The purpose of this study is to assess the efficacy and safety of the intravenous drip infusion of ART-123 in patients with acute exacerbation of idiopathic pulmonary fibrosis (IPF) in a multicenter, double-blind, randomized, placebo-controlled, parallel group comparison study, and to confirm its superiority over placebo with survival rate on Day 90 as the primary endpoint.

Main Inclusion Criteria:

• Patients diagnosed with IPF who meet all criteria from (1) through (4) during the course of IPF

• (1)Unexplained development or worsening of dyspnea within 1 month during the course of IPF

• (2)Finding of new, bilateral ground glass opacities and/or consolidation on HRCT

• (3)No apparent Pulmonary infections, pneumothorax, malignant tumors, pulmonary embolism, or left heart failure

• (4)A decrease* in PaO2 of ≥10 mmHg or SpO2 of ≥4% under the same conditions compared with the level at the previous measurements

  • (*) In cases where no PaO2 or SpO2 test values under the same conditions are available, a patient with a P/F ratio ≤300 in the current episode of acute exacerbation is considered to have met criterion (4)

• Aged 40 years or older and no older than 85 years at the time of informed consent with either sex

Main Exclusion Criteria:

• Have intracranial hemorrhage, pulmonary hemorrhage, gastrointestinal bleeding (continued hematemesis, bloody discharge, gastrointestinal ulcer-induced hemorrhage)
• Have a history of cerebrovascular disorder (e.g., cerebral hemorrhage or cerebral infarction) within 52 weeks (364 days) before informed consent
• Patients for whom the completion of hemostatic treatment has not been confirmed after undergoing surgery of the central nervous system or after trauma
• Have a high risk for fatal or life-threatening hemorrhage
• Patients with malignant tumors
• Have acute exacerbation attributable to drug induced pulmonary disorder, after surgery for malignant tumors, chemotherapy, or radiation therapy
• Have acute exacerbation due to a thoracic surgical procedure (including thoracoscopic lung biopsy)
• Have a history of acute exacerbation of IPF
• Receiving mechanical ventilation through intratracheal intubation
• Patients who are pregnant or nursing, or who may be pregnant
• Patients with a platelet count less than 100,000/uL at the time of enrollment
• Patients with severe renal (serum Cr: ≥4 mg/dL) or hepatic (AST/ALT: ≥500 IU/L or T-Bil: ≥10 mg/dL) dysfunction
• Have been administered a commercially available thrombomodulin alfa (recombinant )(Recomodulin® for Intravenous Injection 12800) within 30 days before the start of investigational product administration
• Have a history of hypersensitivity for investigational product