Academic literature on the topic 'Pro-hemostatic agents'

Recently, local hemostatic agents (LHA) have become increasingly popular abroad and in our country. They act in a targeted way and can be used both in damage to large vessels and in diffuse bleeding. In the article, chemical nature, physical and chemical characteristics of materials and mechanisms of LHA activity are considered, directions of their improvement are shown. LHA are mostly classified by mechanism of action. To date, the popular groups of hemostatic agents are «mucoadhesive agents» (chitosan, amylopectin) and «coagulation factors concentrators» (zeolites, kaolin). Other authors distinguish the group of «aggregation and adhesion stimulants» (collagen, cellulose). Here, representatives of these groups have common characteristics – very high porosity and hydration ability. Another group includes substances that «promote protein denaturation» (inorganic salts of metals, as well as salts of acrylic acid and its derivatives). Polyacrylates are the basis of adhesives with hemostatic activity. However, most modern LHA are complex drugs and it is just this group that is most promising. All means, from hemostatic sponges produced by Zelyonaya Dubrava (Russia) and Nycomed, Takeda (Austria, Norway), and to hemostatic materials of MedTrade manufacture (Great Britain), Etiguette and Z-Medica (USA), combine sorption and, actually, thrombotic properties. The trademarks often imply original compositions and, especially, technologies: Quick Relief, BioSeal, BallistiClot, Hemaderm, CELOX Gauze PRO, OMNI-STAT Hemostatic Gauze for minor external bleeding. The most effective LHA are those based on chitosan and kaolin in the form of dressings with embedded clot-forming substance, for example, with artificial platelets or other coagulation factors.

AbstractThe purpose of this study was to examine the safety of the long-term application of QuikClot Combat Gauze, ChitoGauze PRO and Celox Gauze using a swine model. The study was conducted on nine pigs weighing approximately 30 kg, which were randomly divided into three groups. Under deep anesthesia, the pigs underwent complete transverse cutting of the femoral artery in the groin region. Hemostatic dressings were left in the wound for 24 hours. The animals were euthanized 24 hours after dressing application. In each group, macroscopic and microscopic severe changes and shock symptoms were observed in the lungs, liver, kidneys and heart. Fibrino-gaseous embolic material was found in the pulmonary artery of each group and in the lung vessels of the animals from the ChitoGauze PRO and Celox Gauze groups. In conclusion, the long-term application of the evaluated hemostatic dressings has the risk of coagulopathy and reaching the progressive stage of shock. The residues from the hemostatic dressings can ingress into the systemic circulation, thereby increasing the risk of embolus formation. Because of these harmful effects, the evaluated hemostatic dressings are not appropriate for long-term use. Future studies are needed on the consequences of the long-term application of these hemostatic agents.

Abstract BH3 mimetics are a new class of proapo-ptotic anticancer agents that have shown considerable promise in preclinical animal models and early-stage human trials. These agents act by inhibiting the pro-survival function of one or more Bcl-2–related proteins. Agents that inhibit Bcl-xL induce rapid platelet death that leads to thrombocytopenia; however, their impact on the function of residual circulating platelets remains unclear. In this study, we demonstrate that the BH3 mimetics, ABT-737 or ABT-263, induce a time- and dose-dependent decrease in platelet adhesive function that correlates with ectodomain shedding of the major platelet adhesion receptors, glycoprotein Ibα and glycoprotein VI, and functional down-regulation of integrin αIIbβ3. Analysis of platelets from mice treated with higher doses of BH3 mimetics revealed the presence of a subpopulation of circulating platelets undergoing cell death that have impaired activation responses to soluble agonists. Functional analysis of platelets by intravital microscopy revealed a time-dependent defect in platelet aggregation at sites of vascular injury that correlated with an increase in tail bleeding time. Overall, these studies demonstrate that Bcl-xL–inhibitory BH3 mimetics not only induce thrombocytopenia but also a transient thrombocytopathy that can undermine the hemostatic function of platelets.

Fibrinolysis is an important hemostatic process initiated either by tissue plasminogen activator (tPA) or pro-urokinase (pro-UK) released from endothelial cells. These agents act preferentially on plasminogen by converting it to the active molecule plasmin. This initiates the clot lysis process, which may take several days for completion. Most patients with end-stage renal disease (ESRD) have PTFE grafts for chronic hemodialysis. When these grafts are thrombosed, they are either surgically revised or percutaneously thrombolysed. When these measures fail another access is created without removing the clotted graft. However, it is possible that de-clotting of these thrombosed PTFE grafts can occur spontaneously. Once the graft develops an endothelial lining, these cells can contribute to the fibrinolytic process by secreting tPA or pro-UK. Because this endothelial lining may be less developed than that of a normal vessel, the fibrinolytic process may occur at a slower rate or not at all. Frequent cannulation during hemodialysis can denude existing endothelium, further contributing to the inadequacy of the graft to initiate thrombolysis. In practice, once the PTFE is clotted, the graft is ignored if it is not considered for declotting. In such circumstances the re-canalization process could be overlooked, resulting in the unnecessary placement of additional accesses. Presented here are three patients with clotted grafts in which re-canalization occurred without intervention.

INTRODUCTION: Spontaneous non-traumatic intracranial hemorrhage causes high morbidity and mortality. Clinical pathways for the management of acute ischemic stroke are well established but fall short in identifying intracranial hemorrhage, preventing early therapy. METHODS: Using Class 1 recommendations from the AHA/ASA Spontaneous Intracranial Hemorrhage Guidelines, our multi-disciplinary stroke team developed a hyper-acute clinical pathway. Once the hemorrhagic stroke patient was identified, protocolized measures were immediately initiated to lower systolic blood pressure to 140 mmHg, institute factor replacement therapies in coagulopathic patients and anti-platelet reversal when appropriate. Key performance indicators and quality metrics were established to compare post-intervention groups to the baseline cohort. RESULTS: Of 180 patients, 113 and 67 patients were treated pre- and post-protocol, respectively. From pre- to post-protocol, diagnosis of hemorrhagic stroke using the alert increased from 59% to 81%. Anti-hypertensive initiation within 60 minutes increased from 79.5% to 88.7%, with the average time from CT result decreasing from 32.7 to 21.7 minutes. Time to reversal agent decreased from 53 to 23 minutes for pro-coagulation agents and 106 to 55 minutes for DDAVP. Reversal agent initiation within 60 minutes of CT result increased from 66.6% to 100% for pro-coagulation agents and 28.5% to 84.6% for DDAVP. CONCLUSIONS: The initiation of this management protocol for hemorrhagic stroke resulted in a higher proportion of patients being rapidly identified and earlier initiation of anti-hypertensive and hemostatic therapies. These processes are the key to important interventions designed to reduce injury extension associated with intracranial hemorrhage, like “time to thrombolysis” measures for acute ischemic stroke.

Abstract The pharmacokinetic challenges of warfarin therapy have led to the development of new oral anticoagulants (NOACs) that directly inhibit coagulation factor Xa (FXa). While these new drugs (including rivaroxaban and apixaban) have many benefits over warfarin, no approved strategy exists to reverse their anticoagulant effects in the event of life-threatening bleeding or emergent need for surgery. The most promising reversal strategy in clinical development is a catalytically inactive form of FXa (Gla-domainless FXaS195A, GD-FXaS195A) that binds the NOAC with high affinity to relieve inhibition of endogenous FXa. In principle, removing the inhibitor through molecular engagement is attractive, especially when administered before bleeding begins (e.g. pre-surgery), and there is in vivo evidence to support the efficacy of GD-FXaS195A as a pre-injury antidote for direct FXa inhibitors. However, since GD-FXaS195A is a scavenger of the inhibitor and not a pro-hemostatic agent, GD-FXaS195A may not be effective if given after a bleeding episode has begun. Moreover, its mechanism of action necessitates a 1:1 ratio of GD-FXaS195A to neutralize the inhibitor. Thus, high doses (hundreds of milligrams of protein) will likely be required in humans. We hypothesized that a pro-hemostatic bypassing agent might be able to reverse the effects of direct FXa inhibitors no matter when it is administered, and with high potency. To evaluate this, we used a variant of FXa (FXaI16L) that is more zymogen-like than wild-type (wt)-FXa. This "zymogen-like" variant has lower catalytic activity in in vitro assays compared to wt-FXa due to impaired active site maturation. It is also resistant to active site inhibitors including plasma protease inhibitors, resulting in an extension of its plasma half-life (>30 minutes vs ~1 minute for wt-FXa). Importantly, its activity is rescued upon binding to its cofactor FVa in vivo, and we have previously shown that FXaI16L bypasses the intrinsic pathway defect in hemophilic mice. Here we evaluated whether FXaI16L might also be able to bypass direct FXa inhibitors using in vitro thrombin generation assays (TGAs) and two in vivo injury models in mice, and directly compared FXaI16L to GD-FXaS195A. In TGA experiments, 500 nM rivaroxaban decreased peak thrombin generation to 23% of that observed in normal human plasma (NHP). This decreased thrombin generation could be reversed by the addition of 3 nM human (h)FXaI16L which normalized peak thrombin generation. In comparative studies, hFXaI16L was 300-fold more potent than GD-FXaS195A in TGA assays. These data highlight that differences in mechanism of action (pro-hemostatic vs. scavenger) will have a huge impact on amounts of protein needed to revive thrombin generation. This was further reflected in in vivo studies. In invivo experiments with wild-type mice using 7.5% FeCl3 to induce carotid artery thrombosis, 1 mg/kg rivaroxaban prevented formation of occlusive thrombi. 30 minutes after the initial FeCl3 injury to rivaroxaban-treated mice, infusion of 0.25 mg/kg murine (m)FXaI16L normalized the phenotype, causing rapid occlusion at the injury site within 5 minutes. In contrast, we did not observe carotid artery occlusion with administration of up to 25 mg/kg GD-FXaS195A 30 minutes after the injury to rivaroxaban-treated mice (Fig. 1). When both rivaroxaban and the reversal agent were given prior to the injury, both mFXaI16L (0.5 mg/kg) and GD-FXaS195A (25 mg/kg) were effective at reversing the inhibition. Furthermore, using intravital microscopy to examine thrombus formation at the site of laser injury to mouse cremasteric arterioles, we found that 1 mg/kg rivaroxaban completely abrogated fibrin deposition and substantially reduced platelet accumulation. Treatment with1 mg/kg mFXaI16L substantially increased platelet and fibrin deposition at the site of laser injury. Figure 1 Carotid occlusion time when the reversal agent was infused 30 minutes after the FeCl3 injury. Figure 1. Carotid occlusion time when the reversal agent was infused 30 minutes after the FeCl3 injury. Taken together, these data provide strong support for the in vivo efficacy and potency of FXaI16L as a potential pro-hemostatic bypass agent to reverse direct FXa inhibitors. The data also illustrate that antidotes like GD-FXaS195A may not be as effective as pro-hemostatic agents like FXaI16L following an injury, and we predict that effective reversal of NOACs will require a nuanced approach that uses an antidote or a bypassing agent depending on the clinical scenario. Disclosures Jasuja: Pfizer: Employment. Patel-Hett:Pfizer: Employment. Fruebis:Pfizer: Employment. Pittman:Pfizer: Employment. Camire:Pfizer: Consultancy, Patents & Royalties, Research Funding.

Background Patients with severe congenital hemophilia A (CHA) have a 25-40% lifetime risk of alloantibody (inhibitor) development to FVIII. Patients with acquired hemophilia A (AHA) spontaneously develop neutralizing autoantibodies to factor VIII. In both cases, patients require pro-hemostatic therapy with bypassing agents: recombinant factor VIIa (rFVIIa), activated prothrombin complex concentrate (aPCC) and more recently recombinant porcine factor VIII (rpFVIII). Anti-human FVIII (hFVIII) inhibitors typically bind to the A2 and C2 domains of the FVIII molecule. RpFVIII is an effective pro-hemostatic treatment for AHA and CHA given the immunologic difference in the A2 and C2 domains of the rpFVIII while maintaining sufficient hFVIII homology to act as an effective cofactor to human FIX in the intrinsic tenase. However, some anti-hFVIII antibodies cross-react with rpFVIII and may interfere with its hemostatic function. Cross-reacting antibodies were reported in 35% of subjects in a phase II/III trial prior to initiation of rpFVIII. Moreover, de novo rpFVIII inhibitors may develop during or after the treatment with rpFVIII and may affect its hemostatic function. Here we describe the largest case series to date on baseline cross-reactivity of rpFVIII inhibitors and post-treatment de novo inhibitor development in patients with CHA and AHA to address the paucity of published literature in this area. Aim First, we describe the frequency of baseline cross-reacting rpFVIII inhibitors in patients with AHA and CHA (with inhibitors) at our institution. Second, we describe the effect of baseline rpFVIII antibodies on FVIII recovery after treatment with rpFVIII. We also describe the frequency and timing of de novo rpFVIII inhibitor development after exposure to rpFVIII. Methods Institutional research ethics board approval was obtained. Electronic charts of patients admitted to our institution with AHA or CHA who underwent testing for rpFVIII inhibitors were reviewed retrospectively. RpFVIII inhibitor assay is performed in the special coagulation laboratory using the Nijmegen modified Bethesda assay. The patient sample is initially heat-treated at 57 Results Twenty-seven patients (7 CHA, 20 AHA) underwent testing for porcine inhibitors since assay availability in 2016. 61% (5/7 CHA, 11/20 AHA) of patients had a detectable rpFVIII inhibitor prior to exposure to rpFVIII; median titer 1.6 BU/ml (range 0.6-192). Eight patients with AHA with baseline cross-reacting inhibitors received rpFVIII. Of those, three achieved an initial FVIII recovery beyond 100% (132%, 148% and 177%) after approximately 100U/kg of rpFVIII and all three had very low anti-rpFVIII Bethesda titers (0.70, 0.85 and 0.9 BU/ml). Five patients did not achieve a FVIII recovery above 50% (46%, 46%, 40%, 36% and 0%) despite approximately 100U/kg of rpFVIII. Most patients who received rpFVIII were tested weekly for the duration of their treatment or hospital stay. Upon discharge, patients who were seen in clinic for follow up were tested for anti-hFVIII and anti-rpFVIII. Two AHA patients without a baseline inhibitor who received rpFVIII treatment developed a de novo inhibitor after 20 days (1 BU/ml) and 133 days (12 BU/ml), respectively. One AHA patient had a rise in baseline anti-rpFVIII titer after exposure to rpFVIII. Conclusion In conclusion, we found that 61% of patients with AHA and CHA tested for rpFVIII inhibitors had a detectable baseline cross-reacting inhibitor which is higher than previously described. Of those patients with a baseline inhibitor treated with rpFVIII, only 37.5% of patients had an appropriate rise in FVIII. Finally, 13% of patients without baseline inhibitors developed a de novo inhibitor after exposure to rpFVIII, an incidence comparable to previously published findings. Disclosures Pavenski: Bioverativ: Research Funding; Alexion: Honoraria, Research Funding; Octapharma: Research Funding; Shire: Honoraria; Ablynx: Honoraria, Research Funding. Teitel:BioMarin: Consultancy; CSL Behring: Consultancy; Octapharma: Consultancy; Novo Nordisk: Consultancy; Shire: Consultancy; Pfizer: Consultancy, Research Funding; Bayer: Consultancy, Research Funding. Sholzberg:Takeda: Honoraria, Research Funding; Baxter: Honoraria, Research Funding; Baxalta: Honoraria, Research Funding. OffLabel Disclosure: Recombinant porcine factor VIII is used to treated patients with congenital hemophilia A with allo inhibitors

Abstract Introduction: Emicizumab (ACE910), an antibody to FIX(a) and FX(a), is currently under investigation for treatment of hemophilia with inhibitors. In a phase III trial, two thromboembolic complications and three cases of microangiopathy were reported in patients on ACE910 prophylaxis [Oldenburg et al. NEJM 2017], whose breakthrough bleeding was treated with activated prothrombin complex concentrate aPCC (FEIBA) or aPCC and rFVIIa. We generated a sequence identical analogue (SIA) to ACE910 and analyzed its synergistic interplay with bypassing agents. Aims: To monitor in vitro the pro-coagulant activity of SIA ACE910 in the presence of FEIBA and rFVIIa, and detect the source of excessive coagulation induced by SIA ACE910 combined with FEIBA. Methods: A sequence identical analogue (SIA) to ACE910 was expressed in HEK293 cells, purified as previously described [Sampei et al. PLoS One 2013], and analyzed in several global hemostatic assays at different concentrations and test conditions using plasma and whole blood assays. In thrombin generation (TG) experiments, platelet-poor plasma (PPP) from hemophilia A inhibitor patients and hemophilia A plasma reconstituted with platelets from 3 healthy donors (PRP) was used. A normal TG range was established in healthy donor plasma. Therapeutic concentrations of SIA ACE910 (20-600 nM) were tested alone and with FEIBA (0.05-1 U/mL) or rFVIIa (0.88-5.25 µg/mL). To measure FEIBA components' contribution to the synergistic effect with SIA ACE910, PPP was spiked with select FEIBA components at concentrations corresponding to 0.5 U/mL FEIBA in combination with the antibody. Thrombus formation was analyzed in FVIII-inhibited blood using rotational thromboelastometry (ROTEM) and Total Thrombus-formation Analysis System (T-TAS). Results: Normal peak thrombin was 47-144 nM for PPP and 88-231 nM for PRP. rFVIIa and FEIBA had an additive effect on TG in combination with SIA ACE910 in both plasma types. Combined with rFVIIa (0.88 µg/mL) or FEIBA (0.5 U/mL), SIA ACE910 (600 nM) induced a ~2- and ~16-fold increase over SIA ACE910 alone. SIA ACE910+rFVIIa did not reach the normal range, while SIA ACE910+FEIBA far exceeded it. Adding individual FEIBA components to PPP showed that FIX was, with a half-maximal effect, the main driver for enhanced TG, followed by FIXa. formation in FVIII-inhibited whole blood using ROTEM and T-TAS confirmed the excessive effect of SIA ACE910+FEIBA. In ROTEM, FEIBA and rFVIIa reduced clotting time to shorter than normal, whereas SIA ACE910 had only little effect. Moreover, adding SIA ACE910 to rFVIIa exerted no effect over rFVIIa alone. Conclusion: Combining SIA ACE910 at plasma concentrations observed in patients [Oldenburg et al. NEJM 2017] with FEIBA induced excessive thrombin generation and faster clot formation. In vitro, this effect is mainly mediated by FEIBA component FIX. ACE910 binds to FIX and FIXa to the same extent, and displays its pro-coagulant effect via an unregulated mechanism. Therefore, careful judgement is needed in treating breakthrough bleeds with FEIBA. Disclosures Hartmann: Shire: Employment. Feenstra: Shire: Employment. Knappe: Shire: Employment. Dockal: Baxalta: Patents & Royalties; Shire: Employment, Equity Ownership; Baxter: Equity Ownership, Patents & Royalties. Scheiflinger: Baxter: Equity Ownership; Shire: Employment, Equity Ownership.

The incidence of venous thromboembolism (VTE) in patients with primary brain tumors varies be tween 1 and 60%. This variability in incidence is due to study differences in (a) methods of diagnosis of VTE— i.e., diagnosis at autopsy or clinical diagnosis; (b) amount of time from surgery to VTE diagnosis; (c) proportion of patients receiving deep venous thrombosis (DVT) pro phylaxis ; (d) clinical risk factors associated with VTE, such as paresis, prior thrombotic disease, and chemother apy; and (e) tumor location and histology. The etiology of VTE in patients with primary brain tumors is unknown. The preoperative hemostatic abnormalities noted in clin ical studies have been most consistent with compensated disseminated intravascular coagulation (DIC). These ab normalities, however, appear to be of little predictive value for the subsequent development of VTE. Studies involving brain tumor tissue or cell cultures have impli cated factors released by the tumor or surrounding neural tissue that activate the coagulation system or inhibit fi brinolysis. Recommendations for VTE prophylaxis in clude (a) earliest possible ambulation; (b) intermittent pneumatic compression in all nonambulatory patients preoperatively and postoperatively; and (c) s.c. heparin in high-risk patients. The role of low-molecular-weight heparin in VTE prophylaxis has not been established. Patients with malignant brain tumors can be safely anti coagulated with heparin and warfarin if these agents are carefully monitored. Of 197 patients in seven series who received anticoagulants, only 5 (2.5%) had intracranial bleeding. Vena caval filters and thrombectomy are rarely required. Thrombolytic therapy is contraindicated. Key Words: Venous thromboembolism—Deep venous throm bosis—Malignant brain tumors.

L’hémorragie intracérébrale (HIC) est le sous-type d’AVC le plus grave. Stopper le saignement à l’aide d’agents pro-hémostatiques est une stratégie thérapeutique prometteuse qui demeure limitée par des effets secondaires graves tels qu’une thrombose incontrôlée. Dans la présente étude, nous avons développé une stratégie thérapeutique originale pour l’HIC basée sur l’administration de vésicules extracellulaires (VE) qui peuvent déclencher la cascade de coagulation spécifiquement au site du saignement actif. Nous avons d’abord généré de grandes quantités de VE à partir de monocytes THP-1 stimulés au TNF dans des bioréacteurs. Ces VE dérivées de monocytes présentaient une taille moyenne d’environ 300 nm, une activité du facteur tissulaire (FT) pro-hémostatique élevée réduisant le temps de coagulation de manière dose- et FT-dépendante et une expression élevée de la protéine de ciblage à leur surface (P-Selectin Glycoprotein Ligand 1, PSGL-1). Dans des modèles pré-cliniques d’HIC chez la souris, l’injection intraveineuse de VE dérivées de monocytes a amélioré les résultats de l’AVC de manière dose-dépendante. Les VE à 1mg/kg ont empêché la croissance des hématomes de 43% et amélioré le devenir neurologique à 24h par rapport aux souris témoins (p<0.01, n=15/groupe). Ces effets étaient également présents dans des modèles plus sévères d’HIC (souris traitées à l’enoxaparine ou à la warfarine). Il est important de noter que l’effet bénéfique a été bloqué lors de l’utilisation d’anticorps bloquant le FT ou le PSGL-1, suggérant ainsi que l’activité pro-hémostatique et la capacité de cibler les dommages au niveau des vaisseaux cérébraux sont obligatoires pour l’efficacité thérapeutique des VE. Pour conclure, les VE exogènes dérivées de monocytes portant du FT et du PSGL-1 améliorent les résultats après une HIC induite par la collagénase en agissant comme des pansements hémostatiques intravasculaires
Intracerebral hemorrhage (ICH) is the most severe stroke subtype. Stopping the ongoingbleeding using pro-hemostatic agents is a promising therapeutic strategy that remains limitedby serious side effects such as uncontrolled thrombosis. In the present study, we developed anoriginal therapeutic strategy for ICH based on the administration of nanosized extracellularvesicles (EVs) that can trigger the coagulation cascade specifically at the site of active bleeding.We first generated large amounts of EVs from TNF-stimulated THP-1 monocytes in bioreactors.Those monocyte-EVs presented a mean size of around 300 nm, a high pro-hemostatic activityreducing the clotting time in a dose- and TF-dependent manner and a high expression of atargeting protein on their surface (P-Selectin Glycoprotein Ligand 1, PSGL-1). In preclinicalmodels of ICH in mice, intravenous injection of mEVs improved stroke outcome in a dosedependentmanner. mEVs at 1 mg/kg prevented hematoma growth by 43% and improvedneurological score at 24h compared to control mice (p<0.01, n=15/group). These effects werealso present in more severe models of ICH (enoxaparin or warfarin treated mice). Importantly,the beneficial effect was blocked when using antibodies blocking either TF or PSGL-1,suggesting that both the pro-coagulant activity and the ability to target damaged brain vesselsare mandatory for the therapeutic efficacy of EVs. To conclude, exogenous mEVs bearing TFand PSGL-1 improve outcome after collagenase-induced ICH by acting as intravascularhemostatic patches