Triptorelin

Triptorelin (Trelstar, Triptodur) is a real, FDA-approved GnRH agonist — the same mechanism class as leuprolide, engineered with a different single amino-acid substitution, approved for advanced prostate cancer and, in a separate formulation, for central precocious puberty in children.

How it differs from leuprolide

Triptorelin is a decapeptide GnRH agonist, structurally very close to leuprolide but not identical. Both replace the natural glycine at position 6 with a D-amino acid to block enzymatic cleavage and extend duration of action — leuprolide uses D-Leu6 combined with a modified C-terminus (des-Gly10-ethylamide), while triptorelin uses D-Trp6 and keeps the native Gly10-NH2 C-terminus. The downstream mechanism is identical to leuprolide's: continuous agonist stimulation eventually downregulates the pituitary GnRH receptor, suppressing LH, FSH, and testosterone (or estrogen).

The approvals

The FDA approved triptorelin pamoate (as Trelstar Depot, monthly) on 15 June 2000 for palliative treatment of advanced prostate cancer, later followed by 3-month and 6-month depot formulations. A structurally identical but separately branded and dosed product, Triptodur (a 6-month extended-release formulation), was approved 29 June 2017 for central precocious puberty in children 2 years and older — trial data reported roughly 93% of children returning to prepubertal LH levels and 98% maintaining suppression at 12 months, though we could not trace that figure to a specific peer-reviewed citation and would treat it as company/trade-press sourced rather than confirmed in a journal. A registration-supporting Phase III trial for the 6-month adult prostate-cancer formulation (PMID 19888782, Clinical Drug Investigation 2009) followed 120 patients and found castrate testosterone levels (≤50 ng/dL) achieved by day 29 and maintained through 12 months.

The flare, and how it's managed

Like all GnRH agonists, triptorelin causes a transient surge in LH, FSH, testosterone and estradiol after the first dose before suppression sets in — testosterone typically falls to castrate levels by around day 20-29. Standard practice is to start an anti-androgen (such as bicalutamide or flutamide) about a week before the first triptorelin dose and continue it for 2-3 weeks, the same flare-management protocol used with leuprolide. In October 2010 the FDA required a class-wide label update for GnRH agonists (naming Lupron, Zoladex, Trelstar and Eligard specifically) warning of increased risk of diabetes and cardiovascular events including heart attack, sudden cardiac death, and stroke.

Current status

Trelstar and Triptodur remain on the US market (Trelstar commercialized by Verity Pharmaceuticals under license from Debiopharm; Triptodur by Arbor Pharmaceuticals); Decapeptyl is the brand used in Europe and elsewhere. We found real, currently-live "research chemical" vendor listings for triptorelin sold with research-use-only disclaimers, but no FDA warning letter naming triptorelin specifically — the FDA's recent peptide-vendor enforcement wave has focused on GLP-1 analogs, not this drug class.