Exenatide is a glucagon-like peptide-1 (GLP-1) receptor agonist, one of the earliest drugs in the class. It is a synthetic copy of exendin-4, a peptide found in the venom of the Gila monster lizard. FDA approved it in April 2005 as Byetta, a twice-daily injection for type 2 diabetes. A once-weekly extended-release form followed as Bydureon (2012) and Bydureon BCise (2017).
The most important fact today is that exenatide has largely been superseded. Drugs@FDA lists the main Byetta application, Bydureon and Bydureon BCise as discontinued, and the EU withdrew both Byetta and Bydureon on January 1, 2026 at AstraZeneca’s request for commercial reasons. A generic twice-daily exenatide from Amneal (approved November 2024) remains listed as a prescription product. Exenatide was never approved for weight management, and in head-to-head trials it lowered blood sugar and weight less than semaglutide or liraglutide.
This page summarizes what the FDA labels, clinical trials and regulators report. It is for education only and is not medical advice.
| Property | Detail |
|---|---|
| Drug class | GLP-1 receptor agonist (synthetic exendin-4) |
| Brands / first US approval | Byetta (April 28, 2005); Bydureon (January 27, 2012); Bydureon BCise (October 20, 2017); generic exenatide injection, Amneal (November 19, 2024) |
| Route | Subcutaneous injection: twice daily (Byetta, generic) or once weekly (Bydureon, Bydureon BCise) |
| Labeled doses | Twice-daily form: 5 mcg twice daily, increased to 10 mcg twice daily after 1 month; weekly form: 2 mg once every 7 days |
| Half-life (Byetta label) | 2.4 hours; measurable for about 10 hours after a dose |
| Washout of weekly form (label) | Levels fall below the quantifiable limit about 10 weeks after the last dose |
| Approved use | Blood sugar control in type 2 diabetes only; not approved for weight loss |
| Boxed warning | Weekly forms only: thyroid C-cell tumors in rats |
| US / EU status | Byetta (NDA 021773), Bydureon and Bydureon BCise listed as discontinued; EU authorizations withdrawn January 1, 2026 |
| WADA status | Not named on the 2026 Prohibited List |
What it is
Exenatide is a 39-amino-acid peptide amide with the formula C₁₈₄H₂₈₂N₅₀O₆₀S and a molecular weight of 4186.6 Da (Byetta label). It is made synthetically, but its sequence is the natural one: exendin-4, which John Eng’s laboratory isolated from the venom of Heloderma suspectum (the Gila monster) in 1992 (Eng et al., J Biol Chem 1992).
The label describes its sequence as partially overlapping that of human GLP-1. In 1993, experiments in rat insulin-producing cell lines and isolated rat islets showed that exendin-4 binds the GLP-1 receptor and acts as a potent agonist there, raising cAMP and glucose-stimulated insulin release (Göke et al., J Biol Chem 1993).
What made exendin-4 useful as a drug is stability. In a laboratory study using rat and pig kidney membranes, the enzyme dipeptidyl peptidase-4 (DPP-4) was the rate-limiting step in breaking down human GLP-1, while exendin-4 was several orders of magnitude more stable than GLP-1 (Thum et al., Exp Clin Endocrinol Diabetes 2002). Unlike later drugs such as semaglutide, exenatide carries no fatty-acid chain to bind albumin. That is why the plain peptide still needs twice-daily injection, and why the weekly version relies on a slow-release depot instead.
According to the labels, exenatide:
- increases insulin release from the pancreas only when blood glucose is raised, and restored the first-phase insulin response in people with type 2 diabetes;
- lowers glucagon during high blood sugar, without blocking the normal glucagon response to low blood sugar;
- slows stomach emptying, which lowers the rise in glucose after meals;
- reduces food intake in animals and humans.
Two formulations
| Feature | Byetta / generic exenatide | Bydureon BCise (and Bydureon) |
|---|---|---|
| Form | Clear solution, 250 mcg/mL, in a prefilled pen | Exenatide in biodegradable PLGA polymer microspheres suspended in medium-chain triglyceride oil |
| Dose | 5 or 10 mcg twice daily, within 60 minutes before the morning and evening meals | 2 mg once weekly, any time of day, with or without meals |
| Time to steady state | Not applicable (short-acting) | About 10 weeks |
| Boxed warning | None | Risk of thyroid C-cell tumors |
| Approved ages | Adults | Adults and children 10 years and older (BCise) |
Sources: Byetta label; Bydureon BCise label.
Pharmacokinetics
From the Byetta and Bydureon BCise labels:
| Parameter | Twice-daily exenatide (10 mcg dose) | Weekly exenatide (2 mg) |
|---|---|---|
| Time to peak | Median 2.1 hours | Initial release of surface-bound drug, then a peak at about week 6–7 after a single dose |
| Peak level | Mean 211 pg/mL | Steady-state mean about 208 pg/mL from week 10 |
| Volume of distribution | 28.3 L | Expected to be the same |
| Clearance | 9.1 L/hour | 9.1 L/hour |
| Terminal half-life | 2.4 hours | Not stated; release from the depot controls duration |
| After stopping | Measurable for about 10 hours | Below 20 pg/mL about 10 weeks after the last dose |
Exenatide is cleared mainly by the kidneys (glomerular filtration followed by breakdown of the peptide). This makes kidney function the key factor in exposure:
- Twice-daily form. Exposure was similar to normal in mild to moderate kidney impairment (creatinine clearance 30–80 mL/min) but 3.37-fold higher in end-stage kidney disease on dialysis, where single 5 mcg doses were poorly tolerated. The label does not recommend it below a creatinine clearance of 30 mL/min.
- Weekly form. Exposure was 28% higher in mild and 69% higher in moderate kidney impairment. The label does not recommend it below an eGFR of 45 mL/min/1.73 m².
Liver impairment has not been studied, but the labels do not expect it to matter because the kidneys clear the drug. Age, sex, race and body mass index did not meaningfully change its kinetics.
Approved medical use and current status
All exenatide products are approved only as an add-on to diet and exercise to improve blood sugar control in type 2 diabetes. The labels say not to combine exenatide with other exenatide-containing products (Byetta label; Bydureon BCise label).
- Twice daily. Start at 5 mcg twice daily, injected within 60 minutes before the two main meals (at least about 6 hours apart) and never after a meal. The dose can rise to 10 mcg twice daily after 1 month. The maximum labeled dose is therefore 20 mcg/day.
- Once weekly. 2 mg every 7 days, with no titration step.
- Children. Bydureon BCise is approved from age 10. Byetta is not: in a trial of 120 children aged 10–17, its effectiveness was not shown.
Regulatory status, as of the sources checked:
| Product | US status (Drugs@FDA) | EU status (EMA) |
|---|---|---|
| Byetta, NDA 021773 (AstraZeneca) | Discontinued | Authorization withdrawn January 1, 2026 (first authorized November 2006) |
| Bydureon, NDA 022200 | Discontinued | Authorization withdrawn January 1, 2026 (first authorized June 2011) |
| Bydureon BCise, NDA 209210 | Discontinued | — |
| Exenatide injection, ANDA 206697 (Amneal) | Prescription; listed as the reference standard | — |
The EMA states that AstraZeneca asked for the EU withdrawals because it had decided to stop marketing the products “for commercial reasons,” not because of a safety finding (EMA: Byetta; EMA: Bydureon). Exenatide is not a controlled substance.
What the research shows
Blood sugar in type 2 diabetes
In the 24-week placebo-controlled monotherapy trial on the Byetta label (232 patients, baseline HbA1c about 7.8%), results were:
| Arm | HbA1c change | Reached HbA1c under 7% | Weight change |
|---|---|---|---|
| Placebo | −0.2% | 38% | −1.5 kg |
| 5 mcg twice daily | −0.7% | 48% | −2.7 kg |
| 10 mcg twice daily | −0.9% | 53% | −2.9 kg |
HbA1c is a measure of average blood sugar over about 3 months. Added to metformin for 30 weeks, 10 mcg twice daily lowered HbA1c by 0.9% (vs 0.0% on placebo) and weight by 2.6 kg (vs 0.2 kg) (Byetta label).
Weekly vs twice daily
Two randomized trials compared the formulations directly:
- DURATION-1. 295 patients, 30 weeks, open-label. HbA1c fell 1.9% with 2 mg weekly vs 1.5% with 10 mcg twice daily (p = 0.0023), and 77% vs 61% of evaluable patients reached HbA1c of 7.0% or less. Weight loss was similar, with no increase in hypoglycemia (Drucker et al., Lancet 2008).
- Bydureon BCise vs Byetta. 375 patients, 28 weeks, open-label. HbA1c fell 1.39% vs 1.03% (difference −0.36%). Weight fell 1.4 kg on the weekly form and 1.9 kg on the twice-daily form (Bydureon BCise label).
Compared with newer GLP-1 drugs
Head-to-head trials explain why exenatide lost ground to later drugs:
| Trial | Comparison | n, duration | HbA1c change | Weight change | Notes |
|---|---|---|---|---|---|
| DURATION-6 (Buse et al., Lancet 2013) | Exenatide 2 mg weekly vs liraglutide 1.8 mg daily | 911, 26 weeks | −1.28% vs −1.48% | — | Exenatide failed non-inferiority; nausea 9% vs 21% |
| SUSTAIN 3 (Ahmann et al., Diabetes Care 2018) | Exenatide ER 2 mg weekly vs semaglutide 1 mg weekly | 813, 56 weeks | −0.9% vs −1.5% | −1.9 kg vs −5.6 kg | GI side effects 33.3% vs 41.8%; injection-site reactions 22.0% vs 1.2% |
The trade-off is consistent: weekly exenatide caused fewer stomach side effects than liraglutide or semaglutide but produced smaller drops in blood sugar and weight, and many more injection-site reactions. We found no randomized trial comparing exenatide directly with tirzepatide, a newer dual GIP/GLP-1 agonist covered on its own page.
Weight in people without diabetes
Exenatide was never approved for weight loss, and the evidence in obesity is small. In a 24-week trial, 152 adults with obesity but no diabetes (mean BMI 39.6) received 10 mcg twice daily or placebo, both with a diet and activity program (Rosenstock et al., Diabetes Care 2010):
- Weight: −5.1 kg on exenatide vs −1.6 kg on placebo, a placebo-adjusted difference of −3.3% of body weight.
- Calorie intake: fell in both groups (by 449 vs 387 kcal/day).
- Glucose tolerance: prediabetes normalized in 77% vs 56% of those who had it.
For scale, the semaglutide and tirzepatide pages describe much larger, longer obesity trials. We found no controlled trials of exenatide in lean or resistance-trained people, and no data on its effect on muscle in that group.
Cardiovascular outcomes (EXSCEL)
EXSCEL randomized 14,752 people with type 2 diabetes (73.1% with previous cardiovascular disease) to 2 mg weekly or placebo, with a median follow-up of 3.2 years (Holman et al., NEJM 2017; Bydureon BCise label):
| Outcome | Exenatide | Placebo | Hazard ratio (95% CI) |
|---|---|---|---|
| Major cardiovascular events (cardiovascular death, nonfatal heart attack or nonfatal stroke) | 11.4% | 12.2% | 0.91 (0.83–1.00) |
| Cardiovascular death | 4.6% | 5.2% | 0.88 (0.76–1.02) |
| Nonfatal heart attack | 6.3% | 6.5% | 0.96 (0.85–1.09) |
| Nonfatal stroke | 2.3% | 2.6% | 0.86 (0.70–1.06) |
| Death from any cause | 6.9% | 7.9% | — |
Exenatide was shown to be safe for the heart (non-inferior, p under 0.001) but not superior to placebo (p = 0.06). Rates of acute pancreatitis, pancreatic cancer and medullary thyroid carcinoma did not differ significantly between groups. The cardiovascular outcome trials of semaglutide are summarized on its page for comparison.
Parkinson’s disease
Exenatide was tested in Parkinson’s disease because GLP-1 drugs showed nerve-protective effects in laboratory and animal models:
- Phase 2 (Exenatide-PD). 62 patients received 2 mg weekly or placebo for 48 weeks. At 60 weeks (after a 12-week washout), off-medication motor scores differed by 3.5 points in favor of exenatide (95% CI −6.7 to −0.3) (Athauda et al., Lancet 2017).
- Phase 3 (Exenatide-PD3). 194 patients across six UK hospitals received 2 mg weekly or placebo for 96 weeks. Motor scores worsened by 5.7 points on exenatide and 4.5 points on placebo (p = 0.47). The authors found “no evidence to support exenatide as a disease-modifying treatment” (Vijiaratnam et al., Lancet 2025).
In June 2026, The Lancet published an Expression of Concern about the phase 3 paper (Lancet Editors 2026). The notice does not change the reported negative result, but readers should treat the paper with that caution in mind.
Side effects and risks
Boxed warning: thyroid C-cell tumors (weekly forms)
In a 2-year study in rats, extended-release exenatide caused dose- and duration-dependent increases in thyroid C-cell adenomas and carcinomas at all doses tested (2–27 times human exposure). Whether this applies to humans is unknown. Bydureon BCise is contraindicated in people with a personal or family history of medullary thyroid carcinoma (MTC) or with multiple endocrine neoplasia type 2 (MEN 2) (Bydureon BCise label).
The twice-daily product has no boxed warning. Its label reports benign C-cell adenomas in female rats at all doses (14–23% vs 5–8% in controls) and no tumors in a 2-year mouse study.
Gastrointestinal effects
Nausea is the most common side effect and is dose-dependent. In three 30-week trials adding Byetta to metformin and/or a sulfonylurea (963 on Byetta, 483 on placebo) (Byetta label):
| Adverse reaction | Placebo | Byetta |
|---|---|---|
| Nausea | 18% | 44% |
| Vomiting | 4% | 13% |
| Diarrhea | 6% | 13% |
| Feeling jittery | 4% | 9% |
| Dizziness | 6% | 9% |
| Headache | 6% | 9% |
| Dyspepsia | 3% | 6% |
Nausea usually lessened over time, and 3% of patients stopped because of it. In the Bydureon BCise trials, nausea was reported by 8.2% of 526 patients on the weekly form. Both labels warn against use in severe gastroparesis and report postmarketing acute kidney injury, sometimes needing dialysis, mostly after dehydration from vomiting or diarrhea.
Injection-site reactions and nodules (weekly forms)
The polymer microspheres often leave a lump under the skin. Injection-site nodules were the most common side effect of Bydureon BCise (10.5%), and any injection-site reaction occurred in 23.9% of patients. Postmarketing reports include abscess, cellulitis and tissue necrosis, a few of which needed surgery.
Hypoglycemia
Used alone, exenatide caused little hypoglycemia (3.8% on 10 mcg twice daily vs 1.3% on placebo, none severe). The risk rises with a sulfonylurea or insulin. With a sulfonylurea, hypoglycemia occurred in 35.7% on 10 mcg twice daily vs 3.3% on placebo. The labels advise considering a lower sulfonylurea or insulin dose when starting exenatide. In a trial overdose of 100 mcg (10 times the maximum single dose), patients had severe nausea, vomiting and rapidly falling blood sugar; one needed IV glucose.
Immune reactions
- Antibodies. Many patients develop antibodies to exenatide. In the 30-week Byetta trials, 38% had low titers and 6% high titers; a small share (1–4% across trials) had a weakened glucose response because of them.
- Drug-induced thrombocytopenia. Exenatide can trigger antibodies that destroy platelets, causing serious and sometimes fatal bleeding. A history of this reaction is a contraindication, and patients should never be re-exposed. With the weekly form, low platelets can persist for about 10 weeks after stopping.
- Serious allergic reactions, including anaphylaxis and angioedema, have been reported.
Pancreas and gallbladder
Acute pancreatitis, including fatal hemorrhagic or necrotizing cases, has been reported with GLP-1 receptor agonists including exenatide. It occurred in 0.4% of patients in Bydureon BCise trials. In EXSCEL, acute gallbladder events occurred in 1.9% on exenatide vs 1.4% on placebo.
Other label warnings
- Pulmonary aspiration during general anesthesia or deep sedation, because food may remain in the stomach.
- Heart rate rose by a mean of 2.4 beats per minute with Bydureon BCise.
- Pen sharing can spread blood-borne infections, even with a new needle.
Interactions
- Oral drugs. Slower stomach emptying delays absorption. When acetaminophen was taken with or up to 4 hours after Byetta, its peak levels fell by 37–56%. Given 30 minutes before an oral contraceptive, it lowered peak ethinyl estradiol by 45% and levonorgestrel by 27%. The label advises taking contraceptives and antibiotics at least 1 hour before a Byetta injection.
- Lovastatin. Exposure (AUC) fell about 40% when taken 30 minutes after Byetta.
- Warfarin. No effect on INR in a formal study, but postmarketing reports describe raised INR with bleeding. The label advises more frequent monitoring.
- Insulin and sulfonylureas. Higher risk of hypoglycemia (see above).
Who should not use it
- People who have had a severe allergic reaction to exenatide or its ingredients.
- People with a history of exenatide-induced immune thrombocytopenia.
- For the weekly forms: people with a personal or family history of MTC or MEN 2.
- Not recommended in severe kidney impairment (creatinine clearance under 30 mL/min for the twice-daily form; eGFR under 45 for the weekly form) or severe gastroparesis.
- Pregnancy: animal studies showed fetal and newborn harm (in mice and rabbits), and the label says to use it only if the benefit justifies the risk.
Legal status and use outside medicine
Exenatide is a prescription drug and is not a controlled substance. It is not named on the WADA 2026 Prohibited List, and GLP-1 receptor agonists as a class are not listed.
Its “Cutting” label in fitness circles rests on the modest weight loss seen in diabetes and obesity trials. The evidence for that use is limited to the 24-week obesity trial above, and in SUSTAIN 3 semaglutide produced about three times the weight loss of weekly exenatide.
Key takeaways
- An early GLP-1 drug, from lizard venom. Exenatide is synthetic exendin-4 from the Gila monster, approved in the US in 2005 for type 2 diabetes.
- Short-acting unless put in a depot. The plain peptide has a 2.4-hour half-life and is injected twice daily; the weekly form uses polymer microspheres and takes about 10 weeks to wash out.
- Modest effects compared with newer drugs. Weekly exenatide lowered HbA1c by 0.9% and weight by 1.9 kg in SUSTAIN 3, vs 1.5% and 5.6 kg with semaglutide.
- Heart-safe but not heart-protective. EXSCEL showed no increase in cardiovascular events but no significant reduction either (HR 0.91, 95% CI 0.83–1.00).
- Distinct risks. Nausea affected 44% on twice-daily dosing, the weekly form often causes injection-site nodules, and exenatide can trigger rare but dangerous immune thrombocytopenia.
- Being phased out. The branded products are listed as discontinued in the US and were withdrawn in the EU in January 2026; a generic twice-daily form remains.
Sources
- AstraZeneca. Byetta (exenatide) injection, prescribing information, revised September 2025. DailyMed; Drugs@FDA, NDA 021773.
- AstraZeneca. Bydureon BCise (exenatide) extended-release injectable suspension, prescribing information, revised May 2025. FDA; Drugs@FDA, NDA 209210.
- Food and Drug Administration. Drugs@FDA: Bydureon, NDA 022200. FDA.
- Amneal Pharmaceuticals. Exenatide injection, prescribing information. DailyMed; Drugs@FDA, ANDA 206697.
- European Medicines Agency. Byetta (exenatide): withdrawn. EMA.
- European Medicines Agency. Bydureon (exenatide): withdrawn. EMA.
- Eng J, Kleinman WA, Singh L, et al. Isolation and characterization of exendin-4, an exendin-3 analogue, from Heloderma suspectum venom. Further evidence for an exendin receptor on dispersed acini from guinea pig pancreas. J Biol Chem. 1992;267(11):7402–7405. PubMed.
- Göke R, Fehmann HC, Linn T, et al. Exendin-4 is a high potency agonist and truncated exendin-(9-39)-amide an antagonist at the glucagon-like peptide 1-(7-36)-amide receptor of insulin-secreting beta-cells. J Biol Chem. 1993;268(26):19650–19655. PubMed.
- Thum A, Hupe-Sodmann K, Göke R, et al. Endoproteolysis by isolated membrane peptidases reveal metabolic stability of glucagon-like peptide-1 analogs, exendins-3 and -4. Exp Clin Endocrinol Diabetes. 2002;110(3):113–118. PubMed.
- Drucker DJ, Buse JB, Taylor K, et al. Exenatide once weekly versus twice daily for the treatment of type 2 diabetes: a randomised, open-label, non-inferiority study. Lancet. 2008;372(9645):1240–1250. PubMed.
- Buse JB, Nauck M, Forst T, et al. Exenatide once weekly versus liraglutide once daily in patients with type 2 diabetes (DURATION-6): a randomised, open-label study. Lancet. 2013;381(9861):117–124. PubMed.
- Ahmann AJ, Capehorn M, Charpentier G, et al. Efficacy and safety of once-weekly semaglutide versus exenatide ER in subjects with type 2 diabetes (SUSTAIN 3): a 56-week, open-label, randomized clinical trial. Diabetes Care. 2018;41(2):258–266. PubMed.
- Rosenstock J, Klaff LJ, Schwartz S, et al. Effects of exenatide and lifestyle modification on body weight and glucose tolerance in obese subjects with and without pre-diabetes. Diabetes Care. 2010;33(6):1173–1175. PubMed.
- Holman RR, Bethel MA, Mentz RJ, et al. Effects of once-weekly exenatide on cardiovascular outcomes in type 2 diabetes. N Engl J Med. 2017;377(13):1228–1239. PubMed.
- Athauda D, Maclagan K, Skene SS, et al. Exenatide once weekly versus placebo in Parkinson’s disease: a randomised, double-blind, placebo-controlled trial. Lancet. 2017;390(10103):1664–1675. PubMed.
- Vijiaratnam N, Girges C, Auld G, et al. Exenatide once a week versus placebo as a potential disease-modifying treatment for people with Parkinson’s disease in the UK: a phase 3, multicentre, double-blind, parallel-group, randomised, placebo-controlled trial. Lancet. 2025;405(10479):627–636. PubMed.
- The Editors of The Lancet. Expression of Concern: Exenatide once a week versus placebo as a potential disease-modifying treatment for people with Parkinson’s disease in the UK. Lancet. 2026;407(10548):2588. PubMed.
- World Anti-Doping Agency. The 2026 Prohibited List. WADA.