Antagonists of the calcium receptor. 2. Amino alcohol-based parathyroid hormone secretagogues.

When administered as a single agent to rats, the previously reported calcium receptor antagonist 3 elicited a sustained elevation of plasma PTH resulting in no increase in overall bone mineral density. The lack of a bone building effect for analogue 3 was attributed to the large volume of distribution (V(dss)(rat) = 11 L/kg), producing a protracted plasma PTH profile. Incorporation of a carboxylic acid functionality into the amino alcohol template led to the identification of 12 with a lower volume of distribution (V(dss)(12) = 1.

An orally active calcium-sensing receptor antagonist that transiently increases plasma concentrations of PTH and stimulates bone formation.

Daily subcutaneous administration of exogenous parathyroid hormone (PTH) promotes bone formation in patients with osteoporosis. Here we describe two novel, short-acting calcium-sensing receptor antagonists (SB-423562 and its orally bioavailable precursor, SB-423557) that elicit transient PTH release from the parathyroid gland in several preclinical species and in humans. In an ovariectomized rat model of bone loss, daily oral administration of SB-423557 promoted bone formation and improved parameters of bone strength at lumbar spine, proximal tibia and midshaft femur.

Treatment with a potent cathepsin K inhibitor preserves cortical and trabecular bone mass in ovariectomized monkeys.

The cysteine protease cathepsin K is involved in osteoclast-mediated bone resorption. We evaluated the effect of daily oral dosing of an inhibitor of human cathepsin K (SB-462795 [relacatib]) for 9 months on bone turnover, mass, and architecture in estrogen-deficient cynomolgus monkeys. Ovariectomized animals were treated orally with relacatib at 1, 3, or 10 mg/kg/day, or oral vehicle plus alendronate at 0.

Leucocyte cathepsin K affects atherosclerotic lesion composition and bone mineral density in low-density lipoprotein receptor deficient mice.

Aims: Cathepsin K (CatK), an established drug target for osteoporosis, has been reported to be upregulated in atherosclerotic lesions. Due to its proteolytic activity, CatK may influence the atherosclerotic lesion composition and stability. In this study, we investigated the potential role of leucocyte CatK in atherosclerotic plaque remodelling.

Efficacy and safety of the oncolytic herpes simplex virus rRp450 alone and combined with cyclophosphamide.

Oncolytic herpes simplex virus (oHSV) mutants are under development as anticancer therapeutics. One such vector, rRp450, is ICP6-deleted and expresses a prodrug enzyme for cyclophosphamide (CPA) (rat CYP2B1). Little is known about rRp450's toxicity profile, especially in combination with CPA.

Preconceptual administration of an alphavirus replicon UL83 (pp65 homolog) vaccine induces humoral and cellular immunity and improves pregnancy outcome in the guinea pig model of congenital cytomegalovirus infection.

Development of a vaccine against congenital cytomegalovirus (CMV) infection is a major public health priority. We report the use of a propagation-defective, single-cycle, RNA replicon vector system, derived from an attenuated strain of the alphavirus Venezuelan equine encephalitis virus, to produce virus-like replicon particles (VRPs) expressing GP83, the guinea pig CMV (GPCMV) homolog of the human CMV pp65 phosphoprotein. Vaccination with VRP-GP83 induced antibodies and CD4(+) and CD8(+) T cell responses in GPCMV-seronegative female guinea pigs.

A highly potent inhibitor of cathepsin K (relacatib) reduces biomarkers of bone resorption both in vitro and in an acute model of elevated bone turnover in vivo in monkeys.

Cathepsin K is an osteoclast-derived cysteine protease that has been implicated as playing a major role in bone resorption. A substantial body of evidence indicates that cathepsin K is critical in osteoclast-mediated bone resorption and suggests that its pharmacological inhibition should result in inhibition of bone resorption in vivo. Here we report the pharmacological characterization of SB-462795 (relacatib) as a potent and orally bioavailable small molecule inhibitor of cathepsin K that inhibits bone resorption both in vitro in human tissue and in vivo in cynomolgus monkeys.

Intermittent treatment with parathyroid hormone (PTH) as well as a non-peptide small molecule agonist of the PTH1 receptor inhibits adipocyte differentiation in human bone marrow stromal cells.

Whereas continuous PTH infusion increases bone resorption and bone loss, intermittent PTH treatment stimulates bone formation, in part, via reactivation of quiescent bone surfaces and reducing osteoblast apoptosis. We investigated the possibility that intermittent and continuous PTH treatment also differentially regulates osteogenic and adipocytic lineage commitment of bone marrow stromal progenitor/mesenchymal stem cells (MSC). The MSC were cultured under mildly adipogenic conditions in medium supplemented with dexamethasone, insulin, isobutyl-methylxanthine and troglitazone (DIIT), and treated with 50 nM human PTH(1-34) for either 1 h/day or continuously (PTH replenished every 48 h).

Protection against congenital cytomegalovirus (CMV) disease, conferred by a replication-disabled, bacterial artificial chromosome (BAC)-based DNA vaccine.

It is unclear if protective immunity can be conferred by a cytomegalovirus (CMV) vaccine encoding a single protein subunit, or if multiple viral genes need to be targeted. Using the guinea pig model of congenital CMV infection, these studies examined the immunogenicity and efficacy of a DNA vaccine based on the guinea pig cytomegalovirus (GPCMV) genome cloned as a non-infectious BAC plasmid, modified by transposon insertion into the homolog of the HCMV tegument protein, UL48. Following vaccination of female Hartley guinea pigs with BAC DNA, adverse GPCMV-related pregnancy outcome were assessed after establishment of pregnancy, followed by GPCMV third-trimester challenge.

The effect of cidofovir on cytomegalovirus-induced hearing loss in a Guinea pig model.

Objective: To evaluate the utility of therapy with the cyclic cogener of the anti-cytomegalovirus (CMV) agent cidofovir against CMV-induced hearing loss in a guinea pig model.

Design: Thirty-six guinea pigs were randomly divided into 4 groups of 9. All groups underwent auditory brainstem response testing on days 0, 4, 7, 14, 21, and 28.

Increased osteoblastogenesis and decreased bone resorption protect against ovariectomy-induced bone loss in thrombospondin-2-null mice.

Although bone is composed primarily of extracellular matrix (ECM), the dynamic role that the ECM plays in regulating bone remodeling secondary to estrogen loss is relatively unexplored. Previous studies have shown that mice deficient in the matricellular protein thrombospondin-2 (TSP2-null) form excess endocortical bone; thus, we postulated that enhanced bone formation in TSP2-null mice could protect against ovariectomy (OVX)-induced bone loss. Wild-type (WT) OVX mice showed a significant loss of both midfemoral endocortical and proximal tibial trabecular bone, but OVX did not significantly alter TSP2-null bone.

Response to continuous and pulsatile PTH dosing: a mathematical model for parathyroid hormone receptor kinetics.

In this paper, we propose a mathematical model for parathyroid hormone receptor (PTH1R) kinetics, focusing on the receptor's response to PTH dosing to discern bone formation responses from bone resorption. The PTH1R is a major target for new osteoporosis treatments, as pulsatile PTH dosing has been shown to induce net bone formation in both animals and humans, and PTH(1-34) was recently FDA approved for the treatment of post-menopausal osteoporosis. PTH has also been shown to cause net bone loss when given continuously, so that the net action of PTH on bone is dependent on the dosing pattern.

The non-nucleoside antiviral, BAY 38-4766, protects against cytomegalovirus (CMV) disease and mortality in immunocompromised guinea pigs.

New antiviral drugs are needed for the treatment of cytomegalovirus (CMV) infections, particularly in immunocompromised patients. These studies evaluated the in vitro and in vivo activity of the non-nucleosidic CMV inhibitor, BAY 38-4766, against guinea pig cytomegalovirus (GPCMV). Plaque reduction assays indicated that BAY 38-4766 was active against GPCMV, with an IC(50) of 0.

Protection against congenital cytomegalovirus infection and disease in guinea pigs, conferred by a purified recombinant glycoprotein B vaccine.

Glycoprotein B (gB) has emerged as a subunit-vaccine candidate for congenital cytomegalovirus (CMV) infection, a major public health problem. The present study evaluated a cloned, recombinant gB vaccine in the guinea pig cytomegalovirus (GPCMV) model of congenital infection. Guinea pigs were immunized with gB, which was coadministered with either Freund's adjuvant or alum.

The effect of diaphragmatic stressors on recurrent hiatal hernia.

Hiatal disruption is one of the common mechanisms of failure after Nissen fundoplication. We investigated the correlation between various diaphragm stressors and disruption of the diaphragmatic closure. Thirty-seven patients with a hiatal hernia recurrence of 2 cm or greater, as proven by esophagram, endoscopy, or operative findings, were included.

Rapid inhibition of thyroxine-induced bone resorption in the rat by an orally active vitronectin receptor antagonist.

An excess of thyroid hormone results in increased bone turnover and loss of bone mass in humans. Exogenous administration of thyroid hormone to rats has served as a model of human hyperthyroidism in which antiresorptive therapies have been tested. We have further refined this model of thyroxine (T4)-induced turnover in the rat.

A potent small molecule, nonpeptide inhibitor of cathepsin K (SB 331750) prevents bone matrix resorption in the ovariectomized rat.

Inhibition of the cyteine proteinase, cathepsin K (E.C. 3.

Reduction in animal numbers by long-term implantation of intravenous and intra-arterial catheters in thyroparathyroidectomized rats.

The thyroparathyroidectomized (TPTx) rat has been extensively used to study parathyroid hormone (PTH)-mediated bone resorption by measuring systemic Ca2+ concentrations. Animals have been traditionally used acutely; that is, they are often infused immediately after surgery and are sacrificed after a single use. To perform multiple experiments using a single group of animals we developed a system of long-term implanted intravenous/arterial catheters.

Potent and selective inhibition of human cathepsin K leads to inhibition of bone resorption in vivo in a nonhuman primate.

Cathepsin K is a cysteine protease that plays an essential role in osteoclast-mediated degradation of the organic matrix of bone. Knockout of the enzyme in mice, as well as lack of functional enzyme in the human condition pycnodysostosis, results in osteopetrosis. These results suggests that inhibition of the human enzyme may provide protection from bone loss in states of elevated bone turnover, such as postmenopausal osteoporosis.

Changes in bone turnover following gonadotropin-releasing hormone (GnRH) agonist administration and estrogen treatment in cynomolgus monkeys: a short-term model for evaluation of antiresorptive therapy.

In this study we determine the early time course of estrogen deficiency-induced bone loss in the cynomolgus monkey and examine the potential of this method for evaluating antiresorptive therapies. In two groups of animals, estrogen deficiency was induced by the administration of a gonadotropin-releasing hormone agonist (GnRHa) and bone turnover was measured using biochemical markers. Two weeks after receiving GnRHa, serum estradiol decreased to below the detection limit in most animals and remained there through 6 months or until estrogen replacement started (months 4-6).

Disease-modifying activity of SB 273005, an orally active, nonpeptide alphavbeta3 (vitronectin receptor) antagonist, in rat adjuvant-induced arthritis.

Objective: To evaluate the effects of SB 273005, a potent, orally active nonpeptide antagonist of the integrin avbeta3 vitronectin receptor, on joint integrity in rats with adjuvant-induced arthritis (AIA).

Methods: Male Lewis rats with AIA were orally dosed either prophylactically (days 0-20) or therapeutically (days 10-20) with SB 273005. Efficacy was determined by measurement of paw inflammation, assessment of bone mineral density using dual-energy x-ray absorptiometry (DEXA), magnetic resonance imaging (MRI), and histologic evaluation.

Antagonism of the osteoclast vitronectin receptor with an orally active nonpeptide inhibitor prevents cancellous bone loss in the ovariectomized rat.

An orally active, nonpeptide Arg-Gly-Asp (RGD) mimetic alpha(v)beta3 antagonist, (S)-3-Oxo-8-[2-[6-(methylamino)-pyridin-2-yl]-1-ethoxy]-2-(2,2,2-trifluoroethyl)-2,3,4,5-tetrahydro-1H-2-benzazepine-4-acetic acid (compound 1), has been generated, which prevented net bone loss and inhibited cancellous bone turnover in vivo. The compound binds alpha(v)beta3 and the closely related integrin alpha(v)beta5 with low nanomolar affinity but binds only weakly to the related integrins alpha(IIb)beta3, and alpha5beta1. Compound 1 inhibited alpha(v)beta3-mediated cell adhesion with an IC50 = 3 nM.

Distinct mechanisms of action of selective estrogen receptor modulators in breast and osteoblastic cells.

Raloxifene and idoxifene are selective estrogen receptor modulators (SERMs) that exhibit tissue-specific agonist or antagonist properties via interactions with the estrogen receptor (ER). Both compounds are similarly osteoprotective in the ovariectomized rat in vivo as assessed by measurement of bone mineral density, urinary pyridinium cross-links, and serum osteocalcin, suggesting a similar mechanism of action. However, we have identified a fundamental difference in this mechanism via the estrogen response element (ERE) in osteoblast-like cells.

Antagonizing the parathyroid calcium receptor stimulates parathyroid hormone secretion and bone formation in osteopenic rats.

Parathyroid hormone (PTH) is an effective bone anabolic agent, but it must be administered parenterally. An orally active anabolic agent would provide a valuable alternative for treating osteoporosis. NPS 2143 is a novel, selective antagonist (a "calcilytic") of the parathyroid cell Ca(2+) receptor.