This clinical trial will evaluate the efficacy and safety of a single intravenous dose of agenT-797 administered in addition to standard of care (SOC), compared with placebo plus SOC, in reducing short-term mortality in adult participants with severe pneumonia and moderate to severe AHRF. All participants will receive SOC management for severe pneumonia and acute respiratory distress syndrome (ARDS).

This trial will be conducted in 2 parts (Run-in Phase; Phase 2). The Run-in Phase is designed to characterize the baseline population of the site, where participants will receive open-label agenT-797 plus SOC. After completion of the Run-in Phase, participants will be enrolled and randomized to receive either agenT-797 plus SOC or placebo plus SOC during the double-blinded Phase 2.

Key Inclusion Criteria:

• Admission to an intensive care unit (ICU) with severe pneumonia of any etiology (viral, bacterial, fungal, or mixed), with and without trauma based on clinical suspicion
• Acute hypoxemic respiratory failure (AHRF)
• Evidence of moderate to severe acute respiratory distress syndrome (ARDS) based on Global ARDS criteria
• Onset of severe pneumonia with AHRF ≤7 days prior to informed consent

Key Exclusion Criteria:

• More than two vasopressors to maintain a mean arterial pressure ≥65 millimeters of mercury at the time of informed consent
• Pregnancy or breastfeeding
• History of cytokine release syndrome, as documented in the medical record or reported by the participant, legally authorized representative, or close relative
• Current participation in another interventional clinical trial, or receipt of an investigational medicinal product within 30 days prior to screening, unless reviewed and approved in writing by the medical monitor

Note: Other protocol-defined inclusion/exclusion criteria may apply.

The Run-in Phase is open label and non-randomized, Phase 2 is double blind and randomized.