1. Festschrift in honour of Professor Peter Lees PK/PD modelling of NSAIDs in domestic animals The Royal Veterinary College Camden Campus: 22nd July 2010 PL Toutain UMR 181 Physiopathologie et Toxicologie Expérimentales INRA, ENVT ECOLE NATIONALE VETERINAIRE T O U L O U S E

2. 1795: Rev Edward Stone described the antipyretic properties of the willow 1897 1982 Nobel Prize for Medicine for his research on mechanism of action of NSAID (prostaglandins).

4. Modern history of veterinary NSAIDS: 1971 and beyond

5. Brander & Pugh (1977) No chapter on NSAIDs Originally these drugs (PBZ…) were synthesized in the days of antiseptic surgery as derivatives of phenol which might be capable of exerting internal antisepsis

6. Veterinary Pharmacology & Therapeutics No chapter on NSAIDs 1982

7. Veterinary Pharmacology & Therapeutics (Ninth Ed.) 2009

8. Historically, aspirin was not (appropriately) used in veterinary medicine Historically too expansive for large animals The doses recommended for small animals are too high. –Such recommendations for salicylates were rather constant in veterinary pharmacology handbooks in e.g. Germany, USA, Russia and Spain from 1900 up to the 70’s. The fallacy of the allometric rule

9. The fallacy of allometric scaling for Aspirin Extrapolation from man to animal using the Surface Law and Metabolic Body Weight was popular.

10. Simple allometry: the log-log transformation Y=aBW b Plasma Half-life Body weight

11. The fallacy of allometric scaling for Aspirin The principal reason for this lack of universal applicability is that allometry deals only with size; specifically, it does not address metabolic differences among species.

12. A double log plot of salycilate half-life in different species Body Weight (KG) Half-life (h)

13. The Lloyd E. Davis’ paper (1972) Introduction: “We believed that information relevant to the biotransformation and rates of disappearance from blood of several drugs in a series of large domestic animals might prove of value”

14. The Lloyd E. Davis’ paper on salicylate (1972)

15. The Lloyd E. Davis’ paper (1972) Conclusion: “the present data indicate the futility of extrapolating dose and dosage regimens from one species to another, as has been done in the past, in the treatment of domestic animals”

16. PK : Concepts and practice 1977

17. The main limiting factors to conduct PK studies in the late 1970’s During the 70's, most chemical separations were carried out using paper chromatography and thin-layer chromatography Only in the late 1970's, reverse phase liquid chromatography allowed for improved separation between very similar compounds

18. The main limiting factors to conduct PK studies in the late 1970’s By the 1980's HPLC was commonly used for the separation of chemical compounds. New techniques improved separation, identification, purification and quantification far above the previous techniques.. Improvements in type of columns and thus reproducibility were made as such terms as micro-column, affinity columns, and Fast HPLC began to immerge

19. The main limiting factors to conduct PK & PK/PD studies in the late 1970’s Late 70’: Analog computer 1976 1984 1994

20. Computer: The main limiting factors to conduct PK & PK/PD studies From Lisboa (2003) to Toulouse (2009)

21. Why to investigate NSAIDs in the early eighties

22. Why to investigate NSAIDS All domestic species suffer pain and controlling pain is a priority issue for veterinary pharmacologist Inflammation is a major source of pain –Acute (e.g. infectious) or chronic (e.g. osteoarthritis) To determine an adequate dosage regimen –Efficacy –Safety Selectivity (COX1 vs. COX2)

23. 1982 2009 Peter’s work from 1981 to 2010

24. The first Peter’s paper on PK of NSAIDs (1981)

25. Lack of allometric relationship for different NSAIDS in domestic species

27. Condition of the GI tract and oral PBZ absorption The presence of food in the stomach can have a marked and often unpredictable effect on drug absorption 24h 04 8 12 8 4 0 Hay at the time of administration and 5 h after Concentration (µg/ml) 16 12 8 4 Hay 5 h before and at the time of oral administration 24h 12

28. The today most cited Peter’s paper and the second most cited RVC paper

29. PK PD

30. PK/PD modelling of NSAIDs in domestic animals

31. Peter’s first PK/PD paper

32. What is PK/PD modeling? PK-PD modeling is a scientific tool to quantify, in vivo, the key PD parameters (efficacy, potency and sensitivity) of a drug, which allows to predict the time course of drug effects under physiological and pathological conditions (intensity and duration)

33. What is PK/PD modeling? PK/PD modeling is a versatile tool which is mainly used in veterinary medicine to select rational dosage regimens (dose, dosing interval) for confirmatory clinical testing.

34. Dose titration DoseResponse Black box PK/PD Dose PKPD Plasma concentration surrogate Response

35. ED 50 = ED 50 - is a hybrid parameter (PK and PD) - is not a genuine PD drug parameter Clearance x target EC 50 Bioavailability PD PK The determination of an ED 50 or any ED %

36. What kind of data for PK/PD modeling

37. Measuring response Measuring exposure Measuring variables in PK/PD trials Full concentration time curve AUC Cmax, Cmin Biomarkers Surrogate Clinical outcomes

38. Biomarker definition A characteristic that is objectively measured and evaluated as an indicator of normal biological processes, pathogenic processes, or pharmacologic responses to a therapeutic intervention  Markers of drug response  Markers of disease or physiological function

39. Requires  95% PGE2 inhibition EC 50 response EC 50 response >> EC 50 effect EC 50 in vivo effect EC 50 action whole blood assay Which dependent variable for PK/PD modeling ? NSAID plasma concentration Inhibition of COX Inhibition of PGE2 production Suppression of lameness

40. Biomarkers and surrogates in drug development Demonstrate the likely chance of efficacy/safety Demonstrate therapeutic response Internal decision making Registration dossier Learning Confirming Drug development Screening Biomarkers Surrogate Field clinical outcome Local temperature Pain modulation Binding affinity COX inhibition PGs production Lameness NSAID Wellbeing/Demeanor

41. Ex Vivo biomarker investigation: The tissue cage model

43. Development of equine models of inflammation (1987)

44. The tissue cage model PK investigations –Plasma: shallow compartment –Tissue cage: Deep compartment (size effect) –Influence of inflammation on local concentration of NSAIDs PD investigations

45. Flunixin plasma, exudate & transudate concentrations after an IV flunixin administration (1.1mg/kg) Exudate Transudate

46. The tissue cage model PK investigations PD investigations –Biological liquids for in vitro assays (transudat, exudates) –Ex vivo investigations (PK/PD integration) –In vivo investigation ( PK/PD modeling)

47. The tissue cage model: possible in vivo PK/PD modeling using tissue cage as a surrogate of biophase

48. Response Plasma concentration Body Medium concentratio n Test system Response In vivo In vitro Extrapolation in vitro  in vivo Mechanism- based PK/PD PK/PD: in vitro vs. in vivo

49. Robenacoxib selectivity

51. PK/PD applications 1.in vitro to in vivo extrapolation 2.identify key PD parameters (efficacy, potency, selectivity, affinity…) 3.predict dosage regimen 4.sources (PK or PD) variability in drug response (antibiotics)

52. Application of PK/PD to determine a dosage regimen for NSAIDs PBZ Flunixin Meloxicam Ketoprofen Meloxicam Nimesulide Tolfenamic acid COXIB Meloxicam Coxib Ketoprofen Tolfenamic acid

53. Modeling options regarding presence or not of a delay between PK and PD time development PK and PD delay NO YES No PK modeling PK modeling PK origin PD origin Indirect response model Effect compartment model E = Emax x C(t) model EC 50 + C(t) model Emax x C observed EC 50 + C observedl E =

54. Concentration vs time (C(t)) and effect vs time (E(t)) profiles Effect lags behind concentration  for a given concentration (1) there are 2 possible effects  this makes data analysis difficult Effect (Anticlockwise) hysteresis loop C(t) E(t) t1t1 t2t2 Time delay 1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6 Concentration or effect

55. Decision tree to select a PK/PD model according to the origin of the delay between the plasma concentration and observed effect.

56. The “effect compartment model” Dose 1:PK model Parametric (Exponential) Non parametric (Spline) 2:Link model Ke0 3:PD model Parametric (Emax, Hill) Non parametric (spline) Ke0 K 10 Cp(t) Ce(t) Time Concentration effect Ce Effect Effect(t) Time Effect

57. The “effect compartment model” Flunixin & Ketoprofen in horses Central 1 Peripheral 2 K21 K12 K10 Ke0 K1e Effect Fig 1: PK/PD model applied to the analysis of biological responses

58. Flunixin plasma, exudate & transudate concentrations after an IV flunixin administration (1.1mg/kg) Exudate Transudate

59. Freund adjuvant arthritis in horse Carpitis

60. PK / PD: flunixine

61. PD parameters for different NSAIDs PD parametersEfficacyPotencySensitivity DrugsEmax (cm)EC 50 (µg/mL) Slope PBZ13.63.6>5 Flunixin22.80.93>5 Meloxicam27.40.19>5

62. 8 0 16 0 4 812 1620 24 h Stride length (cm) 1 0.5 2 DOSE mg/kg PK/PD: Flunixine

63. 12 14 8 4 0 0 4812162024 Time(h) Stride length (cm) 1.25 1.0 1.5 2 4 DOSE mg/kg PK/PD: Phenylbutazone

64. A new class of PK/PD models

65. Mechanism-based PK/PD modeling in drug discovery Dose Response PKPD Plasma concentration Plasma concentration Drug receptor interaction Transduction Dose Response Drug specificity affinity intrinsic efficacy System specificity Pharmacogenomics

66. Complexity of model 1:Dose titration Dose Black box Response Dose PK Internal dose Plasma concentration as driving force into PD model Dose Biophase distribution PD Plasma Biosignal flux  loss  production Biomarker response Clinical response Biosensor process Transduction 2:Empirical PK/PD model 3:Semimechanistic model + - + - Feedback loop Disease progression

67. The building of PK/PD models PK model – transforming dose into concentration vs. time profile; Link model –describing transfer of the drug form plasma into the biophase; System model – that describes the physiological system or the pathological process on which the drug is acting; PD model –relating biophase concentration to an effect on the system. Statistical model –that describes the error component of the model and that is typically estimated in population PK/PD investigations.

68. An example of application of PK/PD to determine a dosage regimen for a NSAID in cat

69. As for a conventional dose titration, PK/PD investigations generally require a relevant experimental model (here a kaolin inflammation model) Possibility to perform PK/PD in patient

70. Measure of vertical forces exerted on force plate To measure the vertical forces, a corridor of walk is used with a force plate placed in its center. The cat walks on the force plate on leach. Video As for a conventional dose titration, PK/PD investigations require to measure some relevant endpoints

71. The measure of vertical force and video control are recorded  Vertical forces (Kg) Video Measure of vertical forces exerted on force plate

72.  descending, climbing and creeping time Surrogate endpoints: locomotion tests

73.  withdrawal time: timer stopped when cat withdraws its paw Surrogate endpoint for pain

74. Measure of pain with analgesiometer Cat is placed in a Plexiglas box. A light ray is directed to its paw to create a thermal stimulus. The time for the cat to withdraw its paw of the ray is measured.  withdrawal time of the paws (second) Video

75. dR dt = K in (1- ) - K out R I max + C n IC 50 n + C n PK/PD results: analgesic effect Emax/Imax IC50 Slope=n

76. Simulated dose-response: Robenacoxib: analgesic effect

77. Simulations Robenacoxib: once vs. twice a day Mean effect  32 %Mean effect  52 % Mean effect  96 %

78. Others reasons to prefer a PK/PD approach to a classical dose- titration? The separation of PK and PD variability

79. PK/PD variability Consequence for dosage adjustment PKPD Dose Plasma concentration Effect BODY Receptor Kidney function Liver function... Clinical covariables disease severity or duration pathogens susceptibility (MIC) PK/PD population approach

80. Coefficient of variation PK PD ClearanceVssEC 50 EC 50 antipyretic antiinflamatory Nimesulide17204962 Tolfenamic Ac.289.54748 Prednisolone121549 Interindividual pharmacokinetic and pharmacodynamic variability of Nimesulide, Tolfenamic Ac. and Prednisolone T. Haake, 1997

81. The future of the PK/PD modeling

82. Preclinical drug developmentClinical drug development Learning Drug discovery Approval Confirming 1.To acquire basic knowledge on drug 2.Extrapolation from in vitro to in vivo 3.To be an alternative to dose-titration studies to discover an optimal dosage regimen To adjust dosage regimen to different subgroups of animals (age, sex, breed, disease) Predictive PK/PD Simulations Trial forecasting Preclinical PK/PD Integrated information supporting go/no go decision Predicting Clinical PK/PD Population PK/PD

84. CONCLUSION The aim of veterinary pharmacology is to provide a rational basis for the use of drugs in a clinical setting