Generation of an anticoagulant aptamer that targets factor V/Va and disrupts the FVa-membrane interaction in normal and COVID-19 patient samples.

Coagulation cofactors profoundly regulate hemostasis and are appealing targets for anticoagulants. However, targeting such proteins has been challenging because they lack an active site. To address this, we isolate an RNA aptamer termed T18.3 that binds to both factor V (FV) and FVa with nanomolar affinity and demonstrates clinically relevant anticoagulant activity in both plasma and whole blood. The aptamer also shows synergy with low molecular weight heparin and delivers potent anticoagulation in plasma collected from patients with coronavirus disease 2019 (COVID-19). Moreover, the aptamer's anticoagulant activity can be rapidly and efficiently reversed using protamine sulfate, which potentially allows fine-tuning of aptamer's activity post-administration. We further show that the aptamer achieves its anticoagulant activity by abrogating FV/FVa interactions with phospholipid membranes. Our success in generating an anticoagulant aptamer targeting FV/Va demonstrates the feasibility of using cofactor-binding aptamers as therapeutic protein inhibitors and reveals an unconventional working mechanism of an aptamer by interrupting protein-membrane interactions.

Acquired factor V inhibitor: a nation-wide study of 38 patients.

Acquired factor V inhibitor (AFVI) is an extremely rare disorder that may cause severe bleeding. To identify factors associated with bleeding risk in AFVI patients, a national, multicentre, retrospective study was made including all AFVI patients followed in 21 centres in France between 1988 and 2015. All patients had an isolated factor V (FV) deficiency <50% associated with inhibitor activity. Patients with constitutional FV deficiency and other causes of acquired coagulation FV deficiencies were excluded. The primary outcome was incident bleeding and factors associated with the primary outcome were identified. Thirty-eight (74 [36-100] years, 42·1% females) patients with AFVI were analysed. Bleeding was reported in 18 (47·4%) patients at diagnosis and in three (7·9%) during follow-up (7 [0·2-48.7] months). At diagnosis, FV was <10% in 31 (81·6%) patients. Bleeding at diagnosis was associated with a prolonged prothrombin time that strongly correlated with the AFVI level measured in plasma {r = 0·63, 95% confidence interval (CI) [0·36-0·80], P < 0·05}. Bleeding onset during follow-up was associated with a slow AFVI clearance (P < 0·001). The corresponding receiver operating characteristics curve showed that AFVI clearance was predictive of bleeding onset with an AFVI clearance of seven months with a sensitivity of 100% (95% CI: 29-100) and a specificity of 86% (95% CI: 57-98, P = 0·02). Kaplan-Meier analysis showed that AFVI clearance >7 months increased the risk of bleeding by 8 (95% CI: [0·67-97], P = 0·075). Prothrombin time at diagnosis and time for clearance of FV inhibitor during follow-up are both associated with bleeding in patients with AFVI.

Acquired factor V inhibitor in the setting of coronavirus disease 2019 infection.

Factor V inhibitors are a rare cause of life-threatening bleeding. We present a case of an acquired factor V inhibitor likely caused by coronavirus disease 2019 infection. Bleeding was manifested by severe anemia requiring frequent red-cell transfusion, left psoas muscle hematoma, and left retroperitoneal cavity hematoma. Factor V activity was less than 1% and the factor V inhibitor titer was 31.6 Bethesda units. Severe acute respiratory syndrome coronavirus 2 RNA testing of the nasopharynx was positive 2 weeks before presentation and continued to be positive for 30 days. The patient failed treatment with intravenous immunoglobulin and dexamethasone. Three cycles of plasmapheresis with fresh frozen plasma replacement resulted in correction of the bleeding and laboratory coagulopathy. This is the first reported case of a factor V inhibitor in a coronavirus disease 2019 patient and suggests that plasmapheresis may be a successful treatment strategy.

[Acquired factor V inhibitor].

Since acquired factor V inhibitor (FV-INH) has been first reported in Germany in 1955, about 200 cases have been recorded globally. The incidence of FV-INH is extremely low, with a rate of 0.023-0.09 per million persons per year. FV-INH formation is caused by infection, use of antibiotics and other drugs, surgery, and diseases, including malignancy and autoimmune disorder. Some patients with FV-INH present with abnormal clinical laboratory test results but have no hemorrhagic symptoms. Others experience life-threatening bleeding. Moreover, thrombosis can sometimes occur. The diagnosis is based on prolonged prothrombin time (PT) and activated partial thromboplastin time (APTT), an inhibitor pattern shown by a cross-mixing test of PT and APTT, decreased factor V activity, and detection of FV-INH. Treatment includes hemostatic and immunosuppressive therapy. However, in some cases, the monitoring of progression alone is appropriate. In terms of hemostatic therapies, infusion of platelet concentrates and administration of recombinant factor VIIa are highly useful. However, no definitive treatment strategy has been established. In about 50% of cases, FV-INH is eliminated spontaneously. Therefore, immunosuppressive therapy is recommended only for hemorrhagic patients or those at high risk of hemorrhage. Prednisolone is generally used for the management of immunosuppression. However, some reports have shown that the administration of rituximab, cyclophosphamide, and intravenous immunoglobulin and plasma-exchange can be utilized as treatments.

Haemodialysis Tunisian patient with acquired factor V inhibitor associated to arteriovenous shunt thrombosis.

Factor V deficiency is a rare hemostatic disorder. It may present with a diverse spectrum of symptoms due to a variety of mechanisms including development of autoantibodies associated with a number of conditions. We report a first case of factor V deficiency in Tunisian hemodialysis patient due to an autoantibody most likely secondary to antibiotic exposure responsible for an arteriovenous shunt thrombosis rather than bleeding. We discuss here the clinical and biological features of acquired factor V inhibitor and provide a short review of the current literature.

[Acquired factor V inhibitor associated with apixaban].

Acquired factor V inhibitor is an acquired coagulation disorder that is rare. We report the case of a patient who was treated with apixaban and developed acquired factor V inhibitor. The patient was a 76-year-old man who has been on long-term treatment with aspirin and clopidogrel after undergoing percutaneous coronary intervention (PCI) and carotid artery stenting. In June, he developed a cerebral infarction six days after the second PCI. Apixaban was added to his treatment regimen for cariogenic cerebral embolism. Three months later, intramuscular hemorrhage occurred in his left leg after a fall. However, the hemorrhage improved upon aspirin withdrawal. Unexpectedly, subcutaneous and intramuscular hemorrhage recurred three months after the patient commenced anticoagulation therapy. At this time, the APTT was 242.5 seconds and the PT was over the reference range. Although clopidogrel and apixaban were discontinued, these abnormalities did not improve. However, a cross-mixing test showed an inhibitor pattern, with factor V activity being less than 1% and its inhibitor level being 8.0 BU/ml. Based on these findings, the patient was finally diagnosed of acquired factor V inhibitor. One month after prednisolone administration at 20 mg/day, the PT and APTT were normalized, and prednisolone was tapered off. Although the use of dabigatran has been associated with iatrogenic acquired factor V inhibitor, we describe the first case of acquired factor V inhibitor associated with direct Xa inhibitor.

Acquired Factor V Inhibitor with Hemorrhagic Symptoms after Prasugrel Hydrochloride Treatment.

Acquired factor V inhibitor (AFVI) is a rare coagulopathy. It may be triggered by specific antigens such as antibiotics. We herein report the first case of AFVI after treatment with prasugrel hydrochloride (prasugrel) in an 80-year-old male who underwent percutaneous coronary intervention because of angina pectoris 6 years ago and was initiated on aspirin and ticlopidine hydrochloride. He was switched from ticlopidine hydrochloride to prasugrel before undergoing percutaneous coronary intervention for myocardial infarction. Fifteen days later, he developed sudden nasal hemorrhage, hematuria, and systemic purpura. Coagulation tests revealed prolonged prothrombin time-international normalized ratio (11.35) and activated partial thromboplastin time (170 s). The coagulation factor profile revealed a decreased FV activity (1%). The Bethesda assay for FV inhibitor was positive. AFVI was diagnosed; prasugrel was immediately discontinued, and administration of recombinant activated factor VII and prednisolone were initiated. Hemorrhagic symptoms immediately disappeared; FV activity improved, and the FV inhibitor titer was normalized.

Successful Management of Acquired Factor V Inhibitor by Monitoring Factor V Activity, Antigen, and Inhibitor Values during Immunosuppressive Therapy.

Acquired factor V inhibitor (AFVI) results from the formation of autoantibodies to coagulation factor V (FV), and the clinical phenotype can range from asymptomatic laboratory abnormalities to life-threatening bleeds. We describe a 74-year-old man who developed AFVI along with a massive subcutaneous hematoma. He was initially treated with prednisolone (PSL), but AFVI recurred when the dose was reduced after a short period. We subsequently increased the PSL dose and added cyclophosphamide (CY), which resulted in a complete response. We then gradually tapered PSL and stopped CY, and the patient has since remained free of recurrent AFVI symptoms. We monitored FV activity, antigen concentrations, and inhibitor titers of this patient throughout the clinical course. The ratio of FV activity to antigen concentration was low at diagnosis and gradually increased along with the patient's improvement. This ratio might be a useful parameter for evaluating the effects of immunosuppressive therapy in patients with AFVI.

Acquired Factor V Deficiency Associated with CFPM Administration.

BACKGROUND: Acquired factor V deficiency (AFVD) caused by Factor V (FV) inhibition is a rare event, characterized by prolonged prothrombin time and activated partial thromboplastin time. To date, various factors were reported as triggers for developing FV inhibitor. Clinical symptoms range from asymptomatic to life-threatening bleeding. Case Report and Conclusions: Here, we report an 84-year-old Japanese male on hemodialysis due to renal failure who developed subcutaneous hemorrhage after administration of cefepime (CFPM) to treat bacteremia. Deficient FV activity (< 1.0%) was identified and AFVD with FV inhibitor titer of 9 BU/mL was diagnosed. Although the patient had multiple risks for developing FV inhibitor, CFPM was thought to be the major culprit in this case. After the diagnosis, oral prednisolone (30 mg/day) was initiated, but the patient died of respiratory/cardiac failure, unrelated to AFVD.

A very potent factor V inhibitor interferes with the levels of all coagulation factors and causes a fatal hemorrhagic syndrome.

We report a very high factor V inhibitor affecting the measurement of all coagulation factors besides fibrinogen, all these factors being dramatically decreased. This inhibitor could be linked to antibiotic use. The patient died of massive hemorrhage before a plasma exchange could be initiated.

[Acquired blood coagulation factor â ¤ deficiency in a patient with severe burn].

In March 2017, a severely burned male patient aged 36 years with hypovolemic shock was admitted to our hospital. The patient received large quantities of antibiotics and blood products and repeated skin graft after admission, and then he suffered wound errhysis and throat congestion. The patient was healthy before without family history of bleeding or thrombosis disease. Laboratory tests showed that prothrombin time and activated partial coagulation time were remarkably prolonged, blood coagulation factor Ⅴ activity was extremely low, and the result of qualitative test of coagulation factor inhibitor was positive. Acquired blood coagulation factor Ⅴ deficiency was diagnosed. After application of dexamethasone (5 mg, twice per day) and infusion of fresh frozen plasma, blood coagulation indicators of patients recovered in 4 days, the result of qualitative test of coagulation factor inhibitor was negative, and bleeding symptoms were improved.

Mud in the blood: Novel potent anticoagulant coagulotoxicity in the venoms of the Australian elapid snake genus Denisonia (mud adders) and relative antivenom efficacy.

Due to their potent coagulotoxicity, Australian elapid venoms are unique relative to non-Australian members of the Elapidae snake family. The majority of Australian elapids possess potent procoagulant venom, while only a few species have been identified as possessing anticoagulant venoms. The majority of research to-date has concentrated on large species with range distributions overlapping major city centres, such as brown snakes (Pseudonaja spp.) and taipans (Oxyuranus spp.). We investigated the venom from the poorly studied genus Denisonia and documented anticoagulant activities that were differentially potent on amphibian, avian, and human plasmas. Both species were potently anticoagulant upon amphibian plasma, consistent with these snakes preying upon frogs as their primary food source. While D. devisi was only relatively weakly active on avian and human plasma, D. maculata was potently anticoagulant to amphibian, avian, and human plasma. The mechanism of anticoagulant action was determined to be the inhibition of prothrombin activation by Factor Xa by blocking the formation of the prothrombinase complex. Fractionation of D. maculata venom followed by MS sequencing revealed that the toxins responsible were Group I phospholipase A2. As no antivenom is produced for this species or its near relatives, we examined the ability of Seqirus Australian snake polyvalent antivenom to neutralise the anticoagulant effects, with this antivenom shown to be effective. These results contribute to the body of knowledge regarding adaptive evolution of venom, revealing a unique taxon-specific anticoagulant effect for D. devisi venom. These results also reveal the potential effects and mechanisms behind envenomation by the potently acting D. maculata venom on human plasma, while the discovery of the efficacy of an available antivenom provides information crucial to the design of snakebite management strategies.

A discrepancy between prothrombin time and Normotest (Hepaplastintest) results is useful for diagnosis of acquired factor V inhibitors.

Acquired coagulation factor inhibitors are rare. Among them, coagulation factor V (FV) inhibitor is particularly uncommon and presents with variable clinical manifestations. Certain acquired FV inhibitor patients have only mild bleeding or, in select cases, no symptoms at all, leading to spontaneous recovery. Others have life-threatening bleeding that requires medical attention. Thus, a prompt decision regarding diagnosis and clinical intervention is crucial for such patients. In five acquired FV inhibitor cases treated in our facility, each patient had a malignancy as an underlying disease and all unexpectedly showed prolongation of both prothrombin time (PT) and activated partial thromboplastin time (APTT). They all also displayed a discrepancy between PT and Normotest (Hepaplastintest, HPT) results. All but one patient experienced no bleeding at the time of diagnosis and achieved spontaneous recovery in 1-3 weeks. The patient with bleeding symptoms received plasma exchanges and a platelet transfusion. Useful markers in diagnosing the presence of an acquired FV inhibitor were a sudden prolongation of PT and APTT, and a discrepancy between the PT/APTT and HPT assays. Spontaneous recovery can be expected for patients with only minor bleeding.

High Titer of Acquired Factor V Inhibitor Presenting with a Pseudo-deficiency of Multiple Coagulation Factors.

Acquired coagulation factor inhibitor is a rare coagulation disorder. We herein report a patient with acquired factor V inhibitor showing a decrease in multiple coagulation factor activities. A high titer of factor V inhibitor presumably led to a marked inhibition of factor V activity in the specific factor-deficient plasma used in coagulation factor activity assays based on either an activated partial thromboplastin time (APTT) or prothrombin time (PT) clotting assay, resulting in false low values of the coagulation activity. We re-examined the coagulation factor activity using several dilutions of the patient's plasma and confirmed that the high factor V inhibitor titer had caused an apparent decrease in multiple coagulation factor activities.

Successful Outcome of Severe Intra-cerebral Bleeding Associated with Acquired Factor V Inhibition: Utilization of Multiple Therapeutic Agents.

BACKGROUND: Acquired coagulation factor inhibitors are antibodies that either inhibit activity or increase the clearance of a clotting factor and lead to an increased risk of bleeding. Most of the time, the disorder is attributed to factor VIII inhibition (acquired haemophilia A); however, other coagulation factors could also be implicated. CASE REPORT: Herein, we report an interesting case of a patient who underwent coronary artery bypass grafting and received antibiotic treatment after surgery with third generation cephalosporin. A month later, he presented with extreme bleeding diathesis and cerebral haemorrhage. Following a thorough clinical and laboratory investigation, an acquired factor V inhibitor was diagnosed. The patient received treatment with corticosteroids, intravenous immunoglobulins, anti-CD20 monoclonal antibodies (rituximab), cyclophosphamide and recombinant factor VIIa. Finally, despite the poor initial prognosis, the patient managed to achieve a full recovery. CONCLUSION: As there are no clear guidelines on acquired coagulation inhibitor treatment, reports of such cases could offer insight for future therapy choices. The case was unique because the treatment regimen included a combination of multiple therapeutic agents including rituximab.

Factor V Inhibitors: A Diagnostic and Therapeutic Challenge.

Historically, inhibitors to coagulation factor V (FV) most often have developed in patients treated with bovine thrombin, a topical hemostatic agent used during surgical procedures. With the advent of newer hemostatic agents, and the concurrent diminished use of bovine thrombin, the incidence of FV inhibitors has fallen. Nevertheless, FV inhibitors are occasionally seen on an idiopathic basis as well as in association with medications, malignancies, autoimmune disorders, pregnancy, and infections. Factor V inhibitors may present with life-threatening bleeding or thrombosis, or they may be discovered incidentally as a coagulation screening test abnormality. Management of patients with FV inhibitors is challenging and consists of control of bleeding and eradication of the inhibitor. In this short overview we review the role of platelet and plasma FV in hemostasis and discuss the unique characteristics, clinical features, diagnosis, treatment, and prognosis associated with FV inhibitors.