Short answer: Lonapegsomatropin has a half-life of about 30.7 hours (released growth hormone about 25 hours). Levels peak median 25 hours in children (31 hours in adults) after a dose. People vary, so treat these as estimates.
Lonapegsomatropin is a long-acting prodrug of growth hormone. Human growth hormone is attached to a carrier through a link that breaks down slowly in the body, releasing unchanged growth hormone over the week. It is sold as Skytrofa (Ascendis Pharma), injected under the skin once a week.
Also known as: Skytrofa, lonapegsomatropin-tcgd.
Skytrofa comes as single-dose, two-chamber cartridges (powder in one chamber, water in the other) in 0.7, 1.4, 1.8, 2.1, 2.5, 3, 3.6, 4.3, 5.2, 6.3, 7.6, 9.1, 11 and 13.3 mg. Each cartridge works only with the Skytrofa Auto-Injector, which mixes the powder and gives the dose. A refrigerated cartridge sits at room temperature for 15 minutes first, and a mixed cartridge is used within 4 hours.
The Skytrofa label approves lonapegsomatropin for children 1 year and older who weigh at least 11.5 kg and have growth failure from growth hormone deficiency, and to replace growth hormone in adults with growth hormone deficiency. Label dosing: children take 0.24 mg/kg once a week, with the cartridge picked from a weight table (two cartridges above 60.5 kg). Adults start at 1.4 mg once a week (ages 30 to 60), 2.1 mg (under 30, or any age on oral estrogen) or 0.7 mg (over 60), raised monthly up to 6.3 mg. It is injected into the belly, buttock or thigh. A dose can be given up to 2 days before or after the usual day, with at least 5 days between doses.
The label has no boxed warning. Its warnings, shared with daily growth hormone, cover higher death rates when started during acute critical illness (where it is not used), severe allergic reactions, growth of existing tumors and second tumors in childhood cancer survivors, higher blood sugar, raised pressure in the skull, fluid retention, low cortisol and thyroid changes, hip problems and scoliosis in children, pancreatitis, fat changes at injection sites, and sudden death in children with Prader-Willi syndrome. An eye exam is done before starting. In the pediatric trial against daily somatropin, side effects included viral infection (15% vs 11%) and fever (15% vs 9%); in adults, swelling was 8% vs 1% on placebo. Full numbers are on the Skytrofa side effects, Skytrofa dosing schedule, missed Skytrofa dose and Skytrofa storage pages, and Skytrofa vs Sogroya compares the two.
The Skytrofa label gives a mean half-life of 30.7 hours for lonapegsomatropin in children with growth hormone deficiency, and about 25 hours for the growth hormone it releases. Peak levels of lonapegsomatropin came a median 25 hours after a dose in children and 31 hours in adults; the released growth hormone peaked at 12 hours in children and 13 hours in adults.
Numbers shown are taken from the source above. Half-life varies from person to person.
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