PF-04886847 (an Inhibitor of Plasma Kallikrein) Attenuates Inflammatory Mediators and Activation of Blood Coagulation in Rat Model of Lipopolysaccharide (LPS) - Induced Sepsis

Abstract

The plasma kallikrein-mediated proteolysis regulates both thrombosis and inflammation. Previous study has shown that PF-04886847 is a potent and competitive inhibitor of kallikrein, suggesting that it might be useful for the treatment of kallikrein-kinin mediated inflammatory and thrombotic disorders. In the rat model of lipopolysaccharide (LPS) -induced sepsis used in this study, pretreatment of rats with PF-04886847 (1 mg/kg) prior to LPS (10 mg/kg) prevented endotoxin-induced increase in granulocyte count in the systemic circulation. PF-04886847 significantly reduced the elevated plasma 6-keto PGF1α levels in LPS treated rats, suggesting that PF-04886847 could be useful in preventing hypotensive shock during sepsis. PF-04886847 did not inhibit LPS-induced increase in plasma TNF-α level. Pretreatment of rats with PF-04886847 prior to LPS did not attenuate endotoxin-induced decrease in platelet count and plasma fibrinogen levels as well as increase in plasma D-dimer levels. PF-04886847 did not protect the animals against LPS-mediated acute hepatic and renal injury and disseminated intravascular coagulation (DIC). Since prekallikrein (the zymogen form of plasma kallikrein) deficient patients have prolonged aPPT without having any bleeding disorder, the anti-thrombotic property and mechanism of action of PF-04886847 was assessed. In a rabbit balloon injury model designed to mimic clinical conditions of acute thrombotic events, PF-04886847 reduced thrombus mass dose-dependently. PF-04886847 (1 mg/kg) prolonged both activated partial thromboplastin time (aPTT) and prothrombin time (PT) in a dose-dependent manner. Although the findings of this study indicate that PF-04886847 possesses limited anti-thrombotic and anti-inflammatory effects, PF-04886847 may have therapeutic potential in other kallikrein-kinin mediated diseases.

Stable and Long-Lasting, Novel Bicyclic Peptide Plasma Kallikrein Inhibitors for the Treatment of Diabetic Macular Edema

“…Other PKal inhibitors have indeed been reported to more markedly impact the aPTT coagulation time. E.g., KALI-DY, an engineered molecule obtained from Kunitz domain phage libraries, prolonged the aPTT clotting time by more than 3.5-fold at 1 μM, and PF-04886847, a small molecule competitive inhibitor of PKal, increased the aPTT clotting time 2-fold at 14 μM . However, both KALI-DY and PF-04886847 inhibit Factor XIa at K i = 8.2 nM and 1 μM, respectively, , which should amplify their activity in the aPTT assay.…”

“…E.g., KALI-DY, an engineered molecule obtained from Kunitz domain phage libraries, prolonged the aPTT clotting time by more than 3.5-fold at 1 μM, 33 and PF-04886847, a small molecule competitive inhibitor of PKal, increased the aPTT clotting time 2-fold at 14 μM. 52 However, both KALI-DY and PF-04886847 inhibit Factor XIa at K i = 8.2 nM and 1 μM, respectively, 33,53 which should amplify their activity in the aPTT assay. It is therefore conceivable that the more limited effect of 1b and 2d on the aPTT clotting time is in fact due to their highly specific selectivity profile against other serine proteases from the clotting cascade.…”

Design of Small-Molecule Active-Site Inhibitors of the S1A Family Proteases as Procoagulant and Anticoagulant Drugs

“…Comparison of the complexes of PK with 42a (b) and benzamidine (d; PDB code 2ANY ) shows that overall the substrate-binding sites are similar with comparatively little induced fit in the complex with 42a . Peptidomimetic (kallistop, 43 ; MDCO-2010, 45 ) and nonpeptidic (PF-04886847, 44 ) PK inhibitors are also known, and a likely PK binding mode for 43 (based on docking to the 4ZJ6 receptor) is shown in panel e. This compound makes many similar contacts with PK as the peptide 42a and additionally forms polar interactions between the ligand benzoic acid group and the K147 residue. (f) The pharmacophoric similarity between the small-molecule PK inhibitors is evident from flexible alignment of 43 (magenta) and 44 (cyan) with the modeled bioactive conformation of 45 (green).…”

Plasma Kallikrein Inhibitors in Cardiovascular Disease

“…Using a balloon-induced femoral artery injury model in hypercholesterolemic rabbits, we recently demonstrated that intravenous administration of a potent, small molecule plasma kallikrein inhibitor significantly reduced thrombus mass with minimal effect on bleeding time. 37,38 Similarly, other plasma kallikrein inhibitors have also shown to have antithrombotic properties in vitro or in animal models of venous and arterial thrombosis ( Table 1). [37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55] These studies provide strong evidence that although components of the plasma KKS are dispensable for normal hemostasis, they play a central role in pathological thrombus formation.…”