Nonclinical Overview: CNS Toxicity with Rimonabant Endocrinologic & Metabolic Drugs Advisory Committee June 13, 2007 Karen Davis-Bruno, Ph.D. Division of Metabolism & Endocrinology Products Endocrinologic & Metabolic Drugs Advisory Committee June 13, 2007 Karen Davis-Bruno, Ph.D. Division of Metabolism & Endocrinology Products Center for Drug Evaluation and Research

Endocrinologic & Metabolic Drugs Advisory Committee June 13, Presentation Overview Role of the endogenous endocannabinoid system (ECS) Rimonabant pharmacology focused on its MOA Nonclinical toxicology focused on CNS Clinical relevance of CNS toxicity Role of the endogenous endocannabinoid system (ECS) Rimonabant pharmacology focused on its MOA Nonclinical toxicology focused on CNS Clinical relevance of CNS toxicity

Endocrinologic & Metabolic Drugs Advisory Committee June 13, ECS Modulatory Role Complex cellular signaling system Endogenous –CNS, PNS Neuroprotection –Functions Motor Behavior Cognitive Memory Complex cellular signaling system Endogenous –CNS, PNS Neuroprotection –Functions Motor Behavior Cognitive Memory From:

Endocrinologic & Metabolic Drugs Advisory Committee June 13, Endocannabinoid System

Endocrinologic & Metabolic Drugs Advisory Committee June 13,

Endocrinologic & Metabolic Drugs Advisory Committee June 13, On-Demand Activation of ECS: Retrograde Neurotransmission From:

Endocrinologic & Metabolic Drugs Advisory Committee June 13, ECS Modulatory Role is Complex Tissue Level Effects: –Motor, behavior, cognition, memory, sensory Cellular Level Effects: –Neurotransmission Retrograde neurotransmission Modulation of neurotransmitter activity –e.g. GABA, DA, 5HT, glutamate, vanilloid, NMDA, Ach, NE, orexin-1 –Ion channel function (Ca, K channels) –Multimeric interaction of CB1R with other CNS receptors CB, DA, opioid, adenosine Molecular Level: –Pleiotropic effects on signal transduction Inhibition of AC & PKA Stimulation of MAPK Effects on gene expression Multiple G-proteins coupled to CB receptor Tissue Level Effects: –Motor, behavior, cognition, memory, sensory Cellular Level Effects: –Neurotransmission Retrograde neurotransmission Modulation of neurotransmitter activity –e.g. GABA, DA, 5HT, glutamate, vanilloid, NMDA, Ach, NE, orexin-1 –Ion channel function (Ca, K channels) –Multimeric interaction of CB1R with other CNS receptors CB, DA, opioid, adenosine Molecular Level: –Pleiotropic effects on signal transduction Inhibition of AC & PKA Stimulation of MAPK Effects on gene expression Multiple G-proteins coupled to CB receptor

Endocrinologic & Metabolic Drugs Advisory Committee June 13, Rimonabant Inverse Agonist Properties Binds at agonist receptor binding site Results in opposite effect- negative intrinsic activity Effective in receptors with intrinsic activity (e.g. CB1) Effect depends on: –Ligand –Tissue –Dose U-shaped dose-response curves seen for EC Binds at agonist receptor binding site Results in opposite effect- negative intrinsic activity Effective in receptors with intrinsic activity (e.g. CB1) Effect depends on: –Ligand –Tissue –Dose U-shaped dose-response curves seen for EC

Endocrinologic & Metabolic Drugs Advisory Committee June 13, Rimonabant Pharmacology 1.Rimonabant competes with endogenous endocannabinoids for CB1 receptor binding 2.Inverse agonism resulting from negative modulation of CB1 receptor constitutive activity Allosteric effects Active/on to inactive/off state 3.CB1 receptor independent mechanisms For example: antagonism of endogenous adenosine at A1 receptors 1.Rimonabant competes with endogenous endocannabinoids for CB1 receptor binding 2.Inverse agonism resulting from negative modulation of CB1 receptor constitutive activity Allosteric effects Active/on to inactive/off state 3.CB1 receptor independent mechanisms For example: antagonism of endogenous adenosine at A1 receptors

Endocrinologic & Metabolic Drugs Advisory Committee June 13, Rimonabant ? Animal Adverse Effects: Seizures Tremors Impaired movement Sleep disturbance Hyperesthesia Anxiety Hyperexcitability Desired Effects:  Appetite  Food Intake  Body Weight Other Beneficial Effects:  TG,  HDL-C,  HbA1c ? CB1 (─)(─) (─)(─) Rimonabant Pharmacology

Endocrinologic & Metabolic Drugs Advisory Committee June 13, ECS Effects ± Rimonabant Endocannabinoid System Effects Modulation of Constitutive Effect Rimonabant Effect Motor ↓ activity anti-convulsant seizures, tremors, Impaired and ↓ movement Sensory ↓ pain Hyperesthesia, ↓ body temperature, hyper-excitability, ↑ startle response Behavior anti-anxiety somnolence orexigenic Anxiety, sleep disturbances, anti-orexigenic

Endocrinologic & Metabolic Drugs Advisory Committee June 13, CB1 receptors: Conservation Across Species Similarity of √CNS regional distribution √Receptor homology √Ligand affinity  Animal models have clinical relevance Similarity of √CNS regional distribution √Receptor homology √Ligand affinity  Animal models have clinical relevance

Endocrinologic & Metabolic Drugs Advisory Committee June 13, Key Points CB1 Receptor Pharmacology The ECS has pleiotropic neuromodulatory functions ECS is involved in the regulation of CNS activity through CB1 receptors CB1 receptor sequence & distribution are highly conserved across species Rimonabant is a CB1 receptor antagonist with complex pharmacology and similar affinity across species The ECS has pleiotropic neuromodulatory functions ECS is involved in the regulation of CNS activity through CB1 receptors CB1 receptor sequence & distribution are highly conserved across species Rimonabant is a CB1 receptor antagonist with complex pharmacology and similar affinity across species

Endocrinologic & Metabolic Drugs Advisory Committee June 13, Nonclinical Toxicology of Rimonabant −Pharmacology −General toxicology in mice, rats, dogs, and monkeys −Chronic tox rat (6 mo) & monkey (12 mo) −Two-year rat & mouse carcinogenicity studies −Genotoxicity studies −Reproductive toxicity studies in rats and rabbits CNS major target organ of concern −Pharmacology −General toxicology in mice, rats, dogs, and monkeys −Chronic tox rat (6 mo) & monkey (12 mo) −Two-year rat & mouse carcinogenicity studies −Genotoxicity studies −Reproductive toxicity studies in rats and rabbits CNS major target organ of concern

Endocrinologic & Metabolic Drugs Advisory Committee June 13, Lowest Effective Dose for CNS Toxicities at Clinical Exposure (20 mg/day) CNS ToxicitiesMouseRatMonkeyDogRabbit Mortality2X1X>3X>5X<1X Convulsion3X1X2X Tremor1X4X Motor effects1X 3X5X Aggressiveness1X5X Anxiety1X2X5X

Endocrinologic & Metabolic Drugs Advisory Committee June 13, Seizure: No Safety Margins CNS Toxicity Effect of Rimonabant Multiple of Human Exposure Species NOAEL (mg/kg) Safety Margin* Based on AUC Safety Margin* Based on Cmax Convulsion Mouse201X2X Rat2.5<1X Monkey4<1X Dog153X Tremor Rat2.5<1X Dog51X2X Safety Margin = Exposure in animals at NOAEL / Exposure in humans at 20 mg/day

Endocrinologic & Metabolic Drugs Advisory Committee June 13, Time-Dependent Progressive Convulsive Activity in Multiple Species Minimum Dose Associated with Convulsions Species Tested Acute Toxicity Studies (mg/kg) Sub-acute Toxicity Studies (mg/kg/day) Chronic Toxicity Studies (mg/kg/day) Mouse Rat606 Monkey1512

Endocrinologic & Metabolic Drugs Advisory Committee June 13, Dose-Dependent Seizures Lifetime Rat Bioassay

Endocrinologic & Metabolic Drugs Advisory Committee June 13, Rimonabant potentiates PTZ-induced convulsions & mortality in mice after S.D. NDA Sanofi

Endocrinologic & Metabolic Drugs Advisory Committee June 13, Key Points: Rimonabant CNS Toxicity Rimonabant blockade of CB1 receptors appears to influence the anti-convulsant tone of ECS Rimonabant induced dose-dependent seizures in association with CB1 receptor antagonism in multiple species Seizures were dependent on the dose and duration of rimonabant treatment Seizures occurred at animal exposures equivalent to systemic exposure in humans at the proposed clinical dose (20 mg/day) Rimonabant blockade of CB1 receptors appears to influence the anti-convulsant tone of ECS Rimonabant induced dose-dependent seizures in association with CB1 receptor antagonism in multiple species Seizures were dependent on the dose and duration of rimonabant treatment Seizures occurred at animal exposures equivalent to systemic exposure in humans at the proposed clinical dose (20 mg/day)

Endocrinologic & Metabolic Drugs Advisory Committee June 13, Experience with other CB1 antagonists Several applications for CB1 receptor antagonists under review CNS toxicity is observed but at ≥ 10X therapeutic exposure –Convulsions –Tremor –Motor dysfunction –Suggests rimonabant differs from others in the class by its narrow therapeutic index Several applications for CB1 receptor antagonists under review CNS toxicity is observed but at ≥ 10X therapeutic exposure –Convulsions –Tremor –Motor dysfunction –Suggests rimonabant differs from others in the class by its narrow therapeutic index

Endocrinologic & Metabolic Drugs Advisory Committee June 13, Clinical Relevance of CNS Toxicity Clinically Relevant Rimonabant Effects Multiples of Human Therapeutic Exposure* MouseRatMonkeyDogRabbit Desired pharmacologic activity Weight loss<1 1 CNS toxicities Mortality21>3>5<1 Convulsion312 Tremor14 Motor effects1135 Anxiety125 *Animal exposure at NOAEL / Clinical exposure at 20 mg/day ↓ Weight & CNS Toxicity at Similar Drug Exposures

Endocrinologic & Metabolic Drugs Advisory Committee June 13, SummarySummary CNS toxicity occurs in multiple species at therapeutic exposure levels based on a 20 mg clinical dose Dose-dependent CNS toxicities occur as a result of antagonism of the CB1 receptor and disturbance of the ECS homeostatic regulation The plausible MOA associated with weight loss appears associated with CNS toxicity Other drugs in the class show similar toxicities but occur at much higher animal exposures There are limited, if any, differences between exposures generating the desired pharmacologic effect and those associated with significant animal toxicity (seizures, mortality) supporting the clinical relevance of the CNS toxicity CNS toxicity occurs in multiple species at therapeutic exposure levels based on a 20 mg clinical dose Dose-dependent CNS toxicities occur as a result of antagonism of the CB1 receptor and disturbance of the ECS homeostatic regulation The plausible MOA associated with weight loss appears associated with CNS toxicity Other drugs in the class show similar toxicities but occur at much higher animal exposures There are limited, if any, differences between exposures generating the desired pharmacologic effect and those associated with significant animal toxicity (seizures, mortality) supporting the clinical relevance of the CNS toxicity

Endocrinologic & Metabolic Drugs Advisory Committee June 13, ConclusionsConclusions Rimonabant is a 1 st in class, CB1 receptor antagonist for the management of obesity Sufficient information to demo complex pharmacologic profile Blockade of ECS-mediated orexigenic stimulus may be desirable for obesity but a similar blockade of other CNS functions under regulation by ECS would not be desirable Studies in relevant animal species show CNS toxicities at clinically relevant therapeutic exposures European Regulators (EMEA) 2006: “….nonclinical studies could provide no reassurance regarding margins to the clinical exposure. Consequently, the safe use of rimonabant has to rely more on the clinical safety data and post-approval pharmacovigilance programme.” CNS adverse events consistent with the MOA are reported in the clinic and post-marketing Rimonabant is a 1 st in class, CB1 receptor antagonist for the management of obesity Sufficient information to demo complex pharmacologic profile Blockade of ECS-mediated orexigenic stimulus may be desirable for obesity but a similar blockade of other CNS functions under regulation by ECS would not be desirable Studies in relevant animal species show CNS toxicities at clinically relevant therapeutic exposures European Regulators (EMEA) 2006: “….nonclinical studies could provide no reassurance regarding margins to the clinical exposure. Consequently, the safe use of rimonabant has to rely more on the clinical safety data and post-approval pharmacovigilance programme.” CNS adverse events consistent with the MOA are reported in the clinic and post-marketing