Reduced-Dose Versus Full-Dose Alteplase for High-Risk Pulmonary Embolism (REDSTEM)

High-risk pulmonary embolism is a life-threatening condition requiring immediate reperfusion therapy. Full-dose systemic thrombolysis is recommended as first-line treatment, but its use is limited by the risk of major bleeding, including intracranial hemorrhage. Reduced-dose systemic thrombolysis may reduce bleeding while maintaining clinical efficacy, but this strategy has not been adequately evaluated in patients with high-risk pulmonary embolism. REDSTEM is an international, multicenter, randomized, adaptive, open-label, blinded-endpoint phase 4 trial comparing reduced-dose alteplase with standard full-dose alteplase in adults with acute high-risk pulmonary embolism. The trial will assess whether reduced-dose alteplase preserves early clinical efficacy while reducing severe clinically significant bleeding. Participants will be followed for up to 12 months.

• Incidence of composite efficacy endpoint
• Key secondary endpoint - Incidence of severe clinically significant bleeding

1. Study completion expected

   Jan 31, 2031

2. Primary completion expected

   Jan 31, 2030

3. Expected to start

   Dec 1, 2026

4. Last registry update

   Oct 28, 2026

5. Registered

   Sep 14, 2026