This is a Phase 2 multicenter, randomized, double-blinded, placebo-controlled study that will evaluate the safety and efficacy of host-directed therapeutics in hospitalized adults diagnosed with Acute Respiratory Distress Syndrome (ARDS) utilizing a platform trial design.

Cohort B: Participants will be randomized to receive either a placebo or paridiprubart.

This record describes the default procedures and analyses for Cohort B. Please see NCT06703073 for information on the BP-ARDS-P2-001 Master Protocol.

This is a master protocol for a Phase 2 platform clinical trial to evaluate host-directed therapeutic candidates (i.e., investigational product, IP) for the treatment of hospitalized participants diagnosed with ARDS. The safety and efficacy of each IP will be studied within its own cohort (IP versus Placebo). All patients will continue to receive standard treatments for ARDS as per the investigator. An individual participant will complete the study in approximately 90 days. The study will include a screening period (<24 hours from providing informed consent to treatment), in-hospital treatment period with IP/placebo starting on Day 1 through discharge from the hospital, and a follow-up period after discharge from the hospital through the end of study (Day 90 + 2 weeks). Outcome data will be assembled for each patient over time (such as ventilatory status, oxygenation, and survival). Functional status using the WHO Ordinal scale and Karnofsky scale will be collected. Resource utilization will be calculated (length of stay in a critical care setting, days intubated, and survival).

All participants will undergo a series of physical exams, laboratory assessments/biomarker collections, ECG, Chest X-ray or CT scan, and questionnaires through Day 90. Exploratory biomarkers will be evaluated over time to facilitate clinical learning. This record only includes information relevant to the paridiprubart cohort.

Inclusion Criteria:

The following inclusion criteria are in addition to the exclusion criteria specified in the Master Protocol NCT06703073:

- ARDS Severity of moderate or severe based on PaO2/FiO2 or SpO2/FiO2 assessment at the time of randomization.

Exclusion Criteria:

The following exclusion criteria are in addition to the exclusion criteria specified in the Master Protocol NCT06703073.

-Participant has a known allergy or known hypersensitivity to paridiprubart or its excipients, including polysorbate 80

The overall 2-step randomization scheme will be implemented.

• Randomization Level 1 will be open-label, assigning an eligible patient to one of the available treatment cohorts.
• Randomization Level 2 will be double-blinded and will randomize participants at a 1:1 ratio to receive either IP or placebo within a specific cohort. Thus, the PPD blinded team, site blinded staff members, and participants/legal authorized representative will be considered blinded to study treatment assignment (either IP or placebo) throughout the course of the study.

To preserve the integrity of the study blind, an unblinded pharmacist at each site will be responsible for the reconstitution and dispensation of all study drugs and placebos and will endeavor to ensure that there are no observable differences between the treatment groups (IP or placebo) when dispensing the study materials.