Elizabeth M. Smith

Discovery of Cyclic Acylguanidines as Highly Potent and Selective beta-Site Amyloid Cleaving Enzyme (BACE) Inhibitors: Part I-Inhibitor Design and Validation

A number of novel amidine containing heterocycles were designed to reproduce the unique interaction pattern, revealed by X-ray crystallography, between the BACE-1 catalytic diad and a weak NMR screening hit (3), with special attention paid to maintaining the appropriate basicity and limiting the number of H-bonding donors of these scaffolds. The iminohydantoin cores (10 and 23) were examined first and found to interact with the catalytic diad in one of two binding modes (A and B), each with the iminohydantoin core flipped 180 degrees in relation to the other. The amidine structural motif within each core forms a bidentate interaction with a different aspartic acid of the catalytic diad. Both modes reproduced a highly conserved interaction pattern between the inhibitors and the catalytic aspartates, as revealed by 3. Potent iminohydantoin BACE-1 inhibitors have been obtained, validating the molecular design as aspartyl protease catalytic site inhibitors. Brain penetrant small molecule BACE inhibitors with high ligand efficiencies have been discovered, enabling multiple strategies for further development of these inhibitors into highly potent, selective and in vivo efficacious BACE inhibitors.

Application of Fragment-Based NMR Screening, X-ray Crystallography, Structure-Based Design, and Focused Chemical Library Design to Identify Novel μM Leads for the Development of nM BACE-1 (β-Site APP Cleaving Enzyme 1) Inhibitors

Fragment-based NMR screening, X-ray crystallography, structure-based design, and focused chemical library design were used to identify novel inhibitors for BACE-1. A rapid optimization of an initial NMR hit was achieved by a combination of NMR and a functional assay, resulting in the identification of an isothiourea hit with a K(d) of 15 microM for BACE-1. NMR data and the crystal structure revealed that this hit makes H-bond interactions with the two catalytic aspartates, occupies the nonprime side region of the active site of BACE-1, and extends toward the S3 subpocket (S3sp). A focused NMR-based search for heterocyclic isothiourea isosteres resulted in several distinct classes of BACE-1 active site directed compounds with improved chemical stability and physicochemical properties. The strategy for optimization of the 2-aminopyridine lead series to potent inhibitors of BACE-1 was demonstrated. The structure-based design of a cyclic acylguanidine lead series and its optimization into nanomolar BACE-1 inhibitors are the subject of the companion paper

The discovery of potent, selective, and orally active pyrazoloquinolines as PDE10A inhibitors for the treatment of Schizophrenia.

High-throughput screening identified a series of pyrazoloquinolines as PDE10A inhibitors. The SAR development led to the discovery of compound 27 as a potent, selective, and orally active PDE10A inhibitor. Compound 27 inhibits MK-801 induced hyperactivity at 3mg/kg with an ED(50) of 4mg/kg and displays a ∼6-fold separation between the ED(50) for inhibition of MK-801 induced hyperactivity and hypolocomotion in rats.

T-type calcium channel blockers: spiro-piperidine azetidines and azetidinones-optimization, design and synthesis.

A series of spiro-azetidines and azetidinones has been evaluated as novel blockers of the T-type calcium channel (Ca(V)3.2) which is a new therapeutic target for the potential treatment of both inflammatory and neuropathic pain. Confirmation and optimization of the potency, selectivity and DMPK properties of leads will be described.

Exebryl-1: A novel small molecule currently in human clinical trials as a disease-modifying drug for the treatment of Alzheimer's disease

injections of vehicle, CHF5074 (10 or 30 or 100 mg/kg) or DAPT (100 mg/ kg) 24 and 3 hours before the training session. Wild-type animals received vehicle, CHF5074 (100 mg/kg) or DAPT (100 mg/kg). Freezing was expressed as a percentage of time in each portion of the test in which the animal remained immobile (at least 95% of his body for at least 500 msec) and analyzed using two-way ANOVA (with transgene and treatments ad fixed factors) followed by the Holm-Sidak’s comparison procedure vs the vehicle-treated groups. Results: Compared to vehicle-treated wild-type mice, vehicle-treated transgenic animals had significantly lower freezing to the context (59.1 6 3.9% vs 77.5 6 2.6%, p < 0.001). CHF5074 showed a bell-shaped dose-response curve with a non-significant increase of the contextual freezing with the 10 mg/kg dose (66.1 6 3.6%, p 1⁄4 0.128), a significant improvement with 30 mg/kg (71.5 6 3.9%, p 1⁄4 0.008) and no effects with the highest dose of 100 mg/kg (58.1 6 4.6%). Compared to transgenic controls, DAPT 100 mg/kg had not effects on contextual freezing (55.6 6 5.8%). In wild-type mice, neither CHF5074 (100 mg/kg) nor DAPT (100 mg/kg) had effects on behavior compared to vehicle-treated animals. No significant effects of drug treatments were observed in hippocampal-independent cue conditioning. Conclusions: These data show that acute treatment with CHF5074 improves hippocampal-dependent memory in a transgenic mouse model of AD and support its development as potentially disease-modifying agent of AD.

SCH 2047069, a Novel Oral Kinesin Spindle Protein Inhibitor, Shows Single-Agent Antitumor Activity and Enhances the Efficacy of Chemotherapeutics

Kinesin spindle protein (KSP) is a mitotic kinesin required for the formation of the bipolar mitotic spindle, and inhibition of this motor protein results in mitotic arrest and cell death. KSP inhibitors show preclinical antitumor activity and are currently undergoing testing in clinical trials. These agents have been dosed intravenously using various dosing schedules. We sought to identify a KSP inhibitor that could be delivered orally and thus provide convenience of dosing as well as the ability to achieve more continuous exposure via the use of dose-dense administration. We discovered SCH 2047069, a potent KSP inhibitor with oral bioavailability across species and the ability to cross the blood-brain barrier. The compound induces mitotic arrest characterized by a monaster spindle and is associated with an increase in histone H3 and mitotic protein monoclonal 2 phosphorylation both in vitro and in vivo. SCH 2047069 showed antitumor activity in a variety of preclinical models as a single agent and in combination with paclitaxel, gemcitabine, or vincristine. Mol Cancer Ther; 9(11); 2993–3002. ©2010 AACR.

Isolation, structure elucidation and antibacterial activity of a new tetramic acid, ascosetin.

The ever-increasing bacterial resistance to clinical antibiotics is making many drugs ineffective and creating significant treatment gaps. This can be only circumvented by the discovery of antibiotics with new mechanisms of action. We report here the identification of a new tetramic acid, ascosetin, from an Ascomycete using the Staphylococcus aureus fitness test screening method. The structure was elucidated by spectroscopic methods including 2D NMR and HRMS. Relative stereochemistry was determined by ROESY and absolute configuration was deduced by comparative CD spectroscopy. Ascosetin inhibited bacterial growth with 2–16 μg ml−1 MIC values against Gram-positive strains including methicillin-resistant S. aureus. It also inhibited the growth of Haemophilus influenzae with a MIC value of 8 μg ml−1. It inhibited DNA, RNA, protein and lipid synthesis with similar IC50 values, suggesting a lack of specificity; however, it produced neither bacterial membrane nor red blood cell lysis. It showed selectivity for bacterial growth inhibition compared with fungal but not mammalian cells. The isolation, structure and biological activity of ascosetin have been detailed here.

An integrin antagonist (MK‐0429) decreases proteinuria and renal fibrosis in the ZSF1 rat diabetic nephropathy model

Multiple integrins have been implicated in modulating renal function. Modulation of integrin function can lead to pathophysiological processes associated with diabetic nephropathy such as alterations in the glomerular filtration barrier and kidney fibrosis. The complexity of these pathophysiological changes implies that multiple integrin subtypes might need to be targeted to ameliorate the progression of renal disease. To address this hypothesis, we investigated the effects of MK‐0429, a compound that was originally developed as an αvβ3 inhibitor for the treatment of osteoporosis, on renal function and fibrosis. We demonstrated that MK‐0429 is an equipotent pan‐inhibitor of multiple av integrins. MK‐0429 dose‐dependently inhibited podocyte motility and also suppressed TGF‐β‐induced fibrosis marker gene expression in kidney fibroblasts. Moreover, in the obese ZSF1 rat model of diabetic nephropathy, chronic treatment with MK‐0429 resulted in significant reduction in proteinuria, kidney fibrosis, and collagen accumulation. In summary, our results suggest that inhibition of multiple integrin subtypes might lead to meaningful impact on proteinuria and renal fibrosis in diabetic nephropathy.

Abstract 1648: SCH 1473759, a novel aurora inhibitor, demonstrates enhanced antitumor activity in combination with taxanes and KSP inhibitors

Aurora kinases are required for orderly progression of cells through mitosis. Inhibition of these kinases by siRNA or a small molecule inhibitors results in aberrant endoreduplication and cell death. SCH 1473759 is a novel Aurora inhibitor with potent mechanism based cell activity. The compound is active against a large panel of tumor cell lines from different tissue origin and genetic backgrounds. We found that asynchronous cells require 24 hour exposure to SCH 1473759 to induce maximal endoreduplication and cell kill. However, following a taxane or KSP inhibitor mitotic arrest, less than 4-hour exposure was sufficient to induce endoreduplication. This finding correlated with the ability of SCH 1473759 to accelerate exit from mitosis in response to taxane and KSP induced arrest, but not that of a nocodazole arrest. SCH 1473759 demonstrated single agent biomarker and anti-tumor activity in A2780 ovarian xenograft models. Further, efficacy was enhanced in combination with taxotere and found to be most efficacious when SCH 1473759 was dosed 12-hours post taxotere. These findings could have clinical implications for the development of Aurora inhibitors. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1648.