High-resolution peripheral quantitative computed tomography and finite element analysis of bone strength at the distal radius in ovariectomized adult rhesus monkey demonstrate efficacy of odanacatib and differentiation from alendronate.

Translational evaluation of disease progression and treatment response is critical to the development of therapies for osteoporosis. In this study, longitudinal in-vivo monitoring of odanacatib (ODN) treatment efficacy was compared to alendronate (ALN) in ovariectomized (OVX) non-human primates (NHPs) using high-resolution peripheral computed tomography (HR-pQCT). Treatment effects were evaluated using several determinants of bone strength, density and quality, including volumetric bone mineral density (vBMD), three-dimensional structure, finite element analysis (FEA) estimated peak force and biomechanical properties at the ultradistal (UD) radius at baseline, 3, 6, 9, 12, and 18 months of dosing in three treatment groups: vehicle (VEH), low ODN (2 mg/kg/day, L-ODN), and ALN (30 µg/kg/week). Biomechanical axial compression tests were performed at the end of the study. Bone strength estimates using FEA were validated by ex-vivo mechanical compression testing experiments. After 18months of dosing, L-ODN demonstrated significant increases from baseline in integral vBMD (13.5%), cortical thickness (24.4%), total bone volume fraction BV/TV (13.5%), FEA-estimated peak force (26.6%) and peak stress (17.1%), respectively. Increases from baseline for L-ODN at 18 months were significantly higher than that for ALN in DXA-based aBMD (7.6%), cortical thickness (22.9%), integral vBMD (12.2%), total BV/TV (10.1%), FEA peak force (17.7%) and FEA peak stress (11.5%), respectively. These results demonstrate a superior efficacy of ODN treatment compared to ALN at the UD radii in ovariectomized NHPs.

Effect of odanacatib on bone turnover markers, bone density and geometry of the spine and hip of ovariectomized monkeys: a head-to-head comparison with alendronate.

Odanacatib (ODN) is a selective and reversible Cathepsin K (CatK) inhibitor currently being developed as a once weekly treatment for osteoporosis. Here, effects of ODN compared to alendronate (ALN) on bone turnover, DXA-based areal bone mineral density (aBMD), QCT-based volumetric BMD (vBMD) and geometric parameters were studied in ovariectomized (OVX) rhesus monkeys. Treatment was initiated 10 days after ovariectomy and continued for 20 months. The study consisted of four groups: L-ODN (2 mg/kg, daily p.o.), H-ODN (8/4 mg/kg daily p.o.), ALN (15 µg/kg, twice weekly, s.c.), and VEH (vehicle, daily, p.o.). L-ODN and ALN doses were selected to approximate the clinical exposures of the ODN 50-mg and ALN 70-mg once-weekly, respectively. L-ODN and ALN effectively reduced bone resorption markers uNTx and sCTx compared to VEH. There was no additional efficacy with these markers achieved with H-ODN. Conversely, ODN displayed inversely dose-dependent reduction of bone formation markers, sP1NP and sBSAP, and L-ODN reduced formation to a lesser degree than ALN. At month 18 post-OVX, L-ODN showed robust increases in lumbar spine aBMD (11.4%, p<0.001), spine trabecular vBMD (13.7%, p<0.001), femoral neck (FN) integral (int) vBMD (9.0%, p<0.001) and sub-trochanteric proximal femur (SubTrPF) int vBMD, (6.4%, p<0.001) compared to baseline. L-ODN significantly increased FN cortical thickness (Ct.Th) and cortical bone mineral content (Ct.BMC) by 22.5% (p<0.001) and 21.8% (p<0.001), respectively, and SubTrPF Ct.Th and Ct.BMC by 10.9% (p<0.001) and 11.3% (p<0.001) respectively. Compared to ALN, L-ODN significantly increased FN Ct. BMC by 8.7% (p<0.05), and SubTrPF Ct.Th by 7.6% (p<0.05) and Ct.BMC by 6.2% (p<0.05). H-ODN showed no additional efficacy compared to L-ODN in OVX-monkeys in prevention mode. Taken together, the results from this study have demonstrated that administration of ODN at levels which approximate clinical exposure in OVX-monkeys had comparable efficacy to ALN in DXA-based aBMD and QCT-based vBMD. However, FN cortical mineral content clearly demonstrated superior efficacy of ODN versus ALN in this model of estrogen-deficient non-human primates.

Evaluation of high-resolution peripheral quantitative computed tomography, finite element analysis and biomechanical testing in a pre-clinical model of osteoporosis: a study with odanacatib treatment in the ovariectomized adult rhesus monkey.

This study aimed to validate finite element analysis (FEA) estimation of strength, identify high-resolution peripheral quantitative computed tomography (HR-pQCT) measures correlating with strength, and evaluate the precision of HR-pQCT measurements to longitudinally monitor effects of osteoporosis treatment in ovariectomized (OVX) non-human primates (NHPs). HR-pQCT images were acquired in three groups of NHPs: Intact (n=10), OVX-odanacatib treated (OVX-ODN 30 mg/kg, n=10) and OVX-vehicle treated (OVX-Veh, n=10) at the ultradistal (UD) and distal 1/3 radii and tibia at 12, 16 and 20 months. FEA estimates of bone strength using the Pistoia criterion were validated by ex-vivo mechanical compression (r(2)=0.95) of the UD radius. Single linear regressions of FEA-determined ultimate stress showed high correlation with HR-pQCT derived parameters: integral vBMD (r(2)=0.86), bone volume fraction (r(2)=0.84) and cortical thickness (r(2)=0.79). Precision of HR-pQCT measurements, obtained from an excised radius and tibia, showed low variation (CV=0.005%-5.6%) and helped identify possible sources of error. Comparison of OVX-Veh and Intact groups showed decreases in bone parameters demonstrating trends consistent with bone loss. Comparison of OVX-ODN and OVX-Veh groups showed a treatment effect with increases in bone parameters: integral vBMD (477±27 vs. 364±22 mgHA/cm(3)) and cortical thickness (Ct.Th) (0.90±0.07 vs. 0.64±0.04 mm) at the UD radius, Ct.Th (2.15±0.28 vs. 1.56±0.08 mm) at the distal 1/3 radius. Axial compression peak stress calculated and obtained experimentally showed the OVX-ODN group was 33% stronger than the OVX-Veh group. We conclude that HR-pQCT and FEA serve as robust techniques to longitudinally monitor bone parameters and strength in NHP's.

Inverse relationship between matrix remodeling and lipid metabolism during osteoarthritis progression in the STR/Ort mouse.

OBJECTIVE: The biologic changes associated with osteoarthritis (OA) are incompletely understood. The aim of this study was to elucidate the molecular mechanisms underlying OA progression in an STR/Ort murine model of spontaneous disease. METHODS: Global patterns of gene expression were assessed using microarray analysis of articular cartilage/subchondral bone from the tibial plateaus of STR/Ort mice at 3, 9, and 12 months of age. The age-dependent severity of osteophyte formation and extent of cartilage damage were determined in the corresponding femurs using microfocal computed tomography and the Mankin histologic scoring system. Pathway analysis was used to identify the functions of genes associated with OA progression, and changes in gene expression were confirmed using immunohistochemistry. RESULTS: Six hundred twenty-one genes were associated with both osteophyte formation and cartilage damage in the STR/Ort joints. Genes involved in the development/function of connective tissue and in lipid metabolism were most significantly enriched and regulated during disease progression. Genes directly interacting with peroxisome proliferator-activated receptor alpha (PPARalpha)/PPARgamma were down-regulated, whereas those genes involved with connective tissue remodeling were up-regulated during disease progression. Associations of down-regulation of myotubularin-related phosphatase 1 (a phosphoinositide 3-phosphatase involved in lipid signaling) and up-regulation of biglycan (a member of the small leucine-rich protein family known to modulate osteoblast differentiation and matrix mineralization) with OA progression were confirmed by immunohistochemistry. CONCLUSION: Since adipogenesis and osteogenesis are inversely related in the developing skeletal tissue, these results suggest that a shift in the differentiation of mesenchymal cells from adipogenesis toward osteogenesis is a component of the OA pathophysiologic processes occurring in the tibial plateau joints of STR/Ort mice.

Regulation of gene expression by lithium and depletion of inositol in slices of adult rat cortex.

Lithium inhibits inositol monophosphatase at therapeutically effective concentrations, and it has been hypothesized that depletion of brain inositol levels is an important chemical alteration for lithium's therapeutic efficacy in bipolar disorder. We have employed adult rat cortical slices as a model to investigate the gene regulatory consequences of inositol depletion effected by lithium using cytidine diphosphoryl-diacylglycerol as a functionally relevant biochemical marker to define treatment conditions. Genes coding for the neuropeptide hormone pituitary adenylate cyclase activating polypeptide (PACAP) and the enzyme that processes PACAP's precursor to the mature form, peptidylglycine alpha-amidating monooxygenase, were upregulated by inositol depletion. Previous work has shown that PACAP can increase tyrosine hydroxylase (TH) activity and dopamine release, and we found that the gene for GTP cyclohydrolase, which effectively regulates TH through synthesis of tetrahydrobiopterin, was also upregulated by inositol depletion. We propose that modulation of brain PACAP signaling might represent a new opportunity in the treatment of bipolar disorder.

The effect of an environmental enrichment device on individually caged rabbits in a safety assessment facility.

The primary enclosure of a laboratory animal's environment should encourage species-typical behavior and enhancement of the animal's well-being, as indicated by the Guide. Enrichment devices have been documented to decrease the incidence of stereotypical behaviors and increase overall activity of rabbits. An 8-week study was performed to evaluate the effect of an environmental enrichment device, stainless-steel rabbit rattles on spring clips, on individually housed rabbits in a Safety Assessment facility. We used 48 New Zealand White rabbits; the devices were placed on cages of 32 study rabbits, and 16 control rabbits had no devices. Food consumption measurements and observations of device manipulations (taken during a predetermined peak interaction 1-h timeframe) were collected 5 days per week. All rabbits were bled for evaluation of hematologic parameters for the stress triad (neutrophilia, lymphopenia, and eosinopenia) and weighed weekly. No significant differences were found between study and control rabbits when body weights, food consumption, and hematologic parameters were analyzed. Our study supports previous findings that interaction with enrichment devices decreases over time, thus indicating the need for frequent rotation of different enrichment devices. In addition, no adverse effects of the analyzed parameters were found, indicating that stainless-steel rabbit rattles on spring clips are suitable devices for safety assessment studies, in which the introduction of new variables is often unacceptable.