Approved & therapeutic
Lonapegsomatropin
Skytrofa
Lonapegsomatropin is a once-weekly prodrug of somatropin that releases unmodified human growth hormone over the dosing interval. It is FDA approved for pediatric growth hormone deficiency and, since July 2025, for growth hormone deficiency in adults.
- Status
- Lonapegsomatropin is approved by the U.S. FDA and has official prescribing information.
- Evidence
- Approved labeling. Official prescribing information exists, based on clinical trials in people.
- Half-life
- The somatropin released from the prodrug has an apparent half-life of approximately 25 hours, which supports once-weekly administration; the intact conjugate has an observed half-life of approximately 30.7 hours. The label reports these separately.
- How it's taken
- Subcutaneous injection
- Mechanism
- Anabolic (IGF-1 / myostatin)
- Pathways
- GH axis, IGF-1
How Lonapegsomatropin works
The molecule consists of somatropin bound through a TransCon linker to a methoxy polyethylene glycol carrier. The linker hydrolyses at physiological pH and temperature, releasing unmodified somatropin, which then acts on the growth hormone receptor to stimulate chondrocyte differentiation, protein synthesis, lipolysis and hepatic glucose output, with indirect effects mediated by insulin-like growth factor 1.
What research has looked at
- In the phase 3 heiGHt trial in treatment-naive children with growth hormone deficiency, annualised height velocity at 52 weeks met the primary non-inferiority objective against daily somatropin and additionally reached statistical significance in favour of lonapegsomatropin (11.2 versus 10.3 cm per year, p=0.009).
- In the phase 3 foresiGHt trial in adults with growth hormone deficiency, the primary endpoint of change in trunk percent fat at week 38 was significantly reduced compared with placebo (least squares mean difference -2.04 percent, p<0.001), the basis of the adult approval. No formal statistical comparison was made against the open-label daily somatropin arm.
- Raises insulin-like growth factor 1 concentrations in people with growth hormone deficiency.
- Delivers unmodified somatropin on a weekly schedule, reducing injection frequency relative to daily growth hormone.
Evidence level: Approved labeling. Official prescribing information exists, based on clinical trials in people. These are areas studied or reported, not promised effects.
Reported side effects and risks
- Contraindicated in acute critical illness after open heart surgery, abdominal surgery or multiple accidental trauma, or in acute respiratory failure, because of increased mortality.
- Contraindicated in anyone with known hypersensitivity to somatropin or to any excipient in the product; severe systemic hypersensitivity reactions, including anaphylaxis and angioedema, have been reported with somatropin products including this one.
- Contraindicated in active malignancy, in active proliferative or severe non-proliferative diabetic retinopathy, in children with closed epiphyses, and in children with Prader-Willi syndrome who are severely obese, have a history of upper airway obstruction or sleep apnea, or have severe respiratory impairment, where sudden death has been reported.
- Glucose intolerance and diabetes mellitus may be unmasked; intracranial hypertension (exclude preexisting papilledema before starting) and fluid retention, including edema, arthralgia and carpal tunnel syndrome, may occur.
- Hypoadrenalism, hypothyroidism, pancreatitis, and an increased risk of neoplasms, including a second neoplasm in childhood cancer survivors treated with cranial radiation.
- Slipped capital femoral epiphysis and progression of preexisting scoliosis in children; lipoatrophy at injection sites. Commonly reported reactions in children include viral infection, pyrexia, cough, nausea and vomiting, hemorrhage, diarrhea, abdominal pain, and arthralgia and arthritis; peripheral edema was the most common reaction in adults. There is no boxed warning on the US label.
Sources
- PubMed research on Lonapegsomatropin · NIH · National Library of Medicine
- DrugBank record for Lonapegsomatropin · DrugBank
- Active clinical trials for Lonapegsomatropin · U.S. National Library of Medicine
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Lonapegsomatropin FAQ
What is Lonapegsomatropin?
Lonapegsomatropin is a once-weekly prodrug of somatropin that releases unmodified human growth hormone over the dosing interval. It is FDA approved for pediatric growth hormone deficiency and, since July 2025, for growth hormone deficiency in adults.
How does Lonapegsomatropin work?
The molecule consists of somatropin bound through a TransCon linker to a methoxy polyethylene glycol carrier. The linker hydrolyses at physiological pH and temperature, releasing unmodified somatropin, which then acts on the growth hormone receptor to stimulate chondrocyte differentiation, protein synthesis, lipolysis and hepatic glucose output, with indirect effects mediated by insulin-like growth factor 1.
Is Lonapegsomatropin FDA approved?
Yes. Lonapegsomatropin is approved by the U.S. FDA and has official prescribing information. Evidence level: approved labeling. Official prescribing information exists, based on clinical trials in people.
What is the half-life of Lonapegsomatropin?
Reported half-life: The somatropin released from the prodrug has an apparent half-life of approximately 25 hours, which supports once-weekly administration; the intact conjugate has an observed half-life of approximately 30.7 hours. The label reports these separately.
How is Lonapegsomatropin taken?
Subcutaneous injection.
What side effects have been reported with Lonapegsomatropin?
Reported in the sources: Contraindicated in acute critical illness after open heart surgery, abdominal surgery or multiple accidental trauma, or in acute respiratory failure, because of increased mortality; Contraindicated in anyone with known hypersensitivity to somatropin or to any excipient in the product; severe systemic hypersensitivity reactions, including anaphylaxis and angioedema, have been reported with somatropin products including this one; Contraindicated in active malignancy, in active proliferative or severe non-proliferative diabetic retinopathy, in children with closed epiphyses, and in children with Prader-Willi syndrome who are severely obese, have a history of upper airway obstruction or sleep apnea, or have severe respiratory impairment, where sudden death has been reported; Glucose intolerance and diabetes mellitus may be unmasked; intracranial hypertension (exclude preexisting papilledema before starting) and fluid retention, including edema, arthralgia and carpal tunnel syndrome, may occur; Hypoadrenalism, hypothyroidism, pancreatitis, and an increased risk of neoplasms, including a second neoplasm in childhood cancer survivors treated with cranial radiation; Slipped capital femoral epiphysis and progression of preexisting scoliosis in children; lipoatrophy at injection sites. Commonly reported reactions in children include viral infection, pyrexia, cough, nausea and vomiting, hemorrhage, diarrhea, abdominal pain, and arthralgia and arthritis; peripheral edema was the most common reaction in adults. There is no boxed warning on the US label.
Educational summary compiled from the sources listed above. Not medical advice. Peptide Vault does not sell, source or recommend any compound. Talk to a qualified clinician before starting or changing anything.