The purpose of this study is to evaluate i) the effect of multiple doses of vosoritide and ii) the effect of the therapeutic dose of vosoritide compared to human growth hormone (hGH), in children with idiopathic short stature (ISS).

Key Inclusion Criteria

1. Height assessment corresponding to a height Z-score of ≤ -2.25 SDs in reference to the general population of the same age and sex, as calculated using the Centers for Disease Control and Prevention (CDC) growth charts
2. Tanner Stage 1, at time of signing the ICF (unless too young to stage).

Key Exclusions

1. Known chromosomal imbalance or genetic variant causing short stature syndrome, including but not limited to Laron syndrome, Prader-Willi syndrome, Russell-Silver Syndrome, Turner syndrome, disproportionate skeletal dysplasias, abnormal SHOX gene analysis, or Rasopathy (including Noonan syndrome)
2. Previous treatment with a growth promoting agent