* massive confirmed pulmonary embolism (pe) with haemodynamic instability at trial entry, or any (suspected or confirmed) pe that is expected to require therapeutic dosages of anticoagulants during the treatment period * indication for therapeutic dosages of anticoagulants at trial entry * patients on mechanical ventilation for longer than 48 hours * chronic pulmonary disease i.e. with known forced expiratory volume in 1 second (fev1) \<50%, requiring home oxygen, or oral steroid therapy or hospitalisation for exacerbation within 12 months, or significant chronic pulmonary disease in the investigator's opinion, or primary pulmonary arterial hypertension * has a do-not-intubate (dni) or do-not-resuscitate (dnr) order * in the opinion of the investigator not expected to survive for \> 48 hours after admission * planned interventions during the first 5 days after randomisation, such as surgery, insertion of central catheter or arterial line, drains, etc. * patients with known hypersensitivity to the active substance alteplase, gentamicin (a trace residue from the manufacturing process) or to any of the excipients * significant bleeding disorder at present or within the past 3 months, known haemorrhagic diathesis * patients receiving effective oral anticoagulant treatment, e.g. vitamin k antagonists with international normalised ratio (inr) \>1.3, or any direct oral anticoagulant within the past 48 hours further exclusion criteria apply.

* massive confirmed pulmonary embolism (pe) with haemodynamic instability at trial entry, or any (suspected or confirmed) pe that is expected to require therapeutic dosages of anticoagulants during the treatment period * indication for therapeutic dosages of anticoagulants at trial entry * patients on mechanical ventilation for longer than 48 hours * chronic pulmonary disease i.e. with known forced expiratory volume in 1 second (fev1) \<50%, requiring home oxygen, or oral steroid therapy or hospitalisation for exacerbation within 12 months, or significant chronic pulmonary disease in the investigator's opinion, or primary pulmonary arterial hypertension * has a do-not-intubate (dni) or do-not-resuscitate (dnr) order * in the opinion of the investigator not expected to survive for \> 48 hours after admission * planned interventions during the first 5 days after randomisation, such as surgery, insertion of central catheter or arterial line, drains, etc. * patients with known hypersensitivity to the active substance alteplase, gentamicin (a trace residue from the manufacturing process) or to any of the excipients * significant bleeding disorder at present or within the past 3 months, known haemorrhagic diathesis * patients receiving effective oral anticoagulant treatment, e.g. vitamin k antagonists with international normalised ratio (inr) \>1.3, or any direct oral anticoagulant within the past 48 hours further exclusion criteria apply.

massive confirmed pulmonary embolism (pe) with haemodynamic instability at trial entry, or any (suspected or confirmed) pe that is expected to require therapeutic dosages of anticoagulants during the treatment period indication for therapeutic dosages of anticoagulants at trial entry patients on mechanical ventilation for longer than 48 hours chronic pulmonary disease i.e. with known forced expiratory volume in 1 second (fev1) <50%, requiring home oxygen, or oral steroid therapy or hospitalisation for exacerbation within 12 months, or significant chronic pulmonary disease in the investigator's opinion, or primary pulmonary arterial hypertension has a do-not-intubate (dni) or do-not-resuscitate (dnr) order in the opinion of the investigator not expected to survive for > 48 hours after admission planned interventions during the first 5 days after randomisation, such as surgery, insertion of central catheter or arterial line, drains, etc. patients with known hypersensitivity to the active substance alteplase, gentamicin (a trace residue from the manufacturing process) or to any of the excipients significant bleeding disorder at present or within the past 3 months, known haemorrhagic diathesis patients receiving effective oral anticoagulant treatment, e.g. vitamin k antagonists with international normalised ratio (inr) >1.3, or any direct oral anticoagulant within the past 48 hours further exclusion criteria apply.

massive confirmed pulmonary embolism (pe) with haemodynamic instability at trial entry, or any (suspected or confirmed) pe that is expected to require therapeutic dosages of anticoagulants during the treatment period indication for therapeutic dosages of anticoagulants at trial entry patients on mechanical ventilation for longer than 48 hours chronic pulmonary disease i.e. with known forced expiratory volume in 1 second (fev1) <50%, requiring home oxygen, or oral steroid therapy or hospitalisation for exacerbation within 12 months, or significant chronic pulmonary disease in the investigator's opinion, or primary pulmonary arterial hypertension has a do-not-intubate (dni) or do-not-resuscitate (dnr) order in the opinion of the investigator not expected to survive for > 48 hours after admission planned interventions during the first 5 days after randomisation, such as surgery, insertion of central catheter or arterial line, drains, etc. patients with known hypersensitivity to the active substance alteplase, gentamicin (a trace residue from the manufacturing process) or to any of the excipients significant bleeding disorder at present or within the past 3 months, known haemorrhagic diathesis patients receiving effective oral anticoagulant treatment, e.g. vitamin k antagonists with international normalised ratio (inr) >1.3, or any direct oral anticoagulant within the past 48 hours further exclusion criteria apply.

- massive confirmed pulmonary embolism (pe) with haemodynamic instability at trial entry - indication for therapeutic dosages of anticoagulants at trial entry - patients on mechanical ventilation for longer than 48 hours - chronic pulmonary disease i.e. with known forced expiratory volume in 1 second (fev1) <50%, requiring home oxygen, or oral steroid therapy or hospitalisation for exacerbation within 12 months, or significant chronic pulmonary disease in the investigator's opinion, or primary pulmonary arterial hypertension - has a do-not-intubate (dni) or do-not-resuscitate (dnr) order - in the opinion of the investigator not expected to survive for > 48 hours after admission - planned interventions during the first 5 days after randomisation, such as surgery, insertion of central catheter or arterial line, drains, etc. - patients with known hypersensitivity to the active substance alteplase, gentamicin (a trace residue from the manufacturing process) or to any of the excipients - significant bleeding disorder at present or within the past 3 months, known haemorrhagic diathesis - patients receiving effective oral anticoagulant treatment, e.g. vitamin k antagonists with international normalised ratio (inr) >1.3, or any direct oral anticoagulant within the past 48 hours further exclusion criteria apply.

- massive confirmed pulmonary embolism (pe) with haemodynamic instability at trial entry - indication for therapeutic dosages of anticoagulants at trial entry - patients on mechanical ventilation for longer than 48 hours - chronic pulmonary disease i.e. with known forced expiratory volume in 1 second (fev1) <50%, requiring home oxygen, or oral steroid therapy or hospitalisation for exacerbation within 12 months, or significant chronic pulmonary disease in the investigator's opinion, or primary pulmonary arterial hypertension - has a do-not-intubate (dni) or do-not-resuscitate (dnr) order - in the opinion of the investigator not expected to survive for > 48 hours after admission - planned interventions during the first 5 days after randomisation, such as surgery, insertion of central catheter or arterial line, drains, etc. - patients with known hypersensitivity to the active substance alteplase, gentamicin (a trace residue from the manufacturing process) or to any of the excipients - significant bleeding disorder at present or within the past 3 months, known haemorrhagic diathesis - patients receiving effective oral anticoagulant treatment, e.g. vitamin k antagonists with international normalised ratio (inr) >1.3, or any direct oral anticoagulant within the past 48 hours further exclusion criteria apply.

- massive confirmed pulmonary embolism (pe) with haemodynamic instability at trial entry - patients on mechanical ventilation for longer than 48 hours - chronic pulmonary disease i.e. with known forced expiratory volume in 1 second (fev1) <50%, requiring home oxygen, or oral steroid therapy or hospitalisation for exacerbation within 12 months, or significant chronic pulmonary disease in the investigator's opinion, or primary pulmonary arterial hypertension - has a do-not-intubate (dni) or do-not-resuscitate (dnr) order - in the opinion of the investigator not expected to survive for > 48 hours after admission - patients with known hypersensitivity to the active substance alteplase, gentamicin (a trace residue from the manufacturing process) or to any of the excipients - significant bleeding disorder at present or within the past 3 months, known haemorrhagic diathesis - patients receiving effective oral anticoagulant treatment, e.g. vitamin k antagonists with international normalised ratio (inr) >1.3, or any direct oral anticoagulant within the past 48 hours further exclusion criteria apply.

- massive confirmed pulmonary embolism (pe) with haemodynamic instability at trial entry - patients on mechanical ventilation for longer than 48 hours - chronic pulmonary disease i.e. with known forced expiratory volume in 1 second (fev1) <50%, requiring home oxygen, or oral steroid therapy or hospitalisation for exacerbation within 12 months, or significant chronic pulmonary disease in the investigator's opinion, or primary pulmonary arterial hypertension - has a do-not-intubate (dni) or do-not-resuscitate (dnr) order - in the opinion of the investigator not expected to survive for > 48 hours after admission - patients with known hypersensitivity to the active substance alteplase, gentamicin (a trace residue from the manufacturing process) or to any of the excipients - significant bleeding disorder at present or within the past 3 months, known haemorrhagic diathesis - patients receiving effective oral anticoagulant treatment, e.g. vitamin k antagonists with international normalised ratio (inr) >1.3, or any direct oral anticoagulant within the past 48 hours further exclusion criteria apply.

- massive confirmed pe with haemodynamic instability at trial entry - patients on mechanical ventilation for longer than 48 hours - chronic pulmonary disease i.e. with known fev1 <50%, requiring home oxygen, or oral steroid therapy or hospitalisation for exacerbation within 12 months, or significant chronic pulmonary disease in the investigator's opinion, or primary pulmonary arterial hypertension - has a do-not-intubate (dni) or do-not-resuscitate (dnr) order - in the opinion of the investigator not expected to survive for > 48 hours after admission - patients with known hypersensitivity to the active substance alteplase, gentamicin (a trace residue from the manufacturing process) or to any of the excipients - significant bleeding disorder at present or within the past 3 months, known haemorrhagic diathesis - patients receiving effective oral anticoagulant treatment, e.g. vitamin k antagonists with international normalised ratio (inr) >1.3, or any direct oral anticoagulant within the past 48 hours further exclusion criteria apply.

- massive confirmed pe with haemodynamic instability at trial entry - patients on mechanical ventilation for longer than 48 hours - chronic pulmonary disease i.e. with known fev1 <50%, requiring home oxygen, or oral steroid therapy or hospitalisation for exacerbation within 12 months, or significant chronic pulmonary disease in the investigator's opinion, or primary pulmonary arterial hypertension - has a do-not-intubate (dni) or do-not-resuscitate (dnr) order - in the opinion of the investigator not expected to survive for > 48 hours after admission - patients with known hypersensitivity to the active substance alteplase, gentamicin (a trace residue from the manufacturing process) or to any of the excipients - significant bleeding disorder at present or within the past 3 months, known haemorrhagic diathesis - patients receiving effective oral anticoagulant treatment, e.g. vitamin k antagonists with international normalised ratio (inr) >1.3, or any direct oral anticoagulant within the past 48 hours further exclusion criteria apply.