Inclusion criteria phase II and III:  ≥ 18 years old, males and females Signed and dated written informed consent in accordance with International Council on Harmonisation - Good Clinical Practice (ICH-GCP) and local legislation prior to admission to the trial Documentation of laboratory-confirmed Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, as determined by a molecular test (antigen or nucleic acid) from any respiratory tract specimen (nasopharyngeal (NP) or nasal swab or saliva) collected no more than 72 hours prior to start of treatment Patients experienced mild to moderate Coronavirus Disease 2019 (COVID-19)-related symptoms or measured fever for no more than 5 days prior to start of treatment where symptoms are defined by fever, feeling feverish, fatigue, cough, shortness of breath at rest or during activity, sore throat, body pain or muscle pain/ aches, chills, headache, nasal obstruction or congestion, loss of smell or taste, nausea, diarrhea, vomiting, or dysgeusia One or more of the following signs/symptoms present on day of start of treatment: fever, feeling feverish, fatigue, cough, shortness of breath at rest or during activity, sore throat, body pain or muscle pain/ aches, chills, headache, nasal obstruction or congestion, loss of smell or taste, nausea, diarrhea, vomiting, or dysgeusia Women of childbearing potential (WOCBP) and men able to father a child must be ready and able to use highly effective methods of birth control per ICH M3 (R2) that result in a low failure rate of less than 1% per year when used consistently and correctly  Exclusion criteria phase II and III:  Body weight of less than 40 kg  Severe or critical COVID-19 including at least one of  Oxygen saturation (SpO2) ≤ 93 % on room air or on their usual level of oxygen supplementation in case of chronic oxygen use Ratio of arterial oxygen partial pressure (PaO2 in millimeters of mercury) to fractional inspired oxygen (FiO2) < 300 (in case arterial blood sample was taken) History of hospitalization for COVID-19 Current or imminent need for hospitalization or immediate medical attention in the clinical opinion of the site investigator. Does not include patients hospitalized for isolation only Receipt of intravenous immunoglobulin within 12 weeks prior to Visit 2 Receipt of COVID-19 convalescent plasma treatment at any time prior to Visit 2 Receipt of any SARS-CoV-2 monoclonal antibody treatment at any time prior to Visit 2 Receipt of SARS-CoV-2 vaccine at any time prior to Visit 2 Receipt of an investigational product for COVID-19 within 5 half-lives prior to Visit 2 Receipt of systemic steroids (e.g. prednisone, dexamethasone) within 4 weeks prior to Visit 2 unless used for chronic condition Further exclusion criteria apply.  Exclusion criterion phase III only:  - Previous enrolment in this trial. Patients participating in Phase II are not eligible for Phase III. Re-screening is allowed once, for repeat of Quantitative Reverse Transcription Polymerase chain reaction (RT-qPCR) or antigen SARS-CoV-2 test, if required. The test method used for initial screening (RT-qPCR or antigen) should be used for re-screening.