The main purpose of this study is to evaluate the safety, tolerability, pharmacokinetics, and immunogenicity of FG-3019, a therapeutic antibody designed to block the pro-fibrotic activity of connective tissue growth factor (CTGF). CTGF triggers the production of collagen and fibronectin, which cause scarring and thickening of the lungs. Participants will be assigned sequentially to one of the 3 dose group: Low, medium, and high FG-3019.

Key Inclusion Criteria:

• have a diagnosis of idiopathic pulmonary fibrosis (IPF) by clinical features and surgical lung biopsy or according to the American Thoracic Society criteria

Key Exclusion Criteria:

• have a history of significant exposure to organic or inorganic dust or drugs known to cause pulmonary fibrosis
• have interstitial lung disease other than IPF
• have pulmonary fibrosis associated with connective tissue disease
• have other forms of idiopathic interstitial pneumonia, such as desquamative interstitial pneumonia, acute interstitial pneumonia, nonspecific interstitial pneumonia, or cryptogenic organizing pneumonia
• have end-stage IPF (total lung capacity of less than 45% of predicted value)
• are listed for lung transplantation at the time of study enrollment
• have significant heart problems
• are pregnant or lactating (if female)

Other inclusion and exclusion criteria may apply.