A Study to Assess the Efficacy, Safety, and Pharmacokinetics of Debio 4326 in Pediatric Participants With Central Precocious Puberty (LIBELULA™ Clinical Trial)

Inclusion criteria

• Diagnosis of central precocious puberty.
• Onset of development of sex characteristics (i.e., breast development in girls or testicular enlargement in boys according to the Tanner method) before the age of 8 years in girls and 9 years in boys.
• Initially, only participants aged (a) 5 to 8 years inclusive (i.e., <9 years) are eligible. The Sponsor will determine based on the recommendation of the DMC following the interim analysis whether participants aged (b) 2 to 4 years inclusive (i.e., <5 years) and/or (c) 9 to 10 years inclusive (i.e., <11 years) may be recruited.
• Participant to receive at least 1 year of gonadotropin-releasing hormone agonist (GnRHa) therapy from study treatment start.
• (a) Pre-treated participants: Start of initial GnRHa therapy no later than 18 months after onset of the first signs of CPP.

(b) Treatment-naive participants: Start of Debio 4326 treatment no later than 18 months after onset of the first signs of CPP.

• (a) Pre-treated participants: Difference between bone age (Greulich and Pyle method) and chronological age of ≥1 year based on historical values at the initiation of the GnRHa therapy.

(b) Treatment-naive participants: Difference between bone age (Greulich and Pyle method) and chronological age of ≥1 year.

• (a) Pre-treated participants: Pubertal-type LH response (LH ≥6 IU/L) following a GnRH/GnRHa stimulation test, or random non-stimulated serum LH >0.5 IU/L (if considered local standard of care), based on historical values prior to the initiation of GnRHa therapy.

(b) Treatment-naive participants: Pubertal-type LH response (≥6 IU/L) 30 minutes following a GnRHa [leuprolide acetate 20 micrograms per kilogram (μg/kg) subcutaneous injection (SC)] stimulation test before treatment initiation.

• (a) Pre-treated participants: Clinical evidence of puberty, defined as Tanner Staging ≥2 for breast development for girls and testicular volume ≥4 milliliter (mL) (cubic centimeter [cc]) for boys, prior to the initiation of GnRHa therapy.

(b) Treatment-naive participants: Clinical evidence of puberty, defined as Tanner Staging ≥2 for breast development for girls and testicular volume ≥4 mL (cc) for boys.

Exclusion criteria

• Gonadotropin-independent (peripheral) precocious puberty: gonadotropin-independent gonadal or adrenal sex steroid secretion.
• (a) Pre-treated participants: Non-progressing, isolated premature thelarche prior to the initial GnRHa therapy.

(b) Treatment-naive participants: Non-progressing, isolated premature thelarche.

• Presence of an unstable intracranial tumor or an intracranial tumor potentially requiring neurosurgery or cerebral irradiation. Participants with hamartomas not requiring surgery are eligible.
• Any other condition or chronic illness possibly interfering with growth (e.g., renal failure, diabetes, moderate to severe scoliosis, previously treated intracranial tumor).
• Other than GnRHa therapy in pre-treated participants, any ongoing treatment with a potential effect on serum levels of gonadotropins or sex steroids, or possibly interfering with growth, opioids, central nervous system [CNS] stimulants).
• Prior or current therapy with medroxyprogesterone acetate, growth hormone, or Insulin-like growth factor-1 (IGF-1).
• Diagnosis of short stature, i.e., more than 2.25 standard deviations (SD) below the mean height-for-age.
• Known history of seizures, epilepsy, and/or central nervous system disorders that may have been associated with seizures or convulsions.
• Prior (within 2 months of study treatment start) or current use of medications that have been associated with seizures or convulsions.
• Use of anticoagulants (heparin or coumarin derivatives).

Note: Other inclusion/exclusion criteria mentioned in the protocol may apply.