This is a multicenter, randomized, open-label, active-controlled Phase III clinical trial to evaluate the efficacy and safety of Inpegsomatropin injection，once a week，compared with recombinant human growth hormone (rhGH) in children with idiopathic short stature (ISS). It plans to enroll 300 children with ISS, who will be randomized , stratified by gender and age, and assigned to either the experimental group or the positive controlled group. Each participant will undergo a screening period (up to 12 weeks), a treatment period (52 weeks), and a post-treatment follow-up period (5 weeks). And the safety and efficacy will be evaluated.

Inclusion Criteria:

• Prepubertal children: boys aged ≥3 years and <11 years at screening with testicular volume <4 mL; girls aged ≥3 years and <10 years at screening with breast development at Tanner Stage I, i.e., no palpable breast glandular tissue.
• Compared to chronological age, bone age is advanced by no more than 1 year or delayed by no more than 2 years (i.e., -2 years ≤ bone age - chronological age ≤ 1 year).
• Height at screening is below -2 standard deviations (SD) from the mean for age and sex, with height reference to Appendix 1.
• Body mass index (BMI) is within the 5th to 95th percentile for age and sex of healthy children, with reference to Appendix 2.
• Peak GH level ≥10.0 ng/ml in at least one GH stimulation test.
• No prior systemic pharmacological treatment for growth promotion (continuous use ≥1 month), including but not limited to growth hormone, insulin-like growth factor 1 (IGF-1), etc.
• The legal guardian understands and signs the informed consent form. If the participants is ≥8 years old, they must also sign the informed consent form. For participants under 8 years old who are able to express their consent, their assent should be clearly documented.

Exclusion Criteria:

• Individuals with closed epiphyses;
• Other types of growth and developmental abnormalities, including confirmed or highly suspected growth hormone deficiency (GHD), Noonan syndrome, Prader-Willi syndrome, Russell-Silver syndrome, Turner syndrome, small for gestational age, short stature due to SHOX gene abnormalities, growth delay due to malnutrition, growth delay due to hypothyroidism, and other short statures with a clear etiology; genetic testing results must be obtained before randomization to exclude short stature caused by definite genetic abnormalities;
• Individuals who have participated in any other clinical trial within 3 months prior to screening and have received pharmacological or non-pharmacological interventions;
• Individuals who received inhaled corticosteroids for more than 2 consecutive weeks, or oral or intravenous corticosteroids for more than 1 consecutive week, within the 3 months prior to screening;
• Individuals who are currently receiving or require long-term treatment with other therapies that may affect growth, including but not limited to methylphenidate, sex hormones, gonadotropin-releasing hormone analogs, aromatase inhibitors, anabolic agents, insulin, etc.;
• Individuals with abnormal liver or kidney function at screening (ALT > 1.5 times the upper limit of normal, Cr > upper limit of normal);
• Individuals diagnosed with diabetes mellitus, or with fasting blood glucose ≥6.1 mmol/L on two consecutive occasions;
• Individuals with chronic infectious diseases, such as chronic hepatitis B;
• Individuals with systemic chronic diseases, such as moderate to severe anemia, malnutrition, hypothyroidism, chronic kidney disease, cardiovascular diseases (e.g., dilated cardiomyopathy, etc.), psychiatric and psychological disorders, or those with congenital anomalies requiring clinical intervention as determined by the investigator;
• Individuals with congenital skeletal abnormalities, or those with scoliosis exceeding 15°, limping, or a history of slipped capital femoral epiphysis;
• Individuals with a history of increased intracranial pressure;
• Individuals with a history of malignancy or currently having active malignancy, including intracranial tumors;
• Individuals with severe allergic constitutions, or known allergies to growth hormone or its excipients;
• Individuals with any other disease that the investigator deems may endanger the subject's safety or compromise compliance with the study protocol.