Short answer: Both are once-weekly growth hormone injections for children and adults with growth hormone deficiency.12 Skytrofa (lonapegsomatropin) starts at age 1 and 11.5 kg and uses cartridges mixed in its own auto-injector. Sogroya (somapacitan) starts at 2.5 years, comes in prefilled pens and also covers three other causes of short stature. Neither has a boxed warning or reports a trial against the other.
| Skytrofa | Sogroya | |
|---|---|---|
| Drug | Lonapegsomatropin-tcgd1 | Somapacitan-beco2 |
| Children | Age 1 and older, at least 11.5 kg, with growth hormone deficiency1 | Age 2.5 and older with growth hormone deficiency, born small for gestational age, Noonan syndrome or idiopathic short stature2 |
| Child dose | 0.24 mg/kg a week, with the cartridge picked from a weight table1 | 0.16 mg/kg a week for growth hormone deficiency; 0.24 mg/kg for the other uses2 |
| Adult dose | Start 0.7, 1.4 or 2.1 mg a week by age and oral estrogen use; up to 6.3 mg1 | Start 1.5 mg a week (1 mg over 65, 2 mg on oral estrogen); up to 8 mg2 |
| Device | Powder cartridge mixed and injected by the Skytrofa Auto-Injector1 | Three strengths of prefilled pen2 |
| Missed dose | Within 2 days of the missed day; doses at least 5 days apart1 | Within 3 days after the scheduled day2 |
| Adult trial vs placebo | Swelling (edema) 8% vs 1%1 | Back pain 10% vs 3.3%, joint pain 6.7% vs 1.6%2 |
| Boxed warning | None1 | None2 |
Both labels compare the weekly drug with daily somatropin over 52 weeks in children with growth hormone deficiency who had not been treated before. On Skytrofa, viral infection was 15% vs 11% and fever 15% vs 9%.1 On Sogroya, headache was 12.1% vs 8.8% and pain in the arms or legs 9.8% vs 2.9%.2 These numbers come from separate trials with different people, lengths and methods, so they are not a head-to-head comparison.
From daily somatropin, Skytrofa starts at least 8 hours after the last daily dose; from another weekly growth hormone, at least 7 days after its last dose.1 Children on Sogroya take the last daily dose the day before, or at least 8 hours before, the first weekly dose, and children coming from another weekly product keep the weekly schedule.2 Both labels carry the growth hormone class warnings, including critical illness, tumors, blood sugar, raised pressure in the skull, hip problems in children and pancreatitis, and neither is approved for Prader-Willi syndrome growth failure.12
Which, if either, fits is for your prescriber. More detail: Skytrofa side effects, Sogroya side effects, the Skytrofa and Sogroya dosing schedules, the Skytrofa and Sogroya missed-dose pages, and Sogroya vs daily growth hormone: what changes with a weekly shot?.