* onset of covid-19 pneumonia symptoms (i.e. dyspnea/respiratory insufficiency) \>14 days * on mechanical ventilation at the time of randomization * a pao2/fio2 \< 100 mmhg * uncontrolled systemic infection (other than covid-19) * hypersensitivity to the active substance or to any of the excipients of the experimental drug * total neutrophil count \< 1500/mm3 * severe hepatic cirrhosis * history of chronic hbv or hcv infection * known or active tuberculosis (tb) or a history of incompletely treated tb; suspected or known extrapulmonary tuberculosis * moderate/severe heart failure (nyha class 3 or 4) * any prior (within the defined periods below) or concurrent use of immunosuppressive therapies including but not limited to the following: 1. anti-il-6, anti-il-6r antagonists or janus kinase inhibitors (jaki) in the past 30 days or plans to receive during the study period; 2. cell-depleting agents (e.g., anti cd20) without evidence of recovery of b cells to baseline level; 3. anakinra within 1 week of baseline; canakinumab within 8 weeks of baseline; abatacept within 8 weeks of baseline. 4. tumor necrosis factor (tnf) inhibitors within 2-8 weeks (etanercept within 2 weeks, infliximab, certolizumab, golimumab, or adalimumab within 8 weeks), or after at least 5 half-lives have elapsed, whichever is longer; 5. alkylating agents including cyclophosphamide (cyc) within 6 months of baseline; 6. cyclosporine (csa), azathioprine (aza) or mycophenolate mofetil (mmf) or leflunomide or methotrexate within 4 weeks of baseline. * pregnancy or lactation (note: women of childbearing age should use effective contraception/abstinence after treatment with mavrilimumab and for 3 months after the dosing) * any serious medical condition or abnormality of clinical laboratory tests that, in the investigator's judgment, precludes the patient's safe participation in and completion of the study * in the opinion of the investigator, progression to death is imminent and highly likely within the next 24 hours, irrespective of the provision of treatments * current participation in any other interventional investigational trials

* onset of covid-19 pneumonia symptoms (i.e. dyspnea/respiratory insufficiency) \>14 days * on mechanical ventilation at the time of randomization * a pao2/fio2 \< 100 mmhg * uncontrolled systemic infection (other than covid-19) * hypersensitivity to the active substance or to any of the excipients of the experimental drug * total neutrophil count \< 1500/mm3 * severe hepatic cirrhosis * history of chronic hbv or hcv infection * known or active tuberculosis (tb) or a history of incompletely treated tb; suspected or known extrapulmonary tuberculosis * moderate/severe heart failure (nyha class 3 or 4) * any prior (within the defined periods below) or concurrent use of immunosuppressive therapies including but not limited to the following: 1. anti-il-6, anti-il-6r antagonists or janus kinase inhibitors (jaki) in the past 30 days or plans to receive during the study period; 2. cell-depleting agents (e.g., anti cd20) without evidence of recovery of b cells to baseline level; 3. anakinra within 1 week of baseline; canakinumab within 8 weeks of baseline; abatacept within 8 weeks of baseline. 4. tumor necrosis factor (tnf) inhibitors within 2-8 weeks (etanercept within 2 weeks, infliximab, certolizumab, golimumab, or adalimumab within 8 weeks), or after at least 5 half-lives have elapsed, whichever is longer; 5. alkylating agents including cyclophosphamide (cyc) within 6 months of baseline; 6. cyclosporine (csa), azathioprine (aza) or mycophenolate mofetil (mmf) or leflunomide or methotrexate within 4 weeks of baseline. * pregnancy or lactation (note: women of childbearing age should use effective contraception/abstinence after treatment with mavrilimumab and for 3 months after the dosing) * any serious medical condition or abnormality of clinical laboratory tests that, in the investigator's judgment, precludes the patient's safe participation in and completion of the study * in the opinion of the investigator, progression to death is imminent and highly likely within the next 24 hours, irrespective of the provision of treatments * current participation in any other interventional investigational trials

onset of covid-19 pneumonia symptoms (i.e. dyspnea/respiratory insufficiency) >14 days on mechanical ventilation at the time of randomization a pao2/fio2 < 100 mmhg uncontrolled systemic infection (other than covid-19) hypersensitivity to the active substance or to any of the excipients of the experimental drug total neutrophil count < 1500/mm3 severe hepatic cirrhosis history of chronic hbv or hcv infection known or active tuberculosis (tb) or a history of incompletely treated tb; suspected or known extrapulmonary tuberculosis moderate/severe heart failure (nyha class 3 or 4) any prior (within the defined periods below) or concurrent use of immunosuppressive therapies including but not limited to the following: anti-il-6, anti-il-6r antagonists or janus kinase inhibitors (jaki) in the past 30 days or plans to receive during the study period; cell-depleting agents (e.g., anti cd20) without evidence of recovery of b cells to baseline level; anakinra within 1 week of baseline; canakinumab within 8 weeks of baseline; abatacept within 8 weeks of baseline. tumor necrosis factor (tnf) inhibitors within 2-8 weeks (etanercept within 2 weeks, infliximab, certolizumab, golimumab, or adalimumab within 8 weeks), or after at least 5 half-lives have elapsed, whichever is longer; alkylating agents including cyclophosphamide (cyc) within 6 months of baseline; cyclosporine (csa), azathioprine (aza) or mycophenolate mofetil (mmf) or leflunomide or methotrexate within 4 weeks of baseline. pregnancy or lactation (note: women of childbearing age should use effective contraception/abstinence after treatment with mavrilimumab and for 3 months after the dosing) any serious medical condition or abnormality of clinical laboratory tests that, in the investigator's judgment, precludes the patient's safe participation in and completion of the study in the opinion of the investigator, progression to death is imminent and highly likely within the next 24 hours, irrespective of the provision of treatments current participation in any other interventional investigational trials

onset of covid-19 pneumonia symptoms (i.e. dyspnea/respiratory insufficiency) >14 days on mechanical ventilation at the time of randomization a pao2/fio2 < 100 mmhg uncontrolled systemic infection (other than covid-19) hypersensitivity to the active substance or to any of the excipients of the experimental drug total neutrophil count < 1500/mm3 severe hepatic cirrhosis history of chronic hbv or hcv infection known or active tuberculosis (tb) or a history of incompletely treated tb; suspected or known extrapulmonary tuberculosis moderate/severe heart failure (nyha class 3 or 4) any prior (within the defined periods below) or concurrent use of immunosuppressive therapies including but not limited to the following: anti-il-6, anti-il-6r antagonists or janus kinase inhibitors (jaki) in the past 30 days or plans to receive during the study period; cell-depleting agents (e.g., anti cd20) without evidence of recovery of b cells to baseline level; anakinra within 1 week of baseline; canakinumab within 8 weeks of baseline; abatacept within 8 weeks of baseline. tumor necrosis factor (tnf) inhibitors within 2-8 weeks (etanercept within 2 weeks, infliximab, certolizumab, golimumab, or adalimumab within 8 weeks), or after at least 5 half-lives have elapsed, whichever is longer; alkylating agents including cyclophosphamide (cyc) within 6 months of baseline; cyclosporine (csa), azathioprine (aza) or mycophenolate mofetil (mmf) or leflunomide or methotrexate within 4 weeks of baseline. pregnancy or lactation (note: women of childbearing age should use effective contraception/abstinence after treatment with mavrilimumab and for 3 months after the dosing) any serious medical condition or abnormality of clinical laboratory tests that, in the investigator's judgment, precludes the patient's safe participation in and completion of the study in the opinion of the investigator, progression to death is imminent and highly likely within the next 24 hours, irrespective of the provision of treatments current participation in any other interventional investigational trials

- onset of covid-19 pneumonia symptoms (i.e. dyspnea/respiratory insufficiency) >14 days - on mechanical ventilation at the time of randomization - a pao2/fio2 < 100 mmhg - uncontrolled systemic infection (other than covid-19) - hypersensitivity to the active substance or to any of the excipients of the experimental drug - total neutrophil count < 1500/mm3 - severe hepatic cirrhosis - history of chronic hbv or hcv infection - known or active tuberculosis (tb) or a history of incompletely treated tb; suspected or known extrapulmonary tuberculosis - moderate/severe heart failure (nyha class 3 or 4) - any prior (within the defined periods below) or concurrent use of immunosuppressive therapies including but not limited to the following: 1. anti-il-6, anti-il-6r antagonists or janus kinase inhibitors (jaki) in the past 30 days or plans to receive during the study period; 2. cell-depleting agents (e.g., anti cd20) without evidence of recovery of b cells to baseline level; 3. anakinra within 1 week of baseline; canakinumab within 8 weeks of baseline; abatacept within 8 weeks of baseline. 4. tumor necrosis factor (tnf) inhibitors within 2-8 weeks (etanercept within 2 weeks, infliximab, certolizumab, golimumab, or adalimumab within 8 weeks), or after at least 5 half-lives have elapsed, whichever is longer; 5. alkylating agents including cyclophosphamide (cyc) within 6 months of baseline; 6. cyclosporine (csa), azathioprine (aza) or mycophenolate mofetil (mmf) or leflunomide or methotrexate within 4 weeks of baseline. - pregnancy or lactation (note: women of childbearing age should use effective contraception/abstinence after treatment with mavrilimumab and for 3 months after the dosing) - any serious medical condition or abnormality of clinical laboratory tests that, in the investigator's judgment, precludes the patient's safe participation in and completion of the study - in the opinion of the investigator, progression to death is imminent and highly likely within the next 24 hours, irrespective of the provision of treatments - current participation in any other interventional investigational trials

- onset of covid-19 pneumonia symptoms (i.e. dyspnea/respiratory insufficiency) >14 days - on mechanical ventilation at the time of randomization - a pao2/fio2 < 100 mmhg - uncontrolled systemic infection (other than covid-19) - hypersensitivity to the active substance or to any of the excipients of the experimental drug - total neutrophil count < 1500/mm3 - severe hepatic cirrhosis - history of chronic hbv or hcv infection - known or active tuberculosis (tb) or a history of incompletely treated tb; suspected or known extrapulmonary tuberculosis - moderate/severe heart failure (nyha class 3 or 4) - any prior (within the defined periods below) or concurrent use of immunosuppressive therapies including but not limited to the following: 1. anti-il-6, anti-il-6r antagonists or janus kinase inhibitors (jaki) in the past 30 days or plans to receive during the study period; 2. cell-depleting agents (e.g., anti cd20) without evidence of recovery of b cells to baseline level; 3. anakinra within 1 week of baseline; canakinumab within 8 weeks of baseline; abatacept within 8 weeks of baseline. 4. tumor necrosis factor (tnf) inhibitors within 2-8 weeks (etanercept within 2 weeks, infliximab, certolizumab, golimumab, or adalimumab within 8 weeks), or after at least 5 half-lives have elapsed, whichever is longer; 5. alkylating agents including cyclophosphamide (cyc) within 6 months of baseline; 6. cyclosporine (csa), azathioprine (aza) or mycophenolate mofetil (mmf) or leflunomide or methotrexate within 4 weeks of baseline. - pregnancy or lactation (note: women of childbearing age should use effective contraception/abstinence after treatment with mavrilimumab and for 3 months after the dosing) - any serious medical condition or abnormality of clinical laboratory tests that, in the investigator's judgment, precludes the patient's safe participation in and completion of the study - in the opinion of the investigator, progression to death is imminent and highly likely within the next 24 hours, irrespective of the provision of treatments - current participation in any other interventional investigational trials