Efficacy and safety of histrelin subdermal implant in children with central precocious puberty: a multicenter trial.

Context: GnRH analog (GnRHa) therapy for central precocious puberty (CPP) typically involves im injections. The histrelin implant is a new treatment that provides a continuous slow release of the GnRHa histrelin.
Objective: The objective of the study was to investigate the safety and efficacy of the subdermal histrelin implant for the treatment of CPP in treatment naive and previously treated children.
Design: This was a phase III, open-label, prospective study of 1-yr duration.
Setting: The study was conducted at nine U.S. medical centers.
Patients: Girls ages 2-8 yr (naive) or 2-10 yr (previously treated) and boys 2-9 yr (naive) or 2-11 yr (previously treated) with clinical evidence of CPP and a pretreatment pubertal response to leuprolide stimulation were eligible.
Intervention: A 50-mg histrelin implant was inserted sc in the inner upper arm.
Main Outcome Measures: Peak LH after GnRHa stimulation testing and estradiol (girls) and testosterone (boys) were the main outcome measures.
Results: Thirty-six subjects (20 naive) were enrolled. By 1 month, peak LH fell from 28.2 +/- 19.97 (naive) to 0.8 +/- 0.39 mIU/ml (P < 0.0001) and from 2.1 +/- 2.15 (previously treated) to 0.5 +/- 0.32 mIU/ml (P < 0.0056). Estradiol suppressed from 24.5 +/- 22.27 (naive) to 5.9 +/- 2.37 pg/ml (P = 0.0016) and remained suppressed in previously treated subjects, as did testosterone. Suppression was maintained throughout the study. No significant adverse events occurred.
Conclusions: The subdermal histrelin implant achieves and maintains excellent suppression of peak LH and sex steroid levels for 1 yr in children with CPP. The treatment is well tolerated. Long-term studies are needed to confirm these results.