Exenatide

Origin and structure

Exenatide is the synthetic form of exendin-4, a peptide that John Eng and colleagues at the Veterans Affairs Medical Center in the Bronx, New York, isolated in 1992 from the venom of the Gila monster (Heloderma suspectum), a venomous lizard. It is a chain of 39 amino acids. According to the EMA's assessment, its sequence overlaps that of human GLP-1 by 53%, and unlike the human hormone it is not broken down by DPP-4, the enzyme that gives GLP-1 a half-life of only 1 to 2 minutes. Exenatide therefore lasts hours rather than minutes: after an injection of the twice-daily form its half-life is about 2.4 hours. In diabetic mice it lowered blood glucose at doses about a thousand times lower than GLP-1.

Amylin Pharmaceuticals developed it under the code AC2993, and in April 2005 it became the first GLP-1 receptor agonist approved anywhere, as Byetta: a pen delivering 5 or 10 micrograms, injected twice a day before meals. Bydureon packs 2 mg of exenatide into slowly dissolving polymer microspheres for one injection a week; blood levels build up over 6 to 7 weeks and fall below detection about 10 weeks after the last dose. A ready-mixed version, Bydureon BCise, was added in 2017 in the US and in 2018 in the EU. In the EU both authorisations were first held by Eli Lilly's Dutch subsidiary, Eli Lilly Nederland B.V.; they passed to Bristol-Myers Squibb and AstraZeneca in 2013 and to AstraZeneca alone in 2014.

How it works

Exenatide binds to the human GLP-1 receptor and activates it. In the pancreas it raises insulin release only while blood glucose is high, and the effect subsides as glucose falls, which is why on its own it rarely causes low blood sugar. It suppresses glucagon, so the liver releases less glucose, without blunting the glucagon response to a hypo. It also slows the emptying of the stomach, which flattens the rise in glucose after a meal, and it reduces food intake through less appetite and earlier fullness.

The weekly form keeps a steadier level than the twice-daily form and lowered fasting glucose more in head-to-head trials (by 2.3 against 1.4 mmol/l over 30 weeks). Exenatide is cleared by the kidneys, filtered and then broken down, which is why neither product was recommended in severe kidney impairment (a clearance below 30 ml/min).

Is exenatide approved?

It was, in both the EU and the US, but the medicines have been taken off the market. AstraZeneca asked for the EU authorisations of Byetta and Bydureon to be withdrawn because it had decided, for commercial reasons, to stop marketing them for good, and the European Commission withdrew both on 1 January 2026. They were the only exenatide medicines with an EU-wide authorisation, and because they were authorised EU-wide, the withdrawal also ended their authorisation in the Netherlands, where both had been prescription-only.

Exenatide offered as a research chemical is not one of these medicines. It has no marketing authorisation, is not made under a medicines licence and may not be used in people. The approvals below describe the licensed products only.

• EU: Byetta authorised on 20 November 2006 for type 2 diabetes, on top of metformin and/or a sulfonylurea; use with a thiazolidinedione was added in 2010 and with basal insulin in 2012. Bydureon authorised on 17 June 2011, the first GLP-1 agonist given once a week; combination with basal insulin was added in 2017, the BCise pen in 2018, and adolescents and children from 10 years in 2022. Both authorisations were withdrawn on 1 January 2026 at AstraZeneca's request.
• US: Byetta approved on 28 April 2005, the first medicine of its class; Bydureon on 27 January 2012, the Bydureon Pen in February 2014 and Bydureon BCise on 20 October 2017. On 22 July 2021 the weekly products were approved for children from 10 years. AstraZeneca stopped marketing the brands in the US, and at its request the FDA withdrew the approvals of Byetta, Bydureon and Bydureon BCise with effect from 3 September 2025.
• US generic: the FDA approved Amneal's copy of Byetta on 19 November 2024. In October 2026 the FDA's Drugs@FDA database lists it as discontinued, as it does Byetta, Bydureon and Bydureon BCise.

What the research shows

Exenatide was tested first in randomised trials in type 2 diabetes, sponsored by its manufacturers, then in a large cardiovascular outcome trial and, by academic groups funded by charities and the UK's National Institute for Health and Care Research, in Parkinson's disease. The headline results:

• Byetta: in three 30-week placebo-controlled trials in 1,446 people on metformin, a sulfonylurea or both, HbA1c fell by 0.89 percentage points on 10 micrograms twice daily, against a rise of 0.08 on placebo; body weight fell by 1.9 kg against 0.65 kg.
• DURATION-1 (Lancet 2008): 295 people; after 30 weeks HbA1c fell by 1.9 points on 2 mg once weekly against 1.5 on 10 micrograms twice daily, with a similar weight loss in both groups (3.7 against 3.6 kg).
• DURATION-6 (Lancet 2013): 911 people, head to head with daily liraglutide 1.8 mg; after 26 weeks HbA1c fell by 1.28 points on weekly exenatide against 1.48 on liraglutide, so exenatide missed the margin for non-inferiority. Nausea was less common on exenatide (9% against 21%).
• EXSCEL (NEJM 2017): 14,752 people with type 2 diabetes, 73% of them with previous cardiovascular disease, followed for a median of 3.2 years; cardiovascular death, heart attack or stroke in 11.4% on weekly exenatide against 12.2% on placebo (hazard ratio 0.91, 95% CI 0.83 to 1.00). That showed safety but not benefit (P=0.06 for superiority). Death from any cause was 6.9% against 7.9% (hazard ratio 0.86), a difference not counted as significant under the trial's testing plan.
• Children and adolescents: in a 24-week placebo-controlled trial in 82 young people aged 10 to 17 with type 2 diabetes, weekly exenatide lowered HbA1c by 0.85 points more than placebo, the basis for the paediatric indications.
• Exenatide-PD (Lancet 2017): 62 people with moderate Parkinson's disease at one London centre; after 48 weeks of weekly exenatide and a 12-week washout, the off-medication motor score (MDS-UPDRS part 3) was 3.5 points better than on placebo.
• Exenatide-PD3 (Lancet 2025): the phase 3 trial in 194 people at six UK hospitals; after 96 weeks the motor score had worsened by 5.7 points on exenatide and by 4.5 on placebo, with no significant difference. The authors found no evidence that exenatide slows Parkinson's disease.
• Imaging: a radioactively labelled form of exendin-4 binds to the GLP-1 receptors on insulinomas, small insulin-producing tumours. In a multicentre study led by Radboudumc in Nijmegen (J Nucl Med 2024, 69 adults), this experimental PET/CT scan located them with 94.4% accuracy, against 64.8% for the standard somatostatin-receptor PET/CT.

Side effects and warnings

Most side effects are gastrointestinal. In the Byetta trials 36% of participants had at least one episode of nausea, mostly mild to moderate and fading with time, and 8% stopped because of side effects, against 3% on placebo. Vomiting and diarrhoea were also very common, and headache, dizziness, indigestion and feeling jittery common. With the weekly form, injection-site reactions were more frequent: 16% against 2 to 7% on comparators in the EU trial data. Small lumps under the skin, from the polymer microspheres, were very common and usually cleared within 4 to 8 weeks; in the US trials of the BCise pen an injection-site nodule was reported by 10.5% and nausea by 8.2%.

The product information warns about acute pancreatitis, in very rare cases necrotising or fatal; uncommon kidney problems up to acute kidney failure, sometimes needing dialysis and partly in people dehydrated by nausea, vomiting or diarrhoea; low blood sugar when combined with a sulfonylurea or insulin; gallstones and gallbladder inflammation; a rise in INR with warfarin; and inhaling stomach contents under general anaesthesia or deep sedation. One rare reaction is specific to exenatide: drug-induced immune thrombocytopenia, in which antibodies that act only in the presence of exenatide destroy blood platelets. Serious, sometimes fatal bleeding has been reported, and the US labels rule out anyone who had it before.

Antibodies against exenatide are common. In the Byetta trials 38% of participants had low levels at 30 weeks and 6% higher levels; about half of the latter, 3% of all users, had no apparent glucose response. With the weekly form about 45% had low and 12% higher levels, and the EU label warns that children may be more prone to high levels. Long-acting exenatide caused thyroid C-cell tumours in rats; the US labels of the weekly products carry a boxed warning and rule out people with a personal or family history of medullary thyroid carcinoma or MEN 2, while the EU label calls the clinical relevance unknown. Because the weekly form takes about 10 weeks to wash out, the EU label asks women to stop it at least three months before a planned pregnancy.

Exenatide versus newer GLP-1 agonists

Exenatide opened the GLP-1 class, but liraglutide and semaglutide, both modified versions of human GLP-1, have since done better where they could be compared. In DURATION-6, daily liraglutide lowered HbA1c more than weekly exenatide (by 1.48 against 1.28 points) and weight more (3.6 against 2.7 kg in the US label's analysis), at the cost of more nausea.

The outcome trials point the same way. LEADER for liraglutide and SUSTAIN 6 for semaglutide showed significantly fewer heart attacks, strokes and cardiovascular deaths in type 2 diabetes, while EXSCEL found no significant reduction (hazard ratio 0.91). The trials enrolled different people, and EXSCEL was pragmatic by design, with participants on the study treatment for a median of 27.8 of their 38.7 months of follow-up, so the results cannot be compared one to one. Exenatide was never authorised for weight management, and its weight effect in diabetes trials was a few kilograms.

Frequently asked questions

Is exenatide still available in the Netherlands?

Not as a medicine. Byetta and Bydureon, the only exenatide medicines with an EU-wide authorisation, lost that authorisation on 1 January 2026, when the European Commission withdrew both at AstraZeneca's request, for commercial reasons. That also ended their authorisation in the Netherlands. Other GLP-1 agonists, such as dulaglutide, liraglutide and semaglutide, remain authorised as prescription medicines.

Is exenatide made from Gila monster venom?

No. Exendin-4 was discovered in the venom in 1992, but the medicine is a synthetic peptide with the same 39-amino-acid sequence, made in a factory rather than taken from lizards. The US label describes it as a synthetic peptide that was originally identified in Heloderma suspectum.

What is the difference between Byetta and Bydureon?

The molecule is the same, the release is not. Byetta was a solution injected twice a day before the two main meals, at 5 or 10 micrograms per dose. Bydureon held 2 mg in slow-release microspheres for one injection a week. In DURATION-1 the weekly form lowered HbA1c a little more than Byetta (by 1.9 against 1.5 points over 30 weeks), but caused more injection-site reactions.

Does exenatide help with Parkinson's disease?

Not on current evidence. A small trial in 62 people (Lancet 2017) found a 3.5-point advantage on a motor score, but the phase 3 trial Exenatide-PD3, in 194 people over 96 weeks, found no difference from placebo (Lancet 2025). Its authors concluded that there is no evidence that exenatide slows the disease. Exenatide has no approval for Parkinson's disease in the EU or the US.

Do you lose weight on exenatide?

A little, in people with type 2 diabetes. Over 30 weeks, Byetta 10 micrograms twice daily lowered weight by 1.9 kg against 0.65 kg on placebo, in DURATION-1 the two forms gave 3.7 and 3.6 kg, and in EXSCEL the average difference from placebo was 1.27 kg. Exenatide was never authorised for weight management. For comparison, adults without diabetes lost 14.9% of their body weight on semaglutide 2.4 mg in STEP 1.

Is exenatide banned in sport?

No. GLP-1 agonists, exenatide included, are not on the WADA Prohibited List, which the Dutch anti-doping rules also apply. The Dopingautoriteit's Dopingwaaier shows the current status of individual medicines.

Storage and handling

Store according to product-label instructions and batch handling notes. Lyophilized research peptides are commonly kept dry, protected from light, and handled with clean laboratory technique.

References

Checked against these sources on 28 October 2026.

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