siRNA-mediated knockdown of P450 oxidoreductase in rats: a tool to reduce metabolism by CYPs and increase exposure of high clearance compounds.

Purpose: To develop a tool based on siRNA-mediated knockdown of hepatic P450 oxidoreductase (POR) to decrease the CYP-mediated metabolism of small molecule drugs that suffer from rapid metabolism in vivo, with the aim of improving plasma exposure of these drugs.

Methods: siRNA against the POR gene was delivered using lipid nanoparticles (LNPs) into rats. The time course of POR mRNA knockdown, POR protein knockdown, and loss of POR enzyme activity was monitored.

Development of a liver-targeted siRNA delivery platform with a broad therapeutic window utilizing biodegradable polypeptide-based polymer conjugates.

The greatest challenge standing in the way of effective in vivo siRNA delivery is creating a delivery vehicle that mediates a high degree of efficacy with a broad therapeutic window. Key structure-activity relationships of a poly(amide) polymer conjugate siRNA delivery platform were explored to discover the optimized polymer parameters that yield the highest activity of mRNA knockdown in the liver. At the same time, the poly(amide) backbone of the polymers allowed for the metabolism and clearance of the polymer from the body very quickly, which was established using radiolabeled polymers to demonstrate the time course of biodistribution and excretion from the body.

An in vivo evaluation of amphiphilic, biodegradable peptide copolymers as siRNA delivery agents.

A series of amphiphilic, biodegradable polypeptide copolymers were prepared for the delivery of siRNA (short interfering ribonucleic acid). The molecular weight (or polymer chain length) of the linear polymer was controlled by reaction stoichiometry for the 11.5, 17.

Pharmacological properties of MK-3207, a potent and orally active calcitonin gene-related peptide receptor antagonist.

Calcitonin gene-related peptide (CGRP) has long been hypothesized to play a key role in migraine pathophysiology, and the advent of small-molecule antagonists has clearly demonstrated a clinical link between blocking the CGRP receptor and migraine efficacy. 2-[(8R)-8-(3,5-Difluorophenyl)-10-oxo-6,9-diazaspiro[4.5]dec-9-yl]-N-[(2R)-2'-oxo-1,1',2',3-tetrahydrospiro[indene-2,3'-pyrrolo[2,3-b]pyridin]-5-yl]acetamide (MK-3207) represents the third CGRP receptor antagonist to display clinical efficacy in migraine trials.

Effect of P-glycoprotein-mediated efflux on cerebrospinal fluid concentrations in rhesus monkeys.

Brain penetration of drugs which are subject to P-glycoprotein (Pgp)-mediated efflux is attenuated, as manifested by the fact that the cerebrospinal fluid concentration (C(CSF)), a good surrogate of the unbound brain concentration (C(ub)), is lower than the unbound plasma concentration (C(up)) for Pgp substrates. In rodents, the attenuation magnitude of brain penetration by Pgp-mediated efflux has been estimated by correlating the ratio of CSF to plasma exposures (C(CSF)/C(p)) with the unbound fraction in plasma (f(u)) upon the incorporation of the in vivo or in vitro Pgp-mediated efflux ratios (ERs). In the present work, we investigated the impact of Pgp-mediated efflux on C(CSF) in monkeys.

Strategies toward improving the brain penetration of macrocyclic tertiary carbinamine BACE-1 inhibitors.

This letter describes replacements for the P3 amide moiety present in previously reported tertiary carbinamine macrolactones. Although P-gp efflux issues associated with these amide-macrolactones were solved and full brain penetration was measured in one case, potency was compromised in the process.

Design, synthesis, and SAR of macrocyclic tertiary carbinamine BACE-1 inhibitors.

This Letter describes the design and synthesis of tertiary carbinamine macrocyclic inhibitors of the beta-secretase (BACE-1) enzyme. These macrocyclic inhibitors, some of which incorporate novel P2 substituents, display a 2- to 100-fold increase in potency relative to the previously described acyclic analogs while affording greater stability.

Identification of novel, orally bioavailable spirohydantoin CGRP receptor antagonists.

A rapid analogue approach to identification of spirohydantoin-based CGRP antagonists provided novel, low molecular weight leads. Modification of these leads afforded a series of nanomolar benzimidazolinone-based CGRP receptor antagonists. The oral bioavailability of these antagonists was inversely correlated with polar surface area, suggesting that membrane permeability was a key limitation to absorption.

Interactions of human P-glycoprotein with simvastatin, simvastatin acid, and atorvastatin.

Purpose: In this study, P-glycoprotein (P-gp) mediated efflux of simvastatin (SV), simvastatin acid (SVA), and atorvastatin (AVA) and inhibition of P-gp by SV, SVA, and AVA were evaluated to assess the role of P-gp in drug interactions.

Methods: P-gp mediated efflux of SV, SVA, and AVA was determined by directional transport across monolayers of LLC-PK1 cells and LLC-PK1 cells transfected with human MDR1. Inhibition of P-gp was evaluated by studying the vinblastine efflux in Caco-2 cells and in P-gp overexpressing KBV1 cells at concentrations of SV, SVA, and AVA up to 50 microM.