A Study (Phase 1b/2) of GS3-007a Oral Treatment in Children With Growth Hormone Deficiency (PGHD)

Inclusion Criteria: * chronological age (CA) ≥3 years at Screening * Prepubertal girls or boys * Height at Screening lower than the reference height for normal children of the same chronological age and sex minus 2 standard deviations (-2 SD) * A confirmed diagnosis of growth hormone deficiency (GHD) * Having not been treated with any growth-promoting drugs * BA delayed by ≥6 months compared with the CA at Screening Subjects who meet all of the following criteria are eligible to enroll in the extension study (applicable for Part II extension period) * Subjects who have completed the 52-week treatment period of phase II * Subjects who do not permanently discontinue the investigational Medicinal Product (IMP) during the 52-week treatment period of phase II Exclusion Criteria: * A highly allergic constitution * Suspected or confirmed total pituitary deficiency, including patients previously confirmed with deficiency of ≥2 pituitary hormones other than GH * Being confirmed with other chromosomal abnormalities or growth abnormalities affecting growth * Congenital skeletal dysplasia or serious spinal anomalies * Cognitive hypofunction, neurodevelopmental disorders, or psychiatric/psychological disorders that, in the investigator's opinion, may interfere with evaluation of study endpoints * Any clinically significant abnormality that may affect growth or evaluation of the IMP * Screening magnetic resonance imaging (MRI) scan of the sellar region confirming prior or current intracranial tumor growth * Concurrent use of any medications that may affect growth or response to growth hormone therapy * Epiphyseal closure * Electrocardiogram (ECG) QTcF interval abnormal, with a history of QT/QTc interval prolonged * Hepatic function indicators abnormal at Screening Patients meeting any of the following criteria may not be enrolled in this extension study (applicable for Part II extension period) * Subjects with closed epiphyses * Any clinically significant abnormality that may affect growth or evaluation of the IMP * Known or suspected allergy to the IMP * Women with positive blood human chorionic gonadotropin (hCG) at the pre-treatment visit