Discovery of novel 2,8-diazaspiro[4.5]decanes as orally active glycoprotein IIb-IIIa antagonists.

In our efforts to develop orally active GPIIb-IIIa antagonists with improved pharmaceutical properties, we have utilized a novel 2,8-diazaspiro[4.5]decane scaffold as a template. We describe here our investigation of a variety of templates including spiropiperidinyl-gamma-lactams, spiropiperidinylimide, spiropiperidinylureas, and spiropiperidinylhydantoins. With the appropriate acidic and basic pharmacophores in place, each template yielded analogues with potent GPIIb-IIIa inhibitory activity. One of the compounds, 59 (CT50787), was also used to demonstrate for the first time the use of a pharmacological agent which is alphaIIbbeta3 specific to display biological activity in a lower species such as mouse and to extend bleeding times. Evaluation of the pharmacokinetic properties of selected compounds from each series in rat, dog, and cynomolgus monkey has led to the identification of 22 (CT51464), a double prodrug, with excellent pharmacokinetic properties. It exhibited good pharmacokinetic profile across species (F% = 33 (Cyno), 73 (dog), 22 (rat); t(1/2)(beta)() = 14.2 h (Cyno), 8.97 h (dog), 1.81 h (rat)). The biologically active form, 23 (CT50728), displayed inhibition of platelet aggregation in platelet rich plasma (PRP) with an IC(50) value of 53 nM in citrate buffer, 110 nM in PPACK anticoagulated PRP, and 4 nM in solid-phase GPIIb-IIIa competition binding assay (ELISA). Both 23 and 22 were stable in human liver microsomes, did not inhibit the P450 3A4 isozyme, and had low protein binding (18.22% for 23) and a desirable log P (0.45 +/- 0.06 for 22, and -0.91 +/- 0.32 for 23). It is predicted that the high oral bioavailability for these compounds in multiple species should translate into lower intra- and intersubject variability in man. The long plasma half-life of the lead is consistent with once or twice daily administration for chronic therapy. Analogue 22 (CT51464) thus appears to be a promising oral GPIIb-IIIa inhibitor with significantly improved pharmacokinetic properties over the previously described clinical candidates and may be found useful in the treatment of arterial occlusive disorders.

GP IIb/IIIa inhibition with eptifibatide lowers levels of soluble CD40L and RANTES after percutaneous coronary intervention.

Platelets are the most abundant blood source of CD40L, a proinflammatory and prothrombotic costimulatory molecule implicated in atherosclerosis. Agonist stimulation results in the secretion of a soluble form of CD40L (sCD40L) and GP IIb/IIIa receptor inhibition blocks secretion of sCD40L in vitro. However, the effect of GP IIb/IIIa inhibition on sCD40L levels in humans is unknown. Plasma sCD40L and inflammatory markers were measured (t = 0, 0.5, 2, and 24 hr post-PCI) in a cohort of patients receiving abciximab (n = 15), eptifibatide (n = 15), or no GP IIb/IIIa inhibitor (n = 15). PCI in the absence of GP IIb/IIIa inhibitor was associated with a small but measurable rise in sCD40L and the platelet-derived chemokine RANTES. In contrast, eptifibatide significantly lowered baseline sCD40L (P = 0.018) and RANTES (P = 0.006) levels. This effect was not observed with abciximab. GP IIb/IIIa inhibition with eptifibatide lowers levels of sCD40L and RANTES post-stenting, possibly conferring anti-inflammatory as well as antithrombotic effects.

Inhibitory effects of glycoprotein IIb/IIIa antagonists and aspirin on the release of soluble CD40 ligand during platelet stimulation.

BACKGROUND: Glycoprotein (GP) IIb/IIIa antagonists inhibit platelet aggregation, an activity attributed to the clinical benefits of these drugs in settings that involve acute coronary thrombosis. However, platelet activation and subsequent aggregation are now known to cause the release of a soluble form of CD40 ligand (sCD40L), a prothrombotic and proinflammatory protein with GP IIb/IIIa binding activity and an established role in atherosclerotic lesion progression. The present study was designed to determine what effect GP IIb/IIIa antagonists have on the release of sCD40L. METHODS AND RESULTS: Doses of eptifibatide, abciximab, and tirofiban that inhibited platelet aggregation by at least 80% also inhibited sCD40L release in vitro (by 85%, 57%, and 80%, respectively). When platelets were stimulated with a thrombin receptor agonist, inhibition by GP IIb/IIIa antagonists occurred without affecting the release of betaTG, an alpha-granule protein. Unexpectedly, concentrations of the 3 antagonists that blocked aggregation by only 20% to 50% potentiated the release of sCD40L (by 19% to 26%). Platelets from aspirin-treated individuals were partially protected from sCD40L release, but only when the agonist was collagen, an affect augmented by the addition of GP IIb/IIIa antagonists. CONCLUSIONS: These studies suggest that the mechanisms responsible for the clinical benefits of GP IIb/IIIa antagonists (at doses that optimally inhibit aggregation) and of aspirin may not be limited to the inhibition of thrombosis through their blockade of platelet aggregation but may also involve the inhibition of inflammation and thrombosis through their blockade of sCD40L release. These studies also provide a mechanism by which suboptimal doses of GP IIb/IIIa antagonists may be proinflammatory.

Cardiopulmonary bypass induces release of soluble CD40 ligand.

BACKGROUND: Cardiopulmonary bypass (CPB) is known to induce platelet activation, thrombosis, thrombocytopenia, and a systemic inflammatory response. It is known that CD40 ligand (CD40L) exists in platelets, that a soluble form of this protein (sCD40L) is released on platelet activation, that platelets are the primary source of sCD40L in blood, and that sCD40L is involved in thrombosis and inflammation. The present study was designed to determine whether sCD40L is released during CPB. Methods and Results- Blood was obtained from patients undergoing CPB-requiring surgery and analyzed for sCD40L, interleukin-6, and platelet factor 4 and beta-thromboglobulin (markers of platelet activation). Platelets were also isolated and analyzed for their levels of CD40L. Plasma levels of sCD40L increased >1.7-fold (from 0.29 to 0.51 ng/mL, P=0.001) within 1 hour on CPB and increased further to 3.7-fold (to 1.08 ng/mL, P=0.03) 2 hours after the procedure. Half of the released sCD40L was cleared in 2 hours, which allowed the sCD40L to return to approximately baseline levels 8 hours after the procedure. The platelet content of CD40L was decreased by 40% (2.675 to 1.64 ng/10(8) platelets, P=0.001) 1 hour after initiation of CPB and was similar to that observed for platelet factor 4 and beta-thromboglobulin. Interleukin-6, a marker of inflammation, also increased during CPB. CONCLUSIONS: The present study demonstrates that CPB causes an increase in the concentration of plasma sCD40L. The corresponding decrease in platelet CD40L suggests that this prothrombotic and proinflammatory protein was derived primarily from platelets and may contribute to the thrombotic and inflammatory complications associated with CPB.