Michael P. Bova

Chemoproteomics-Based Design of Potent LRRK2-Selective Lead Compounds That Attenuate Parkinson’s Disease-Related Toxicity in Human Neurons

Leucine-rich repeat kinase-2 (LRRK2) mutations are the most important cause of familial Parkinsons disease, and non-selective inhibitors are protective in rodent disease models. Because of their poor potency and selectivity, the neuroprotective mechanism of these tool compounds has remained elusive so far, and it is still unknown whether selective LRRK2 inhibition can attenuate mutant LRRK2-dependent toxicity in human neurons. Here, we employ a chemoproteomics strategy to identify potent, selective, and metabolically stable LRRK2 inhibitors. We demonstrate that CZC-25146 prevents mutant LRRK2-induced injury of cultured rodent and human neurons with mid-nanomolar potency. These precise chemical probes further validate this emerging therapeutic strategy. They will enable more detailed studies of LRRK2-dependent signaling and pathogenesis and accelerate drug discovery.

Design of an orally efficacious hydroxyethylamine (HEA) BACE-1 inhibitor in a preclinical animal model.

In this Letter, we describe our efforts to design HEA BACE-1 inhibitors that are highly permeable coupled with negligible levels of permeability-glycoprotein activity. These efforts culminate in producing 16 which lowers Αβ by 28% and 32% in the cortex and CSF, respectively, in the preclinical wild type Hartley guinea pig animal model when dosed orally at 30mpk BID for 2.5days.

Design and synthesis of highly selective, orally active Polo-like kinase-2 (Plk-2) inhibitors

Polo-like kinase-2 (Plk-2) is a potential therapeutic target for Parkinsons disease and this Letter describes the SAR of a series of dihydropteridinone based Plk-2 inhibitors. By optimizing both the N-8 substituent and the biaryl region of the inhibitors we obtained single digit nanomolar compounds such as 37 with excellent selectivity for Plk-2 over Plk-1. When dosed orally in rats, compound 37 demonstrated a 41-45% reduction of pS129-α-synuclein levels in the cerebral cortex.

Design and synthesis of thiophene dihydroisoquinolines as novel BACE1 inhibitors.

Utilizing a structure based design approach, combined with extensive medicinal chemistry execution, highly selective, potent and novel BACE1 inhibitor 8 (BACE1 Alpha assay IC50=8nM) was made from a weak μM potency hit in an extremely efficient way. The detailed SAR and general design approaches will be discussed.

Label free fragment screening using surface plasmon resonance as a tool for fragment finding - analyzing parkin, a difficult CNS target.

Surface Plasmon Resonance (SPR) is rarely used as a primary High-throughput Screening (HTS) tool in fragment-based approaches. With SPR instruments becoming increasingly high-throughput it is now possible to use SPR as a primary tool for fragment finding. SPR becomes, therefore, a valuable tool in the screening of difficult targets such as the ubiquitin E3 ligase Parkin. As a prerequisite for the screen, a large number of SPR tests were performed to characterize and validate the active form of Parkin. A set of compounds was designed and used to define optimal SPR assay conditions for this fragment screen. Using these conditions, more than 5000 pre-selected fragments from our in-house library were screened for binding to Parkin. Additionally, all fragments were simultaneously screened for binding to two off target proteins to exclude promiscuous binding compounds. A low hit rate was observed that is in line with hit rates usually obtained by other HTS screening assays. All hits were further tested in dose responses on the target protein by SPR for confirmation before channeling the hits into Nuclear Magnetic Resonance (NMR) and other hit-confirmation assays.

Structure-based design of novel dihydroisoquinoline BACE-1 inhibitors that do not engage the catalytic aspartates.

The structure-activity relationship of a series of dihydroisoquinoline BACE-1 inhibitors is described. Application of structure-based design to screening hit 1 yielded sub-micromolar inhibitors. Replacement of the carboxylic acid of 1 was guided by X-ray crystallography, which allowed the replacement of a key water-mediated hydrogen bond. This work culminated in compounds such as 31, which possess good BACE-1 potency, excellent permeability and a low P-gp efflux ratio.

Quantifying Amyloid Beta (Aβ)–Mediated Changes in Neuronal Morphology in Primary Cultures: Implications for Phenotypic Screening

Alzheimer’s disease (AD) is a devastating neurodegenerative disease affecting millions of people. The amyloid hypothesis suggests that the pathogenesis of AD is related to the accumulation of amyloid beta (Aβ) in the brain. Herein, the authors quantify Aβ-mediated changes in neuronal morphology in primary cultures using the Cellomics neuronal profiling version 3.5 (NPv3.5) BioApplication. We observed that Aβ caused a 33% decrease in neurite length in primary human cortical cultures after 24 h of treatment compared with control-treated cultures. We also determined that quantifying changes of neuronal morphology was a more sensitive indicator of nonlethal cell injury than traditional cytotoxicity assays. Aβ-mediated neuronal deficits observed in human cortical cultures were also observed in primary rat hippocampal cultures, where we demonstrated that the integrin-blocking antibody, 17E6, completely abrogated Aβ-mediated cytotoxicity. Finally, we showed that Aβ challenge to 21 days in vitro rat hippocampal cultures reduced synapsin staining to 14% of control-treated cultures. These results are consistent with the finding that loss of presynaptic integrity is one of the initial deficits observed in AD. The implementation of phenotypic screens to identify compounds that block Aβ-mediated cytotoxicity in primary neuronal cultures may lead to the development of novel strategies to prevent AD.

Design, synthesis and structure-activity relationship of novel [3.3.1] bicyclic sulfonamide-pyrazoles as potent γ-secretase inhibitors.

The structure-activity relationship (SAR) of a novel, potent and metabolically stable series of sulfonamide-pyrazoles that attenuate β-amyloid peptide synthesis via γ-secretase inhibition is detailed herein. Sulfonamide-pyrazoles that are efficacious in reducing the cortical Aβx-40 levels in FVB mice via a single PO dose, as well as sulfonamide-pyrazoles that exhibit selectivity for inhibition of APP versus Notch processing by γ-secretase, are highlighted.

Emerging drug targets in amyotrophic lateral sclerosis

Introduction: Amyotrophic lateral sclerosis (ALS) is a progressive and devastating neurodegenerative disease resulting from injury and death of upper and lower motor neurons. Symptoms initially include muscle weakness and twitching and subsequently progress to muscle atrophy, complete loss of limb use, respiratory difficulties and ultimately death. Multiple biological mechanisms have been implicated in ALS and a complex etiology has been described. As a result, drug discovery researchers have few validated targets to pursue and patients have few therapeutic options. Areas covered: Identification of new drug targets in ALS can be facilitated by a detailed understanding of the processes and genes that contribute to pathogenesis. Accordingly, this review summarizes current hypotheses regarding underlying mechanisms for motor neuron susceptibility in ALS. An overview of emerging and tractable drug targets that could result in therapeutic breakthroughs is provided. Expert opinion: Despite the immense progress that has been made in understanding ALS over the last decade, riluzole remains the only approved drug to treat ALS. Combining structure-guided drug design applied to validated and pharmaceutically tractable targets with disease-relevant phenotypic screens will allow for the identification of novel drug targets and potentially breakthrough therapeutics for ALS.

Thermodynamic and kinetic characterization of hydroxyethylamine β-secretase-1 inhibitors

Alzheimers disease (AD) is a devastating neurodegenerative disease affecting millions of people. β-Secretase-1 (BACE-1), an enzyme involved in the processing of the amyloid precursor protein (APP) to form Aβ, is a well validated target for AD. Herein, the authors characterize 10 randomly selected hydroxyethylamine (HEA) BACE-1 inhibitors in terms of their association and dissociation rate constants and thermodynamics of binding using surface plasmon resonance (SPR). Rate constants of association (ka) measured at 25 °C ranged from a low of 2.42×10(4) M(-1) s(-1) to the highest value of 8.3×10(5) M(-1) s(-1). Rate constants of dissociation (kd) ranged from 1.09×10(-4) s(-1) (corresponding to a residence time of close to three hours), to the fastest of 0.028 s(-1). Three compounds were selected for further thermodynamic analysis where it was shown that equilibrium binding was enthalpy driven while unfavorable entropy of binding was observed. Structural analysis revealed that upon ligand binding, the BACE-1flap folds down over the bound ligand causing an induced fit. The maximal difference between alpha carbon positions in the open and closed conformations of the flap was over 5 Å. Thus the negative entropy of binding determined using SPR analysis was consistent with an induced fit observed by structural analysis.