Development of tenecteplase for stroke thrombolysis: Japan’s endeavor

Intravenous thrombolysis for acute ischemic stroke is strongly recommended based on high-level evidence. However, the efficacy of the currently approved drug, alteplase, is not necessarily sufficient. Thrombolysis can trigger intracranial hemorrhage, that is a critical issue that cannot be overlooked, especially for Asians, who are generally hypertensive and prone to bleeding, making strict blood pressure control essential. Based on clinical trial results of a new thrombolytic agent, tenecteplase, several guidelines now recommend its use, and the off-label use has become common in many countries. As of 2024, regulatory approval has been granted in Western countries. Approval is also expected in major Asian countries between 2025 and 2026. In Japan, approval requires clinical data specific to Japanese patients, but no domestic pharmaceutical company currently handles the drug. We are conducting an investigator-initiated, multicenter, prospective, randomized, open-label, masked-endpoint, superiority trial, T-FLAVOR, comparing tenecteplase at 0.25 mg/kg (international standard dose) with alteplase at 0.6 mg/kg (a unique low dose approved in Japan). The target population consists of patients with ischemic stroke due to large vessel occlusion within 4.5 h of onset, who are also eligible for mechanical thrombectomy within 6 h. The primary efficacy outcome is successful early reperfusion assessed via catheter angiography after drug administration. Enrollment of the planned 220 participants was complete, and results are expected to be published in 2025. This is the only clinical trial using tenecteplase in Japan and the world's first to directly compare tenecteplase and low-dose alteplase (0.6 mg/kg).