Fondaparinux sodium: a review of its use in the management of acute coronary syndromes

Comparative evaluation of efficacy, safety and haemostatic parameters of enoxaparin and fondaparinux in unstable coronary artery disease

AIM

To compare the safety and efficacy of Enoxaparin (EX) and Fondaparinux (FD) in patients with Unstable Coronary Artery Disease (UCAD).

MATERIALS AND METHODS

A prospective, open label, randomized comparative study was designed to study the comparative efficacy and safety of EX and FD in UCAD patients. Recovery, recurrence, major and minor bleeding and biochemical investigations were evaluated and compared among two arms.

RESULTS

The baseline demographic characteristics were similar in both groups, with mean age of 56.05 and 56.05 years in EX and FD group respectively. Recovery was equal in two arms. Recurrent MI or angina was seen numerically more in EX group, but it did not statistically vary from that in the FD group. Incidence of haemorrhage was similar in both groups at 9 days, but at 30 days, EX showed a higher incidence (p<0.05). Deaths were prevented in both the treatment arms. Bleeding parameters such as BT, CT and platelet count were not altered in both groups.

CONCLUSION

FD appeared to be better than EX in efficacy, as was indicated by a numerically more decrease in recurrence of angina or MI. FD regimen group also had better safety profile, as there was no incidence of haemorrhage at 30 days Therefore, we conclude that FD is an attractive option than EX in UCAD patients.

In silico discovery of a compound with nanomolar affinity to antithrombin causing partial activation and increased heparin affinity

The medical and socioeconomic relevance of thromboembolic disorders promotes an ongoing effort to develop new anticoagulants. Heparin is widely used as activator of antithrombin but incurs side effects. We screened a large database in silico to find alternative molecules and predicted d-myo-inositol 3,4,5,6-tetrakisphosphate (TMI) to strongly interact with antithrombin. Isothermal titration calorimetry confirmed a TMI affinity of 45 nM, higher than the heparin affinity (273 nM). Functional studies, fluorescence analysis, and citrullination experiments revealed that TMI induced a partial activation of antithrombin that facilitated the interaction with heparin and low affinity heparins. TMI improved antithrombin inhibitory function of plasma from homozygous patients with antithrombin deficiency with a heparin binding defect and also in a model with endothelial cells. Our in silico screen identified a new, non-polysaccharide scaffold able to interact with the heparin binding domain of antithrombin. The functional consequences of this interaction were experimentally characterized and suggest potential anticoagulant therapeutic applications.

Factor Xa inhibitors for acute coronary syndromes

BACKGROUND

The activation of coagulation mechanisms plays a central role in the pathogenesis of acute coronary syndromes (ACS). Administration of unfractionated heparin (UFH) and low molecular weight heparins (LMWH), agents preventing the progression of thrombus formation, is a crucial therapeutic strategy. However, some limitations related to their use have recently stimulated the development of new synthetic agents.

OBJECTIVES

To evaluate the clinical efficacy and safety of factor Xa inhibitors for treatment of ACS compared to UFH or LMWH.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) of the Cochrane Library (Issue 1, 2008), PubMed, EMBASE and LILACS as well as the publications from International Congresses and the reference lists of the selected studies in December 2008.

SELECTION CRITERIA

We used randomized controlled trials (RCTs) comparing factor Xa inhibitors to UFH or LMWH during the course of ACS. Outcome measures included all-cause mortality, myocardial infarction, re-infarction, ischemia recurrence, and adverse events.

DATA COLLECTION AND ANALYSIS

The selection, quality assessment and data extraction of the included trials were done independently by two authors and disagreements were resolved by consensus. Data were analysed by the use of risk ratio (RR) with 95% confidence interval (CI), and the numbers needed to treat (NNT) were reported as needed.

MAIN RESULTS

A total of four RCTs involving 27,976 subjects were included. Fondaparinux was the only factor Xa inhibitor identified in our included RCTs. Fondaparinux appeared to be related to a lower risk in all-cause mortality at 90 to 180 days (RR 0.89; 95% CI 0.81 to 0.97), especially in the group where enoxaparin (a LMWH) was the control drug. Fondaparinux was also associated with a lower risk in major and minor bleeding at 30 days compared to enoxaparin (RR 0.63, 95% CI 0.55 to 0.73; RR 0.34, 95% CI 0.28 to 0.43, respectively), but not when compared to UFHs (RR 1.41; 95% CI 0.49 to 4.10; RR 0.70, 95% CI 0.14 to 3.39 respectively).

AUTHORS' CONCLUSIONS

The therapeutic efficacy of factor Xa inhibitors in ACS seemed to be related to a reduced risk in all-cause mortality at 90 to 180 days, with a better safety profile than enoxaparin in terms of reduce incidence of major and minor bleeding.

Cardiovascular drug therapy in the elderly: benefits and challenges

Increasing life expectancy in industrialized societies has resulted in a huge population of older adults with cardiovascular disease. Despite advances in device therapy and surgery, the mainstay of treatment for these disorders remains pharmacological. Hypertension affects two-thirds of older adults and remains a potent risk factor for coronary artery disease, chronic heart failure, atrial fibrillation, and stroke in this age group. Numerous trials have demonstrated reduction in these adverse outcomes with antihypertensive drugs. After acute myocardial infarction, β-adrenergic blockers reduce mortality regardless of patient age. Statins and antiplatelet drugs have proven beneficial in both primary and, especially, secondary prevention of coronary events in older adults. In elders with chronic heart failure, loop diuretics must be used cautiously, owing to their higher potential for adverse effects, whereas angiotensin-converting-enzyme inhibitors and β-blockers reduce symptoms and prolong survival. The high risk of stroke in elderly patients with atrial fibrillation is markedly reduced with warfarin, although bleeding risk is increased. The high prevalence of polypharmacy among older adults with cardiovascular disease, coupled with age-associated physiological changes and comorbidities, provides major challenges in adherence and avoidance of drug-related adverse events.

Fondaparinux: a pharmacoeconomic review of its use in the management of non-ST-segment elevation acute coronary syndrome

Fondaparinux (Arixtra) is an anticoagulant that selectively inhibits activated factor X, thereby interrupting the blood coagulation cascade. In OASIS-5, a large pivotal trial in patients with non-ST-segment elevation acute coronary syndrome (NSTE-ACS), subcutaneous fondaparinux 2.5 mg once daily was noninferior to subcutaneous enoxaparin 1 mg/kg twice daily (both agents were administered over a mean of about 5 days in combination with antiplatelet therapy) in reducing death or ischaemic events at 9 days, and the efficacy was maintained for up to 6 months (study end). However, fondaparinux was associated with a significantly lower rate of bleeding than enoxaparin in the first 9 days, and at 3 and 6 months. This lower rate of bleeding led to lower long-term mortality and morbidity with fondaparinux than with enoxaparin. In modelled cost-utility analyses conducted from a healthcare payer perspective in Spain, France and the US with a lifetime horizon, fondaparinux once daily was predicted to be cost effective relative to enoxaparin twice daily with regard to the incremental cost per QALY gained. In Spain and the US, fondaparinux dominated enoxaparin (i.e. was less costly and more effective) and, in the French analysis, the incremental cost per QALY gained with fondaparinux versus enoxaparin was well within recommended thresholds. Results of short-term (6-month) cost analyses in the US and France also favoured fondaparinux over enoxaparin. Sensitivity analyses demonstrated that base-case conclusions were robust over a range of parameter estimates and assumptions, including plausible variations in baseline risk of a cardiac event or baseline risk of bleeding. In conclusion, in patients with NSTE-ACS receiving antiplatelet therapy, fondaparinux was cost effective relative to enoxaparin in cost-utility analyses in Europe and the US. This cost advantage primarily reflects the lower rate of bleeding with fondaparinux than with enoxaparin and the lower rate of mortality and morbidity over the long term.

Interaction of antithrombin with sulfated, low molecular weight lignins: opportunities for potent, selective modulation of antithrombin function

Antithrombin, a major regulator of coagulation and angiogenesis, is known to interact with several natural sulfated polysaccharides. Previously, we prepared sulfated low molecular weight variants of natural lignins, called sulfated dehydrogenation polymers (DHPs) (Henry, B. L., Monien, B. H., Bock, P. E., and Desai, U. R. (2007) J. Biol. Chem. 282, 31891-31899), which have now been found to exhibit interesting antithrombin binding properties. Sulfated DHPs represent a library of diverse noncarbohydrate aromatic scaffolds that possess structures completely different from heparin and heparan sulfate. Fluorescence binding studies indicate that sulfated DHPs bind to antithrombin with micromolar affinity under physiological conditions. Salt dependence of binding affinity indicates that the antithrombin-sulfated DHP interaction involves a massive 80-87% non-ionic component to the free energy of binding. Competitive binding studies with heparin pentasaccharide, epicatechin sulfate, and full-length heparin indicate that sulfated DHPs bind to both the pentasaccharide-binding site and extended heparin-binding site of antithrombin. Affinity capillary electrophoresis resolves a limited number of peaks of antithrombin co-complexes suggesting preferential binding of selected DHP structures to the serpin. Computational genetic algorithm-based virtual screening study shows that only one sulfated DHP structure, out of the 11 present in a library of plausible sequences, bound in the heparin-binding site with a high calculated score supporting selectivity of recognition. Enzyme inhibition studies indicate that only one of the three sulfated DHPs studied is a potent inhibitor of free factor VIIa in the presence of antithrombin. Overall, the chemo-enzymatic origin and antithrombin binding properties of sulfated DHPs present novel opportunities for potent and selective modulation of the serpin function, especially for inhibiting the initiation phase of hemostasis.

Spotlight on fondaparinux sodium in acute coronary syndromes

Fondaparinux sodium (Arixtra) is a synthetic, sulfated pentasaccharide, selective factor Xa inhibitor that is indicated in Europe for preventing thrombus formation in patients with acute coronary syndromes (ACS; the focus of this review), including those with ST-segment elevation myocardial infarction (STEMI), non-STEMI (NSTEMI), or unstable angina. The large (n = 20,078), well designed OASIS-5 trial showed that subcutaneous fondaparinux 2.5 mg/day for < or =8 days was noninferior to subcutaneous enoxaparin 1 mg/kg twice daily (once daily in those with renal dysfunction) in reducing death or ischemic events at 9 days and the efficacy was maintained for up to 6 months (study end) in patients with unstable angina or NSTEMI. During this time, major bleeding occurred in fewer fondaparinux than enoxaparin recipients, resulting in a benefit : risk balance favoring fondaparinux. The incidence of death or reinfarction at 30 days was significantly lower in recipients of subcutaneous fondaparinux 2.5 mg/day than in those who received usual care (including unfractionated heparin treatment as indicated) in patients with STEMI in the large (n > 12,000) OASIS-6 trial. There were no differences in the incidence of major bleeding between these groups, resulting in a benefit : risk balance favoring fondaparinux. The specificity and selectivity of fondaparinux, combined with its long half-life and 100% bioavailability, allows once-daily anticoagulation without the need for monitoring activated clotting time. Subcutaneous fondaparinux was noninferior to enoxaparin treatment in patients with unstable angina or NSTEMI, and was more effective than usual care in those with STEMI. Fondaparinux has a favorable tolerability profile, particularly with regard to the risk of major bleeding, and limited data suggest that it is more cost effective than enoxaparin in the short term. Thus, overall, clinical evidence suggests that fondaparinux has a valuable place in the treatment of patients with ACS.