Efficacy and Safety of Bimagrumab/BYM338 at 52 Weeks on Physical Function, Muscle Strength, Mobility in sIBM Patients

Estimated Within Treatment Group Lean Body Mass (LBM) Ratio at Week 52

LBM was measured via dual energy x-ray absorptiometry (DXA) and calculated as (LBM at Week 52/LBM at baseline)\*100 . A positive change from baseline indicates improvement.

Time frame: Baseline, Week 52

Change From Baseline in Quadriceps Quantitative Muscle Testing (QMT) on the Right Side at Week 52

Quadriceps muscle strength was measured by portable fixed dynamometry (PFD) on the right side. A negative change from baseline indicates deterioration.

Time frame: Baseline, Week 52

Change From Baseline in Sporadic Inclusion Body Myositis (sIBM) Functional Assessment (sIFA) Score at Week 52

Self-reported physical function was assessed by a newly developed patient reported outcome named sporadic inclusion body myositis (sIBM) functional assessment (sIFA). The sIFA consists of 11 items scored on an 11 point numerical rating scale from 0 (no difficulty) to 10 (unable to do) across 3 domains: upper body functioning, lower body functioning and general functioning. Participants completed the assessment where the recall period was the past week prior to completing the patient reported outcome (PRO). The total score on the sIFA scale ranges from 0 (minimum) to 110 (maximum). Higher values represent a worse outcome. A positive change from baseline indicates deterioration.

Time frame: Baseline, Week 52

Estimated Annual Number of Falls Per Patient Within Treatment Group

Participants documented any fall occurrences in a paper diary during the study.