Not Approved (US) Sexual & Reproductive Health

Corifollitropin alfa

also known as: Elonva, FSH-CTP

Organon/Merck's Elonva — a recombinant long-acting FSH fusion protein (FSH-CTP) used as a single SC injection to replace the first week of daily FSH in IVF stimulation. Approved by the EMA in 2010; never approved in the United States.

A long-acting recombinant FSH produced by fusing the C-terminal peptide (CTP) of hCG-beta onto the FSH beta-subunit in a CHO-cell expression system, exploiting the same prolonged-half-life strategy Schering-Plough/Merck used for hCG. A single 100 or 150 mcg SC injection initiates and sustains multifollicular development for the first 7 days of a controlled-ovarian-stimulation cycle. EMA-approved as Elonva in January 2010. Never FDA-approved: Merck submitted but received a Complete Response Letter from the FDA in 2010 and has not re-filed; the product remains commercially available in Europe and many other markets, but is not available in the United States.

Mechanism of action

FSHR agonism identical to other FSH products; the CTP fusion provides prolonged half-life through CTP-associated O-linked glycan sialylation that reduces renal clearance — the same mechanism that gives hCG its longer half-life relative to LH. Pharmacologic effect of a single 100 mcg dose approximates 7 daily 150 IU doses of conventional FSH.

Primary uses

  • Controlled ovarian stimulation for IVF/ICSI in combination with a GnRH antagonist (ex-US)

Typical dosing

100 (<60 kg) or 150 (≥60 kg) mcg single SC injection on stimulation day 1 (subcutaneous)

Single dose initiates and maintains multifollicular development for 7 days. From day 8 onward, conventional daily recombinant FSH is added if additional stimulation is needed. GnRH antagonist (ganirelix or cetrorelix) started on day 5–6 per local protocol.

Regulatory status

EMA-approved as Elonva (Organon/Merck/MSD, January 2010) for controlled ovarian stimulation in combination with a GnRH antagonist for the development of multiple follicles in women participating in assisted reproductive technology programs. Available in the UK, EU, Canada, Australia, and many other markets. Merck/MSD received an FDA Complete Response Letter in 2010 and has not re-filed; not approved or marketed in the United States.

References

  1. [other] Elonva (corifollitropin alfa) Summary of Product Characteristics. European Medicines Agency.
  2. [pubmed] Devroey P, et al. "A randomized assessor-blind trial comparing highly purified hMG and recombinant FSH in a GnRH antagonist cycle with compulsory single-blastocyst transfer." Fertil Steril, 2012;97:561-571 (corifollitropin-alfa context).
  3. [pubmed] Fauser BC, et al. "Predictors of ovarian response: progress towards individualized treatment in ovulation induction and ovarian stimulation." Hum Reprod Update, 2008;14:1-14.

Related peptides

Follitropin alfa

EMD Serono's Gonal-f — the first recombinant human FSH approved by the FDA (1997). Used for ovulation induction, IVF controlled ovarian stimulation, and male hypogonadotropic hypogonadism fertility induction.

Follitropin beta

Organon/Merck's Follistim AQ (Puregon internationally) — a recombinant human FSH produced independently of follitropin alfa but clinically equivalent; FDA-approved 1997 for ovulation induction and IVF controlled ovarian stimulation.

Follitropin delta

Ferring's Rekovelle — a recombinant human FSH produced in a human cell line (PER.C6), dosed via a personalized algorithm based on serum AMH and body weight. Approved in the EU, UK, Canada, Australia, Japan, and China, but received an FDA Complete Response Letter in February 2026 over manufacturing issues; not currently approved in the United States.

Ganirelix

Organon/Merck's Ganirelix Acetate (formerly Antagon; Orgalutran internationally) — a GnRH antagonist functionally equivalent to cetrorelix for IVF LH-surge prevention, dosed as a daily fixed 250 mcg SC injection.

Cetrorelix

Merck Serono's Cetrotide — a GnRH antagonist used during IVF controlled ovarian stimulation to block premature LH surges. Unlike GnRH agonists, produces immediate gonadotropin suppression without a flare, shortening IVF cycles.
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.