Somapacitan
Growth hormone made to last a week by binding albumin, for adults and children
Somapacitan is human growth hormone with one amino acid changed and a fatty side chain attached, so it binds albumin and lasts long enough for a weekly injection. Approved as Sogroya for adults with growth hormone deficiency in 2020 and children in 2023, its label added three more childhood growth conditions in 2026.
What is it?
Daily growth hormone means about 365 injections a year; somapacitan cuts that to 52. It is human growth hormone with one amino acid changed (L101C) so that a fatty side chain can be attached; the chain binds albumin, which shields the molecule from clearance. The label gives a half-life of about 2 to 3 days in adults and about 34 hours in children at the paediatric dose.
The dose was set in children. A phase 2 trial of 59 children compared weekly 0.04, 0.08 and 0.16 mg/kg with daily growth hormone; only the highest dose matched daily treatment (12.9 against 11.4 cm a year at 26 weeks), and 0.16 mg/kg became the label dose. In REAL 4, children with growth hormone deficiency then grew 11.2 cm a year on it against 11.7 on daily somatropin, within the non-inferiority margin.
The long-term picture in children comes from REAL 3, whose final seven-year report found height scores approaching the population average and no new safety concern, with three serious adverse events judged possibly or probably related.
In February 2026 the label extended to children born small for gestational age, with Noonan syndrome or with idiopathic short stature, at a higher weekly dose of 0.24 mg/kg. The trials behind it each ran 52 weeks against daily growth hormone: children born small grew 11.0 cm a year on somapacitan, it matched daily treatment in idiopathic short stature, and in Noonan syndrome it did better (10.4 against 9.2 cm a year). A trial in Turner syndrome also met non-inferiority, but Turner syndrome is not on the US label.
In adults the measure is body composition, not height. In REAL 1, 301 adults with untreated growth hormone deficiency saw truncal fat fall by 1.53 percentage points against placebo over 34 weeks, with gains in lean mass and IGF-I. Adults switched from daily injections kept IGF-I in range and rated the weekly schedule as more convenient. The adult dose starts at 1.5 mg a week and is titrated to IGF-I.
Its warnings are those of growth hormone itself: intracranial hypertension, fluid retention, glucose intolerance and diabetes, and in children slipped capital femoral epiphysis and worsening scoliosis. It is contraindicated in acute critical illness, active cancer and diabetic eye disease, and in children with Prader-Willi syndrome who are severely obese or have severe breathing problems.
Two other weekly growth hormones are approved, somatrogon and lonapegsomatropin, each lengthening the hormone's life by a different route; each has its own page.
Mechanism of Action
Somapacitan acts as growth hormone does; what differs is how long it stays in the blood.
Growth hormone receptor
Binds the GH receptor like somatropin, triggering JAK2/STAT5 signalling and IGF-I production (dataset mechanism).
Albumin binding
A fatty side chain attached at position 101 binds albumin reversibly, slowing kidney and receptor-mediated clearance (dataset mechanism).
Weekly profile
Half-life about 2 to 3 days in adults and about 34 hours in children at 0.16 mg/kg (Sogroya label 12.3).
Published Research
The trials behind somapacitan, read from their PubMed abstracts: the paediatric dose-finding and REAL 4 trials with REAL 3's seven-year results, the 2026 trials in children born small, with Noonan syndrome, idiopathic short stature and Turner syndrome, and the adult trials. Dosing from the Sogroya label read October 1, 2026.
REAL 4: children with GHD
Children randomised 2:1 to somapacitan 0.16 mg/kg weekly or daily somatropin grew 11.2 and 11.7 cm a year at week 52, meeting the non-inferiority margin, with similar IGF-I and safety.
REAL 3: seven years in children
In the phase 2 REAL 3 trial of children with growth hormone deficiency, 43 of the main cohort (73%) completed seven years; height standard deviation scores approached 0 by week 364, three serious adverse events were judged possibly or probably related, and no new safety concern emerged.
Finding the dose
In 59 children, weekly 0.04, 0.08 and 0.16 mg/kg gave height velocities of 8.0, 10.9 and 12.9 cm a year at 26 weeks against 11.4 on daily growth hormone, which set 0.16 mg/kg.
Born small for gestational age
In 142 prepubertal children randomised to somapacitan 0.24 mg/kg weekly or one of two daily growth hormone doses, height velocity at 52 weeks was 11.0 cm a year on somapacitan.
Noonan syndrome
In treatment-naive children with Noonan syndrome, weekly somapacitan gave a height velocity of 10.4 cm a year at 52 weeks against 9.2 cm on daily growth hormone, meeting non-inferiority and then superiority (difference 1.2 cm a year), with a similar safety profile.
Idiopathic short stature
In treatment-naive children with idiopathic short stature, height velocity at 52 weeks was 10.2 cm a year on weekly somapacitan and 10.6 cm on daily growth hormone, within the non-inferiority margin; adverse events affected 79.7% and 78.6%, mostly mild.
Turner syndrome: not on the label
In treatment-naive girls with Turner syndrome, height velocity at 52 weeks was 9.0 cm a year on weekly somapacitan and 9.5 cm on daily growth hormone, meeting non-inferiority, with IGF-I in a similar range and similar safety. Turner syndrome is not among the US label's indications.
REAL 1: adults with GHD
In 301 untreated adults, 34 weeks of weekly somapacitan cut truncal fat by 1.53 percentage points against placebo and improved visceral fat, lean mass and IGF-I.
Switching adults from daily GH
In 92 adults switched from daily growth hormone, weekly somapacitan kept IGF-I in range for 26 weeks with mostly mild adverse events, no antibodies and no clinically significant reactions over 1,500 injections, and scored higher for convenience.
Dosing Data
Dosed by label, once weekly at any time of day, adjusted to growth response in children and to IGF-I in adults.
Educational information, not medical advice. Each dose above is tagged with its source: an approved label, a published human study, animal data, or amounts reported by users. None is a recommendation for you. An unapproved compound has no established safe or effective human dose, and products sold for “research use only” are not made or tested for people. Talk to a doctor before acting on anything on this site, including before you start, stop or change any medicine or dose. Full medical disclaimer.
Side Effects & Contraindications
Reported Side Effects
Warnings from the Sogroya label (version 8).
Contraindications & Cautions
From the label.
Legal Status
Approved in the US for adults and four childhood conditions.
Frequently Asked Questions
?How does it last a week?
Its attached fatty side chain binds albumin, which slows its clearance: the label gives a half-life of about 2 to 3 days in adults.
?Is it the same as somatropin?
It is a modified somatropin: one amino acid is changed so the albumin-binding chain can be attached.
?How does it compare with other weekly GH drugs?
Somatrogon and lonapegsomatropin also allow weekly dosing; this page covers somapacitan's own trials.
?Which children is it approved for?
In the US: growth hormone deficiency (from 2023) and, from February 2026, children born small for gestational age, with Noonan syndrome or with idiopathic short stature.
?Is it approved for Turner syndrome?
Not in the US. A 2026 trial found it matched daily growth hormone in girls with Turner syndrome, but the label does not include it.
?Does it work as well as daily injections?
In the 52-week trials it matched daily growth hormone in growth hormone deficiency and idiopathic short stature, and grew children with Noonan syndrome faster.
?What is known long term?
REAL 3 followed children with growth hormone deficiency for seven years: height scores approached average and no new safety concern appeared.
?How is the adult dose set?
The label starts adults at 1.5 mg a week and adjusts the dose by IGF-I levels.
References
- [fda-pi] Sogroya (somapacitan-beco) injection US prescribing information (DailyMed version 8, effective February 25, 2026); read October 1, 2026.
- [clinical-trial] Miller BS, et al. "Weekly Somapacitan is Effective and Well Tolerated in Children With GH Deficiency: The Randomized Phase 3 REAL4 Trial." J Clin Endocrinol Metab, 2022;107(12):3378-3388. PMID: 36062966.
- [clinical-trial] Sävendahl L, et al. "Once-Weekly Somapacitan vs Daily GH in Children With GH Deficiency: Results From a Randomized Phase 2 Trial." J Clin Endocrinol Metab, 2020;105(4):e1847-61. PMID: 31917835.
- [clinical-trial] Johannsson G, et al. "Once-weekly Somapacitan is Effective and Well Tolerated in Adults with GH Deficiency: A Randomized Phase 3 Trial." J Clin Endocrinol Metab, 2020;105(4):e1358-76. PMID: 32022863.
- [clinical-trial] Linglart A, et al. "Somapacitan in children born small for gestational age: a randomized controlled phase 3 trial." Eur J Endocrinol, 2026;194(3):311-325. PMID: 41782416.
- [clinical-trial] Johannsson G, et al. "Safety and convenience of once-weekly somapacitan in adult GH deficiency: a 26-week randomized, controlled trial." Eur J Endocrinol, 2018;178(5):491-499. PMID: 29500310.
- [clinical-trial] Jorge AAL, et al. "Once-weekly somapacitan in children with Noonan syndrome: randomized controlled phase 3 trial." Eur J Endocrinol, 2026;194(3):393-403. PMID: 41774755.
- [clinical-trial] Abuzzahab J, et al. "Somapacitan in children with idiopathic short stature: a randomized controlled phase 3 study." Eur J Endocrinol, 2026;194(2):242-253. PMID: 41712606.
- [clinical-trial] Mauras N, et al. "Once-weekly somapacitan enhances linear growth in girls with Turner syndrome: a randomized controlled phase 3 study." J Clin Endocrinol Metab, 2026. PMID: 42538806.
- [clinical-trial] Sävendahl L, et al. "Seven-year Safety and Efficacy of Somapacitan in Children With GH Deficiency: Final Results From REAL 3." J Endocr Soc, 2026;10(1):bvaf189. PMID: 41394116.
Sources & Citations
Dosing and warnings from the Sogroya label (DailyMed version 8, effective February 25, 2026, read October 1, 2026); approvals from Drugs@FDA; studies from PubMed abstracts.
Medical Disclaimer: This content is for educational and informational purposes only. It is not medical advice, and nothing here is an instruction to obtain or use any compound. Talk to a licensed clinician about your own situation.