1. Massive confirmed 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 2. Indication for therapeutic dosages of anticoagulants at trial entry 3. Mechanical ventilation for longer than 48 hours 4. 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 5. Has a Do-Not-Intubate (DNI) or Do-Not-Resuscitate (DNR) order 6. In the opinion of the investigator not expected to survive for > 48 hours after screening. 7. Planned interventions during the first 5 days after randomization, such as surgery, insertion of central catheter or arterial line, drains, etc. 8. Known hypersensitivity to the active substance alteplase, gentamicin (a trace residue from the manufacturing process) or to any of the excipients 9. Significant bleeding disorder at present or within the past 6 months, known haemorrhagic diathesis 10. Patients receiving effective oral anticoagulant treatment, e.g. vitamin K antagonists with INR >1.3, or any direct oral anticoagulant within the past 48 hours 11. Any history of central nervous system damage (i.e. neoplasm, aneurysm, intracranial or spinal surgery) 12. History or evidence or suspicion of intracranial haemorrhage including sub-arachnoid haemorrhage 13. Severe uncontrolled arterial hypertension (according to the investigator`s judgement) 14. Major surgery or significant trauma in the past 10 days, recent trauma to head or cranium 15. Cardiac arrest and/or cardiopulmonary resuscitation during the current hospital stay 16. Obstetrical delivery within the past 10 days 17. Severe hepatic dysfunction i.e. Child-Pugh B and C, including biopsy confirmed hepatic cirrhosis, portal hypertension, hepatic encephalopathy, or active hepatitis 18. Bacterial endocarditis, pericarditis 19. Acute pancreatitis 20. Documented ulcerative gastro-intestinal disease during the last 3 months 21. Severe heart failure (New York Heart Association Class IV) 22. Arterial aneurysms, arterial/venous malformations 23. Malignancy (Stage IV) with increased bleeding risk Further criteria apply.

1. Massive confirmed 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 2. Indication for therapeutic dosages of anticoagulants at trial entry 3. Mechanical ventilation for longer than 48 hours 4. 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 5. Has a Do-Not-Intubate (DNI) or Do-Not-Resuscitate (DNR) order 6. In the opinion of the investigator not expected to survive for > 48 hours after screening. 7. Planned interventions during the first 5 days after randomization, such as surgery, insertion of central catheter or arterial line, drains, etc. 8. Known hypersensitivity to the active substance alteplase, gentamicin (a trace residue from the manufacturing process) or to any of the excipients 9. Significant bleeding disorder at present or within the past 6 months, known haemorrhagic diathesis 10. Patients receiving effective oral anticoagulant treatment, e.g. vitamin K antagonists with INR >1.3, or any direct oral anticoagulant within the past 48 hours 11. Any history of central nervous system damage (i.e. neoplasm, aneurysm, intracranial or spinal surgery) 12. History or evidence or suspicion of intracranial haemorrhage including sub-arachnoid haemorrhage 13. Severe uncontrolled arterial hypertension (according to the investigator`s judgement) 14. Major surgery or significant trauma in the past 10 days, recent trauma to head or cranium 15. Cardiac arrest and/or cardiopulmonary resuscitation during the current hospital stay 16. Obstetrical delivery within the past 10 days 17. Severe hepatic dysfunction i.e. Child-Pugh B and C, including biopsy confirmed hepatic cirrhosis, portal hypertension, hepatic encephalopathy, or active hepatitis 18. Bacterial endocarditis, pericarditis 19. Acute pancreatitis 20. Documented ulcerative gastro-intestinal disease during the last 3 months 21. Severe heart failure (New York Heart Association Class IV) 22. Arterial aneurysms, arterial/venous malformations 23. Malignancy (Stage IV) with increased bleeding risk Further criteria apply.