Evidence review: Open Peptide Project (verified against primary PubMed, ClinicalTrials.gov & FDA records) · Last checked 2026-10-27. ← Back to Evidence Library

Lonapegsomatropin (Skytrofa, TransCon hGH): what the evidence says

Name: Lonapegsomatropin (Skytrofa, TransCon hGH)
Published: 2026-10-27

At a glance

What it is: a prodrug of human growth hormone: unmodified somatropin is attached to a large PEG carrier through a linker that slowly releases it, so one injection lasts a week. Approved as Skytrofa in Aug 2021 for children 1 year and older with growth failure from GH deficiency; openFDA lists an efficacy supplement approved Jul 25, 2025, and the current label adds adults with GH deficiency. ^{R1, R2}

What the evidence says: Human in the heiGHt trial (161 children), weekly lonapegsomatropin produced slightly faster growth than daily somatropin and met both non-inferiority and superiority tests. ^R3 In adults (foresiGHt, 259 people), it lowered trunk fat and raised lean mass vs placebo. ^R4

Biggest risks: label warnings are the same family as other growth hormone products: serious allergic reactions, possible tumor growth or recurrence, impaired glucose tolerance, raised pressure in the skull and others. Prohibited in sport. ^{R2, R5}

Rating


Human Human evidence	Strong: phase 3 RCTs in children (n = 161) and adults (n = 259) ^{R3, R4}
Animal Animal / lab evidence	Not reviewed
Regulatory	FDA-approved ^R1 · not on FDA's 503A or 503B bulk-substance category lists and not on FDA's compounding safety-risk page ^{R6, R7, R8} · prohibited at all times (WADA S2.2.3) ^R5
Established human dose	Yes, label dose (see Study details)

Evidence verdict: Child growth hormone deficiency: Strong (phase 3 RCT) · Adult growth hormone deficiency: Strong (phase 3 RCT) · Anti-aging or bodybuilding: No human data

This page reports what studies used. It is not dosing advice.

Legend: HUMAN data · ANIMAL / LAB data · UNKNOWN · UNVERIFIED: not yet confirmed against a primary source

About the evidence: well-run sponsor RCTs; the child trial was open-label, and long-term safety relies largely on decades of GH experience.

What is it?

Related pages: human-growth-hormone, somapacitan, somatrogon.

Does it work?

Human heiGHt (children, 52 weeks): height velocity 11.2 vs 10.3 cm/year with daily somatropin; adverse events and immune responses similar. ^{R3, R9}
Human foresiGHt (adults, 38 weeks): trunk fat −1.68% vs +0.37% with placebo; lean mass +1.60 kg vs −0.11 kg. ^{R4, R10}
⚪ Anti-aging or bodybuilding: no human data.

Is it safe?

Label warnings: hypersensitivity, neoplasms, glucose intolerance, intracranial hypertension, fluid retention, and others shared with somatropin. ^R2
Contraindicated in acute critical illness, active cancer and some other settings. ^R2
Human Safety in trials was similar to daily somatropin. ^{R3, R4}

Gray-market vials: extra risks

A gray-market vial has no quality control and no guarantee of identity, strength or sterility. We test retail vials blind under the Open Peptide Standard; see /tests/. A passing test covers one batch on one date and does not mean the compound is safe.

Is it legal?

US: FDA-approved, prescription (Skytrofa), for children and adults. ^{R1, R2}
Compounding: not on FDA's 503A or 503B bulk-substance category lists and not on FDA's compounding safety-risk page. ^{R6, R7, R8}
Sport: prohibited at all times; WADA names lonapegsomatropin under S2.2.3. ^R5

Study details

These are amounts researchers used, not recommendations.

Study	People / model	Route	Amount used	Follow-up	Reported	Citation
heiGHt 2021	161 treatment-naive children with GHD	SC	0.24 mg hGH/kg/week	52 weeks	Height velocity 11.2 vs 10.3 cm/yr (daily somatropin)	PMID 34272849
foresiGHt 2026	259 adults with GHD	SC	Weekly, titrated, per study	38 weeks	Trunk fat −1.68% vs +0.37% (placebo)	PMID 41420532

Full reference list (PubMed, CT.gov, FDA and WADA checked Oct 27, 2026)

^R1 Drugs@FDA, Skytrofa (lonapegsomatropin-tcgd), application BLA761177 (openFDA drugsfda record checked Oct 27, 2026). https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=BLA761177
^R2 Skytrofa prescribing information, label published Oct 26, 2026 (DailyMed, checked Oct 27, 2026). https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=9229f871-bc61-4ddc-8122-d126d40e36ac
^R3 Thornton PS, et al. J Clin Endocrinol Metab. 2021. PMID 34272849
^R4 Biller BMK, et al. J Clin Endocrinol Metab. 2026. PMID 41420532
^R5 WADA. The 2026 Prohibited List, S2.2.3, Growth hormone (GH), its analogues and fragments, naming lonapegsomatropin. https://www.wada-ama.org/sites/default/files/2025-09/2026list_en_final_clean_september_2025.pdf
^R6 FDA, 503A bulk drug substances categories list (updated May 14, 2026). https://www.fda.gov/media/94155/download
^R7 FDA, 503B bulk drug substances categories list (updated Mar 21, 2025). https://www.fda.gov/media/94164/download
^R8 FDA, Certain bulk drug substances for use in compounding that may present significant safety risks (content current Apr 22, 2026). https://www.fda.gov/drugs/human-drug-compounding/certain-bulk-drug-substances-use-compounding-may-present-significant-safety-risks
^R9 ClinicalTrials.gov NCT02781727, heiGHt, phase 3 in children with GH deficiency, completed, 162 enrolled (CT.gov API v2, checked Oct 27, 2026). https://clinicaltrials.gov/study/NCT02781727
^R10 ClinicalTrials.gov NCT04615273, foresiGHt, phase 3 in adults with GH deficiency, completed, 264 enrolled (CT.gov API v2, checked Oct 27, 2026). https://clinicaltrials.gov/study/NCT04615273

Disclaimer

This page is for education and harm reduction, not medical advice or a recommendation to use Lonapegsomatropin (Skytrofa, TransCon hGH). This is a prescription medicine. Use it only under the care of a licensed clinician; do not buy it from research-chemical or gray-market sellers. Report problems to FDA MedWatch (https://www.fda.gov/safety/medwatch).