SKYTROFA

Clinical safety rating: caution

Comprehensive clinical and safety monograph for SKYTROFA (SKYTROFA).

How it works

Recombinant human growth hormone that binds to growth hormone receptors, activating intracellular signaling pathways including JAK2/STAT5, leading to increased synthesis of insulin-like growth factor 1 (IGF-1) and subsequent anabolic and growth-promoting effects.

What the body does with it

Metabolism	Hepatic metabolism via proteolytic degradation; no major CYP450 involvement.
Excretion	Renal excretion of intact drug is minimal; SKYTROFA (lonapegsomatropin) is a long-acting growth hormone prodrug that is primarily eliminated via cellular proteolysis and renal catabolism. The parent compound is not significantly excreted unchanged in urine. Less than 5% of the dose is recovered as intact drug in urine; biliary/fecal excretion is negligible.
Half-life	Terminal elimination half-life: approximately 25-30 hours in pediatric patients with growth hormone deficiency (GHD), allowing once-weekly subcutaneous dosing. The long half-life is attributed to the sustained release of active somatropin from the prodrug conjugate and reduced renal clearance.
Protein binding	Approximately 80-90% bound to growth hormone binding protein (GHBP) in plasma. Albumin binding is minimal. Binding is saturable at high concentrations.
Volume of Distribution	Volume of distribution (Vd) is approximately 0.3-0.5 L/kg, indicating distribution primarily into extracellular fluid and tissues, with limited penetration into deep compartments.
Bioavailability	Subcutaneous: Absolute bioavailability is approximately 75-85% in pediatric GHD patients after injection into the thigh, abdomen, or buttock; no oral formulation is available.
Onset of Action	Subcutaneous: Onset of clinical effect (increased serum IGF-1 levels) occurs within 4-8 hours after the first dose, with peak IGF-1 levels observed at 24-48 hours.
Duration of Action	Duration: The pharmacodynamic effect on IGF-1 levels is sustained over the 7-day dosing interval. Clinical effects on growth require chronic weekly administration for months to years; a single dose does not produce measurable height gain.

Classification & Brands

Dosing & administration

Subcutaneous injection of 0.2-0.4 mg/kg/week (0.03-0.06 mg/kg/day) given as daily divided doses or weekly single dose.

Dosage form	INJECTABLE
Renal impairment	Estimated GFR <30 mL/min/1.73 m²: contraindicated. For GFR 30-60 mL/min/1.73 m²: initiate at 0.1 mg/kg/week, titrate based on IGF-I levels. ESRD: not recommended.
Liver impairment	Child-Pugh Class C: contraindicated. Child-Pugh Class A or B: no dose adjustment required, but monitor liver function and IGF-I levels.
Pediatric use	For growth hormone deficiency: 0.025-0.05 mg/kg/day subcutaneously, with maximum 0.1 mg/kg/day. Dose adjusted based on IGF-I levels and growth response.
Geriatric use	In elderly patients with adult growth hormone deficiency: start at 0.1-0.2 mg/kg/week, with lower initial dosing (0.1 mg/kg/week) and careful titration based on IGF-I levels and adverse effects. Monitor for fluid retention and glucose intolerance.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for SKYTROFA (SKYTROFA).

Breastfeeding	Excretion into breast milk is minimal due to high molecular weight; M/P ratio not established. No adverse effects reported in nursing infants. Caution advised; use only if clearly needed.
Teratogenic Risk	No reported teratogenic risk; somatropin is a protein hormone with low placental transfer. Animal studies show no fetal harm. Inadvertent use during pregnancy not associated with congenital anomalies. Benefit-risk assessment advised.
Fetal Monitoring

Warnings & precautions

■ FDA Black Box Warning

Increased mortality in patients with acute critical illness due to complications following open heart surgery, abdominal surgery, multiple accidental trauma, or acute respiratory failure. Not approved for these uses.

Side Effect Profile

Serious Effects

Absolute Contraindications

["Hypersensitivity to somatrogon or any excipients","Acute critical illness with complications (e.g., open heart surgery, abdominal surgery, trauma, respiratory failure)","Active malignancy","Diabetic retinopathy (active proliferative or preproliferative)","Children with closed epiphyses (except for adult growth hormone deficiency)"]

Clinical Precautions

Precautions

["Increased risk of neoplasms in patients with pre-existing malignancies or predisposition; monitor for new growths.","Benign intracranial hypertension (pseudotumor cerebri) with papilledema, visual changes, headache, nausea/vomiting.","Slipped capital femoral epiphysis (hip pain/limp in children).","Progression of scoliosis in children.","Pancreatitis risk, especially in children.","Fluid retention/edema in adults.","Hypersensitivity reactions including anaphylaxis.","Increased risk of secondary neoplasms in pediatric cancer survivors (especially CNS tumors).","May reduce insulin sensitivity; monitor glucose levels."]

Clinical Tips & Counseling

Drug interactions

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SKYTROFA

Clinical safety rating: caution

Comprehensive clinical and safety monograph for SKYTROFA (SKYTROFA).

How it works

What the body does with it

Metabolism	Hepatic metabolism via proteolytic degradation; no major CYP450 involvement.
Excretion	Renal excretion of intact drug is minimal; SKYTROFA (lonapegsomatropin) is a long-acting growth hormone prodrug that is primarily eliminated via cellular proteolysis and renal catabolism. The parent compound is not significantly excreted unchanged in urine. Less than 5% of the dose is recovered as intact drug in urine; biliary/fecal excretion is negligible.
Half-life	Terminal elimination half-life: approximately 25-30 hours in pediatric patients with growth hormone deficiency (GHD), allowing once-weekly subcutaneous dosing. The long half-life is attributed to the sustained release of active somatropin from the prodrug conjugate and reduced renal clearance.
Protein binding	Approximately 80-90% bound to growth hormone binding protein (GHBP) in plasma. Albumin binding is minimal. Binding is saturable at high concentrations.
Volume of Distribution	Volume of distribution (Vd) is approximately 0.3-0.5 L/kg, indicating distribution primarily into extracellular fluid and tissues, with limited penetration into deep compartments.
Bioavailability	Subcutaneous: Absolute bioavailability is approximately 75-85% in pediatric GHD patients after injection into the thigh, abdomen, or buttock; no oral formulation is available.
Onset of Action	Subcutaneous: Onset of clinical effect (increased serum IGF-1 levels) occurs within 4-8 hours after the first dose, with peak IGF-1 levels observed at 24-48 hours.
Duration of Action	Duration: The pharmacodynamic effect on IGF-1 levels is sustained over the 7-day dosing interval. Clinical effects on growth require chronic weekly administration for months to years; a single dose does not produce measurable height gain.

Classification & Brands

Dosing & administration

Subcutaneous injection of 0.2-0.4 mg/kg/week (0.03-0.06 mg/kg/day) given as daily divided doses or weekly single dose.

Dosage form	INJECTABLE
Renal impairment	Estimated GFR <30 mL/min/1.73 m²: contraindicated. For GFR 30-60 mL/min/1.73 m²: initiate at 0.1 mg/kg/week, titrate based on IGF-I levels. ESRD: not recommended.
Liver impairment	Child-Pugh Class C: contraindicated. Child-Pugh Class A or B: no dose adjustment required, but monitor liver function and IGF-I levels.
Pediatric use	For growth hormone deficiency: 0.025-0.05 mg/kg/day subcutaneously, with maximum 0.1 mg/kg/day. Dose adjusted based on IGF-I levels and growth response.
Geriatric use	In elderly patients with adult growth hormone deficiency: start at 0.1-0.2 mg/kg/week, with lower initial dosing (0.1 mg/kg/week) and careful titration based on IGF-I levels and adverse effects. Monitor for fluid retention and glucose intolerance.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for SKYTROFA (SKYTROFA).

Breastfeeding	Excretion into breast milk is minimal due to high molecular weight; M/P ratio not established. No adverse effects reported in nursing infants. Caution advised; use only if clearly needed.
Teratogenic Risk	No reported teratogenic risk; somatropin is a protein hormone with low placental transfer. Animal studies show no fetal harm. Inadvertent use during pregnancy not associated with congenital anomalies. Benefit-risk assessment advised.
Fetal Monitoring