Overview
Drug Class Taxonomy
Structural classification and therapeutic positioning
GLP-1 receptor agonists are classified by their structural origin, half-life strategy, and receptor selectivity. The field has evolved from simple peptide analogues of native GLP-1 to sophisticated multi-receptor co-agonists and, most recently, oral non-peptide small molecules — a trajectory from parenteral peptides to daily oral tablets that mirrors the historical arc of insulin therapy.
The classification used here distinguishes seven generations based on primary pharmacological innovation:
I
Exendin-4 analogues — Short-acting, non-human peptide
Exenatide IR · Lixisenatide · Derived from Gila monster venom peptide · 53% GLP-1 homology
II
Fatty acid–acylated GLP-1 analogues — Once daily
Liraglutide · ≥94% GLP-1 homology · Albumin-binding via palmitoyl chain · 13 h half-life
III
Ultra-long-acting peptides — Once weekly
Semaglutide · Dulaglutide · Efpeglenatide · Fatty diacid or Fc-fusion strategies · 5–7 day t½
IV
Dual GIP/GLP-1 co-agonists — Comparative weight-management evidence
Tirzepatide · Full GIPR + partial GLP-1R agonism · Once weekly · Up to 22.5% weight loss
V
Triple agonists — GIP + GLP-1 + Glucagon receptor
Retatrutide · Investigational triple agonist · Mazdutide is a GLP-1/glucagon dual agonist
VI
Oral small-molecule GLP-1 RAs — Non-peptide
Orforglipron: UK authorised · Danuglipron and lotiglipron: discontinued development
VII
Novel co-agonist & combination strategies — 2027–2030
GLP-1/amylin · GLP-1/FGF21 · GLP-1/GCG · Brain-biased variants · Monthly / implant delivery
Timeline
Regulatory Approval History
FDA and EMA approvals 2005–2026 and projected beyond
2005 · FDA
Exenatide (Byetta)
First GLP-1 RA approved · T2DM · Twice daily SC · Amylin/Eli Lilly
2010 · FDA / EMA
Liraglutide (Victoza)
First once-daily GLP-1 RA · T2DM · Novo Nordisk · Later approved Saxenda 2014 (obesity)
2012 · FDA / EMA
Exenatide XR (Bydureon) & Lixisenatide (Lyxumia)
First once-weekly GLP-1 RA (Bydureon) · Lixisenatide — strong postprandial effect, low CV data
2014–2017 · FDA / EMA
Albiglutide (Tanzeum) · Dulaglutide (Trulicity) · Semaglutide SC (Ozempic)
Albiglutide: Fc-fusion, later withdrawn commercially 2018 · Dulaglutide: pen device · Semaglutide: highest efficacy peptide of its era
2019 · FDA
Oral Semaglutide (Rybelsus)
First oral GLP-1 RA · SNAC absorption enhancer · T2DM · EMA 2020 · NICE approval 2022
2021 · FDA · EMA 2022
Semaglutide 2.4 mg (Wegovy)
Obesity indication · STEP programme · 15% mean weight loss · NICE approval 2023
2022 · FDA · UK weight management 2023
Tirzepatide (Mounjaro; Zepbound is US branding)
First dual GIP/GLP-1 RA · UK-authorised for T2DM and weight management · NICE TA1026 / NG28
Development pipeline · verify current status
Retatrutide · Orforglipron · CagriSema
Retatrutide and CagriSema: investigational · Orforglipron: UK authorised August 2026
2027–2030 · Projected
Monthly / implant · GLP-1/FGF21 · Brain-biased agents
Ultra-long-acting formulations · Subcutaneous implants · Tissue-specific GLP-1 agonism · Combination pharmacology with SGLT2i
Generation I
Current UK status: Exenatide is no longer marketed in the UK. Lixisenatide is no longer authorised, according to the MHRA communication of 29 January 2026. The following profiles describe historical pharmacology and trial evidence, not current UK initiation options.
Exendin-4 Analogues
Short-acting · Non-human peptide origin · 53% GLP-1 homology
The first generation of GLP-1 RAs is structurally derived from exendin-4, a 39-amino-acid peptide isolated from the venom of the Gila monster (Heloderma suspectum). Despite only 53% sequence identity with human GLP-1, exendin-4 binds and activates the human GLP-1 receptor with high affinity — and crucially, its position-2 glycine substitution (vs alanine in GLP-1) confers complete resistance to DPP-4 cleavage. This provided the structural proof of concept that a non-human peptide could form the basis of effective GLP-1R agonist therapy.
Origin
Exendin-4 (Gila monster)
GLP-1 Homology
53% sequence identity
XR half-life
~2 weeks (PLGA depot)
IR dosing
5–10 mcg SC twice daily
XR dosing
2 mg SC once weekly
Elimination
Renal (proteolysis)
eGFR cutoff
Product-specific renal restrictions
Structural Pharmacology
Exenatide is a synthetic replicate of exendin-4. Its Gly² substitution prevents DPP-4 cleavage at the His-Gly bond. The XR formulation (Bydureon) encapsulates exenatide in poly(lactic-co-glycolic acid) (PLGA) microspheres — a biodegradable polymer matrix that releases the peptide over approximately 10 weeks as polymer hydrolysis progresses. This delivery system achieves once-weekly dosing purely through sustained subcutaneous release, not through modification of the peptide's pharmacokinetics. The microspheres produce a visible subcutaneous nodule at injection sites in some patients.
Clinical Profile
As a short-acting agent, exenatide IR primarily suppresses postprandial glucose through gastric emptying delay and meal-related insulin stimulation, with comparatively modest effects on fasting glucose. This differentiates it mechanistically from once-weekly agents: short-acting GLP-1 RAs produce greater meal-related GLP-1R agonism (relevant for postprandial hyperglycaemia) but less continuous receptor occupancy (less fasting glucose control). Exenatide IR must be administered within 60 minutes before the two main meals of the day — a prescribing detail with significant adherence implications.
Key Trial Evidence
DURATION-1
HbA1c −1.9% (XR vs IR)
XR superior to IR · 26 weeks
EXSCEL
MACE neutral (HR 0.91)
CV safety · n=14,752 · 2017
HbA1c reduction
−0.8 to −1.5%
Dose-dependent · vs baseline
Limitations & Current Use
Exenatide has been largely superseded by semaglutide and tirzepatide for new prescriptions in T2DM management, given inferior HbA1c reduction, weight loss, and CV outcome data. EXSCEL demonstrated CV safety (non-inferiority) but not superiority, unlike LEADER (liraglutide), SUSTAIN-6 (semaglutide), and SELECT (semaglutide). Current use is primarily in patients with established exenatide tolerance who are maintained on therapy, or where cost is the primary driver. Renal impairmentExenatide renal restrictions depend on formulation and jurisdiction. Use the current UK product information and monitor dehydration-related renal deterioration; a universal eGFR 45 cutoff must not be applied to both formulations.
Origin
Exendin-4 + C-terminal Lys×6
Dosing
10–20 mcg SC once daily
Special feature
Strongest gastric emptying delay
Structural Pharmacology
Lixisenatide is a modified exendin-4 analogue with six lysine residues appended to the C-terminus and deletion of Pro38. These modifications increase receptor binding affinity and confer additional DPP-4 resistance while extending the half-life modestly to ~3 hours. Among all GLP-1 RAs, lixisenatide produces the most pronounced gastric emptying delay, resulting in a disproportionately large postprandial glucose-lowering effect relative to its overall HbA1c reduction — making it uniquely suited to patients with isolated postprandial hyperglycaemia and predominantly normal fasting glucose.
CV Outcomes — ELIXA Trial
ELIXA (2015, n=6,068) was the first GLP-1 RA cardiovascular outcomes trial. It enrolled patients with T2DM following a recent acute coronary syndrome — a uniquely high-risk population. Lixisenatide demonstrated CV safety (non-inferiority for MACE) but did not demonstrate superiority (HR 1.02, 95% CI 0.89–1.17). Unlike subsequent trials, ELIXA showed no benefit in heart failure hospitalisation and no renal benefit. This trial positioned lixisenatide as the GLP-1 RA with the weakest CV outcomes evidence of the class — though it established the foundational safety dataset that encouraged subsequent trials.
ELIXA
MACE neutral (HR 1.02)
Post-ACS population · n=6,068
Postprandial BG
Largest PPG reduction
Greatest gastric delay of class
⚠
Generation I — Key Clinical Limitation
Short-acting exenatide and lixisenatide generally retain a more marked gastric-emptying effect than long-acting agents. Sustained GLP-1 receptor stimulation can cause tachyphylaxis. These mechanisms do not establish a universal preferred medicine; use current NICE pathways and the product-specific SmPC.once-weekly semaglutide is preferred by NICE NG28 (February 2026) based on superior HbA1c reduction, weight loss, and cardiovascular outcome data.
Generation II
Fatty Acid–Acylated Analogues
Once daily · ≥94% GLP-1 homology · Albumin-binding strategy
The second generation introduced the pivotal innovation of fatty acid acylation to achieve extended plasma half-life through non-covalent albumin binding. Rather than relying on non-human peptide sequences for DPP-4 resistance, these agents are near-identical to human GLP-1 but modified at strategic positions to resist degradation and bind plasma albumin, dramatically extending circulating half-life.
GLP-1 Homology
97% sequence identity
Key modification
C16 palmitoyl at Lys²⁶
Albumin binding
>98% (non-covalent)
T2DM dosing
0.6→1.2→1.8 mg SC OD
Obesity dosing
0.6→3.0 mg SC OD (titrate over 5 weeks)
Renal use
Caution eGFR <15; avoid ESRD
Structural Pharmacology
Liraglutide achieves a 97% homology to native GLP-1 with two modifications: (1) Lys³⁴→Arg substitution prevents trypsin cleavage; (2) a C16 palmitoyl fatty acid is attached via a glutamate spacer to Lys²⁶. The palmitoyl chain mediates reversible, non-covalent albumin binding, creating a large effective molecular complex (~70 kDa) that resists renal filtration and protects the peptide from proteolytic degradation. Self-association into heptameric complexes at the SC injection site provides an additional absorption depot, contributing to the ~13-hour half-life and allowing once-daily dosing without loss of glycaemic control during the 12–24-hour inter-dose interval.
LEADER Trial — Landmark CV Evidence
The LEADER trial (2016, NEJM, n=9,340) established liraglutide as the first GLP-1 RA to demonstrate cardiovascular superiority over placebo (standard of care). Primary MACE (CV death, non-fatal MI, non-fatal stroke) was reduced by 13% (HR 0.87, 95% CI 0.78–0.97, p=0.01 for superiority). CV death was specifically reduced by 22% (HR 0.78). All-cause mortality was reduced by 15%. The renal composite outcome was reduced by 22%. LEADER enrolled patients with T2DM at high CV risk (established CVD or ≥1 CV risk factor aged ≥50 years) over a median 3.8 years — and remains the foundational dataset supporting liraglutide's cardiovascular positioning in international guidelines.
Obesity Indication — Saxenda (3.0 mg)
At the higher obesity dose (Saxenda, 3.0 mg OD), liraglutide produces approximately 7–8% mean body weight loss (−8.4 kg absolute; net placebo-adjusted ~5.6%) in clinical trials (SCALE programme), with ~63% of patients achieving ≥5% weight loss at 56 weeks. The SCALE Outcomes trial (n=3,731) demonstrated modest CV risk factor improvement without a powered CV endpoint. Saxenda has been largely superseded in obesity management by semaglutide 2.4 mg (Wegovy) and tirzepatide (Zepbound), which produce 2–4× greater weight loss — though liraglutide remains a NICE-approved option in England under the NHS England Tier 3 specialist weight management service criteria.
LEADER
MACE −13% (HR 0.87)
CV superiority · n=9,340 · 2016
SCALE Obesity
Weight loss −8.4 kg
vs −2.8 kg placebo · 56 weeks
LIRA-RENAL
Safe eGFR 15–59
No dose adjustment needed
Generation III
Ultra-Long-Acting Once-Weekly Agents
Semaglutide · Dulaglutide · Efpeglenatide · Fatty diacid or Fc-fusion strategies
Generation III agents achieve once-weekly dosing through structural innovations that extend half-life to 5–7 days. Two distinct strategies are employed: enhanced fatty acid acylation (semaglutide: C18 fatty diacid with PEG spacer, achieving stronger albumin binding than liraglutide's C16 chain) and Fc-fusion protein technology (dulaglutide: IgG4 Fc domain linked to two GLP-1 peptides, leveraging FcRn recycling). This generation represents the current standard of care for GLP-1 RA therapy in type 2 diabetes and obesity.
GLP-1 Homology
94% sequence identity
Modification
Aib⁸ + C18 fatty diacid (mini-PEG)
SC half-life
~7 days (165–184 h)
Albumin binding
>99% · 3–4× stronger than liraglutide
Ozempic dosing
0.25→0.5→1→2 mg SC weekly
Wegovy dosing
0.25→2.4 mg SC weekly (5 steps); UK maximum up to 7.2 mg weekly for BMI ≥30 kg/m² (
MHRA, 6 January 2026)
Rybelsus
1.5→4→9 mg oral OD (fasting; current UK formulation, replaced 3/7/14 mg)
HbA1c reduction
Up to −1.8% (1 mg SC)
Semaglutide Structure and Pharmacology
Semaglutide differs structurally from liraglutide through: (1) Aib⁸ (α-aminoisobutyric acid) at position 8, which reduces DPP-4 cleavage; (2) a C18 fatty diacid attached through a spacer to Lys²⁶, supporting albumin binding; and (3) an Lys³⁴→Arg substitution. These features support high protein binding and once-weekly subcutaneous dosing. Comparative efficacy depends on indication, dose, comparator and population and should not be inferred from structural pharmacology alone.
Oral Semaglutide — Indication and Brand Matter
Rybelsus is oral semaglutide authorised for T2DM. A separate Wegovy tablet for weight management was authorised by the MHRA on 11 June 2026 at a different dose schedule (1.5→4→9→25 mg once daily) and is not currently available through the NHS. These products and doses must not be interchanged. Both use an absorption-enhancing oral formulation and require fasting administration; follow the current product information.
SELECT Trial — CV Outcomes Without Diabetes (2023)
The SELECT trial (NEJM 2023, Lincoff et al., n=17,604) was transformative: it enrolled adults with obesity (BMI ≥27) and established cardiovascular disease but without diabetes — demonstrating for the first time that a GLP-1 RA reduces MACE in a non-diabetic population. Semaglutide 2.4 mg SC weekly reduced the primary composite (CV death, non-fatal MI, non-fatal stroke) by 20% (HR 0.80, 95% CI 0.72–0.90, p<0.001) over a mean 39.8 months. This was accompanied by 9.4% weight loss vs 0.9% placebo. SELECT positioned semaglutide as a cardioprotective agent beyond glycaemic control, and its data underpins MHRA and NICE expansion of the obesity indication in 2024–2025.
FLOW Trial — Renal Outcomes (2024)
FLOW randomised 3,533 adults with type 2 diabetes and selected albuminuric CKD. Its composite included kidney failure, sustained ≥50% eGFR decline, or death from kidney or cardiovascular causes (HR 0.76; 95% CI 0.66–0.88); this is not a kidney-only composite. Median follow-up was 3.4 years. Baseline-SGLT2 subgroup estimates were imprecise and do not independently prove additive kidney protection.
Primary source.
MASH — product-specific authorisations
ESSENCE reported MASH resolution without fibrosis worsening in 62.9% versus 34.3% with placebo at the planned 72-week analysis. Semaglutide is distinct from tirzepatide: FDA approved Wegovy for non-cirrhotic MASH with F2–F3 fibrosis in August 2025. Current UK Wegovy product information also contains an adult non-cirrhotic MASH indication; follow its dose and specialist requirements.
Primary source.
Oral Wegovy — US December 2025; UK June 2026
FDA approval of Wegovy tablets was announced on 22 December 2025; January 2026 was the US launch period. The MHRA authorised the weight-management tablet on 11 June 2026. Oral Wegovy and Rybelsus have distinct indications and dose schedules and must not be substituted dose-for-dose.
Primary source.
SUSTAIN-6
MACE −26% (HR 0.74)
T2DM + high CV risk · n=3,297
SELECT 2023
MACE −20% (HR 0.80)
Obesity, no T2DM · n=17,604
FLOW 2024
Renal composite −24%
CKD + T2DM · n=3,533
STEP-1
Weight −14.9%
Semaglutide 2.4 mg · n=1,961
Structure
2× GLP-1 analogue + IgG4 Fc fusion
Half-life
~5 days (112 hours)
Recycling mechanism
FcRn neonatal Fc receptor
Dosing
0.75→1.5→3→4.5 mg SC weekly
Max approved dose
4.5 mg (2020 extension)
Device
Single-use auto-injector pen
Immunogenicity
Very low (Fc modifications)
Fc-Fusion Half-Life Strategy
Dulaglutide uses a fundamentally different half-life extension strategy from albumin-binding agents. Two modified GLP-1(7-37) molecules are covalently linked via a short peptide connector to the Fc region of IgG4. The IgG4 Fc domain is modified (Leu²³⁴Ala, Leu²³⁵Ala) to eliminate Fc-gamma receptor binding and complement activation, minimising effector function and reducing immunogenicity. The large molecular size (~60 kDa) prevents glomerular filtration. Critically, neonatal Fc receptor (FcRn) recycling — the endosomal salvage mechanism that rescues IgG antibodies from lysosomal degradation — extends dulaglutide's half-life to ~5 days, far beyond what molecular size alone would predict.
REWIND — Broad CV Outcomes in Diverse T2DM Population
REWIND (2019, NEJM, n=9,901) demonstrated cardiovascular superiority of dulaglutide 1.5 mg weekly vs placebo (HR 0.88, 95% CI 0.79–0.99, p=0.026) in the most demographically broad GLP-1 RA outcomes trial — only 31% of participants had established CVD at baseline, making REWIND the most relevant to primary prevention. The primary MACE reduction of 12% was driven primarily by non-fatal stroke reduction (HR 0.76) — a finding that distinguishes REWIND from other GLP-1 RA trials. Dulaglutide also showed a renal composite benefit (HR 0.85), though less pronounced than semaglutide in FLOW.
REWIND
MACE −12% (HR 0.88)
69% primary prevention · n=9,901
AWARD-11
HbA1c −2.02% (4.5 mg)
Dose escalation trial · 2020
⛔
Albiglutide (Tanzeum / Eperzan) — Commercially Withdrawn 2018
Albiglutide (GSK) was a once-weekly GLP-1 RA utilising a different Fc-fusion strategy — GLP-1 fused to human albumin (not IgG4). Despite receiving FDA (2014) and EMA approval and demonstrating CV safety in HARMONY Outcomes (HR 0.78, p=0.0006 for superiority), GSK withdrew albiglutide from all markets in July 2018 for commercial reasons (poor market penetration vs Trulicity), not safety concerns. It is clinically notable that HARMONY Outcomes demonstrated CV superiority post-withdrawal, raising questions about the commercial decision. Albiglutide serves as a pharmacological reference point for albumin-fusion (as opposed to albumin-binding) half-life extension.
Structure
Exendin-4 + PEG + IgG4 Fc
Half-life
~10 days (longest peptide t½)
Dosing
4–6 mg SC once weekly
Status
Phase 3 complete · NDA not yet filed US
Efpeglenatide combines elements of both half-life extension strategies: exendin-4 (DPP-4-resistant peptide) conjugated to a PEGylated IgG4 Fc domain. The ~10-day half-life is the longest of any peptide GLP-1 RA. The AMPLITUDE-O trial (NEJM 2021, n=4,076) demonstrated MACE superiority (HR 0.73, p=0.0004) in a high-CV-risk T2DM population, establishing its outcomes credentials. However, Sanofi has not pursued regulatory filing in the US or EU, citing commercial strategy — making efpeglenatide a clinical orphan with strong evidence but no approved product.
Generation IV
Dual GIP/GLP-1 Co-Agonists
Tirzepatide — dual incretin pharmacology · comparative trial evidence
Generation IV represents the most significant pharmacological advance since the introduction of GLP-1 RAs — the first agent designed as a single-molecule dual incretin co-agonist acting at both the GIP receptor and GLP-1 receptor simultaneously. This is mechanistically distinct from simply combining two separate agonists: tirzepatide is a single peptide optimised to activate both receptors with specific potency ratios and biased signalling characteristics that produce synergistic rather than additive effects.
Receptor targets
GIPR (full) + GLP-1R (partial)
GIP EC₅₀
~0.05 nM (full agonist)
GLP-1R activity
Biased · lower potency vs semaglutide
Half-life
~5 days (C20 fatty diacid)
T2DM dosing
2.5→5→10→15 mg SC weekly
HbA1c reduction
Up to −2.58% (15 mg)
Weight loss
Up to −22.5% (SURMOUNT-1, 15 mg)
NICE approval
NG28 Feb 2026 — T2DM criteria
Structural Innovation — Twin Incretin in a Single Peptide
Tirzepatide is a 39-amino-acid synthetic peptide based on the native GIP sequence with modifications that enable simultaneous high-affinity GIP receptor and GLP-1 receptor binding. Key structural features: (1) The GIP-based scaffold preserves high-affinity GIPR binding; (2) Amino acid substitutions at critical positions enable GLP-1R recognition — notably Aib² for DPP-4 resistance; (3) A C20 fatty diacid via γGlu-mini-PEG linker at Lys²⁶ achieves albumin binding sufficient for a ~5-day half-life. Unlike semaglutide (which is a biased Gs activator with strong β-arrestin recruitment), tirzepatide shows biased GLP-1R agonism favouring the Gs pathway over β-arrestin — potentially explaining its sustained weight loss efficacy without the receptor desensitisation seen with long-term full agonists.
SURPASS Programme — T2DM
SURPASS-2 reported HbA1c changes of −2.01, −2.24 and −2.30 percentage points with tirzepatide 5, 10 and 15 mg versus −1.86 with semaglutide 1 mg at 40 weeks. SURPASS-CVOT subsequently met non-inferiority to dulaglutide for MACE (HR 0.92; 95.3% CI 0.83–1.01); superiority was not demonstrated (p=0.09).
Primary source.
SURMOUNT Programme — Obesity
SURMOUNT-1 reported 72-week weight changes of −15.0%, −19.5% and −20.9% with tirzepatide 5, 10 and 15 mg versus −3.1% with placebo (treatment-regimen estimand). The separate efficacy estimand at 15 mg was −22.5% versus −2.4%. SURMOUNT-3 used a selected lifestyle lead-in population and reported additional change of −18.4% versus +2.5% after randomisation; do not mix those baselines.
Primary source.
MASH / MASLD — phase 2 evidence
SYNERGY-NASH (NEJM 2024) was a phase 2 trial, not an approval decision. MASH resolution without fibrosis worsening occurred in 44%, 56% and 62% with 5, 10 and 15 mg tirzepatide versus 10% with placebo at 52 weeks. The previous claim of FDA MASH approval in early 2026 was unsupported and has been removed. Do not prescribe for MASH solely on this research summary.
Primary source.
Obstructive sleep apnoea — US approval, December 2024
The FDA authorised Zepbound for moderate-to-severe obstructive sleep apnoea in adults with obesity on 20 December 2024, alongside reduced-calorie diet and physical activity. This is a United States product indication; UK indications and NHS access must be checked separately.
Primary source.
SURPASS-2
HbA1c −2.30% (15 mg)
Superior to sema 1mg · n=1,879
SURMOUNT-1
Weight −20.9% (15 mg)
No T2DM · n=2,539 · 72 weeks
SYNERGY-NASH
MASH resolution 44–62%
NEJM 2024 · vs 10% placebo
SURMOUNT-3
Additional weight −18.4%
After lifestyle lead-in · treatment-regimen
Combination Class
Fixed-Ratio Insulin Combinations
IDegLira · IGlarLixi · Co-formulated basal insulin + GLP-1 RA
Fixed-ratio combination products co-formulate a basal insulin with a GLP-1 RA in a single pen device, administered as a single daily injection. They are designed to provide complementary glycaemic mechanisms — basal insulin addresses fasting hyperglycaemia while the GLP-1 RA reduces postprandial excursions and attenuates insulin-related weight gain — with simplified injection burden compared with separate titration of each agent.
Components
Degludec + Liraglutide
Ratio
1 unit degludec : 0.036 mg liraglutide
Dose range
10–50 dose steps OD
Max liraglutide
1.8 mg/day (at max dose)
IDegLira delivers both components at a fixed 1:0.036 ratio, allowing simple titration by dose steps. The DUAL programme demonstrated HbA1c reduction of ~1.9% from baseline in insulin-naive patients, with weight-neutral to weight-losing outcomes (unlike basal insulin alone). The GLP-1 RA component attenuates the hypoglycaemia-promoting effects of intensifying insulin and prevents the weight gain typically seen with insulin titration — addressing two major barriers to insulin intensification. Key limitation: the fixed ratio means the GLP-1 RA dose cannot be independently titrated, potentially limiting dose flexibility.
DUAL-I
HbA1c −1.9%
Insulin-naive · 26 weeks
DUAL-VII
Weight neutral vs IDeg alone
Insulin intensification
Components
Glargine U100 + Lixisenatide
Pen A (10–40 U)
Glargine 1U : Lixisenatide 1mcg
Pen B (30–60 U)
Glargine 1U : Lixisenatide 0.5mcg
Timing
SC OD within 1 hour before meal
IGlarLixi differs from IDegLira in utilising lixisenatide — the short-acting exendin-4 analogue with the most pronounced gastric emptying delay. The LixiLan programme demonstrated superiority to glargine alone (HbA1c −1.6% vs −1.3%) with significantly less weight gain. Two pen strengths allow flexibility across the insulin dose range. Key advantage over IDegLira: lixisenatide's strong postprandial action specifically addresses mealtime hyperglycaemia, complementing glargine's fasting glucose control in a pharmacokinetically rational pairing.
LixiLan-O
HbA1c −1.6% vs −1.3% glargine
Insulin-naive · 30 weeks
Oral Class
Oral GLP-1 Receptor Agonists
Peptide-based (SNAC) and non-peptide small-molecule approaches
The oral delivery of GLP-1 RAs represents the most commercially significant challenge in incretin pharmacology. Two distinct approaches have now reached regulatory approval: oral peptide delivery (semaglutide enabled by SNAC absorption technology, licensed 2019) and oral non-peptide small-molecule GLP-1 RAs (orforglipron/Foundayo FDA approved April 2026 for chronic weight management; UK authorised August 2026 for weight management and type 2 diabetes, danuglipron development discontinued April 2025). Small-molecule agents do not require absorption enhancers, have no food interaction constraints, are manufacturable without recombinant biology, and could transform access economics in low-income settings. Orforglipron's approval marks a watershed moment — the first small-molecule GLP-1 RA, enabling true generic development rather than biosimilars.
💡
Why Small-Molecule GLP-1 RAs Are a Paradigm Shift
Oral small-molecule agonists activate GLP-1 receptors without the peptide structure of semaglutide. Binding modes and pharmacological properties differ by compound; do not generalise an allosteric mechanism or food restrictions across this class. Orforglipron is the authorised example described below.
Brand name
Foundayo (UK/US)
Structure
Small molecule · Non-peptide
Mechanism
TM allosteric GLP-1R agonist
Dosing
Oral once daily · No food/water restriction
UK authorisation
10 August 2026
Indication
UK: weight management and type 2 diabetes
Prescribing
Use current UK SmPC; check NHS eligibility
Key innovation
First GLP-1 pill with no timing restrictions
Orforglipron (Foundayo) is an oral, non-peptide GLP-1 receptor agonist. The MHRA authorised it on 10 August 2026 for adult weight management and insufficiently controlled type 2 diabetes. The weight-management indication covers BMI ≥30 kg/m², or ≥27 to <30 kg/m² with a weight-related comorbidity, alongside diet and activity. Authorisation does not itself establish NICE recommendation, NHS funding or availability.
MHRA authorisation.
Structure
Non-peptide small molecule
Phase 2b
−7.7% weight (40 mg BID)
GI tolerability
Higher vs orforglipron Phase 2
Current status
Development discontinued 14 April 2025
Pfizer discontinued danuglipron development on 14 April 2025 after reviewing the clinical programme, including a potential drug-induced liver injury in one participant. This includes the once-daily programme; danuglipron is not an active phase 3 option.
Pfizer development update.
Lotiglipron (Pfizer) was discontinued in June 2023 after Phase 2 data revealed clinically significant hepatotoxicity signals — elevated liver enzymes (ALT/AST) in a substantial proportion of participants. This led to complete programme termination. The compound's hepatic safety profile contrasts with orforglipron, which has not demonstrated comparable liver signals in Phase 2 data, suggesting this may be a compound-specific rather than class-wide concern. Lotiglipron's discontinuation heightened regulatory scrutiny of hepatic monitoring requirements across the oral non-peptide class.
The former claim of a named Novo Nordisk six-month semaglutide implant programme could not be substantiated in the current sponsor pipeline and has been removed. Long-acting delivery concepts must not be described as clinical-stage products without a traceable trial registration or primary report. Sponsor pipeline checked 21 October 2026.
Generation V
Triple Agonists — GIP + GLP-1 + Glucagon
Retatrutide (triple) · Mazdutide (dual) · Glucagon-containing therapies
The third receptor target — the glucagon receptor (GCGR) — adds a fundamentally new mechanism to the dual incretin framework. Glucagon stimulates hepatic gluconeogenesis (raising glucose) but simultaneously increases energy expenditure through brown adipose tissue thermogenesis, hepatic fatty acid oxidation, and lipolysis. In isolation, glucagon receptor agonism causes hyperglycaemia — making it pharmacologically incompatible with metabolic disease treatment. But combined with GLP-1R agonism (which powerfully suppresses glucose elevation and insulin-independent glucose disposal), the hyperglycaemic effect of glucagon is neutralised while its energy-expenditure-promoting effects are retained — a pharmacologically elegant co-dependency.
Targets
GIPR + GLP-1R + GCGR
TRIUMPH-2: 12 mg
−18.8% at 80 weeks (treatment-regimen)
HbA1c reduction
See trial-specific glycaemic outcomes
Half-life
~6 days · weekly dosing
Dosing (Phase 3)
4, 9, 12 mg SC weekly (study doses)
Regulatory status
Investigational; not authorised for prescribing
Retatrutide activates GIP, GLP-1 and glucagon receptors.
TRIUMPH-2 now provides phase 3 evidence in obesity and type 2 diabetes. The sponsor’s 20.8% result uses the efficacy estimand; it is distinct from the treatment-regimen result above. Cross-trial comparisons do not establish superiority over tirzepatide or surgery.
Peer-reviewed trial;
sponsor analysis (29 September 2026).
Targets
GLP-1R + GCGR (no GIP)
Weight loss
−15.2% at 24 weeks (6 mg)
Region
China-based trials · Pan-Asia
Status
China: authorised; UK status differs
Mazdutide is a GLP-1/glucagon dual agonist, not a triple agonist. NMPA authorisation in China covers adult weight management and type 2 diabetes; this does not confer UK authorisation.
Innovent regulatory status (June 2026).
Pemvidutide is an investigational GLP-1/glucagon dual agonist. The sponsor reported 48-week IMPACT phase 2b MASH data in December 2025; it is inaccurate to describe those results as still pending. Body-composition analyses from separate studies do not prove preservation of muscle function or superiority over semaglutide or tirzepatide. Lean mass and skeletal-muscle function are different measurements. Dated sponsor IMPACT report.
Emerging Class
Novel Mechanisms & Combination Strategies
GLP-1/amylin · GLP-1/FGF21 · GLP-1/GIP/Amylin · Brain-biased agonism · 2025–2030 horizon
REDEFINE-1 (NEJM 2025) randomised 3,417 adults without diabetes to cagrilintide–semaglutide, either component, or placebo for 68 weeks. Weight change with the combination was −20.4% versus −3.0% with placebo (treatment-policy estimand). The 22.7% headline uses the trial-product estimand and must not be paired with the treatment-policy placebo result. Gastrointestinal events occurred in 79.6% versus 39.9%. This trial does not establish superiority over tirzepatide. Primary publication. Novo Nordisk lists CagriSema for obesity as filed; filing is not authorisation. Sponsor pipeline.
Submitted (FDA): the sponsor announced its new drug application in December 2025. Dated submission announcement. A submission is not approval.
Zenagamtide (formerly amycretin) is a single-molecule GLP-1/amylin receptor agonist with oral and subcutaneous formulations. The sponsor’s Q2 2026 update states that the phase 3 AMAZE obesity programme began in Q1 2026 and describes planned AMBITION phase 3 development in type 2 diabetes. It remains investigational. Early dose-escalation results cannot establish a product ranking or predict final phase 3 outcomes. Dated sponsor development update.
Survodutide is an investigational GLP-1/glucagon dual agonist. In the 48-week phase 2 MASH trial (293 treated participants), MASH improvement without worsening fibrosis occurred in 47%, 62% and 43% with 2.4, 4.8 and 6 mg versus 14% with placebo. At least one-stage fibrosis improvement occurred in 34–36% versus 22%; this was not an 83% fibrosis response. Nausea, diarrhoea and vomiting were common. Primary publication. Phase 3 SYNCHRONIZE-1 obesity and SYNCHRONIZE-MASLD results were published in 2026; these are distinct populations and endpoints. SYNCHRONIZE-1. SYNCHRONIZE-MASLD.
FGF21 effects
Adiponectin ↑ · Hepatic lipid ↓ · TG ↓
Rationale
Complementary metabolic + liver effects
Key programmes
Novo (sema-FGF21 bispecific) · 89bio
Target conditions
MASH · T2DM · Obesity · ASCVD
Fibroblast growth factor 21 (FGF21) is a hepatokine that increases adiponectin secretion, promotes fatty acid oxidation, reduces triglycerides, and improves insulin sensitivity through mechanisms distinct from GLP-1R signalling. GLP-1R/FGF21 bispecific conjugates or co-formulated therapies aim to combine GLP-1-mediated appetite suppression and insulin secretion with FGF21's lipid-lowering, liver-protective, and adiponectin-enhancing effects. Novo Nordisk disclosed a semaglutide-FGF21 bispecific programme in 2024. 89bio's pegozafermin (FGF21 analogue) is separately in Phase 3 for MASH, and combination strategies with GLP-1 RAs are anticipated. This class is particularly compelling for the MASH + dyslipidaemia + obesity triad.
Concept
Tissue-biased GLP-1R agonism
CNS-biased goal
Greater appetite suppression · Less GI SE
Peripheral-restricted
GI SE reduction · Insulin action focus
Programmes
Multiple academic + industry · 2026–2030
The primary adverse effects of current GLP-1 RAs — nausea, vomiting, constipation — arise predominantly from GLP-1R activation in the gut and brainstem area postrema. Peripherally-restricted GLP-1 RAs (poor CNS penetration) could potentially reduce GI side effects while preserving pancreatic and peripheral metabolic effects. Conversely, CNS-penetrant / brain-biased variants aim to maximise hypothalamic appetite suppression while minimising peripheral GI activation. Additionally, β-arrestin-biased GLP-1 RAs that preferentially engage Gs over β-arrestin at GLP-1R are being developed to reduce receptor desensitisation during chronic therapy — potentially maintaining efficacy beyond the ~18-month plateau observed with current agents. These represent the frontier of precision pharmacology for incretin therapy.
Horizon
The Future Landscape — 2026–2030
Projected approvals · Combination pharmacology · Delivery innovation · Biosimilars
The GLP-1 RA therapeutic landscape is undergoing the most rapid period of pharmacological innovation since insulin's introduction. By 2030, the therapeutic class is expected to encompass agents addressing mechanisms far beyond glycaemia and weight, with implications for heart failure, neurodegenerative disease, addiction, and — through biosimilar entry — global access transformation.
Projected Approvals Timeline (2025–2030)
| Agent | Class | Company | Indication | Expected | Status |
| Orforglipron |
Oral non-peptide GLP-1 RA |
Eli Lilly |
T2DM + Obesity |
10 August 2026 |
UK authorised |
| CagriSema |
GLP-1 + Amylin |
Novo Nordisk |
Obesity |
No approval date established |
Filed; investigational |
| Retatrutide |
Triple GIP/GLP-1/GCG |
Eli Lilly |
Obesity + T2DM |
2026 results; investigational |
Investigational |
| Tirzepatide (obesity) |
Dual GIP/GLP-1 |
Eli Lilly |
Weight management (Mounjaro UK) |
Authorised 2023 |
UK authorised |
| Zenagamtide (amycretin) |
GLP-1 + amylin |
Novo Nordisk |
Obesity / T2DM |
Phase 3 development in 2026 |
Investigational |
| GLP-1/FGF21 bispecific |
GLP-1 + FGF21 |
Novo Nordisk / others |
MASH + Obesity |
2028+ |
Phase 1–2 |
| Semaglutide biosimilar |
Biosimilar GLP-1 RA |
Multiple (Mylan, Sun, Biocon) |
T2DM / Obesity |
2028–2030 |
Development |
Expanding Indications Beyond Cardiometabolic Disease
The GLP-1 receptor is expressed broadly across tissues with implications beyond metabolic disease. Several expanding indications are supported by emerging evidence:
🔭
Heart Failure — STEP-HFpEF
STEP-HFpEF (NEJM 2023, n=529) demonstrated semaglutide 2.4 mg significantly improved KCCQ-CSS scores (quality of life), 6-minute walk distance, and CRP (inflammation marker) in patients with HFpEF and obesity, without worsening renal function. A dedicated HFpEF outcomes trial is now enrolling. GLP-1 RA therapy in HFpEF may act through multiple mechanisms: weight loss (reducing ventricular preload), anti-inflammatory effects, and direct myocardial GLP-1R signalling improving diastolic function.
🧠
Neurodegeneration — Parkinson's & Alzheimer's Disease
GLP-1R is expressed in substantia nigra dopaminergic neurons and hippocampal regions. Epidemiological data show reduced Parkinson's disease incidence in GLP-1 RA-treated T2DM patients. LIXIPARK (lixisenatide, phase 2) reported an exploratory motor-score signal, but the 2025 phase 3 exenatide trial did not demonstrate disease modification.
Exenatide primary report. Parkinson’s disease is not an established GLP-1 treatment indication. EVOKE/EVOKE+ did not slow Alzheimer’s disease progression; observational associations do not establish treatment efficacy.
Sponsor results, 24 November 2025.
🍺
Addiction & Reward Behaviour
GLP-1R is expressed in the ventral tegmental area (VTA) and nucleus accumbens — mesolimbic reward circuitry. Preclinical models show GLP-1 RA suppression of alcohol preference, nicotine seeking, and opioid reward. Phase 2 trials of semaglutide in alcohol use disorder (NCT05520398, n=48) and nicotine dependence are ongoing, with early signals of reduced consumption. The observation that GLP-1 RA users report reduced craving for alcohol, tobacco, and recreational drugs — noted in real-world pharmacovigilance — has generated substantial academic and commercial interest in addiction medicine applications.
💊
Biosimilar Entry — The Access Transformation
WHO added GLP-1 therapies to its Essential Medicines List in September 2025 for high-risk type 2 diabetes and issued conditional adult-obesity recommendations in December 2025. Generic timelines and percentage price reductions are not established by those decisions.
WHO guideline and EML context.
Reference
Full Comparison Table
All licensed and late-stage agents — side by side
| Drug |
Class |
Route |
Frequency |
t½ |
HbA1c↓ |
Weight↓ |
CV Trial |
UK Status |
| Exenatide IR |
Exendin-4 |
SC |
Twice daily |
2.4 h |
0.8–1.5% |
~2–3 kg |
EXSCEL (neutral) |
No longer UK marketed |
| Exenatide XR |
Exendin-4 + PLGA |
SC |
Weekly |
~2 wks |
1.3–1.9% |
~3 kg |
EXSCEL (neutral) |
No longer UK marketed |
| Lixisenatide |
Exendin-4 modified |
SC |
Once daily |
3 h |
0.8–1.0% |
~2 kg |
ELIXA (neutral) |
No longer UK authorised |
| Liraglutide |
Human GLP-1 + C16 |
SC |
Once daily |
13 h |
1.0–1.6% |
~5–6 kg |
LEADER ✓ (−13%) |
Licensed |
| Dulaglutide |
GLP-1 × IgG4 Fc |
SC |
Weekly |
5 d |
1.1–2.0% |
~4–6 kg |
REWIND ✓ (−12%) |
Licensed |
| Semaglutide SC |
Human GLP-1 + C18 |
SC |
Weekly |
7 d |
1.5–1.8% |
10–15% |
SELECT ✓ (−20%) |
Licensed ★ |
| Semaglutide oral |
Human GLP-1 + SNAC |
Oral |
Once daily |
7 d |
0.9–1.4% |
~5 kg |
SOUL: MACE HR 0.86 vs placebo |
Licensed |
| Tirzepatide |
GIP + GLP-1 dual |
SC |
Weekly |
5 d |
2.0–2.6% |
15–22% |
SURPASS-CVOT |
Licensed (T2DM + Obesity) |
| CagriSema |
GLP-1 + Amylin |
SC |
Weekly |
7 d |
TBC |
20.4% (REDEFINE-1; treatment-policy) |
No completed CVOT |
Filed; investigational |
| Retatrutide |
GIP + GLP-1 + GCG |
SC |
Weekly |
6 d |
Trial-dependent |
18.8% (TRIUMPH-2; treatment-regimen) |
TRIUMPH-2 (2026) |
Investigational |
| Orforglipron |
Non-peptide oral GLP-1 RA |
Oral |
Once daily |
~12 h |
Trial-dependent |
Trial-dependent |
ATTAIN (Phase 3) |
UK authorised |
| Zenagamtide (amycretin) |
GLP-1 + Amylin (single mol.) |
Oral / SC |
Weekly |
TBC |
TBC |
~22%+ |
No completed CVOT |
Investigational · phase 3 |
| Albiglutide |
GLP-1 × HSA fusion |
SC |
Weekly |
5 d |
0.7–1.0% |
~1 kg |
HARMONY ✓ (−22%) |
Withdrawn 2018 |
![Oral semaglutide — SNAC absorption enhancer. Illustration showing Sodium N-(8-[2-hydroxybenzoyl] amino) caprylate facilitates gastric transcellular absorption.](/images/drug-classes/img_oral_sema_snac.webp)
