterly injection formulations to improve long-term adherence. Implantable sustained-release systems under investigation.
Pharmacogenomics and biomarker-guided selection of optimal agents. Which receptor combination profile best suits an individual's metabolic phenotype?