Alteplase (Activase, Cathflo Activase)

Alteplase is a real, FDA-approved recombinant tissue plasminogen activator (tPA) — the original clot-dissolving biologic behind an entire drug class, approved for heart attack in 1987 and for acute ischemic stroke in 1996, and still the reference drug that its own engineered descendants, reteplase and tenecteplase, are measured against.

A recombinant clot-dissolving enzyme, first of its kind

Alteplase is a recombinant form of human tissue plasminogen activator (tPA), an enzyme that converts plasminogen into plasmin, the protease that breaks down the fibrin mesh holding a blood clot together. Genentech manufactured it using recombinant DNA technology in genetically engineered mammalian cell culture — one of biotechnology's earliest commercial successes, arriving a few years after the company's original recombinant-insulin and recombinant-growth-hormone products. Unlike streptokinase, the older thrombolytic purified from bacteria, alteplase is a copy of the native human enzyme itself, avoiding the allergic reactions and antibody formation that repeated streptokinase exposure can cause — the reason tPA-class drugs, including the reteplase and tenecteplase covered elsewhere on this site, gradually displaced streptokinase in US practice.

Four approvals across three decades, on two pivotal trials

The FDA first approved alteplase (as Activase) on 13 November 1987 to reduce mortality in acute myocardial infarction. The trial that cemented its place over the older, far cheaper streptokinase was GUSTO-I (The GUSTO Investigators, "An International Randomized Trial Comparing Four Thrombolytic Strategies for Acute Myocardial Infarction," N Engl J Med 1993;329(10):673-682, PMID 8204123): 41,021 patients across four thrombolytic regimens found that an accelerated alteplase infusion plus IV heparin cut 30-day mortality to 6.3%, versus 7.2-7.4% on the streptokinase regimens — a real, statistically significant survival advantage that a later formal cost-effectiveness analysis of the same trial data priced at roughly $32,678 per additional year of life, judged reasonable against typical willingness-to-pay benchmarks of the era. The FDA extended alteplase's approval to acute massive pulmonary embolism in 1990, then to acute ischemic stroke within 3 hours of symptom onset on 18 June 1996, based on the NINDS rt-PA Stroke Trial (National Institute of Neurological Disorders and Stroke rt-PA Stroke Study Group, "Tissue Plasminogen Activator for Acute Ischemic Stroke," N Engl J Med 1995;333(24):1581-1587, PMID 7477192): patients treated with alteplase were at least 30% more likely than those on placebo to have minimal or no disability at 3 months, against a real increase in symptomatic intracranial hemorrhage within 36 hours (6.4% vs 0.6%) and no statistically significant difference in 90-day mortality (17% vs 21%). A fourth approval, Cathflo Activase — a small, fixed 2 mg dose instilled directly into a blocked central-venous catheter rather than given systemically — followed in 2001, later supported in children by a dedicated 310-patient prospective study finding an 82.9% success rate after up to two doses.

A label the guidelines have outrun

Alteplase's FDA stroke label has remained fixed at a 3-hour treatment window since 1996, even though the ECASS III trial (Hacke W, Kaste M, Bluhmki E, et al., "Thrombolysis with Alteplase 3 to 4.5 Hours after Acute Ischemic Stroke," N Engl J Med 2008;359(13):1317-1329) found a real, statistically significant benefit to treating out to 4.5 hours — a favorable 90-day outcome (modified Rankin Scale 0-1) in 52.4% of alteplase patients versus 45.2% on placebo in that extended window. The FDA has never approved a labeling change to match, and American Heart Association/American Stroke Association guidance has for more than a decade recommended treating eligible patients through 4.5 hours regardless — meaning a substantial share of alteplase's actual stroke use in the US runs on guideline consensus and accepted off-label practice rather than an FDA-cleared indication, a labeling gap now well over 15 years old.

Current status: still foundational, now facing a faster rival

Alteplase, marketed by Genentech (a Roche subsidiary), remains FDA-approved and in routine use for heart attack, pulmonary embolism, catheter clearance, and ischemic stroke. Despite its original composition-of-matter patents having expired decades ago, no generic or biosimilar alteplase has ever reached the US market — recombinant biologics have proven far harder to genericize than small-molecule drugs, and instead of a direct generic, alteplase's real competition has come from engineered variants of the same molecule: reteplase (1996) and tenecteplase, both covered separately on this site. That competition has intensified since tenecteplase's own March 2025 FDA approval for acute ischemic stroke, and the AHA/ASA's 2026 acute ischemic stroke guideline (published online 26 January 2026, replacing the 2018-2019 guideline) now recommends tenecteplase and alteplase on equal footing for eligible patients within 4.5 hours, rather than treating alteplase as the default with tenecteplase as a secondary option. Alteplase carries no wellness, cosmetic, or self-administered use of any kind — it is a hospital-only emergency drug given under direct clinical supervision.