Not Approved (US) Pipeline & In-Development

Eftansomatropin alfa

also known as: GX-H9, efpegsomatropin, Declage

Genexine and Handok's long-acting growth hormone candidate — approved in South Korea (Declage, 2025) for pediatric growth hormone deficiency; global partnership with Handok for Korean commercialization.

A long-acting recombinant growth hormone fusion protein developed by Genexine (South Korea) using a hybrid Fc (hyFc) half-life extension platform — somatropin is fused to a modified IgD/IgG4 Fc domain that provides FcRn-mediated recycling with minimal effector function. Approved in South Korea as Declage in 2025 for pediatric GH deficiency, with clinical development ongoing in other regions. Has been evaluated for both weekly and every-other-week dosing schedules.

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

once weekly (primary) or every two weeks (studied) (subcutaneous)

Dosing per Korean prescribing information; not established in US populations.

Regulatory status

Approved in South Korea (MFDS) as Declage in 2025 for pediatric growth hormone deficiency, marketed by Handok Inc. Not FDA-approved as of this writing. Phase 3 global program status variable; Genexine has signed regional partnerships (Handok, Tasly) for commercialization in Asia.

References

  1. [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.
  2. [manufacturer] Genexine/Handok. Declage (eftansomatropin alfa) approval announcement, South Korea MFDS, 2025.

Related peptides

Somatropin (HGH)

FDA-approved recombinant human growth hormone — the direct hormone replacement, with multiple clinical indications, prescription-only status, and specific federal criminal provisions against off-label distribution.

Somapacitan

Novo Nordisk's once-weekly growth hormone (Sogroya) — FDA-approved in 2020 for adult GH deficiency and in 2023 for pediatric GH deficiency in children aged 2.5+ years.

Lonapegsomatropin

Ascendis Pharma's once-weekly growth hormone prodrug (Skytrofa) — the first weekly GH to receive FDA approval (August 2021) for pediatric GH deficiency in patients aged 1+ years weighing at least 11.5 kg.

Somatrogon

Pfizer/OPKO's once-weekly growth hormone (Ngenla) — FDA-approved in June 2023 for pediatric GH deficiency in children aged 3+ years; uses a CTP-fusion strategy borrowed from long-acting follitropin alfa.
Disclaimer

This entry is for educational purposes only and does not constitute medical advice. Dosing information reflects published regulatory or research data and is not a recommendation. Many compounds described here are not approved for human use in the United States. Consult a licensed medical professional before considering any peptide therapy.