Discovery and Development of Novel Small Molecule Inhibitors of Botulinum Neurotoxin A Terry Bowlin, Ph. D. Microbiotix, Inc. Worcester, MA October 29, 2008
Bo. NT Inhibitor Discovery MBX Overview Bo. NT Background Bo. NT Drug Discovery Bo. NT Assays October 29, 2008
MICROBIOTIX A small molecule, anti-infective drug discovery company Terry L. Bowlin, Ph. D. , CEO Worcester, MA October 29, 2008
Microbiotix Corporate Overview Ø Launched in January 2000 with offices and laboratories in Worcester, Massachusetts Ø Core antibiotics technology based on scientific founders’ research at U Mass on inhibition of bacterial DNA replication Ø 10, 739 sq. ft. of fully equipped office and microbiology and medicinal chemistry laboratory space Ø Fully integrated infectious disease microbiology and medicinal chemistry drug discovery capability Ø 25 employees with extensive experience in drug discovery and development Ø Active biodefense program for the discovery and development of novel antibacterial, antiviral and antivirulence factor therapeutics Ø Current preclinical pipeline of novel anti-bacterial and anti-herpes inhibitor October 29, 2008
Microbiotix Discovery Platform Proprietary Screens: Ø Enzyme based Ø Ø Cell based Ø Ø Ø permeabilized bacterial replication screen whole-cell target-based luciferase reporter screens Biofilm Ø Ø purified enzymes essential for replication (e. g. , polymerase, gyrase, topoisomerase, helicase) HTS for identification of biofilm inhibitors Types of readouts Ø UV/Vis absorbancy, fluorescence, FRET, time-resolved FRET, luminescence, radioisotopic Lodish et al. 2003. Molecular Medicinal Chemistry: Cell Biology, 5 th ed. Ø Fully integrated medicinal chemistry drug discovery unit Compound Library: Ø Greater than 100 K compounds with greater than 200 druglike chemotypes October 29, 2008
Microbiotix Anti-Infective Drug Discovery Compound Libraries (Drug-like compounds & natural products) • MBX 500 • MBX 222 HTS & Confirmation Lead Identification • Medicinal Chemistry • IC 50 & MIC criteria • Serum effect • In vitro therapeutic index criteria • Confirmed SAR • MOA confirmation • Freedom to operate • Biochemical Screens • Cell-Based Screens • Re-tested in quadruplicate Confirmed Hits Validated Hits • Secondary Assays • IC 50 & MIC criteria • In vitro therapeutic index criteria • QC & stability Hit Validation In Licensing • MBX 1107 (USAMRIID) • MBX 400 (Wayne St. U. ) October 29, 2008 Lead Compounds Lead Optimization • Ranked by criteria • Low resistance freq. • Passed acute tox • Effective in animals • Scalable synthesis • Patentable • Satisfactory market Preclinical Candidates • MBX 500 • MBX 400
Microbiotix Drug Discovery Portfolio PROJECT THERAPEUTIC TARGET MOLECULAR TARGET STATUS MBX-500 Gram +; MRSA/VRE Polymerase; Gyrase/Topoisomerase Pre-clinical IND enabling MBX-1162 Broad Spectrum Antibiotic (biodefense) DNA/Helicase Pre-clinical IND enabling MBX-1131 C. botulinum (biodefense) Bo. NT /A LC SAR MBX-400 Anti-beta/gamma Herpes; (HCMV/HHV 6/HHV 8) Polymerase Preclinical INDenabling MBX-222 Ebo. V (biodefense) Fusion Hit/lead MBX-1325 HCV Polymerase Hit/lead ANTI-BACTERIAL ANTI-VIRAL October 29, 2008
Bo. NT Inhibitor Discovery MBX Overview Bo. NT Background Bo. NT Drug Discovery Bo. NT Assays October 29, 2008
October 29, 2008
Bo. NT Medical Uses Ø Ø Ø Ø Cosmetic (Wrinkles, etc. ) Dystonia (Muscle Contraction) Hyperhidrosis(Excess Sweating) Strabismus(Crossed Eyed) Blepharospasm(Excessive Blinking) Back Pain Migraine (Tension Headaches) Incontinence October 29, 2008
October 29, 2008
The Bo. NT Threat Ø Botulinum neurotoxins (Bo. NTs) are the most potent of the biological toxins Ø Of the botulinum neurotoxins, Bo. NT/A is the most potent (lethal dose 1 ng/kg) Ø Due to their lethality, Bo. NTs are listed as category A (highest priority) biothreat agents by the CDC Ø Bo. NTs are easily produced and may be delivered by aerosol route Ø Consequently, these toxins represent a serious threat to both military personnel and civilians October 29, 2008
Bo. NT Serotypes Ø Bo. NT secreted by the anaerobic spore-forming bacterial Clostridia species ØSeven Bo. NT serotypes exists (A-G), which differ significantly in amino acid sequence, protein substrates, and substrate cleavage sites Ø Significant differences in the duration of the paralysis caused by each October 29, 2008
Bo. NT Mediated Paralysis v Significant differences in the duration of the paralysis caused by each serotype: Ø Bo. NT/A paralysis lasts the longest, typically 4 -6 months, and this is a primary reason why it has become popular for both medicinal and cosmetic applications Ø The duration of paralysis from Bo. NT/A coupled with its potency and the fact that several high resolution crystal structures are available have made it possibly the most tractable and relevant for immediate drug discovery efforts October 29, 2008
October 29, 2008
Bo. NT Substrate Ø Once inhaled into the lung, Bo. NTs are taken up by the blood stream, target the peripheral cholinergic nerve endings, and cause death by interrupting autonomic nerve function Ø The zinc-dependent endopeptidase light chain (LC) portion of Bo. NTs impair neuronal exocytosis through proteolysis of essential SNARE (soluble NSFethylmaleimide-sensitive factor attachment protein receptor) components of neurotransmission October 29, 2008
1. Binding 2. Internaliza tion 3. Transloca tion (LC release) 4. Proteolyti c Cleavage SNARE complex October 29, 2008
Therapeutic Approaches to Bo. NT Inhibition Therapeutic Anti-Bo. NT MAbs Receptor decoys HC inhibitors Efficacy Effective in mice (in vivo toxin neutralization when premixed with Bo. NT/A prior to injection) Limitations 3 MAbs required (oligoclonal) for adequate potency; limited postexposure utility Effective in nerve assays when Co-administration of gangliosides premixed prior to contact required; limited post-exposure utility Effective in isolated mouse Mechanism unclear; associated diaphragm muscle twitch model cytotoxicity of anti-malarials; no post-exposure protection LC inhibitors – peptides Efficacy demonstrated in vitro only Non drug-like molecules with poor ADME features LC inhibitors – small molecules Efficacy in vitro, & in neuronal cell culture or synaptosomes Higher potency with suitable ADME properties needed October 29, 2008
Bo. NT Current Treatment Ø The currently available Bo. NT toxoid vaccine, as well as experimental preventative antibodies, cannot counter these toxins after they penetrate neurons Ø Critical care mechanical ventilation is the only treatment option once neurons have been intoxicated and diaphragm muscles cease to function Ø The effects of internalized Bo. NTs can last for months (6), and longterm mechanical ventilation would be impractical if even a limited number of individuals were simultaneously intoxicated Ø Therefore, there is an urgent need to identify and develop low molecular weight non-peptidic inhibitors that will serve as both prophylactics and post-exposure ‘rescue’ therapeutics October 29, 2008
Bo. NT Inhibitor Discovery MBX Overview Bo. NT Background Bo. NT/A Inhibitor Drug Discovery Assays/Results October 29, 2008
Bo. NT Drug Discovery Ø Due to the lethality and difficulty of treating intoxication with Bo. NTs, new small-molecule inhibitors of these toxins are critically needed. Ø We have identified a new series of Bo. NT/A inhibitors with potency in both enzyme and cellbased primary neuronal assays. October 29, 2008
Compound Evaluation Flow Chart October 29, 2008
Bo. NT Biological Assays Ø FRET Assays Ø HPLC Assay Ø Neuronal Cell Assays October 29, 2008
Enzyme Based Assays Fluoresence Resonance Energy Transfer (FRET) Standard Assay For Recombinant Bo. NT Lc. A (DACIA SUBSTRATE) For Characterization of MBX Compounds REAGENT [STOCK] QUANTITY ( L) [FINAL] DMSO or Compound 100 % 1 1% Sterile Water 55 M 44 N/A HEPES p. H 7. 4 200 m. M 25 50 m. M Tween 20 0. 5% 10 0. 05% Bon. T Lc. A 1 g/m. L 10 10 ng in rxn DACIA Substrate 200 M 10 20 M Incubate at 37°C for 40 minutes. Monitor Ex 398 nm Em 485 nm every minute for kinetic measurement. At the end of 40 minutes, stop reactions with 10 µL 5% Acetic Acid. Read Ex 398 nm Em 485 nm in endpoint mode. Alternative Assay For Recombinant Bo. NT Lc. A (FITC SUBSTRATE) For Characterization of MBX Compounds REAGENT [STOCK] QUANTITY ( L) [FINAL] DMSO or Compound 100 % 1 1% Sterile Water 55 M 34 N/A HEPES p. H 8. 2 200 m. M 25 50 m. M Tween 20 0. 5% 20 0. 1% Bon. T Lc. A 1 g/m. L 10 10 ng in rxn FITC Substrate 100 M 10 10 M Incubate at 37°C for 60 minutes. Monitor Ex 490 nm Em 523 nm every minute for kinetic measurement. At the end of 60 minutes, stop reactions with 10 µL 500 m. M EDTA p. H 8. 0. Read Ex 490 nm Em 523 nm in endpoint mode. October 29, 2008
October 29, 2008
Detection Method for Bo. NT Lc. A FRET (DACIA) Assay D 1 E 1 October 29, 2008 HEAT DENATURED Bo. NT Lc. A CONTROL 10 ng Bo. NT Lc. A
Enzyme Based Assay-HPLC REAGENT DMSO or Compound Sterile Water HEPES p. H 7. 4 NP-40 Bo. NT Lc. A Substrate (DACIA) [STOCK] 100% 55 M 200 m. M 0. 5% 1 g/m. L 2 m. M QUANTITY ( L) 1. 5 46 38 15 45 4. 5 [FINAL] 1% N/A 50 m. M 0. 05% 45 ng in rxn 60 M Incubate at 37°C for 40 minutes. At the end of 40 minutes, stop reactions with 15 µL 5% Acetic Acid. Read Ex 398 nm Em 485 nm in endpoint mode. HPLC Conditions Solvent A: 0. 1% TFA Solvent B: 0. 1% TFA in 70% Acetonitrile Inject 100 µl sample Gradient: 35% B to 40% B over 21 min, 100% for 10 min Monitor effluent at 365 nm October 29, 2008
Detection Method for Bo. NT Lc. A HPLC Assay Heat Denatured Bo. NT Lc. A Reaction Native Bo. NT Lc. A Reaction October 29, 2008
Compound Library 20, 000 cpds 50, 000 cpds Maybridge & Microsource Discovery Chembridge DIVERSet. TM HTS Screening Library 100, 000 Cpds ~200 chemotypes 3, 770 cpds, natural products & derivatives Analyti. Con Discovery October 29, 2008 Chemical Filters: To include: • ~200 -500 Da • Lipinski “rule of 5” To exclude: • Cytotoxic fragments • Metal complexes • Highly conjugated ring systems • Oxime esters • Nitroso groups • Strong Michaelson acceptors 30, 000 cpds GLSynthesis, MBX, & other sources
Ongoing HTS at Microbiotix Libraries Screened: Ø Tim Tec Natural Products Ø Chembridge 50 K Ø Chem Div 2 Number of Compounds Screened Number of Number Primary Hits Confirmed via FRET Assay % Final Confirmed Hit Rate: FRET + Ongoing HPLC Secondary Assays 70, 400 330 0. 16 114 Typical Z’ Score=0. 69 October 29, 2008
Examples of Select Screening Hits ID IC 50 (µM) FRET IC 50 (µM) HPLC CB 6346186 16 58 CB 7620237 24 88 CB 6352178 5. 92 35 CB 7662532 31 72 CB 6696465 33 78 CB 7725216 10 27 CB 6698977 19 78 CB 7738585 16 >100 CB 7774777 39 ND CB 7869065 10 14 CB 7781727 38 ND CB 7853216 7. 15 10 CB 7785416 18 61 CB 7898734 8. 22 13 CB 7836164 13 59 CB 7924532 15 12 October 29, 2008
USAMRIID HTS Bo. NT/A LC Inhibitors Structure Compound ID % Inhibition NSC 661, 755 Q 2 -61 50% NSC 357, 756 57% Q 2 -15 60% NSC 119, 889 October 29, 2008 62% 56% Q 2 -43 52%
October 29, 2008
The Bo. NT/A LC pseudo-peptide inhibitor Mpp-RATKML (Ki=330 n. M) docked within the Bo. NT/A LC substrate binding cleft (Burnett et al, JBC, 2007, 282: 5004 -14) October 29, 2008
Refined Pharmacophore for Bo. NT/A LC Inhibition A Planar Components: A&B Hydrophobic Components: C&D Positive Ionizable Component: E October 29, 2008
New Bo. NT/A LC Inhibitors: Potencies, Search Query Fits and Distances Between Components October 29, 2008
Chick Neuronal Cell Assay 1) Embryonic chicken spinal motor neuron cells were isolated utilizing methods described by Kuhn 2) Neuronal cell cultures were incubated overnight at 37°C prior to Bo. NT/A intoxication 3) Cells were pre-incubated with inhibitor for 45 min, followed by 3. 5 hour incubation with 10 n. M Bo. NT/A and inhibitor 4) Cells were then lysed 5) Lysates were run on a 12% gel and transferred to nitrocellulose 6) Blots were probed with SMI 81 mouse anti-SNAP-25 primary antibody, followed by probing with horseradish peroxidase-conjugated goat anti-mouse secondary antibody in combination with ECL Western blotting detection system 7) Developed blot is analyzed via densitometry (UN-SCAN-IT gel automated digitizing system) Burnett et al. (2007) J. Biol. Chem. 282, 5004 -5014 Kuhn, T. B. (2003) Methods Cell Biol. 71, 67 -87 October 29, 2008
Chick Neuronal Cell Morphological Analysis Green=staining for tubulin Red=staining for actin filaments Blue=staining for DNA October 29, 2008 NSC 240898 is well tolerated by neurons and is an effective inhibitor of Bo. NT/A LC-mediated cleavage of SNAP-25 in cells
SNAP-25 Western Blot Analysis Chick Primary Neuronal Cells October 29, 2008
Analysis of Hit NSC 240898 Neuron uptake Ø Bo. NT/A LC inhibition: 61%@20 µM Ø CC 50 > 40 µM Ø NSC 240898 MBX-1131 Optimization Type I analogs Three-ring scaffold October 29, 2008 Type II analogs Two-ring scaffold
Docking Analysis 2, 4 -dichlorocinnamic hydroxamate October 29, 2008 MBX-1107
Bo. NT SAR: Summary Ø Basic substituents at R are required for Bo. NT Lc. A inhibitory activity Ø Basic substituents at R’ increase activity further Ø Small substituents on indole N are tolerated Ø Heteroatoms Y decrease Bo. NT activity Ø Small substituents such as F, Cl at R’’ are tolerated Ø Substitution of the phenoxy group with indole maintains potency October 29, 2008
Structures of Bo. NT/A Inhibitors MBX 1131 (NSC 240898) MBX 1107 MBX 1130 MBX 1140 MBX 1195 MBX 1340 MBX 1341 October 29, 2008
Enzyme Specificity of Select Bo. NT Lc. A Inhibitors IC 50 (µM) MBX ID Bo. NT/A Fluorescence Assay Bo. NT/A HPLC Assay Bo. NT/B HPLC Assay AT LF MMP-1 MMP-9 1131 16. 5 11 21 17 >100 11 1107 12. 5 9. 4 >100 43 >100 24 1130 15 8. 9 26 5. 5 >100 < 25 1140 1. 35 0. 84 8. 1 0. 83 >100 35 1195 IND 2. 7 4. 4 3. 9 ND ND 1340 4. 4 2. 8 ND ND 1341 2. 8 3. 2 ND ND AT LF, Bacillus anthracis lethal factor; MMP, human Matrix Metalloprotease; IND, Indeterminate due to autofluorescence or quenching of the compound; ND, Not determined October 29, 2008
Bo. NT Lc. A Enzymatic Activity ØThe original lead NSC 240898 was resynthesized (MBX 1131) and demonstrated to be as potent as it was in the original screen, with an IC 50 of 16. 5 µM ØMBX 1107, a structural analog of MBX 1131, is as potent as MBX 1131 in the enzymatic (FRET and HPLC) assays ØMBX 1107 shows greater specificity for Bo. NT Lc. A than does MBX 1131 in assays for related metalloproteases (Bo. NT Lc. B, anthrax lethal factor and human MMPs) ØCompounds MBX 1130, 1140, 1196, 1340 and 1341, with related but distinct bis-(indole) structures, are the most potent Bo. NT Lc. A enzyme inhibitors we have synthesized to date, with MBX 1140 displaying a 10 -fold increase in potency over MBX 1131 and 1107 October 29, 2008
Rat Neuronal Cell Assay 1) Cells are harvested from 7 -8 day old rat cerebella, washed and cultured in 6 well plates (>7 days) 2) Once the cells have become networked, they are preincubated (15 min. ) with test compounds or diluent (DMSO) 3) Cells are inoculated with Bo. NT/A and incubated for 3 hrs (37 °C) 4) Cells are treated with 1 M Na. OH, to inactivate the Bo. NT and lysed. 5) Samples are run on SDS-PAGE gels and transferred to membranes for immunoblot analysis with rabbit anti-SNAP-25 and HRP-conjugated goat antirabbit Ig. G 6) Band intensities are read and normalized using scanning densitometry October 29, 2008
Inhibition of Bo. NT/A Activity in Primary Rat Neurons by MBX Compounds at 80 µM MBX Compounds (80 m. M) Control Bo. NT/A 1130 1107 1131 1195 1340 1341 Uncleaved Cleaved 120 Rel. Int. SNAP 25 (%) 100 80 60 40 20 0 MBX compounds (80 µM) October 29, 2008 1195
Dose-dependent Inhibition of Bo. NT/A Activity in Primary Rat Neurons by MBX 1131 (µM) Control Uncleaved Cleaved October 29, 2008 Bo. NT/A 100 50 25 12. 5
October 29, 2008
Bo. NT/A Inhibitor Cell-Based Results ØMBX 1131 is the most potent of the Microbiotix Bo. NT/A inhibitors in the rat neuronal SNAP-25 cleavage assay, followed by MBX 1140. MBX 1107 has very little activity in this assay. Ø Compounds MBX 1195, 1340 and 1341 appear to have activity at a single concentration of 80 µM. October 29, 2008
Bo. NT/A LC Inhibitor Status Ø Over 100 compounds have been made and tested Ø Established a Bo. NT/A LC fluorescent based assay for HTS (Z’ factor > 0. 8) Ø Established a Bo. NT/A LC HPLC assay Ø Established MMP 1, 2, 3 and 9 assays; anthrax LF Ø Established cytotoxicity assays: He. La, MRC-5, HFF Ø Bo. NT/B LC assay is being developed Ø Compound profiling in secondary assays in progress Co-Crystallography Studies are under way Ø October 29, 2008
Bo. NT/A Inhibitor Summary Ø Ø Ø All 7 compounds exhibited potency in the enzyme assays of 1 -17 µM, with varying degrees of specificity, when tested against other metalloproteases MBX 1140 was the most potent compound in the series In the cell-based assay, MBX 1131 (NSC 240898) and 1140 displayed the greatest potencies (IC 50 = 40 µM and 70 µM, respectively) October 29, 2008
Bo. NT/A Inhibitor Conclusions The new series of compounds, based on MBX 1131 (NSC 240898), show promise for the treatment of lethal Bo. NT/A intoxication. October 29, 2008
October 29, 2008
Acknowledgements USAMRIID: Sina Bavari, Ph. D. Rekha Panchal, Ph. D. James Burnett, Ph. D. NCI: Rick Gussio, Ph. D. Tufts Vetinary School: John Beak-Park, Ph. D. Microbiotix – Biology: Don Moir, Ph. D. , CSO Michelle M. Butler, Ph. D. , Steven Cardinale, MS Arnab Basu, Ph. D. , Joselynn Wallace, BS Microbiotix - Medicinal Chemistry: Norton P. Peet, Ph. D. , Director of Chemistry John D. Williams, Ph. D. Bing Li, Ph. D. , Ramdas Pai, MS Shen Gu, Ph. D. NIAID – 5 U 01 AI 070430 -02 October 29, 2008
October 29, 2008
Скачать презентацию Discovery and Development of Novel Small Molecule Inhibitors
56a543a81cf1a0917c1884c5dd3ed194.ppt