Immunomodulatory potential of natural killer T (NKT) activation by NKTT320 in Mauritian-origin cynomolgus macaques.

Invariant natural killer T-lymphocytes (iNKT) are unique immunomodulatory innate T cells with an invariant TCRα recognizing glycolipids presented on MHC class-I-like CD1d molecules. Activated iNKT rapidly secrete pro-and anti-inflammatory cytokines, potentiate immunity, and modulate inflammation. Here, we report the effects of iNKT activation in Mauritian-origin cynomolgus macaques by a humanized monoclonal antibody, NKTT320, that binds to the invariant region of the iNKT TCR.

Combination of NKT14m and Low Dose IL-12 Promotes Invariant Natural Killer T Cell IFN-γ Production and Tumor Control.

Invariant natural killer T (iNKT) cells are innate-like T lymphocytes characterized by the expression of an invariant T cell receptor (iTCR) that recognizes glycolipid antigens presented by the MHC I-like CD1d molecule. Following antigenic stimulation, iNKT cells rapidly produce large amounts of cytokines that can trans-activate dendritic cells (DC) and promote the anti-tumor functions of cytotoxic lymphocytes, such as natural killer (NK) and CD8 T cells. Additionally, iNKT cells can mediate robust and direct cytotoxicity against CD1d tumor targets.

Cancer Immunotherapeutic Potential of NKTT320, a Novel, Invariant, Natural Killer T Cell-Activating, Humanized Monoclonal Antibody.

Invariant natural killer T cells (iNKTs) directly kill tumor cells and trans-activate the anti-tumor functions of dendritic cells (DC), natural killer (NK) cells, and T and B cells. As such, iNKTs serve as a powerful tool for use in cell-based cancer immunotherapy. iNKT cell activation commonly requires engagement of the invariant T cell receptor (iTCR) by CD1d presenting glycolipid antigens.

The novel agonistic iNKT-cell antibody NKT14m induces a therapeutic antitumor response against B-cell lymphoma.

Invariant natural killer T (iNKT) cells are a small population of T lymphocytes that expresses an invariant T cell receptor with a unique specificity for glycolipid antigens. Their activation using the glycolipid α-galactosylceramide (α-GalCer) triggers innate and adaptive immune responses. The use of α-GalCer in preclinical models as a single antitumor treatment showed moderate effect, but its efficacy in cancer patients was less effective.

The role of iNKT cells on the phenotypes of allergic airways in a mouse model.

iNKT cells and mast cells have both been implicated in the syndrome of allergic asthma through their activation-induced release of Th2 type cytokines and secretion of histamine and other mediators, respectively, which can promote airways hyperresponsiveness (AHR) to agents such as methacholine. However, a mechanistic link between iNKT cells and mast cell recruitment or activation has never been explored. Our objective was to determine whether iNKT cells are necessary for the recruitment of mast cells and if iNKT cells can influence the acute allergen induced bronchoconstriction (AIB) caused by mast cell mediator release.

NNKTT120, an anti-iNKT cell monoclonal antibody, produces rapid and sustained iNKT cell depletion in adults with sickle cell disease.

Unlabelled: Invariant NKT (iNKT) cells can be activated to stimulate a broad inflammatory response. In murine models of sickle cell disease (SCD), interruption of iNKT cell activity prevents tissue injury from vaso-occlusion. NKTT120 is an anti-iNKT cell monoclonal antibody that has the potential to rapidly and specifically deplete iNKT cells and, potentially, prevent vaso-occlusion.

Invariant Natural Killer T Cells Are Pathogenic in the HLA-DR4-Transgenic Humanized Mouse Model of Toxic Shock Syndrome and Can Be Targeted to Reduce Morbidity.

During toxic shock syndrome (TSS), bacterial superantigens trigger a polyclonal T -cell response leading to a potentially catastrophic "cytokine storm". Whether innate-like invariant natural killer T (iNKT) cells, with remarkable immunomodulatory properties, participate in TSS is unclear. Using genetic and cell depletion approaches, we generated iNKT cell-deficient, superantigen-sensitive HLA-DR4-transgenic (DR4tg) mice, which were compared with their iNKT-sufficient counterparts for responsiveness to staphylococcal enterotoxin B (SEB).

Mouse Invariant Monoclonal Antibody NKT14: A Novel Tool to Manipulate iNKT Cell Function In Vivo.

Invariant Natural Killer T (iNKT) cells are a T cell subset expressing an invariant T Cell Receptor (TCR) that recognizes glycolipid antigens rather than peptides. The cells have both innate-like rapid cytokine release, and adaptive-like thymic positive selection. iNKT cell activation has been implicated in the pathogenesis of allergic asthma and inflammatory diseases, while reduced iNKT cell activation promotes infectious disease, cancer and certain autoimmune diseases such as Type 1 diabetes (T1D).

P-selectin inhibition therapeutically promotes thrombus resolution and prevents vein wall fibrosis better than enoxaparin and an inhibitor to von Willebrand factor.

Objective: Aptamers are oligonucleotides targeting protein-protein interactions with pharmacokinetic profiles and activity reversal options. Although P-selectin and von Willebrand factor (vWF) have been implicated in the development of venous thrombosis (VT), no studies have directly compared aptamer efficacy with standard of care in VT. In this study, ARC5692, an anti-P-selectin aptamer, and ARC15105, an anti-vWF aptamer, were compared with low-molecular-weight heparin, enoxaparin, to test the efficacy of P-selectin or vWF inhibition in promoting thrombus resolution and preventing vein wall fibrosis, in a baboon model of VT.

Drug-drug interaction of the anti-TFPI aptamer BAX499 and factor VIII: studies of spatial dynamics of fibrin clot formation in hemophilia A.

Background: In recent years, a number of tissue factor pathway inhibitor (TFPI) antagonists have been developed to serve as bypassing agents to improve hemostasis in hemophilia A. Since TFPI antagonists and FVIII concentrates are procoagulants, their combined effect on spatial clot formation could be potentially pro-thrombotic.

Objective: To investigate the cooperative effect of TFPI inhibition and supplementation of FVIII in hemophilia A in a spatial, reaction-diffusion experiment in vitro.

A humanized monoclonal antibody specific for invariant Natural Killer T (iNKT) cells for in vivo depletion.

Invariant Natural Killer T (iNKT) cells are a subset of T cells recognizing glycolipid antigens presented by CD1d. Human iNKT cells express a conserved T cell receptor (TCR)-α chain (Vα24-Jα18) paired with a specific beta chain, Vβ11. The cells are both innate-like, with rapid cytokine release, and adaptive-like, including thymic positive selection.

ARC15105 is a potent antagonist of von Willebrand factor mediated platelet activation and adhesion.

Objective: We investigated the stability, pharmacokinetic, and pharmacodynamic profile of the 2(nd) generation anti-von Willeband factor aptamer ARC15105.

Methods And Results: Platelet plug formation was measured by collagen/adenosine diphosphate-induced closure time with the platelet function analyzer-100 and platelet aggregation by multiple electrode aggregometry. Platelet adhesion was measured on denuded porcine aortas and in a flow chamber.

Recent advances in the development of coagulation factors and procoagulants for the treatment of hemophilia.

Hemophilia is a family of rare bleeding disorders. The two primary types, hemophilia A and hemophilia B, are caused by recessive X-chromosome linked mutations that result in deficiency of coagulation factor VIII (FVIII) or factor IX (FIX), respectively. Clinically, hemophilia is manifested by spontaneous bleeding, particularly into the joints (haemarthrosis) and soft tissue, and excessive bleeding following trauma or surgery.

Aptamer ARC19499 mediates a procoagulant hemostatic effect by inhibiting tissue factor pathway inhibitor.

Hemophilia A and B are caused by deficiencies in coagulation factor VIII (FVIII) and factor IX, respectively, resulting in deficient blood coagulation via the intrinsic pathway. The extrinsic coagulation pathway, mediated by factor VIIa and tissue factor (TF), remains intact but is negatively regulated by tissue factor pathway inhibitor (TFPI), which inhibits both factor VIIa and its product, factor Xa. This inhibition limits clot initiation via the extrinsic pathway, whereas factor deficiency in hemophilia limits clot propagation via the intrinsic pathway.

An anti-von Willebrand factor aptamer reduces platelet adhesion among patients receiving aspirin and clopidogrel in an ex vivo shear-induced arterial thrombosis.

The von Willebrand factor (vWF) aptamer, ARC1779 that blocks the binding of vWF A1-domain to platelet glycoprotein 1b (GPIb) at high shear, may deliver a site-specific antithrombotic effect. We investigated the efficiency of ARC1779 on platelet function in patients with coronary artery disease (CAD) on double antiplatelet therapy. Blood from patients taking aspirin and clopidogrel and from normal volunteers was treated ex vivo with ARC1779 or abciximab, either prior to perfusion (pretherapy) or 10 minutes following the initiation of perfusion (posttherapy) on damaged arteries.

Inhibition of cell adhesion by anti-P-selectin aptamer: a new potential therapeutic agent for sickle cell disease.

Adhesive interactions between circulating sickle red blood cells (RBCs), leukocytes, and endothelial cells are major pathophysiologic events in sickle cell disease (SCD). To develop new therapeutics that efficiently inhibit adhesive interactions, we generated an anti-P-selectin aptamer and examined its effects on cell adhesion using knockout-transgenic SCD model mice. Aptamers, single-stranded oligonucleotides that bind molecular targets with high affinity and specificity, are emerging as new therapeutics for cardiovascular and hematologic disorders.

Discovery of 2-[1-(4-chlorophenyl)cyclopropyl]-3-hydroxy-8-(trifluoromethyl)quinoline-4-carboxylic acid (PSI-421), a P-selectin inhibitor with improved pharmacokinetic properties and oral efficacy in models of vascular injury.

Previously, we reported the discovery of PSI-697 (1a), a C-2 benzyl substituted quinoline salicylic acid-based P-selectin inhibitor. It is active in a variety of animal models of cardiovascular disease. Compound 1a has also been shown to be well tolerated and safe in healthy volunteers at doses of up to 1200 mg in a phase 1 single ascending dose study.

The aptamer ARC1779 blocks von Willebrand factor-dependent platelet function in patients with thrombotic thrombocytopenic purpura ex vivo.

Background: In thrombotic thrombocytopenic purpura (TTP), ultralarge von Willebrand factor (VWF) multimers bind platelet (PLT) glycoprotein Ib and lead to the formation of disseminated fibrin-poor, VWF-rich PLT thrombi. The aptamer ARC1779 blocks binding of the VWF A1 domain to PLT glycoprotein Ib. We evaluated whether ARC1779 inhibits the excessive VWF activity and VWF-mediated PLT function in patients with TTP.

P-selectin/ PSGL-1 inhibitors versus enoxaparin in the resolution of venous thrombosis: a meta-analysis.

Background: P-selectin antagonism has been shown to decrease thrombogenesis and inflammation in animal models of deep venous thrombosis (DVT).

Objective: To determine the effectiveness of P-selectin inhibitors versus saline and enoxaparin in venous thrombus resolution in nonhuman primate models of venous thrombosis.

Methods: Studies reporting vein re-opening, inflammation expressed as Gadolinium enhancement and coagulation parameters were searched in the literature and pooled into a meta-analysis using an inverse variance with random effects.

A structural explanation for the antithrombotic activity of ARC1172, a DNA aptamer that binds von Willebrand factor domain A1.

ARC1172 is a 41-mer DNA aptamer selected to bind the A1 domain of von Willebrand factor (VWF). A derivative of ARC1172 with modifications to increase intravascular survival inhibits carotid artery thrombosis in a Cynomolgus macaque model and inhibits VWF-dependent platelet aggregation in humans, suggesting that such aptamers may be useful to prevent or treat thrombosis. In the crystal structure of a VWF A1-ARC1172 complex, the aptamer adopts a three-stem structure of mainly B-form DNA with three noncanonical base pairs and 9 unpaired residues, 6 of which are stabilized by base-base or base-deoxyribose stacking interactions.

The aptamer ARC1779 is a potent and specific inhibitor of von Willebrand Factor mediated ex vivo platelet function in acute myocardial infarction.

ARC1779 is an aptamer, which blocks binding of the von Willebrand Factor (VWF) A1 domain to platelet GPIb receptors. VWF is increased in the elderly an in the setting of acute myocardial infarction (AMI), as reflected by increased shear-dependent platelet function. We hypothesized that ARC1779 concentration-dependently inhibits ex vivo platelet function, and that this concentration effect relationship may be shifted in patients with AMI.

Dose-dependent thrombus resolution due to oral plaminogen activator inhibitor (PAI)-1 inhibition with tiplaxtinin in a rat stenosis model of venous thrombosis.

This study aimed to evaluate a small-molecule PAI-1 inhibitor (PAI-039; tiplaxtinin) in a rodent stenosis model of venous thrombosis in a two-phase experiment. Phase 1 determined the efficacy of tiplaxtinin against Lovenox (LOV), while phase 2 determined the dose-dependent efficacy. For both phases, drug treatment began 24 hours after surgically induced venous thrombosis and continued for four days.

Prophylactic P-selectin inhibition with PSI-421 promotes resolution of venous thrombosis without anticoagulation.

P-selectin inhibition has been evaluated as a therapeutic for prevention and treatment of venous thrombosis. In this study, a novel oral small-molecule inhibitor of P-selectin, PSI-421, was evaluated in a baboon model of stasis induced deep vein thrombosis (DVT). Experimental groups included i) primates receiving a single oral dose of 1 mg/kg PSI-421 two days prior and continued six days after thrombosis (n = 3); ii) primates receiving a single daily subcutaneous dose of 0.

Aptamers as candidate therapeutics for cardiovascular indications.

The first therapeutic aptamer was approved for human use in 2004, and a range of chemical substitutions that improve the drug-like properties of aptamers has recently been shown to increase the utility of this modality. Currently there are both anticoagulant and antithrombotic aptamers in the clinic, and additionally there are a number of earlier stage projects in which a variety of cardiovascular targets are inhibited by specific aptamers and for which a wide range of therapeutic applications has been suggested.