An Extension Study to Evaluate the Efficacy and Safety of BMN 111 in Children With Achondroplasia

Inclusion Criteria: * Must have completed Study 111-301 * Female \>= 10 years old or who have begun menses must have a negative pregnancy test at the Baseline Visit and be willing to have additional pregnancy tests during the study * If sexually active, willing to use a highly effective method of contraception while participating in the study * Are willing and able to perform all study procedures * 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. Exclusion Criteria: * Permanently discontinued BMN 111 or placebo prior to completion of the 111-301 study * Have a clinically significant finding or arrhythmia on Baseline ECG that indicates abnormal cardiac function * Evidence of decreased growth velocity (\<1.5 cm/year) as assessed over a period of at least 6 months or of growth plate closure (proximal tibia, distal femur) through bilateral lower extremity X-rays. * Require any investigational agent prior to completion of study period * Current therapy with medications known to alter renal function * Pregnant or breastfeeding or plan to become pregnant during study * Concurrent disease or condition that, in the view of the investigator, would interfere with study participation or safety evaluations, for any reason. * Have a condition or circumstance that, in the view of the investigator, places the subject at high risk for poor treatment compliance or for not completing the study.