June 2004 Conclusion Slides

June 2004 Bone quality is an integral component of bone strength Maintaining or restoring bone architecture is required for optimal bone quality Bone turnover rate affects the degree of mineralization of bone Optimal collagen/mineral matrix properties contribute to bone quality Bone Quality

June 2004 Bone quality is an integral component of bone strength Maintaining or restoring bone architecture is required for optimal bone quality Bone turnover rate affects the degree of mineralization of bone Bone Quality

June 2004 Raloxifene: Summary of Bone Quality Effects Changes in BMD explain only a small proportion of vertebral fracture risk reduction shown with raloxifene Raloxifene reduces bone turnover to the premenopausal range allowing Repair of microdamage Preservation of heterogeneous mineral distribution A modest increase in mineralization

June 2004 Possible Contributing Factors to the Antifracture Efficacy of Antiresorptives Increase bone mineral density Decrease bone turnover Preserve bone microarchitecture Decrease number of remodeling sites Maintain trabecular thickness and connectivity Decrease number of trabecular perforations

June 2004 Biochemical markers and bone turnover significantly reduced to premenopausal range Normal bone turnover allows adequate repair of microdamage No adverse effect on bone histology Bone Quality Raloxifene

June 2004 Weinstein RS, et al. J Bone Miner Res. 14:S279; 1999 Prestwood KM, et al. J Clin Endocrinol Metab. 85: ; 2000 Ott SM, et al. J Bone Miner Res. 17: ; 2002 Bone Quality Raloxifene Histomorphometry No woven bone No marrow fibrosis No mineralization defect No cellular toxicity (light microscopy) Normal histologic appearance

June 2004 Bone Quality Raloxifene No adverse effects on bone histology Changes in BMD explain only a small proportion of vertebral fracture risk reduction Reduces bone turnover to the normal premenopausal range A moderate increase in mineralization and preservation of heterogeneous mineral distribution Long-term efficacy with sustained fracture reduction in the fourth year of treatment Favorable effects on femoral neck geometry

June 2004 Architecture Increase trabecular thickness and connectivity Increase cortical thickness and improves cortical geometry Favorable effects on femoral neck geometry Turnover Increase formation on quiescent (neutral) surface Increase in formation is greater than resorption (positive bone balance) Transient increase in cortical porosity without impact on bone strength Damage Accumulation Forms new bone Increased bone turnover reduces damage accumulation Bone Quality Conclusions Teriparatide

June 2004 Architecture Increase trabecular thickness and connectivity Increase cortical thickness and improves cortical geometry Favorable effects on femoral neck geometry Turnover Increase formation on quiescent (neutral) surface Increase in formation is greater than resorption (positive bone balance) Transient increase in cortical porosity without impact on bone strength Bone Quality Conclusions Teriparatide

June 2004 Turnover Reduction Within normal physiologic range Preservestrength Decrease resorption cavities Decrease stress risers Decrease perforations Maintain Horizontal struts Maintain Plate-like structure

June 2004 Excessive Turnover Reduction Below normal physiologic range Increasedfragility Insufficient fatigue damage repair Microcrack accumulation Microcrack propagation Prolonged secondary mineralization Excessive mineralization + homogeneous bone ?

June 2004 Osteoporosis Severe Osteoporosis Normal Courtesy Dr. A. Boyde

June 2004 Physiological Range Sourced from Weinstein RS, J Bone Miner Res , 2000 What Is the Optimal Reduction in Bone Turnover for an Antiresorptive Drug? Bone Strength Bone Turnover Excessive turnover Increase in stress risers (weak zones) Increase in perforations Loss of connectivity Insufficient turnover Accumulation of microdamage Increased brittleness due to excessive mineralization

Summary of Bone Quality Effects of Raloxifene and Teriparatide RaloxifeneTeriparatide Cortical geometryProtectImprove Trabecular microarchitectureProtectImprove TurnoverDecreaseIncrease Bone balanceNormalPositive MineralizationNormalFresh bone Mineral heterogeneityNormalIncrease Microdamage Collagen cross-links Osteocyte apoptosis Decrease ? Decrease Decrease? Younger Decrease June 2004

The Assessment of Bone Quality - Advances in Technology

June 2004 Cadaver Vertebrae: FEM vs. BCT Experiments QCT Compressive strength (kN) QCT-BMD x A min (mg/mm) r 2 =0.65, SE=1.11 kN Crawford et al, Bone 2003 Strength (kN) BCT ORS QCT-BMD xA (mg/mm) min Model Strength (kN) June 2004

Virtual Bone Biopsy Wrist detection coils Microscopy-specific MRI scanner software enhancements 3D image processing and analysis

June 2004 Supplemental Slides

June 2004 The Effect of Antiresorptive Therapy on Fracture Healing Study Protocol Cao Y et al. J Bone Miner Res 17: ; 2002 Female OVX rats (n=140) Five study groups Sham control OVX placebo control OVX + estrogen OVX + raloxifene OVX + alendronate Objective: To evaluate the effect of antiresorptives on fracture healing.

June 2004 The Effect of Antiresorptive Therapy on Fracture Healing External Callus Formation Reproduced with permission from Cao Y et al. J Bone Miner Res 17: , Weeks Callus formation Fracture visible 16 Weeks OVX Fracture line dissapeared ALN fracture line still visible Callus width largest in ALN group Fracture repair was delayed with ALN treatment

The Effect of Antiresorptive Therapy on Fracture Healing Photomicrographs of the Callus Reproduced with permission from Cao Y et al. J Bone Miner Res 17: , 2002 ShamOVXEE2RLXALN June 2004

Urinary Markers of Bone Resorption MarkerAbbreviation HydroxyprolineHYP PyridinolinePYD DeoxypyridinolineDPD N-terminal cross-linking telopeptide of type I collagenNTX C-terminal cross-linking telopeptide of type I collagenCTX Delmas PD. J Bone Miner Res 16:2370; 2001

June 2004 Serum Markers of Bone Turnover Abbreviation Formation Bone alkaline phosphatase ALP (BSAP) OsteocalcinOC Procollagen type I C-propeptidePICP Procollagen type I N-propeptidePINP Resorption N-terminal cross-linking telopeptide of type I collagen NTX C-terminal cross-linking telopeptide of type I collagenCTX Tartrate-resistant acid phosphataseTRAP Delmas PD. J Bone Miner Res 16:2370, 2001

Effect of Size on Areal BMD BMC 111 AreaBMD “True” Value = 1 g/cm 3 Adapted from Carter DR, et al. J Bone Miner Res 1992

June 2004 Local Buckling