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Safety Pharmacology

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  1. Safety Pharmacology

  2. Outline of lecture • Definition of safety pharmacology • Why is it important? • Role in Drug Discovery and Development • Drug induced QT prolongation • Integrating safety pharmacology data • Summary and Future perspective

  3. ICH definitions of pharmacology • Primary Pharmacodynamics • identifies desired properties of a molecule • Secondary Pharmacodynamics • identifies other properties of a molecule which are of no particular importance for safety • Safety Pharmacology • identifies other properties of a molecule which have safety implications

  4. ICH definition of Safety Pharmacology “Safety pharmacology studies are those studies that investigate potential undesirable pharmacodynamic effects of a substance on physiological functions in relation to exposure therapeutic range and above.” • “Docis sola facit venenum nen sit” - “The dose makes the poison” • Paracelsus (1494-1541) ICH S7A Guideline for Safety Pharmacology Studies (2000)

  5. ICH S7A stated objectives of Safety Pharmacology studies • To identify undesirable pharmacodynamic properties of a substance that may have relevance to its human safety; • To evaluate adverse pharmacodynamic and/or pathophysiological effects of a substance observed in toxicology and/or clinical studies; • To investigate the mechanism of the adverse pharmacodynamic effects observed and/or suspected. ICH S7A Guideline for Safety Pharmacology Studies (2000)

  6. Outline of lecture • Definition of safety pharmacology • Why is it important? • Role in Drug Discovery and Development • Drug induced QT prolongation • Integrating safety pharmacology data • Summary and Future perspective

  7. Reasons for attrition during development • Safety still the main reason for drug discontinuation • Situation didn’t improve through the 90s • CV safety is the most common target organ Landis & Kola, 2004

  8. Safety reasons for drug withdrawal • Cardiovascular and CNS toxicities have been the leading reasons for drug withdrawals over the last decade • Strategies to reduce predictable toxicities are central to improving the quality and viability of new therapeutic agents Stephens, 2004

  9. What does safety pharmacology offer clinicians? Goes beyond regulatory ‘box-ticking’... • Early information for risk assessment in terms of product viability • A therapeutic window for acute dosing in man • A set of anticipated side-effects for the clinicians involved in Phase I design • A set of tools for testing mechanistic hypotheses

  10. Outline of lecture • Definition of safety pharmacology • Why is it important? • Role in Drug Discovery and Development • Drug induced QT prolongation • Integrating safety pharmacology data • Summary and Future perspective

  11. Input across the discovery-development continuum Safety pharmacology consultation Hazard prediction Hazard identification Risk assessment Risk management and mitigation Registration support Target safety evaluation Follow-up / investigative studies Product support • Pre-candidate • De-risking leads • Profiling candidates GLP core battery studies inc. tox Due diligence support Theoretical target liabilities

  12. Regulations 2001 1996 1997 1998 1999 2000 2002 2003 2004 2005 2006 2007? CPMP/986/96:The assessment for the potential for QT prolongation by non-cardiovascular medicinal products ICH S7B:The non-clinical evaluation of the potential for delayed ventricular repolarisation (QT interval prolongation) by human pharmaceuticals EMEA/CHMP/SWP/94227/2004:Guideline on the non-clinical investigation of the dependence potential of medicinal products ICH S7A:Safety Pharmacology studies for human pharmaceuticals ICH S6:Nonclinical evaluation of biotechnology-derived pharmaceuticals: includes safety pharmacology requirements E14:The clinical evaluation of QT/QTc interval prolongation and proarrhythmic potential for non-antiarrhythmic drugs Increasing number and scope reflecting increasing regulatory conservatism and focus on safety pharmacology

  13. ICH S7A Safety Pharmacology Guideline Has clarified many aspects of safety pharmacology studies...

  14. Timing, GLP, route, and dose selection • Timing of studies • to support FTIH • generally done in parallel with Regulatory Toxicology studies • Compliance with GLP • studies are clearly safety studies so should be done to GLP (to the greatest extent feasible) • Route of administration • intended clinical route should be used where feasible • Dose selection • no longer acceptable to test up to a multiple (e.g. 100x) of a pharmacologically active dose • need to demonstrate there is either • an effect on the parameter of interest, or • an effect on some other parameter, which makes further dose escalation pointless

  15. Scope of studies • Core battery studies • Investigate the effects of the test substance on vital functions • Cardiovascular, respiratory and central nervous system • Follow-up studies • Provide greater depth of understanding than, or additional knowledge to, that provided by the core battery on vital functions • Supplemental studies • Evaluate potential adverse pharmacodynamic effects on organ system function not addressed by the core battery or repeated dose toxicity studies

  16. What is typically measured as the Core Battery? Central nervous system motor activity, behavioural changes, coordination, sensory/motor reflex responses, body temperature (e.g. using FOB). Cardiovascular system blood pressure, heart rate, ECG; In vivo, in vitro and/or ex vivo methods incl. methods for repolarization and conductance abnormalities should also be considered. Respiratory system respiratory rate and tidal volume or hemoglobin oxygen saturation. Clinical observation of animals is generally not adequate.

  17. What is typically done as the Core Battery? • Cardiovascular • In vitro hERG (IKr) study • In vivo non-rodent (usually telemetry) • Central Nervous System • In vivo rodent Irwin or Functional Observational Battery (FOB) • Respiratory function • In vivo rodent generally using plethysmography

  18. In vitro hERG study • hERG = ‘human ether-a-go-go related gene’ - clone of the native cardiac potassium current (IKr) which is important during cardiac repolarization • hERG channel stable expression in a mammalian cell line e.g. HEK 293 • hERG current amplitude measured in single cells using whole cell patch clamp technique • Derive potency measures (IC25, 50, 75) from concentration-response curve

  19. In vivo cardiovascular study • Anaesthetised or conscious telemetered non-rodents (dogs, primates, mini-pigs) • Usually single dose Latin square or escalating dose designs • Assess time course and magnitude of effects, and plasma concentration (where PK included) Raw data example Terfenadine QTc dose-response in dogs ABP ECG

  20. In vivo CNS study • Observational methods for assessing multiple behavioural, neurological and autonomic parameters in rats or mice. Non-rodents may also be used. • The two main tests used are either the Irwin test or the Functional Observational Battery (FOB) • FOB test includes additional quantitative measures e.g. grip strength • Usually escalating dose design • Assess time course and nature of effects, and plasma concentration (where PK included)

  21. In vivo respiratory study Theophylline (10 mg/kg, iv) Rat • Anaesthetised or conscious rodents (mice, rats). Non-rodents may also be used. • Usually single dose Latin square or escalating dose designs • Assess time course and magnitude of effects, and plasma concentration (where PK included) Whole body Plethysmograph Ventilatory parameters Head-out plethysmograph

  22. Follow-up, supplemental and toxicology studies • Follow-up studies • too many options to cover! • Supplemental studies • For example, autonomic, renal, gastro-intestinal etc • Safety pharmacology endpoints in toxicology studies • ECGs at pre-defined timepoints or via ambulatory telemetry methods • Other parameters as needed (e.g. neurological assessment) • Allows data to be obtained after repeat dosing • Non-invasive technology allows collection of Lead II ECG and non-invasive blood pressure in chronic toxicology studies

  23. Abuse potential assessment • Regulatory requirements • No specific guidelines currently exist in US and Japan. • Europe EMEA guideline issued in 2006 • However, • assessment of abuse generally required for all compounds that enter the CNS • Preclinical package consists of • drug discrimination (in rodents), • self-administration (commonly in primates) • physical dependence/withdrawal (in rodents)

  24. Abuse potential assessment continued • Summary of early indicators for assessing the abuse and dependence liability of a novel compound • CNS activity • Chemical structure similarities • Mechanism of action • Adverse events in pre-clinical studies • Adverse events in (early) clinical trials • PK/PD characteristics • Pharmaceutical characteristics

  25. What about non-regulatory safety pharmacology? • Many companies conduct non-regulatory (non-GLP) safety pharmacology early in Discovery • To identify safety pharmacology-related liabilities early in discovery process • To help direct chemistry • To rank compounds and aid selection of drug candidates • To aid internal decision making

  26. Generic Safety Pharmacology strategy for NCEs SP endpoints in Toxicology e.g. ECGs Routine Follow-up SP studies Case-by-case Lead to Candidate Candidate to FTIH Clinical development Lead FTIH Candidate Selection Launch Early Safety Pharmacology Regulatory Safety Pharmacology in silico:(e.g. hERG) GLP in vivo CV GLP in vivo CNS GLP in vivo RES GLP in vitro hERG Abuse liability testing in vitro:ion channels (inc. hERG), isolated tissues Case-by-case Routine in vivo:conscious or anaesthetised models Case-by-case Alternate sources of information: e.g. pharmacological profiling data

  27. What about biologicals? • Regulatory guidance • ICH S6: “...important to investigate the potential for undesirable pharmacologic activity in appropriate animal models and, where necessary, to incorporate monitoring for these activities in the toxicity or clinical studies...” • ICH S7A: “For biotechnology-derived products that achieve highly specific receptor targeting, it is often sufficient to evaluate safety pharmacology endpoints as part of toxicology and/or pharmacology studies, and therefore safety pharmacology studies can be reduced or eliminated for these products.” • No specific mention of biologicals in ICH S7B and ICH E14

  28. What about biologicals? • What safety pharmacology is required • An assessment of core organ system function is required • in separate standalone in vivo safety pharmacology studies • or endpoints incorporated into toxicity studies • Option taken may depend on • nature, biology, physicochemical characteristics, and species specificity of the molecule • biology and expression of target • What about hERG? • limited value as biological not likely to enter cells and block channel like small molecules (size matters) • high affinity off-target interactions with ion channel proteins less likely with proteins with highly specific receptor binding • Confounding effects of excipients and assay protein free-buffers

  29. Outline of lecture • Definition of safety pharmacology • Why is it important? • Role in Drug Discovery and Development • Drug induced QT prolongation • Integrating safety pharmacology data • Summary and Future perspective

  30. Acquired Long QT syndrome • Membrane cardiac ion channel - hERG - underlies repolarization of the AP • Cardiac cellular electrical activity - action potential underlying ECG • ECG : normal and showing QT prolongation • ECG showing Torsades de Points (TdP) arrhythmia ? Spontaneous termination, Syncope, VF, SCD

  31. Post-marketing signals of Torsade de Pointes (TdP) and sudden cardiac death for a number of non-cardiovascular medicines Poor prediction of post-marketing response - as a result a number of drugs were withdrawn or suspended from at least one major market for causing TdP. These drugs also prolong QT interval of the ECG List is growing, see Why the regulatory concern?

  32. Regulatory response – ICH E14 and ICH S7B • Clinical (ICH E14) and pre-clinical (ICH S7B) guidance documents dealing specifically with ventricular repolarisation (QT interval prolongation) issued in 2005 • Required tests • ICH E14: A ‘thorough QT study’ in HV or patients • ICH S7B: a GLP hERG and GLP in vivo QT assessment prior to FTIH • S7B & E14 tests focus on QT prolongation but • Unlikely to see TdP as it is a rare event (1 in 10000 – 100000 exposures) • QT prolongation is not the clinical problem • QT prolongation itself may be benign, TdP never is

  33. Regulatory guidance – ICH E14 • ICH E14 • Thorough QT/QTc Study • Serves as the basis for evaluation of arrhythmogenic potential • Required for almost all NCEs • A study designed to detect or rule out a small degree of QT prolongation (approx. 10 msec) • Long duration (compared with typical HV studies) 6-12 months • Very Costly ($1-3 million per study) • Consequences of developing a compound with a clinical QT effect • Increased risk = increased effort to demonstrate benefit • Increased costs • Delays in filing and/or approval • Label warnings • Competitive implications

  34. Ranolazine – anti-anginal Cisapride (300nM) MAP ECG Cisapride (300nM) + Ranolazine (10mM) However… MAP ECG Clinical QTc prolongation • Clinical QTc prolongation contributed to a delayed approval • Pre-clinical studies demonstrated it did not induce TdP, and suppressed drug-induced TdP (in vitro & in vivo) • Approved in US in January 2006, approval in Europe pending • Recent clinical data suggests an antiarrhythmic property (Scirica et al 2007)

  35. Complications • Not all compounds which inhibit hERG cause QTc prolongation and/or TdP, and not all compounds that cause QTc prolongation and/or TdP inhibit hERG • The precise relationship between drug-induced prolongation of ventricular repolarisation and the risk of proarrhythmia is not fully understood • Not always is TdP preceded by significant QT prolongation • Not always is QT interval prolongation associated with TdP • Not all drug-induced arrhythmias are due to hERG block / QT prolongation

  36. Outline of lecture • Definition of safety pharmacology • Why is it important? • Role in Drug Discovery and Development • Drug induced QT prolongation • Integrating safety pharmacology data • Summary and Future perspective

  37. Integrating non-clinical and clinical data • Integrated risk assessment is central to the proposed non-clinical testing strategy in ICH S7B

  38. Some Factors to Consider • Exposure e.g., Free vs total plasma concentration e.g., Pharmacokinetics e.g., Metabolites • Species differences e.g., receptor / mechanism • Attenuating / augmenting factors e.g., multiple ion channel inhibition in the heart e.g., autonomic nervous system mediated effects / compensation • Risk:benefit assessment e.g., indication e.g., CV risk in patient population e.g., nature of CV effect e.g., development goal

  39. Integrated CV Risk Assessment • Derive margins for decision making and ranking compounds • Understand relationships between assays (eg QT at <hERG IC50)

  40. Therapeutic index (margin) concept • hERG safety margin • > 30 fold efficacious free Cmax vs hERG IC50 • (Webster et al. 2002) (Redfern et al. 2003) • Support for 30 fold hERG margin in relation to ventricular arrhythmia incidence in WHO-UMC database • (De Bruin et al. 2005) • In vivo safety margin • > 20 fold efficacious free Cmax vs EC10 • (Omata et al. 2005) • In summary, maximise margin to at least 30 fold hERG IC50 vs predicted efficacious free Cmax for serious diseases and at least 100 fold for less serious (benign) diseases

  41. Interpreting a QT integrated risk assessment • Inactive at hERG, no MAPD or QTc prolongation. Predicted clinical free Cmax is 0.2 to 0.4 uM • Calculate therapeutic index (TI) relative to human free Cmax • hERG TI = > 75 fold • MAPD TI = > 75 fold • In vivo TI = > 28 fold • Low risk of clinical QT prolongation • hERG IC50 = 3 uM, MAPD prolongation from 3 uM, QTc prolongation from 1.8 uM. Predicted clinical free Cmax is 0.2 to 0.4 uM • Calculate therapeutic index (TI) relative to human free Cmax • hERG TI = 8 to 14 fold • MAPD TI = 8 to 14 fold • In vivo TI = 5 to 8 fold • High risk of clinical QT prolongation

  42. Outline of lecture • Definition of safety pharmacology • Why is it important? • Role in Drug Discovery and Development • Drug induced QT prolongation • Integrating safety pharmacology data • Summary and Future perspective

  43. Summary of lecture • Safety pharmacology is a rapidly evolving discipline that embraces the principles of physiology, pharmacology and toxicology • Regulatory guidance and accepted industry practices promote a data-driven approach • There is a hierarchy of organ systems, with a primary focus on organ systems that are vital for life • There is more to safety pharmacology than the ‘QT issue’ • The role of safety pharmacology starts early in discovery and does not stop at FTIH

  44. Future perspectives • Computational modelling for cardiovascular safety prediction • Humanised safety screens e.g. stem cells • PK (TK) / PD modelling and simulation for improved data analysis, study design and prediction of probability of effect • Provision of repeat dose safety pharmacology data by inclusion of endpoints in repeat dose toxicology studies e.g. Holter-type ECG • Simultaneous assessment of multiple organ systems • Non-invasive imaging of organ function and correlation with pathological changes e.g. echo

  45. References and suggested reading • ICH website: • Bass A et al. (2004) Origins, practices and future of safety pharmacology. J Pharmacol Toxicol Methods 49, 145-51. • De Bruin ML et al (2005). Anti-HERG activity and the risk of drug-induced arrhythmias and sudden death. E Heart J 26, 590-597. • Fermini B & Fossa AA (2003) The impact of drug-induced QT interval prolongation on drug discovery and development. Nature Reviews: Drug Discovery. 2, 439-47. • Omata T et al (2005). QT PRODACT: comparison of non-clinical studies for drug-induced delay in ventricular repolarization and their role in safety evaluation in humans. J. of Pharm Sci 99, 531-541. • Porsolt RD et al. (2005) International Safety Pharmacology Guidelines (ICH S7A and S7B): Where do we go from here? Drug Dev Res 64, 83-89 • Redfern WS et al. (2002) Safety pharmacology – a progressive approach. Fund. Clin. Pharmacol. 16, 161-173. • Redfern WS et al. (2003) Relationships between preclinical cardiac electrophysiology, clinical QT interval prolongation and torsade de pointes for a broad range of drugs: evidence for a provisional safety margin in drug development. Cardiovasc. Res. 58, 32-45. • Reinhart GA et al (2005). Predictive, non-GLP models of secondary pharmacodynamics: putting the best compounds forward. C Opinion in Chem Biol 9, 392-399 • Scirica BM et al (2007). Effect of Ranolazine, an Antianginal Agent With Novel Electrophysiological Properties, on the Incidence of Arrhythmias in Patients With Non ST-Segment Elevation Acute Coronary Syndrome: Results From the Metabolic Efficiency With Ranolazine for Less Ischemia in Non ST-Elevation Acute Coronary Syndrome Thrombolysis in Myocardial Infarction 36 (MERLIN-TIMI 36) Randomized Controlled Trial. Circ 2007 116(15),1647-1652 • Stephens MDB (2004). In: “Stephens’ detection of new adverse drug reactions” fifth edition. Eds. J Talbot & P Waller. pp1-91. • Webster R et al (2002). Towards a drug concentration effect relationship for QT prolongation and torsades de pointes. C Opinion in Drug Disc and Dev 5, 116-126.