An Efficacy and Safety Study of BG00011 in Participants With Idiopathic Pulmonary Fibrosis (SPIRIT)

Key Inclusion Criteria:

- Female subjects must be surgically sterile, postmenopausal (minimum 1 year without
menses), or agree to use 1 or more forms of highly effective contraception from the
time of signing of the informed consent form (ICF) until 3 months after the last
injection of study medication. Male subjects must also agree to use 1 or more forms of
highly effective contraception for either themselves or their partners from signing of
ICF until 4 months after last injection of study medication.

- IPF diagnosed based on modified ATS/ERS/JRS/ALAT IPF guideline for diagnosis and
management, within 3 years of Screening.

- Combination of high-resolution computed tomography (HRCT) pattern and, if one has been
obtained, surgical lung biopsy pattern, consistent with diagnosis of IPF.

- Carbon monoxide diffusion capacity (DLco) (corrected for hemoglobin): 30% to 79%
predicted of normal at Screening, with no clinically significant deterioration between
the Screening Visit and randomization, as determined by the Investigator.

- Forced (expiratory) vital capacity (FVC) ≥50% predicted of normal at Screening, with
no clinically significant deterioration between the Screening Visit and randomization,
as determined by the Investigator.

- If a subject is taking nintedanib or pirfenidone, they must be on a stable dose for at
least 8 weeks prior to randomization.

Key Exclusion Criteria:

- Unable to perform pulmonary functional tests (PFTs) or undergo HRCT procedure.

- Peripheral capillary oxygen saturation (SpO2) <90% at rest (if on oxygen
supplementation, must be ≤2 L/min at rest).

- Airway obstruction (i.e., prebronchodilator FEV1/FVC <0.7) or evidence of a
bronchodilator response as defined by an absolute increase of ≥12% and an increase of
≥200 milliliters (mL) in FEV1 or FVC, or both, after bronchodilator use, compared with
the values before bronchodilator use at Screening.

- End-stage fibrotic disease likely requiring organ transplantation within 12 months, or
if the subject has initiated active evaluation for organ transplantation.

- The extent of emphysema in the lungs exceeds fibrosis, based on central review of HRCT
scans.

- Body weight <60 kg at Screening.

- History of or ongoing malignant disease, including solid tumors and hematologic
malignancies, with the exception of basal cell carcinomas, squamous cell carcinomas,
and carcinoma in situ of the cervix that have been completely excised and considered
cured >2 years prior to Screening.

- Significant cardiac disease (e.g., New York Heart Association Class 3 or 4; myocardial
infarction within the past 6 months; unstable angina; coronary angioplasty or coronary
artery bypass graft within the past 6 months; uncontrolled atrial or ventricular
cardiac arrhythmias; or pulmonary hypertension requiring pharmacologic treatment).

- Clinical diagnosis of any connective tissue disease (including but not limited to
scleroderma, polymyositis/dermatomyositis, systemic lupus erythematosus, and
rheumatoid arthritis) or a diagnosis of interstitial pneumonia with autoimmune
features as determined by the Investigator.

- Other disease that may interfere with testing procedures or, in the judgment of the
Investigator, may interfere with study participation or may put the patient at risk
when participating in this study.

- Other unspecified reasons that, in the opinion of the Investigator or Biogen, make the
subject unsuitable for enrollment.

NOTE: Other protocol defined Inclusion/Exclusion criteria may apply.