Optimization of Physicochemical Properties of Pyrrolidine GPR40 AgoPAMs Results in a Differentiated Profile with Improved Pharmacokinetics and Reduced Off-Target Activities

GPR40 AgoPAMs are highly effective antidiabetic agents that have a dual mechanism of action, stimulating both glucose-dependent insulin and GLP-1 secretion. The early lipophilic, aromatic pyrrolidine and dihydropyrazole GPR40 AgoPAMs from our laboratory were highly efficacious in lowering plasma glucose levels in rodents but possessed off-target activities and triggered rebound hyperglycemia in rats at high doses. A focus on increasing molecular complexity through saturation and chirality in combination with reducing polarity for the pyrrolidine AgoPAM chemotype resulted in the discovery of compound 46, which shows significantly reduced off-target activities as well as improved aqueous solubility, rapid absorption, and linear PK. In vivo, compound 46 significantly lowers plasma glucose levels in rats during an oral glucose challenge yet does not demonstrate the reactive hyperglycemia effect at high doses that was observed with earlier GPR40 AgoPAMs.

Synthesis and evaluation of azabicyclo[3.2.1]octane derivatives as potent mixed vasopressin antagonists

A series of biaryl amides containing an azabicyclooctane amine headpiece were synthesized and evaluated as mixed arginine vasopressin (AVP) receptor antagonists. Several analogues, including 8g, 12g, 13d, and 13g, were shown to have excellent V(1a)- and good V(2)-receptor binding affinities. Compound 13d was further profiled for drug-like properties and for an in vitro comparison with conivaptan, the program's mixed V(1a)/V(2)-receptor antagonist standard.

Effect of tiplaxtinin (PAI-039), an orally bioavailable PAI-1 antagonist, in a rat model of thrombosis

OBJECTIVE

To assess the antithrombotic and profibrinolytic effects of tiplaxtinin (PAI-039), an orally bioavailable antagonist of PAI-1, in rat models of thrombosis.

METHODS AND RESULTS

Carotid artery and vena cava vascular injury was produced by application of FeCl3 and blood flow was monitored using ultrasonic technology. To assess efficacy in a thrombosis prevention paradigm, PAI-039 was administered orally 90 min before injury (1-30 mg kg(-1)). To assess efficacy in a thrombosis treatment paradigm, vascular injury and stable thrombus formation were followed 4 h later by recovery and PAI-039 administration. PAI-039 prevented carotid artery occlusion in 20, 68 and 60% of animals pretreated with 0.3, 1.0 and 3.0 mg kg(-1), respectively. Time to occlusive thrombosis was increased from 18.2 +/- 4.6 min in controls to 32.5 +/- 8.7 (P = ns), 46.1 +/- 7.0 (P < 0.05), and 41.6 +/- 11.3 min (P < 0.05) in the respective PAI-039 treatment groups. In the vena cava protocol, PAI-039 pretreatment significantly reduced thrombus weight at PAI-039 doses of 3, 10 and 30 mg kg(-1). When PAI-039 was dosed in a treatment paradigm 4 h after stable arterial and venous thrombosis, a significant reduction in thrombus weight was observed 24 h later at PAI-039 doses of 3, 10 and 30 mg kg(-1). PAI-039 (10, 30 and 100 mg kg(-1)) had no effect on platelet aggregation in response to ADP or collagen and was not associated with increased bleeding or prolonged prothrombin time. In animals bearing no vascular injury, PAI-039 had no effect on circulating, low-levels of PAI-1 activity. In contrast, circulating PAI-1 activity increased 5-fold following the induction of vascular injury, which was completely neutralized by PAI-039.

CONCLUSIONS

PAI-039 exerts antithrombotic efficacy in rat models of arterial and venous vascular injury without effecting platelet aggregation.

Synthesis and SAR of 2-carboxylic acid indoles as inhibitors of plasminogen activator inhibitor-1

We synthesized and evaluated a novel series of 2-carboxylic acid indole-based inhibitors of plasminogen activator inhibitor-1 (PAI-1). Systematic modification of the N-1 position and the 5-position of the indole scaffold resulted in the identification of several compounds that showed good potency against PAI-1 in the spectrophotometric assay. This potency did not always translate to the antibody assay. Solubility and serum protein binding studies on selected analogs revealed that protein binding might be a factor in the poor correlation between the two assays.

Evaluation of PAI-039 [{1-benzyl-5-[4-(trifluoromethoxy)phenyl]-1H-indol-3-yl}(oxo)acetic acid], a novel plasminogen activator inhibitor-1 inhibitor, in a canine model of coronary artery thrombosis

We tested a novel, orally active inhibitor of plasminogen activator inhibitor-1 (PAI-1) in a canine model of electrolytic injury. Dogs received by oral gavage either vehicle (control) or the PAI-1 inhibitor PAI-039 [{1-benzyl-5-[4-(trifluoromethoxy)phenyl]-1H-indol-3-yl}(oxo)acetic acid] (1, 3, and 10 mg/kg) and were subjected to electrolytic injury of the coronary artery. PAI-039 caused prolongation in time to coronary occlusion (control, 31.7 +/- 6.3 min; 3 mg/kg PAI-039, 66.0 +/- 6.4 min; 10 mg/kg, 56.7 +/- 7.4 min; n = 5-6; p < 0.05) and a reduced thrombus weight (control, 7.6 +/- 1.5 mg; 10 mg/kg PAI-039, 3.6 +/- 1.0 mg; p < 0.05). Although occlusive thrombosis was observed across all groups based upon the absence of measurable blood flow, a high incidence (>60%) of spontaneous reperfusion occurred only in those groups receiving PAI-039. Spontaneous reperfusion in the 10 mg/kg PAI-039 group accounted for total blood flow (area under the curve of coronary blood flow) of 99.6 +/- 11.7 ml after initial thrombotic occlusion (p < 0.05 compared with control). Plasma PAI-1 activity was reduced in all drug-treated groups (percentage of reduction in activity p < 0.05; 10 mg/kg PAI-039), whereas ADP-, 9,11-dideoxy-11alpha,9alpha-epoxymethanoprostaglandin F(2alpha) (U46619)-, and collagen-induced platelet aggregation, as well as template bleeding and prothrombin time, remained unaffected by PAI-039. Ex vivo clot lysis analysis revealed normal clot formation but accelerated clot lysis in PAI-039-treated groups. The pharmacokinetic profile of PAI-039 indicated an oral bioavailability of 43 +/- 15.3% and a plasma half-life of 6.2 +/- 1.3 h. In conclusion, PAI-039 is an orally active prothrombolytic drug that inhibits PAI-1 and accelerates fibrinolysis while maintaining normal coagulation in a model of coronary occlusion.

Design and synthesis of oxadiazolidinediones as inhibitors of plasminogen activator inhibitor-1

A novel series of PAI-1 inhibitors containing an oxadiazolidinedione moiety were identified by high through-put screening. Optimization of substituents by parallel synthesis and the iterative design toward understanding structure-activity relationship to improve potency are described.

WAY-140312 reduces plasma PAI-1 while maintaining normal platelet aggregation

Plasminogen activator inhibitor-1 (PAI-1) is the major physiological inhibitor of tissue plasminogen activator (tPA) and is elevated in diseases of vascular remodeling. In this study, we describe an inhibitor of active PAI-1, WAY-140312. Using fluorescence spectroscopy, it was determined that WAY-140312 bound PAI-1 at a single binding site with a dissociation constant of 5 microM. In a biochemical assay determining direct tPA activity, human recombinant PAI-1 completely inhibited tPA, but this inhibition was blocked by WAY-140312 at an IC(50) of 15.6 microM. In vivo, a 10 mg/kg oral dose of WAY-140312 to rats produced a significant plasma reduction of active PAI-1. Bleeding time, thrombin clotting time, and ex vivo platelet aggregation induced by ADP (20 microM) or collagen (2.5 microg/ml) were not affected by administration of WAY-140312. These results are the first to demonstrate that an orally active PAI-1 inhibitor can reduce plasma PAI-1 activity while maintaining normal platelet aggregation and coagulation.

Release of PAI-1 by human preadipocytes and adipocytes independent of insulin and IGF-1

The effect of insulin and insulin-like growth factor-1 (IGF-1) on plasminogen activator inhibitor-1 (PAI-1) release from primary cultures of human preadipocytes and adipocytes has been investigated. Initial experiments measuring basal PAI-1 release (ng/ml) indicated variability between individual cultures. Using a novel technique for adipocyte quantitation, additional experiments were performed to determine PAI-1 release per cell, indicating a significant reduction with differentiation. Insulin and IGF-1 over a range of concentrations had no effect on PAI-1 release, and RT-PCR of PAI-1 mRNA following treatment with insulin and IGF-1 also indicated similar expression between treatments. The cultures did exhibit insulin-stimulated glyceraldehyde-3-phosphate dehydrogenase (GAPDH) expression and leptin synthesis following differentiation to the adipocyte phenotype. This is the first report of PAI-1 secretion by primary cultures of human preadipocytes and adipocytes, indicating PAI-1 release independent of insulin and IGF-1 and implicating other factors in the elevated plasma PAI-1 observed with insulin resistance.