Clinical Pharmacokinetics of Ponesimod, a Selective S1P1 Receptor Modulator, in the Treatment of Multiple Sclerosis

Ponesimod, a selective, rapidly reversible, and orally active, sphingosine-1 phosphate receptor (S1P) modulator, is indicated for the treatment of relapsing-remitting multiple sclerosis (RRMS). The clinical pharmacokinetics (PK) and pharmacodynamics (PD) of ponesimod was studied in 16 phase I, one phase II, and one phase III clinical studies. Ponesimod population PK was characterized by an open two-compartment disposition model with a terminal half-life of 33 h (accumulation factor of 2- to 2.6-fold), and fast and almost complete oral absorption (absolute oral bioavailability: 84%), reaching peak plasma and blood concentrations within 2-4 h. Ponesimod is highly metabolized, and the parent compound along with its two major (non-clinically active) metabolites are mainly excreted in the feces (recovery: 57.3-79.6%) and to a lesser extent in the urine (recovery: 10.3-18.4%). Additionally, the population PKPD model characterized the ponesimod effects on heart rate: a transient, dose-dependent decrease in heart rate in the first days of dosing, that is mitigated by administering the first doses of ponesimod treatment using a gradual up-titration schedule, before reaching the daily maintenance dose of 20 mg. This selected maintenance dose has been shown to be superior in reducing annualized relapse rate (ARR) when compared with teriflunomide in a pivotal phase III study. Furthermore, a dose-dependent reduction of peripheral lymphocyte counts that is sustained with continued daily oral dosing of ponesimod and is rapidly (4-7 days) reversible upon drug discontinuation has been characterized with an indirect response model.

Bladder calculi causing irreducible urogenital prolapse

Over 200 000 surgeries for vaginal prolapse are done annually, and these are rarely urgent. However, when the rare event of bladder stones causes incarcerated procidentia, surgical intervention should not be delayed, due to unrelenting pain and end-organs effects. We present such a case below. A 71-year-old woman presents to our department with massive uterovaginal and rectal procidentia. This massive prolapse was found to be irreducible due to numerous dahllite stones in the bladder, and was causing obstructive uropathy with left-sided hydronephrosis. A multidisciplinary approach was necessary to surgically correct the prolapse and implement complete removal of all the stones. The simultaneous occurrence of uterovaginal prolapse, rectal prolapse and urolithiasis is uncommon. Stone formation is a result of chronically infected urine presenting a nidus for stone formation. This presentation has occurred very rarely over the last 70 years of the world's literature. Surgical cures can be achieved by either the vaginal or abdominal routes but should be treated emergently to alleviate pain, prevent renal impairment from obstructive uropathy and decrease infectious morbidity.

MK-7622: A First-in-Class M1 Positive Allosteric Modulator Development Candidate

Identification of ligands that selectively activate the M₁ muscarinic signaling pathway has been sought for decades to treat a range of neurological and cognitive disorders. Herein, we describe the optimization efforts focused on addressing key physicochemical and safety properties, ultimately leading to the clinical candidate MK-7622, a highly selective positive allosteric modulator of the M₁ muscarinic receptor that has entered Phase II studies in patients with Alzheimer's disease.

Discovery of naphthyl-fused 5-membered lactams as a new class of m1 positive allosteric modulators

Selective activation of the M1 muscarinic receptor via positive allosteric modulation represents an original approach to treat the cognitive decline in patients with Alzheimer's disease. A series of naphthyl-fused 5-membered lactams were identified as a new class of M1 positive allosteric modulators and were found to possess good potency and in vivo efficacy.

Identification of a methoxynaphthalene scaffold as a core replacement in quinolizidinone amide M(1) positive allosteric modulators

A series of methoxynaphthalene amides were prepared and evaluated as alternatives to quinolizidinone amide M1 positive allosteric modulators. A methoxy group was optimal for M1 activity and addressed key P-gp issues present in the aforementioned quinolizidinone amide series.

The preclinical efficacy, selectivity and pharmacologic profile of MK-5932, an insulin-sparing selective glucocorticoid receptor modulator

Glucocorticoids are used widely in the treatment of inflammatory diseases, but use is accompanied by a significant burden of adverse effects. It has been hypothesized that gene- and cell-specific regulation of the glucocorticoid receptor by small molecule ligands could be translated into a therapeutic with an improved risk-benefit profile. MK-5932 is a highly selective glucocorticoid receptor modulator that is anti-inflammatory in vivo with an improved profile on glucose metabolism: Bungard et al. (2011). Bioorg. Med. Chem. 19, 7374-7386. Here we describe the full biological profile of MK-5932. Cytokine production following lipopolysaccharide (LPS) challenge was blocked by MK-5932 in both rat and human whole blood. Oral administration reduced inflammatory cytokine levels in the serum of rats challenged with LPS. MK-5932 was anti-inflammatory in a rat contact dermatitis model, but was differentiated from 6-methylprednisolone by a lack of elevation of fasting insulin or glucose levels after 7 days of dosing, even at high exposure levels. In fact, animals in the vehicle group were consistently hyperglycemic at the end of the study, and MK-5932 normalized glucose levels in a dose-dependent manner. MK-5932 was also anti-inflammatory in the rat collagen-induced arthritis and adjuvant-induced arthritis models. In healthy dogs, oral administration of MK-5932 exerted acute pharmacodynamic effects with potency comparable to prednisone, but with important differences on neutrophil counts, again suggestive of a dissociated profile. Important gaps in our understanding of mechanism of action remain, but MK-5932 will be a useful tool in dissecting the mechanisms of glucose dysregulation by therapeutic glucocortiocids.

Orally active fumagillin analogues: transformations of a reactive warhead in the gastric environment

Semisynthetic analogues of fumagillin, 1, inhibit methionine aminopeptidase-2 (MetAP2) and have entered the clinic for the treatment of cancer. An optimized fumagillin analogue, 3 (PPI-2458), was found to be orally active, despite containing a spiroepoxide function that formed a covalent linkage to the target protein. In aqueous acid, 3 underwent ring-opening addition of water and HCl, leading to four products, 4-7, which were characterized in detail. The chlorohydrin, but not the diol, products inhibited MetAP2 under weakly basic conditions, suggesting reversion to epoxide as a step in the mechanism. In agreement, chlorohydrin 6 was shown to revert rapidly to 3 in rat plasma. In an ex vivo assay, rats treated with purified acid degradants demonstrated inhibition of MetAP2 that correlated with the biochemical activity of the compounds. Taken together, the results indicate that degradation of the parent compound was compensated by the formation of active equivalents leading to a pharmacologically useful level of MetAP2 inhibition.

Identification of amides as carboxylic Acid surrogates for quinolizidinone-based m1 positive allosteric modulators

Selective activation of the M1 muscarinic receptor via positive allosteric modulation represents an approach to treat the cognitive decline in patients with Alzheimer's disease. A series of amides were examined as a replacement for the carboxylic acid moiety in a class of quinolizidinone carboxylic acid M1 muscarinic receptor positive allosteric modulators, and leading pyran 4o and cyclohexane 5c were found to possess good potency and in vivo efficacy.

UGT2B17 genetic polymorphisms dramatically affect the pharmacokinetics of MK-7246 in healthy subjects in a first-in-human study

MK-7246, an antagonist of the chemoattractant receptor on T helper type 2 (Th2) cells, is being developed for the treatment of respiratory diseases. In a first-in-human study, we investigated whether genetic polymorphisms contributed to the marked intersubject variability in the pharmacokinetics of MK-7246 and its glucuronide metabolite M3. Results from in vitro enzyme kinetic studies suggested that UGT2B17 is probably the major enzyme responsible for MK-7246 metabolism in both the liver and the intestine. As compared with those with the UGT2B17*1/*1 wild-type genotype, UGT2B17*2/*2 carriers, who possess no UGT2B17 protein, had 25- and 82-fold greater mean dose-normalized values of area under the plasma concentration–time curve (AUC) and peak concentration of MK-7246, respectively, and a 24-fold lower M3-to-MK-7246 AUC ratio. The apparent half-life of MK-7246 was not as variable between these two genotypes. Therefore, the highly variable pharmacokinetics of MK-7246 is attributable primarily to the impact of UGT2B17 genetic polymorphisms and extensive first-pass metabolism of MK-7246.

Discovery of a selective allosteric M1 receptor modulator with suitable development properties based on a quinolizidinone carboxylic acid scaffold

One approach to ameliorate the cognitive decline in Alzheimer's disease (AD) has been to restore neuronal signaling from the basal forebrain cholinergic system via the activation of the M(1) muscarinic receptor. A number of nonselective M(1) muscarinic agonists have previously shown positive effects on cognitive behaviors in AD patients, but were limited due to cholinergic adverse events thought to be mediated by the activation of the M(2) to M(5) subtypes. One strategy to confer selectivity for M(1) is the identification of positive allosteric modulators, which would target an allosteric site on the M(1) receptor rather than the highly conserved orthosteric acetylcholine binding site. Quinoline carboxylic acids have been previously identified as highly selective M(1) positive allosteric modulators with good pharmacokinetic and in vivo properties. Herein is described the optimization of a novel quinolizidinone carboxylic acid scaffold with 4-cyanopiperidines being a key discovery in terms of enhanced activity. In particular, modulator 4i gave high plasma free fractions, enhanced central nervous system (CNS) exposure, was efficacious in a rodent in vivo model of cognition, and afforded good physicochemical properties suitable for further preclinical evaluation.

Quinolizidinone carboxylic acids as CNS penetrant, selective m1 allosteric muscarinic receptor modulators

Positive allosteric modulation of the M1 muscarinic receptor represents an approach to treat the cognitive decline in patients with Alzheimer's disease. Replacement of a quinolone ring system in a quinolone carboxylic acid series of M1 modulators with a quinolizidinone bearing a basic amine linkage led to a series of compounds with higher free fraction, enhanced CNS exposure, and improved efficacy in rodent in vivo models of cognition.

N-heterocyclic derived M1 positive allosteric modulators

Replacement of a phenyl ring with N-linked heterocycles in a series of quinolone carboxylic acid M1 positive allosteric modulators was investigated. In particular, a pyrazole derivative exhibited improvements in potency, free fraction, and CNS exposure.

Carbamate analogues of fumagillin as potent, targeted inhibitors of methionine aminopeptidase-2

Inhibition of methionine aminopeptidase-2 (MetAP2) represents a novel approach to antiangiogenic therapy. We describe the synthesis and activity of fumagillin analogues that address the pharmacokinetic and safety liabilities of earlier candidates in this compound class. Two-step elaboration of fumagillol with amines yielded a diverse series of carbamates at C6 of the cyclohexane spiroepoxide. The most potent of these compounds exhibited subnanomolar inhibition of cell proliferation in HUVEC and BAEC assays. Although a range of functionalities were tolerated at this position, alpha-trisubstituted amines possessed markedly decreased inhibitory activity, and this could be rationalized by modeling based on the known fumagillin-MetAP2 crystal structure. The lead compound resulting from these studies, (3R,4S,5S,6R)-5-methoxy-4-((2R,3R)-2-methyl-3-(3-methylbut-2-enyl)oxiran-2-yl)-1-oxaspiro[2.5]octan-6-yl (R)-1-amino-3-methyl-1-oxobutan-2-ylcarbamate, (PPI-2458), demonstrated an improved pharmacokinetic profile relative to the earlier clinical candidate TNP-470, and has advanced into phase I clinical studies in non-Hodgkin's lymphoma and solid cancers.

Alterations in attentional mechanisms in response to acute inflammatory pain and morphine administration

Research indicates that pain negatively impacts attention; however, the extent of this impact and the mechanisms of the effect of pain on normal attentional processing remain unclear. This study 1) examined the impact of acute inflammatory pain on attentional processing, 2) examined the impact of morphine on attentional processing, and 3) determined if an analgesic dose of morphine would return attentional processing to normal levels. Male Sprague-Dawley rats were trained on the 5 choice serial reaction time task (5CSRTT), a test commonly used to assess the attentional mechanisms of rodents. Animals were injected with saline or 1, 3, or 6 mg/kg of morphine. Twenty minutes later, animals received a formalin (or saline) injection into one hind paw to induce an inflammatory condition and were then immediately tested in the 5CSRTT. The results show that the formalin injection significantly impaired performance, as measured by an increase in the number of trials in which the animal failed to attend to the task. Likewise, a high dose of morphine (6 mg/kg) produced similar decrements in task performance. Of primary importance is that 3 mg/kg of morphine produced analgesia with only mild sedation, and performance in the 5CSRTT was improved with this dose. This is the first study to use an animal model of acute pain to demonstrate the negative impact of pain on attention, and provides a novel approach to examine the neural correlates that underlie the disruptive impact of pain on attention.

Infrared spectra of the Li+–(H2)n (n=1–3) cation complexes

The Li+-(H2)n n=1-3 complexes are investigated through infrared spectra recorded in the H-H stretch region (3980-4120 cm-1) and through ab initio calculations at the MP2/aug-cc-pVQZ level. The rotationally resolved H-H stretch band of Li+-H2 is centered at 4053.4 cm-1 [a -108 cm-1 shift from the Q1(0) transition of H2]. The spectrum exhibits rotational substructure consistent with the complex possessing a T-shaped equilibrium geometry, with the Li+ ion attached to a slightly perturbed H2 molecule. Around 100 rovibrational transitions belonging to parallel Ka=0-0, 1-1, 2-2, and 3-3 subbands are observed. The Ka=0-0 and 1-1 transitions are fitted by a Watson A-reduced Hamiltonian yielding effective molecular parameters. The vibrationally averaged intermolecular separation in the ground vibrational state is estimated as 2.056 A increasing by 0.004 A when the H2 subunit is vibrationally excited. The spectroscopic data are compared to results from rovibrational calculations using recent three dimensional Li+-H2 potential energy surfaces [Martinazzo et al., J. Chem. Phys. 119, 11241 (2003); Kraemer and Spirko, Chem. Phys. 330, 190 (2006)]. The H-H stretch band of Li+-(H2)2, which is centered at 4055.5 cm-1 also exhibits resolved rovibrational structure. The spectroscopic data along with ab initio calculations support a H2-Li+-H2 geometry, in which the two H2 molecules are disposed on opposite sides of the central Li+ ion. The two equivalent Li+...H2 bonds have approximately the same length as the intermolecular bond in Li+-H2. The Li+-(H2)3 cluster is predicted to possess a trigonal structure in which a central Li+ ion is surrounded by three equivalent H2 molecules. Its infrared spectrum features a broad unresolved band centered at 4060 cm-1.

A novel methionine aminopeptidase-2 inhibitor, PPI-2458, inhibits non-Hodgkin's lymphoma cell proliferation in vitro and in vivo

PURPOSE

Fumagillin and related compounds have potent antiproliferative activity through inhibition of methionine aminopeptidase-2 (MetAP-2). It has recently been reported that MetAP-2 is highly expressed in germinal center B cells and germinal center-derived non-Hodgkin's lymphomas (NHL), suggesting an important role for MetAP-2 in proliferating B cells. Therefore, we determined the importance of MetAP-2 in normal and transformed germinal center B cells by evaluating the effects of MetAP-2 inhibition on the form and function of germinal centers and germinal center-derived NHL cells.

EXPERIMENTAL DESIGN

To examine the activity of PPI-2458 on germinal center morphology, spleen sections from cynomolgus monkeys treated with oral PPI-2458 were analyzed. Antiproliferative activity of PPI-2458 was assessed on germinal center-derived NHL lines in culture. A MetAP-2 pharmacodynamic assay was used to determine cellular MetAP-2 inhibition following PPI-2458 treatment. Finally, inhibition of MetAP-2 and proliferation by PPI-2458 was examined in the human SR NHL line in culture and in implanted xenografts.

RESULTS

Oral PPI-2458 caused a reduction in germinal center size and number in lymphoid tissues from treated animals. PPI-2458 potently inhibited growth (GI(50) = 0.2-1.9 nmol/L) of several NHL lines in a manner that correlated with MetAP-2 inhibition. Moreover, orally administered PPI-2458 significantly inhibited SR tumor growth, which correlated with inhibition of tumor MetAP-2 (>85% at 100 mg/kg) in mice.

CONCLUSIONS

These results show the potent antiproliferative activity of PPI-2458 on NHL lines in vitro and oral antitumor activity in vivo and suggest the therapeutic potential of PPI-2458 as a novel agent for treatment of NHL should be evaluated in the clinical setting.

Rotationally resolved infrared spectrum of the Li+–D2 cation complex

The infrared spectrum of mass selected Li(+)-D(2) cations is recorded in the D-D stretch region (2860-2950 cm(-1)) in a tandem mass spectrometer by monitoring Li(+) photofragments. The D-D stretch vibration of Li(+)-D(2) is shifted by -79 cm(-1) from that of the free D(2) molecule indicating that the vibrational excitation of the D(2) subunit strengthens the effective Li(+)cdots, three dots, centeredD(2) intermolecular interaction. Around 100 rovibrational transitions, belonging to parallel K(a)=0-0, 1-1, and 2-2 subbands, are fitted to a Watson A-reduced Hamiltonian to yield effective molecular parameters. The infrared spectrum shows that the complex consists of a Li(+) ion attached to a slightly perturbed D(2) molecule with a T-shaped equilibrium configuration and a 2.035 A vibrationally averaged intermolecular separation. Comparisons are made between the spectroscopic data and data obtained from rovibrational calculations using a recent three dimensional Li(+)-D(2) potential energy surface [R. Martinazzo, G. Tantardini, E. Bodo, and F. Gianturco, J. Chem. Phys. 119, 11241 (2003)].

Inhibition of melanoma tumor growth by a pharmacological inhibitor of MetAP-2, PPI-2458

Over the past few decades, melanoma has shown the fastest growing incidence rate of all cancers. This malignancy is clinically defined by its potential to rapidly metastasize, and advanced metastatic melanomas are highly resistant to existing therapeutic regimens. Here, we report that PPI-2458, a novel, orally active agent of the fumagillin class of irreversible methionine aminopeptidase-2 (MetAP-2) inhibitors, potently inhibited the proliferation of B16F10 melanoma cells in vitro, with a growth inhibitory concentration 50% (GI50) of 0.2 nM. B16F10 growth inhibition was correlated with the inhibition of MetAP-2 enzyme, in a dose-dependent fashion, as determined by a pharmacodynamic assay, which measures the amount of uninhibited MetAP-2 following PPI-2458 treatment. Prolonged exposure of B16F10 cells to PPI-2458 at concentrations of up to 1 microM, 5,000-fold above the GI50, did not alter their sensitivity to PPI-2458 growth inhibition and no drug resistance was observed. Moreover, prolonged exposure to this agent induced melanogenesis, concomitant with the elevated expression of the melanocyte-specific enzymes tyrosinase and tyrosinase-related proteins (TRP) 1 and 2, a morphological feature associated with differentiated melanocytes. PPI-2458, when administered orally (p.o.), significantly inhibited B16F10 tumor growth in mice in a dose-dependent fashion, with a maximum inhibition of 62% at 100 mg/kg. This growth inhibition was directly correlated to the amount of irreversibly inhibited MetAP-2 (80% at 100 mg/kg PPI-2458) in tumor tissue. These data demonstrate that PPI-2458 has potent antiproliferative activity against B16F10 cells in vitro and in vivo, and that both activities are directly correlated with levels of MetAP-2 enzyme inhibition. This antiproliferative activity, coupled with additional observations from studies in vitro (absence of detectable resistance to PPI-2458 and induction of morphological features consistent with differentiated melanocytes), provides a rationale for assessing the therapeutic potential of PPI-2458 in the treatment of melanoma.

Inhibition of melanoma tumor growth by a pharmacological inhibitor of MetAP-2, PPI-2458

Over the past few decades, melanoma has shown the fastest growing incidence rate of all cancers. This malignancy is clinically defined by its potential to rapidly metastasize, and advanced metastatic melanomas are highly resistant to existing therapeutic regimens. Here, we report that PPI-2458, a novel, orally active agent of the fumagillin class of irreversible methionine aminopeptidase-2 (MetAP-2) inhibitors, potently inhibited the proliferation of B16F10 melanoma cells in vitro, with a growth inhibitory concentration 50% (GI50) of 0.2 nM. B16F10 growth inhibition was correlated with the inhibition of MetAP-2 enzyme, in a dose-dependent fashion, as determined by a pharmacodynamic assay, which measures the amount of uninhibited MetAP-2 following PPI-2458 treatment. Prolonged exposure of B16F10 cells to PPI-2458 at concentrations of up to 1 microM, 5,000-fold above the GI50, did not alter their sensitivity to PPI-2458 growth inhibition and no drug resistance was observed. Moreover, prolonged exposure to this agent induced melanogenesis, concomitant with the elevated expression of the melanocyte-specific enzymes tyrosinase and tyrosinase-related proteins (TRP) 1 and 2, a morphological feature associated with differentiated melanocytes. PPI-2458, when administered orally (p.o.), significantly inhibited B16F10 tumor growth in mice in a dose-dependent fashion, with a maximum inhibition of 62% at 100 mg/kg. This growth inhibition was directly correlated to the amount of irreversibly inhibited MetAP-2 (80% at 100 mg/kg PPI-2458) in tumor tissue. These data demonstrate that PPI-2458 has potent antiproliferative activity against B16F10 cells in vitro and in vivo, and that both activities are directly correlated with levels of MetAP-2 enzyme inhibition. This antiproliferative activity, coupled with additional observations from studies in vitro (absence of detectable resistance to PPI-2458 and induction of morphological features consistent with differentiated melanocytes), provides a rationale for assessing the therapeutic potential of PPI-2458 in the treatment of melanoma.

Infrared spectra of the Cl––C2H4 and Br––C2H4 anion dimers

Infrared spectra of mass-selected Cl- -C2H4 and Br- -C2H4 complexes are recorded in the vicinity of the ethylene CH stretching vibrations (2700-3300 cm(-1) using vibrational predissociation spectroscopy. Spectra of both complexes exhibit 6 prominent peaks in the CH stretch region. Comparison with calculated frequencies reveal that the 4 higher frequency bands are associated with CH stretching modes of the C2H4 subunit, while the 2 weaker bands are assigned as overtone or combinations bands gaining intensity through interaction with the CH stretches. Ab initio calculations at the MP2/aug-cc-pVDZ level suggest that C2H4 preferentially forms a single linear H-bond with Cl- and Br- although a planar bifurcated configuration lies only slightly higher in energy (by 110 and 16 cm(-1), respectively). One-dimensional potential energy curves describing the in-plane intermolecular bending motion are developed which are used to determine the corresponding vibrational energies and wavefunctions. Experimental and theoretical results suggest that in their ground vibrational state the Cl- -C2H4 and Br- -C2H4 complexes are localized in the single H-bonded configuration, but that with the addition of modest amounts of internal energy, the in-plane bending wavefunction also has significant amplitude in the bifurcated structure.

Methionine aminopeptidases type I and type II are essential to control cell proliferation

The dependence of cell growth on methionine aminopeptidase (MetAP) function in bacteria and yeast is firmly established. Here we report experimental evidence that the control of cell proliferation in mammalian cells is directly linked and strictly dependent on the activity of both MetAP-1 and MetAP-2. The targeted downregulation of either methionine aminopeptidase MetAP-1 or MetAP-2 protein expression by small interfering RNA (siRNA) significantly inhibited the proliferation of human umbilical vein endothelial cells (HUVEC) (70%-80%), while A549 human lung carcinoma cell proliferation was less inhibited (20%-30%). The cellular levels of MetAP-2 enzyme were measured after MetAP-2 siRNA treatment and found to decrease over time from 4 to 96 h, while rapid and complete depletion of MetAP-2 enzyme activity was observed after 4 h treatment with two pharmacological inhibitors of MetAP-2, PPI-2458 and fumagillin. When HUVEC and A549 cells were treated simultaneously with MetAP-2 siRNA and PPI-2458, or fumagillin, which irreversibly inhibit MetAP-2 enzyme activity, no additive effect on maximum growth inhibition was observed. This strongly suggests that MetAP-2 is the single critical cellular enzyme affected by either MetAP-2 targeting approach. Most strikingly, despite their significantly different sensitivity to growth inhibition after targeting of either MetAP-1 or MetAP-2, HUVEC, and A549 cells, which were made functionally deficient in both MetAP-1 and MetAP-2 were completely or almost completely inhibited in their growth, respectively. This closely resembled the observed growth inhibition in genetically double-deficient map1map2 yeast strains. These results suggest that MetAP-1 and MetAP-2 have essential functions in the control of mammalian cell proliferation and that MetAP-dependent growth control is evolutionarily highly conserved.

A methionine aminopeptidase-2 inhibitor, PPI-2458, for the treatment of rheumatoid arthritis

The hallmark of rheumatoid arthritis (RA) is the progressive destruction of articular joints, characterized by invasive synovial hyperplasia and pathological neovascularization. Here we report that PPI-2458, a member of the fumagillin class of irreversible methionine aminopeptidase-2 (MetAP-2) inhibitors, potently inhibits the proliferation of human fibroblast-like synoviocytes (HFLS-RA), derived from RA patients, with a growth inhibitory concentration 50 (GI(50)) of 0.04 nM and a maximum inhibition of >95% at 1 nM. Human umbilical vein endothelial cells (HUVEC) are similarly inhibited in proliferation by PPI-2458 (GI(50), 0.2 nM). We developed a method to measure the level of MetAP-2 enzyme inhibition after exposure to PPI-2458 and demonstrate that growth inhibition of PPI-2458-sensitive HFLS-RA and HUVEC is linked to MetAP-2 enzyme inhibition, in a dose-dependent fashion. The secretion of several inflammatory mediators such as IL-6 and vascular endothelial growth factor from activated HFLS-RA was not inhibited by PPI-2458. The CNS toxicity profile of PPI-2458, determined by the incidence of seizures, is significantly improved over that of the parental compound TNP-470. In the rat model of peptidoglycan-polysaccharide-induced arthritis, PPI-2458 significantly attenuated paw swelling when therapeutically administered after the onset of chronic disease. We suggest that the mechanism of PPI-2458 action, highly selective and potent anti-proliferative activity on HFLS-RA and HUVEC in vitro, a significantly improved CNS toxicity profile, and marked attenuation of chronic disease in the rat peptidoglycan-polysaccharide arthritis model in vivo, positions this compound as a drug for the treatment of RA.

Mechanisms of idiosyncratic drug reactions: the case of felbamate

Idiosyncratic drug reactions (IDR) are a specific type of drug toxicity characterized by their delayed onset, low incidence and reactive metabolite formation with little, if any, correlation between pharmacokinetics or pharmacodynamics and the toxicological outcome. As the name implies, IDR are unpredictable and often result in the post marketing failure of otherwise useful therapies. Examples of drugs, which have failed as a result of IDR in recent years, include trovafloxacin, zileuton, troglitazone, tolcapone and felbamate. To date there exists no pre-clinical model to predict these adverse drug reactions and a mechanistic understanding of these toxicities remains limited. In an attempt to better understand this class of drug toxicities and gain mechanistic insight, we have studied the IDR associated with a model compound, felbamate. Our studies with felbamate are consistent with the theory that compounds which cause IDR undergo bioactivation to a highly reactive electrophilic metabolite that is capable of forming covalent protein adducts in vivo. In additon, our data suggest that under normal physiological conditions glutathione plays a protective role in preventing IDR during felbamate therapy, further emphasizing a correlation between reactive metabolite formation and a toxic outcome. Clinical studies with felbamate have been able to demonstrate an association between reactive metabolite formation and a clinically relevant toxicity; however, additional research is required to more fully understand the link between reactive metabolite formation and the events which elicit toxicity. Going forward, it seems reasonable that screening for reactive metabolite formation in early drug discovery may be an important tool in eliminating the post-marketing failure of otherwise useful therapies.

Medical internet ethics: a field in evolution

As in any new field, the merger of medicine, e-commerce and the Internet raises many questions pertaining to ethical conduct. Key issues include defining the essence of the patient-provider relationship, establishing guidelines and training for practicing online medicine and therapy, setting standards for ethical online research, determining guidelines for providing quality healthcare information and requiring ethical conduct for medical and health websites. Physicians who follow their professional code of ethics are obligated not to exploit the relationship they have with patients, nor allow anyone else working with them to do so. Physicians and therapists are obligated to serve those who place trust in them for treatment, whether in face-to-face or online Internet encounters with patients or clients. This ethical responsibility to patients and clients is often in direct conflict with the business model of generating profits. Healthcare professionals involved in Medical Internet Ethics need to define the scope of competent medical and healthcare on the Internet. The emerging ethical issues facing medicine on the Internet, the current state of medical ethics on the Internet and questions for future directions of study in this evolving field are reviewed in this paper.

Constitutive activation of STAT3 is associated with the acquisition of an interleukin 6-independent phenotype by murine plasmacytomas and hybridomas

Interleukin 6 (IL-6), the major growth factor for myeloma cells, signals through the activation of signal transducers and activators of transcription (STAT) proteins. An important step in the malignant progression of murine plasmacytomas is the transition from dependence on IL-6 to a state of IL-6 independence. To elucidate the mechanism whereby IL-6 independence occurs, intracellular signaling events elicited by IL-6 in both IL-6-dependent and -independent plasmacytomas and hybridomas were compared. It was found that STAT3, a key molecule involved in IL-6 signaling, was constitutively activated and phosphorylated in IL-6-independent cell lines compared to the IL-6-dependent cells. Further comparison of upstream signaling pathways revealed that JAK-1 was constitutively present in anti-phosphotyrosine immunoprecipitates of IL-6-independent cells; gp130 was constitutively phosphorylated in a subset of IL-6-independent plasmacytomas, whereas other IL-6-independent lines showed no detectable gp130 phosphorylation in the absence of exogenous IL-6. Secretion of a factor capable of supporting the growth of IL-6-dependent cells was observed in one of the IL-6-independent plasmacytomas, but not in others, making an autocrine mechanism an unlikely explanation for IL-6 independence. These findings provide evidence that the constitutive activation of STAT3, either in the absence of detectable receptor-proximal events or associated with the concomitant activation of gp130, can contribute to the process of IL-6 independence.

The synthesis, in vitro reactivity, and evidence for formation in humans of 5-phenyl-1,3-oxazinane-2,4-dione, a metabolite of felbamate

Previously we have proposed and provided evidence for a metabolic scheme leading to 3-carbamoyl-2-phenylpropionaldehyde from the antiepileptic drug felbamate. This aldehyde was found to undergo reversible cyclization to form the more stable cyclic carbamate 4-hydroxy-5-phenyl-tetrahydro-1,3-oxazin-2-one or undergo elimination to form 2-phenylpropenal. The cyclic carbamate bears structural similarity to 4-hydroxycyclophosphamide and there is an intriguing parallelism between the pathway from the cyclic carbamate to 2-phenylpropenal and the known pathway from 4-hydroxycyclophosphamide to acrolein. The similarity of these transformations led us to consider 5-phenyl-1,3-oxazinane-2,4-dione, which could arise from an oxidation of the cyclic carbamate, as a potential metabolite of felbamate. As the formation of this dione species may have both potential pharmacologic and toxicologic implications for felbamate therapy, we wished to study its reactivity. We have developed a synthesis of 5-phenyl-1, 3-oxazinane-2,4-dione and evaluated its reactivity in vitro. This dione was found to undergo base-catalyzed decomposition to three products, one of which is the major human metabolite of felbamate, 3-carbamoyl-2-phenylpropionic acid. Furthermore, we have found evidence for the presence of the dione in human urine after felbamate treatment through the identification of its major in vitro decomposition product, 2-phenylacrylamide 11.

Evaluation of methods for transient transfection of a murine macrophage cell line, RAW 264.7

Monocyte/macrophage cell lines are fastidious cells commonly used in transient transfection experiments. In the course of a study of gene regulation by lipopolysaccharide (LPS), we have compared several methods for DNA-mediated cell transfection to determine which would be optimally applicable to the macrophage line, RAW 264.7. Both the response level (LPS inducibility) and the degree of inter-assay variation were evaluated for each transfection technique. The following methods were compared: Lipofectin, LipofectAMINE, LipofectAMINE PLUS, SuperFect, Ca3(PO4)2 DNA co-precipitation, DEAE dextran-mediated transfection and electroporation. The transfected plasmid DNA included a luciferase reporter construct containing the junB minimal promoter under the control of an LPS-inducible 1300-bp regulatory fragment downstream of junB 5'-flanking sequence, as well as a beta-galactosidase reporter construct under the adenovirus promoter and enhancer used as an internal control. Electroporation, followed by a resting period of 16-24 h before stimulation with LPS, had the highest inducibility of all methods. DEAE dextran and Ca3(PO4)2 precipitation showed the least and the greatest inter-assay variation, respectively. For all other methods, inter-assay variability fell within this range. The results presented may serve as both a general reference and a guide for reporter gene studies in this or other macrophage cell lines.

Quantification in patient urine samples of felbamate and three metabolites: acid carbamate and two mercapturic acids

PURPOSE

Previously we proposed and provided evidence for the metabolic pathway of felbamate (FBM), which leads to the reactive metabolite, 3-carbamoyl-2-phenylpropion-aldehyde. This aldehyde carbamate was suggested to be the reactive intermediate in the oxidation of 2-phenyl-1,3-propanediol monocarbamate to the major human metabolite 3-carbamoyl-2-phenylpropionic acid. In addition, the aldehyde carbamate was found to undergo spontaneous elimination to 2-phenylpropenal, commonly known as atropaldehyde. Moreover, atropaldehyde was proposed to play a role in the development of toxicity during FBM therapy. Evidence for atropaldehyde formation in vivo was reported with the identification of modified N-acetyl-cysteine conjugates of atropaldehyde in both human and rat urine after FBM administration. Identification of the atropaldehyde-derived mercapturic acids in urine after FBM administration is consistent with the hypothesis that atropaldehyde is formed in vivo and that it reacts with thiol nucleophiles. Based on the hypothesis that the potential for toxicity will correlate to the amount of atropaldehyde formed, we sought to develop an analytic method that would quantify the amount of relevant metabolites excreted in patient urine.

METHODS

We summarize the results of an LC/MS method used to quantify FBM, 3-carbamoyl-2-phenylpropionic acid and two atropaldehyde-derived mercapturic acids in the patient population.

RESULTS

Analysis was performed on 31 patients undergoing FBM therapy. The absolute quantities of FBM and three metabolites were measured.

CONCLUSIONS

This method demonstrated sufficient precision for the identification of patients exhibiting "abnormal" levels of atropaldehyde conjugates and may hold potential for patient monitoring.

The synthesis and evaluation of temperature sensitive tubulin toxins

The synthesis of several potent inhibitors of tubulin polymerization that exert their activities through interaction at the colchicine binding site is described. These agents were evaluated for their abilities to inhibit the polymerization of tubulin and the growth of neoplastic cell cultures. Additionally, the inhibition of tubulin polymerization activity of these agents was assessed over a temperature range of 30-45 degrees C to ascertain the effect of temperature on this activity. Several of the compounds possess significant inhibition of tubulin polymerization activity, and select compounds exhibit this activity in a temperature dependent manner.

Potentially reactive cyclic carbamate metabolite of the antiepileptic drug felbamate produced by human liver tissue in vitro

Felbamate (FBM) is a novel antiepileptic drug that was approved in 1993 for treatment of several forms of epilepsy. After its introduction, toxic reactions (aplastic anemia and hepatotoxicity) associated with its use were reported. It is unknown whether FBM or one of its metabolites is responsible for these idiosyncratic adverse reactions. Although the metabolism of FBM has not been fully characterized, three primary metabolites of FBM have been identified, i.e. 2-hydroxy, p-hydroxy, and monocarbamate metabolites. In addition, the monocarbamate metabolite leads to a carboxylic acid, which is the major metabolite of FBM in humans. Formation of the hydroxylated products of FBM involves cytochrome P450 enzymes, but the enzymes involved in the formation and further metabolism of the monocarbamate have not yet been elucidated. Recently, mercapturate metabolites of FBM have been identified in human urine, and a metabolic scheme involving reactive aldehyde metabolite formation from the monocarbamate metabolite has been proposed. The present study confirmed the formation of the proposed metabolites using human liver tissue in vitro. The aldehyde intermediates were trapped as oxime derivatives, and the cyclic equilibrium product (proposed as a storage and transport form for the aldehydes) was monitored directly by HPLC or GC/MS. Formation of putative toxic aldehyde intermediates and the major carboxylic acid metabolite of FBM was differentially effected with the cofactors NADP+ and NAD+. It is possible that the cofactors may influence the relative metabolism via activation and inactivation pathways.

The synthesis and evaluation of benzannelated-azatoxins: the benzazatoxins

The synthesis and evaluation of azatoxin congeners possessing annealed aromatic frameworks are described. The compounds were evaluated for their abilities to affect topoisomerase II inhibition through the stabilization of "cleavable complex" and for the inhibition of tubulin polymerization using purified bovine brain tubulin.

Synthesis and structure-activity profiles of A-homoestranes, the estratropones

2-Methoxyestradiol, a mammalian metabolite of estradiol, has reported antiangiogenic activity which has been proposed to be mediated through interaction at the colchicine binding site on the tubulin monomer. Subsequent structure-activity studies of 2-methoxyestradiol have yielded highly potent steroidal inhibitors of tubulin polymerization. In an effort to probe the scope of binding at the colchicine binding site and the nature of the relationship between 2-methoxyestradiol and colchicine, a series of colchicine/2-methoxyestradiol hybrids was synthesized. These A-homoestrane hybrid systems, collectively termed estratropones, possessed an A-ring tropone system with the keto functionality at either the C-2, C-3, or C-4 position of the steroid nucleus. The estratropones were evaluated for their ability to inhibit the polymerization of tubulin using an in vitro purified bovine brain assay. Most of these hybrids inhibit polymerization with greater potency than either of the natural products. The most potent of these congeners possessed an approximate 5-fold enhancement of the activity of colchicine for the inhibition of tubulin polymerization. alpha-Substituents on the tropone ring showed varied effects on the activities for the two classes of estratropones studied in this regard, the C-3 oxo and the C-4 oxo species. The 3-substituted 4-oxoestratropones exhibited antitubulin activity according to Cl approximately Br > OCH3, whereas the 4-substituted 3-oxoestratropones exhibited activity according to OCH3 > Br approximately Cl. It is unclear if these substituent factors are purely electronic or steric effects or if the substituent operates indirectly by altering the conformation of the nonplanar troponoid ring. The estratropones represent a new class of tubulin binding agents with potential antiangiogenic utility.

A proposed mechanism for p-aminoclonidine allergenicity based on its relative oxidative lability

p-Aminoclonidine (apraclonidine) is a selective alpha 2 adrenergic agonist used to reduce intraocular pressure in the treatment of glaucoma. Use of apraclonidine is frequently associated with severe local allergic effects which warrant discontinuation of the drug in affected patients. We have assessed the oxidative lability of apraclonidine relative to a panel of adrenergic agonists and/or known allergens; amodiaquine, epinephrine, clonidine, and brimonidine. These compounds were compared by their electrochemical potentials as well as their oxidative lability in the presence of several oxidative enzyme systems (i.e., horseradish peroxidase, lactoperoxidase, myeloperoxidase, and diamine oxidase). The half-lives for enzymatic oxidation of these compounds were found to parallel the electrochemical oxidation potentials in the order: amodiaquine approximately epinephrine < apraclonidine << clonidine approximately brimonidine. The production of a reactive electrophilic intermediate of apraclonidine was demonstrated through the formation of two glutathione apraclonidine adducts from the horseradish peroxidase/H2O2-mediated oxidation of apraclonidine in the presence of glutathione. A mechanism for apraclonidine allergenicity in vivo is proposed wherein apraclonidine is bioactivated through oxidation to the bis-iminoquinone followed by protein conjugation to form an apraclonidine-protein hapten that elicits the immune response.

Mechanisms of adrenergic agonist induced allergy bioactivation and antigen formation

Reduction of elevated intraocular pressure with alpha 2 agonists has proved to be an exciting new therapeutic approach for the treatment of glaucoma. We have studied the chemical reactivities of several alpha 2 agonists and known allergens to elucidate the origin of the observed ocular allergic response to the alpha 2 agonist apraclonidine. The oxidation potentials of clonidine, apraclonidine, brimonidine, and two known allergens, amodiaquine, and epinephrine, were measured vs. a standard calomel electrode.. Agents that were oxidatively labile were treated with both chemical and enzymatic oxidants. Clonidine and brimonidine proved to be oxidatively stable in sharp contrast to apraclonidine which had an oxidation potential similar to that observed with epinephrine and amodiaquine, two known allergy-inducing agents. In addition, two glutathione-apraclonidine conjugates formed by the in-situ reaction of glutathione with an enzymatically oxidized apraclonidine intermediate were isolated and their structures determined using spectroscopic methods. The structures were shown to be analogous to those obtained with amodiaquine and epinephrine. Apraclonidine, like amodiaquine and epinephrine, possesses a hydroquinone-like subunit and can be readily oxidized and conjugated with thiols modeling well known hapten-forming reactions. Brimonidine, like clonidine, lacks the hydroquinone subunit and does not undergo the thiol conjugation reactions.

Identification of modified atropaldehyde mercapturic acids in rat and human urine after felbamate administration

3-Carbamoyl-2-phenylpropionaldehyde has recently been proposed [Thompson et al. (1996) Chem. Res. Toxicol. 9, 1225-1229] as a potential reactive metabolite of the anti-epileptic drug felbamate. This aldehyde was found to undergo rapid elimination to generate 2-phenylpropenal and reversible cyclization to generate 4-hydroxy-5-phenyltetrahydro-1,3-oxazin-2-one at physiological pH. 2-Phenylpropenal, an alpha,beta-unsaturated aldehyde commonly termed atropaldehyde, is a potent electrophile and undergoes rapid conjugation with glutathione. We sought to demonstrate the formation of atropaldehyde in vivo through the identification of mercapturic acids in rat and human urine after felbamate administration. In this paper, we describe the identification of both the reduced (N-acetyl-S-(2-phenylpropan-3-ol)-L-cysteine) and oxidized (N-acetyl-S-(2-phenyl-3-propanoic acid)-L-cysteine) mercapturic acids of atropaldehyde in rat and human urine. The reduced species was the more abundant in human (approximately 2:1) and rat (approximately 6:1) urine. These findings establish the possibility that atropaldehyde is formed from felbamate in vivo, undergoes glutathione conjugation, and is ultimately excreted in urine in the form of mercapturic acids. Thus, the proposed pathway of felbamate biotransformation, if confirmed in patients, could contribute to our understanding of the toxicities observed during felbamate treatment.

Synthesis and in vitro reactivity of 3-carbamoyl-2-phenylpropionaldehyde and 2-phenylpropenal: putative reactive metabolites of felbamate

We propose that 3-carbamoyl-2-phenylpropionaldehyde is an intermediate in the metabolism of felbamate, an anti-epileptic drug with a unique profile of the therapeutic activity, and undergoes a cascade of chemical reactions responsible for the toxic properties of the parent drug. To test this hypothesis, we have synthesized 3-carbamoyl-2-phenylpropionaldehyde and evaluated its in vitro reactivity. This molecule was found to be highly unstable at physiological pH (t1/2 < or = 30 s) and to undergo facile elimination to 2-phenylpropenal, an alpha, beta-unsaturated aldehyde commonly termed atropaldehyde. However, the predominant reaction pathway for 3-carbamoyl-2-phenylpropionaldehyde was reversible cyclization to generate 4-hydroxy-5-phenyltetrahydro-1,3-oxazin-2-one, a urethane that has a considerably longer half-life at physiological pH (t1/2 > or = 5 h) and may serve as a stable reservoir of the reactive aldehyde both in vitro and in vivo. Atropaldehyde is a potent electrophile and was found to exhibit cytotoxicity to cultured fibroblasts (50% growth inhibition (GI50) = 4.1 +/- 1.1 microM) comparable to the known unsaturated aldehyde toxins, 4-hydroxy-2-nonenal and acrolein. 3-Carbamoyl-2-phenylpropionaldehyde also exhibited significant cytotoxicity (GI50 = 53 +/- 8 microM), whereas 2-phenyl-1,3-propanediol monocarbamate (GI50 > 500 microM) and 3-carbamoyl-2-phenylpropionic acid (GI50 > 500 microM) were nontoxic. We have additionally demonstrated the formation of a glutathione-atropaldehyde conjugate from the in vitro incubation of 3-carbamoyl-2-phenylpropionaldehyde with glutathione. Thus, the potent cytotoxicity and potential allergenicity of atropaldehyde implicate this unsaturated aldehyde as a possible causative agent in the toxicities observed with felbamate treatment.

Use of GnRH agonist before hysterectomy: a cost simulation

OBJECTIVE

To evaluate the potential savings in cost of care derived from performing vaginal hysterectomies instead of abdominal hysterectomies in selected women with fibroid uteri equivalent in size to a 14-18 week gestation.

METHODS

Women 35-46 years of age undergoing hysterectomy for fibroid uteri were selected to allow application of conversion rates gained in a separate randomized study using leuprolide acetate depot 3.75 mg. Statewide public data for North Carolina's hospital discharges provided relative rates of hospital charges and leiomyomas for all hysterectomies, by age. Professional charges were omitted from the analysis. Estimated savings were projected to the national level.

RESULTS

During 1992 in North Carolina, 18,110 inpatient hysterectomies were performed for women of all ages; 28.1% of these were for uterine leiomyomas. For women 35-46 years old (12.7% of all hysterectomies), there were 1904 abdominal and 390 vaginal hysterectomies; the mean total charge for abdominal hysterectomy was $5590, and $4732 for the vaginal alternative. These statewide data provide missing elements to allow a national estimate of the potential savings of using GnRH agonist preoperatively. The projected national savings, if 1987 utilization data are used, was $4.6 million, nearly 1.4% of the inpatient charges. The 1992 value of these savings is $6.7 million.

CONCLUSION

The use of preoperative GnRH agonist therapy before hysterectomy for patients with a uterine size equivalent to a 14-18 week gestation represents a significant cost-saving alternative, increasing the use of vaginal hysterectomy and resulting in potential savings in direct inpatient medical care charges.

Cold induced rhabdomyolysis in carnitine palmyityl transferase deficiency

A case of carnitine palmityl transferase deficiency in skeletal muscle is described. The usual symptoms associated with this disease (recurrent muscle cramps or pain and pigmenturia) were observed but sudden exposure to cold precipitate rhabdomyolysis in this patient.

Symptomatic hypergastrinaemia with achlorhydria: reflief by antrectomy

A women had hypergastrinaemia associated with the variety of gastritis (Type A) that is associated usually with pernicious anaemia, together with recurring bouts of severe abdominal pain. Fasting serum gastrin levels ranged between 600 and 2750 pg/ml. There was a rise in serum gastrin levels after a standard protein meal, indicative of a large G cell mass, and a fall after intragastric HCI, which led to a trial of treatment with HCI; this gave some symptomatic relief. After surgical antrectomy there was a profound fall of serum gastrin from a pre-operative level of 2500 pg/ml to constant values of 16--25 pg/ml, and complete and lasting relief from the bouts of abdominal pain.

Quantitation of cell-mediated immunity: responses to dinitrochlorobenzene and ubiquitous antigens

T-lymphocyte immune capacity in man was assessed semiquantitatively by two in vivo procedures: the primary type of response to dinitrochlorobenzene and the secondary type of response, representing memory, to a group of five uniquitous antigens. Controlling for degree of illness proved important in assessing immune capacity in specific diseases; thus, the number of responders and mean score of semiquantitated responses was significantly lower in groups of patients with cancer and multisystem autoimmune disease when comparisons were made with healthy persons, but less so when comparisons were made with a group of subjects with other incapacitating diseases. A notable finding was the lack of correlation in the results of tests of cell-mediated immunity between the two procedures described. Depressed cell-mediated immunity shown in multisystem autoimmune disease is relevant to both predisposition to infection and the postulated role of thymic dysfunction in the pathogenesis of autoimmunity.

Human infection with a tapeworm, Bertiella sp., probably of African origin

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