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'''GLP-1 receptor agonists''' (GLP-1 RAs, also called ''incretin mimetics'') are a class of injectable and (in one case) oral peptide medicines that bind and activate the [[GLP-1 receptor]].<ref name="drucker2022">Drucker DJ (2022). GLP-1 physiology informs the pharmacotherapy of obesity. ''Mol Metab'' 57:101351. doi:10.1016/j.molmet.2021.101351</ref> They were originally developed for [[type 2 diabetes mellitus]] and have since become first-line for [[obesity]],<ref name="step1">Wilding JPH et al. (2021). Once-weekly semaglutide in adults with overweight or obesity (STEP-1). ''NEJM'' 384:989. doi:10.1056/NEJMoa2032183</ref><ref name="surmount1">Jastreboff AM et al. (2022). Tirzepatide once weekly for the treatment of obesity (SURMOUNT-1). ''NEJM'' 387:205. doi:10.1056/NEJMoa2206038</ref> approved for [[cardiovascular risk reduction]] in obesity without diabetes,<ref name="select">Lincoff AM et al. (2023). Semaglutide and cardiovascular outcomes in obesity without diabetes (SELECT). ''NEJM'' 389:2221–32. doi:10.1056/NEJMoa2307563</ref> [[chronic kidney disease]] in T2DM,<ref name="flow">Perkovic V et al. (2024). Effects of semaglutide on chronic kidney disease in patients with type 2 diabetes (FLOW). ''NEJM'' 391:109. doi:10.1056/NEJMoa2403347</ref> and [[MASH]] with stage 2–3 fibrosis.<ref name="essence">Newsome PN et al. (2025). Semaglutide in MASH (ESSENCE). FDA approval basis. {{Citation needed}}</ref>
'''GLP-1 receptor agonists''' (GLP-1 RAs, also called ''incretin mimetics'') are a class of injectable and (in one case) oral peptide medicines that bind and activate the [[GLP-1 receptor]].<ref name="drucker2022">Drucker DJ (2022). GLP-1 physiology informs the pharmacotherapy of obesity. ''Mol Metab'' 57:101351. doi:10.1016/j.molmet.2021.101351</ref> They were originally developed for [[type 2 diabetes mellitus]] and have since become first-line for [[obesity]],<ref name="step1">Wilding JPH et al. (2021). Once-weekly semaglutide in adults with overweight or obesity (STEP-1). ''NEJM'' 384:989. doi:10.1056/NEJMoa2032183</ref><ref name="surmount1">Jastreboff AM et al. (2022). Tirzepatide once weekly for the treatment of obesity (SURMOUNT-1). ''NEJM'' 387:205. doi:10.1056/NEJMoa2206038</ref> approved for [[cardiovascular risk reduction]] in obesity without diabetes,<ref name="select">Lincoff AM et al. (2023). Semaglutide and cardiovascular outcomes in obesity without diabetes (SELECT). ''NEJM'' 389:2221–32. doi:10.1056/NEJMoa2307563</ref> [[chronic kidney disease]] in T2DM,<ref name="flow">Perkovic V et al. (2024). Effects of semaglutide on chronic kidney disease in patients with type 2 diabetes (FLOW). ''NEJM'' 391:109. doi:10.1056/NEJMoa2403347</ref> and [[MASH]] with stage 2–3 fibrosis.<ref name="essence">Newsome PN et al. (2025). Semaglutide in MASH (ESSENCE). FDA approval basis. {{Citation needed}}</ref>


As of 2023, GLP-1 RAs were the largest growth driver in US outpatient medicine spending — Ozempic alone accounted for $9.2 billion in Medicare Part D, second only to [[Eliquis]] across all federal programs.<ref name="cms2023">Centers for Medicare & Medicaid Services. ''Medicare Part D Drug Spending Dashboard, 2023.'' Gross spending, not net of manufacturer rebates. Available at: https://data.cms.gov/summary-statistics-on-use-and-payments/medicare-medicaid-spending-by-drug</ref>
As of 2023, GLP-1 RAs were the largest growth driver in US outpatient medicine spending, Ozempic alone accounted for $9.2 billion in Medicare Part D, second only to [[Eliquis]] across all federal programs.<ref name="cms2023">Centers for Medicare & Medicaid Services. ''Medicare Part D Drug Spending Dashboard, 2023.'' Gross spending, not net of manufacturer rebates. Available at: https://data.cms.gov/summary-statistics-on-use-and-payments/medicare-medicaid-spending-by-drug</ref>


== Mechanism ==
== Mechanism ==
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The GLP-1 receptor is a class B G-protein-coupled receptor expressed on pancreatic β-cells, hypothalamic satiety neurons, gastric smooth muscle, cardiomyocytes, vascular endothelium, and renal tubules.<ref name="drucker2022"/><ref name="holst2022">Holst JJ (2022). GLP-1 incretin and pleiotropic hormone with pharmacological promise. ''Curr Opin Pharmacol'' 63:102189.</ref> Activation produces:
The GLP-1 receptor is a class B G-protein-coupled receptor expressed on pancreatic β-cells, hypothalamic satiety neurons, gastric smooth muscle, cardiomyocytes, vascular endothelium, and renal tubules.<ref name="drucker2022"/><ref name="holst2022">Holst JJ (2022). GLP-1 incretin and pleiotropic hormone with pharmacological promise. ''Curr Opin Pharmacol'' 63:102189.</ref> Activation produces:


* '''β-cell''': glucose-dependent insulin secretion — meaning hypoglycemia risk is low compared to [[sulfonylureas]] or [[insulin]]<ref name="drucker2022"/>
* '''β-cell''': glucose-dependent insulin secretion, meaning hypoglycemia risk is low compared to [[sulfonylureas]] or [[insulin]]<ref name="drucker2022"/>
* '''α-cell''': glucagon suppression<ref name="drucker2022"/>
* '''α-cell''': glucagon suppression<ref name="drucker2022"/>
* '''Stomach''': delayed gastric emptying → improved postprandial glucose and prolonged satiety<ref name="drucker2022"/>
* '''Stomach''': delayed gastric emptying → improved postprandial glucose and prolonged satiety<ref name="drucker2022"/>
* '''CNS''': hypothalamic appetite suppression and modulation of reward circuitry — the mechanism behind both the weight loss and the widely-reported "food noise" quieting{{Citation needed}}
* '''CNS''': hypothalamic appetite suppression and modulation of reward circuitry, the mechanism behind both the weight loss and the widely-reported "food noise" quieting{{Citation needed}}
* '''Cardiovascular and renal''': independent of glycemia — endothelial improvement, natriuresis, weight-mediated and weight-independent blood pressure reduction, plaque stabilization<ref name="sattar2021">Sattar N et al. (2021). Cardiovascular, mortality, and kidney outcomes with GLP-1 receptor agonists in patients with type 2 diabetes: a systematic review and meta-analysis. ''Lancet Diabetes Endocrinol'' 9(10):653–62. doi:10.1016/S2213-8587(21)00203-5</ref>
* '''Cardiovascular and renal''': independent of glycemia, endothelial improvement, natriuresis, weight-mediated and weight-independent blood pressure reduction, plaque stabilization<ref name="sattar2021">Sattar N et al. (2021). Cardiovascular, mortality, and kidney outcomes with GLP-1 receptor agonists in patients with type 2 diabetes: a systematic review and meta-analysis. ''Lancet Diabetes Endocrinol'' 9(10):653–62. doi:10.1016/S2213-8587(21)00203-5</ref>


Native GLP-1 is rapidly cleaved by [[DPP-4]] and has a plasma half-life of approximately 2 minutes.<ref name="holst2022"/> Every clinically useful GLP-1 RA is engineered for DPP-4 resistance, either by amino-acid substitution at position 2 ([[liraglutide]], [[semaglutide]]),<ref name="drucker2022"/> structural fusion ([[dulaglutide]]'s Fc domain),<ref name="dulaglutide-label">US FDA. ''Trulicity (dulaglutide) prescribing information.'' Eli Lilly and Company. https://www.accessdata.fda.gov/drugsatfda_docs/label/2022/125469s044lbl.pdf</ref> or by being a non-mammalian peptide ([[exenatide]], from Gila monster venom).<ref name="eng1992">Eng J et al. (1992). Isolation and characterization of exendin-4, an exendin-3 analogue, from ''Heloderma suspectum'' venom. ''J Biol Chem'' 267(11):7402–5.</ref>
Native GLP-1 is rapidly cleaved by [[DPP-4]] and has a plasma half-life of approximately 2 minutes.<ref name="holst2022"/> Every clinically useful GLP-1 RA is engineered for DPP-4 resistance, either by amino-acid substitution at position 2 ([[liraglutide]], [[semaglutide]]),<ref name="drucker2022"/> structural fusion ([[dulaglutide]]'s Fc domain),<ref name="dulaglutide-label">US FDA. ''Trulicity (dulaglutide) prescribing information.'' Eli Lilly and Company. https://www.accessdata.fda.gov/drugsatfda_docs/label/2022/125469s044lbl.pdf</ref> or by being a non-mammalian peptide ([[exenatide]], from Gila monster venom).<ref name="eng1992">Eng J et al. (1992). Isolation and characterization of exendin-4, an exendin-3 analogue, from ''Heloderma suspectum'' venom. ''J Biol Chem'' 267(11):7402–5.</ref>
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== Problems ==
== Problems ==


* '''Type 2 diabetes mellitus''' — first- or second-line per [[ADA Standards of Care|ADA 2025 Standards of Care]],<ref name="ada2025">American Diabetes Association. ''Standards of Care in Diabetes — 2025.'' ''Diabetes Care'' 48(Suppl. 1):S1–S352. doi:10.2337/dc25-S001</ref> especially when [[ASCVD]], [[heart failure]], [[CKD]], or obesity is co-present
* '''Type 2 diabetes mellitus''', first- or second-line per [[ADA Standards of Care|ADA 2025 Standards of Care]],<ref name="ada2025">American Diabetes Association. ''Standards of Care in Diabetes, 2025.'' ''Diabetes Care'' 48(Suppl. 1):S1–S352. doi:10.2337/dc25-S001</ref> especially when [[ASCVD]], [[heart failure]], [[CKD]], or obesity is co-present
* '''Obesity or overweight with weight-related comorbidity''' — BMI ≥30, or ≥27 with a weight-related condition (semaglutide 2.4 mg,<ref name="wegovy-label">US FDA. ''Wegovy (semaglutide) prescribing information.'' Novo Nordisk. https://www.accessdata.fda.gov/drugsatfda_docs/label/2021/215256s000lbl.pdf</ref> tirzepatide,<ref name="zepbound-label">US FDA. ''Zepbound (tirzepatide) prescribing information.'' Eli Lilly. https://www.accessdata.fda.gov/drugsatfda_docs/label/2023/217806s000lbl.pdf</ref> liraglutide 3 mg<ref name="saxenda-label">US FDA. ''Saxenda (liraglutide) prescribing information.'' Novo Nordisk. https://www.accessdata.fda.gov/drugsatfda_docs/label/2014/206321Orig1s000lbl.pdf</ref>)
* '''Obesity or overweight with weight-related comorbidity''', BMI ≥30, or ≥27 with a weight-related condition (semaglutide 2.4 mg,<ref name="wegovy-label">US FDA. ''Wegovy (semaglutide) prescribing information.'' Novo Nordisk. https://www.accessdata.fda.gov/drugsatfda_docs/label/2021/215256s000lbl.pdf</ref> tirzepatide,<ref name="zepbound-label">US FDA. ''Zepbound (tirzepatide) prescribing information.'' Eli Lilly. https://www.accessdata.fda.gov/drugsatfda_docs/label/2023/217806s000lbl.pdf</ref> liraglutide 3 mg<ref name="saxenda-label">US FDA. ''Saxenda (liraglutide) prescribing information.'' Novo Nordisk. https://www.accessdata.fda.gov/drugsatfda_docs/label/2014/206321Orig1s000lbl.pdf</ref>)
* '''Cardiovascular risk reduction in obesity without T2DM''' — semaglutide 2.4 mg (SELECT)<ref name="select"/>
* '''Cardiovascular risk reduction in obesity without T2DM''', semaglutide 2.4 mg (SELECT)<ref name="select"/>
* '''MASH with stage 2–3 fibrosis''' — semaglutide (FDA 2025, based on ESSENCE)<ref name="essence"/>
* '''MASH with stage 2–3 fibrosis''', semaglutide (FDA 2025, based on ESSENCE)<ref name="essence"/>
* '''CKD in T2DM''' — semaglutide adjunctive label (FLOW)<ref name="flow"/>
* '''CKD in T2DM''', semaglutide adjunctive label (FLOW)<ref name="flow"/>


== Key trials ==
== Key trials ==
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| '''SUSTAIN-6''' (2016) || Semaglutide SC || T2DM + high CV risk || 26% ↓ MACE<ref name="sustain6">Marso SP et al. (2016). Semaglutide and cardiovascular outcomes in patients with type 2 diabetes (SUSTAIN-6). ''NEJM'' 375:1834–44. doi:10.1056/NEJMoa1607141</ref>
| '''SUSTAIN-6''' (2016) || Semaglutide SC || T2DM + high CV risk || 26% ↓ MACE<ref name="sustain6">Marso SP et al. (2016). Semaglutide and cardiovascular outcomes in patients with type 2 diabetes (SUSTAIN-6). ''NEJM'' 375:1834–44. doi:10.1056/NEJMoa1607141</ref>
|-
|-
| '''REWIND''' (2019) || Dulaglutide || T2DM + CV risk or established CVD || 12% ↓ MACE — first GLP-1 RA benefit shown in ''primary'' prevention<ref name="rewind">Gerstein HC et al. (2019). Dulaglutide and cardiovascular outcomes in type 2 diabetes (REWIND). ''Lancet'' 394(10193):121–30. doi:10.1016/S0140-6736(19)31149-3</ref>
| '''REWIND''' (2019) || Dulaglutide || T2DM + CV risk or established CVD || 12% ↓ MACE, first GLP-1 RA benefit shown in ''primary'' prevention<ref name="rewind">Gerstein HC et al. (2019). Dulaglutide and cardiovascular outcomes in type 2 diabetes (REWIND). ''Lancet'' 394(10193):121–30. doi:10.1016/S0140-6736(19)31149-3</ref>
|-
|-
| '''PIONEER-6''' (2019) || Semaglutide PO || T2DM + high CV risk || Non-inferior to placebo<ref name="pioneer6">Husain M et al. (2019). Oral semaglutide and cardiovascular outcomes in patients with type 2 diabetes (PIONEER-6). ''NEJM'' 381:841–51. doi:10.1056/NEJMoa1901118</ref>
| '''PIONEER-6''' (2019) || Semaglutide PO || T2DM + high CV risk || Non-inferior to placebo<ref name="pioneer6">Husain M et al. (2019). Oral semaglutide and cardiovascular outcomes in patients with type 2 diabetes (PIONEER-6). ''NEJM'' 381:841–51. doi:10.1056/NEJMoa1901118</ref>
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| '''SURMOUNT-1''' (2022) || Tirzepatide || Obesity without T2DM || Up to ~22.5% body-weight loss at 72 wk<ref name="surmount1"/>
| '''SURMOUNT-1''' (2022) || Tirzepatide || Obesity without T2DM || Up to ~22.5% body-weight loss at 72 wk<ref name="surmount1"/>
|-
|-
| '''SELECT''' (2023) || Semaglutide 2.4 mg || Obesity + established CVD, no T2DM || 20% ↓ MACE — landmark for obesity as a CV target<ref name="select"/>
| '''SELECT''' (2023) || Semaglutide 2.4 mg || Obesity + established CVD, no T2DM || 20% ↓ MACE, landmark for obesity as a CV target<ref name="select"/>
|-
|-
| '''STEP-HFpEF''' (2023) || Semaglutide || HFpEF + obesity || ↑ functional capacity (KCCQ), ↓ weight<ref name="stephfpef">Kosiborod MN et al. (2023). Semaglutide in patients with heart failure with preserved ejection fraction and obesity (STEP-HFpEF). ''NEJM'' 389:1069–84. doi:10.1056/NEJMoa2306963</ref>
| '''STEP-HFpEF''' (2023) || Semaglutide || HFpEF + obesity || ↑ functional capacity (KCCQ), ↓ weight<ref name="stephfpef">Kosiborod MN et al. (2023). Semaglutide in patients with heart failure with preserved ejection fraction and obesity (STEP-HFpEF). ''NEJM'' 389:1069–84. doi:10.1056/NEJMoa2306963</ref>
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'''Serious / labeled''':
'''Serious / labeled''':
* '''Pancreatitis''' — labeled warning.<ref name="ozempic-label"/> Real-world data are mixed; recent large cohorts do not show a clear increase, and some show ''decreased'' acute pancreatitis incidence.<ref name="sattar2021"/>
* '''Pancreatitis''', labeled warning.<ref name="ozempic-label"/> Real-world data are mixed; recent large cohorts do not show a clear increase, and some show ''decreased'' acute pancreatitis incidence.<ref name="sattar2021"/>
* '''Gallbladder disease''' — cholelithiasis is partly driven by rapid weight loss.<ref name="wegovy-label"/>
* '''Gallbladder disease''', cholelithiasis is partly driven by rapid weight loss.<ref name="wegovy-label"/>
* '''Medullary thyroid carcinoma (MTC) / C-cell hyperplasia''' — boxed warning,<ref name="ozempic-label"/> based on rodent data. Humans show no calcitonin signal. Long-term follow-up >10 years has not been associated with increased thyroid cancer.<ref name="pollack2025">Pollack R, Stokar J (2025). Long-term GLP-1 receptor agonist use is not associated with incident thyroid cancer. ''Diabetes Metab Res Rev'' 41(8):e70104.</ref> The Bezin 2023 French case-control study found a weak signal that remains heavily debated.<ref name="bezin2023">Bezin J et al. (2023). GLP-1 receptor agonists and the risk of thyroid cancer. ''Diabetes Care'' 46(2):384–90. doi:10.2337/dc22-1148</ref> '''Contraindicated in personal or family history of MTC or [[MEN2]].'''<ref name="ozempic-label"/>
* '''Medullary thyroid carcinoma (MTC) / C-cell hyperplasia''', boxed warning,<ref name="ozempic-label"/> based on rodent data. Humans show no calcitonin signal. Long-term follow-up >10 years has not been associated with increased thyroid cancer.<ref name="pollack2025">Pollack R, Stokar J (2025). Long-term GLP-1 receptor agonist use is not associated with incident thyroid cancer. ''Diabetes Metab Res Rev'' 41(8):e70104.</ref> The Bezin 2023 French case-control study found a weak signal that remains heavily debated.<ref name="bezin2023">Bezin J et al. (2023). GLP-1 receptor agonists and the risk of thyroid cancer. ''Diabetes Care'' 46(2):384–90. doi:10.2337/dc22-1148</ref> '''Contraindicated in personal or family history of MTC or [[MEN2]].'''<ref name="ozempic-label"/>
* '''[[NAION]]''' (non-arteritic anterior ischemic optic neuropathy) — emerging signal. Small absolute risk increase.<ref name="hsu2025">Hathaway JT, Shah MP, Hathaway DB et al. (2024). Risk of nonarteritic anterior ischemic optic neuropathy in patients prescribed semaglutide. ''JAMA Ophthalmol'' 142(8):732–9. doi:10.1001/jamaophthalmol.2024.2296</ref>
* '''[[NAION]]''' (non-arteritic anterior ischemic optic neuropathy), emerging signal. Small absolute risk increase.<ref name="hsu2025">Hathaway JT, Shah MP, Hathaway DB et al. (2024). Risk of nonarteritic anterior ischemic optic neuropathy in patients prescribed semaglutide. ''JAMA Ophthalmol'' 142(8):732–9. doi:10.1001/jamaophthalmol.2024.2296</ref>
* '''Aspiration risk under anesthesia''' — delayed gastric emptying. [[American Society of Anesthesiologists|ASA]] 2024 guidance: hold weekly agents 7 days pre-op; daily agents skip the morning dose.<ref name="kindel2024">Kindel TL et al. (2024). Perioperative GLP-1 receptor agonist safety guidance. ''Surg Obes Relat Dis'' 20(12):1183–8.</ref>
* '''Aspiration risk under anesthesia''', delayed gastric emptying. [[American Society of Anesthesiologists|ASA]] 2024 guidance: hold weekly agents 7 days pre-op; daily agents skip the morning dose.<ref name="kindel2024">Kindel TL et al. (2024). Perioperative GLP-1 receptor agonist safety guidance. ''Surg Obes Relat Dis'' 20(12):1183–8.</ref>
* '''Suicidality''' — initial EMA signal not replicated. Subsequent large studies suggest ''reduced'' suicidal ideation.<ref name="wang2024">Wang W, Volkow ND, Berger NA et al. (2024). Association of semaglutide with risk of suicidal ideation in a real-world cohort. ''Nat Med'' 30:168–76. doi:10.1038/s41591-023-02672-2</ref> FDA removed suicidality warnings January 2026.{{Citation needed}}
* '''Suicidality''', initial EMA signal not replicated. Subsequent large studies suggest ''reduced'' suicidal ideation.<ref name="wang2024">Wang W, Volkow ND, Berger NA et al. (2024). Association of semaglutide with risk of suicidal ideation in a real-world cohort. ''Nat Med'' 30:168–76. doi:10.1038/s41591-023-02672-2</ref> FDA removed suicidality warnings January 2026.{{Citation needed}}


'''Other monitored''':<ref name="ozempic-label"/>
'''Other monitored''':<ref name="ozempic-label"/>
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The discovery story is one of the great late-20th-century pharmacological narratives.
The discovery story is one of the great late-20th-century pharmacological narratives.


Native GLP-1 was isolated in the late 1980s by Jens Juul Holst (Copenhagen) and Daniel Drucker (Toronto).<ref name="holst2022"/> Its therapeutic potential was obvious — and so was its problem: a 2-minute plasma half-life.<ref name="holst2022"/>
Native GLP-1 was isolated in the late 1980s by Jens Juul Holst (Copenhagen) and Daniel Drucker (Toronto).<ref name="holst2022"/> Its therapeutic potential was obvious, and so was its problem: a 2-minute plasma half-life.<ref name="holst2022"/>


In 1992, John Eng, an endocrinologist at the Bronx VA Medical Center, was reading work by Pisano and Raufman noting that the venom of the [[Gila monster]] (''Heloderma suspectum'') caused [[pancreatitis]] in laboratory animals.{{Citation needed}} Eng hypothesized that the venom must contain something incretin-like — and isolated exendin-4, a 39-amino-acid peptide 53% homologous to human GLP-1, but naturally resistant to DPP-4 cleavage.<ref name="eng1992"/> The VA declined to patent the discovery, so Eng patented it personally in 1993, licensed it to Amylin Pharmaceuticals, and the rest of the class — Byetta in 2005, then Victoza, Trulicity, Ozempic, Mounjaro — flowed from that single venom isolation.{{Citation needed}}
In 1992, John Eng, an endocrinologist at the Bronx VA Medical Center, was reading work by Pisano and Raufman noting that the venom of the [[Gila monster]] (''Heloderma suspectum'') caused [[pancreatitis]] in laboratory animals.{{Citation needed}} Eng hypothesized that the venom must contain something incretin-like, and isolated exendin-4, a 39-amino-acid peptide 53% homologous to human GLP-1, but naturally resistant to DPP-4 cleavage.<ref name="eng1992"/> The VA declined to patent the discovery, so Eng patented it personally in 1993, licensed it to Amylin Pharmaceuticals, and the rest of the class, Byetta in 2005, then Victoza, Trulicity, Ozempic, Mounjaro, flowed from that single venom isolation.{{Citation needed}}


== Spending and access context ==
== Spending and access context ==
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* Mounjaro: $2.4 billion Part D (first full year)
* Mounjaro: $2.4 billion Part D (first full year)


These are gross figures — net spend after manufacturer rebates is materially lower, often 30–50% off list.<ref name="cms2023"/>
These are gross figures, net spend after manufacturer rebates is materially lower, often 30–50% off list.<ref name="cms2023"/>


== See also ==
== See also ==
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<references/>
<references/>


[[Category:MedCategory]]
[[Category:GLP-1 receptor agonists]]
[[Category:GLP-1 receptor agonists]]
[[Category:Antidiabetic medicines]]
[[Category:Antidiabetic medicines]]
[[Category:Anti-obesity medicines]]
[[Category:Anti-obesity medicines]]

Latest revision as of 18:00, 19 May 2026

GLP-1 receptor agonists (GLP-1 RAs, also called incretin mimetics) are a class of injectable and (in one case) oral peptide medicines that bind and activate the GLP-1 receptor.[1] They were originally developed for type 2 diabetes mellitus and have since become first-line for obesity,[2][3] approved for cardiovascular risk reduction in obesity without diabetes,[4] chronic kidney disease in T2DM,[5] and MASH with stage 2–3 fibrosis.[6]

As of 2023, GLP-1 RAs were the largest growth driver in US outpatient medicine spending, Ozempic alone accounted for $9.2 billion in Medicare Part D, second only to Eliquis across all federal programs.[7]

Mechanism

The GLP-1 receptor is a class B G-protein-coupled receptor expressed on pancreatic β-cells, hypothalamic satiety neurons, gastric smooth muscle, cardiomyocytes, vascular endothelium, and renal tubules.[1][8] Activation produces:

  • β-cell: glucose-dependent insulin secretion, meaning hypoglycemia risk is low compared to sulfonylureas or insulin[1]
  • α-cell: glucagon suppression[1]
  • Stomach: delayed gastric emptying → improved postprandial glucose and prolonged satiety[1]
  • CNS: hypothalamic appetite suppression and modulation of reward circuitry, the mechanism behind both the weight loss and the widely-reported "food noise" quieting[citation needed]
  • Cardiovascular and renal: independent of glycemia, endothelial improvement, natriuresis, weight-mediated and weight-independent blood pressure reduction, plaque stabilization[9]

Native GLP-1 is rapidly cleaved by DPP-4 and has a plasma half-life of approximately 2 minutes.[8] Every clinically useful GLP-1 RA is engineered for DPP-4 resistance, either by amino-acid substitution at position 2 (liraglutide, semaglutide),[1] structural fusion (dulaglutide's Fc domain),[10] or by being a non-mammalian peptide (exenatide, from Gila monster venom).[11]

Approved agents

Generic Brand(s) Maker Route Dosing First FDA approval Notes
Exenatide Byetta (BID), Bydureon (weekly) AstraZeneca (originally Amylin) SC BID or 1×/wk 2005[12] First-in-class. Exendin-4 from Heloderma suspectum venom.[11] US commercial market discontinued 2024.[citation needed]
Liraglutide Victoza (T2DM), Saxenda (obesity) Novo Nordisk SC Daily 2010 (T2DM), 2014 (obesity)[13] First daily GLP-1 RA. Acylated for albumin binding.[1]
Albiglutide Tanzeum GSK SC Weekly 2014[14] Withdrawn 2017 (commercial reasons).[citation needed]
Dulaglutide Trulicity Eli Lilly SC Weekly 2014[10] Fc-fusion construct.[10]
Lixisenatide Adlyxin (US), Lyxumia (EU) Sanofi SC Daily 2016[15] Withdrawn US 2023.[citation needed]
Semaglutide Ozempic (T2DM SC), Wegovy (obesity SC), Rybelsus (oral T2DM) Novo Nordisk SC or oral Weekly SC / Daily PO 2017 SC, 2019 PO[16][17] Highest-revenue medicine globally (2024).[citation needed] Wegovy 2.4 mg also approved for CV risk reduction in obesity[4] and MASH with fibrosis.[6]
Tirzepatide Mounjaro (T2DM), Zepbound (obesity) Eli Lilly SC Weekly 2022 (T2DM), 2023 (obesity)[18] Dual GLP-1 + GIP agonist ("twincretin"). Superior weight loss vs semaglutide in SURPASS-2[19] and SURMOUNT-1.[3]

Problems

  • Type 2 diabetes mellitus, first- or second-line per ADA 2025 Standards of Care,[20] especially when ASCVD, heart failure, CKD, or obesity is co-present
  • Obesity or overweight with weight-related comorbidity, BMI ≥30, or ≥27 with a weight-related condition (semaglutide 2.4 mg,[21] tirzepatide,[22] liraglutide 3 mg[23])
  • Cardiovascular risk reduction in obesity without T2DM, semaglutide 2.4 mg (SELECT)[4]
  • MASH with stage 2–3 fibrosis, semaglutide (FDA 2025, based on ESSENCE)[6]
  • CKD in T2DM, semaglutide adjunctive label (FLOW)[5]

Key trials

Trial Agent Population Primary result
LEADER (2016) Liraglutide T2DM + high CV risk 13% ↓ MACE[24]
SUSTAIN-6 (2016) Semaglutide SC T2DM + high CV risk 26% ↓ MACE[25]
REWIND (2019) Dulaglutide T2DM + CV risk or established CVD 12% ↓ MACE, first GLP-1 RA benefit shown in primary prevention[26]
PIONEER-6 (2019) Semaglutide PO T2DM + high CV risk Non-inferior to placebo[27]
SURPASS-2 (2021) Tirzepatide vs semaglutide T2DM Tirzepatide superior on HbA1c and weight[19]
STEP-1 (2021) Semaglutide 2.4 mg Obesity without T2DM ~14.9% body-weight loss at 68 wk[2]
SURMOUNT-1 (2022) Tirzepatide Obesity without T2DM Up to ~22.5% body-weight loss at 72 wk[3]
SELECT (2023) Semaglutide 2.4 mg Obesity + established CVD, no T2DM 20% ↓ MACE, landmark for obesity as a CV target[4]
STEP-HFpEF (2023) Semaglutide HFpEF + obesity ↑ functional capacity (KCCQ), ↓ weight[28]
FLOW (2024) Semaglutide T2DM + CKD 24% ↓ kidney + CV events; stopped early for efficacy[5]
ESSENCE (2025) Semaglutide 2.4 mg MASH + fibrosis Histologic improvement; basis for FDA approval[6]

Adverse effects

Common (≥10%, often dose-limiting):[16][21]

  • Nausea, vomiting, diarrhea, constipation, dyspepsia, abdominal pain
  • Worse during dose escalation; mostly tolerable with slow titration
  • Approximately 75% of exenatide users experience GI side effects;[citation needed] fewer with long-acting weekly agents

Serious / labeled:

  • Pancreatitis, labeled warning.[16] Real-world data are mixed; recent large cohorts do not show a clear increase, and some show decreased acute pancreatitis incidence.[9]
  • Gallbladder disease, cholelithiasis is partly driven by rapid weight loss.[21]
  • Medullary thyroid carcinoma (MTC) / C-cell hyperplasia, boxed warning,[16] based on rodent data. Humans show no calcitonin signal. Long-term follow-up >10 years has not been associated with increased thyroid cancer.[29] The Bezin 2023 French case-control study found a weak signal that remains heavily debated.[30] Contraindicated in personal or family history of MTC or MEN2.[16]
  • NAION (non-arteritic anterior ischemic optic neuropathy), emerging signal. Small absolute risk increase.[31]
  • Aspiration risk under anesthesia, delayed gastric emptying. ASA 2024 guidance: hold weekly agents 7 days pre-op; daily agents skip the morning dose.[32]
  • Suicidality, initial EMA signal not replicated. Subsequent large studies suggest reduced suicidal ideation.[33] FDA removed suicidality warnings January 2026.[citation needed]

Other monitored:[16]

  • Hypotension or syncope (volume depletion, especially with diuretics)
  • Acute kidney injury (volume depletion from GI losses)
  • Injection-site reactions (more with exenatide; antibody formation can reduce efficacy)

Interactions

No interactions reported yet.

Discovery

The discovery story is one of the great late-20th-century pharmacological narratives.

Native GLP-1 was isolated in the late 1980s by Jens Juul Holst (Copenhagen) and Daniel Drucker (Toronto).[8] Its therapeutic potential was obvious, and so was its problem: a 2-minute plasma half-life.[8]

In 1992, John Eng, an endocrinologist at the Bronx VA Medical Center, was reading work by Pisano and Raufman noting that the venom of the Gila monster (Heloderma suspectum) caused pancreatitis in laboratory animals.[citation needed] Eng hypothesized that the venom must contain something incretin-like, and isolated exendin-4, a 39-amino-acid peptide 53% homologous to human GLP-1, but naturally resistant to DPP-4 cleavage.[11] The VA declined to patent the discovery, so Eng patented it personally in 1993, licensed it to Amylin Pharmaceuticals, and the rest of the class, Byetta in 2005, then Victoza, Trulicity, Ozempic, Mounjaro, flowed from that single venom isolation.[citation needed]

Spending and access context

Per CMS 2023 spending data:[7]

  • Diabetes is the single largest Medicare Part D therapeutic class at $59.4 billion in 2023
  • GLP-1 RAs drove most of the +$13.8 billion class growth that year
  • Ozempic: $9.2 billion Part D (#2 single medicine across all federal programs, after Eliquis)
  • Trulicity: $7.4 billion Part D, $2.9 billion Medicaid
  • Mounjaro: $2.4 billion Part D (first full year)

These are gross figures, net spend after manufacturer rebates is materially lower, often 30–50% off list.[7]

See also

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Drucker DJ (2022). GLP-1 physiology informs the pharmacotherapy of obesity. Mol Metab 57:101351. doi:10.1016/j.molmet.2021.101351
  2. ↑ 2.0 2.1 Wilding JPH et al. (2021). Once-weekly semaglutide in adults with overweight or obesity (STEP-1). NEJM 384:989. doi:10.1056/NEJMoa2032183
  3. ↑ 3.0 3.1 3.2 Jastreboff AM et al. (2022). Tirzepatide once weekly for the treatment of obesity (SURMOUNT-1). NEJM 387:205. doi:10.1056/NEJMoa2206038
  4. ↑ 4.0 4.1 4.2 4.3 Lincoff AM et al. (2023). Semaglutide and cardiovascular outcomes in obesity without diabetes (SELECT). NEJM 389:2221–32. doi:10.1056/NEJMoa2307563
  5. ↑ 5.0 5.1 5.2 Perkovic V et al. (2024). Effects of semaglutide on chronic kidney disease in patients with type 2 diabetes (FLOW). NEJM 391:109. doi:10.1056/NEJMoa2403347
  6. ↑ 6.0 6.1 6.2 6.3 Newsome PN et al. (2025). Semaglutide in MASH (ESSENCE). FDA approval basis. [citation needed]
  7. ↑ 7.0 7.1 7.2 Centers for Medicare & Medicaid Services. Medicare Part D Drug Spending Dashboard, 2023. Gross spending, not net of manufacturer rebates. Available at: https://data.cms.gov/summary-statistics-on-use-and-payments/medicare-medicaid-spending-by-drug
  8. ↑ 8.0 8.1 8.2 8.3 Holst JJ (2022). GLP-1 incretin and pleiotropic hormone with pharmacological promise. Curr Opin Pharmacol 63:102189.
  9. ↑ 9.0 9.1 Sattar N et al. (2021). Cardiovascular, mortality, and kidney outcomes with GLP-1 receptor agonists in patients with type 2 diabetes: a systematic review and meta-analysis. Lancet Diabetes Endocrinol 9(10):653–62. doi:10.1016/S2213-8587(21)00203-5
  10. ↑ 10.0 10.1 10.2 US FDA. Trulicity (dulaglutide) prescribing information. Eli Lilly and Company. https://www.accessdata.fda.gov/drugsatfda_docs/label/2022/125469s044lbl.pdf
  11. ↑ 11.0 11.1 11.2 Eng J et al. (1992). Isolation and characterization of exendin-4, an exendin-3 analogue, from Heloderma suspectum venom. J Biol Chem 267(11):7402–5.
  12. ↑ US FDA. Byetta (exenatide) approval history. https://www.accessdata.fda.gov/drugsatfda_docs/label/2009/021773s9s11s18s22s25lbl.pdf
  13. ↑ US FDA. Victoza (liraglutide) prescribing information. Novo Nordisk. https://www.accessdata.fda.gov/drugsatfda_docs/label/2017/022341s027lbl.pdf
  14. ↑ US FDA. Tanzeum (albiglutide) approval letter, 15 April 2014.
  15. ↑ US FDA. Adlyxin (lixisenatide) approval letter, 27 July 2016.
  16. ↑ 16.0 16.1 16.2 16.3 16.4 16.5 US FDA. Ozempic (semaglutide) prescribing information. Novo Nordisk. https://www.accessdata.fda.gov/drugsatfda_docs/label/2022/209637s019lbl.pdf
  17. ↑ US FDA. Rybelsus (semaglutide) prescribing information. Novo Nordisk. https://www.accessdata.fda.gov/drugsatfda_docs/label/2019/213051s000lbl.pdf
  18. ↑ US FDA. Mounjaro (tirzepatide) prescribing information. Eli Lilly. https://www.accessdata.fda.gov/drugsatfda_docs/label/2022/215866s000lbl.pdf
  19. ↑ 19.0 19.1 Frías JP et al. (2021). Tirzepatide versus semaglutide once weekly in patients with type 2 diabetes (SURPASS-2). NEJM 385(6):503–15. doi:10.1056/NEJMoa2107519
  20. ↑ American Diabetes Association. Standards of Care in Diabetes, 2025. Diabetes Care 48(Suppl. 1):S1–S352. doi:10.2337/dc25-S001
  21. ↑ 21.0 21.1 21.2 US FDA. Wegovy (semaglutide) prescribing information. Novo Nordisk. https://www.accessdata.fda.gov/drugsatfda_docs/label/2021/215256s000lbl.pdf
  22. ↑ US FDA. Zepbound (tirzepatide) prescribing information. Eli Lilly. https://www.accessdata.fda.gov/drugsatfda_docs/label/2023/217806s000lbl.pdf
  23. ↑ US FDA. Saxenda (liraglutide) prescribing information. Novo Nordisk. https://www.accessdata.fda.gov/drugsatfda_docs/label/2014/206321Orig1s000lbl.pdf
  24. ↑ Marso SP et al. (2016). Liraglutide and cardiovascular outcomes in type 2 diabetes (LEADER). NEJM 375:311–22. doi:10.1056/NEJMoa1603827
  25. ↑ Marso SP et al. (2016). Semaglutide and cardiovascular outcomes in patients with type 2 diabetes (SUSTAIN-6). NEJM 375:1834–44. doi:10.1056/NEJMoa1607141
  26. ↑ Gerstein HC et al. (2019). Dulaglutide and cardiovascular outcomes in type 2 diabetes (REWIND). Lancet 394(10193):121–30. doi:10.1016/S0140-6736(19)31149-3
  27. ↑ Husain M et al. (2019). Oral semaglutide and cardiovascular outcomes in patients with type 2 diabetes (PIONEER-6). NEJM 381:841–51. doi:10.1056/NEJMoa1901118
  28. ↑ Kosiborod MN et al. (2023). Semaglutide in patients with heart failure with preserved ejection fraction and obesity (STEP-HFpEF). NEJM 389:1069–84. doi:10.1056/NEJMoa2306963
  29. ↑ Pollack R, Stokar J (2025). Long-term GLP-1 receptor agonist use is not associated with incident thyroid cancer. Diabetes Metab Res Rev 41(8):e70104.
  30. ↑ Bezin J et al. (2023). GLP-1 receptor agonists and the risk of thyroid cancer. Diabetes Care 46(2):384–90. doi:10.2337/dc22-1148
  31. ↑ Hathaway JT, Shah MP, Hathaway DB et al. (2024). Risk of nonarteritic anterior ischemic optic neuropathy in patients prescribed semaglutide. JAMA Ophthalmol 142(8):732–9. doi:10.1001/jamaophthalmol.2024.2296
  32. ↑ Kindel TL et al. (2024). Perioperative GLP-1 receptor agonist safety guidance. Surg Obes Relat Dis 20(12):1183–8.
  33. ↑ Wang W, Volkow ND, Berger NA et al. (2024). Association of semaglutide with risk of suicidal ideation in a real-world cohort. Nat Med 30:168–76. doi:10.1038/s41591-023-02672-2
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