John P. Caldwell

Iminoheterocycles as γ-secretase modulators

The synthesis of a novel series of iminoheterocycles and their structure-activity relationship (SAR) as modulators of gamma-secretase activity will be detailed. Encouraging SAR generated from a monocyclic core led to a structurally unique bicyclic core. Selected compounds exhibit good potency as gamma-secretase modulators, excellent rat pharmacokinetics, and lowering of Abeta42 levels in various in vivo models.

Discovery of silyl proline containing HCV NS5A inhibitors with pan-genotype activity: SAR development

HCV NS5A inhibitors have shown impressive in vitro potency profiles in HCV replicon assays thus making them attractive components for inclusion in an all oral fixed dose combination treatment regimen. Herein we describe the research efforts that led to the discovery of silyl proline containing HCV NS5A inhibitors such as 7e and 8a with pan-genotype activity profile and acceptable pharmacokinetic properties.

Structure and activity relationships of tartrate-based TACE inhibitors.

The syntheses and structure-activity relationships of the tartrate-based TACE inhibitors are discussed. The optimization of both the prime and non-prime sites led to compounds with picomolar activity. Several analogs demonstrated good rat pharmacokinetics.

Discovery of potent iminoheterocycle BACE1 inhibitors.

The synthesis of a series of iminoheterocycles and their structure-activity relationships (SAR) as inhibitors of the aspartyl protease BACE1 will be detailed. An effort to access the S3 subsite directly from the S1 subsite initially yielded compounds with sub-micromolar potency. A subset of compounds from this effort unexpectedly occupied a different binding site and displayed excellent BACE1 affinities. Select compounds from this subset acutely lowered Aβ40 levels upon subcutaneous and oral administration to rats.

Discovery of potent wall teichoic acid early stage inhibitors.

The widespread emergence of methicillin-resistant Staphylococcus aureus (MRSA) has dramatically eroded the efficacy of current β-lactam antibiotics and created an urgent need for novel treatment options. Using an S. aureus phenotypic screening strategy, we have identified small molecule early stage wall teichoic acid (WTA) pathway-specific inhibitors predicted to be chemically synergistic with β-lactams. These previously disclosed inhibitors, termed tarocins, demonstrate by genetic and biochemical means inhibition of TarO, the first step in WTA biosynthesis. Tarocins demonstrate potent bactericidal synergy in combination with broad spectrum β-lactam antibiotics across diverse clinical isolates of methicillin-resistant Staphylococci. The synthesis and structure-activity relationships (SAR) of a tarocin series will be detailed. Tarocins and other WTA inhibitors may provide a rational strategy to develop Gram-positive bactericidal β-lactam combination agents active against methicillin-resistant Staphylococci.

Benzimidazole analogs as WTA biosynthesis inhibitors targeting methicillin resistant Staphylococcus aureus.

A series of benzimidazole analogs have been synthesized to improve the profile of the previous lead compounds tarocin B and 1. The syntheses, structure-activity relationships, and selected biochemical data of these analogs are described. The optimization efforts allowed the identification of 21, a fluoro-substituted benzimidazole, exhibiting potent TarO inhibitory activity and typical profile for a wall teichoic acid (WTA) biosynthesis inhibitor. Compound 21 displayed a potent synergistic and bactericidal effect in combination with imipenem against diverse methicillin-resistant Staphylococci.

Iminopyrimidinones: A novel pharmacophore for the development of orally active renin inhibitors

The development of renin inhibitors with favorable oral pharmacokinetic profiles has been a longstanding challenge for the pharmaceutical industry. As part of our work to identify inhibitors of BACE1, we have previously developed iminopyrimidinones as a novel pharmacophore for aspartyl protease inhibition. In this letter we describe how we modified substitution around this pharmacophore to develop a potent, selective and orally active renin inhibitor.

Can We Make Small Molecules Lean? Optimization of a Highly Lipophilic TarO Inhibitor

We describe our optimization efforts to improve the physicochemical properties, solubility, and off-target profile of 1, an inhibitor of TarO, an early stage enzyme in the biosynthetic pathway for wall teichoic acid (WTA) synthesis. Compound 1 displayed a TarO IC50 of 125 nM in an enzyme assay and possessed very high lipophilicity (clogP = 7.1) with no measurable solubility in PBS buffer. Structure-activity relationship (SAR) studies resulted in a series of compounds with improved lipophilic ligand efficiency (LLE) consistent with the reduction of clogP. From these efforts, analog 9 was selected for our initial in vivo study, which in combination with subefficacious dose of imipenem (IPM) robustly lowered the bacterial burden in a neutropenic Staphylococci murine infection model. Concurrent with our in vivo optimization effort using 9, we further improved LLE as exemplified by a much more druglike analog 26.

2D-LC as an on-line desalting tool allowing peptide identification directly from MS unfriendly HPLC methods.

&NA; The increasing interest in peptides and proteins in pharmaceutical research and development has led to many challenges for the researchers tasked with characterizing and analyzing these larger molecules. Due to the more complicated impurity profile of peptides and proteins, multiple liquid chromatography techniques are often needed to achieve comprehensive analysis. However, many of these separation conditions require buffers, salts or additives that render them incompatible with mass spectrometry (MS) detection. Previous researchers have demonstrated proof of concept for the use of two dimensional liquid chromatography (2D‐LC) to provide convenient second dimension online desalting of components purified in the first chromatographic dimension. In this paper, we evaluated the Agilent heart‐cutting 2D‐LC system connected with an Agilent Q‐TOF mass spectrometer to address this frequently encountered analytical challenge. On this 2D‐LC/MS system, fractions containing the compounds of interest are separated by the first dimension using an MS incompatible mobile phase, then sent to a second dimension HPLC method where fast desalting using an MS compatible mobile phase is performed prior to MS analysis. The system allows for fast and direct collection of MS information for chromatographic peaks eluted in MS incompatible mobile phases, without requiring difficult, time consuming and error‐prone translation of chromatographic methods from MS incompatible to MS compatible eluents, or off‐line fraction collection and preparation. Several examples showing the application of the approach to complex mixtures containing peptides with impurities and positional isomers are presented. HighlightsCommercially available Agilent 2D‐LC is used as a simple, fully automated on‐line desalting tool for direct MS identification of impurities separated by MS incompatible HPLC.Peptide impurities and positional isomers are successfully identified by Agilent 2D‐LC/MS system.Off‐line fraction collection and translation of chromatographic methods are circumvented.

MK-8325: A silyl proline-containing NS5A inhibitor with pan-genotype activity for treatment of HCV

HCV NS5A inhibitors have shown impressive in vitro potency profiles in HCV replicon assays thus making them attractive components for inclusion in an all oral fixed dose combination regimen. Herein, we describe the discovery and characterization of silyl proline-containing HCV NS5A inhibitor MK-8325 with good pan-genotype activity and acceptable pharmacokinetic properties.