Preclinical Models of Drug Efficacy and Skeletal Toxicity René Rizzoli M.D. Division of Bone Diseases [WHO Collaborating Center for Osteoporosis and Bone Diseases] Geneva University Hospital Geneva, Switzerland

Guidelines Main objectives (1) FDA 1994 Opportunity to directly examine bone mass, architecture and strength WHO 1998 To establish the relationship between the effects of an intervention To establish the relationship between the effects of an intervention on bone mass and bone strength CPMP 2001 Documentation of drug-induced effects on bone architecture and strength Preclinical Studies

Guidelines Main objectives (2) FDA 1994 To demonstrate that long term treatment will not lead to deleterious effects on bone quality WHO 1998 To establish the effects of long term exposure on the quality of skeletal tissue CPMP 2001 Important component of the initial efficacy and safety assessment Preclinical Studies

Guidelines Main objectives (3) FDA 1994 WHO 1998 To elucidate the mechanism of action of a pharmaceutical agent and thus provide the rationale for its use in humans ______ To examine the effects of an intervention on fracture repair CPMP 2001 Preclinical Studies

Preclinical Studies: Specific Issues SpeciesSpecies Study DesignStudy Design Reflective of Clinical Situation (Prevention/Treatment) Treatment Schedule (Continuous/Intermittent) DosesDurationVariables (Mass, Density, Architecture, Histology, Biomechanics, Remodeling)

Predictive values of preclinical studies As far as the animal model chosen pertaines to the clinical situation for which the drug is evaluated, the results of preclinical studies (relation BMD-strength; bony tissue tolerance) are highly predictive of clinical outcome for most, if not all, drugs tested

Alendronate Reduces the Risk of Morphometric Vertebral Fractures Without VFxWith VFx Incidence (%) per year r Placebo Alendronate Reduction = 44% p = Reduction = 47% p < Vertebral Fracture Status at Baseline Cummings SR, et al. JAMA. 1998; 280: Black DM, et al. Lancet. 1996; 348: BMD Bone Strength Alendronate Increases BMD and Bone Strength in Baboon Vertebrae Balena et al., JCI 92: ,1993

Risedronate Increases Vertebral Bone Strength Control2.5mg/kg/d MPa * Dufresne, et al, JBMR 2001; 16 (Suppl 1): S404. Minipig Vertebrae Effect of Risedronate on Radiographic Vertebral Fractures Years 0-3 PBORISPBORIS 41%Reduction P < %Reduction P < % of Patients with Fracture 1 Harris et al. JAMA. 1999;282:1344– Reginster JY. Osteoporos Int. 2000;11:83–91.

Turner et al Raloxifene Preserves Bone Strength in the Ovariectomized Rat Breaking Force (N) * * Sham OVX RLX Vertebrae Effect of Raloxifene Treatment In Women With or Without Existing Fractures Placebo RLX 60 No Existing Fractures ExistingFractures % Patients with Incident Fracture RR 0.5 (0.3, 0.7) RR 0.7 (0.6, 0.9) * * Ettinger et al Vertebral Deformity

rhPTH(1-34) Increases Strength of Monkey Vertebrae Yield Force (N) * *†*† * Sato et al. Osteoporos Int 2001 ShamOVXPTH1PTH Placebo PTH 20 PTH 40 Patients (%) with  1 Fracture *P<0.001 rhPTH(1-34) Reduces the Risk of New Vertebral Fractures RR 0.35 (95% CI, 0.22, 0.55)* RR 0.31 (95% CI, 0.19, 0.50)* Neer et al. NEJM 2001

Strontium ranelate (mg/kg/d) Compression Test of Vertebra (L4) * Ultimate Strength (N) Mean ± SEM. * p<0.05 vs control group CUMULATIVE INCIDENCE OF PATIENTS WITH NEW VERTEBRAL FRACTURE * P < Placebo SR st 1 st 2 nd 3 rd Year * * * % patients Relative Risk of vertebral fracture: - 41%

Preclinical Models of Drug Efficacy and Skeletal Toxicity Failure to Evaluate Bone Strength in Preclinical Efficacy Assessment Ex. Fluoride Salts 1.Major Increase in BMD of the Axial Skeleton, but No Reduction in Vertebral Fracture Risk (Hagenhauer et al, 2001) 1.No Significant Improvement of Bone Strength in Various Animal Models (Sogaard et al, 1995, Lafage et al, 1995, Turner et al, 1996)

Animal studies Clinical Trials BMD Bone Strength BMDReduced Fracture Rate Etidronate + + ? (Mineralization ? (MineralizationDefect)+Notobserved Alendronate + + Risedronate RaloxifeneFluoride + Not improved Notobserved hPTH StrontiumRanelate

Guidelines Impact on clinical study timing FDA 1994 Submission of final reports from studies in rats and non rodents after phase III, between Pre-NDA meeting and submission of NDA WHO 1998 Well documented preclinical evaluation generally appropriate before phase III. Evaluation before start of clinical program should include pharmacodynamic and bone tolerance data CPMP 2001 Studies in OVX rats and in the second animal model should be timed so as to provide guidance for phase II and support for phase III, resp. Preclinical Studies

Guidelines Impact on clinical study program FDA 1994 Bone quality “normal” or “abnormal“ determines : - Drug approval for marketing - Duration of controlled studies (phase III) - Duration of phase IV open studies WHO 1998 Bone quality “normal” or “uncertain”, and mechanism of action well- or ill-understood determine: - End points (biomark. or BMD) for dose selection in phase II - Entering phase II - BMD or Fx may be appropriate end-point in phase III CPMP 2001 No impact Preclinical Studies

Preclinical Models of Drug Efficacy and Skeletal Toxicity Issues to be Clarified 1.Relation Bone Mass - Bone Strength (How to Detect an Exeption)

proximal tibia BMD (mg/cm2) * ° ° * * * Proximal tibia BV/TV (%) * *° ¥ BFR/BS (µm3/µm2/d) BMD, Cancellous Bone Volume and Bone Formation Rate in Adult Female Rats Treated with the SERM MDL103,323 or the Bisphosphonate Pamidronate at Doses Similarly Increasing Bone Strength (Bourrin et al., Bone 2002) SHAM OVX OVX OVX + MDL+ Pam + MDL+ Pam SHAM OVX OVX OVX + MDL+ Pam + MDL+ Pam SHAM OVX OVX OVX + MDL+ Pam + MDL+ Pam

Preclinical Models of Drug Efficacy and Skeletal Toxicity Issues to be Considered 1.Relation Bone Mass - Bone Strength (How to Detect an Exeption) 2. Heterogeneity of Action within a Drug Category

Vertebral Strength SHAM OVX OVX OVX HMR RAL HMR RAL mg/kg BW mg/kg BW SHAM OVX OVX OVX HMR RAL HMR RAL mg/kg BW mg/kg BW Serum IGF-I Serum IGF-I * * The Decrease in Bone Mass and Bone Strength Induced by Ovariectomy is corrected by the SERM HMR 3339 Ammann et al, ASBMR 2002

Preclinical Models of Drug Efficacy and Skeletal Toxicity Issues to be Considered 1.Relation Bone Mass - Bone Strength (How to Detect an Exeption) 2.Heterogeneity within a Drug Category 3.Safety Window (Anabolic Agents: Dose x 5)

Preclinical Models of Drug Efficacy and Skeletal Toxicity Issues to be Considered 1.Relation Bone Mass - Bone Strength (How to Detect an Exeption) 2.Heterogeneity within a Drug Category 3.Safety Window (Anabolic Agents: Dose x 5) 4.Integration of Preclinical Studies in the Drug Development Strategy (Complementarity, Definition of Study Design Including End-Points, Population)

Strategies for drug development in osteoporosis according to the 1998 WHO guidelines PreclinicalPhase IIPhase III Quality of bone normalValidated biochemical indicesBMD may be an of turnover appropriate for dose appropriate Mechanism of action selectionend-point Understood Quality of bone normalBone mineral measurementsFracture may be a to assess dosenecessary end- Mechanism of action point ill-understood Quality of bone uncertainBMD and other end-pointsFracture is an appropriateappropriate Mechanism of action end-point understood Quality of bone Unlikely to enter phase II abnormal or uncertain Mechanism of action ill-understood

Preclinical Models of Drug Efficacy and Skeletal Toxicity Focus on Bone Strength Measured at Various Skeletal Sites Looking at Consistency in the Relation with Bone Mass/DensityBone Mass/Density GeometryGeometry MicroarchitectureMicroarchitecture RemodelingRemodeling HistologyHistology

GuidelinesAnimal Models: Study Design FDA 1994 Reflective of clinical indication - Preventive - Curative Treatment schedule (continuous vs intermittent) should be the same as that intended for clinical use WHO 1998Idem FDA 1994 It should establish a rationale for the type of treatment schedule used later in humans CPMP 2001 Idem FDA 1994 Preclinical Studies

Guidelines Animal Models: Study Design. Duration FDA 1994 Based on bone turnover: Primates: 16 months Rats: 12 months WHO 1998 Based on phase III duration Large animal: 1/2 time selected for phase III evaluation Rats: 1/4 time selected for phase III evaluation CPMP 2001 Based on bone turnover: Rat and large animals: at least 6 remodeling cycles Preclinical Studies

Guidelines Animal studies FDA 1994 Bone mass/density measurement Analysis of bone architecture /histology Biomechanical testing of bone strength Biochemical markers of bone turnover WHO 1998 Similar recommendations but more detailed than FDA Fracture healing evaluation CPMP 2001 Similar recommendations but less detailed than FDA 1994 Preclinical Studies

Data on Fracture Risk might not be Required Before First Registration 1.For a New Agent Provided: -Antifracture Efficacy has been Demonstrated with an Agent of the Same Category -Similar Changes in BMD and Bone Turnover in Patients Compared to this Agent -Similar Changes in Bone Strength in Animal Models -Similar Profile of Bone Safety 2.Combined Therapy (2 Antiresorptives, 1 Anabolic + 1 Antiresorptive) Provided: -Antifracture Efficacy Demonstrated for both Agents -Higher Bone Strength with the Combined Therapy than with one Agent Alone -Similar Profile of Bone Safety

Predictive values of preclinical studies The results of animals studies were able to predict whether changes in bone mass and/or bone mineral density will be associated with modifications in bone fragility and therefore in fracture rate in osteoporotic patients

Guidelines Animal Models: Species FDA 1994 Two species are required: 1.Adult ovariectomized rats 2. Larger remodeling species WHO 1998 Idem FDA other rodent and non rodents models according to the type of osteoporosis CPMP 2001 Idem FDA 1994 Preclinical Studies