1. 1 Disorders of Mood and Behavior Schizophrenia Antipsychotic Drugs 3/9/2011 CHEM E-120 Harvard University Extension School 3/9/11CHEM E-120

2. 2 Schziophrenia 1. Two or more for a one month period Delusions Hallucinations Disorganized speech Grossly disorganized or catatonic behavior Continuous symptoms must persist for 6 months Three domains Positive Symptoms: excess or distortion of normal function (psychosis) Negative Symptoms: decrease or loss of normal function (social withdrawal) Cognitive Impairment: information processing 3/9/11CHEM E-120

3. 3 Neurochemical Hypotheses of Schizophrenia Dopamine Hyperfunction Hypothesis Hyperactivity of the dopaminergic system in the forebrain increases levels of dopamine. Proposed based on the observation that antipsychotic drugs tend to bind to D 2 receptor as antagonists or inverse agonists. Serotonin (5HT) Hypothesis Decrease in serotonin function, 5HT 2a antagonist/inverse agonist Clozapine Hypothesis: mixed levels of D 2 /5HT 2 /H 1 /M 1 /adrenergic activity Glutamate Hypofunction Hypothesis: NMDA blockade, decreased activation of NMDA receptors GABA Hypothesis: GABAergic system appears perturbed, lower levels of GABA reuptake sites 3/9/11CHEM E-120

4. 4 Neurotransmitters - Dopamine 1/27/2010 2 families of dopamine binding receptors D 1 -likeincrease cAMP, increased concentration in prefrontal cortex schizophrenia D 1 caudate/putamen, NuAcc, cerebral cortex D 5 located in hippocampus, hypothalamus, cerebral cortex very high affinity for dopamine reduced agonist induced locomotion, startle, and prepulse inhibition D 2 -likedecrease cAMP, open K + channels, close Ca 2+ channels D 2 caudate/putamen, NuAcc knockout mice parkinsonian-like motor impairment D 3 hypothalamus D 4 frontal cortex, NuAcc knockout mice hypersensitive to ethanol and stimulants

5. CHEM E-1205 Neurotransmitters - Serotonin Binds to the serotonin receptors and transporter Important in depression, anxiety, and schizophrenia 3 main families 5-HT 1 - GPCR, 5 subtypes (A, B, D, E, F) have 40-60% sequence homology, inhibit adenylyl cyclase 5-HT 1A – cortical and limbic structures, presynaptic (autoreceptors) and postsynaptic 5-HT 2 - GPCR, 3 subtypes (A, B, C) have 45-50% sequence homology, stimulate phospholipase C 5-HT 2A – frontal cortex, parts of limbic system, site of action of hallucinogenic drugs 5-HT 2C – limbic system and motor system, site of action of hallucinogenic drugs 5-HT 3 - ligand-gated ion channel, 6 subtypes, stimulate adenylyl cyclase 1/27/2010

6. 6 Antipsychotic Drugs First generation antipsychotics (FGA) introduced 1955. Tend to be D2 antagonists Chlorpromazine (Thorazine) Second generation antipsychotics (SGA, atypical antipsychotics) D 2 antagonist/5-HT 2a antagonist Haloperidol Clozapine (Clozaril) Olanzapine (Zyprexa) Quetiapine (Seroquel) Risperidone (Risperdal) Antipsychotics are atypical when their 5-HT 2A antagonism superimposed on D 2 antagonism reduces D 2 binding of the drug enough to reverse motor side effects but not enough to reverse antipsychotic effects. New drugs: Aripiprazole - partial agonist 3/9/11CHEM E-120

7. 7 VTA Am HYPTh HC Thalumus PutamenNuAcc Dopamine Serotonin Norepinephrine Cortex Raphe nuclei Locus coeruleus Schizophrenia Neurocircuitary 3/9/11CHEM E-120 SN A9 - Substantia nigra - extrapyramidal nigrostriatal pathway A10 – Ventral tegmental areamesolimbic pathway (positive symptoms) mesocortical pathway (negative symptoms) Caudate nucleus striatum: caudate nucleus (cognition), putamen (motor), nucleus accumbens HC - hippocampus

8. 8 Modified Dopamine Hypothesis Normal State Brainstem dopaminergic neurons Ventral tegmantal area (A10) Limbic area striatum Prefrontal cortex Mesolimbic systemMesocortical system Negative feedback inhibitory Kandel p 1205 3/9/11CHEM E-120

9. 9 Modified Dopamine Hypothesis - Schizophrenic State Brainstem dopaminergic neurons Ventral tegmantal area (A10) Limbic area (striatum) Increase in activity Increase in dopamine levels Produces Positive symptoms (psychosis) Prefrontal cortex Decreased activity Reduction in dopamine levels D 1 highly expressed Produces Negative symptoms Mesolimbic systemMesocortical system disrupted Loss of negative feedback 3/9/11CHEM E-120

10. 10 Modified Dopamine Hypothesis Schizophrenic State and EPS (side effect) Limbic area + striatum Increase in activity Increase in dopamine levels, high expression levels of D 2, D 3, and D 4 Positive symptoms Mesolimbic system A10 Nigrostriatal system motor control side effects D 2 antagonists cause EPS EPS – extrapyramidal syndrome (involuntary movements, muscular rigidity) VTA (A10)SN (A9) 3/9/11CHEM E-120

11. 11 Serotonin - Dopamine Hypothesis - Schizophrenic State Brainstem dopaminergic neurons Limbic area (striatum) Increase in activity Increase in dopamine levels Positive symptoms Prefrontal cortex Decreased activity Reduction in dopamine levels Negative symptoms Mesolimbic system Mesocortical system disrupted Raphe nuclei 5-HT 3/9/11CHEM E-120

12. 12 Substantia nigra (A9) Limbic area + striatum  dopamine levels 5-HT 2A antagonist dec dopamine (A10) 5-HT 2c antagonist inc dopamine Prefrontal cortex (  dopamine) 5-HT 2A antagonist  DA 5-HT 1A agonist  DA 5-HT 2C antagonist  DA CNS Drugs 2006, 20, 389 Raphe nuclei 5-HT Modulation of 5-HT 2A, 5-HT 1A, or 5-HT 2C alone have no antipsychotic effectt Serotonin - Dopamine Hypothesis - Schizophrenic State 3/9/11CHEM E-120 5-HT 1A agonist (inhibit neuron, activating dopamine neurons, dec EPS) 5-HT 2A antagonist (disinhibits dopaminergic neuron, increased dopamine binds to D2 preventing binding of drug antagonists, thereby dec EPS)

13. 13 Antipsychotic Drugs First generation antipsychotics (FGA) introduced 1955. Tend to be D2 antagonists Chlorpromazine (Thorazine) Second generation antipsychotics (SGA, atypical antipsychotics) D 2 antagonist/5-HT 2a antagonist Haloperidol Clozapine (Clozaril) Olanzapine (Zyprexa) Quetiapine (Seroquel) Risperidone (Risperdal) Antipsychotics are atypical when their 5-HT 2A antagonism superimposed on D 2 antagonism reduces D 2 binding of the drug enough to reverse motor side effects but not enough to reverse antipsychotic effects. New drugs: Aripiprazole - partial agonist 3/9/11CHEM E-120

14. 14 D 2 occupancy Theory - drugs compete with dopamine for D 2 sites, ideal antipsychotic efficacy w/o EPS achieved by < 80% occupancy and fast dissociation Drug + D 2 [Drug][D 2 ] (therapeutic effect) DA + D 2 [DA][D 2 ] (EPS effect) ~ 40% occupancy Major side-effect of FGA is extrapyramidal effects (Parkinson-type effects) due to D 2 antagonism. D 2 high and D 2 low states have been proposed where D 2 high is a high affinity state of the D 2 receptor. Suggested an elevation of D 2 high occurs leading to hypersensitivity to dopamine. 3/9/11CHEM E-120

15. 15 First Generation Antipsychotics ImipramineChlorpromazine 5-HT1pIC 50 ~ 4-55.5 5-HT26.58 α15.55.5 (antagonist) α27 (antagonist)7.8 (antagonist) DA4-55.5 (antagonist) D2-like7.5 H17.5 (antagonist)8 Muscarinc7 (M2 antagonist)7 Naunyn-Schmiedeberg’s Arch Pharmacol 1984, 327, 95 3/9/11CHEM E-120

16. 16 Structures of FGA/SGA Antipsychotic FGA D 2 potency SGA benzazepines - Similar D 2 (efficacy) + 5-HT 2A (efficacy/reduce EPS) 3/9/11CHEM E-120

17. 17 Clozapine Introduced in 1972 Withdrawn in 1975 (agranulocytosis, loss of white blood cells) Reintroduced with restrictions in 1990 First “atypical” antipsychotic as it did not produce extrapyramidal side effects. Study of clozapine lead to 5-HT 2a /D 2 hypothesis: To overcome side effects of chloropromazine: i.e. better binding affinty at 5-HT 2a than D 2 K i 5-HT 2a K i D 2 < 1.0 3/9/11CHEM E-120

18. 18 Clozapine K i 5-HT 2a K i D 2 < 1.0 ReceptorK i nMReceptorK i nM D1D1 53 11 3.7 D2D2 36  2A 51 D3D3 160  2B 22 D4D4  2C 9 5-HT 1A 710H1H1 17 5-HT 1B 1200M1M1 1.9 5-HT 1D 980M2M2 10 5-HT 2A 4M3M3 14 5-HT 2B 8.5M4M4 18 5-HT 2C 5.5 5-HT 3 110 5-HT 6 4 5-HT 17 21 3/9/11CHEM E-120

19. 19 Receptors and Effects CNS Drugs 2008 22, 1047 3/9/11CHEM E-120

20. 20 Newer Atypical Antipsychotics 3/9/11CHEM E-120

21. 21 Atypical Antipsychotics Binding Data MARTA – multiacting receptor-targeted antipsychotic, SDA – serotonin-dopamine antagonist 3/9/11CHEM E-120

22. 22 Animal Behavioral Models Conditioned avoidance The ability of a compound to inhibit the conditioned avoidance response (CAR) to an aversive stimulus is one of the oldest predictors of antipsychotic efficacy. In this test, rats are trained to move from one side of shuttle box to the other on presentation of an audible cue (the conditioned stimulus) in order to avoid a footshock (the unconditioned stimulus). Once the animals have been trained, both typical and atypical antipsychotics are effective in decreasing the CAR to the conditioned stimulus without altering the escape response elicited by the unconditioned stimulus. This inhibition of the CAR is thought to be mediated by a reduction in dopaminergic function in the striatum and nucleus accumbens. Therefore, inhibition of CAR is not an actual preclinical model of schizophrenia, but rather a facile in vivo method of detecting DA receptor blockade. The comparison between doses of antipsychotics that inhibit CAR and doses that induce catalepsy provides a convenient method to determine the therapeutic index for EPS. 3/9/11CHEM E-120

23. 23 Animal Behavioral Models Locomotor activity Practically all antipsychotic agents decrease spontaneous locomotor activity and decrease locomotor activity that has been pharmacologically increased by amphetamine, PCP 2, or apomorphine. As described for CAR, decreased locomotor activity can be interpreted as an in vivo readout of DA antagonism. However, the ability of nondopaminergic agents to induce hyperlocomotion that is sensitive to antipsychotics, and the ability of novel nondopaminergic compounds to reduce hyperlocomotion elicited by amphetamine suggest that this particular model involves a more complex circuit that may possibly have some relevance to the clinical state. 3/9/11CHEM E-120

24. 24 Animal Behavioral Models Latent inhibition Latent inhibition is the ability of a pre-exposed nonreinforced stimulus to inhibit later stimulus-response learning. This behavior can be disrupted by amphetamine in both rodents and humans. While often put forward as a model of positive symptoms with significant face validity, a careful review of the literature reveals significant disagreement on key facts, including the prevalence of disrupted latent inhibition in schizophrenic patients, the responsiveness of amphetamine-disrupted latent inhibition to atypical antipsychotics, and key differences between experimental paradigms used in human and animal studies. Results employing the latent inhibition assay must be interpreted with caution until these controversies are fully addressed. 3/9/11CHEM E-120

25. 25 Animal Behavioral Models Prepulse inhibition A disruption in sensory and cognitive gating is hypothesized to be at the core of many of the symptoms of schizophrenia. Prepulse inhibition (PPI) refers to the ability of a low-intensity stimulus, or prepulse, to diminish the startle response elicited by a higher-intensity stimulus. This model has gained significant favor in recent years largely due to the findings that schizophrenic patients exhibit deficits in sensory and cognitive gating. This is particularly evident in studies of event-related potentials (ERPs) in the electroencephalogram of schizophrenic patients. These differences in ERPs suggest that schizophrenic patients have a deficit in the gating or processing of sensory information. This impaired sensorimotor gating may underlie the vulnerability in schizophrenia to sensory flooding, cognitive fragmentation, and conceptual disorganization. PPI is disrupted by a wide range of psychotomimetics and can be rescued by treatment with antipsychotic drugs. Based on the high degree of face validity, apparent predictive validity, and the ability to strengthen construct validity by disrupting the behavior with multiple classes of psychotomimetics, PPI stands out as the current ‘gold standard’ assay for evaluating animal models of schizophrenia. 3/9/11CHEM E-120

26. 26 CATIE - 2005 Large scale clinical trial sponsered by NIH involving 1493 patirents at 57 sites (NEJM 2005, 353, 1209). Patients were randomely assigned to olanzapine (7.5 - 30 mg/day)SGA perphenazine (8 - 32 mg/day)FGA quetiapine (200 - 800 mg/day)SGA risperidone (1.5 - 6 mg/day)SGA ziprasidone (40 - 160 mf/day)SGA 74% discontinued use before 18 months due to side-effects or lack of efficacy. Judged that in terms of efficacy and patient compliance SGA may be no better that FGA Calls into question the entire D 2 /5-HT 2A approach 3/9/11CHEM E-120

27. 27 Aripiprazole D 2 and 5-HT 1A partial agonist Approved for use in USA 2002. Efficacy against positive and negative symptoms. Same rate of EPS (21%) as placebo(19%) vs haloperidol(43%) 90% bioavialable t 1/2 = 75 hours, 94 hrs active metabolite 10-15 mg/day maintenance dose 10 - 30 mg/day 3/9/11CHEM E-120

28. 28 Aripiprazole Partial agonists Low levels of endogenous full agonist - partial agonist active High levels “ - partial agonist = antagonist In PFC will act as agonist relieving negative symptoms In limbic/striatum will act as antagonist relieving pos symptoms 3/9/11CHEM E-120

29. 29 Discovery of Aripiprazole Chem. Pharm. Bull 1988, 36, 4377 Otsuka Pharmaceutical Co. Developed into several drugs Looking for anti-histimine drugs w/o CNS side effects Neuroleptic-like activity in rodent screen and did not have EPS This compound was used as a lead to explore the development of antipsychotics with fewer side effects No Dopamine receptor antagonism Inhibition of DA release from presynaptic neurons or inhibit DA synthesis 3/9/11CHEM E-120

30. 30 Discovery of Aripiprazole Chem. Pharm. Bull 1988, 36, 4377 Otsuka Pharmaceutical Co. n = 1-4 22 mono and disub benzene rings Prepared 34 compounds and compared to chlopromazine and haloperidol Dopamine induces jumping behavior in mice  1. Inhibition of L-DOPA induced jumping (L-DOPA converted to DA) 2. Inhibition of methamphetamine-induced jumping (DA releaser) 3. EPS side effects measured by induction of catalepsy in mice 3/9/11CHEM E-120

31. 31 Discovery of Aripiprazole Inhibition of jumping behavior 5>6,7>8 No  -adrenergic antagonism (side effects) 8>7>>6>5 Inhibition of jumping behavior n = 3 ≥ 4 >> 2,5 3/9/11CHEM E-120

32. 32 Discovery of Aripiprazole Inhibition of jumping behavior 1-2 substituents found to enhance activity 2,3-dichloro reduced activity ED 50 37 mg/kg 2-CH 3 ED 50 0.7 mg/kg 2,3-diCH 3 ED 50 1.2 mg/kg 2-F ED 50 1.9 mg/kg Induction of catalepsy in mice < chlorpromazine and haloperidol 3/9/11CHEM E-120

33. 33 Discovery of Aripiprazole Was in clinical trials but stopped Aggravated positive symptoms In some patients Autoreceptor Agonist effects 3/9/11CHEM E-120

34. 34 Discovery of Aripiprazole J Med Chem 1998, 41, 658 Postsynaptic DA receptor antagonist: ability to inhibit APO-induced sterotypic behavior (locomoter activity) in mice (anti-APO test) Presynaptic DA autoreceptor agoinst activity: ability to reverse the increase in DOPA synthesis induced by GBL (gamma-butyrolactone) 3/9/11CHEM E-120

35. 35 Discovery of Aripiprazole ED 50  mol/kg po (anti-APO test) 41 26 17 2.8 >23 Butoxy chain best 3/9/11CHEM E-120

36. 36 Discovery of Aripiprazole Anti-APO test ED 50  mol/kg po If 2 = CH 3, at 3 Cl = Br >F If 2 = CH 3,electron-withdrawing at 3 increases potency electron-releasing at 3 decreases potency 2-CH 3,3-ClED 50 = 2.8  mol/kg po 2-Cl, 3-CH 3 ED 50 = 0.9  mol/kg po 2,3-(Cl) 2 ED 50 = 0.6  mol/kg po 2,4>7.0 2,52.7 2,6>7.0 3,4>7.0 3,51.1 3/9/11CHEM E-120

37. 37 Discovery of Aripiprazole Anti-APO test Position ED 50  mol/kg po 5>22 6>22 70.6 8>22 SAR results for Postsynaptic DA receptor antagonism Side chain C 4 > C 3 and C 5 1-2 substituents on aromatic ring 2-OCH 2 CH 3 best for 1 substituent 2,3-dichloro best for 2 substituents Substitution at position 7 of 3,4-dihydroquinolinone ring is best 3/9/11CHEM E-120

38. 38 Discovery of Aripiprazole measurement of peripheral activity ED 50  mol/kg po Inhibit GBL Induced DOPA synthesis B/A adverse effect beneficial effect 3/9/11CHEM E-120

39. 39 Discovery of Aripiprazole Time course of inhibition of APO-induced sterotypy at 1-6 hours after 30mg/kg po No inhibition Maximum inhibition at 2 and 4 hrs after admin. ED 50 49  mol/kg Complete inhibition at 2 hours ED 50 11.8  mol/kg 3/9/11CHEM E-120

40. 40 Discovery of Aripiprazole Agonist activity Antagonist activity JPET 1995, 274, 329 3/9/11CHEM E-120

41. 41 Metabolism of Aripiprazole K i (nM) ReceptorAripiprazoleOPC-14857 5-HT 2A 7.92.5 5-HT 2C 12663 D 2 10.5 D 3 1020 5-HT 6 10079 European J Pharmacology 2006, 546, 88 OPC-14857 Aripiprazole 3/9/11CHEM E-120

42. 42 Metabolism of Aripiprazole Full agonist EC 50 4.7 nM EC 50 1.5 nM 3/9/11CHEM E-120

43. 43 Bifeprunox (DU-127090) - Solvay D 2 K i = 3.2 nMpartial agonist (28% at 1  M) 5-HT 1A K i = 10 nMpartial agonist, D 3 K i = 0.6 nM D 4 K i = 1.6 nM PET imaging at 10mg, 90% occupancy of striatal D 2 after 2 hours Not approved by FDA in 2007 due to lack of efficacy 3/9/11CHEM E-120

44. 44 D 2 antagonist/5-HT 1A agonist Tried to mimic (bioisostere) Biphenyl methylamine but could not Biphenyl critical 3/9/11CHEM E-120

45. 45 D 2 antagonist/5-HT 1A agonist 3/9/11CHEM E-120

46. 46 D 2 antagonist/5-HT 1A agonist 16 20 3/9/11CHEM E-120

47. 47 D 2 antagonist/5-HT 1A agonist Inhibition of methyl phenidate (indirect DA agonist) induced stereotypy & hyperlocomotion Potency to induce catalepsy Lower lip retraction 5-HT 1A agonist Flat-body syndrome 1.1 - 8.3 mg/kg - range of 5-HT 1A agonism to achieve antipsychotic effects w/o negative 5-HT behavioral changes (rats) 5-HT 1A /D 2 3/9/11CHEM E-120

48. 48 GABA Agonists Prodrugs as Antipsychotics GABA reported to attenuate cognitive deficits of schizophrenia and reduce EPS from D 2 antagonists. GABA does not cross BBB though. Theory - conjugate GABA with D 2 antagonists that are known to cross BBB J. Med. Chem. 2008, 51, 2858 3/9/11CHEM E-120

49. 49 GABA Agonists Prodrugs as Antipsychotics 3/9/11CHEM E-120

50. 50 GABA Agonists Prodrugs as Antipsychotics Induction of catalepsy (ip) 3/9/11CHEM E-120

51. 51 GABA Agonists Prodrugs as Antipsychotics Prolactin inc as measure of D antagonism (ip) Plasma prolactin levels in rats treated po Perphenazine 5, 10, 20 mg/kg 3 7,14,28 mg/kg 3/9/11CHEM E-120

52. 52 GABA Agonists Prodrugs as Antipsychotics Perphenazine and 3 · 3HCl abrogate hyperactivity induced by D-amphetamine in rats. Male Wistar rats divided into five groups (six/group) were treated po respectively with: vehicle (1% lactic acid, two groups); perphenazine (2.5 mg/kg); an equimolar dose of 3 · 3HCl; and GABA (1 mg/kg). With the exception of one of the vehicle treated groups, which served as negative control, after 90 min all other animals received D-amphetamine (2.0 mg/kg, ip). The rats were then placed individually in barrels, and the number of head movements and climbing attempts on the barrel walls were recorded double-blindly. 3/9/11CHEM E-120

53. 53 Emerging Targets Muscarinc M1/M4 agonist - antipsychotic activity w/o catalepsy  7 nAChR (nicotinic acetylcholine) partial agonist Cognition enhancing properties Highly expressed in PFC, perhaps involved in sensory gating JMC 2006, 49, 4374 3/9/11CHEM E-120

54. 54 Emerging Targets Histamine H 3 Antagonists - potential for cognitive improvement Gluamatergic - NMDA positive allosteric modulation Metabotropic Glutamate (mGLUR) agonist mGlu2/3 agonists - Phase 2 trial (Nature Medicine 2007, 13, 1102) AMPA agonist Glutamate transporter inhibition D 4 antagonists Phosphodiesterase inhibitors - PDE4 Neurokinin - NK 3 antagonists (Bioorganic & Med. Chem Lett 2009, 19, 837) Cannabinoids - CB 1 antagonists can reduce stimulant-induced hyperactivity J. Medicinal Chemistry 2008, 51, 1077-1107 Emerging Opportunities for Antipsychotic Drug Discovery in the Postgenomic Era Pharmacological Reviews 2008, 60, 358-403, Antipsychotic Drugs: Comparison in Animal Models of Efficacy, Neurotransmitter Regulation, and Neuroprotection. 3/9/11CHEM E-120