Eftansomatropin alfa

Mechanism of action

GH receptor agonism by the fused somatropin moiety. The hybrid Fc (hyFc) domain — combining portions of IgD and IgG4 constant regions — enables FcRn-mediated recycling (the same half-life extension mechanism as IgG antibodies) while minimizing FcγR-mediated effector functions such as ADCC and CDC. This produces an extended circulating half-life without the immune activation that full IgG Fc fusion might cause in a hormone replacement context.

Primary uses

• Pediatric growth hormone deficiency (Korea-approved)
• Adult growth hormone deficiency (Phase 2–3 investigated)

Typical dosing

Regulatory status

No marketing approval found (searched October 5, 2026). Not FDA-approved. Orphan drug designation from South Korea's MFDS (Korea Herald). A Chinese partner, TJ Bio, filed a biologics licence application with China's CDE after a phase 3 trial in children with growth hormone deficiency met non-inferiority to daily Norditropin (Korea Biomedical Review). An earlier version of this entry said it had been approved in South Korea as 'Declage' in 2025; no source for that approval could be found, and the claim was removed.

Status as of this entry's last review, October 5, 2026. Approvals, compounding rules and sport rules change; the regulatory tracker is checked more often.

What we checked

Eftansomatropin alfa (GX-H9) is a long-acting growth hormone: somatropin fused to a hybrid antibody Fc fragment so it can be injected weekly or every two weeks. It is a protein, not a short peptide. One trial is indexed on PubMed; this section records what can be checked, including a corrected approval claim.

Identity, computed

Human growth hormone fused to a hybrid IgD/IgG4 Fc domain, a protein of roughly 100 kDa according to a 2021 review; the site's calculator does not model fusion proteins, so no formula is computed.

Regulatory status, read October 5, 2026

Drugs@FDA: 0 records for “eftansomatropin”. EMA medicines list: 0 records for “eftansomatropin”. Run for semaglutide, the same queries return 6 and 5 records (and the registry search 84 trials), so a zero here is an absence, not a broken search. WADA 2026: section S2.2.3; WADA 2027: section S2.2.3.

What the maker or sellers claim

Claim, from the developers: Once-weekly dosing improves convenience and adherence over daily growth hormone. The phase 3 result is reported by the companies and the trade press; we found no peer-reviewed publication of it.

Claim, from an earlier version of this entry: It was approved in South Korea as 'Declage' in 2025. We found no source for that approval and removed the claim.

About long-acting growth hormones

Several long-acting growth hormones are already approved elsewhere, such as lonapegsomatropin and somatrogon, which our growth hormone entries cover. In the one indexed GX-H9 trial, 45 adults with growth hormone deficiency in Europe and Korea received weekly or every-other-week doses or daily Genotropin, with exposure rising with dose; that paper is cited in References.

What we looked for and did not find

No marketing approval found, no FDA or EMA record, and no peer-reviewed report of the phase 3 trial. A Korean orphan designation and a Chinese licence application are reported in the trade press, cited in References.

References

1. [news] Korea Herald. "Handok-Genexine's long-acting growth hormone gets orphan drug status in Korea." Read October 5, 2026.
2. [news] Korea Biomedical Review. "Genexine's Chinese partner applies for product approval of long-acting growth hormone therapy." Read October 5, 2026.
3. [pubmed] Ku CR, et al. "Long-acting FC-fusion rhGH (GX-H9) shows potential for up to twice-monthly administration in GH-deficient adults." Eur J Endocrinol, 2018;179(3):169-179. PMID: 29973375.
4. [clinical-trial] Kim SG, et al. "Safety, pharmacokinetics, and pharmacodynamics of GX-H9 (eftansomatropin alfa), a long-acting recombinant human growth hormone, in healthy volunteers and adults with growth hormone deficiency." J Clin Pharmacol, 2018;58:621-630.

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