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withdrawn Sexual & Reproductive Health

Abarelix

also known as: Plenaxis, R-3827

The first injectable GnRH antagonist for prostate cancer — a synthetic decapeptide that achieved castration without testosterone flare, later supplanted by degarelix and oral alternatives.

A synthetic decapeptide GnRH receptor antagonist that was the first in its class approved for prostate cancer (2003), achieving immediate testosterone suppression without the agonist flare of leuprolide, but withdrawn from the US market due to anaphylaxis risk.

Mechanism of action

Competitive antagonist at the GnRH receptor on pituitary gonadotrophs. Immediately suppresses LH and FSH release, achieving castrate testosterone without the initial surge (flare) that occurs with GnRH agonists. Histamine release from the formulation was responsible for the anaphylactic reactions that led to withdrawal.

Primary uses

  • Advanced prostate cancer (historical)
  • Androgen deprivation therapy

Typical dosing

100 mg intramuscular, days 1, 15, 29, then every 4 weeks (intramuscular)

US-withdrawn. Superseded by degarelix (Firmagon) and relugolix (Orgovyx).

Regulatory status

FDA-approved in 2003 (Plenaxis, Praecis) for symptomatic advanced prostate cancer under restricted distribution. Voluntarily withdrawn from the US market in 2005 due to systemic allergic reactions. Still available in some markets.

References

  1. [clinical-trial] Trachtenberg J, et al. "A phase 3, multicenter, open label, randomized study of abarelix versus leuprolide plus daily antiandrogen in men with prostate cancer." J Urol, 2002;167:1670-1674.

Related peptides

Degarelix

Ferring's Firmagon — a GnRH antagonist for advanced prostate cancer that achieves castrate testosterone within 3 days, eliminating the clinical flare risk of GnRH-agonist therapy in patients with symptomatic bone metastases or impending spinal cord compression.

Relugolix

The oral alternative to Lupron — a once-daily pill that suppresses testosterone to castrate levels for prostate cancer without the flare, injection, or cold-chain requirements of injectable GnRH agonists.

Leuprolide

The prototypical long-acting GnRH agonist, FDA-approved across multiple formulations (Lupron Depot, Eligard, Fensolvi, Camcevi) for advanced prostate cancer, endometriosis, central precocious puberty, uterine fibroids, and IVF protocols.

Goserelin

AstraZeneca's Zoladex — a long-acting GnRH agonist delivered as a subcutaneous biodegradable implant. FDA-approved for advanced prostate cancer, advanced breast cancer in premenopausal women, endometriosis, and endometrial thinning prior to ablation.
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.