For many girls with Turner syndrome, growth hormone is not a short course of treatment but a routine repeated every night for years. The daily injection works, but it takes a toll: it hurts, it interrupts sleep, it depends on an adult being available and, over time, it invites missed doses. That is why longer-acting versions that cut the number of injections without losing effectiveness are of real interest. The question now has an answer: can a single weekly injection keep up the same pace of growth as the classic schedule?
The answer comes from the REAL8 trial (NCT05330325), a randomised, open-label, active-comparator phase 3 study run at 49 clinics in 18 countries. It enrolled 105 prepubertal girls with Turner syndrome who had not been treated with growth hormone before and were aged between 2.5 and 10 years. Two out of three were assigned to weekly somapacitan at 0.24 mg per kilogram of body weight, and one in three to conventional daily growth hormone at 0.050 mg per kilogram per day. Both were given subcutaneously, and the main follow-up ran for 52 weeks, with a subsequent 104-week extension phase.
The primary endpoint was height velocity after one year of treatment. The results confirmed that the weekly schedule was non-inferior: girls treated with somapacitan grew a mean of 9.0 centimetres per year, compared with 9.5 centimetres per year on the daily injection. The estimated difference was -0.8 centimetres per year, with a 95% confidence interval that stayed within the pre-specified non-inferiority margin. In other words, the growth rate of the two schedules is comparable from both a statistical and a clinical point of view.
The second relevant piece of data is insulin-like growth factor I (IGF-I), the marker monitored to check that the dose is not excessive. Its standard deviation score rose in both groups: +1.71 with somapacitan and +1.95 with daily growth hormone at 52 weeks, values in the same range and with no sign of overexposure to treatment. The safety profile was similar in both arms, and no participant discontinued the trial product because of adverse events, no small detail for a treatment measured in years rather than weeks.
These results deserve a cautious reading. The study was open-label, meaning neither families nor investigators were blinded to which schedule each girl received, and the main follow-up covers only one year, far too short to know whether the difference translates into final adult height. Nor does it answer whether the convenience of a weekly injection genuinely improves long-term adherence, which is the practical reason this type of formulation attracts interest. The 104-week extension and longer follow-up studies will be the ones to clarify the impact on adult stature.
Even so, the central message is clear: cutting seven weekly injections down to one does not compromise short-term growth in previously untreated girls with Turner syndrome. For families, that may mean fewer difficult nights and fewer disruptions to school and social life; for paediatric endocrinology services, a different conversation about how to organise a treatment that, in Turner syndrome, often begins in childhood and accompanies the patient through much of her development.
Source: Once-weekly somapacitan enhances linear growth in girls with Turner syndrome: a randomized controlled phase 3 study. Mauras N, Boettcher C, Højby M, Soltysik K, Jorge AAL, Kashimada K, Linglart A, Luo X, Murray PG, Backeljauw P. J Clin Endocrinol Metab 2026;dgag309. DOI: 10.1210/clinem/dgag309.
Read the publication: https://doi.org/10.1210/clinem/dgag309 · PubMed 42538806
