Study to Evaluate the Efficacy and Safety of BMN 333 Versus Vosoritide in Children With Achondroplasia

Inclusion Criteria

• Participants must be aged ≥ 2 to \< 11 years (Phase 2) or ≥ 2 to \< 18 years (Phase 3), at the time of signing the informed consent
• Participants must have ACH (confirmed by documented genetic testing) and open epiphyses
• Are Tanner Stage I (Phase 2) or any Tanner stage (Phase 3)
• Are ambulatory and able to stand without assistance

Exclusion Criteria

• Have any short stature condition other than ACH (eg, hypochondroplasia, trisomy 21, pseudoachondroplasia, GH deficiency)
• Have any of the following disorders: Hypothyroidism or hyperthyroidism, unless treated with evidence of normalized thyroid-stimulating hormone (TSH) levels, diabetes mellitus, unless considered well-controlled, autoimmune inflammatory disease, inflammatory bowel disease, autonomic neuropathy, anemia defined as hemoglobin \< 10 g/dL, vitamin D deficiency, significant hip pathology.
• Have history of any renal insufficiency or cardiac/ cardiovascular disease that places the participant at increased risk of an adverse cardiac outcome in the setting of hypotension.
• Have had bone fractures of the long bones or spine within 6 months prior to screening.
• Have used vosoritide, any other approved product (except GH, as detailed below), investigational product, or investigational medical device for the treatment of ACH or short stature at any time
• Have been treated with GH, insulin-like growth factor 1, or anabolic steroids in the 6 months prior to treatment start