Inclusion Criteria:
1. Informed consent of parent or legal representative of participant and child assent, as age appropriate must be obtained before any study-related activities.
2. At the time of signing the Informed consent form (ICF), the following conditions must be met:
Phase Ib:
Girls: age ≥3and ≤11 years, breast development at Tanner stage 1, body weight ≥16 kg; Boys: age ≥3 and ≤12 years, testis volume \<4 mL, body weight ≥16 kg.
Phase II:
Girls: age ≥3 and ≤9 years, breast development at Tanner stage 1; Boys: age ≥3 and ≤10 years, testis volume \<4 mL.
3. BMI within the range of ±2 SD of the mean BMI for age and sex at screening
4. Height is at least 2 SD below the mean HT for age and sex (HT SDS ≤ -2.0) at screening according to the normal pediatric population standards
5. Diagnosis of GHD confirmed by two different GH stimulation tests performed at screening or within 12 months prior to screening.
6. No prior exposure to GH or IGF-1therapy.
7. Absence of intracranial tumor, as confirmed by MRI or CT. Images or scans obtained within 1 year prior to screening can be used as screening data if accompanied by a medical evaluation and conclusion.
8. AHV \<5 cm/year at screening (Phase II only);
9. BA \< CA at screening (Phase II only);
10. IGF-1 SDS ≤ -1.0 at screening (Phase II only).
Exclusion Criteria:
1. Presence of one or more pituitary hormone deficiencies in addition to growth hormone deficiency.
2. Any suspected or known disease likely to affect growth, or any clinically significant abnormality that would preclude the accurate assessment of standing height (Phase II only), including but not limited to:
* Turner syndrome
* Noonan syndrome
* Laron Syndrome
* Other genetic syndromes with short stature that are caused by chromosomal abnormalities or gene mutations, including but not limited to Prader-Willi syndrome, abnormal SHOX-1 gene analysis, or GH receptor deficiency.
* Born small for gestational age
* Growth retardation due to malnutrition
* Growth retardation due to hypothyroidism.
* Short stature with any other clearly identified etiology.
* Congenital abnormalities causing skeletal abnormalities, or claudication (Phase II only).
* Significant spinal abnormalities (Phase II only).
3. Epiphyseal closure (Phase II only).
4. Abnormal liver function, renal function, or coagulation profile
5. Current or prior history of any malignant disease; or a family history of malignancy.
6. Presence of impaired glucose metabolism, or HbA1c ≥ 5.7%, or a confirmed diagnosis of diabetes mellitus.
7. Clear medical history of cardiovascular, hepatic, renal, gastrointestinal, respiratory, hematological, neurological, or metabolic disorders, or any other condition that, in the opinion of the investigator, makes the participant unsuitable for participation in the study.
8. Any clinically significant abnormality in vital signs, physical examinations, laboratory tests, 12-lead ECG, full spine anteroposterior and lateral X-ray, or B-mode ultrasound, other than those associated with the study disease, as judged by the investigator and will make the participant unsuitable for the study.
9. A positive result for any of the following serological tests during the screening period: HBsAg, Anti-HCV, Anti-HIV, or TP-Ab.
10. Known highly allergic diathesis or hypersensitivity to growth hormone products or any excipient of the investigational drug.
11. Participation in another clinical trial within 3 months prior to screening, or if the time since the last dose is less than 5 half-lives of the previous investigational drug at screening.
12. Receipt of any blood products within 3 months prior to the first dose, poor peripheral venous access, or any medical condition that will preclude tolerance of the blood sampling procedures.
13. Administration of any vaccine within 14 days prior to the first dose or planned vaccination at any time during the study period.
14. The participant and/or the parent/legal representative is likely to be non-compliant with respect to study conduct, as judged by the investigator.
15. Children have been treated with systemic corticosteroid treatment for longer than 2 consecutive weeks within the last 3 months prior to screening (Phase II only).
16. Children have been treated with inhaled glucocorticoid therapy at a dose greater than 400 µg/day of inhaled budesonide or equivalents for longer than 4 consecutive weeks within the last 12 months prior to screening (Phase II only).
17. Receipt within 3 months prior to screening or planned use during the study of medications that may interfere with growth or development (Phase II only).
18. Any other condition that, in the opinion of the investigator, makes the participant unsuitable for participation in the study.
