Role of epsilon amino caproic acid in the management of haemophilic patients with inhibitors

Overcoming the challenges of treating hemophilia in resource-limited nations: a focus on medication access and adherence

BACKGROUND

Hemophilia is a high cost low volume disease. Resource limited nations (RLN) usually spend very little on health budget and most of it is spent in dealing with common ailments. Clotting products constitute more than 90% of the total cost of hemophilia care. The manner in which these products can be made accessible for persons with hemophilia (PWH) and how its continuous supply and distribution can be maintained and improved is described in this review.

AREAS COVERED

Number of PWH in the Resource Limited Nations (RLN); minimum amount of concentrate required to keep a PWH relatively free of bleeds; the different products available for management of PWH; means and ways to minimize and optimize the concentrate usage and purchase on a budget; nonfactor therapy; ways and means to improve the management and allow better quality concentrates in higher quantities for PWH in those countries; adherence as a challenge for RLN country and ways to manage them. The time covered is from 1980s till date. Pubmed was searched mainly for review articles with the key words hemophilia, RLN, concentrate access, alternative therapy. Cross references from these reviews as well as some of the abstracts from international conferences were read.

EXPERT OPINION

Developing a patient's society and a bleeding disorder registry are the two most important actions toward ensuring adequate treatment material for PWH in RLN. Government should allocate a budget for hemophilia care depending on the number of PWH diagnosed and future projection of increased numbers of PWH. Population based product requirement may not work initially as only 10-20% of PWH in such a country has been diagnosed hence initial requirement of concentrates should be directed to these patients. Meanwhile efforts should be made to diagnose new cases. Antenatal diagnosis centers should offer antenatal diagnosis and prevent birth of severe hemophilia children. Self sufficiency in plasma based concentrates should be planned and aimed. A national tendering committee can get a good price on the concentrates on global tendering with annual rate contracts (prevents outdating). Avoiding wastage by outdating of the products in large denomination vials will help. Hoarding concentrates in unreasonable amounts should be avoided through good supply chain management. Regular physiotherapy, proper use of optimum amounts of concentrate will reduce per PWH consumption of the factor concentrates. Plasma derived intermediate purity factors, first/second generation recombinant clotting factors are safe and relatively cheaper as well as effective. Also concentrates which are close to their expiry date (>3 < 6 months) are equally effective and cheap. With proper supply chain management such products can be included in the portfolio. Primary prophylaxis with low/ intermediate dose of the concentrates is a cost-effective way to manage the patients and this also reduces inhibitor development. Adherence to therapy is not yet an important issue for RLN countries but will become one in future. With advancement and improvement the country can access alternative non factor concentrates and other newer products.

Fibrin(ogen) as a Therapeutic Target: Opportunities and Challenges

Fibrinogen is one of the key molecular players in haemostasis. Thrombin-mediated release of fibrinopeptides from fibrinogen converts this soluble protein into a network of fibrin fibres that form a building block for blood clots. Thrombin-activated factor XIII further crosslinks the fibrin fibres and incorporates antifibrinolytic proteins into the network, thus stabilising the clot. The conversion of fibrinogen to fibrin also exposes binding sites for fibrinolytic proteins to limit clot formation and avoid unwanted extension of the fibrin fibres. Altered clot structure and/or incorporation of antifibrinolytic proteins into fibrin networks disturbs the delicate equilibrium between clot formation and lysis, resulting in either unstable clots (predisposing to bleeding events) or persistent clots that are resistant to lysis (increasing risk of thrombosis). In this review, we discuss the factors responsible for alterations in fibrin(ogen) that can modulate clot stability, in turn predisposing to abnormal haemostasis. We also explore the mechanistic pathways that may allow the use of fibrinogen as a potential therapeutic target to treat vascular thrombosis or bleeding disorders. Better understanding of fibrinogen function will help to devise future effective and safe therapies to modulate thrombosis and bleeding risk, while maintaining the fine balance between clot formation and lysis.

Ethyl Acetate Fraction of Helianthus tuberosus L. Induces Anti-Diabetic, and Wound-Healing Activities in Insulin-Resistant Human Liver Cancer and Mouse Fibroblast Cells

Traditional, complementary, and integrative medicine are globally accepted alternative methods for the treatment of diabetes mellitus (DM). However, the mechanism of anti-diabetic effects of Helianthus tuberosus L. remains unproven. In the present study, antioxidant and anti-diabetic activity of the tubers of H. tuberosus were studied in detail. Methanolic extracts of H. tuberosus tubers were subjected to solvent fractionation method by increasing the polarity of the solvent using n-hexane, and ethyl acetate. The obtained methanol extracts and its fractions were subjected to free radical scavenging activity (DPPH and ABTS assay) and in vitro enzyme (α-amylase and α-glucosidase) inhibition assay. Moreover, glucose uptake in insulin-resistant HepG2 cell line was analyzed. The preliminary phytochemical analysis confirmed the presence of phenolic and flavonoid compounds in the active fraction. The radical scavenging and in vitro diabetic related enzyme inhibitory activities were found to be dose dependent. The maximum ABTS⁺ and DPPH scavenging activity was documented in ethyl acetate fraction of the H. tuberosus followed by methanol extract, hexane fraction, and methanol fraction. We also found that H. tuberosus showed a less toxicity in mouse fibroblast cells and enhance the glucose uptake in insulin-resistant HepG2 cells. Besides, the ethyl acetate fraction of the H. tuberosus analyzed by UPLC-QTOF-MS-MS and GC/MS revealed the presence of phenolic compounds such as neochlorogenic acid, chlorogenic acid, caffeic acid, 5-O-(4-coumaroyl)-quinic acid, feruloylquinic acid, caffeoylquinic acid, isoxazolidine, salicylic acid β-D-glucoside, dicaffeoylquinic acid isomers, salvianolic acid derivative isomers, and 1,4 dicaffeoylquinic acid etc. Among the identified phytochemicals, six were chosen for molecular docking study to explore their its inhibitory interactions with α-amylase and α-glucosidase. Taken together, the findings of the present study suggested that phytocompounds of EAF were responsible for the significant in vitro antioxidant, wound-healing, and anti-diabetic activities.

Absence of functional compensation between coagulation factor VIII and plasminogen in double-knockout mice

Plasminogen deficiency is associated with severely compromised fibrinolysis and extravascular deposition of fibrin. In contrast, coagulation factor VIII (FVIII) deficiency leads to prolonged and excessive bleeding. Based on opposing biological functions of plasminogen and FVIII deficiencies, we hypothesized that genetic elimination of FVIII would alleviate the systemic formation of fibrin deposits associated with plasminogen deficiency and, in turn, elimination of plasminogen would limit bleeding symptoms associated with FVIII deficiency. Mice with single and combined deficiencies of FVIII (F8^-/-) and plasminogen (Plg^-/-) were evaluated for phenotypic characteristics of plasminogen deficiency, including wasting disease, shortened lifespan, rectal prolapse, and multiorgan fibrin deposition. Conversely, to specifically examine the role of plasmin-mediated fibrinolysis on bleeding caused by FVIII deficiency, F8^-/- and F8^-/-/Plg^-/- mice were subjected to a bleeding challenge. Mice with a combined deficiency in FVIII and plasminogen displayed no phenotypic differences relative to mice with single FVIII or plasminogen deficiency. Plg^-/- and F8^-/-/Plg^-/- mice exhibited the same penetrance and severity of wasting disease, rectal prolapse, extravascular fibrin deposits, and reduced viability. Furthermore, following a tail vein-bleeding challenge, no significant differences in bleeding times or total blood loss could be detected between F8^-/- and F8^-/-/Plg^-/- mice. Moreover, F8^-/- and F8^-/-/Plg^-/- mice responded similarly to recombinant FVIII (rFVIII) therapy. In summary, the pathological phenotype of Plg^-/- mice developed independently of FVIII-dependent coagulation, and elimination of plasmin-driven fibrinolysis did not play a significant role in a nonmucosal bleeding model in hemophilia A mice.

Abrogating fibrinolysis does not improve bleeding or rFVIIa/rFVIII treatment in a non-mucosal venous injury model in haemophilic rodents

Essentials The efficacy of systemic antifibrinolytics for hemophilic non-mucosal bleeding is undetermined. The effect of systemically inhibiting fibrinolysis in hemophilic mice and rats was explored. Neither bleeding nor the response to factor treatment was improved after inhibiting fibrinolysis. The non-mucosal bleeding phenotype in hemophilia A appears largely unaffected by fibrinolysis.

SUMMARY

Background Fibrinolysis may exacerbate bleeding in patients with hemophilia A (HA). Accordingly, antifibrinolytics have been used to help maintain hemostatic control. Although antifibrinolytic drugs have been proven to be effective in the treatment of mucosal bleeds in the oral cavity, their efficacy in non-mucosal tissues remain an open question of significant clinical interest. Objective To determine whether inhibiting fibrinolysis improves the outcome in non-mucosal hemophilic tail vein transection (TVT) bleeding models, and to determine whether a standard ex vivo clotting/fibrinolysis assay can be used as a predictive surrogate for in vivo efficacy. Methods A highly sensitive TVT model was employed in hemophilic rodents with a suppressed fibrinolytic system to examine the effect of inhibiting fibrinolysis on bleeding in non-mucosal tissue. In mice, induced and congenital hemophilia models were combined with fibrinolytic attenuation achieved either genetically or pharmacologically (tranexamic acid [TXA]). In hemophilic rats, tail bleeding was followed by whole blood rotational thromboelastometry evaluation of the same animals to gauge the predictive value of such assays. Results The beneficial effect of systemic TXA therapy observed ex vivo could not be confirmed in vivo in hemophilic rats. Furthermore, neither intravenously administered TXA nor congenital knockout of the fibrinolytic genes encoding plasminogen or tissue-type plasminogen activator markedly improved the TVT bleeding phenotype or response to factor therapy in hemophilic mice. Conclusions The findings here suggest that inhibition of fibrinolysis is not effective in limiting the TVT bleeding phenotype of HA rodents in non-mucosal tissues.

[Homeopathic Medicine Reduces Pain and Hemarthrosis in Moderate and Severe Hemophilia: A Multicentric Study]

BACKGROUND

Hemarthrosis is a common clinical presentation of patients with severe and moderately severe hemophilia. Severe pain, swelling, and loss of function involving knee, ankle, elbow, and shoulder joints are commonly seen. In India, except for paracetamol and some non-steroidal anti-inflammatory drugs (NSAIDs), opiate analgesics are not easily available even in the mainstay of treatment; i.e., factor concentrates are also not available regularly. Hence, there is an unmet need for exploring alternative management strategies in this condition in India.

OBJECTIVE

To assess the effect of homeopathic medicines on pain and acute hemarthrosis in hemophilia when factor concentrates are not available and paracetamol in adequate doses proves inadequate.

PATIENTS

343 patients with hemophilia (PWH) from Nashik, Mumbai, and Surat presenting with hemarthrosis were prescribed homeopathic medicines in addition to paracetamol and RICE (rest, immobilization, cold application, and elevation). They were assessed using standard techniques.

RESULTS

1,679 episodes of hemarthrosis in major joints were encountered between December 2007 and March 2014, in 343 patients. In 1,580 of the 1,679 hemarthrosis episodes (94.1%), bleeding/inflammation was arrested and pain relieved with homeopathic medication. Additional factor concentrate was required in 99 patients (4.48%). The mean pain score improved from 6.88 ± 2.118 to 1.5 ± 0.34 over 6-24 h following the homeopathic medicines (p < 0.0001). The swellings were also substantially reduced (p < 0.001). The number of joint bleeds per month was reduced significantly under the influence of therapy (p < 0.0001), showing the long-term disease-modifying effect of the treatment.

CONCLUSION

Homeopathic medicines without factor concentrates appeared to reduce bleeding and pain in PWH presenting with hemarthrosis and could have influenced the long-term frequency of bleeding.

Management of Haemophilia in Developing Countries: Challenges and Options

There are significant challenges in managing haemophilia patients in developing countries. These challenges are (i) Lack of proper health care infrastructure and human resources suitable for haemophilia care (ii) Competing health care priorities of the government. (iii) Lack of penetrance of medical insurance in the population. (iv) Lesser visibility of the haemophilia patients in health care system (v) Low awareness across the medical profession, population and the policy makers about the condition (vi) Non availability of factor concentrates (vii) Inadequate utilization of knowledge for reducing factor concentrate use. (viii) Inadequate pain relief (ix) Challenges due to inhibitor developing (x) Viral hepatitis & (xi) Lack of research publications relevant to the country are some of the challenges faced by PWH for their management in developing country. The solutions are not easy but development of a strong patient organization with linkages with World Federation of Haemophilia is an important initial step. Following that internal and international twinning, use of internal sources, strong advocacy programme targeting government, doctors, opinion makers will solve many of the challenges in the time to come.

Treatment of refractory hemorrhage with Factor XIII in a patient with hemophilia A with inhibitor

An 11-year-old male with hemophilia A and a known high-titer Factor VIII inhibitor was admitted with retroperitoneal hemorrhage. The patient was receiving infusions of recombinant activated Factor VII (rFVIIa) for a recent elbow hemorrhage when retroperitoneal bleeding commenced. Despite increased dosing of rFVIIa and a dose of activated prothrombin complex concentrate (aPCC), he continued to hemorrhage and required several blood transfusions. Factor XIII was administered 1 hour after rFVIIa and the patient demonstrated cessation of bleeding and normalization of clot strength. Factor XIII may act as an adjuvant in effective clot stabilization in patients with hemophilia and inhibitory antibodies.

Solulin increases clot stability in whole blood from humans and dogs with hemophilia

Solulin is a soluble form of thrombomodulin that is resistant to proteolysis and oxidation. It has been shown to increase the clot lysis time in factor VIII (fVIII)-deficient plasma by an activated thrombin-activatable fibrinolysis inhibitor (TAFIa)-dependent mechanism. In the present study, blood was drawn from humans and dogs with hemophilia, and thromboelastography was used to measure tissue factor-initiated fibrin formation and tissue-plasminogen activator-induced fibrinolysis. The kinetics of TAFI and protein C activation by the thrombin-Solulin complex were determined to describe the relative extent of anticoagulation and antifibrinolysis. In severe hemophilia A, clot stability increased by > 4-fold in the presence of Solulin while minimally affecting clot lysis time. Patients receiving fVIII/fIX prophylaxis showed a similar trend of increased clot stability in the presence of Solulin. The catalytic efficiencies of TAFI and protein C activation by the thrombin-Solulin complex were determined to be 1.53 and 0.02/μM/s, respectively, explaining its preference for antifibrinolysis over anticoagulation at low concentrations. Finally, hemophilic dogs given Solulin had improved clot strength in thromboelastography assays. In conclusion, the antifibrinolytic properties of Solulin are exhibited in hemophilic human (in vitro) and dog (in vivo/ex vivo) blood at low concentrations. Our findings suggest the therapeutic utility of Solulin at a range of very low doses.

Procoagulant activity in hemostasis and thrombosis: Virchow's triad revisited

Virchow's triad is traditionally invoked to explain pathophysiologic mechanisms leading to thrombosis, alleging concerted roles for abnormalities in blood composition, vessel wall components, and blood flow in the development of arterial and venous thrombosis. Given the tissue-specific bleeding observed in hemophilia patients, it may be instructive to consider the principles of Virchow's triad when investigating mechanisms operant in hemostatic disorders as well. Blood composition (the function of circulating blood cells and plasma proteins) is the most well studied component of the triad. For example, increased levels of plasma procoagulant proteins such as prothrombin and fibrinogen are established risk factors for thrombosis, whereas deficiencies in plasma factors VIII and IX result in bleeding (hemophilia A and B, respectively). Vessel wall (cellular) components contribute adhesion molecules that recruit circulating leukocytes and platelets to sites of vascular damage, tissue factor, which provides a procoagulant signal of vascular breach, and a surface upon which coagulation complexes are assembled. Blood flow is often characterized by 2 key variables: shear rate and shear stress. Shear rate affects several aspects of coagulation, including transport rates of platelets and plasma proteins to and from the injury site, platelet activation, and the kinetics of fibrin monomer formation and polymerization. Shear stress modulates adhesion rates of platelets and expression of adhesion molecules and procoagulant activity on endothelial cells lining the blood vessels. That no one abnormality in any component of Virchow's triad fully predicts coagulopathy a priori suggests coagulopathies are complex, multifactorial, and interactive. In this review, we focus on contributions of blood composition, vascular cells, and blood flow to hemostasis and thrombosis, and suggest that cross-talk among the 3 components of Virchow's triad is necessary for hemostasis and determines propensity for thrombosis or bleeding. Investigative models that permit interplay among these components are necessary to understand the operant pathophysiology, and effectively treat and prevent thrombotic and bleeding disorders.

Hemostasis research in India: past, present, and future

Hemostasis research in India has a long history considering the fact that it is one of the youngest specialities in the world. If we take creation of prothrombin time (PT) test as one of the beginning of modern hemostsis research, then the specialty is no older than 60 years. School of Tropical Medicine Kolkata, Banaras Hindu University, All India Institute of Medical Sciences at Delhi, Christian Medical College at Vellore, Post Graduate Institute of Medical Education and Research at Chandigarh, and KEM Hospital at Mumbai contributed substantially in defining various bleeding disorders in our country. Unfortunately, some of these institutes are no longer as active in the field as they used to be. Currently, the Institute of Immunohaematology at Mumbai, Chrstian medical College at Vellore, and All India Institute of Medical Sciences at Delhi are actively engaged in hemostsis research in India. Developing prenatal diagnostic technologies, mutation detection of various hemostatic disorders, developing low-cost management technologies for hemophilia, and other bleeding disorders are becoming important present day research activity in the area of hemostasis in addition to age old areas of prevalence and unusual case description studies. Entry of many new corporate hospitals, development of structured postgraduate training program in hematology, and easy availability of instruments and reagents are likely to foster further growth in this area of medical research in India in future.

Haematology research in India: past, present and future

Haematology research in India is relatively recent in origin. However the pioneers in the field not only did exemplary work when compared to advanced western countries, they also made it a point to develop centres of excellence and human resources for future of haematology work in this country. In this brief overview an effort has been made to give a taste of quality and expanse of haematology research in this country. This review does not claim to have described every bit of haematology research in this country. Our pioneers worked under extremely difficult and trying circumstances on a subject which was limited to funding available from Indian Council of Medical Research. Now the times have changed, several funding agencies in the country are able to provide substantial fund for research. Modern state of the art basic research institutions are tying up with medical colleges for good quality research and the seeds which our pioneers had planted have grown into a mighty tree. It would not be an exaggeration to say we are on the threshold of the golden era of haematology research in this country.

Very long half-life plasminogen activator inhibitor type 1 reduces bleeding in a mouse model

OBJECTIVE

To investigate the potential for the future clinical use of a very long half-life plasminogen activator inhibitor type 1 (VLHL PAI-1) as a haemostatic agent.

MATERIALS AND METHODS

We developed a VLHL PAI-1 (half-life >700 h) recombinant mutant of PAI-1 and assessed VLHL PAI-1 for its ability to inhibit fibrinolysis in vitro using human, rabbit, mouse and rat blood. Fibrin clot lysis time, monitored by thromboelastometry, was determined at various concentrations of VLHL PAI-1. Also, we determined total bleeding time and total blood loss of control, VLHL PAI-1-, tissue-type plasminogen activator (tPA)- and tPA + VLHL PAI-1-treated mice.

RESULTS

Using a thromboelastometer, mouse blood was most similar to human blood in its coagulation and fibrinolytic characteristics. We evaluated the affect of VLHL PAI-1 on haemostasis using the mouse model and showed that VLHL PAI-1 is an effective inhibitor of fibrin clot degradation. It reduced time of bleeding and total blood loss.

CONCLUSION

VLHL PAI-1 may provide an important physiological mechanism to protect clots from premature dissolution in surgical and trauma settings.

New Coagulant Agent (Ankaferd Blood Stopper) for Open Hemorrhages in Hemophilia With Inhibitor

The treatment of hemophilia A patients with inhibitor could be very expensive. Ankaferd blood stopper (ABS) is a unique folkloric medicinal plant extract, which has historically been used in Turkish traditional medicine as a hemostatic agent. In this article, a 16-year-old boy was presented with uncontrolled bleeding, despite the treatment of factor VIII, rVIIa, factor VIII inhibitor bypass activity (FEIBA), cyclophosphamide, and prednisolone at circumcision site that resolved with ABS in minutes. Our patient with hemophilia A and inhibitor is the first clinical pediatric case.

Efficacy and safety of a new-class hemostatic drug candidate, AV513, in dogs with hemophilia A

AV513 is a select fucoidan, a sulfated polysaccharide of botanical origin. It inhibits tissue factor pathway inhibitor (TFPI) activity and accelerates clotting of human hemophilia A and B plasma. In prior work, subcutaneous administration of AV513 to mice with hemophilia A improved hemostasis. The current studies were designed to evaluate potential efficacy and safety in dogs with hemophilia A (hemophilia A dogs) with minimally increased hemostasis after adenoassociated viral-FVIII gene transfer and in treatment-naive severe hemophilia A dogs. AV513 administered subcutaneously to low-FVIII dogs for multiple weeks improved hemostasis as exhibited in thromboelastography (TEG) and cuticle bleeding time (CBT) tests. Moreover, AV513 administered orally to AAV-FVIII dogs and treatment-naive severe hemophilia A dogs for a multiweek dose-escalating period yielded correction to normal ranges in both TEG and CBT end points at 5 to 15 mg/kg and 15 to 20 mg/kg dose levels, respectively. In all 3 separate studies, throughout their duration, AV513 was well tolerated by the dogs without any adverse events. Additional pharmacologic characterization of AV513 included intravenous pharmacokinetic analysis in rats. In summary, the combination of safety and efficacy in 2 global tests of hemostasis in the hemophilia A dog model indicate that further evaluation of AV513 as a hemostatic agent in hemophilia A patients is warranted.

A systematic approach to controlling problem bleeds in patients with severe congenital haemophilia A and high-titre inhibitors

The presence of inhibitory antibodies to clotting factors complicates the treatment of bleeding in haemophilia patients. For patients with high-titre inhibitors, bypassing agents are essential to haemostatic management. To determine optimal treatment practices, an international panel of physicians convened to develop a systematic treatment approach for problem bleeds (i.e. bleeds that are unresponsive to initial therapy with a single agent within a reasonable amount of time) in haemophilia patients with inhibitors.

AIM

The goal of this panel was to develop a consensus algorithm that would aid physicians in considering a variety of treatment approaches to optimize patient care by preventing extensive therapy with inadequate treatments that may lead to suboptimal patient outcomes and unnecessary costs.

METHODS

Consensus opinions were analyzed for clinical preferences at different time periods, depending on patient response to treatment. Decision-making points were defined based on the type of bleed: every 8-12 h for the first 24 h, then every 24 h thereafter for limb-threatening bleeds; every 2-4 h for 2-7 days for life-threatening bleeds.

RESULTS

The resultant consensus guidelines provide a generalized methodology to guide the treatment of problem bleeds in patients with severe haemophilia A and inhibitors, and emphasize changing treatment at the first sign of an inadequate haemostatic response. The treatment algorithms apply to both paediatric and adult patients, although the differences between the two groups were reviewed.

CONCLUSION

These guidelines are focused on optimising the timing of treatment decisions, which may lead to faster responses and improved outcomes.

Use of FEIBA for invasive or surgical procedures in patients with severe hemophilia A or B with inhibitors

Achieving hemostasis in patients with hemophilia A or B is complicated by the presence of inhibitors and is made even more difficult when these individuals require surgery. Over a 4-year period, 6 patients with inhibitors to factor VIII and 1 patient with inhibitors to factor IX underwent surgery or invasive procedures at our institution. A total of 26 procedures were performed, primarily using the bypassing agent FEIBA for bleeding control. Excellent hemostasis was obtained in all cases, adding to accumulating data indicating that FEIBA is safe and effective in hemophilia patients with inhibitors who require surgery.

Options for treating acute bleeds in addition to bypassing agents: extracorporeal immunoadsorption, FVIII/FIX, desmopressin and antifibrinolytics

Inhibitor patients do not always respond satisfactorily to treatment with bypassing agents, and options to the standard practice are sometimes needed. Temporary inhibitor removal may be achieved using extracorporeal immunoadsorption. This technique uses a column system including either protein A or antihuman IgG. Immunoadsorption may be used as part of an immune tolerance protocol, or in the case of acute bleeds or prior to surgery, thus rendering the patient more responsive to ordinary replacement therapy with factor VIII or factor IX. Desmopressin is a valuable haemostatic agent in many situations and can be especially recommended in mild haemophilia complicated by an inhibitor. Antifibrinolytics are often administered as an adjunct therapy to the treatment protocol and have also been reported to have a direct anti-inhibitor effect.

Application of current knowledge to the management of bleeding events during immune tolerance induction

The development of inhibitors to factor VIII is the most serious adverse event associated with the treatment of haemophilia A, predisposing patients to uncontrollable haemorrhage, disability and premature death. Eradication of inhibitors via immune tolerance induction (ITI) is effective in the majority of patients, but may require months to years to achieve success. In the interim, the treatment and prevention of acute bleeding episodes are primary foci of care. Regrettably, there is a paucity of information regarding management of bleeding episodes in inhibitor patients undergoing tolerization. Until specific data from ongoing clinical trials are available to provide more guidance in this patient group, it is reasonable and useful to rely on the broader base of medical literature pertaining to patients not being tolerized to deduce strategies for controlling acute and perioperative bleeding episodes in inhibitor patients during ITI.

High dose factor VIIa improves clot structure and stability in a model of haemophilia B

Factor IX (FIX) deficiency results in haemophilia B and high dose recombinant activated factor VII (rFVIIa) can decrease bleeding. Previously, we showed that FIX deficiency results in a reduced rate and peak of thrombin generation. We have now used plasma and an in vitro coagulation model to examine the effect of these changes in thrombin generation on fibrin clot structure and stability. Low FIX delayed the clot formation onset and reduced the fibrin polymerisation rate. Clots formed without FIX were composed of thicker fibrin fibres than normal. rFVIIa shortened the clot formation onset time and improved the fibre structure of haemophilic clots. We also examined clot formation in the presence of a fibrinolytic challenge by including tissue plasminogen activator or plasmin in the reaction milieu. In these assays, normal FIX levels supported clot formation; however, clots did not form in the absence of FIX. rFVIIa partially restored haemophilic clot formation. These results were independent of the effects of the thrombin-activatable fibrinolysis inhibitor. Our data suggest that rFVIIa enhances haemostasis in haemophiliacs by increasing the thrombin generation rate to both promote formation of a structurally normal clot and improve clot formation and stability at sites with high endogenous fibrinolytic activities.

Epsilon aminocaproic acid reduces transfusion requirements in patients with thrombocytopenic hemorrhage

BACKGROUND

Epsilon aminocaproic acid (EACA) is an antifibrinolytic drug that has been used to control hemorrhage by stabilizing the thrombus. It has been used in thrombocytopenic patients largely on an empiric basis.

METHODS

Concerns regarding side effects have limited the use of this drug. The authors reviewed their experience with EACA at the Cleveland Clinic Foundation from 1997 to 2003.

RESULTS

Of 77 patients with thrombocytopenic hemorrhage, 51 (66%) patients achieved a complete response and 13 (17%) patients achieved a partial response, resulting in a decrease in platelet and red blood cell transfusions. Adverse effects were manageable in this set of patients with severe underlying disease.

CONCLUSIONS

Based on this experience, EACA may be a valuable adjunctive therapy in the treatment of patients with thrombocytopenic hemorrhage.

Trehalose and 6-aminohexanoic acid stabilize and renature glucose-6-phosphate dehydrogenase inactivated by glycation and by guanidinium hydrochloride

A number of naturally occurring small organic molecules, primarily involved in maintaining osmotic pressure in the cell, display chaperone-like activity, stabilizing the native conformation of proteins and protecting them from various kinds of stress. Most of them are sugars, polyols, amino acids or methylamines. In addition to their intrinsic protein-stabilizing activity, these small organic stress molecules regulate the activity of some molecular chaperones, and may stabilize the folded state of proteins involved in unfolding or in misfolding diseases, such as Alzheimer's and Parkinson's diseases, or alpha1-antitrypsin deficiency and cystic fibrosis, respectively. Similar to molecular chaperones, most of these compounds have no substrate specificity, but some specifically stabilize certain proteins, e.g., 6-aminohexanoic acid (AHA) stabilizes apolipoprotein A. In the present work, the capacity of 6-aminohexanoic acid to stabilize non-specifically other proteins is demonstrated. Both trehalose and AHA significantly protect glucose-6-phosphate dehydrogenase (G6PD) against glycation-induced inactivation, and renatured enzyme already inactivated by glycation and by guanidinium hydrochloride (GuHCl). To the best of our knowledge, there are no data on the effect of these compounds on protein glycation. The correlation between the recovery of enzyme activity and structural changes indicated by fluorescence spectroscopy and Western blotting contribute to better understanding of the protein stabilization mechanism.