The primary purpose of this study is to assess the safety and tolerability of escalating doses of NAL ER and to evaluate its effect on respiratory function in participants with IPF.

Inclusion criteria:

• Diagnosis of IPF as determined by a pulmonologist based on American Thoracic Society (ATS)/ European Respiratory Society (ERS) / Japanese Respiratory Society (JRS) / Asociación Latinoamericana de Tórax (ALAT) guidelines.
• SpO2 ≥ 92%, taken after at least 5 minutes in a sitting position, undisturbed and non-stimulated - Saturation of Hemoglobin with Oxygen as measured by pulse oximetry.
• FVC ≥ 40% of Global Lung Function Initiative (GLI) 2012 predicted values- Forced Vital Capacity, as determined by spirometry adhering to ATS/ERS guidelines.

Exclusion criteria:

• Exacerbation of IPF in the last 3 months.
• Positive results for coronavirus infection (COVID-19) at Day -2, prior to Admission to the clinical research unit (CRU).
• Diagnosis of Chronic Obstructive Pulmonary Disease (COPD), or an forced expiratory volume in 1 second (FEV1)/forced vital capacity (FVC) <0.8.
• Currently using any overnight oxygen therapy at any level or delivered by any modality. Intermittent daytime oxygen use of any duration is allowed.
• Diagnosis of sleep disordered breathing (e.g., sleep apnea).
• Upper or lower respiratory tract infection within the 8 weeks prior to admission to the CRU.
• Clinical history of aspiration pneumonitis.

Note: Other inclusion/exclusion criteria mentioned in the protocol may apply.