Lepirudin
recombinant hirudin, [Leu1,Thr2]-63-desulfohirudin, HBW 023, r-hirudin
Lepirudin was a recombinant hirudin, a 65-residue direct thrombin inhibitor produced in yeast, licensed specifically for anticoagulating patients with heparin-induced thrombocytopenia. It filled a genuine clinical gap for over a decade but was withdrawn worldwide in 2012 for commercial reasons. Its withdrawal is also remembered for a real safety problem: fatal anaphylaxis on re-exposure.
Mechanism
Lepirudin is recombinant hirudin expressed in Saccharomyces cerevisiae, differing from natural leech hirudin variant 1 at the first two residues (leucine and threonine replace the two valines) and lacking the sulfate on tyrosine 63. Functionally it behaves as hirudin does: a bivalent, essentially irreversible direct thrombin inhibitor forming a tight one-to-one non-covalent complex with thrombin. The globular, triply disulfide-bonded N-terminal domain plugs the catalytic cleft; the acidic C-terminal tail engages exosite 1 and blocks fibrinogen recognition.
The clinical rationale was specific. Heparin-induced thrombocytopenia is an antibody-mediated reaction to complexes of heparin with platelet factor 4; it paradoxically causes thrombosis rather than bleeding, and all heparins must be stopped immediately. Lepirudin neither binds platelet factor 4 nor requires antithrombin, so it can anticoagulate a sensitised patient without feeding the immune reaction. Clearance is almost entirely renal, with a half-life of little over an hour in normal kidney function that can extend to days in renal failure. That renal dependence, combined with the absence of any reversal agent, made lepirudin technically demanding to use. Anticoagulant effect was titrated against the activated partial thromboplastin time ratio.
What the research shows
The HAT programme comprised prospective multicentre studies in patients with confirmed heparin-induced thrombocytopenia, compared with a historical control cohort of similar patients managed without a direct thrombin inhibitor. In the principal published analysis of 95 lepirudin-treated patients, a complete laboratory response (normalisation of the platelet count) occurred in 65 patients (69.1%). The combined endpoint of death, new thromboembolic complication or limb amputation at 35 days occurred in 30.9% of lepirudin patients versus 52.1% of the 120 historical controls. Bleeding was more common with lepirudin (44.6% versus 27.2%).
A subsequent meta-analysis pooling two prospective trials (113 lepirudin-treated patients against 91 historical controls) reported the combined endpoint in 22.1% of treated patients, significantly lower than historical controls (p=0.004), and identified an activated partial thromboplastin time ratio of 1.5 to 2.5 as the range associated with optimal efficacy without excess bleeding, ratios below 1.5 being subtherapeutic and above 2.5 carrying elevated bleeding risk. That aPTT target became the basis of the labelled monitoring recommendation.
The most consequential post-marketing finding was immunological. Antihirudin IgG antibodies developed in a substantial proportion of treated patients with prolonged exposure. These antibodies did not usually neutralise the drug; instead they formed complexes that delayed renal clearance and paradoxically enhanced and prolonged anticoagulation, requiring dose reduction. More seriously, a pharmacovigilance analysis of approximately 35,000 treated patients identified nine severe anaphylactic reactions closely associated in time with lepirudin administration, four of them fatal, giving an estimated incidence of about 0.015% (5 of 32,500) on first exposure and 0.16% (4 of 2,500) on re-exposure. This became a defining caution for the class.
Evidence assessment
Mixed evidence
Downgraded from 'strong' in the draft on audit. Lepirudin genuinely held FDA and EU marketing authorisations for heparin-induced thrombocytopenia with thromboembolic complications, and all three cited papers were verified as real (PMIDs 10441094, 10910895 and 14568897). But the elsewhere in this set 'strong' denotes replicated randomised evidence plus regulator-approved labelling, and lepirudin fails the first half of that test: every efficacy study was a prospective single-arm cohort compared against historical controls, never a randomised trial, because randomising patients with active heparin-induced thrombocytopenia to continued heparin would have been unethical. Historical-control comparisons are vulnerable to secular changes in diagnosis and supportive care, and the effect sizes cannot be treated as randomised estimates. Consistent internal findings across two cohorts plus regulatory approval, with no randomised data and a real post-marketing anaphylaxis signal, is best described as mixed.
Tiers are applied consistently across the library and re-checked when new trials read out. Read the grading method.
Key studies
Lepirudin (recombinant hirudin) for parenteral anticoagulation in patients with heparin-induced thrombocytopenia Preclinical only
A complete laboratory response (platelet recovery) occurred in 65 of 95 lepirudin-treated patients (69.1%). The combined endpoint of death, new thromboembolic complication or limb amputation at 35 days occurred in 30.9% of treated patients versus 52.1% of historical controls, but bleeding was more frequent (44.6% versus 27.2%).
Anaphylactic and anaphylactoid reactions associated with lepirudin in patients with heparin-induced thrombocytopenia Preclinical only
Nine severe anaphylactic reactions were identified in close temporal association with lepirudin, four of them fatal. Estimated incidence was approximately 0.015% (5 of 32,500) on first exposure and 0.16% (4 of 2,500) among re-exposed patients, with an estimated re-exposure rate of 7.5%.
Safety
Bleeding is the dominant complication and there is no antidote; the drug is not readily removed by conventional low-flux haemodialysis, though high-flux membranes clear some. Because clearance is almost entirely renal, any degree of kidney impairment causes marked accumulation, and lepirudin was effectively unusable in severe renal failure.
The distinctive hazard is immunological. Antihirudin antibodies form in a substantial proportion of patients and, rather than neutralising the drug, tend to prolong its effect by impairing renal clearance, so aPTT monitoring and dose reduction were required during prolonged treatment. Anaphylaxis, including four fatal cases in the published pharmacovigilance series, occurred predominantly in patients re-exposed within months of a previous course, at an estimated 0.16% on re-exposure against 0.015% on first exposure; this is the reason re-exposure was strongly discouraged. Other reported effects include injection- and infusion-site reactions, fever, abnormal liver function tests and anaemia. Since lepirudin is no longer manufactured, material sold under this name is outside any regulated supply chain and its identity and sterility cannot be assumed. Argatroban, a small-molecule direct thrombin inhibitor with hepatic clearance, has largely taken over the clinical niche.
Regulatory status
| Jurisdiction | Status |
|---|---|
| United Kingdom | Not available. Lepirudin held a centralised EU marketing authorisation from 1997 for anticoagulation in adults with type II heparin-induced thrombocytopenia and thromboembolic disease requiring parenteral antithrombotic therapy. The marketing authorisation holder voluntarily withdrew it and the European Commission issued the withdrawal decision in April 2012, for commercial reasons. There is no MHRA-licensed lepirudin product. Argatroban is the direct thrombin inhibitor now used in this indication in the UK. |
| United States | Formerly FDA-approved (March 1998) for anticoagulation in patients with heparin-induced thrombocytopenia and associated thromboembolic disease. Production was discontinued in 2012 and it is no longer marketed in the United States. |
| WADA (sport) | Not listed on the WADA Prohibited List. Anticoagulants are not prohibited in or out of competition. |
Questions
Heparin-induced thrombocytopenia is an antibody reaction to heparin-platelet factor 4 complexes that, counterintuitively, causes thrombosis rather than bleeding. Once diagnosed, every form of heparin must stop immediately, yet the patient still urgently needs anticoagulation, often more than before. Lepirudin filled that gap because it inhibits thrombin directly, without antithrombin and without any interaction with platelet factor 4, so it cannot feed the immune reaction.
The manufacturer voluntarily withdrew it for commercial reasons in 2012. Its market had been eroded by argatroban, which is cleared hepatically rather than renally, a decisive practical advantage, since many patients with heparin-induced thrombocytopenia are critically ill with impaired kidney function, in whom lepirudin accumulates dangerously. The anaphylaxis signal on re-exposure also weighed against it.
Lepirudin is a foreign yeast-expressed protein and provokes antihirudin antibodies in a substantial proportion of patients. A pharmacovigilance analysis covering roughly 35,000 treated patients found nine severe anaphylactic reactions, four fatal, at an estimated 0.015% on first exposure and 0.16% on re-exposure, typically in patients re-treated within a few months of a previous course. This is the main reason re-exposure was strongly discouraged and a significant part of why the class fell out of favour.
Argatroban is the parenteral direct thrombin inhibitor most commonly used in the UK, with bivalirudin as an alternative particularly around cardiac procedures. Direct oral anticoagulants are increasingly used once the acute phase has passed. Any decision of this kind belongs with the treating haematology and critical care teams. This entry is educational and does not describe how any of these agents should be used.