The Negative BMU Balance Mean wall thickness (µm) Women 20 40 60 80 Age (yr) Ac. F /yr) 4 2 3 1 Remodeling rate Vedi et al 1982 Erickson et al 1999 The Negative BMU Balance 10 50 90 20 40 60 80 Formation by BMU Resorption by BMU Lips et al 1979 Mean wall thickness (µm) Three abnormalities compromise bone material and structure

Cort Trab 90% 45% 55% 10% 50-64 65-79 80+ Cort Trab Perimeter available for remodeling (m) 2.5 2 Cort 1.5 1 Trab 0.5 <50 60-79 80 + mgHA/yr Age (yrs) 5 Amount of bone lost from the cortical and trabecular compartments 4 Cort 3 2 Trab 90% 1 45% 55% 10% Zebaze et al 2010 50-64 65-79 80+

The Four Envelopes of Bone Periosteal Intracortical Endocortical Trabecular

Treat BMD Higher density of a decreasing Bone Volume Untreated Perturbed Steady State Restored, Slower Higher density of a decreasing Bone Volume BMD Structure more compromised if a weaker remodeling suppressant used because residual tissue level remodeling with the negative BMU balance in more BMUS despite treatment decays bone Untreated Treat Structural decay

Weiss et al Drug Metab Distribut 2006;36:2043 Trabecular Bone High Surface/Volume Configuration Accessible to remodeling and treatment C14 Zoledronic Acid Distribution Tibia Vertebrae Skull days --16 16 48 80 112 144 176 208 240 25 50 75 100 nmol/g DRUG Weiss et al Drug Metab Distribut 2006;36:2043

Cortical Bone Low Surface/Volume Endocortical surface Less Access

HORIZON-PFT Study 2301 Slide Library Bone 49 (2011) 128–132 HORIZON-PFT Study 2301 Slide Library V3 1-May-07 BP on bone surfaces 1-2 2-3 3-4 Weeks High Affinity ALN 2.4 Low affinity RISED 1.2 -20 -40 -60 -80 L4 trabec BFR % control Mararachia et al Bone 1996;19:281 Allen et al Bone 2011;49:128 CONFIDENTIAL

Penetration into Bone Matrix High Affinity Compound Low Affinity Compound Turek et al Calcif Tissue Int 2012;90:202

Mice constitutively activated PTH/PTHrP receptor have high porosity Cortical porosity (%) Cortical vBMD (mg/cm2) 1350 1250 1150 \ 1050 OPG ALN ZOL Vehicle Cortical porosity (%) 6 4 2 *** OPG ALN ZOL Vehicle 0 2 4 6 8 Toughness (MPa) 0 2 4 6 8 Cortical porosity (%) 15 10 5 OPG** ALN ZOL Vehicle OPG** 0 2 4 6 8 8 6 4 2 Cortical porosity (%) Femur energy to failure (Nmm) **relative to vehicle ALN ZOL Vehicle Ohishi et al Am J Pathol 2009;174:2160

Antiresorptive Therapies and the Surface Extent of Remodeling Reflected in the Mineralizing Surface MS/BS (%) 10 Normal 3 10 25 50 mg Bone H et al JBMR 2010 Placebo Odanacatib 2 4 6 8 % 10 Pennypacker et al JBMR 2011 Ovx+L-235 2 mg/kg 10 mg/kg Ovx Ovx+ALN *Sham BFR/BS Vertebral Cancellous Bone, rabbits 120 100 80 60 40 20 L-235 % 8 6 4 Ris Ibn Zol Aln DMab 2 Recker JBMR 1988;31:133 Eriksen Bone 2002;31:620 Chavassieux JCI 1997;100:1475 Recker OI 2004;15:231 Recker JBMR 1008;23:6 Reid JBMR 2010

Restored, same number, more shallow BP = fewer, same depth? Steady State Perturbed Restored, same number, more shallow BMD Steady state remodeling restored. Whether there is bone loss, no loss or gain depends on bone balance. Structure more compromised if a weaker remodeling suppressant used because residual tissue level remodeling with the negative BMU balance in more BMUS despite treatment decays bone Untreated Treat Structural decay

20 16 12 8 4 Prox Femur Trab Bone Prox Femur Endocort Surface 75 50 25 0.8 0.4 100 60 20 Veh 6 30 mg/kg 6 4 2 1.2 0.6 16 8 Veh 6 30 mg/kg Fem. Neck Trab Bone Veh 6 30 mg/kg Haversian Canal Surface 25 20 15 10 5 1.5 1.0 0.5 p=0.05 MS/BS (%) p<0.001 p<0.01 p<0.005 1.0 0.8 0.6 0.4 0.2 p<0.05 MAR (µm/d) 60 30 Explain terms In the trab cpt at the PF reduction in remodelling intensity in the Rx gp cf vehicle which reached sig in 30mg/kg gp While for MAR there was a reduction only in the 6mg/kg gp This leads to reduced BFR in both Rx groups 6mg/kg group due to reduced MAR 30mg/kg group due to reduced remodelling intensity 100 50 p<0.05 BFR (µm3/µm3/yr) p=0.05 p<0.001 p<0.005 p<0.01 Veh 6 30 mg/kg p values refer to difference relative to vehicle 13

Vehicle OD 30 mg/kg 0.8 0.4 Periosteal Surface Proximal Femur Femoral Neck 30 20 10 50 25 Vehicle MS/BS (%) 0.8 0.4 p<0.05 0.3 0.2 0.1 MAR (µm/d) OD 30 mg/kg 30 20 10 120 60 p<0.01 p<0.05 BFR (µm3/µm3/yr) p values refer to difference relative to vehicle 14

Ronacalerat – Ca Receptor Antagonist 6 8 10 12 4 2 --2 % Change BL M6 M12 BL M6 M12 -4 -2 2 4 6 LS aBMD Total Hip aBMD % Change TERI TERI ALN ALN PBO RONA RONA PBO 160 120 80 Time (h) 40 200 1 2 3 4 5 6 7 8 Intact PTH (mg/L) Sept 3rd: MW Comments: Verifying Data. RONA ALN PBO Fitzpatrick et al JBMR 2011