An anti-αVß3 antibody inhibits coronary artery atherosclerosis in diabetic pigs.

BACKGROUND AND AIMS: Diabetes is a major risk factor for the development of atherosclerosis. Hyperglycemia stimulates vascular smooth muscle cells (VSMC) to secrete ligands that bind to the αVß3 integrin, a receptor that regulates VSMC proliferation and migration. This study determined whether an antibody that had previously been shown to block αVß3 activation and to inhibit VSMC proliferation and migration in vitro, inhibited the development of atherosclerosis in diabetic pigs. METHODS: Twenty diabetic pigs were maintained on a high fat diet for 22 weeks. Ten received injections of anti-ß3 F(ab)2 and ten received control F(ab)2 for 18 weeks. RESULTS: The active antibody group showed reduction of atherosclerosis of 91 ± 9% in the left main, 71 ± 11%, in left anterior descending, 80 ± 10.2% in circumflex, and 76 ± 25% in right coronary artery, (p < 0.01 compared to lesions areas from corresponding control treated arteries). There were significant reductions in both cell number and extracellular matrix. Histologic analysis showed neointimal hyperplasia with macrophage infiltration, calcifications and cholesterol clefts. Antibody treatment significantly reduced number of macrophages contained within lesions, suggesting that this change contributed to the decrease in lesion cellularity. Analysis of the biochemical changes within the femoral arteries that received the active antibody showed a 46 ± 12% (p < 0.05) reduction in the tyrosine phosphorylation of the ß3 subunit of αVß3 and a 40 ± 14% (p < 0.05) reduction in MAP kinase activation. CONCLUSIONS: Blocking ligand binding to the αVß3 integrin inhibits its activation and attenuates increased VSMC proliferation that is induced by chronic hyperglycemia. These changes result in significant decreases in atherosclerotic lesion size in the coronary arteries. The results suggest that this approach may have efficacy in treating the proliferative phase of atherosclerosis in patients with diabetes.

Pharmacokinetics and pharmacodynamics of turoctocog alfa and N8-GP in haemophilia A dogs.

The objective of the present study was to evaluate the pharmacokinetic (PK) and pharmacodynamic (PD) profiles of the new recombinant FVIII compound turoctocog alfa and a Glyco-PEGylated FVIII derivative thereof (N8-GP) in Haemophilia A dogs. Six haemophilic dogs divided into two groups were included in the study. Each dog was administered a dose of 125 U kg(-1) , blood samples were collected at predetermined time points for both pharmacokinetic (FVIII measured by one-stage aPTT assay) and pharmacodynamic [whole blood clotting time (WBCT)] evaluations. After intravenous administration to haemophilic dogs, the plasma concentration at the first sampling point was comparable for turoctocog alfa and N8-GP, and the clearance was estimated to be 6.5 and 3.9 mL h(-1) kg(-1) for turoctocog alfa and N8-GP respectively. Both turoctocog alfa and N8-GP were able to reduce the WBCT time to normal levels (<20 min), however, the reduced clearance was reflected in the WBCT, which returned to baseline at a later time point for N8-GP as compared with dogs dosed with turoctocog alfa. The clearance was 40% reduced for N8-GP as compared with turoctocog alfa. Simulations of a multiple dosing regimen in dogs, suggest that to maintain WBCT <20 min N8-GP can be dosed at reduced intervals, e.g. with 4 days between doses, whereas turoctocog alfa will have to be dosed with 2½ day between doses. Data thereby supports N8-GP as an alternative to standard rFVIII replacement therapy, with a more convenient dosing regimen.

Improved kinetics of rIX-FP, a recombinant fusion protein linking factor IX with albumin, in cynomolgus monkeys and hemophilia B dogs.

BACKGROUND: Prophylaxis of hemophilia B, at present, requires multiple infusions of human factor (F)IX concentrates per week. A FIX molecule with a prolonged half-life has the potential to greatly improve the convenience of, and adherence to, prophylaxis. OBJECTIVES: The aim of our studies was to investigate the pharmacokinetic (PK) and pharmacodynamic (PD) profile of a recombinant fusion protein linking coagulation FIX with albumin (rIX-FP). METHODS: Cynomolgus monkeys and hemophilia B dogs received single intravenous doses of rIX-FP (50-500 IU kg(-1)). rIX-FP plasma levels were determined by an activity-based assay (dogs only) and anti-FIX ELISA methods. Additionally, activated partial thromboplastin time (APTT) was determined in hemophilia B dogs. Data were compared with a direct study comparator (recombinant FIX [rFIX]) or previously published data. RESULTS: The terminal half-life of rIX-FP was prolonged in both species compared with FIX reference data. In hemophilia B dogs, human FIX antigen levels remained above 0.05 IU mL(-1) more than three times longer after rIX-FP (7.3 days) compared with rFIX (2.3 days), whereas respective calculations based on activity levels confirmed the observed superior profile. Prolonged PDs of rIX-FP were demonstrated with APTT<60 s sustained around four times longer with rIX-FP (5.9 days) than rFIX (1.5 days). CONCLUSIONS: These studies indicate that the recombinant albumin fusion technology successfully improves the PK profile of FIX. Clinical studies will test whether the improved kinetics result in a significant half-life extension in patients with hemophilia B.

Pharmacokinetics and ex vivo whole blood clot formation of a new recombinant FVIII (N8) in haemophilia A dogs.

N8, a new recombinant factor VIII (rFVIII) compound developed for the treatment of haemophilia A, is produced in Chinese hamster ovary (CHO) cells and formulated without human- or animal-derived materials. The aim of the present study was to compare the pharmacokinetics (PK) and the procoagulant effect, measured by ex vivo whole blood clot formation, of N8 and a commercial rFVIII in a cross-over study in haemophilia A dogs. N8 and Advate® (100 IU kg⁻¹) were administered intravenously to three haemophilia A dogs. Blood was sampled between 0 and 120 h postdose and FVIII:C analysed. PK parameters maximum plasma concentration, area under the curve, half-life (t(½)), clearance, mean residence time (MRT) and volume of distribution and incremental recovery were calculated. Whole blood clotting time (WBCT) and thromboelastography (TEG®) were used to determine the haemostatic potential. No adverse reactions were observed with N8 or Advate ®. N8 and Advate® exhibited similar PK parameters, with t(½) 7.7-11 h and MRT 11-14 h. Both rFVIII compounds corrected the prolonged WBCT (> 48 min) to the range of normal dogs (8-12 min), i.e. N8 to 7.5-10.5 min and Advate® to 7.5-11.5 min. N8 and Advate® also normalized the whole blood clot formation according to TEG®. The native whole blood clotting assays (WBCT, TEG®) appeared to be more sensitive to low concentrations of FVIII than assays in citrated plasma samples. In conclusion, comparison of N8 and Advate ® in haemophilia A dogs revealed similar safety, similar PK and similar effects in whole blood clot formation assays.

Prevention of spontaneous bleeding in dogs with haemophilia A and haemophilia B.

Dogs with haemophilia A or haemophilia B exhibit spontaneous bleeding comparable with the spontaneous bleeding phenotype that occurs in humans with severe haemophilia. The phenotypic and genotypic characteristics of haemophilic dogs have been well-described, and such dogs are suitable for testing prophylactic protein replacement therapy and gene transfer strategies. In dogs with haemophilia, long-term effects on spontaneous bleeding frequency (measured over years) can be used as an efficacy endpoint in such studies. Although complete correction of coagulopathy has not been achieved, published data show that prophylactic factor replacement therapy and gene transfer can markedly reduce the frequency of spontaneous bleeding in haemophilic dogs. Further studies are currently ongoing.

A phase II prospective open-label escalating dose trial of recombinant interleukin-11 in mild von Willebrand disease.

von Willebrand factor (VWF) is a multimeric glycoprotein that mediates platelet adhesion and is decreased in von Willebrand disease (VWD). 1-8 deamino-d-arginine vasopressin (DDAVP), the most common treatment for VWD, is limited by tachyphylaxis and inconvenience, and in 20% of the patients, unresponsiveness. Recombinant human interleukin-11 (rhIL-11), a gp-130 signalling cytokine with haematopoietic and anti-inflammatory activity, increases VWF antigen and its activity in heterozygous VWF(+/-) mice and dogs. To determine the biological efficacy and safety of rhIL-11 in non-bleeding human subjects with mild VWD, we conducted a phase II prospective open-label trial of rhIL-11 at 10, 25 and 50 mug kg(-1) subcutaneously (s.c.), given daily for 7 days in nine subjects with mild VWD. VWF and factor VIII (FVIII) levels increased gradually and progressively after s.c. rhIL-11, which was sustained through 7 days of dosing to 1.5- to 3-fold over baseline. Following intravenous DDAVP, 0.3 mug kg(-1), on day 7 there was a further boost in VWF and FVIII levels, suggesting that the mechanism of rhIL-11 differs from that of DDAVP. Platelet VWF mRNA expression measured by quantitative PCR increased from two- to eightfold over baseline, suggesting that the mechanism of rhIL-11 effect may be upregulation of VWF mRNA. VWF and FVIII levels returned to baseline by day 14. rhIL-11 was well tolerated with less than grade-1 hypertension, hypokalaemia and fluid retention. Recombinant IL-11 increases VWF levels in humans with mild VWD, justifying future clinical trials to determine its potential in preventing or reducing bleeding in this patient population.

Intracellular function in rehydrated lyophilized platelets.

This study aimed to evaluate the effect of cross-linking and lyophilization on intracellular signalling processes in rehydrated, lyophilized (RL) platelets, which are under development as a platelet substitute for transfusion. Exposure of RL platelets to thrombin resulted in enhanced phosphorylation of several proteins, including 18 kDa and 42 kDa kinase substrates that were shown to be the substrates of myosin light chain and protein kinase C respectively. Cross-linking and lyophilization depleted the platelets of free cytoplasmic ADP and ATP, but had less effect on protein-bound nucleotides. The surface membrane of RL platelets was found to be permeable to poly dT probes less than approximately 3 kDa in size; larger nucleotide probes and proteins did not penetrate the surface membrane. Taken together, our results indicate that RL platelets retain some of the haemostatic stimulus-response functions of fresh platelets and are capable of feedback amplification in coagulation.

Chemotactic peptide-induced changes of intermediate filament organization in neutrophils during granule secretion: role of cyclic guanosine monophosphate.

In neutrophils activated to secrete with formyl-methionyl-leucyl-phenylalanine, intermediate filaments are phosphorylated transiently by cyclic guanosine monophosphate (cGMP)-dependent protein kinase (G-kinase). cGMP regulation of vimentin organization was investigated. During granule secretion, cGMP levels were elevated and intermediate filaments were transiently assembled at the pericortex to areas devoid of granules and microfilaments. Microtubule and microfilament inhibitors affected intermediate filament organization, granule secretion, and cGMP levels. Cytochalasin D and nocodazole caused intermediate filaments to assemble at the nucleus, rather than at the pericortex. cGMP levels were elevated in neutrophils by both inhibitors; however, with cytochalasin D, cGMP was elevated earlier and granule secretion was excessive. Nocodazole did not affect normal cGMP elevations, but specific granule secretion was delayed. LY83583, a guanylyl cyclase antagonist, inhibited granule secretion and intermediate filament organization, but not microtubule or microfilament organization. Intermediate filament assembly at the pericortex and secretion were partially restored by 8-bromo-cGMP in LY83583-treated neutrophils, suggesting that cGMP regulates these functions. G-kinase directly induced intermediate filament assembly in situ, and protein phosphatase 1 disassembled filaments. However, in intact cells stimulated with formyl-methionyl-leucyl-phenylalanine, intermediate filament assembly is focal and transient, suggesting that vimentin phosphorylation is compartmentalized. We propose that, in addition to changes in microfilament and microtubule organization, granule secretion is also accompanied by changes in intermediate filament organization, and that cGMP regulates vimentin filament organization via activation of G-kinase.

Compartmentalization of PDE-4 and cAMP-dependent protein kinase in neutrophils and macrophages during phagocytosis.

The compartmentalization of cAMP in human neutrophils during phagocytosis of serum-opsonized zymosan suggests that cAMP is an important second messenger for regulating phagocytosis. Type 4 cAMP-specific phosphodiesterase (PDE-4), cAMP-dependent protein kinase (PKA), and adenylate cyclase are the principal effector molecules for cAMP regulation in phagocytes. Immunofluorescence microscopy demonstrated that PDE-4 isoforms (HSPDE-4A, HSPDE-4B, HSPDE-4D) were targeted to the forming phagosome in neutrophils, and were colocalized with the catalytic subunit of PKA and degranulated myeloperoxidase. Phagocytosis and accumulation of PDE-4 and PKA near adherent zymosan were inhibited by elevating cAMP levels with forskolin or rolipram. cAMP, PDE-4, and PKA were localized at sites of zymosan adherence in cells treated with cytochalasin D to inhibit phagosome formation, suggesting that zymosan engagement to Fc/CR3 receptors triggers cAMP elevations at sites of phagocytosis. HSPDE-4A, HSPDE-4B, HSPDE-4D, and PKA also were localized at the forming phagosome in monocyte-derived macrophages, and the lysosomal marker CD63 demonstrated the absence of PDE-4 around internalized phagolysosomes. These results suggest that cAMP levels are focally regulated by PDE-4 at the nascent phagosome, and that PKA may phosphorylate proteins associated with pseudopodia formation and phagosome internalization.