LIBELULA: Debio 4326-301: An open-label, single-arm, multi-center, Phase 3 study on the efficacy, safety, and pharmacokinetics of Debio 4326, a triptorelin 12-month formulation, in pediatric participants who are receiving gonadotropin-releasing hormone agonist therapy for central precocious puberty

This is an open-label, single-arm, multi-center, Phase 3 study of Debio 4326, a triptorelin acetate 70 mg, 12-month extended-release formulation, in pediatric participants with central (gonadotropin-dependent) precocious puberty (CPP). This Phase 3 study will enroll pediatric participants who are already on treatment with a gonadotropin-releasing hormone agonist (GnRHa) for CPP and who will switch to Debio 4326. The study is composed of 2 parts (Figure 1-1): - Part A will assess efficacy, safety and pharmacokinetics (PK) over 12 months (52 weeks) after the first injection of Debio 4326. It will furthermore assess the absence of the acute-on-chronic (AOC) phenomenon after the first Debio 4326 injection in a randomly selected subset representing approximately half the study population. Additionally, the triptorelin maximum serum concentration (Cmax) will be measured in a PK subset. - Part B will assess the persistence of the efficacy, safety, and PK profiles over 12 months (52 weeks) after the second injection of Debio 4326, administered 12 months following the first injection. Similar to Part A, the absence of the AOC phenomenon will be investigated after the second Debio 4326 injection in the AOC subset. Part B will also assess the potential accumulation of triptorelin serum concentration after the second Debio 4326 injection, evaluated on Cmax in the PK subset and on triptorelin serum concentration at the end of the dosing interval (Ctrough) in all participants. The study will start with the first 2 participants (sentinel dosing) enrolled in Part A who will be part of the PK subset. When the second participant has completed V5 i.e., after 4 weeks of treatment with Debio 4326, cumulative safety, PK and pharmacodynamics (PD) data of the 2 participants will be reviewed by a Data Monitoring Committee (DMC). The Sponsor will determine, based on the recommendation of the DMC, whether screening of further participants may be initiated. The end of treatment (EOT) occurs 52 weeks after last Debio 4326 injection. Post-treatment assessments after the EOT will depend on the participants' subsequent treatment: 1.Those participants who switch to a non-triptorelin GnRHa therapy after the EOT will undergo a post-treatment visit (PTV) 64 weeks after last Debio 4326 injection, during which residual serum triptorelin levels will be assessed. 2.Those who stop all hormonal treatment with GnRHa at the EOT will undergo a PTV 64 weeks after the last Debio 4326 injection, during which reversibility of luteinizing hormone (LH) suppression and residual serum triptorelin levels will be assessed. 3.Those who continue treatment with another triptorelin formulation after the EOT will not undergo a PTV and will complete the study at the EOT visit.