Lysine Analogues Tranexamic Acid Research Articles

Discovery and Evaluation of Anti-Fibrinolytic Plasmin Inhibitors Derived from 5-(4-Piperidyl)isoxazol-3-ol (4-PIOL).

Inhibition of plasmin has been found to effectively reduce fibrinolysis and to avoid hemorrhage. This can be achieved by addressing its kringle 1 domain with the known drug and lysine analogue tranexamic acid. Guided by shape similarities toward a previously discovered lead compound, 5-(4-piperidyl)isoxazol-3-ol, a set of 16 structurally similar compounds was assembled and investigated. Successfully, in vitro measurements revealed one compound, 5-(4-piperidyl)isothiazol-3-ol, superior in potency compared to the initial lead. Furthermore, a strikingly high correlation (R2 = 0.93) between anti-fibrinolytic activity and kringle 1 binding affinity provided strong support for the hypothesized inhibition mechanism, as well as revealing opportunities to fine-tune biological effects through minor structural modifications. Several different ligand-based (Freeform, shape, and electrostatic-based similarities) and structure-based methods (e.g., Posit, MM/GBSA, FEP+) were used to retrospectively predict the binding affinities. A combined method, molecular alignment using Posit and scoring with Tcombo, lead to the highest coefficient of determination (R2 = 0.6).

Antifibrinolytics (lysine analogues) for the prevention of bleeding in people with haematological disorders.

Background Patients with haematological disorders are frequently at risk of severe or life-threatening bleeding as a result of thrombocytopenia. This is despite the routine use of prophylactic platelet transfusions (PlTx) to prevent bleeding once the platelet count falls below a certain threshold. PlTx are not without risk and adverse events may be life-threatening. A possible adjunct to prophylactic PlTxs is the use of antifibrinolytics, specifically the lysine analogues tranexamic acid (TXA) and epsilon aminocaproic acid (EACA). Objectives To determine the efficacy and safety of antifibrinolytics (lysine analogues) in preventing bleeding in patients with haematological disorders. Search methods We searched for randomised controlled trials (RCTs) in the Cochrane Central Register of Controlled Trials (CENTRAL Issue 12, 2012), MEDLINE (1948 to 10 January 2013), EMBASE (1980 to 10 January 2013), CINAHL (1982 to 10 January 2013), PubMed (e-publications only) and the Transfusion Evidence Library (1980 to January 2013). We also searched several international and ongoing trial databases to 10 January 2013 and citation-tracked relevant reference lists. Selection criteria RCTs involving patients with haematological disorders, who would routinely require prophylactic platelet transfusions to prevent bleeding. We only included trials involving the use of the lysine analogues TXA and EACA. Data collection and analysis Two authors independently screened all electronically derived citations and abstracts of papers, identified by the review search strategy, for relevancy. Two authors independently assessed the full text of all potentially relevant trials for eligibility, completed the data extraction and assessed the studies for risk of bias using The Cochrane Collaboration's 'Risk of bias' tool. We requested missing data from one author but the data were no longer available. The outcomes are reported narratively: we performed no meta-analyses because of the heterogeneity of the available data. Main results Of 470 articles initially identified, 436 were excluded on the basis of the title and abstract. We reviewed 34 full-text articles from which four studies reported in five articles were eligible for inclusion. We did not identify any RCTs which compared TXA with EACA. We did not identify any ongoing RCTs. One cross-over TXA study (eight patients) was excluded from the outcome analysis because data from this study were at a high risk of bias. Data from the other three studies were all at unclear risk of bias due to lack of reporting of study methodology. Three studies (two TXA (12 to 56 patients), one EACA (18 patients)) reported in four articles (published 1983 to 1995) were included in the narrative review. All three studies compared the drug with placebo. All studies reported bleeding, but it was reported in different ways. All three studies suggested antifibrinolytics reduced the risk of bleeding. The first study showed a difference in average bleeding score of 42 in placebo (P) versus three (TXA). The second study only showed a difference in bleeding episodes during consolidation chemotherapy, with a mean of 2.6 episodes/patient (standard deviation (SD) 2.2) (P) versus a mean of 1.1 episodes/patient (SD 1.4) (TXA). The third study reported bleeding on 50% of days at risk (P) versus bleeding on 31% of days at risk (EACA). Two studies (68 patients) reported thromboembolism and no events occurred. All three studies reported a reduction in PlTx usage. The first study reported a difference of 222 platelet units (P) versus 69 platelet units (TXA). The second study only showed a difference in total platelet usage during consolidation chemotherapy, with a mean of 9.3 units (SD 3.3) (P) versus 3.7 (SD 4.1) (TXA). The third study reported one PlTx every 10.5 days at risk (P) versus one PlTx every 13.3 days at risk (EACA). Two studies reported red cell transfusion requirements and one study found a reduction in red cell transfusion usage. One study reported death due to bleeding as an outcome measure and none occurred. Only one study reported adverse events of TXA as an outcome measure and none occurred. None of the studies reported on the following pre-specified outcomes: overall mortality, adverse events of transfusion, disseminated intravascular coagulation (DIC) or quality of life (QoL). Authors' conclusions Our results indicate that the evidence available for the use of antifibrinolytics in haematology patients is very limited. The only available data suggest that TXA and EACA may be useful adjuncts to platelet transfusions so that platelet use, and the complications associated with their use, can be reduced. However, the trials were too small to assess whether antifibrinolytics increased the risk of thromboembolic events. Large, high-quality RCTs are required before antifibrinolytics can be demonstrated to be efficacious and safe in widespread clinical practice.

Regulatory decisions pertaining to aprotinin may be putting patients at risk.

The antifibrinolytic agent aprotinin, a naturally occurring serine protease inhibitor, was removed from the worldwide market in October 2007.[1][1] Aprotinin and two other antifibrinolytic agents (the lysine analogues tranexamic acid and aminocaproic acid) had been used in cardiac surgery to

Anti-Fibrinolytics (lysine analogues) for the Prevention of Bleeding in Patients with Hematological Disorders: A Systematic Review

AbstractAbstract 3427 Introduction:Patients with hematological disorders are frequently at risk of severe or life-threatening bleeding as a result of thrombocytopenia. This is despite the routine use of prophylactic platelet transfusions (PlTx) to prevent bleeding once the platelet count falls below a certain threshold. PlTx are not without risk and adverse events may be life threatening. A possible adjunct to prophylactic PlTxs is the use of anti-fibrinolytics, specifically the lysine analogues tranexamic acid (TXA) and epsilon aminocaproic acid (EACA). The objective of this review was to establish the current evidence for the safety and efficacy of these agents in thrombocytopenic patients with hematological disorders who would routinely receive PlTx. Methods:The protocol was pre-specified and published in the Cochrane Database of Systematic Reviews (CD009733). We searched (in full) MEDLINE (1948–2011); EMBASE (1980–2011); CENTRAL (The Cochrane Library Issue 4, 2011); CINAHL (1982–2011); LILACS; Transfusion Evidence Library: WHO ICTRP; ISRCTN ClinicalTrials.gov; EU Clinical Trials Register; and 4 other electronic databases up to 31st October 2011 as well as additional records from hand-searching articles. There were no restrictions on language or publication period. Eligible studies were randomized-controlled trials (RCTs) involving patients (of all ages) with a hematological disorder who were severely thrombocytopenic due to bone marrow failure, who required PlTxs, and who received TXA or EACA (any dose, via any route). Trials of patients with immune thrombocytopenia were excluded. Two authors extracted data independently. Study and participant characteristics, details of the intervention and comparator, and key outcomes were recorded. Primary outcomes were bleeding and thromboembolism. Secondary outcomes included mortality, laboratory measures of fibrinolysis, number of platelet (plt) and red blood cell (RBC) transfusions (Tx), and adverse events of anti-fibrinolytic agents or transfusions. Risk of study bias was assessed using the Cochrane Collaboration criteria. Results:Of 446 initially identified, 415 articles were excluded on the basis of the title and abstract. Thirty-one full text articles were reviewed from which, 4 studies reported in 5 articles were eligible for inclusion. One TXA study (8 patients (pts)) was excluded from the qualitative analysis due to poor study design. Three studies (2 TXA (12 to 56pts), 1 EACA (18pts)) reported in 4 articles (published 1983 to 1995) were included in the qualitative analysis. No quantitative analysis was performed due to differences in the way outcomes were reported and the paucity of data available.All studies reported bleeding, but it was reported in different ways. All 3 studies suggested anti-fibrinolytics reduced the risk of bleeding. The first study showed a difference in average bleeding score of 42 in placebo (P) vs. 3 (TXA). The second study only showed a difference in bleeding episodes during consolidation chemotherapy, mean 2.6 episodes/pt (SD 2.2) (P) vs. mean 1.1 episodes/pt (SD 1.4) (TXA). The final study reported bleeding on 50% of days at risk (P) vs. bleeding on 31% of days at risk (EACA). Two studies reported thromboembolism and no events occurred. All 3 studies reported a reduction in PlTx usage. The first study reported a difference of 222 plt units (P) vs. 69 plt units (TXA). The second study only showed a difference in total plt usage during consolidation chemotherapy, mean 9.3 units (SD 3.3) (P) vs 3.7 (SD 4.1) (TXA). The final study reported 1 PlTx every 10.5 days at risk (P) vs. 1 PlTx every 13.3 days at risk (EACA). One of the 2 studies that reported RBCTx usage found a reduction in use. None of the studies reported overall mortality. One study reported death due to bleeding, and none occurred. Only 1 study reported adverse events of TXA and none occurred. Conclusions:Our results indicate that the evidence base for the use of anti-fibrinolytics in this patient group is poor. TXA and EACA may be useful adjuncts to PlTx in order to minimize their use and any associated complications because all of the studies showed the same direction of effect. They appear to be well tolerated although the data are sparse. Larger RCTs are required to evaluate the use of anti-fibrinolytics before they can be widely adopted in clinical hematology practice. Disclosures:No relevant conflicts of interest to declare.

Effects of Aprotinin or Tranexamic Acid on Proteolytic/Cytokine Profiles in Infants After Cardiac Surgery

After cardiopulmonary bypass (CPB), elaboration of cytokines, and subsequent induction of interstitial proteases, such as matrix metalloproteinases (MMPs), can result in a complex postoperative course. The serine protease inhibitor, aprotinin, which has been used in congenital heart surgery putatively for modulating fibrinolysis is now unavailable, necessitating the use of lysine analogues such as tranexamic acid (TXA). The present study tested the hypothesis that distinctly different plasma profiles of signaling molecules and proteases would be differentially affected after the administration of aprotinin or TXA in the context of congenital cardiac surgery and CPB. Thirty-seven patients (age, 4.8 +/- 0.3 months) undergoing corrective surgery for ventricular septal defect and tetralogy of Fallot received either aprotinin (n = 22) or TXA (n = 15). Using a high throughput multiplex suspension immunoassay, plasma was serially quantified for cytokines and MMPs: before aprotinin or TXA (baseline), after separation from CPB, and 4, 12, 24, and 48 hours post-CPB. Tumor necrosis factor-alpha increased initially after CPB in both the aprotinin and TXA groups, but at 24 and 48 hours post-CPB was approximately 50% lower in the aprotinin group (p < 0.05). The IL-10 levels were threefold higher in the TXA group compared with the aprotinin group immediately post-CBP (p < 0.05). Plasma levels of MMP types associated with inflammation, MMP-8, and MMP-9, were twofold higher in the late post-CPB period in the TXA group when compared with the aprotinin group. After ventricular septal defect or tetralogy of Fallot repair in children, cytokine induction occurs, which is temporally related to the emergence of a specific MMP profile. Moreover, these unique findings demonstrated differential effects between the serine protease inhibitor aprotinin and the lysine analogue TXA with respect to cytokine and MMP induction in the early postoperative period. The different cytokine-proteolytic profile between these antifibrinolytics may in turn influence biologic processes in the postoperative period.

Engineering Kunitz Domain of Human Tissue Factor Pathway Inhibitor-2 to Selectively Inhibit Fibrinolysis: An Antifibrinolytic Agent with Potential to Replace Aprotinin

Tissue factor pathway inhibitor-2 (TFPI-2) inhibits factor XIa, plasma kallikrein and factor VIIa/tissue factor; accordingly, it has been proposed for use as an anticoagulant. Full-length TFPI-2 or its isolated first Kunitz domain (KD1) also inhibits plasmin and therefore it has been proposed for use as an antifibrinolytic agent. However, the anticoagulant properties of TFPI-2 or KD1 would diminish its antifibrinolytic function. In this report, structure based investigations and analysis of the serine proteases profiles revealed that coagulation enzymes prefer a hydrophobic residue at the P2′ (nomenclature of Schechter and Berger, BBRC , 27:157–162, 1967) position in their substrates/inhibitors, whereas plasmin prefers a positively charged arginine residue at the corresponding position in its substrates/inhibitors. Based upon this observation, we changed the P2′ residue Leu17 (bovine pancreatic trypsin inhibitor/aprotinin numbering) in KD1 to Arg (KD1-L17R) and compared its inhibitory properties with the wild-type KD1 (KD1-WT). Both WT and KD1-L17R were expressed in E. Coli, folded and purified to homogeneity. Amino-terminal sequences and mass spectra revealed proper folding of the KD1-WT and KD1-L17R. As compared to KD1-WT, the KD1-L17R neither prolonged the activated partial thromboplastin time of normal plasma nor it inhibited factor XIa, plasma kallikrein or factor VIIa/tissue factor. Further, KD1-L17R inhibited plasmin with ~4-fold increased affinity. In a mouse liver laceration model of bleeding from small vessels, KD1-L17R reduced total blood loss by 84% compared with KD1-WT, which reduced total blood loss by 10%. Moreover, in this bleeding model, KD1-L17R was more effective than aprotinin (70% reduction), which has been used as an antifibrinolytic agent to decrease blood loss during major surgery. In this model, KD1-L17R was also more effective than the lysine analogue tranexamic acid (52% reduction). In additional studies, in a tail transection model of bleeding from a large vessel, KD1-L17R reduced total blood loss by 70% and was more effective than KD1-WT (46% reduction), aprotinin (43% reduction) and tranexamic acid (67% reduction). Notably, as compared to aprotinin, renal toxicity manifesting as multifocal tubular necrosis by histopathology was not observed with KD1-L17R or KD1-WT. In conclusion, KD1-L17R is a specific inhibitor of plasmin without anticoagulant properties and is more effective in reducing blood loss compared with known antifibrinolytic agents in clinical use.

Desmoteplase-mediated plasminogen activation and clot lysis are inhibited by the lysine analogue tranexamic acid

Tranexamic acid (trans-4-aminoethylcyclohexane-1carboxylic acid; t-AMCA) (TA) is a synthetic lysine analogue with potent antifibrinolytic properties. TA saturates lysine binding sites on kringle domains of plasminogen and prevents them from interacting with the fibrin surface, thereby disrupting plasminogen activation and fibrinolysis [1,2]. TA is used clinically to minimize blood loss in a range of haemorrhagic conditions, mainly during cardiac surgeries or in the treatment of chronic bleeding disorders (e.g. menorrhagia) [2]. TA is also considered in bleeding associated with thrombolytic therapy [3]. Control of systemic fibrinolysis in humans requires a therapeutic plasma TA concentration of 10–15mg/ml (63–95mmol/l) [4,5].

Are antifibrinolytic drugs equivalent in reducing blood loss and transfusion in cardiac surgery? A meta-analysis of randomized head-to-head trials

BackgroundAprotinin has been shown to be effective in reducing peri-operative blood loss and the need for re-operation due to continued bleeding in cardiac surgery. The lysine analogues tranexamic acid (TXA) and epsilon aminocaproic acid (EACA) are cheaper, but it is not known if they are as effective as aprotinin.MethodsStudies were identified by searching electronic databases and bibliographies of published articles. Data from head-to-head trials were pooled using a conventional (Cochrane) meta-analytic approach and a Bayesian approach which estimated the posterior probability of TXA and EACA being equivalent to aprotinin; we used as a non-inferiority boundary a 20% increase in the rates of transfusion or re-operation because of bleeding.ResultsPeri-operative blood loss was significantly greater with TXA and EACA than with aprotinin: weighted mean differences were 106 mls (95% CI 37 to 227 mls) and 185 mls (95% CI 134 to 235 mls) respectively. The pooled relative risks (RR) of receiving an allogeneic red blood cell (RBC) transfusion with TXA and EACA, compared with aprotinin, were 1.08 (95% CI 0.88 to 1.32) and 1.14 (95% CI 0.84 to 1.55) respectively. The equivalent Bayesian posterior mean relative risks were 1.15 (95% Bayesian Credible Interval [BCI] 0.90 to 1.68) and 1.21 (95% BCI 0.79 to 1.82) respectively. For transfusion, using a 20% non-inferiority boundary, the posterior probabilities of TXA and EACA being non-inferior to aprotinin were 0.82 and 0.76 respectively. For re-operation the Cochrane RR for TXA vs. aprotinin was 0.98 (95% CI 0.51 to 1.88), compared with a posterior mean Bayesian RR of 0.63 (95% BCI 0.16 to 1.46). The posterior probability of TXA being non-inferior to aprotinin was 0.92, but this was sensitive to the inclusion of one small trial.ConclusionThe available data are conflicting regarding the equivalence of lysine analogues and aprotinin in reducing peri-operative bleeding, transfusion and the need for re-operation. Decisions are sensitive to the choice of clinical outcome and non-inferiority boundary. The data are an uncertain basis for replacing aprotinin with the cheaper lysine analogues in clinical practice. Progress has been hampered by small trials and failure to study clinically relevant outcomes.

The Receptor for Urokinase-Type Plasminogen Activator of a Human Keratinocyte Line (HaCaT)

It is assumed that plasmin participates in pericellular proteolysis in the epidermis. Plasmin is generated by keratinocyte-associated plasminogen activators from the proenzyme plasminogen; plasminogen activation can proceed at the keratinocyte surface. The resultant plasmin interferes with cell to matrix adhesion and does possibly contribute to keratinocyte migration during reepithelialization. Here we describe the receptor for urokinase-type plasminogen activator (uPA-R) in the human keratinocyte cell line HaCaT, which serves to direct plasminogen activation to the cell surface; we relate the receptor to the uPA-R previously described in human myclo-/monocytes. Binding of uPA to the receptor accelerated plasminogen activation by a factor of ≈10, compared to uPA in solution. Receptor-bound uPA was susceptible to inhibition by the plasminogen activator inhibitors 1 and 2. uPA and uPA-R antigen, as well as uPA activity, were localized to the leading front of expanding sheets of HaCaT cells. Exposure of HaCaT cells to plasminogen was followed by detachment of the cells. Detachment was prevented by an anti-catalytic anti-uPA antibody, by the plasmin-specific inhibitor aprotinin, and by the lysine analogue tranexamic acid, the latter of which prevents plasmin(ogen) binding to the cell surface. Our findings support the hypothesis that uPA-mediated plasminogen activation is characteristic of mobile rather than sessile keratinocytes. Moreover, the uPA-R seems to focalize plasminogen activation to the surface of cells at the site of keratinocyte migration.