 For the first 12 weeks in this extension study, patients will receive ATYR1940 at the highest tolerated dose received in the parent study; no dose adjustments are allowed during this 12-week period. After 12 weeks, if the patient is demonstrating good tolerability, the ATYR1940 dose may be increased on a patient-specific basis at the Investigators discretion, in consultation with the Sponsor and Medical Monitor. ATYR1940 dose increases to 3.0 mgkg are not permissible. 