medwireNews: The long-acting recombinant human growth hormone (rhGH) fusion protein somavaratan boosts growth velocity in children even when given as infrequently as once a month, study findings suggest.
Somavaratan consists of rhGH attached to sequences of hydrophilic amino acids, the overall effect of which is to reduce the speed at which it is cleared from the body via the kidneys. In adults, it has a half-life of 130 hours.
The current phase Ib/IIa study involved a dose-escalation phase and a 6-month randomised, open-label phase. The dose-escalation phase showed that somavaratan remained measureable in the plasma of the 48 participating children for up to 1 month.
As with other types of long-acting GH, somavaratan was developed “with the anticipation that a reduced burden of dosing schedules might alleviate challenges of treatment adherence with daily rhGH and avoid the diminished efficacy associated with decreased adherence”, say George Bright (Versartis Inc., Menlo Park, California, USA) and study co-authors.
The randomised phase included 44 of the patients from the dose-escalation phase plus an additional 20 patients, all of whom had GH deficiency (peak GH <10 ng/ml). The patients received a total of 30 mg/kg somavaratan over 6 months, given as 1.15 mg/kg per week, 2.5 mg/kg twice monthly or 5.0 mg/kg once a month.
The patients were aged about 8 years old at baseline and had a height standard deviation score (SDS) of –2.0 or below. Before treatment the average growth velocity was 4.52 cm/year in 38 patients for whom the information was available.
During treatment, however, growth velocity markedly improved, to 7.86 cm/year among patients receiving monthly treatment, 8.61 cm/year among those receiving it twice monthly and 7.58 cm/year among those receiving weekly treatment. There were no significant differences in on-treatment height velocity between the groups.
The corresponding 6-month improvements in height SDS were 0.28, 0.33 and 0.24, again with no differences between the groups, the team reports in The Journal of Clinical Endocrinology & Metabolism.
Safety was as anticipated for GH-deficient children receiving rhGH. Injection site pain was the most common reaction, but was mild and lasted less than 30 minutes. Anti-somavaratan antibodies did not appear to affect height velocity in the patients who developed them.
By Eleanor McDermid, Senior medwireNews Reporter
J Clin Endocrinol Metab 2016; Advance online publication
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