Trofinetide (Daybue)_Dosage, benefits & legal status
Also known as Daybue, Daybue Stix, Daybu, NNZ-2566, ACP-2566
An approved oral treatment for Rett syndrome, built from the first three amino acids of IGF-1 with one methyl group added.
Common vial size is what vendors typically sell, not a recommendation. Enter your own vial in the calculator.
What is Trofinetide (Daybue)?
Plain language first. The technical label stays, but it never stands alone.Overview
It is a twice-daily drink measured in grams that modestly improved behaviour scores in a 12-week trial in girls and young women, at the cost of diarrhoea in about four in five. The label says how it works is unknown. The EU authorised it in August 2026 after first refusing it.
Trofinetide is glycine-proline-glutamate, the first three residues of IGF-1, with an extra methyl group on the proline. Neuren developed it as NNZ-2566 and licensed it to Acadia, and the FDA approved it as Daybue in March 2023 for Rett syndrome in people aged 2 and over.
What it's used for
A prescription oral solution for Rett syndrome. Modest benefit on behaviour and clinician ratings; diarrhoea is very common.
How does Trofinetide (Daybue) work?
What it does in the body, and where.Trofinetide is a synthetic copy of glycine-proline-glutamate (GPE), the tripeptide cut from the front of IGF-1, with a methyl group added to the proline.
- 01Unknown in peopleThe US label states that how it works in Rett syndrome is unknown.
- 02Animal workIn fragile X model mice it corrected learning, activity and social problems and normalised dendritic spine density and overactive ERK and Akt signalling. The company describes reduced brain inflammation and better synaptic function from animal studies.
- 03Not IGF-1It is three amino acids, not the 70-residue hormone, and no source found shows it acting at the IGF-1 receptor. Nothing in the label or the trial papers links it to growth hormone.
What else is it used for?
Each group carries its own evidence level.Approved means regulators have cleared it for that purpose. Investigational means it is in trials. Early research means it is being studied and is not established.
Rett syndrome
FDA-approved- Human trialLAVENDER, 187 participants, 12 weeks: both co-primary measures beat placebo, by 3.2 points on a 90-point behaviour scale and 0.3 points on a 7-point clinician scale.
- Human trialOpen-label extensions: behaviour scores improved 7.3 points by week 40 and 11.8 points by week 104 from the original baseline, with no placebo group; 21% left the 40-week extension because of diarrhoea.
- No dataApproval reaches age 2, but the controlled trial enrolled ages 5 to 20; under-5 evidence is an open-label study of 15 girls.
Fragile X
Investigational- Human trial72 males aged 12 to 45 for 28 days: the 70 mg/kg twice-daily dose met prespecified efficacy criteria; both doses were well tolerated. No later fragile X trial was found.
It is not IGF-1 or an IGF-1 analogue in the usual sense: it copies only the first three of IGF-1's 70 residues, with an added methyl group, so it is not identical to GPE either. Nothing ties it to growth hormone. The label says its mechanism is unknown, so 'reduces neuroinflammation' is an animal-study claim. The diarrhoea rate is quoted as 80%, 82% or 85% depending on the dataset: the trial paper, the label's 12-week table or the label's pooled long-term figure. US approval reaches age 2, but the controlled trial enrolled ages 5 to 20, and the EU limits use to age 5 and over. The EU brand is Daybu, not Daybue. It is not approved for fragile X.
The published record
Papers and trials about Trofinetide (Daybue)
66 papers tagged human · 37 not reviews or lab · 14 clinical trial publications
14 registered trials · 4 with posted results
Furthest stage reached: Approved in the US
Counted from Europe PMC indexing, not read by a person; a human tag can land on reviews, commentary or lab papers; clinical trial publications is the narrower count.
At a glance
Four things to know about Trofinetide (Daybue)
Evidence
FDA-approved
Category
Brain, mood and sleep
Common vial
Varies
Half-life
About 1.5 hours
How much, and do you cycle it?
The range, and whether you take breaks.5,000 to 12,000 mg twice daily by weight (label), twice daily. Continuous, twice daily FDA label
Taken twice a day long term. Open-label follow-up has run for up to about 32 months, with diarrhoea the main reason people stopped.
About 1.5 hoursFDA label
Peak at 2 to 3 hours; at least 84% absorbed; about 80% excreted unchanged in urine and not metabolised by CYP enzymes. Exposure rises about 80% in moderate kidney impairment.
Source: Daybue prescribing information section 12.3
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What does it cost?
Typical dose and cost, in plain numbers.Trofinetide (Daybue) is not injected
It is taken by mouth or gastrostomy tube (oral solution). Twice daily by weight, by mouth or gastrostomy tube, with or without food: 5,000 mg (9 to under 12 kg), 6,000 mg (12 to under 20 kg), 8,000 mg (20 to under 35 kg), 10,000 mg (35 to under 50 kg) and 12,000 mg (50 kg and over). The oral solution is 200 mg/mL, so 25 to 60 mL a dose; Daybue Stix are powder packets dissolved in water. Half doses in moderate kidney impairment. Measured in grams, so the vial calculator does not apply.
How do you store it?
Before mixing, and after.Dry powder in the freezer or fridge. Once mixed, fridge, and use within about a month.
Unmixed lyophilized Trofinetide (Daybue) keeps for a long time cold. Once you add water the clock starts: most reconstituted vials hold up for roughly 28 to 30 days at fridge temperature. Keep it out of light, and do not freeze it after mixing.
What are the side effects and cautions?
Known cautions and warnings for this compound.Who should avoid it
- None on the US label; Health Canada lists hypersensitivity to the drug or its ingredients
- Severe kidney impairment (eGFR below 30): not recommended; moderate impairment needs half doses
- Laxatives: stop them before starting
- Children under 2: not studied
Stop and get help
- Severe diarrhoea, or signs of dehydration such as a dry mouth, little urine or unusual sleepiness
- Weight loss that keeps going
- Coughing, choking or breathing trouble after vomiting, since aspiration pneumonia has been reported
Common effects
- Diarrhoea in 82% against 20% on placebo over 12 weeks; 96% of cases were mild or moderate
- Vomiting in 29% against 12%
- Weight loss of more than 7% in 12% against 4% on placebo
- Fever, seizures, anxiety, lower appetite and tiredness, each in 8 to 9%
- 19% stopped the 12-week trial because of side effects, mostly diarrhoea
Where this page says nothing is established, that means nobody has studied it, not that a compound is safe.
Is Trofinetide (Daybue) approved?
And where the numbers on this page come from.Yes. Trofinetide (Daybue) is FDA approved and available on prescription in the United States. It is also approved in the European Union, Canada, and Israel.
- Approval statusFDA-approved
- RouteBy mouth or gastrostomy tube (oral solution)
- Checked12 October 2026
- Approved outside the USEuropean Union, Canada, Israel: Health Canada approved it on 11 October 2024 for Rett syndrome from age 2. The EU authorised it as Daybu on 20 August 2026 for neurobehavioural symptoms of Rett syndrome from age 5, after an initial refusal. Acadia reports approval in Israel in December 2025. Also approved in the US.This does not change the United States position above.
- DoseFrom the drug label. The manufacturer tested this range and a regulator reviewed it.
- Vial sizeFrom what vendors typically list; not a recommendation.
- SourcesDaybue prescribing information (DailyMed, revised 3/2026)Drugs@FDA, NDA 217026Neul JL et al., Nature Medicine 2023;29:1468-1475 (LAVENDER)ClinicalTrials.gov, LAVENDER posted results (NCT04181723)EMA, Daybu EPAREMA, questions and answers on the initial refusal of DaybuHealth Canada, summary basis of decisionBerry-Kravis E et al., Pediatric Neurology 2020;110:30-41FDA GSRS substance record, trofinetide (UNII Z2ME8F52QL)
What has happened recently
FDA-approved on 10 March 2023 (NDA 217026, Daybue oral solution) for Rett syndrome in adults and children aged 2 and over, with priority review, orphan status and a rare pediatric disease voucher later sold for $150 million. A powder form, Daybue Stix, was approved on 11 December 2025. Health Canada approved it in October 2024. In the EU the CHMP refused it in February 2026, judging the 12-week effects too small to be clinically meaningful, then recommended it on re-examination for neurobehavioural symptoms from age 5; authorisation as Daybu followed on 20 August 2026. Acadia holds worldwide rights from Neuren.
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What else is like Trofinetide (Daybue)?
Others in Brain, mood and sleep, side by side.If you're weighing Trofinetide (Daybue), it's worth reading Ziconotide, Selank, and Semax in the same class.
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Guides for this compound
- mcg vs mg: The Peptide Dosing Mistake to Avoid
Your vial says mg and your protocol says mcg. Here is the conversion and how to check it.
Sources
- Daybue prescribing information (DailyMed, revised 3/2026)(2026)Indication from age 2; mechanism unknown; weight-band dosing; LAVENDER RSBQ -4.9 against -1.7 (p=0.018) and CGI-I 3.5 against 3.8 (p=0.003); diarrhoea 82% against 20%; half-life about 1.5 hours; about 80% excreted unchanged in urine.
- Drugs@FDA, NDA 217026(2026)Approved 10 March 2023; type 1 new molecular entity, priority review, orphan. Paediatric labelling supplement approved 27 March 2026.
- Neul JL et al., Nature Medicine 2023;29:1468-1475 (LAVENDER)(2023)187 girls and women aged 5 to 20, 12 weeks: co-primary endpoints met (P=0.0175 and P=0.0030); diarrhoea 80.6% against 19.1%.
- ClinicalTrials.gov, LAVENDER posted results (NCT04181723)(2022)70 of 93 on trofinetide and 85 of 94 on placebo completed; serious adverse events 3 in each arm.
- EMA, Daybu EPAR(2026)Authorised 20 August 2026 for neurobehavioural symptoms of Rett syndrome in patients aged 5 and over, after an initial negative opinion on 26 February 2026 and a positive re-examination.
- EMA, questions and answers on the initial refusal of Daybu(2026)The 12-week effects were judged too small to be clinically meaningful; key symptoms were not assessed; withdrawals clouded long-term efficacy.
- Health Canada, summary basis of decision(2024)Approved 11 October 2024 for Rett syndrome from age 2 and at least 9 kg. Benefit described as modest, with high discontinuation and unblinding from diarrhoea.
- Berry-Kravis E et al., Pediatric Neurology 2020;110:30-41(2020)Fragile X phase 2, 72 males aged 12 to 45, 28 days: 70 mg/kg twice daily met prespecified efficacy criteria.
- FDA GSRS substance record, trofinetide (UNII Z2ME8F52QL)(2026)Glycyl-2-methyl-L-prolyl-L-glutamic acid, C13H21N3O6, registered as a chemical. Codes NNZ-2566 and ACP-2566.
Beyond these, 106 records are indexed. Browse the records