Abaloparatide, a novel PTH receptor agonist, increased bone mass and strength in ovariectomized cynomolgus monkeys by increasing bone formation without increasing bone resorption.

Abaloparatide, a novel PTH1 receptor agonist, increased bone formation in osteopenic ovariectomized cynomolgus monkeys while increasing cortical and trabecular bone mass. Abaloparatide increased bone strength and maintained or enhanced bone mass-strength relationships, indicating preserved or improved bone quality. INTRODUCTION: Abaloparatide is a selective PTH1R activator that is approved for the treatment of postmenopausal osteoporosis. The effects of 16 months of abaloparatide administration on bone formation, resorption, density, and strength were assessed in adult ovariectomized (OVX) cynomolgus monkeys (cynos). METHODS: Sixty-five 9-18-year-old female cynos underwent OVX surgery, and 15 similar cynos underwent sham surgery. After a 9-month period without treatments, OVX cynos were allocated to four groups that received 16 months of daily s.c. injections with either vehicle (n = 17) or abaloparatide (0.2, 1, or 5 µg/kg/day; n = 16/dose level), while Sham controls received s.c. vehicle (n = 15). Bone densitometry (DXA, pQCT, micro-CT), qualitative bone histology, serum calcium, bone turnover markers, bone histomorphometry, and bone strength were among the key measures assessed. RESULTS: At the end of the 9-month post-surgical bone depletion period, just prior to the treatment phase, the OVX groups exhibited increased bone turnover markers and decreased bone mass compared with sham controls. Abaloparatide administration to OVX cynos led to increased bone formation parameters, including serum P1NP and endocortical bone formation rate. Abaloparatide administration did not influence serum calcium levels, bone resorption markers, cortical porosity, or eroded surfaces. Abaloparatide increased bone mass at the whole body, lumbar spine, tibial diaphysis, femoral neck, and femoral trochanter. Abaloparatide administration was associated with greater lumbar vertebral strength, and had no adverse effects on bone mass-strength relationships for the vertebrae, femoral neck, femoral diaphysis, or humeral cortical beams. CONCLUSIONS: Abaloparatide administration was associated with increases in bone formation, bone mass and bone strength, and with maintenance of bone quality in OVX cynos, without increases in serum calcium or bone resorption parameters.

Effects of long term treatment with high doses of odanacatib on bone mass, bone strength, and remodeling/modeling in newly ovariectomized monkeys.

The objectives here were to evaluate the effects of odanacatib (ODN) at doses exceeding the clinical exposure on biomechanical properties of lumbar vertebrae (LV), hip and central femur (CF), and compare ODN to alendronate (ALN) on bone remodeling/modeling in ovariectomized (OVX) monkeys. Ten days post-surgery, animals were treated with vehicle (VEH), ODN-L (2mg/kg/day, p.o.), ODN-H (8/4mg/kg/day), or ALN (30µg/kg/week, s.c.) for 20months. An intact group was also included. ODN-L provided systemic exposures of 1.8-fold of clinical exposure. ODN-H started at 20-fold for 5.5months, and then reduced to 7.8-fold of clinical exposure, compared to ALN at approximated clinical exposure. From cross sectional analyses, LV density and peak load in ODN at both doses or ALN were not different from VEH or Intact. However, cortical thickness of femoral neck (FN) and CF in ODN were higher (21-34%, p<0.05) than VEH, due to smaller endocortical (Ec) perimeter of FN (10-11%; p<0.05) and CF (9-12%; ODN-L, p<0.05), and larger CF periosteal (Ps) perimeter (2-12%; ODN-H, p<0.001) versus VEH. ODN groups also showed slightly higher cortical porosity and Ps non-lamellar bone in CF. ODN-H treatment resulted in higher CF peak load (p<0.05) versus VEH. For all bone sites analyzed, a positive, linear relationship (r(2)=0.46-0.69, p<0.0001) of peak load to density or structural parameters was demonstrated. No treatment-related differences in the derived intrinsic strength properties were evidenced as compared between groups. ALN reduced all remodeling surfaces without affecting Ps modeling. Trabecular and intracortical remodeling were reduced in ODN groups, similar to ALN. Ec mineralizing surface in ODN-H trended to be lower than VEH by month 20, but Ec bone formation indices in ODN groups generally were not different from VEH. Ps modeling in ODN groups was significantly higher than other treatment groups. This study overall demonstrated the bone safety profile of ODN and its unique mechanism on cortical bone supporting the clinical application for osteoporosis treatment.

Skeletal health: primate model of postmenopausal osteoporosis.

Currently, the nonhuman primate is the most widely used large animal model to evaluate the safety and efficacy of new drug entities to treat or prevent estrogen-deficiency-induced bone loss and osteoporosis. Surgical ovariectomy (OVX) induces a state of high bone turnover and rapid bone loss establishing a new steady-state bone mass within 8-9 months. Many systems in the monkey are similar to humans, including skeletal and reproductive physiology and the immune system, making this a plausible model suitable to evaluate the effects of new bone drugs. The long-term sequelae following OVX and withdrawal of monthly exposure to cyclic reproductive hormones in older female monkeys (cynomolgus and rhesus) mimics estrogen depletion and postmenopausal bone loss occurring in women. Characterization of the primate model revealed an apparent limitation to the extent of bone loss. Animals lose bone mass after OVX, but the extent of the bone loss cannot be described as osteoporotic. The small differences between OVX and sham-operated controls in many important bone measurements is overcome by including 15-20 animals per group to provide adequate statistical power. The long-term, at least 16 month, bone safety studies performed to satisfy regulatory guidelines provide an opportunity to study treatment effects for an extended period not covered in shorter-term safety studies. In vivo end-points such as densitometry and biochemical markers translate easily to clinical use, while biomechanical end-points that cannot be measured clinically can be used to predict fracture prevention. To date, the monkey OVX model has been used to support submissions for many new drugs including anabolics, bisphosphonates and selective estrogen receptor modulators. Despite its limitations, the OVX monkey model remains the best characterized of the large animal models of osteopenia and has become integral to osteoporosis drug development.

Cancellous and cortical bone architecture and turnover at the iliac crest of postmenopausal osteoporotic women treated with parathyroid hormone 1-84.

Treatment with parathyroid hormone [PTH(1-84)] increases lumbar spine bone mineral density and decreases vertebral fractures, but its effects on bone microarchitecture are unknown. We obtained iliac crest biopsies from postmenopausal osteoporotic women given placebo (n=8) or 100 microg PTH(1-84) for 18 (n=8) or 24 (n=7) months to assess cancellous and cortical bone formation and structure. At 18 months, cancellous bone volume (BV/TV) measured by microcomputed tomography and histomorphometry was 45-48% higher in subjects treated with PTH(1-84) versus placebo, a result of higher trabecular number (Tb.N) and thickness. The higher Tb.N appeared to result from intratrabecular tunneling. Connectivity density was higher and structure model index was lower, indicating a better connected and more plate-like trabecular architecture. Cancellous bone formation rate (BFR) was 2-fold higher in PTH(1-84)-treated subjects, primarily because of greater mineralizing surface. Osteoblast and osteoid surfaces were a nonsignificant 58% and 35%, respectively, higher with PTH(1-84) treatment. Osteoclast and eroded surface were unaffected by PTH(1-84). There were no effects of PTH(1-84) treatment on cortical thickness, or endocortical or periosteal BFR, but cortical porosity tended to be higher. Although cancellous BFR was lower at 24 than at 18 months, measures of cancellous and cortical bone structure were similar at both timepoints. The bone produced by PTH(1-84) had normal lamellar structure and mineralization with no abnormal histology. In conclusion, when compared with placebo, treatment of osteoporotic women with PTH(1-84) was associated with higher BV/TV and trabecular connectivity, with a more plate-like architecture, all consistent with the lower vertebral fracture incidence.

Intratrabecular tunneling increases trabecular number throughout the skeleton of ovariectomized rhesus monkeys treated with parathyroid hormone 1-84.

Daily treatment of ovariectomized (OVX) adult rhesus monkeys with human parathyroid hormone (PTH) 1-84 for 16 months increases trabecular bone volume (BV/TV), number (Tb.N) and connectivity at lumbar vertebra-3 (L3) and thoracic vertebra-10. We proposed that the increased Tb.N and connectivity was achieved by stimulation of intratrabecular tunneling. Using histomorphometry to determine frequency of events, we have now quantified intratrabecular tunneling at L3 and extended it to investigate the effects of PTH(1-84) treatment on trabecular bone at the proximal femur, distal radius and iliac crest of these animals. At L3, tunneling frequency was low in control sham and OVX animals ( approximately 0.05/mm(2)) but increased significantly in PTH(1-84)-treated animals (0.27, 0.49 and 0.95/mm(2) with the 5, 10 and 25 microg/kg doses, respectively). Very similar tunneling frequencies were observed at all skeletal sites in all groups. Iliac crest biopsies were also collected at baseline and after 6 months of treatment and showed significant time- and dose-related increases in tunnels. Although the pattern and magnitude of response varied slightly from site to site, PTH(1-84) treatment significantly increased Tb.N, as well as BV/TV and bone formation rate at all skeletal sites. A modest but statistically significant increase in trabecular thickness occurred only at the iliac crest. In summary, intratrabecular tunneling is rare in control monkeys, but increased substantially with PTH(1-84) treatment. This phenomenon provides a plausible explanation for the PTH(1-84)-induced increase in Tb.N observed in OVX monkeys. Moreover, these analyses allowed a comparison of the effects PTH(1-84) treatment on trabecular bone at multiple locations.

Evaluation of cartilage and bone degradation in a murine collagen antibody-induced arthritis model.

The purpose of this work was to validate collagen antibody-induced arthritis (CAIA) model in two mice strains (Balb/c and CD-1) using clinical, biochemical, microstructural and histological techniques. We induced arthritis in mice using a cocktail of collagen type II (CII) antibodies followed by an injection with lipopolysaccharide (LPS) in different doses in Balb/c and CD-1 mice strains. Serum CTX-II levels were measured at study termination and correlated with microscopic severity of joint lesions as determined by a validated scoring systems. Bone involvement was assessed by microcomputer tomography (micro-CT). Balb/c mice developed rapid (day 6) and robust (100%) arthritis, whereas CD-1 mice showed only temporary macroscopic signs of disease. Serum CTX-II levels in Balb/c mice showed a significant increase in cartilage degradation in diseased animals (43-64% compared with non-diseased mice) and was decreased in animals receiving dexamethasone. Correlation of serum CTX-II with the microscopic score was statistically significant (P < 0.01). Micro-CT analysis demonstrated structural damage in bone in the CAIA Balb/c mice, which was prevented by dexamethasone. The CAIA-LPS model provides a useful supplement to currently available animal models of arthritis. This is a rapid onset and robust model; however, the choice of mouse strain should be evaluated carefully.

Effects of treatment with parathyroid hormone 1-84 on quantity and biomechanical properties of thoracic vertebral trabecular bone in ovariectomized rhesus monkeys.

Osteoporosis is characterized by impaired bone quality leading to increased susceptibility to fracture, particularly of the thoracic spine. However, the lumbar spine is studied most commonly. We investigated the effects of 16 months of treatment with full-length parathyroid hormone (PTH) 1-84 (5, 10, or 25 microg/kg) on bone mineral density (BMD) and on architecture and biomechanical properties of trabecular bone at the thoracic spine of ovariectomized (OVX) adult rhesus monkeys and compared the results with those from the lumbar spine. At baseline, 9 months after surgery, dual-energy X-ray absorptiometric BMD at T9-T12 was 7% lower in OVX than in sham animals. All PTH(1-84) doses increased BMD to sham levels within 7 months. Micro-computed tomography of T10 vertebrae showed that trabecular bone volume and connectivity were higher in PTH(1-84)-treated animals than in sham controls, primarily through a significantly greater trabecular number. Peripheral quantitative computed tomography of trabecular bone cores from T11 and T12 confirmed that PTH(1-84) increased BMD. Compression testing of the cores showed that PTH(1-84) treatment increased stiffness, modulus, yield load, and yield stress to levels significantly greater than in sham animals, with the largest effect in the 10 microg/kg group (35-54% greater than in OVX controls). Thus, PTH(1-84) treatment increased BMD and the biomechanical properties of trabecular bone at the thoracic spine of OVX rhesus monkeys. The 10 microg/kg dose produced the greatest effect on trabecular strength, possibly because the highest dose stimulated bone remodeling excessively. Importantly, the changes observed were similar to those in lumbar vertebrae, thereby validating extrapolation of results from the lumbar to the thoracic spine.

Effects of treatment of ovariectomized adult rhesus monkeys with parathyroid hormone 1-84 for 16 months on trabecular and cortical bone structure and biomechanical properties of the proximal femur.

Treatment of monkeys and humans with parathyroid hormone (PTH) 1-84 stimulates skeletal remodeling, which increases trabecular (Tb) bone mineral density (BMD) but decreases cortical (Ct) BMD at locations where these bone types predominate. We report the effects of daily PTH treatment (5, 10, or 25 microg/kg) of ovariectomized (OVX) rhesus monkeys for 16 months on bone structure and biomechanical properties at the proximal femur, a mixed trabecular and cortical bone site. PTH reversed the OVX-induced decrease in BMD measured by dual-energy X-ray absorptiometry at the proximal femur, femoral neck, and distal femur. Peripheral quantitative computed tomography confirmed a significant decrease in Ct.BMD and an increase in Tb.BMD at the total proximal femur and at the proximal and distal femoral metaphyses. The decrease in Ct.BMD resulted primarily from increased area because cortical bone mineral content was unaffected by PTH. Histomorphometry revealed that PTH significantly increased the trabecular bone formation rate (BFR) as well as trabecular bone volume and number. PTH did not affect periosteal or haversian BFR at the femoral neck, but cortical porosity was increased slightly. PTH had no effects on stiffness or peak load measured using a shear test, whereas work-to-failure, the energy required to fracture, was increased significantly. Thus, PTH treatment induced changes in trabecular and cortical bone at the proximal femur that were similar to those occurring at sites where these bone types predominate. Together, the changes had no effect on stiffness or peak load but increased the energy required to break the proximal femur, thereby making it more resistant to fracture.

Effects of daily treatment with parathyroid hormone 1-84 for 16 months on density, architecture and biomechanical properties of cortical bone in adult ovariectomized rhesus monkeys.

Treatment with parathyroid hormone 1-84 (PTH) or teriparatide increases osteonal remodeling and decreases bone mineral density (BMD) at cortical (Ct) bone sites but may also increase bone size. Decreases in BMD and increases in size exert opposing effects on bone strength. In adult ovariectomized (OVX) rhesus monkeys, we assessed the effects of daily PTH treatment (5, 10 or 25 microg/kg) for 16 months on BMD at the radial, tibial and femoral diaphyses, and on biomechanical properties (3-point bending) of radial cortical bone and the femoral diaphysis. PTH treatment did not affect areal BMD measured by dual-energy X-ray absorptiometry at the tibial diaphysis but caused a rapid, dose-related decrease at the distal radial diaphysis. Peripheral quantitative computed tomography at the radial and femoral diaphyses confirmed a significant PTH dose-related decrease in volumetric Ct.BMD caused primarily by increased cortical area. Significant increases in cortical thickness were the result of nonsignificant increases in periosteal length and decreases in endocortical length. Histomorphometry revealed increased endocortical bone formation at the tibial diaphysis and rib, higher Haversian remodeling at the rib and increased cortical porosity at the rib and tibia. Biomechanical testing at the femoral diaphysis showed that PTH treatment had no effect on peak load, but significantly decreased stiffness and increased work-to-failure (the energy required to break the bone). Similar changes occurred in radial cortical beams but only stiffness was changed significantly. Thus, PTH treatment of OVX rhesus monkeys decreased BMD and stiffness of cortical bone but did not affect peak load, likely because of increased bone size. However, PTH treatment increased the energy required to break the femur making it more resistant to fracture.

The RANKL inhibitor OPG-Fc increases cortical and trabecular bone mass in young gonad-intact cynomolgus monkeys.

UNLABELLED: Weekly treatment of gonad-intact cynomolgus monkeys (for up to 6 months) with the RANKL inhibitor OPG-Fc reduced bone turnover markers and increased volumetric cortical and trabecular BMD and BMC at radial and tibial metaphyses. OPG-Fc was well tolerated in this study without evidence of change in measured toxicologic parameters vs. control. INTRODUCTION: RANKL is the primary mediator of osteoclast formation, function, and survival. The catabolic effects of RANKL are inhibited by OPG, a soluble decoy receptor for RANKL. We investigated the safety and pharmacology of OPG-Fc in gonad-intact cynomolgus monkeys. METHODS: Males and females were treated weekly with vehicle (n = 5/sex) or OPG-Fc (15 mg/kg) by s.c. (n = 5/sex) or i.v. (n = 3/sex) injection for 6 months. RESULTS: Routine toxicologic investigations, hematologic parameters, body and organ weights, and ophthalmologic and electrocardiographic findings were not affected by OPG-Fc treatment. Because s.c. and i.v. dosing of OPG-Fc caused similar effects, these groups were combined for analyses. The following endpoints were significantly different in males and/or females treated with OPG-Fc relative to sex-matched vehicle controls after 6 months (p < 0.05). Biochemical markers of bone turnover (urine N-telopeptide and serum osteocalcin) were significantly decreased with OPG-Fc treatment. Cortical and trabecular volumetric BMD and BMC, cortical thickness, and cross-sectional moment of inertia were significantly increased by OPG-Fc treatment at the proximal tibia and distal radius metaphyses. Increases in cortical thickness were associated with significantly greater periosteal circumference. CONCLUSIONS: OPG-Fc increased cortical and trabecular BMD and BMC in young gonad-intact cynomolgus monkeys.

Daily treatment of aged ovariectomized rats with human parathyroid hormone (1-84) for 12 months reverses bone loss and enhances trabecular and cortical bone strength.

Most studies that have investigated the anabolic effects of parathyroid hormone (1-84) (PTH) or PTH fragments on the skeleton of ovariectomized (OVX) rats have evaluated the short-term effects of high-dose PTH(1-34) in young animals. This study used densitometry, histomorphometry, and biomechanical testing to evaluate the effects of 12-month daily treatment with low-dose PTH (15 or 30 microg/kg) in rats that were 10 months old at baseline, 4 months after OVX. Bone mineral density (BMD) and bone strength were reduced substantially in control OVX rats. The 15 microg/kg dose of PTH restored BMD to levels similar to those in sham animals within 6 months at the lumbar spine, distal and central femur, and whole body and maintained the BMD gain from 6 to 12 months. The 30 microg/kg dose produced greater effects. Both PTH doses normalized the trabecular bone volume-to-total volume ratio (BV/TV) at lumbar vertebra 3 but not at the proximal tibia (where baseline BV/TV was very low), solely by increasing trabecular thickness. PTH dose-dependently increased bone formation by increasing the mineralizing surface, but only the 30 microg/kg dose increased resorption. PTH increased cortical BMD, area, and thickness, primarily by increasing endocortical bone formation, and restored all measures of bone strength to levels similar to those in sham animals at all skeletal sites. PTH increased bone mass safely; there was no osteoid accumulation, mineralization defect, or marrow fibrosis and there were no abnormal cells. Thus, long-term PTH therapy normalized bone strength in the aged OVX rat, a model of postmenopausal osteoporosis, through increased bone turnover and enhanced formation of both trabecular and cortical bone.

The utility of measuring C-terminal telopeptides of collagen type II (CTX-II) in serum and synovial fluid samples for estimation of articular cartilage status in experimental models of destructive joint diseases.

OBJECTIVE: To characterize and validate a novel, enzyme-linked immunoassay for measuring cross-linked dimer forms of C-terminal telopeptides of type II collagen (CTX-II) in serum and synovial fluid of rodents, and investigate whether CTX-II measurements can reflect joint status in two established animal models of destructive joint diseases. METHODS: Firstly, the specificity, in vivo validity, antigen recovery, and reproducibility of the assay were investigated. Secondly, we induced arthritis in rats using either bovine collagen type II or mono-iodoacetate. CTX-II levels were measured in the serum and synovial fluid of the affected femoro-tibial joint and correlated with microscopic severity of joint lesions as determined by validated scoring systems. RESULTS: The F4601 monoclonal antibody (mAb) is highly specific for the EKGPDP sequence at the CTX-II. Strong CTX-II signals were detected during enzymatic degradation of articular cartilage explants by matrix metalloproteinase (MMP)-9 or MMP-13. The assay presented a good degree of precision and reproducibility (inter- and intra-assay CVs< 8.0%). In the collagen-induced arthritis (CIA) model, the assay indicated markedly increased levels of CTX-II in both the synovial fluid and the serum. Furthermore, CTX-II levels in both the synovial fluid (r = 0.76; P < 0.0001) and the serum (r = 0.85; P < 0.0001) showed strong correlations with the microscopic severity scores of joint lesions at Day 22. In the mono-iodoacetate-induced arthritis (MIA) model, CTX-II concentration in the synovial fluid (r = 0.53; P < 0.0001), but not in the serum, correlated with the microscopic severity score. CONCLUSIONS: The Preclinical CTX-II assay could provide a useful supplement to currently available methods for the non-invasive assessment of cartilage status. The utility of serum CTX-II to reflect joint status appeared to be limited to systemic forms of destructive joint diseases.

Intermittent intravenous administration of the bisphosphonate ibandronate prevents bone loss and maintains bone strength and quality in ovariectomized cynomolgus monkeys.

Using a clinically relevant regimen, this study investigated the effects of treatment with ibandronate, a highly potent nitrogen-containing bisphosphonate, on bone loss, biochemical markers of bone turnover, densitometry, histomorphometry, biomechanical properties, and bone concentration in aged ovariectomized monkeys. Sixty-six female cynomolgus monkeys, aged 9 years and older, were ovariectomized (OVX) or sham operated. Intravenous (iv) bolus injections of ibandronate at 10, 30, or 150 microg/kg or placebo were administered at 30-day intervals (corresponding to intervals of 3 months in humans), starting at OVX, for 16 months. OVX significantly decreased bone mass at the lumbar spine, proximal femur, femoral neck, and radius and increased bone turnover in a time-dependent manner, as assessed by dual energy X-ray absorptiometry, peripheral quantitative computed tomography, or histomorphometry. Ibandronate iv bolus injections administered at 30 microg/kg every 30 days prevented osteopenia induced by estrogen depletion. OVX-induced increases in bone turnover (as determined by activation frequency, bone formation rate, and biochemical markers of bone turnover, including urinary N-telopeptide and deoxypyridinoline excretion and serum values for osteocalcin and bone-specific alkaline phosphatase) were suppressed on treatment, and bone mass, architecture, and strength were preserved at clinically relevant sites. Treatment with high-dose (150 microg/kg/dose) iv bolus injections of ibandronate further increased bone mass and improved bone strength at both the spine and femoral neck, without adversely affecting bone quality. In contrast, treatment with a 10 microg/kg/dose only partially prevented the OVX-induced effects. These data support the potential for the long-term administration of ibandronate by intermittent iv bolus injections in humans to prevent osteoporosis and improve bone quality at clinically relevant sites.

Subchronic toxicity study of tetrahydroisohumulone and hexahydroisohumulone in the beagle dog.

Hops and hop extracts are approved and widely used bittering agents in the brewing of beer. During recent years, preisomerized alpha hop acids and reduced preisomerized alpha hop acids have been introduced as effective and economical bittering agents that may be added late in the brewing process. Although hops have been used for centuries, there are few studies in the literature on the safety of this ingredient. The study herein was conducted to determine the effects associated with subchronic oral administration of the reduced preisomerized hop acids, hexahydroisohumulone and tetrahydroisohumulone, in the dog. The results show that these materials are generally well tolerated in the dog. At high dose levels they induce vomiting, and much of the material administered was excreted in the faeces. The no-observed-adverse-effect level (NOAEL) of the compounds were 50 and 100 mg/kg body weight, respectively. Consumption of these ingredients by adult humans drinking 1 litre of beer daily is less than 0.25 mg/kg body weight; their use is thus associated with wide safety margins.

Pharmacokinetics and pharmacodynamics of TP-9201, a gpIIbIIIa antagonist, administered in combination with recombinant tissue-type plasminogen activator, heparin, and aspirin in beagles.

The effect of heparin, aspirin, and recombinat tissue-type plasminogen activator (rt-PA) on TP-9201 pharmacokinetics and pharmacodynamics was investigated in beagles. Animals received TP-9201, an Arginine-Glycine-Aspartic acid (RGD)-containing synthetic peptide glycoprotein (gp)IIbIIIa antagonist as a bolus of 0.31 mg/kg, followed by a 4-h infusion of 0.5 mg/kg/h. rt-PA was administered as a modification of the weight-adjusted standard regimen. Heparin was administered as a bolus followed by an infusion producing a 1.5- to 2-fold increase in the activated prothromboplastin time (aPTT) above baseline values. Aspirin was administered orally, approximately 24 and 2 h before TP-9201. TP-9201 had a plasma clearance of 9.9 +/- 2 ml/min/kg and a volume of distribution that was larger than plasma volume. Administration of heparin and aspirin with TP-9201 did not affect the clearance of TP-9201, whereas rt-PA resulted in a faster clearance (p = 0.05). Whether the faster clearance is physiologic or a result of rt-PA interference in the TP-9201 assay is unclear. TP-9201 completely inhibited ADP-mediated platelet aggregation. After discontinuation of TP-9201, recovery of platelet aggregation had a half life (t1/2) of 2-3 h and was complete < or = 24 h. Coadministration of heparin did not interfere with TP-9201 pharmacodynamics, whereas aspirin and rt-PA slowed the recovery of platelet aggregation. The template bleeding time profile for the TP-9201-treated animals was similar to that of the aspirin-treated animals.

Pharmacokinetics and pharmacodynamics of TP-9201, a GPIIbIIIa antagonist, in rats and dogs.

Because activation of the glycoprotein IIbIIIa (GPIIbIIIa) on platelets represents the final common pathway of platelet aggregation, inhibition of fibrinogen binding to the GPIIbIIIa complex provides an excellent target for inhibiting platelet aggregation. Peptides containing the arginine-glycine-aspartic acid (RGD) sequence have been shown to inhibit the binding of fibrinogen to the GPIIbIIIa receptor on platelets competitively. We studied the pharmacokinetics of TP-9201, a synthetic cyclic peptide containing the RGD sequence, in rats and dogs after a 24-h intravenous (I.V.) infusion at three doses. The mean plasma clearance of TP-9201 after intravenous infusions of 30, 150, and 600 mg/kg/day in rats was 20.2, 18.7, and 18.5 ml/min/kg, respectively. In beagles, TP-9201 clearance was 9.0, 7.5, and 7.3 ml/min/kg, corresponding to infusions of 10, 75, and 600 mg/kg/day, respectively. The volume of distribution was larger than plasma volume, and the terminal half-life (t1/2) was short in both species studied ranging from 0.5 to 0.7 h in rats and from 2.5 to 2.6 h in dogs. The results suggest that TP-9201 follows linear pharmacokinetics over the dose range studied. Despite the multiple blood sampling procedure used in the study, there were no hemorrhagic complications. Pharmacodynamic assessment in beagles showed that TP-9201 produces a dose-dependent inhibition of ADP-mediated platelet aggregation. The estimated in vivo IC50 value and sigmoidicity were 124 and 3.5 ng/ml, respectively, suggesting that TP-9201 is a potent GPIIbIIIa antagonist with a steep concentration-effect relationship. TP-9201 is rapidly cleared from the circulation on termination of the intravenous infusion. There is a corresponding reversal of platelet inhibition as TP-9201 is cleared from the circulation.

"What are they talking about? Is something wrong?" Information sharing during the second stage of labor.

Twenty postpartal women were shown videotapes of their second stage labors and simultaneously interviewed. During separate interviews, their 25 caregivers were also shown the videotapes and interviewed. The interviews were analyzed for major themes, one of which was sharing information during labor. Although women and caregivers appeared to agree about what information laboring women require and how it should be given, caregiver perceptions of the quality of their information giving were more positive than mothers' perceptions. Many women wanted more informational support, especially in alleviating unvoiced fears about their baby's health.

Analysis of antigen-induced changes in pulmonary mechanics in sensitized inbred rats.

An inbred line of rats was derived which develop marked and consistent dyspnea following sensitization and then exposure to aerosolized antigen. This pulmonary response was investigated in detail by determining forced pulmonary mechanics to derive respiratory rate, peak expiratory flow rate (PEFR), forced vital capacity (FVC), forced expiratory volume in 0.1 s (FEV0.1), and maximal midexpiratory flow rate (MMFR). Challenging anesthetized rats for 5 min with an aerosol of 3% egg albumin produced minimal change in respiratory rate, a 20% fall in PEFR, a 50% fall in FVC, and a 30% decrease in FEV0.1 and MMFR. The response could be inhibited or reversed by salbutamol (0.5 mg/kg, i.v.) and aminophylline (25 mg/kg, i.v.) administered either before or after challenge. The pulmonary changes are consistent with antigen-induced asthma in the rats. The response shows similarities to human asthma and may provide a relevant experimental model.