A Study to Assess the Efficacy, Safety and Pharmacokinetics of Debio 4326 in Pediatric Participants Receiving Gonadotropin-Releasing Hormone Agonist Therapy for Central Precocious Puberty

Inclusion Criteria:

1. Diagnosis of central precocious puberty and currently receiving GnRHa therapy.

2. Onset of development of sex characteristics (i.e., breast development in girls ortesticular enlargement in boys according to the Tanner method) before the age of 8years in girls and 9 years in boys.

3. Initially, only participants aged (a) 5 to 8 years inclusive (i.e., <9 years) areeligible. The Sponsor will determine based on the recommendation of the DMCfollowing the interim analysis whether participants aged 2 to 4 years inclusive (i.e., <5 years) and/or 9 to 10 years inclusive (i.e., <11 years) may be recruited.

4. Participant to receive at least 1 year of GnRHa therapy from study treatment start.

5. Start of initial GnRHa therapy no later than 18 months after onset of the firstsigns of Central precocious puberty (CPP).

6. Difference between bone age (Greulich and Pyle method) and chronological age of ≥1year based on historical values at the initiation of the GnRHa therapy.

7. Pubertal-type LH response following a GnRH/GnRHa stimulation test, or randomnon-stimulated serum (if considered local standard of care), based on historicalvalues prior to the initiation of GnRHa therapy.

8. Clinical evidence of puberty, defined as Tanner Staging ≥2 for breast developmentfor girls and testicular volume ≥4 mL (cc) for boys, prior to the initiation ofGnRHa therapy.

Exclusion Criteria:

1. Gonadotropin-independent (peripheral) precocious puberty: gonadotropin-independentgonadal or adrenal sex steroid secretion.

2. Non-progressing, isolated premature thelarche prior to the initial GnRHa therapy.

3. Presence of an unstable intracranial tumor or an intracranial tumor potentiallyrequiring neurosurgery or cerebral irradiation. Participants with hamartomas notrequiring surgery are eligible.

4. Any other condition or chronic illness possibly interfering with growth (e.g., renalfailure, diabetes, moderate to severe scoliosis, previously treated intracranialtumor).

5. Other than GnRHa therapy, any ongoing treatment with a potential effect on serumlevels of gonadotropins or sex steroids, or possibly interfering with growth.

6. Prior or current therapy with medroxyprogesterone acetate, growth hormone, orInsulin-like growth factor-1 (IGF-1).

7. Diagnosis of short stature, i.e., more than 2.25 standard deviations (SD) below themean height-for-age.

8. Known history of seizures, epilepsy, and/or central nervous system disorders thatmay have been associated with seizures or convulsions.

9. Prior (within 2 months of study treatment start) or current use of medications thathave been associated with seizures or convulsions.

10. Use of anticoagulants (heparin or coumarin derivatives).