Xention (United Kingdom)

Two double-blind, randomized studies were conducted to assess the tolerability, pharmacokinetics and pharmacodynamics of oral TA-8995, a new cholesteryl ester transfer protein (CETP) inhibitor, in healthy subjects. Study 1: Subjects received single doses of TA-8995 or placebo (fasted). Doses were 5, 10, 25, 50 (fed/fasted), 100 and 150 mg (Caucasian males, 18-55 years), 25 mg (Caucasian males, > 65 years and Caucasian females, 18-55 years), 25, 50, 100 and 150 mg (Japanese males, 18-55 years). Study 2: Caucasian males (18-55 years) received 1, 2.5, 10 or 25 mg once daily TA-8995 or placebo for 21-28 days. Blood and urine for pharmacokinetics and/or pharmacodynamics were collected. Tolerability was assessed by adverse events, vital signs, electrocardiograms and laboratory safety tests. Peak TA-8995 concentrations occurred approximately 4 h post-dose. Mean half-lives ranged from 81 to 166 h, without an obvious dose relationship. Exposure increased less than proportionally to dose. TA-8995 was not excreted in urine. Following 2.5 to 25 mg once daily dosing, TA-8995 demonstrated nearly complete inhibition of CETP activity (92-99%), increased high density lipoprotein-cholesterol (HDL-C) by 96 to 140% and decreased low density liporotein-cholesterol (LDL-C) by 40% to 53%. There were dose-related increases in apolipoproteins A-1 and E, HDL2-C and HDL3-C, and decreases in apolipoprotein B and lipoprotein A. There was no evidence of significant effects of age, gender, ethnicity or food on pharmacokinetics or pharmacodynamics. All doses were well tolerated. TA-8995 is a potent CETP inhibitor and warrants further investigation.

The human electrophysiological and pharmacological properties of XEN-D0101 were evaluated to assess its usefulness for treating atrial fibrillation (AF). XEN-D0101 inhibited Kv1.5 with an IC50 of 241 nM and is selective over non-target cardiac ion channels (IC50 Kv4.3, 4.2 μM; hERG, 13 μM; activated Nav1.5, >100 μM; inactivated Nav1.5, 34 μM; Kir3.1/3.4, 17 μM; Kir2.1, >>100 μM). In atrial myocytes from patients in sinus rhythm (SR) and chronic AF, XEN-D0101 inhibited non-inactivating outward currents (Ilate) with IC50 of 410 and 280 nM, respectively, and peak outward currents (Ipeak) with IC50 of 806 and 240 nM, respectively. Whereas Ilate is mainly composed of IKur, Ipeak consists of IKur and Ito. Therefore, the effects on Ito alone were estimated from a double-pulse protocol where IKur was inactivated (3.5 µM IC50 in SR and 1 µM in AF). Thus, inhibition of Ipeak is because of IKur reduction and not Ito. XEN-D0101 significantly prolonged the atrial action potential duration at 20%, 50%, and 90% of repolarization (AF tissue only) and significantly elevated the atrial action potential plateau phase and increased contractility (SR and AF tissues) while having no effect on human ventricular action potentials. In healthy volunteers, XEN-D0101 did not significantly increase baseline- and placebo-adjusted QTc up to a maximum oral dose of 300 mg. XEN-D0101 is a Kv1.5/IKur inhibitor with an attractive atrial-selective profile.

In endothelial cells, neuropilin-1 (NRP1) binds vascular endothelial growth factor (VEGF)-A and is thought to act as a coreceptor for kinase insert domain-containing receptor (KDR) by associating with KDR and enhancing VEGF signaling. Here we report mutations in the NRP1 b1 domain (Y297A and D320A), which result in complete loss of VEGF binding. Overexpression of Y297A and D320A NRP1 in human umbilical vein endothelial cells reduced high-affinity VEGF binding and migration toward a VEGF gradient, and markedly inhibited VEGF-induced angiogenesis in a coculture cell model. The Y297A NRP1 mutant also disrupted complexation between NRP1 and KDR and decreased VEGF-dependent phosphorylation of focal adhesion kinase at Tyr407, but had little effect on other signaling pathways. Y297A NRP1, however, heterodimerized with wild-type NRP1 and NRP2 indicating that nonbinding NRP1 mutants can act in a dominant-negative manner through formation of NRP1 dimers with reduced binding affinity for VEGF. These findings indicate that VEGF binding to NRP1 has specific effects on endothelial cell signaling and is important for endothelial cell migration and angiogenesis mediated via complex formation between NRP1 and KDR and increased signaling to focal adhesions. Identification of key residues essential for VEGF binding and biological functions provides the basis for a rational design of antagonists of VEGF binding to NRP1.