This is a Phase 2, open-label multi-center long-term extension study, with approximately 70 subjects, to evaluate the safety and efficacy of BMN111 in children with Achondroplasia until subjects reach near-adult final height. Eligible subjects will have completed 1 year of BMN111 or placebo treatment in the 111-206 study and once enrolled in the 111-208 extension study will receive a daily dose of BMN111 by subcutaneous injection according to their age as determined by 111-206.

Inclusion Criteria:

1. Must have completed Study 111-206 on investigational treatment (BMN 111 or placebo).
2. Parent(s) or guardian(s) are willing and able to provide written, signed informed consent after the nature of the study has been explained and prior to performance of any research related procedure. Also, subjects under the age of majority are willing and able to provide written assent (if required by local regulations or the IRB/IEC) after the nature of the study has been explained and prior to performance of any research-related procedure. Subjects who reach the age of majority in their country while the study is ongoing will be asked to provide their own written consent again upon reaching the legal age of majority.
3. Are willing and able to perform all study procedures

Exclusion Criteria:

1. Permanently discontinued BMN 111 or placebo prior to completion of Study 111-206
2. Have a clinically significant finding or arrhythmia on ECG that indicates abnormal cardiac function or conduction or QTc-F > 450 msec
3. Require any investigational agent (except BMN 111) prior to completion of study period
4. Current therapy with antihypertensive medications, angiotensin-converting enzyme (ACE) inhibitors, angiotensin II receptor blockers, diuretics, beta-blockers, calcium-channel blockers, cardiac glycosides, systemic anticholinergic agents, GnRH agonists, any medication that may impair or enhance compensatory tachycardia, diuretics, or other drugs known to alter renal or tubular function
5. Pregnant or planning to become pregnant (self or partner) at any time during the study
6. Concurrent disease or condition that, in the view of the investigator, would interfere with study participation or safety evaluations, for any reason
7. Have a condition or circumstance that, in the view of the investigator, places the subject at high risk for poor treatment compliance