Download - Alzheimer's Disease Final Presentation
Neuro Group: Discovery of new secretase inhibitor drug leads for
neurodegeneration and Alzheimer's disease. Mission Statement & Timeline
Dorothy Du, Cathy Hutchinson and Melissa McCoy
Advisor: Gilbert Rishton, PhD
Mission Statement
• To address the unmet medical need in Alzheimer's disease by the discovery and development of safe and effective drug leads and, ultimately, to help bring new mechanism-based medicines to the Alzheimer's disease patient population.
Discovery• Alzheimer’s disease introduction
– Disease history and outlook, market analysis of current treatments on the market and in development (i.e. gamma-secretase inhibitors, Amyloid specific mAb, ect.), pro’s/con’s of current treatments and need for more drug development
• Neurodegeneration• What causes it in AD? What is the hypothesized disease pathway and
what factors are still not well understood?• APP, β-secretase, and A plaques
• Secretase inhibitor design from APP structure– Gil’s example of small molecule drug design
• Biochemical screening– Model Systems for testing efficacy (i.e. transfected cell lines, transgenic
mouse model of AD, ELISA for detecting Beta Amyloid levels)– Methods for screening blood-brain barrier permeability (computational,
in vivo, and in vitro methods)
Figure 1 – Actual and estimated number of new AD cases in the US through 2050
Figure 2- Actual and estimated costs of AD in the US. Purple bars =Medicare costs, Yellowbars=Medicaid cost
Mount, Claire & Downton, Christian. Nature Medicine. 12, 780-784 (2006)
Disease Outlook
Drug Company Mechanism IndicationAricept (donepezil)
Eisai/ Pfizer AChE inhibitor Mild to moderate AD
Exelon (rivastigmine)
Novartis AchE inhibitor Mild to moderate AD
Razadyne (galantamine)
Johnson and Johnson
AchE inhibitor Mild to moderate AD
Namenda/ Ebixa (memantine)
Lundbeck/ Forest NMDA receptor antagonist
Moderate to severe AD
Current Treatment Market
Figure 3- Existing and forecasted Alzheimer’s disease treatment marketMount, Claire & Downton, Christian. Nature Medicine. 12, 780-784 (2006)
APP and β-Secretase• APP= Amyloid Precursor Protein
– Genetic link in Alzheimer’s Disease
• Protein is cleaved by enzymes known as secretases
– 3 types: α-secretase, β-secretase, and γ-secretase– Cleave the protein at different positions
Familial Alzheimer’s Disease Sporadic Alzheimer’s Disease
Mutations in APP/Presenilin genes
Genetic risk factors:ApoE4, other genes? Aging & environmental
Life-long increase in Aβ42 production Failure of Aβ clearance, gradual increasing levels
Aβ accumulation and oligomerization
Aβ oligomers subtly effect synapses
Aβ oligomers form plaques
Immune cell activation/ inflammation
Oxidative stress/ altered ion flow
Neuron dysfunction/transmitter deficits
Dementia
Amyloid Cascade Hypothesis
Blennhow, Kaj et al. The Lancet. 368 (2006)
Normal Tau Protein
Abnormally hyperphosphorylated tau
Kinases Phosphatases
Sequestration of MAPs and tau by hyperphosphorylated tau
Tau polymerization
NFT formation
Microtubule disassembly
Disturbed axonal flow/transport
Dementia
Neuronal dysfunction
Neuronal Death
Tau Protein in Alzheimer’s Disease
Blennhow, Kaj et al. The Lancet. 368 (2006)
Potential Drug Targets of AD
Journal of Pharmacology And Experimental Therapeutics Fast Forward First published on November 25, 2002; DOI: 10.1124/jpet.102.035840
Link Between Amyloid Hypothesis and Tau Protein
Journal of Pharmacology And Experimental Therapeutics Fast Forward First published on November 25, 2002; DOI: 10.1124/jpet.102.035840
Competitive LandscapeDrug Target/Mechanism Company Stage of Development
β-secretase inhibitor Amgen, Bristol-Meyer Squibbs, Elan Pharmaceuticals, Scios Inc, GlaxoSmithKline
Pre-clinical
γ-secretase inhibitors or modulators
Eli Lilly, Myriad Pharmaceuticals
Phase II/III
Aβ immunotherapy Elan Pharmaceuticals, Baxter Healthcare, Wyeth
Phase I, II and III
Aβ fibrillization inhibitors Neurochem, Prana Biotechnology
Phase II/III
CDK5/GSK-3β inhibitors UCSB Pre-clinical
Anti-inflammatory drugs Proctor & Gamble, Roche Phase III
Cholesterol lowering drugs Pfizer Phase II
http://www.alzforum.org
Why Target β-secretase?
• Plays a crucial role in the first step of the amyloid cascade
• Mice missing the β-secrectase gene are normal and cannot produce Aβ
• The enzyme is an aspartic protease similar to the HIV protease for which successful inhibitors have already been produced
Biochemical Screening
• Biochemical Assay– Kinetic measurements-
determines how potent the inhibitor is
– β-Secretase FRET Assay ( Fluorescence Resonance
Energy Transfer) Inhibition of β-secretase by a Statine-derived Inhibitor.
http://www.invitrogen.com/content/sfs/manuals/L0724.pdf
Biochemical Screening• Functional Activity Assays
– Utilize in vivo modelsystem:
• Transfected cell line• Transgenic mouse• Both produce excess Aβ
– Detect levels of Aβ in cell lysate or brain tissue
• Utilize immuno-assays• Western Blot, ELISA,
Immunoprecipitation
Rational Methods
• Medicinal Chemistry• X-ray Crystallography, Co-crystallization• Assay Development
– Enzyme Assay Development to measure pharmacokinetics of drug leads
– Need to measure initial velocity of reaction, Km and Vmax with selected substrates
– Determine IC50 and Ki for inhibitors (used to determine how good the inhibitor is at inhibiting the enzyme and what type of inhibition is occuring)
– Assay would be an In vitro system that measures the ability of the drug lead to inhibit secretase
Assay Development
• Biochemical Screening• Blood Brain Barrier Permeability (BBB)
– In vivo (transgenic mice) and in vitro (artificial membranes) approaches
– Computational approaches
• Other important Factors to Consider:– Pharmacokinetics-metabolic stability, metabolic liability,
permeability, protein binding– ADME- Absorption, Distribution, Metabolism and Excretion– Toxicology- will need to be outsourced
Literature
• Patent search– Lead molecules, composition-of-matter patents
• Novelty, new intellectual property• Building cost at CSUCI
Patent• Provisional patent
– Specific claims, composition-of-matter, use, function
– Structure, structure-activity-relationship– New drug lead, secretase inhibitor
• IP: Develop intellectual property position– Provisional patents– PCT patents
Development
• Facilitate development by attention to quality in discovery stage– Leadlike, druglike, low MW, oral bioavailability,
blood-brain barrier permeability• Facilitate development by partnering
– Use contract development labs for in vivo work.– Partner with a drug company for clinical
development
Characteristics of a Good Lead
Pajouhesh, Hassan et al. NeuroRx. 2, 541-553. (2005)