Somapacitan

Origin and structure

Somapacitan was developed by Novo Nordisk, which also makes the daily growth hormone Norditropin, under the code NNC0195-0092; the first trial in healthy volunteers started in 2012. The aim was to replace daily growth hormone injections, which children with a deficiency often need for many years, with one injection a week.

The protein is human growth hormone, 191 amino acids made by bacteria (E. coli), with one change: the leucine at position 101 is replaced by a cysteine. To that cysteine a side chain is attached chemically: a fatty acid on a hydrophilic spacer, which binds reversibly to albumin, the main protein of blood plasma. The whole molecule weighs about 23.3 kDa, of which the side chain accounts for about 1.2 kDa. Novo Nordisk uses the same principle, letting a drug ride on albumin, in the insulin detemir (Levemir) and the GLP-1 medicines liraglutide (Victoza) and semaglutide (Ozempic).

Sogroya is a ready-to-use liquid in pre-filled pens of 5, 10 and 15 mg, kept in the fridge. In the US its official name is somapacitan-beco. Strictly speaking it is a growth hormone analogue, not somatropin, the name for growth hormone with exactly the natural sequence.

How it works

Somapacitan acts like the body's own growth hormone. It activates the growth hormone receptor, and much of its effect runs through IGF-1, which tissues, above all the liver, produce in response. In children it drives growth at the growth plates of the bones; in adults with a deficiency it lowers fat mass and raises lean mass. The albumin binding changes how long the molecule lasts, not where it acts: it slows its removal from the blood, which stretches the effect of one injection to a week.

More than 99% of somapacitan in the blood is bound to protein. Its half-life is about 2 to 3 days at steady state in adults and children with a deficiency, and about 34 hours at the standard children's dose; it stays in the circulation for about two weeks after the last injection. IGF-1 peaks 2 to 4 days after each injection and falls again before the next, a swing within the week that daily injections do not produce, and a steady weekly pattern is reached after one or two doses. That is why IGF-1 is measured on a fixed day, 3 to 4 days after the injection.

The body breaks somapacitan down completely. In a small study in Groningen, seven healthy men received radiolabelled somapacitan: no intact drug turned up in urine or faeces, and 81% of the radioactivity left the body in urine and 13% in faeces. Oral oestrogen, as in the contraceptive pill, blunts the response: at the same dose, exposure was 53% lower in women taking it than in men, and women may need higher doses and a longer period of dose adjustment.

Is somapacitan approved?

Yes. Sogroya is a prescription medicine in the EU, and therefore in the Netherlands, and in the US. Treatment is started and monitored by doctors experienced in growth hormone deficiency, such as endocrinologists and paediatric endocrinologists.

In the Netherlands Sogroya is listed in the Farmacotherapeutisch Kompas but, like the daily growth hormones, it is not in the pharmacy reimbursement system (GVS). Growth hormones have been paid for as specialist medical care through the hospital since 2013, and the Dutch horizon scan for medicines places Sogroya in that budget for specialist care (MSZ).

• EU: authorised on 31 March 2021 for adults with growth hormone deficiency, and on 24 July 2023 also for children from 3 years and adolescents with growth failure due to a deficiency. It carries the black triangle for additional monitoring, its licence was renewed without time limit in November 2025, and in September 2026, at Novo Nordisk's request, it was withdrawn from the EU register of orphan medicines; it had been designated an orphan medicine in 2018.
• EU, new uses in children: in May 2026 the EMA's CHMP recommended adding short children born small for gestational age (SGA) without catch-up growth and children with Noonan syndrome. On 17 September 2026, after re-examining that opinion, it also recommended children with idiopathic short stature (ISS), short stature without a known cause. The European Commission had not yet decided when this page was checked. Turner syndrome is not among the recommended uses.
• US: approved on 28 August 2020 for adults with growth hormone deficiency, on 28 April 2023 for children from 2.5 years with growth failure due to a deficiency, and on 27 February 2026 for children from 2.5 years who were born SGA without catch-up growth by age 2, or who have Noonan syndrome or ISS.

What the research shows

The evidence comes from Novo Nordisk's REAL programme. In adults the main trial was double-blind against placebo, with an open-label daily growth hormone arm; the trials in children were open-label comparisons with daily injections, so families and doctors knew which treatment a child received. Growth was measured as height velocity, the centimetres gained per year. The EU product information notes that experience in adults over 60 and beyond five years of treatment is still limited, and long-term registries in children and adults are running. The main results:

• Adults, REAL 1 (J Clin Endocrinol Metab 2020): 300 previously untreated adults with growth hormone deficiency in 17 countries. After 34 weeks the share of fat around the trunk fell by 1.06 percentage points on weekly somapacitan and rose by 0.47 on placebo (difference −1.53, 95% CI −2.68 to −0.38). Daily somatropin lowered it more, by 2.23 points, while visceral fat and lean mass changed by similar amounts on both. The gains held through a 52-week extension. In a post hoc analysis the trunk-fat effect was clear in men but not statistically clear in women. After eight weeks of dose adjustment IGF-1 had reached the upper half of the normal range, the range today's label aims for, in 53% of participants, but in only 32% of women on oral oestrogen.
• Adults switching from daily injections: in two smaller trials, REAL 2 with 92 adults and a Japanese trial with 62, safety over 26 and 52 weeks was similar to daily growth hormone, and no antibodies against somapacitan were found in adults.
• Children with deficiency, REAL 4 (J Clin Endocrinol Metab 2022): 200 previously untreated children aged 2.5 to 11 in 20 countries grew 11.2 cm in the first year on weekly somapacitan against 11.7 cm on daily somatropin (difference −0.5 cm, 95% CI −1.1 to 0.2), which met the trial's test for being no worse. After three years 188 children were still taking part; in the third year they grew 7.4 cm on somapacitan throughout and 7.8 cm after switching from daily injections, and both groups were approaching the height expected from their parents.
• Long-term, REAL 3 (phase 2): 59 children started on one of three somapacitan doses or daily growth hormone, and all later moved to somapacitan. After seven years 43 of them were still in the trial, with heights close to the average for their age. Three serious adverse events were judged possibly or probably related to treatment, and no new safety concerns appeared.
• Born small for gestational age, REAL 8: 142 children grew 11.0 cm in a year on weekly somapacitan, against 9.4 cm on a lower and 11.1 cm on a higher daily dose of somatropin. That was 1.6 cm a year more than on the lower dose (95% CI 0.91 to 2.23) and about the same as on the higher dose (difference −0.1 cm, 95% CI −0.75 to 0.60).
• Noonan syndrome, REAL 8: 77 children grew 10.4 cm a year on somapacitan against 9.2 cm on daily somatropin (difference 1.2 cm, 95% CI 0.32 to 2.03). The daily dose used for comparison was lower than the highest dose licensed for Noonan syndrome in the US.
• Idiopathic short stature, REAL 8: 88 children grew 10.2 cm a year on somapacitan against 10.5 cm on daily somatropin (difference −0.3 cm, 95% CI −1.00 to 0.42), which met the test for being no worse.
• Turner syndrome, REAL 8 (J Clin Endocrinol Metab 2026): 105 girls aged 2.5 to 10 grew 9.0 cm a year on somapacitan against 9.5 cm on daily somatropin. Somapacitan met the test for being no worse, but the estimated difference of −0.8 cm a year (95% CI −1.57 to −0.11) favoured daily injections. Turner syndrome is not an approved use.

Somapacitan versus the other weekly growth hormones

Three weekly growth hormones are authorised in the EU, each built differently. Somapacitan rides on albumin. Somatrogon (Ngenla, Pfizer) is growth hormone fused to short pieces of another human hormone, chorionic gonadotropin (hCG). Lonapegsomatropin (Skytrofa, Ascendis Pharma) is ordinary somatropin attached to a carrier that releases it slowly after injection.

In the EU, Sogroya is the only one of the three authorised for adults; Ngenla and Skytrofa are licensed for children and adolescents with a deficiency from 3 years of age. In the US, Skytrofa is approved for adults as well. Each was tested against daily injections in children: Sogroya gave 11.2 cm a year against 11.7 cm in 200 children, Ngenla 10.1 cm against 9.8 cm in 224 children, and Skytrofa 11.2 cm against 10.3 cm in 161 children. The trials differed in design and population, so these figures cannot be set against one another.

Because head-to-head trials were lacking, Novo Nordisk researchers compared the three indirectly in 2024. They found no difference in growth over 52 weeks between them or against daily growth hormone, and more injection-site pain with somatrogon.

Side effects and warnings

In the trials the side effects matched those known for daily growth hormone. The most frequent was headache, in 12% of children and 12% of adults. Children also had pain in the arms or legs (9%), an underactive thyroid (5%) and injection-site reactions such as bruising or pain (5%); adults had joint pain (7%), fatigue (6%), swelling of the hands and feet (4%) and low adrenal function (3%). Raised blood sugar occurred in 1 to 2%. Most of these were mild and passed. Antibodies against somapacitan appeared in 16 of 132 children in REAL 4, none of them neutralising and without effect on growth.

The warnings are those of the growth hormone class. Growth hormone can unmask an underactive thyroid or adrenal glands and lowers insulin sensitivity, so the product information asks for checks of thyroid function, cortisol and blood sugar. It also warns about raised pressure inside the skull (benign intracranial hypertension), a slipped growth plate at the hip in fast-growing children, pancreatitis, and changes in the fat under the skin when the same injection site is used week after week. The US label adds severe allergic reactions, worsening scoliosis in children and sudden death in severely obese children with Prader-Willi syndrome, as warnings for all growth hormones.

Somapacitan must not be used when a tumour is active, in acute critical illness after open-heart or abdominal surgery, multiple trauma or acute respiratory failure, where high doses of daily growth hormone raised mortality from 19% to 42% in two placebo-controlled trials, or to promote growth once the growth plates have closed. In childhood cancer survivors, second tumours, mostly inside the skull, are slightly more common on growth hormone, with earlier radiation as the main risk factor. No carcinogenicity studies were done with somapacitan, and with no data in pregnancy it is not recommended then.

Frequently asked questions

Is Sogroya available in the Netherlands, and is it reimbursed?

Yes, on prescription. Sogroya has an EU licence that applies in the Netherlands and is listed in the Farmacotherapeutisch Kompas, for adults and for children from 3 years with growth hormone deficiency. It is not in the pharmacy reimbursement system (GVS), but neither are the daily growth hormones: since 2013 growth hormone in the Netherlands has been paid for as specialist medical care through the hospital, and the Dutch horizon scan for medicines places Sogroya in that budget.

What is the difference between Sogroya, Ngenla and Skytrofa?

All three are weekly growth hormones, built in different ways. Sogroya (somapacitan) binds to albumin in the blood, Ngenla (somatrogon) is growth hormone fused to pieces of hCG, and Skytrofa (lonapegsomatropin) releases ordinary somatropin slowly from a carrier. In the EU only Sogroya is licensed for adults; the other two are for children from 3 years. They have not been tested against each other in a randomised trial, and an indirect comparison found similar growth after a year.

Is somapacitan the same as HGH?

Not quite. It is human growth hormone with one amino acid changed and a fatty-acid side chain attached, which makes it an analogue rather than somatropin. It acts on the same receptor and has the same kinds of effects and side effects, but one injection lasts a week instead of a day, and its doses are set separately from those of daily somatropin.

How long does one injection of somapacitan last?

About a week. Its half-life is about 2 to 3 days in adults and children with a deficiency (about 34 hours at the standard children's dose), IGF-1 peaks 2 to 4 days after the injection, and the drug stays in the circulation for about two weeks after the last dose. Because IGF-1 rises and falls over the week, doctors measure it 3 to 4 days after an injection.

Is somapacitan banned in sport?

Yes, at all times, in and out of competition. The 2026 WADA Prohibited List names somapacitan, together with lonapegsomatropin and somatrogon, as a growth hormone analogue in class S2.2.3, and the Dutch anti-doping rules apply the same list. Athletes with a diagnosed growth hormone deficiency need a therapeutic use exemption before they can be treated with it.

Is Sogroya approved for short children without growth hormone deficiency?

In the US, yes, since February 2026: for children from 2.5 years who were born small for gestational age without catch-up growth, or who have Noonan syndrome or idiopathic short stature. In the EU the CHMP recommended the same three uses in 2026, idiopathic short stature only after a re-examination, but the European Commission had not yet decided when this page was checked. Novo Nordisk says Sogroya would be the first growth hormone licensed for idiopathic short stature in the EU. Turner syndrome has been studied but is not an approved use.

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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