Matthew D. Linnik

Anti-Inflammatory Effects of LJP 1586 [Z-3-Fluoro-2-(4-methoxybenzyl)allylamine Hydrochloride], an Amine-Based Inhibitor of Semicarbazide-Sensitive Amine Oxidase Activity

Semicarbazide-sensitive amine oxidase (SSAO, amine oxidase, copper-containing 3, and vascular adhesion protein-1) is a copper-containing enzyme that catalyzes the oxidative deamination of primary amines to an aldehyde, ammonia, and hydrogen peroxide. SSAO is also involved in leukocyte migration to sites of inflammation, and the enzymatic activity of SSAO is essential to this role. Thus, inhibition of SSAO enzyme activity represents a target for the development of small molecule anti-inflammatory compounds. Here, we have characterized the novel SSAO inhibitor, Z-3-fluoro-2-(4-methoxybenzyl)allylamine hydrochloride (LJP 1586), and assessed its anti-inflammatory activity. LJP 1586 is a potent inhibitor of rodent and human SSAO activity, with IC50 values between 4 and 43 nM. The selectivity of LJP 1586 was confirmed with a broad panel of receptors and enzymes that included the monoamine oxidases A and B. Oral administration of LJP 1586 resulted in complete inhibition of rat lung SSAO, with an ED50 between 0.1 and 1 mg/kg, and a pharmacodynamic half-life of greater than 24 h. In a mouse model of inflammatory leukocyte trafficking oral dosing with LJP 1586 resulted in significant dose-dependent inhibition of neutrophil accumulation, with an effect comparable to that of anti-leukocyte function-associated antigen-1 antibody. In a rat model of LPS-induced lung inflammation, administration of 10 mg/kg LJP 1586 resulted in a 55% significant reduction in transmigrated cells recovered by bronchoalveolar lavage. The results demonstrate that a selective, orally active small molecule inhibitor of SSAO is an effective anti-inflammatory compound in vivo and provide further support for SSAO as a therapeutic anti-inflammatory target.

Domain V of β2-Glycoprotein I Binds Factor XI/XIa and Is Cleaved at Lys317-Thr318

The fifth domain (DV) of β2-glycoprotein I (β2GPI) is important for binding a number of ligands including phospholipids and factor XI (FXI). β2GPI is proteolytically cleaved in DV by plasmin but not by thrombin, VIIa, tissue plasminogen activator, or uPA. Following proteolytic cleavage of DV by plasmin, β2GPI retains binding to FXI but not to phospholipids. Native β2GPI, but not cleaved β2GPI, inhibits activation of FXI by thrombin and factor XIIa, attenuating a positive feedback mechanism for additional thrombin generation. In this report, we have defined the FXI/FXIa binding site on β2GPI using site-directed mutagenesis. We show that the positively charged residues Lys284, Lys286, and Lys287 in DV are essential for the interaction of β2GPI with FXI/FXIa. We also demonstrate that FXIa proteolytically cleaves β2GPI at Lys317-Thr318 in DV. Thus, FXIa cleavage of β2GPI in vivo during thrombus formation may accelerate FXI activation by decreasing the inhibitory effect of β2GPI.

In vivo characterization of bioconjugate B cell toleragens with specificity for autoantibodies in antiphospholipid syndrome.

This study investigated the use of well-defined bioconjugate molecules to suppress antigen-specific B cell responses to domain I (DI) of human beta(2)-glycoprotein I (beta(2)GPI) in rats. DI is the dominant target of pathogenic autoimmune antibodies in patients with antiphospholipid syndrome (APS), a disease characterized by antibody-mediated thromboembolic events. Rats primed with DI conjugated to keyhole limpet hemocyanin (DI-KLH) were rendered tolerant to subsequent antigen challenge by treatment with multivalent conjugates of DI. Antibodies to DI were suppressed 89-96% with intravenous doses of 500 micro g, and reductions were paralleled by decreases in splenic antigen-specific antibody-forming cells (AFC). Suppression was achieved with a variety of conjugates having two to four copies of DI and circulating half-lives of 2.6-8.7 h. Antibodies to KLH were not suppressed, indicating the specificity of the approach. These results establish the basis for further development of therapeutic B cell toleragens to suppress pathogenic antibodies in APS and other autoimmune diseases.

Therapeutic Potential of Toleragens in the Management of Antiphospholipid Syndrome

Autoantibodies to β2-glycoprotein I (β2GPI) are believed to be the primary cause of coagulation abnormalities in patients with antiphospholipid syndrome (APS). Clinical features include a range of life-threatening thrombotic events and microangiopathies affecting multiple organ systems. Current standard of care relies on long-term, high-intensity anticoagulation and is associated with a high risk for serious bleeding events. The relation between autoantibodies and the pathophysiology of APS is not clearly understood, but numerous in vitro studies have characterized the effects of antiphospholipid autoantibodies on various components of the coagulation cascade, including tissue factor and the protein C pathway. The fine specificity of autoantibodies to β2GPI is a subject of considerable debate; however, a body of evidence may offer resolution by integrating concepts of antibody affinity and assay sensitivity with carefully designed molecular studies. An investigational new therapy for APS is based on the approach that pathogenic antibodies may be reduced via depletion of circulating autoantibodies and induction of immune tolerance at the B-cell level. Preliminary results from a phase I/II clinical trial with LJP 1082, a B-cell toleragen, indicate the drug was well tolerated and may warrant further development for reduction of thrombotic events in patients with APS.

Pharmacokinetics of High-Dose Abetimus Sodium in Normal Subjects With Specific Assessment of Effect on Coagulation

Abetimus sodium is an oligonucleotide‐based investigational drug designed to treat patients with lupus nephritis by specifically reducing anti‐double‐stranded DNA antibody levels. The safety and pharmacokinetics of abetimus were evaluated in 24 healthy volunteers at intravenous doses of 600 mg, 1200 mg, and 2400 mg. The mean half‐life ranged from 0.8 to 1.5 hours. Maximum exposure assessed by maximum observed plasma concentration was dose proportional. Total exposure assessed by area under the plasma concentration—time curve was dose proportional between 1200‐mg and 2400‐mg doses and greater than proportionate between the 600‐mg and 1200‐mg doses. Abetimus was well tolerated in all dose groups, with adverse events observed in 33.3% (2/6) of placebo subjects and 16.7% (3/18) subjects receiving abetimus. No clinically significant effects were observed on laboratory values, vital signs, or electrocardiogram, with the exception of a transient, dose‐dependent, prolongation in activated partial thromboplastin time. In vitro coagulation studies suggested that the effect on activated partial thromboplastin time was attributable to a nonspecific interaction rather than specific factor depletion. Exposure to abetimus at intravenous doses of 600 mg, 1200 mg, and 2400 mg was well tolerated. Total exposure assessed by area under the plasma concentration—time curve was greater than dose proportional across the dose range of 600 mg to 2400 mg.