medwireNews: Weekly injections of somatrogon result in similar height gains to daily somatropin treatment in children with growth hormone deficiency (GHD), show results of a 12-month phase 3 trial.
“Compared with somatropin administered once-daily, the less-frequent injection schedule afforded by somatrogon administered once-weekly has the potential to improve poor adherence and quality of life, which are key unmet needs in this pediatric population”, write the researchers in the Journal of Clinical Endocrinology & Metabolism.
At enrolment, the 224 trial participants were aged between 3 and 11 years if they were boys and between 3 and 10 years if they were girls and all had GHD confirmed with two different GH provocation tests.
The children all had impaired height, with an average height standard deviation score (SDS) of –2.86, and they had an annualized height velocity of –0.7 SDS or less. The majority were boys (71.9%) and White (74.6%).
After 12 months of treatment, the average annual height velocity was 10.10 cm/year for children randomly assigned to take somatrogon and 9.78 cm/year for those taking somatropin, making the weekly treatment statistically noninferior to standard daily treatment. The two treatments were equivalent irrespective of age, sex, or peak stimulated GH level.
Change in bone age was also similar between the treatment groups, report Bradley Miller (University of Minnesota Masonic Children’s Hospital, Minneapolis, USA) and study co-authors.
The average insulin-like growth factor (IGF)-1 SDS at baseline was –1.95 in the somatrogon group and –1.72 in the somatropin group, rising to 0.65 and “near zero”, respectively, at 12 months. Twenty-six patients in the somatrogon group and three in the somatropin group had levels that exceeded 2.0 SDS at some point in the study.
“Closer scrutiny of these 26 samples showed that 23 of them were obtained on day 2 or 3 after administration, which represents peak IGF-1 levels, not the mean, explaining the high IGF-1 levels”, say Miller et al.
They stress that interpreting IGF-1 levels in children taking long-acting GH is heavily dependent on the day of sample collection and that monitoring in clinical practice will require reference to pharmacokinetic/pharmacodynamics models for the specific product.
The most common adverse event was injection site pain, recorded in 39.4% and 25.2% of patients taking somatrogon and somatropin, respectively. The researchers say this imbalance did not relate to age or injection site, and they attribute it to the study protocol, which counted every high pain score for somatrogon but only the worst of the seven daily somatropin injections, even if multiple injections in a single week had a high pain score.
They also note that most instances of injection site pain occurred during the first 6 months of the study.
By Eleanor McDermid
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