The purpose of this study is to find out if the experimental drug called tozorakimab is safe and effective in treating severe viral lung infections with Acute Respiratory Failure (ARF), and also to better understand the studied disease and associated health problems. Participants will receive a single dose that will be administered via IV injection followed by participants’ vital signs and WHO Clinical Progression Scale will be assessed and recorded once daily during hospitalization. Post discharge, the participants will be contacted via phone at Day 14 and Day 28 and then visit the site for final assessments on Day 60.

1. Inclusion
   1. Adult participants ≥ 18 years old at the time of signing the ICF.
   2. Patients hospitalized with viral lung infection.
   3. Hypoxaemia requiring treatment with supplemental O2. Hypoxaemia is defined as:

      − SpO2 ≤ 90% OR

      − SpO2 ≤ 92% AND one or both of the following:

      o Radiographic infiltrates by Chest X-ray/CT scan compatible with viral lung infection per investigator judgement.

      o Use of accessory muscles of respiration or respiratory rate > 22/minute.

   4. ≤ 36 hours since admission to hospital. Refer to Section 4.1.2 for more details.
   5. ≤ 14 days since onset of respiratory viral infection symptoms.
2. Exclusion
   1. Known fungal or parasitic lung infection, aspiration lung infection, lung abscess, or evidence of septic shock. Bacterial co-infection is allowed, unless, in the opinion of the investigator, bacterial infection defines the severity of the participant’s condition.
   2. Hypoxaemia caused primarily by extrapulmonary insult or by lung injury of noninfective aetiology (eg, trauma, chemical injury, etc).
   3. Ongoing IMV/ECMO at randomization.
   4. Any comorbid condition that, in the opinion of the investigator, is likely to result in death within 3 months from randomization.
   5. Anticipated recovery and discharge from the hospital within 24 hours of randomization.
   6. Active tuberculosis defined as disease requiring current treatment.
   7. Known unstable cardiovascular disease (eg, chronic heart failure NYHA Class IV, recent myocardial infarction or stroke within 3 months, uncontrolled ventricular arrhythmia, or cardiogenic pulmonary oedema, which is driving the severity of the hypoxaemia, that in the investigator’s judgement may put the participant at risk or negatively affect the outcome of the study).
   8. Known absolute neutrophil count ≤ 1.0 x 109 /L.
   9. Known untreated HIV. Known history of active hepatitis B or C (treated and controlled hepatitis and HIV are allowed).
   10. Known history of active severe inflammatory bowel disease or colitis (including Crohn’s disease or ulcerative colitis).
   11. The following malignancies:
       1. Solid tumours with metastases (Stage IV).
       2. Lymphoma/leukaemia not in complete remission.
       3. Malignancies treated with chemotherapy and/or immunomodulatory drugs within the past 2 months.
   12. Transplant patients at risk of organ rejection, or those on long-term immunosuppressive treatment for the transplant. Treatment with corticosteroids is allowed.
   13. Any disorder that is not stable in the opinion of the investigator, including but not limited to cardiovascular, gastrointestinal, hepatic, renal, neurological, musculoskeletal, infectious (including risk factors for viral lung infection), endocrine, metabolic, haematological, immune, psychiatric, or major physical impairment and could:
       1. affect the safety of the participant throughout the study,
       2. influence the findings of the study or their interpretation,
       3. impede the participant’s ability to complete the entire duration of the study.
   14. Use of long-term oxygen therapy for pre-existing conditions.
   15. Chronic treatment with TNF inhibitors, Janus kinase inhibitors or interferon-gamma. Wash-out period of 4 weeks or 5 half-lives (whichever is longer) is required prior to enrollment.
   16. Current treatment with any investigational medication. Wash-out period of 4 weeks or 5 half-lives (whichever is longer) is required prior to enrolment.
   17. Participants who have previously received tozorakimab.
   18. Known history of:
       1. anaphylaxis to any biologic therapy,
       2. severe reaction to any medication, including biologic agents or human gamma globulin therapy,allergy or reaction to any component of the study intervention formulation.
   19. Pregnant and lactating participants.
   20. Male participants who are sexually active with a FOCBP and participants that are FOCBP who are sexually active with a male partner, unless they agree to use highly effective contraceptive methods from enrolment throughout the study and until at least 14 weeks after last dose of IP.
   21. Inability of the participant to understand and/or comply with study procedures and/or attend all telephone calls and follow-up visit in the opinion of the investigator.