Key

Inclusion Criteria:

• - Documented diagnosis of IPF per the 2018 American Thoracic Society (ATS)/European Respiratory Society (ERS)/Japanese Respiratory Society (JRS)/Latin American Thoracic Society Clinical Practice Guideline (Raghu 2018).

• - Chest high-resolution computed tomography (HRCT) performed within 12 months prior to first Screening Visit and according to the minimum requirements for IPF diagnosis by central review based on participant's HRCT only (if no lung biopsy is available) or based on both HRCT and lung biopsy (with application of the different criteria in either situation).

If an evaluable HRCT <12 months prior to Screening is not available, an HRCT can be performed at first Screening Visit to determine eligibility, according to the same requirements as the historical HRCT. If a participant has an indeterminate usual interstitial pneumonia (UIP) pattern and their HRCT is >6 months old, if in the opinion of the Investigator their disease has progressed, an additional HRCT may be obtained and reviewed for eligibility.

• - FVC ≥45% of predicted normal at Screening Visits.

• - Forced expiratory volume in 1 second (FEV1)/FVC ≥0.7 at Screening Visits.

• - DLco ≥30% and ≤90% of predicted, corrected for hemoglobin at first Screening Visit.

Key

Exclusion Criteria:

• - Abnormalities detected on electrocardiogram (ECG) of either rhythm or conduction that in the opinion of the Investigator are clinical significant.

Participants with implantable cardiovascular devices (for example, pacemaker) affecting the QT interval time may be enrolled in the study based upon Investigator judgment following cardiologist consultation if deemed necessary, and only after discussion with the Medical Monitor.

• - Emphysema present on ≥50% of the HRCT, or the extent of emphysema is greater than the extent of fibrosis, according to central review of the HRCT.

• - Interstitial lung disease associated with known primary diseases (for example, connective tissue disease, sarcoidosis and amyloidosis), exposures (for example, radiation, silica, asbestos, and coal dust), or drugs (for example, amiodarone).

• - Participants who cannot meet protocol-specified baseline stability criteria.

• - Acute IPF exacerbation within 3 months prior to screening.

• - Receiving nintedanib in combination with pirfenidone.

• - Receiving systemic corticosteroids equivalent to prednisone >10 milligrams (mg)/day or equivalent within 2 weeks prior to Screening.

• - Use of any of the following therapies within 4 weeks prior to Screening and during the Screening Period, or planned during the study: imatinib, ambrisentan, azathioprine, mycophenolate mofetil, cyclophosphamide, cyclosporine A, tacrolimus, bosentan, methotrexate, inhaled treprostinil, phosphodiesterase-5 inhibitors, including sildenafil (unless for occasional use), prednisone at steady dose >10 mg/day or equivalent, or other investigational therapy.

• - History of cigarette smoking or vaping within the previous 3 months.

• - Female participant who is pregnant or breastfeeding.

• - Previous exposure to study intervention or known allergy/sensitivity to study drug.

• - Receiving an investigational treatment within 28 days of randomization.

• - Inadequate IV access.

Arms

Experimental: Axatilimab

Participants will receive axatilimab every 2 weeks during the 26-week Treatment Period.

Placebo Comparator: Placebo

Participants will receive placebo every 2 weeks during the 26-week Treatment Period.

Interventions

Drug: - Axatilimab

Administered as intravenous (IV) infusion

Other: - Placebo

Placebo to match axatilimab administered as IV infusion. Placebo will not contain active ingredient.