Dose Range Finding Study of Bimagrumab in Sarcopenia

Inclusion Criteria: * Low muscle mass as confirmed by DXA; * Low gait speed \<0.8 m/s * SPPB score less than or equal to 9; * Weigh at least 35 kg; * Adequate dietary intake; Exclusion Criteria: * A lower limb fracture in the past 6 months or any impairment or disease severely affecting gait (e.g. stroke with hemiparesis, myasthenia gravis, Parkinson's disease, peripheral polyneuropathy, intermittent claudication in advanced peripheral vascular disease, spinal stenosis, or severe osteoarthritis of the knee or hip with ineffective pain management); * Requires regular assistance from another person for general activities of daily living (e.g. bathing, dressing, toileting). * Intraocular surgery and laser procedures for refractive correction within 6 months prior to screening; * Any underlying muscle disease including active myopathy or muscular dytrophy; * Confirmed diagnosis of heart failure classified as New York Heart Association Class III or IV (e.g. dilated cardiomyopathy); * Type I diabetes or uncontrolled Type 2 diabetes; * Chronic kidney disease \[estimated glomerular filtration rate (GFR) \< 30 mL/min\]; * History of confirmed chronic obstructive pulmonary disease with a severity grade \> 2 on the Medical Research Council Dyspnea Scale; * Confirmed rheumatoid arthritis or other systemic autoimmune disease requiring immunosuppressive therapy or corticosteroids \>10 mg/d prednisone equivalent; * Known history or presence of severe active acute or chronic liver disease (e.g., cirrhosis); * Myocardial infarction, coronary artery bypass graft surgery, percutaneous coronary intervention (e.g. angioplasty or stent placement), or deep vein thrombosis/pulmonary embolism within 12 weeks of screening; * Active cancer (i.e., under current treatment), or cancer requiring treatment in the last 5 years excluding non-melanoma skin cancers or cancers with excellent prognosis (e.g., early stage prostate or breast cancer, carcinoma in situ of the uterine cervix); * Any chronic active infection (e.g., HIV, Hepatitis B or C, tuberculosis, etc).