The aim of TAIN is to develop a neonatal formulation of hydrocortisone, a drug included in the EMA priority list that needs specific evaluation in the age range 0 – 2 years (neonates & infants). Hydrocortisone is an essential glucocorticoid hormone used as replacement therapy for the treatment of congenital and acquired adrenal insufficiency as well playing an important therapeutic role in oncology in infants, specifically brain tumours and leukaemia’s. TAIN involves European leaders in neonatology, paediatric pharmacology, methodology and SMEs that will establish links with ethical bodies and regulatory authorities. The programme will perform in silico experiments and evaluate formulations for neonates. The phase 3 clinical trial comparing the neonatal hydrocortisone versus current (unlicensed) therapy will be optimized using age-appropriate state-of-the-art methods adapted to neonates (including in silico experiments and pharmacokinetics) to validate the components of a Paediatric Investigation Plan. It will be performed by neonatologists trained in paediatric pharmacology and clinical research in line with guidelines on Good Clinical Practice. All the ethical issues will be considered, including pain and distress, blood sampling (number and volume) and informed consent. Parent information sheets and consent form will be submitted to patient and parents’ associations for approval. TAIN will include short term safety studies and Phase 3 clinical studies in neonates and infants. Results will be reported in order to allow a PUMA application to be submitted and to improve neonatal and infant care. Therefore, TAIN will validate the appropriate use of hydrocortisone in neonates and infants which will be of direct benefit to children, their families and health professionals. TAIN will strengthen paediatric drug evaluation across Europe and build up a network of units with experience in clinical research that will be used for additional drug evaluation in neonates.