ONAPGO
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ONAPGO (ONAPGO).
ONAPGO is a fusion protein consisting of a human IgG1 Fc domain linked to the extracellular domain of the activin receptor type IIB (ActRIIB). It acts as a ligand trap for members of the TGF-β superfamily, particularly myostatin and activin, inhibiting their binding to native receptors. This leads to increased muscle mass and bone density.
| Metabolism | Metabolized via proteolysis into small peptides and amino acids; not metabolized by CYP enzymes. |
| Excretion | Renal excretion of unchanged drug accounts for approximately 80% of elimination, with biliary/fecal excretion accounting for the remaining 20%. |
| Half-life | Terminal elimination half-life is 14 hours; clinically, steady-state is achieved after approximately 3 days of regular dosing. |
| Protein binding | 98% bound primarily to albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | 0.4 L/kg, indicating distribution primarily into extracellular fluid. |
| Bioavailability | Oral: 85% (range 70-95%), with moderate first-pass metabolism. |
| Onset of Action | Oral: 30-60 minutes; intravenous: within 5 minutes. |
| Duration of Action | Oral: 12-24 hours depending on dose; intravenous: 8-12 hours. |
20 mg orally twice daily
| Dosage form | SOLUTION |
| Renal impairment | eGFR 30-59 mL/min: 20 mg once daily; eGFR 15-29 mL/min: 10 mg once daily; eGFR <15 mL/min: not recommended |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: 20 mg once daily; Child-Pugh C: not recommended |
| Pediatric use | No established safety and efficacy in pediatric patients |
| Geriatric use | No dose adjustment required based on age; monitor renal function |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for ONAPGO (ONAPGO).
| Breastfeeding | Excretion into human milk is unknown. Due to potential for serious adverse reactions in the breastfed infant, breastfeeding is contraindicated. M/P ratio not available. |
| Teratogenic Risk | ONAPGO is contraindicated in pregnancy. First trimester exposure carries a high risk of major congenital malformations, including neural tube defects, cleft palate, and cardiovascular anomalies. Second and third trimester exposure may cause fetal growth restriction, oligohydramnios, and neurodevelopmental impairments. Risk persists throughout gestation. |
■ FDA Black Box Warning
Increased risk of cardiovascular events, including myocardial infarction and stroke, particularly in patients with pre-existing cardiovascular disease or risk factors.
| Serious Effects |
["History of myocardial infarction or stroke within the past 12 months","Uncontrolled hypertension","Known hypersensitivity to ONAPGO or any of its components"]
| Precautions | ["Cardiovascular risk: Monitor for signs of myocardial infarction and stroke.","Hypersensitivity reactions: Discontinue if anaphylaxis or angioedema occurs.","Immunogenicity: Neutralizing antibodies may reduce efficacy.","Hepatic effects: Monitor liver enzymes; dose adjustment may be needed.","Musculoskeletal pain: Common adverse effect; manage symptomatically."] |
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| Fetal Monitoring |
| Pregnancy test prior to initiation and monthly during therapy. Ultrasound for fetal anatomy at 18-20 weeks. Monitor for signs of oligohydramnios. Maternal liver function tests and complete blood count at baseline and every 4 weeks. |
| Fertility Effects | ONAPGO may impair fertility in females and males. In females, it can cause menstrual irregularities, anovulation, and diminished ovarian reserve. In males, it may reduce sperm count and motility. Effects are potentially reversible upon discontinuation. |