CHEM E-120 Harvard University Extension School Neurodegenerative Disorders Alzheimer’s Disease April 6, 2011 4/6/11 CHEM E-120

Alzheimer’s Disease Most prevalent of the neurodegenerative diseases Affects ~ 15-20 million individuals worldwide Age onset ~ 60 – 65 years, risk of developing Alzheimer’s doubles every 5 years after age 65 with a 50% chance after age 85. 8th leading cause of death Main clinical symptom is dementia early memory impairment episodic memory progressive decline in executive function – reasoning, etc drastic alterations in personality – aggressive behavior DSM-IV classifies several forms of dementia No diagnostic tool premortem except clinical dementia rating (CDR) Postmortem analysis is characterized by the identification of neurofibrillary tangles (NFT) and amyloid plaques. 4/6/11 CHEM E-120

Cholinergic Hypothesis - AD Based on finding reduced activity of choline acetyltransferase activity and loss of cholinergic neurons in the forebrain. Reduction in amount of acetylcholine. Cholinergic system appears important in cognitive function: attention, memory noncognitive function: depression, psychosis, aggression, sleep Acetylcholine (ACh) binds to muscarinic receptors and nicotinic (nAChR) Na+ channels. 4/6/11 CHEM E-120

Neurotransmitters - Acetylcholine mnemonic function neurofibrally tangles appear here first in early satge AD 4/6/11 CHEM E-120

2. M1 agonist (stimulates cognitive function) 3. NAChR agonists Loss of ACh How to increase it? 1. Inhibition of ACHE 2. M1 agonist (stimulates cognitive function) 3. NAChR agonists α4β2 agonist predominate NACh subunit in brain partial agonist Varenicline (7)5 agonist inc Ca2+ permeability agonist increase cognition 4. 5-HT1A antagonist increase ACh and glutamate Comprehensive Medicinal Chemistry II Chapter 6.08 4/6/11 CHEM E-120

Mediciation Development Alzheimer’s Disease 1. Acetylcholineesterase inhibitors (4 approved for use) Tacrine (Cognex) Donepezil (Aricept) Rivastigmine (Exelon) Galantamine (Razadyne, Reminyl) 2. NMDA noncompetitive antagonist (Approved) Memantine (Namenda) reduces Ca2+ influx into neurons, excess Ca2+ is cytotoxic 3. β-Secretase inhibitors 4. GSK-3 inhibitors (Annual Reports in Med. Chem. 2010, 44, 3 5. 5HT1A antagonists 4/6/11 CHEM E-120

Acetylcholinesterase Acetylcholinesterase (ACHE) is a serine esterase enzyme ACHE has an anionic binding site which attracts the positively charged quaternary ammonium group of ACH. A serine then attacks and cleaves the ester. This is an example of general base catalysis. 4/6/11 CHEM E-120

Phe297 Phe295 vs aliphatic in BChE catalytic triad Glu202 quat site van der Waals surface map of acetylcholine in active site of AChE inhibitor binding site Phe297 Phe295 vs aliphatic in BChE 4/6/11 catalytic triad CHEM E-120 Basic Neurochemistry p. 195 Glu202 quat site

Acta Biologica Hungarica 54 (2), pp. 183–189 (2003) 4/6/11 CHEM E-120

Donepezil - Aricept Approved in 1997 Annual Reports in Medicinal Chemistry 1998, 33, 332 Jpn. J. Pharmacol. 89, 7 – 20 (2002) 4/6/11 CHEM E-120

Discovery of Donepezil 1 found through random screening prepared about 700 analogs benzylpiperizine to benzylpiperidine replacement of ether 4 poor bioavailability and short duration of action Jpn. J. Pharmacol. 89, 7 – 20 (2002) 4/6/11 CHEM E-120

Discovery of Donepezil 7 replace amide by ketone 6 cyclic amide better inhibition than 5 leads to 8 IC50 less than 4 but longer duration of action SAR 4/6/11 CHEM E-120

Discovery of Donepezil ring size carbonyl 4/6/11 CHEM E-120

Discovery of Donepezil p-methoxy 4/6/11 CHEM E-120

Discovery of Donepezil 4/6/11 CHEM E-120

Discovery of Donepezil location and number of N’s 4/6/11 CHEM E-120

Discovery of Donepezil pKa! 4/6/11 CHEM E-120

Discovery of Donepezil Tacrine oral ID50 = 9.5 mg/kg oral ID50 = 2.6 mg/kg 4/6/11 CHEM E-120

Discovery of Donepezil move from light to dark chamber (foot shock) learn: avoid dark chamber no learning MS cholinergic projections to hippocampus equivalent to Meynert nucleus in humans 4/6/11 CHEM E-120

Discovery of Donepezil 4/6/11 CHEM E-120

Discovery of Donepezil Result of J-CGIC 4/6/11 CHEM E-120

Structure March 1999, 7:297–307 π-π stacking 4/6/11 CHEM E-120

Structure March 1999, 7:297–307 4/6/11 CHEM E-120

Amyloid Plaque Formation Insoluble, neurotoxic, protein clusters formed from Amyloid Precursor Protein (APP) 770 AA AA669 Asp C terminus intracellular N terminus extracellular BACE β-secretase Β-CFT AA669 AA770 γ-secretase AChE Aβ – β-amyloid1-40(42) fibril peripheral site of AChE 4/6/11 CHEM E-120

BACE Inhibitors 2-Amino-3,4-dihydroquinazolines High-throughput hit from a screen of their corporate compound collection J. Med. Chem. 2007, 50, 4261 Johnson & Johnson 4/6/11 CHEM E-120

BACE - 2-Amino-3,4-dihydroquinazolines First obtained a X-ray crystal of 1 bound to BACE-1 1 forms a U shaped conformation in active site 4/6/11 CHEM E-120

BACE - 2-Amino-3,4-dihydroquinazolines 4/6/11 CHEM E-120

5-HT1A Antagonists Lecozatan – Selective 5-HT1A Antagonist It has been suggested that the serotonergic system may be hyperactive in AD as a result of enhanced turnover of serotonin. This will ultimately result in the reduction of activity of cortical pathways by the binding of serotonin to autoreceptors on presynaptic neurons. It has been found that 5-HT1A antagonists can facilitate glutamatergic activity and cholinergic activity which leads to a reduction in cognitive deficits. The Potential Utility of 5-HT1A Receptor Antagonists in the Treatment of Cognitive Dysfunction Associated with Alzheimer’s Disease Current Pharmaceutical Design, 2002, 8, 139-145 Lecozatan – Selective 5-HT1A Antagonist 4/6/11 CHEM E-120

WAY100135 – Selective 5-HT1A Antagonist Arylpiperazines reported to be high-affinity 5-HT1A ligands (JMC 1988, 31, 1968) Eur. J. Pharmacol. 1988, 154, 339 In 1993 WAY100135 was reported as the first true selective antagonist of 5-HT1A Eur. J. Pharmacol. 1993, 237, 283 4/6/11 CHEM E-120

WAY100135 – Selective 5-HT1A Antagonist Evidence for presynaptic antagonist activity (autoreceptor) serotonin at 5-HT1A presynaptic inhibits firing Drug ID50 (μg/kg i.v.) 8-OH-DPAT (agonist) 1.9 BMY7378 (partial agonist) 12 NAN-190 (partial agonist) 16 MDL73005EF (“) 81 (±)WAY100135 >2500 (+)WAY100135 >600 (-)WAY100135 >1000 inhibitory effect serotonin is blocked 4/6/11 CHEM E-120

WAY100135 – Selective 5-HT1A Antagonist Evidence for presynaptic antagonist activity The 5-HT1A agonist 8-OH-DPAT induces hypothermia in mice. An antagonist should prevent this in a dose-dependent manner (±)WAY100135 ED50 = 2.0 mg/kg s.c. (+)WAY100135 ED50 = 1.5 mg/kg s.c. (-)WAY100135 ineffective up to 30 mg/kg 4/6/11 CHEM E-120

WAY100135 – Selective 5-HT1A Antagonist Evidence for postsynaptic antagonist activity 5-CT is a 5-HT1A agonist that: Inhibits the electrically stimulated contraction of muscle rightward shift that is indicative of antagonism 4/6/11 CHEM E-120

WAY100135 – Selective 5-HT1A Antagonist Evidence for postsynaptic antagonist activity (+) The 8-OH-DPAT syndrome Due to 5-HT activation Extended flat body posture Forepaw treading Hyperlocomotion (±) (-) 4/6/11 CHEM E-120

WAY100635 Drug IC50 (nM) pA2 (5-CT) ED50 (antag. Induced hypothermia) (±)WAY100135 34 7.2 2.5 mg/kg (+)WAY100135 15 (-)WAY100135 437 WAY100635 1.35 9.7 0.01 mg/kg >100 fold selective vs other 5-HT receptors and 35 other receptors/transporters Eur. J. Pharmacol. 1995, 281, 81-88 4/6/11 CHEM E-120

Lecozatan – Selective 5-HT1A Antagonist WAY-100635 lacked bioavailability. Modification of the amide portion and N-phenyl portion. 4/6/11 CHEM E-120

Lecozatan – Selective 5-HT1A Antagonist Though not the most potent in vitro antagonist, 11c showed most potency in vivo Rats trained to respond to fixed ratio-30 schedule of food presentation to receive a food pellet. Agonist 8-OH-DPAT reduces response rate. 4/6/11 CHEM E-120

Lecozatan – Selective 5-HT1A Antagonist J. Pharmacology and Experimental Therapeutics 2005, 314, 1274 4/6/11 CHEM E-120

Lecozatan – Selective 5-HT1A Antagonist In vivo microdialysis in conscious rats 4/6/11 CHEM E-120

Lecozatan – Selective 5-HT1A Antagonist Time dependent increase in glutamate levels in dentate gyrus by in vivo microdialysis 4/6/11 CHEM E-120

Lecozatan – Selective 5-HT1A Antagonist Time dependent increase in acetylcholine levels in hippocampus by in vivo microdialysis 4/6/11 CHEM E-120

Lecozatan – Selective 5-HT1A Antagonist 16% @ 1.0 mg/kg Lecozotan enhances cognitive function in the aged rhesus monkey as assessed by DMTS (delayed matching-to-sample) performance efficiency. 4/6/11 CHEM E-120

Lecozatan – Selective 5-HT1A Antagonist binding of 11C-WAY-100635 Nature Clinical Pharmacology and Therapeutics 2008, 83, 86 4/6/11 CHEM E-120

Lecozatan – Selective 5-HT1A Antagonist Study shows Lecozotan is readily absorbed into the brain and binds to 5-HT1A receptors regardless of age and is not affected by AD being present Nature Clinical pharmacology and Therapeutics 2008, 83, 86 4/6/11 CHEM E-120