Tenecteplase (TNKase)

Tenecteplase is a real, FDA-approved third-generation variant of alteplase — approved for heart attack in 2000 on a 17,000-patient trial showing it matched alteplase's survival benefit with less bleeding and a single five-second bolus instead of an hour-long infusion, and in March 2025 it became the first new FDA-approved acute-stroke medicine in nearly three decades, formalizing years of guideline-endorsed, off-label use.

A triple mutation engineered for a single bolus

Tenecteplase is alteplase with three targeted amino-acid substitutions engineered into it: changes that slow its clearance from the bloodstream, increase its specificity for fibrin (reducing bleeding elsewhere in the body), and make it far more resistant to the body's own natural inhibitor of tPA, plasminogen activator inhibitor-1 (PAI-1). Genentech built it specifically to allow single-bolus dosing — one weight-based injection given over about five seconds — instead of alteplase's bolus-plus-60-to-90-minute-infusion regimen, a genuine practical advantage in emergency and prehospital settings where every minute spent preparing an infusion delays treatment.

ASSENT-2: matching alteplase's survival benefit, with an easier dose

The FDA approved tenecteplase (as TNKase) on 2 June 2000 for acute myocardial infarction, based on the ASSENT-2 trial (Assessment of the Safety and Efficacy of a New Thrombolytic Investigators, "Single-Bolus Tenecteplase Compared with Front-Loaded Alteplase in Acute Myocardial Infarction: The ASSENT-2 Double-Blind Randomised Trial," Lancet 1999;354(9180):716-722, PMID 10475182): 16,949 patients randomized to single-bolus tenecteplase or accelerated alteplase found near-identical 30-day mortality (6.18% vs. 6.15%), while tenecteplase produced significantly fewer non-cerebral bleeding complications and required fewer blood transfusions. The trial established tenecteplase as at least as effective as alteplase for heart attack, with a real safety and convenience edge rather than a bigger efficacy win.

Years of guideline-endorsed off-label stroke use, then a 2025 approval

For stroke, tenecteplase's regulatory story ran in the opposite order from most drugs on this site: guideline-endorsed clinical use arrived years before FDA approval. American Heart Association/American Stroke Association guidance identified tenecteplase as a reasonable alternative to alteplase for eligible ischemic-stroke patients as early as 2019, on the strength of a growing trial base that included the Canadian AcT trial (Menon BK, Buck BH, Singh N, et al., "Intravenous Tenecteplase Compared with Alteplase for Acute Ischaemic Stroke in Canada (AcT): a Pragmatic, Multicentre, Open-Label, Registry-Linked, Randomised, Controlled, Non-Inferiority Trial," Lancet 2022;400(10347):161-169, PMID 35779553): 1,600 patients found tenecteplase non-inferior to alteplase on the primary functional-outcome measure (excellent outcome in 36.9% vs. 34.8%), with similar rates of symptomatic intracranial hemorrhage. Despite that trial base and years of accepted off-label use, the FDA did not formally approve tenecteplase for acute ischemic stroke until 3 March 2025, based specifically on AcT trial data — an approval widely reported as the first new FDA-cleared acute stroke medicine in almost 30 years.

Current status

Tenecteplase remains FDA-approved for both acute myocardial infarction and acute ischemic stroke, marketed by Genentech, and its dosing advantage is now reshaping stroke-care guidelines directly: the AHA/ASA's 2026 acute ischemic stroke guideline (published online 26 January 2026, replacing the 2018-2019 guideline) recommends tenecteplase and alteplase on equal footing for eligible patients within 4.5 hours of onset, rather than treating alteplase as the default choice with tenecteplase as a secondary option — a genuine, fast-moving shift in the standard of care less than a year after tenecteplase's own stroke approval. Like alteplase and reteplase, tenecteplase is a hospital-only emergency drug administered under direct clinical supervision, with no wellness, cosmetic, or self-administered use of any kind.