Somapacitan
Somapacitan is an FDA-approved long-acting growth hormone. Somapacitan is a human growth hormone analog carrying a single substitution with an attached albumin-binding side chain. Reversible, non-covalent binding to endogenous albumin slows renal clearance and receptor-mediated elimination, extending the half-life enough to support weekly dosing while the molecule still signals through the normal growth hormone receptor and JAK2/STAT5 pathway.
For research use only.
Key Facts
- CAS
- 1338578-34-9
- Molecular Weight (MW)
- 1310.5 g/mol
- Half-life
- —
- FDA status
- Approved
- Administration Route
- subcutaneous
- Frequency
- —
- Last updated
- Aug 30, 2026
- Reviewed
- Aug 30, 2026
Research summary
Once-weekly albumin-binding growth hormone derivative approved for growth hormone deficiency in adults and in children. It reduces injection frequency from daily to weekly.
Peptide Library's Somapacitan profile summarises 5 cited studies listed in the Science section, the compound's regulatory status, and research-protocol parameters reported for it. It is a research reference, not medical advice.
Protocol
- Dosage Range
- —
- Frequency
- —
- Cycle
- —
- Administration Route
- subcutaneous
- Reconstitution Guide
- —
Sequence & molecular data
| Molecular formula | C54H95N13O20S2 |
|---|---|
| Molecular weight | 1310.5 g/mol |
| CAS number | 1338578-34-9 |
| PubChem CID | 129894493 |
| FDA UNII | 8FOJ430U94 |
Identifiers link to the public PubChem, FDA Substance Registration (UNII), ChEMBL and DrugBank records for the same entity.
Science
Mechanism of Action
Somapacitan is a human growth hormone analog carrying a single substitution with an attached albumin-binding side chain. Reversible, non-covalent binding to endogenous albumin slows renal clearance and receptor-mediated elimination, extending the half-life enough to support weekly dosing while the molecule still signals through the normal growth hormone receptor and JAK2/STAT5 pathway.
Studies
- Efficacy and Safety of Somapacitan Relative to Somatrogon and Lonapegsomatropin in Pediatric Growth Hormone Deficiency: Systematic Literature Review and Network Meta-analysis
- Once-weekly somapacitan in children with Noonan syndrome: randomized controlled phase 3 trial
- Somapacitan in children born small for gestational age: a randomized controlled phase 3 trial
- Somapacitan in children born small for gestational age: 4-year results from phase 2
- Efficacy, safety, and insulin-like growth factor I of weekly somapacitan in children with growth hormone deficiency: 3-year results from REAL4
Regulatory & research status
Somapacitan is an FDA-approved product for specific labelled indications. Approval does not extend to the research contexts described on this page, and approved products are prescription medicines.
| FDA status | Approved |
|---|---|
| Research status | Approved product (see FDA status) |
| Availability | Prescription-Only |
| WADA (sport) | Unknown / Not Listed |
| Library classification | FDA-Approved |
Benefits
—
Potential Side Effects
No side effects listed yet for this entry.
Storage & stability
Lyophilized (freeze-dried) peptide powder is far more stable than the reconstituted solution. Keep sealed vials cold, dry and away from light; long-term storage is typically frozen, with short-term refrigeration for vials in use.
Once reconstituted in bacteriostatic water, keep the solution refrigerated, avoid repeated freeze–thaw cycles and agitation, and label the vial with the reconstitution date and concentration. Discard any solution that turns cloudy or shows particulates.
Degradation rates differ by sequence: peptides containing methionine, cysteine, asparagine or glutamine are more prone to oxidation and deamidation, so shelf life after reconstitution is compound-specific rather than universal.
Read the full guide: how to store peptides before and after reconstitution →
Source: Manning MC, Chou DK, Murphy BM, Payne RW, Katayama DS. Stability of protein pharmaceuticals: an update. Pharm Res. 2010;27(4):544–575. (PMID 20143256). General guidance for research handling; not product-specific instructions.
Somapacitan: frequently asked questions
What is Somapacitan?
Once-weekly albumin-binding growth hormone derivative approved for growth hormone deficiency in adults and in children. It reduces injection frequency from daily to weekly.
How does Somapacitan work?
Somapacitan is a human growth hormone analog carrying a single substitution with an attached albumin-binding side chain. Reversible, non-covalent binding to endogenous albumin slows renal clearance and receptor-mediated elimination, extending the half-life enough to support weekly dosing while the molecule still signals through the normal growth hormone receptor and JAK2/STAT5 pathway.
Is Somapacitan FDA approved?
Yes. Somapacitan is approved by the FDA, and approved products are prescription medicines. Approval is always for specific indications studied in clinical trials, so an approved status does not mean the compound is approved for every use it is discussed for. Research-chemical material sold under the same name is not the approved product.
What peptides are similar to Somapacitan?
Compounds most often compared with Somapacitan include Human Growth Hormone (Somatropin), Lonapegsomatropin, Somatrogon and Pegvisomant. They are grouped by shared mechanism or research area rather than by equivalence, and their regulatory status and evidence base differ.
References
- Efficacy and Safety of Somapacitan Relative to Somatrogon and Lonapegsomatropin in Pediatric Growth Hormone Deficiency: Systematic Literature Review and Network Meta-analysis — Adv Ther, 2024External reference
- Once-weekly somapacitan in children with Noonan syndrome: randomized controlled phase 3 trial — Eur J Endocrinol, 2026External reference
- Somapacitan in children born small for gestational age: a randomized controlled phase 3 trial — Eur J Endocrinol, 2026External reference
- Somapacitan in children born small for gestational age: 4-year results from phase 2 — Eur J Endocrinol, 2026External reference
- Efficacy, safety, and insulin-like growth factor I of weekly somapacitan in children with growth hormone deficiency: 3-year results from REAL4 — Eur J Endocrinol, 2025External reference
Related research, comparisons & guides
Related peptides
Compiled by Peptide Library Editorial · Reviewed Aug 30, 2026 · Updated Aug 30, 2026 · Version 1
This Somapacitan profile is compiled from published literature (5 cited studies linked above), public regulatory records and chemical registries. It describes what research reports; it is not medical advice, and nothing here is a dosing recommendation for humans. Peptide Library does not sell peptides. Editorial policy · How profiles are compiled · Report an error
Track Somapacitan research, inventory and reconstitution in the free Peptide Library app. Get the app for iOS or Android →