A Study of the Effect of BIIB023 on Muscle Atrophy in Healthy Male Volunteers

Inclusion Criteria:

- Deemed healthy as determined by the Investigator based on medical history, 12-lead
electrocardiogram, vital signs, and clinical laboratory parameters at Screening, and
physical examination at Baseline

- Body mass index (BMI) between 18.5 and 32 kg/m2, inclusive, at the time of Screening

- Willing to abstain from using tobacco and tobacco-containing products during the
study

- Willing to limit the intake of alcohol to no more than 2 units per day throughout the
study; exceptions are 48 hours prior to Screening, 48 hours prior to Day 1, and
during the in-clinic immobilization period when no alcohol will be permitted. One
unit of alcohol is defined as 12 fluid ounce (fl oz) of beer, 5 fl oz of wine, or 1.5
fl oz of liquor

- Willing to maintain a regular diet for the duration of the study and a recreational
level of physical activity defined as participation in an exercise program or other
physical activity at a level of intensity that does not exceed the level prior to
study entry

- Practice effective contraception during the study and be willing and able to continue
contraception for at least 6 months after the last dose of study treatment.

Exclusion Criteria:

- History of or positive test result at Screening for human immunodeficiency virus
(HIV).

- History or positive test result at Screening for hepatitis C virus (HCV) antibody or
hepatitis B virus (defined as positive for hepatitis B surface antigen [HBsAg] or
hepatitis B core antibody [HBcAb]).

- History of tuberculosis (TB) or a positive QuantiFERON®-TB Gold test. There must be
no other clinical evidence of TB on physical examination of the subject.

- Use of tobacco or tobacco-containing products within 3 months prior to Screening

- Known history of thrombophilia, hypercoagulopathy, or prior history of deep vein
thrombosis (DVT) or pulmonary embolism (PE)

- History of physical activity consistent with endurance training or resistance
training within 6 months prior to Screening

- Any back, leg, knee, or shoulder complaints that may interfere with the use of
crutches

- Prolonged travel (more than 6 hours) within 2 weeks prior to randomization.