1. Inclusion Criterion was updated to state that participants of child‐bearing potential or with partners of child-bearing potential must consent to use a highly effective method of contraception. The abstinence language was also updated. 2. Stopping Rules were updated to state that Regulatory Authorities, as well as IRBs and ethics committees (ECs), would be informed should unexpected and possibly, probably, or definitely drug-related serious adverse events (SAEs) occurred and/or if the study was paused or stopped per recommendation from the data monitoring committee (DMC). Language was also added stating that, if paused or stopped, the trial would only be restarted following approval by Regulatory Authorities. 3. Updated to include language that if emergent suicidal ideation or behavior was indicated upon review of the Columbia-Suicide Severity Rating Scale (C-SSRS), the investigator should promptly evaluate the subject to ensure proper management and protection of subject safety. 4. Multiple sections were updated to define the Sponsor’s responsibilities with regard to reporting SAEs/Suspected Unexpected Serious Adverse Reactions (SUSARs).

1. Inclusion Criterion was updated to increase the upper age limit from 50 to 55. 2. Updated to clarify that leftover biological samples (from the protocol specified blood and urine requirements) may be used for future research including, but not limited to, biomarker research.

1. Synopsis, Data Monitoring Committee, and Review of Safety Data were updated to indicate that DMC meetings would occur at least 2 times per year instead of quarterly. 2. Schedule of Events was updated to remove the free, total and bound urine SA levels from the Screening Visit. Drug Concentrations Measurements was also updated to reflect this change. 3. Schedule of Events, Footnote g was updated to clarify how the urine sample for N-acetyl-D-mannosamine (ManNAc) testing would be collected. Urine Testing for ManNAc was also updated to reflect this change. 4. Schedule of Events and Selection of Doses and Study Duration were updated to reflect that the Safety Follow up Visit was to be conducted by phone, including clarifications around the Safety Follow-up Call. Based on this change, the assessments to be conducted at this visit were updated to indicate that the Safety Follow-up Call was only for subjects who completed the study and chose not to enroll in the extension study, UX001-CL302, or who discontinued the study early. This call was not required for subjects who were eligible and chose to take part in the extension study, UX001-CL302. Information on any ongoing or new AEs, SAEs, and concomitant medications was to be collected in this phone call. 5. Discussion of Study Design, Including Choice of Control Group was updated to include additional rationale for the 6WMT as a secondary endpoint. 6. List of Abbreviations and Definition of Terms was updated to include “TC", defined as telephone call. 7. Removal of Subjects from Therapy or Assessment, Adverse Events, Adverse Event Reporting, General, Serious Adverse Events, Serious Adverse Drug Reactions, and Requirements for Immediate Reporting, Adverse Drug Reaction Reporting, and Urgent Safety Measures were updated to clarify the end of the data collection period for safety reporting events based on the change to the Safety Follow-up Call (refer to Summary of Change #4 above).

(continued) 8. Study Schedule was updated based on the change to the Safety Follow up Call (refer to Summary of Change #4 above) and to clarify that Screening procedures may have taken place across multiple days to allow enough time to complete all procedures and confirm initial subject eligibility. 9. Dynamometry was updated to clarify the number of test attempts that would be administered for each muscle group (3 versus up to 3). For data analysis, the highest value (rather than an average of the 3 values) was still utilized as specified in the original protocol. 10. Dynamometry was updated to remove an outdated reference for normative grip strength data. 11. Six Minute Walk Test was updated to clarify the 6MWT administration for this protocol. 12. Table and Clinical Laboratory Tests for Safety were updated to clarify the analytes that would be tested in the urinalysis (added blood and leukocyte esterase) and to clarify that microscopic evaluation would be conducted for abnormal urine test results. 13. Volume of Blood to Be Drawn from Each Subject and associated Table were updated to clarify the volume of blood that would be drawn for the serum SA tests, to reduce the number of chemistry and hematology samples obtained, and to clarify the overall volume of blood that would be obtained during the study. The total mL of blood collected through study completion was increased from 108.5 mL to 119.0 mL. 14. Individual Neuromuscular Quality of Life Questionnaire was updated to provide guidance on administering the test to subjects when the scale was not available in the subject’s native language. 15. Pregnancy Testing was updated to remove the reference to a pregnancy test at the Safety Follow-up Visit. 16. Populations Analyzed was updated to match the definition of the SA Analysis Set between the synopsis and the protocol body (ie, urine SA levels was added to Section).

(continued) 17. Subject Information and Consent was modified to remove the requirement for assent from subjects under the age of 18. 18. Safety Contact Information was updated with the correct email address for the Medical Monitor. 19. References section was updated to remove the outdated normative grip strength data reference.

1. The study objectives were modified to designate 3 secondary objectives as “key” secondary objectives. These 3 secondary objectives were to evaluate the effect of 6 g/day of Ace-ER treatment of subjects with GNEM on the following: - Lower extremity composite muscle strength score as measured by dynamometry - Muscle strength in the knee extensors as measured by dynamometry - Physical functioning as measured using the GNEM-FAS mobility domain score 2. Three secondary clinical efficacy endpoints were designated as “key” secondary endpoints. These included the following: - LEC score based on a sum of the mean bilateral strength recorded in the following muscle groups: knee flexors, hip flexors, hip extensors, hip abductors, and hip adductors - Muscle strength in the knee extensors: bilateral total force (in kg) - GNEM FAS mobility domain score Percent predicted muscle strength in the knee extensors was previously included as a secondary endpoint (in addition to total force) and was now listed separately as a tertiary endpoint. 3. Text was added to indicate that Hochberg’s adjustment for multiplicity would be applied for the 3 key secondary endpoints. In addition, geographic region and sex were added as covariates for the primary efficacy analysis. 4. Language regarding urinary SA as a tertiary objective and its assessment was modified. Urinary SA was measured but was not used as a determination of Ace-ER absorption, excretion, and pharmacodynamics.