Characterization of canine coagulation factor VII and its complex formation with tissue factor: canine-human cross-species compatibility

Procoagulant Activity of Umbilical Cord-Derived Mesenchymal Stromal Cells' Extracellular Vesicles (MSC-EVs)

Many cell types, including cancer cells, release tissue factor (TF)-exposing extracellular vesicles (EVs). It is unknown whether MSC-EVs pose a thromboembolism risk due to TF expression. Knowing that MSCs express TF and are procoagulant, we hypothesize that MSC-EVs also might. Here, we examined the expression of TF and the procoagulant activity of MSC-EVs and the impact of EV isolation methods and cell culture expansion on EV yield, characterization, and potential risk using a design of experiments methodology. MSC-EVs were found to express TF and have procoagulant activity. Thus, when MSC-derived EVs are employed as a therapeutic agent, one might consider TF, procoagulant activity, and thromboembolism risk and take steps to prevent them.

Animal Safety, Toxicology, and Pharmacokinetic Studies According to the ICH S9 Guideline for a Novel Fusion Protein tTF-NGR Targeting Procoagulatory Activity into Tumor Vasculature: Are Results Predictive for Humans?

Simple Summary

Non-clinical safety, toxicology, and pharmacokinetic studies according to ICH guidelines with a new fusion protein tTF-NGR consisting of human truncated tissue factor (TF) and a small targeting peptide are reported. Results are compared with those of a phase I clinical dose escalation trial with tTF-NGR in cancer patients. Most of the non-clinical results were not predictive for human tolerability. Thus, animal sparing alternative pathways for translation of such a bio-pharmaceutical compound from preclinical studies on efficacy and mode of action into the clinic are discussed.

Abstract

Background: CD-13 targeted tissue factor tTF-NGR is a fusion protein selectively inducing occlusion of tumor vasculature with resulting tumor infarction. Mechanistic and pharmacodynamic studies have shown broad anti-tumor therapeutic effects in xenograft models. Methods: After successful Good Manufacturing Practice (GMP) production and before translation into clinical phase I, ICH S9 (S6) guideline-conforming animal safety, toxicology, and pharmacokinetic (PK) studies were requested by the federal drug authority in accordance with European and US regulations. Results: These studies were performed in mice, rats, guinea pigs, and beagle dogs. Results of the recently completed clinical phase I trial in end-stage cancer patients showed only limited predictive value of these non-clinical studies for patient tolerability and safety in phase I. Conclusions: Although this experience cannot be generalized, alternative pathways with seamless clinical phase 0 microdosing—phase I dose escalation studies are endorsed for anticancer drug development and translation into the clinic.

Coagulation factor activity patterns of venom-induced consumption coagulopathy in naturally occurring tiger snake (Notechis scutatus) envenomed dogs treated with antivenom

BACKGROUND

Venom-induced consumption coagulopathy (VICC) from tiger snake (Notechis scutatus) envenomation results in a dose-dependent coagulopathy that is detectable on coagulometry. However, individual coagulation factor activities in dogs with tiger snake envenomation have not been determined. This study aimed to characterise VICC and the time course of recovery in tiger snake envenomed dogs and to investigate an association between tiger snake venom (TSV) concentrations and factor activity.

METHODS

This was a prospective, observational, cohort study. The study cohort was 11 dogs of any age, breed, sex, body weight >10 kg, confirmed serum TSV on ELISA and treated with antivenom. Blood was collected at enrolment before antivenom administration, then at 3, 12 and 24 h after antivenom administration. Tiger snake venom concentrations were detected with a sandwich ELISA. Fibrinogen was measured using a modified Clauss method, and coagulation factors (F) II, V, VII, VIII and X were measured with factor-deficient human plasma using a modified prothrombin (PT) and activated partial thromboplastin (aPTT) method. Linear mixed models, with multiple imputations of censored observations, were used to determine the effect of time and TSV concentration on the coagulation times and factor activity. This cohort was compared to 20 healthy controls.

RESULTS

At enrolment, there were severe deficiencies in fibrinogen, FV and FVIII, with predicted recovery by 10.86, 11.75 and 13.14 h after antivenom, respectively. There were modest deficiencies in FX and FII, with predicted recovery by 20.57 and 32.49 h after antivenom, respectively. No changes were detected in FVII. Prothrombin time and aPTT were markedly prolonged with predicted recovery of aPTT by 12.58 h. Higher serum TSV concentrations were associated with greater deficiencies in FII, FV and FVIII, and greater prolongations in coagulation times. The median (range) serum TSV concentration was 57 (6-2295) ng/mL.

CONCLUSIONS

In tiger snake envenomed dogs, we detected a profound, TSV-concentration-related consumption of select coagulation factors, that rapidly recovered toward normal. These findings allowed further insight into tiger snake VICC in dogs.

Evaluation of procoagulant tissue factor expression in canine hemangiosarcoma cell lines

OBJECTIVE To evaluate expression of procoagulant tissue factor (TF) by canine hemangiosarcoma cells in vitro. SAMPLES 4 canine hemangiosarcoma cell lines (SB-HSA [mouse-passaged cutaneous tumor], Emma [primary metastatic brain tumor], and Frog and Dal-1 [primary splenic tumors]) and 1 nonneoplastic canine endothelial cell line (CnAoEC). PROCEDURES TF mRNA and TF antigen expression were evaluated by quantitative real-time PCR assay and flow cytometry, respectively. Thrombin generation was measured in canine plasma and in coagulation factor-replete or specific coagulation factor-deficient human plasma by calibrated automated thrombography. Corn trypsin inhibitor and annexin V were used to examine contributions of contact activation and membrane-bound phosphatidylserine, respectively, to thrombin generation. RESULTS All cell lines expressed TF mRNA and antigen, with significantly greater expression of both products in SB-HSA and Emma cells than in CnAoEC. A greater percentage of SB-HSA cells expressed TF antigen, compared with other hemangiosarcoma cell lines. All hemangiosarcoma cell lines generated significantly more thrombin than did CnAoEC in canine or factor-replete human plasma. Thrombin generation induced by SB-HSA cells was significantly lower in factor VII-deficient plasma than in factor-replete plasma and was abolished in factor X-deficient plasma; residual thrombin generation in factor VII-deficient plasma was abolished by incubation of cells with annexin V. Thrombin generation by SB-HSA cells was unaffected by the addition of corn trypsin inhibitor. CONCLUSIONS AND CLINICAL RELEVANCE Hemangiosarcoma cell lines expressed procoagulant TF in vitro. Further research is needed to determine whether TF can be used as a biomarker for hemostatic dysfunction in dogs with hemangiosarcoma.

Canine models of inherited bleeding disorders in the development of coagulation assays, novel protein replacement and gene therapies

Animal models of inherited bleeding disorders are important for understanding disease pathophysiology and are required for preclinical assessment of safety prior to testing of novel therapeutics in human and veterinary medicine. Experiments in these animals represent important translational research aimed at developing safer and better treatments, such as plasma-derived and recombinant protein replacement therapies, gene therapies and immune tolerance protocols for antidrug inhibitory antibodies. Ideally, testing is done in animals with the analogous human disease to provide essential safety information, estimates of the correct starting dose and dose response (pharmacokinetics) and measures of efficacy (pharmacodynamics) that guide the design of human trials. For nearly seven decades, canine models of hemophilia, von Willebrand disease and other inherited bleeding disorders have not only informed our understanding of the natural history and pathophysiology of these disorders but also guided the development of novel therapeutics for use in humans and dogs. This has been especially important for the development of gene therapy, in which unique toxicities such as insertional mutagenesis, germ line gene transfer and viral toxicities must be assessed. There are several issues regarding comparative medicine in these species that have a bearing on these studies, including immune reactions to xenoproteins, varied metabolism or clearance of wild-type and modified proteins, and unique tissue tropism of viral vectors. This review focuses on the results of studies that have been performed in dogs with inherited bleeding disorders that closely mirror the human condition to develop safe and effective protein and gene-based therapies that benefit both species.

Expression of tissue factor in canine mammary tumours and correlation with grade, stage and markers of haemostasis and inflammation

Tissue factor (TF) expression in human cancers has been associated with a procoagulant state and facilitation of metastasis. This study was conducted in order to evaluate if TF was expressed in canine mammary tumours. Forty epithelial mammary tumours from 28 dogs were included. TF expression of the tumours was evaluated by immunohistochemistry using a polyclonal antibody against recombinant canine TF. In addition, thromboelastography, haemostatic and inflammatory parameters were evaluated in the patients. TF was recognized in 44% of benign and 58% of malignant tumours. TF localized to the cytoplasmic membrane of neoplastic luminal epithelial cells and/or diffusely in the cytoplasm. No association was found between TF expression and stage or grade of disease. A significant association between TF expression and antithrombin and plasminogen was found, and extensive TF expression was seen in a lymph node metastasis classified as anaplastic mammary carcinoma from a dog with concomitant disseminated intravascular coagulation (DIC).

Immunomodulatory intervention with interferon-γ in Escherichia coli pyelonephritis

PURPOSE

We investigated the efficacy of recombinant human interferon-γ in experimental pyelonephritis due to Escherichia coli.

MATERIALS AND METHODS

Pyelonephritis was induced by intrapelvic inoculation of bacteria after ureteral ligation in 38 rabbits assigned to 1 of 3 groups, including group 1-16 controls, group 2-14 rabbits treated with intravenous recombinant human interferon-γ and group 3-8 rabbits treated with intravenous recombinant human interferon-γ plus amikacin. Bacterial counts, cytokines and malondialdehyde were measured in blood. Peripheral blood mononuclear cells were isolated to measure TNFα transcripts, cytokine stimulation and apoptosis. Survival was recorded, and the tissue bacterial load and myeloperoxidase activity were measured after sacrifice.

RESULTS

The mortality rate in groups 1, 2 and 3 was 66.7%, 25% and 12.5%, respectively. The circulating bacterial count and tissue bacterial load were less in group 2 than in group 1. Circulating malondialdehyde negatively correlated with the bacterial load of the spleen. Although the number of TNFα transcripts in circulating peripheral blood mononuclear cells did not differ, peripheral blood mononuclear cells isolated from group 2 at 48 hours produced much greater concentrations of tumor necrosis factor-α after stimulation with Pam3Cys. In parallel, the apoptosis rate of circulating monocytes was increased in group 2 at 48 hours. Lung myeloperoxidase activity at 24 hours, serving as indirect evidence of neutrophil infiltration, was decreased in group 2.

CONCLUSIONS

Recombinant human interferon-γ administration prolonged survival in rabbits with experimental E. coli urosepsis. Its action was probably related to increased bacterial phagocytosis after modulation of oxidant status and reversal of monocyte immunoparalysis.

Aortic thrombosis in dogs: presentation, therapy, and outcome in 26 cases

OBJECTIVES

The pathogenesis and presentation of aortic thrombosis (AT) in dogs is not well characterized and an effective antithrombotic therapy for AT in dogs has not been identified. Our goal is to report the clinical presentation and results of therapies in dogs with AT.

ANIMALS

Twenty-six client-owned dogs.

METHODS

Retrospective review of medical records of dogs diagnosed with AT between 2003 and 2010.

RESULTS

Twenty-six dogs had an apparent primary mural aortic thrombus. None had structural heart disease at diagnosis. Twenty dogs were ambulatory with varying degrees of pelvic limb dysfunction. Duration of ambulatory dysfunction was 7.8 weeks (range 1 day-52 weeks). A majority of dogs (58%) had no concurrent conditions at diagnosis. Fourteen dogs were treated with a standard warfarin protocol for a median period of 22.9 months (range 0.5-53 months). Ambulatory function improved in all dogs treated with warfarin. Time until clinical improvement was 13.9 days (range 2-49 days). Dogs treated with warfarin did not become non-ambulatory, die or undergo euthanasia related to AT, or have a known serious hemorrhagic event.

CONCLUSIONS

The pathogenesis of AT in dogs is distinct from that of aortic thromboembolism (ATE) in cats. Aortic thrombosis in dogs is more likely to involve local thrombosis in the distal aorta with embolization to the arteries of the pelvic limb resulting in chronic progressive ambulatory dysfunction. Chronic warfarin administration is well-tolerated and appears to be an effective short-term and long-term therapy for dogs with AT.

Pharmacokinetics, pharmacodynamics and safety of recombinant canine FVIIa in a study dosing one haemophilia A and one haemostatically normal dog

Recombinant human FVIIa (rhFVIIa) corrects the coagulopathy in hemophilia A and B as well as FVII deficiency. This is also the case in dogs until canine anti-human FVIIa antibodies develop (~2 weeks). Recombinant canine factor VIIa (rcFVIIa), successfully over-expressed by gene transfer in haemophilia dogs, has provided long-term haemostasis (>2 years). However, pharmacokinetics (PK), pharmacodynamics (PD) and safety of rcFVIIa after pharmacological administration have not been reported. We therefore wanted to explore the safety, PK and PD of rcFVIIa in dogs. A pilot study was set up to evaluate the safety as well as PK and PD of rcFVIIa after a single intravenous dose of 270 μg kg(-1) to one HA and one haemostatically normal dog and to directly compare rcFVIIa with rhFVIIa in these two dogs. Single doses of rcFVIIa and rhFVIIa were well tolerated. No adverse events were observed. Pharmacokinetic characteristics including half-life (FVIIa activity: 1.2-1.8 h; FVIIa antigen 2.8-3.7 h) and clearance were comparable for rcFVIIa and rhFVIIa. Kaolin-activated thromboelastography approached normal in the HA dog with the improvement being most pronounced after rcFVIIa. This study provided the first evidence that administering rcFVIIa intravenously is feasible, safe, well tolerated and efficacious in correcting the haemophilic coagulopathy in canine HA and that rcFVIIa exhibits pharmacokinetic characteristics comparable to rhFVIIa in haemophilic and haemostatically competent dogs. This strengthens the hypothesis that rcFVIIa can be administered to dogs to mimic the administration of rhFVIIa to humans.

Canine specific ELISA for coagulation factor VII

Canine coagulation factor VII (FVII) deficiency can be hereditary or acquired and may cause life threatening bleeding episodes if untreated. FVII procoagulant activity can be measured by FVII activity (FVII:C), but assays for measurement of canine specific FVII antigen (FVII:Ag) have not been available to date. In this study, a canine specific ELISA for measurement of FVII:Ag in plasma was developed and validated. The FVII:Ag ELISA correctly diagnosed homozygous and heterozygous hereditary FVII deficiency. Together with activity based assays, such as FVII:C, the FVII:Ag ELISA should be valuable in the diagnosis of hereditary canine FVII deficiency.