Julia A. Hubbard

Second generation of BACE-1 inhibitors part 3: Towards non hydroxyethylamine transition state mimetics

Our first generation of hydroxyethylamine BACE-1 inhibitors proved unlikely to provide molecules that would lower amyloid in an animal model at low oral doses. This observation led us to the discovery of a second generation of inhibitors having nanomolar activity in a cell-based assay and with the potential for improved pharmacokinetic profiles. In this Letter, we describe our successful strategy for the optimization of oral bioavailability and also give insights into the design of compounds with the potential for improved brain penetration.

Nuclear magnetic resonance spectroscopy reveals the functional state of the signalling protein CheY in vivo in Escherichia coli

Two‐component signal transduction (TCST) pathways are regulatory systems that are highly homologous throughout the bacterial kingdom. Their established role in virulence and absence in vertebrates has made TCST an attractive target for therapeutic intervention. However, such systems have yet to yield success in the development of novel antibiotics. CheY serves as a prototype for the analysis of response regulator function. The protein structure exhibits several conformations by both X‐ray and nuclear magnetic resonance (NMR) analyses. Knowledge of which structures are relevant in vivo would be valuable in a rational drug design project. Our aim was to probe the in vivo conformation and ligand binding of CheY in Escherichia coli under resting conditions by in‐cell NMR methods. CheY was selectively labelled with 15N by the control of growth and expression conditions. NMR spectra obtained in vivo demonstrated that the Mg2+ complex was the predominant form even though cells were resuspended in metal‐free buffers and the intracellular free Mg2+ was low. In‐cell NMR also confirmed the uptake and in vivo binding mode to CheY of small‐molecular‐weight compounds identified in vitro. This paper reports the first observation of the structure and interactions with a potential drug of a regulator protein in its native host in vivo using NMR spectroscopy.

Second generation of BACE-1 inhibitors. Part 1: The need for improved pharmacokinetics

Inhibition of the aspartyl protease BACE-1 has the potential to deliver a disease-modifying therapy for Alzheimers disease. We have recently disclosed a series of transition-state mimetic BACE-1 inhibitors showing nanomolar potency in cell-based assays. Amongst them, GSK188909 (compound 2) had favorable pharmacokinetics and was the first orally bioavailable inhibitor reported to demonstrate brain amyloid lowering in an animal model. In this Letter, we describe the reasons that led us to favor a second generation of inhibitors for further in vivo studies.

Second Generation of Bace-1 Inhibitors Part 2: Optimisation of the Non-Prime Side Substituent.

Our first generation of hydroxyethylamine transition-state mimetic BACE-1 inhibitors allowed us to validate BACE-1 as a key target for Alzheimers disease by demonstrating amyloid lowering in an animal model, albeit at rather high doses. Finding a molecule from this series which was active at lower oral doses proved elusive and demonstrated the need to find a novel series of inhibitors with improved pharmacokinetics. This Letter describes the discovery of such inhibitors.

Synthesis and Evaluation of Novel Alpha-Amino Cyclic Boronates as Inhibitors of Hcv Ns3 Protease.

We have designed and synthesized a novel series of alpha-amino cyclic boronates and incorporated them successfully in several acyclic templates at the P1 position. These compounds are inhibitors of the HCV NS3 serine protease, and structural studies show that they inhibit the NS3 protease by trapping the Ser-139 hydroxyl group in the active site. Synthetic methodologies and SARs of this series of compounds are described.

Unlocking the secrets of the gatekeeper: methods for stabilizing and crystallizing GPCRs.

G-protein coupled receptors (GPCRs) are integral membrane cell surface receptors with key roles in mediating the cellular responses to a wide range of biologically relevant molecules including hormones, neurotransmitters and importantly the majority of currently available drugs. The first high-resolution, X-ray crystallographic structure of a GPCR, that of rhodopsin, was obtained in 2000. It took a further seven years for the next structure, that of the β2 adrenergic receptor. Remarkably, at the time of writing, there have been an astonishing 18 further independent high-resolution GPCR structures published in the last five years (overall total of 68 structures in different conformations or bound to different ligands). Of particular note is the recent structure of the β2 adrenergic receptor in complex with its cognate heterotrimeric G-protein revealing for the first time molecular details of the interaction between a GPCR and the complete G-protein. Together these structures have provided unprecedented detail into the mechanism of action of these incredibly important proteins. This review describes several key methodological advances that have made such extraordinarily fast progress possible.

Novel macrocyclic HCV NS3 protease inhibitors derived from α-amino cyclic boronates

A novel series of P2-P4 macrocyclic HCV NS3/4A protease inhibitors with α-amino cyclic boronates as warheads at the P1 site was designed and synthesized. When compared to their linear analogs, these macrocyclic inhibitors exhibited a remarkable improvement in cell-based replicon activities, with compounds 9a and 9e reaching sub-micromolar potency in replicon assay. The SAR around α-amino cyclic boronates clearly established the influence of ring size, chirality and of the substitution pattern. Furthermore, X-ray structure of the co-crystal of inhibitor 9a and NS3 protease revealed that Ser-139 in the enzyme active site traps boron in the warhead region of 9a, thus establishing its mode of action.

Conformation of the cytoplasmic domain of phospholamban by NMR and CD

Nuclear magnetic resonance (NMR) and circular dichroism (CD) spectroscopy have been used to characterize the conformation of the putative cytoplasmic domain of phospholamban (PLB), an oligomeric membrane-bound protein which regulates the activity of the cardiac sarcoplasmic reticulum Ca(2+)-dependent ATPase. In aqueous solution the 25-residue peptide adopts a number of rapidly interconverting conformers with no secondary structural type obviously predominating. However, in trifluoroethanol (TFE) the conformation, while still highly dynamic, is characterized by a high proportion of helical structures. Evidence for this is provided by alpha CH chemical shifts and low NH chemical shift temperature coefficients, small NH-alpha CH intraresidue scalar coupling constants, a substantial number of distinctive interresidue nuclear Overhauser effects (NOEs) [dNN(i, i + 1), d alpha N(i, i + 3), d alpha beta(i, i + 3) and d alpha N(i, i + 4)] and characteristic CD bands at 190 (positive), 206 (negative) and 222 nm (negative). The helicity is interrupted around Pro-21. The activity of PLB is regulated by phosphorylation at either Ser-16 or Thr-17. CD shows that phosphorylation at Ser-16 by the cAMP-activated protein kinase causes about an 11% decrease in alpha-helical content in TFE.

Loss of constitutive activity is correlated with increased thermostability of the human adenosine A2A receptor

Thermostabilization by mutagenesis is one method which has facilitated the determination of high‐resolution structures of the adenosine A2A receptor (A2AR). Sets of mutations were identified, which both thermostabilized the receptor and resulted in preferential agonist (Rag23 mutant) or antagonist (Rant5 and Rant21) binding forms as assessed by radioligand binding analysis. While the ligand‐binding profiles of these mutants are known, the effects these mutations have on receptor activation and downstream signalling are less well characterized.