The discovery of MK-0674, an orally bioavailable cathepsin K inhibitor.

MK-0674 is a potent and selective cathepsin K inhibitor from the same structural class as odanacatib with a comparable inhibitory potency profile against Cat K. It is orally bioavailable and exhibits long half-life in pre-clinical species. In vivo studies using deuterated MK-0674 show stereoselective epimerization of the alcohol stereocenter via an oxidation/reduction cycle.

Identification of anabolic selective androgen receptor modulators with reduced activities in reproductive tissues and sebaceous glands.

Androgen replacement therapy is a promising strategy for the treatment of frailty; however, androgens pose risks for unwanted effects including virilization and hypertrophy of reproductive organs. Selective Androgen Receptor Modulators (SARMs) retain the anabolic properties of androgens in bone and muscle while having reduced effects in other tissues. We describe two structurally similar 4-aza-steroidal androgen receptor (AR) ligands, Cl-4AS-1, a full agonist, and TFM-4AS-1, which is a SARM.

Control of rat tail skin temperature regulation by estrogen receptor-beta selective ligand.

Objective: To test the role of ERbeta in the control of estrogen-dependent thermoregulation in rats.

Methods: Test the ability of an ERbeta-selective ligand to suppress the elevation in basal rat tail skin temperature (TST) caused by ovariectomy (OVX).

Results: ERbeta-19 is a tetrahydrofluorenone ERbeta-selective ligand that displaces 0.

Agonist-like SERM effects on ERalpha-mediated repression of MMP1 promoter activity predict in vivo effects on bone and uterus.

Estradiol receptors (ER), ERalpha and ERbeta, are ligand-dependent transcription factors that regulate gene expression. Human and murine genetics suggest that ERalpha is the key target for estradiol action on bone, uterus and breast. To date, the molecular mode of action of estradiol and selective estradiol receptor modulators (SERMs) on bone is not fully understood.

The discovery of odanacatib (MK-0822), a selective inhibitor of cathepsin K.

Odanacatib is a potent, selective, and neutral cathepsin K inhibitor which was developed to address the metabolic liabilities of the Cat K inhibitor L-873724. Substituting P1 and modifying the P2 side chain led to a metabolically robust inhibitor with a long half-life in preclinical species. Odanacatib was more selective in whole cell assays than the published Cat K inhibitors balicatib and relacatib.

Involvement of alpha(v)beta3 integrins in osteoclast function.

Integrins are heterodimeric adhesion receptors that mediate cell-matrix interaction. Osteoclast exhibits high expression of the alpha(v)beta(3) integrin, which binds to a variety of extracellular matrix proteins including vitronectin, osteopontin, and bone sialoprotein. Arg-Gly-Asp (RGD)-containing peptides, RGD-mimetics, and blocking antibodies to alpha(v)beta(3) integrin were shown to inhibit bone resorption in vitro and in vivo, suggesting that this integrin may play an important role in regulating osteoclast function.

M-CSF induces the stable interaction of cFms with alphaVbeta3 integrin in osteoclasts.

The macrophage colony stimulating factor receptor (cFms) and alpha(V)beta(3) integrin are both abundantly expressed and play critical roles in the differentiation, survival and migration of osteoclasts. We have previously demonstrated that cross-talk between cFms- and alpha(V)beta(3)-mediated signaling pathways regulated the cytoskeletal organization required for osteoclast migration. To investigate the nature of interaction between the two receptors, we sequentially used anion-exchange chromatography and immunoprecipitation to purify alpha(V)beta(3)-associated protein complexes.

Antagonist-induced, activation function-2-independent estrogen receptor alpha phosphorylation.

Estrogen receptor alpha (ERalpha) serine 118 (Ser118) phosphorylation modulates activation function-1 (AF1) function. Correct positioning of helix 12 promotes agonist-dependent recruitment of cyclin-dependent kinase-7 to catalyze this event. In this study we show robust cyclin-dependent kinase-7-independent, AF2 antagonist-induced Ser118 phosphorylation.

Characterization of articular cartilage and subchondral bone changes in the rat anterior cruciate ligament transection and meniscectomized models of osteoarthritis.

Osteoarthritis (OA) is a chronic joint disease characterized by cartilage destruction, subchondral bone sclerosis, and osteophyte formation. Subchondral bone stiffness has been proposed to initiate and/or contribute to cartilage deterioration in OA. The purpose of this study was to characterize subchondral bone remodeling, cartilage damage, and osteophytosis during the disease progression in two models of surgically induced OA.

Relative binding affinities of bisphosphonates for human bone and relationship to antiresorptive efficacy.

Potent bisphosphonates (BPs) preferentially bind bone at sites of active osteoclastic bone resorption, where they are taken up by the osteoclast and inhibit resorption. We tested the hypothesis that BP affinity to human bone affects antiresorptive potency. [(1)(4)C]-Alendronate binding to human bone was saturable and reversible with an apparent Kd of 72 microM by Scatchard analysis.

Mechanism of action of bisphosphonates.

In recent years, substantial progress has been made in understanding the mechanism for bisphosphonate suppression of bone turnover. Bisphosphonates can now be distinguished based on their molecular and cellular mechanisms of action. Simple bisphosphonates such as clodronate and etidronate inhibit bone resorption through induction of osteoclast apoptosis.

Estrogenic control of thermoregulation in ERalphaKO and ERbetaKO mice.

Objective: Estrogen is the most effective treatment for preventing the vasomotor symptoms in women. The ability of estrogen to control tail skin temperature (TST) in rats is used as an animal model for the studies of estrogens on menopausal hot flushes. Today, we know that estrogen can mediate its actions via the interaction with two different estrogen receptors: ERalpha and ERbeta.

Nonpeptide alpha(v)beta3 antagonists: identification of potent, chain-shortened 7-oxo RGD mimetics.

Potent, novel 7-oxo alpha(v)beta3 antagonists have been prepared. These antagonists offer decreased plasma protein binding and excellent pharmacokinetic profiles.

Cross-talk between an activator of nuclear receptors-mediated transcription and the D1 dopamine receptor signaling pathway.

Nuclear receptors are transcription factors that usually interact, in a ligand-dependent manner, with specific DNA sequences located within promoters of target genes. The nuclear receptors can also be controlled in a ligand-independent manner via the action of membrane receptors and cellular signaling pathways. 5-Tetradecyloxy-2-furancarboxylic acid (TOFA) was shown to stimulate transcription from the MMTV promoter via chimeric receptors that consist of the DNA binding domain of GR and the ligand binding regions of the PPARbeta or LXRbeta nuclear receptors (GR/PPARbeta and GR/LXRbeta).

Nitrogen-containing bisphosphonate mechanism of action.

The current paradigm for drug discovery requires the identification of a target involved in the disease process (e.g. enzyme or receptor) and the development of an appropriate ligand (activator, inhibitor or selective modulator).

Nonpeptide alphavbeta3 antagonists. Part 11: discovery and preclinical evaluation of potent alphavbeta3 antagonists for the prevention and treatment of osteoporosis.

3-(S)-Pyrimidin-5-yl-9-(5,6,7,8-tetrahydro-[1,8]naphthyridin-2-yl)-nonanoic acid (5e) and 3-(S)-(methylpyrimidin-5-yl)-9-(5,6,7,8-tetrahydro-[1,8]naphthyridin-2-yl)-nonanoic acid (5f) were identified as potent and selective antagonists of the alpha(v)beta(3) receptor. These compounds have excellent in vitro profiles (IC(50) = 0.07 and 0.

Nonpeptide alpha V beta 3 antagonists. Part 10: In vitro and in vivo evaluation of a potent 7-methyl substituted tetrahydro-[1,8]naphthyridine derivative.

Subtle modifications were incorporated into the structure of clinical candidate 1. These changes were designed to maintain potency and selectivity while inducing changes in physical properties leading to improved pharmacokinetics in three species. This approach led to the identification of 4 as a potent, selective alphaVbeta3 receptor antagonist that was selected for clinical development based on an improved PK profile and efficacy demonstrated in an in vivo model of bone turnover.

Nonpeptide alpha V beta 3 antagonists. Part 9: Improved pharmacokinetic profile through the use of an aliphatic, des-amide backbone.

A series of alphaVbeta3 receptor antagonists lacking the amide bond of previously-reported 'chain-shortened' compounds is described. Replacement of the lone amide bond with two methylene groups in this series yields more lipophilic compounds that have longer half-lives, lower clearance, and greater oral bioavailability when administered to dogs.

Rat tail skin temperature regulation by estrogen, phytoestrogens and tamoxifen.

Objective: Develop a rat model for the evaluation of estrogenic agents on estrogen deficiency-induced changes in thermoregulation.

Methods: OVX rats are impaired in thermoregulation which manifests itself as an elevation in basal tail skin temperature (TST) and are less able to respond to temperature changes than intact rats.

Results: Administration of estrogen subcutaneously to estrogen-depleted rats either as depot formulation, biodegradable pellets, or daily injections, suppressed the increased TST.

The LATS2/KPM tumor suppressor is a negative regulator of the androgen receptor.

The androgen receptor (AR) is a member of the steroid receptor superfamily that plays critical roles in the development and maintenance of the male reproductive system and in prostate cancer. Actions of AR are controlled by interaction with several classes of coregulators. In this study, we have identified LATS2/KPM as a novel AR-interacting protein.

Non-peptide alpha v beta 3 antagonists. Part 7: 3-Substituted tetrahydro-naphthyridine derivatives.

A series of 3-substituted tetrahydro-[1,8]naphthyridine containing alpha(v)beta(3) antagonists was prepared. A comparison of their in vitro IC(50) values to the electron properties of the 3-substituents revealed a good linear Hammett correlation (rho=-1.96, R(2)=0.

Regulatory mechanism of osteoclast activation.

Osteoclasts are multinucleated, terminally differentiated cells which play an essential role in bone resorption. Osteoclasts exhibit high expression of the alpha(v)beta3 integrin, which binds to a variety of extracellular matrix proteins, including vitronectin, osteopontin and bone sialoprotein. RGD (Aug-Gly-Asp)-containing peptides, RGD-mimetics and blocking antibodies to alpha(v)beta3 integrin were shown to inhibit bone resorption in vitro and in vivo, suggesting that this integrin plays an important role in regulating osteoclast function.

Non-peptide alpha(v)beta(3) antagonists: identification of potent, chain-shortened RGD mimetics that incorporate a central pyrrolidinone constraint.

Antagonists of the integrin receptor alpha(v)beta(3) are expected to have utility in the treatment of osteoporosis through inhibition of bone resorption. A series of potent, chain-shortened, pyrrolidinone-containing alpha(v)beta(3) receptor antagonists is described. Two sets of diasteromeric pairs of high-affinity antagonists demonstrated marked differences in log P values, which translated into differing dog pharmacokinetic properties.

Nonpeptide alphavbeta3 antagonists. 8. In vitro and in vivo evaluation of a potent alphavbeta3 antagonist for the prevention and treatment of osteoporosis.

3(S)-(6-methoxypyridin-3-yl)-3-[2-oxo-3-[3-(5,6,7,8-tetrahydro-[1,8]-naphthyridin-2-yl)propyl]imidazolidin-1-yl]propionic acid 6 was identified as a potent and selective antagonist of the alpha(v)beta(3) receptor. This compound has an excellent in vitro profile (IC(50) = 0.08 nM), a significant unbound fraction in human plasma (12%), and good pharmacokinetics in rat, dog, and rhesus monkey.