It included following changes: - Muscle fibrosis MRI assessment was removed from inclusion criteria, and the fibrosis MRI assessment was added as an exploratory endpoint, per Food and Drug Administration (FDA) feedback.

It included following changes: - Safety follow-up was extended to 60 days (+ 3 days) after the last infusion to align with 5 times the half-life of pamrevlumab (12.2 days). - Clarification was added that participants already on an approved DMD therapy should not discontinue that therapy to be eligible for the study. - Study drug administration window was extended from 24 to 48 hours to align with updated pamrevlumab stability information. - Electrocardiograms (ECGs) were removed to align with DMD standard of care. - Basophils were added to include all components of the lab testing panel. - Pulmonary function test (PFT) inclusion criteria were clarified. - Criteria for participants to continue into the OLE period were clarified. - Muscle fibrosis MRI assessment and fibrosis endpoint were removed from the OLE period.

It included following changes: - Per investigator feedback, Inclusion Criterion was changed to average (of Screening and Day 0) ppFVC between 45 and 85, inclusive, to mitigate risk and safeguard the wellbeing of the DMD participants, who could have potentially suffered from exhaustion with the original ppFVC requirements.

It included following changes: - Participation requirements for cardiac MRI, pneumonia and influenza vaccinations, and acceptable ranges for central laboratory assessments were clarified. - Inclusion Criterion was changed to remove the requirement for cardiomyopathy diagnosis. - The exclusion criterion for allergic reactions was expanded to include hypersensitivity to the study drug components or the gadolinium-based contrast agents required for the MRI. - Casimersen (amondys 45) was added to the prohibited concomitant medications, due to its recent drug approval. - Cardiac and pulmonary assessment exclusion criteria were expanded to exclude participants with abnormal glomerular filtration rate (GFR) or acute kidney injury. - Clarification was added to state that pamrevlumab would be permanently discontinued in the case of a serious or life-threatening allergic reaction. - Instruction was added for participants to speak to the study doctor and assess if an unscheduled visit is required after any adverse reaction during an home health care (HHC) visit. - Guidance regarding the time separation between study drug and COVID-19 vaccination was added. - Guidance regarding visit modality (in-person vs remote) and visit scheduling was added to align with FDA/European Medicines Agency (EMA) guidance regarding the COVID-19 pandemic and the resulting need for flexibility for visits and assessments. • Contraception requirements were added to include permitted methods, such as condoms and abstinence. • Clarification was added that subjects who discontinue from the Double-blind Treatment period were not eligible for OLE participation. • AE reporting and AE definition were updated to reflect International Council for Harmonisation (ICH) E2A standard language.

It included following changes: - Bone fracture safety assessments were added to align with the pediatric investigational plan. - Secondary endpoints were rearranged to align with the revised analysis plan. - The exploratory endpoint of summarizing the subscores of the 3 regional dimensions of the PUL was added. - Withdrawal criteria were updated to include a description for participants discontinuing infusions. • Additional pharmacokinetics (PK), anti-drug antibodies (ADA), antidrug antibody neutralizing antibody (ADA-NA), and immunogenic reaction blood draws were added to increase the scope of specialty lab testing.