The main aim of the study is to investigate the plasma pharmacokinetics (PK) and safety of intravenous (IV) administration of a single dose of 400 milligrams (mg) or 600 mg RO7223280 in critically ill participants with bacterial infections.

Inclusion Criteria:

• Illness requiring treatment in an intensive care unit (ICU) at the time of enrolment

• Ongoing clinical syndrome meeting at least one of the following criteria:

  1. HABP: bacterial pneumonia diagnosed after more than 48 hours of hospitalization or within 7 days after a hospital discharge
  2. Ventilator-associated bacterial pneumonia (VABP): bacterial pneumonia diagnosed after more than 48 hours of mechanical ventilation or within 72 hours after weaning
  3. Bacteremia confirmed by the presence of a bacterial pathogen in a blood culture drawn within 7 days prior to dosing and with the defined focus of infection.
  4. For Cohort 4 only: mechanically ventilated participants who have a BAL procedure planned as part of routine practice for a day that can function as Day 1.

Exclusion Criteria:

• Ongoing documented catheter-related bacteraemia as the sole ongoing infection
• Major surgery within 48 hours prior to dosing or major surgery expected within 48 hours after the start of the infusion
• Known chronic severe hepatic impairment (Child-Pugh class C). Note: acute severe hepatic impairment is not exclusionary

Qualified researchers may request access to individual patient level data through the clinical study data request platform (www.vivli.org). Further details on Roche's criteria for eligible studies are available here (https://vivli.org/ourmember/roche/). For further details on Roche's Global Policy on the Sharing of Clinical Information and how to request access to related clinical study documents, see here (https://www.roche.com/innovation/process/clinical -trials/data-sharing/).