The human growth hormone formulation somapacitan for adults with growth hormone deficiency was approved by the Food and Drug Administration on Sept. 1. .
Somapacitan contains an albumin-binding element attached to the growth hormone, causing the reversible binding to albumin proteins in the body. This reduces clearance and increases the half-life of the hormone. The formulation has previous demonstrated safety and efficacy in children with growth hormone deficiency (J Clin Endocrinol Metab. 2020 Apr 1. doi: 10.1210/clinem/dgz310).
Growth hormone treatment can counter abdominal obesity, reduced lean body mass, fatigue, osteopenia, cardiovascular risks, and other manifestations of growth hormone deficiency in adults, but daily injections can be burdensome for patients. That makes long-acting versions attractive, but the lifelong nature of the treatment makes it important to characterize safety and tolerability.
The approval comes on the strength of a randomized, placebo-controlled phase 3 trial (REAL 1) of 300 adult patients in 17 countries with growth hormone deficiency (J Clin Endocrinol Metab. 2020 Apr 1. doi: 10.1210/clinem/dgaa049). Participants had either never received growth hormone treatment, or had stopped taking one at least 6 months before starting the trial. Subjects received once-weekly somapacitan, once-weekly placebo, or daily somatropin, which is FDA approved.
The primary endpoint was percentage change of truncal fat, which is regulated by growth hormone, and can lead to medical problems. After 34 weeks, subjects in the somapacitan group experienced a 1.06% decrease in truncal fat, compared with a 0.47% increase in the placebo group (P = .009) and a 2.23% decrease in the daily somatropin group.
After 34 weeks, a 52-week extension trial began. The somapacitan group continued on the drug and the placebo group was offered somapacitan. Patients on daily somatropin were randomized to continue daily treatment with somatropin or to switch to somapacitan.
At the end of the extension trial, those taking somapacitan for the full 86-week duration had an average reduction of 1.52% in truncal fat. After 86 weeks, the somapacitan and daily somatropin groups had similar values for percentage change in visceral fat, lean body mass, or appendicular skeletal muscle mass.
Common side effects of somapacitan were back pain, joint paint, indigestion, a sleep disorder, dizziness, tonsillitis, swelling in the arms or lower legs, vomiting, adrenal insufficiency, hypertension, increase in blood creatine phosphokinase, weight increase, and anemia.
Somapacitan, marketed as Sogroya by Novo Nordisk, is contraindicated in patients with an allergy to the drug, as well as those with an active malignancy, diabetic eye disease where increases in blood sugars could lead to retinal damage, acute critical illness, or acute respiratory failure.
The FDA recommends that providers perform an eye examination before drug initiation, as well as periodically while the patient is taking the drug, to rule out preexisting papilledema. This could be a sign of intracranial hypertension, which could be caused or worsened by growth hormones.