Evaluation of the GastroPlus™ Advanced Compartmental and Transit (ACAT) Model in Early Discovery.

PURPOSE: The aim of this study was to evaluate the oral exposure predictions obtained early in drug discovery with a generic GastroPlus Advanced Compartmental And Transit (ACAT) model based on the in vivo intravenous blood concentration-time profile, in silico properties (lipophilicity, pKa) and in vitro high-throughput absorption-distribution-metabolism-excretion (ADME) data (as determined by PAMPA, solubility, liver microsomal stability assays). METHODS: The model was applied to a total of 623 discovery molecules and their oral exposure was predicted in rats and/or dogs. The predictions of Cmax, AUClast and Tmax were compared against the observations. RESULTS: The generic model proved to make predictions of oral Cmax, AUClast and Tmax within 3-fold of the observations for rats in respectively 65%, 68% and 57% of the 537 cases. For dogs, it was respectively 77%, 79% and 85% of the 124 cases. Statistically, the model was most successful at predicting oral exposure of Biopharmaceutical Classification System (BCS) class 1 compounds compared to classes 2 and 3, and was worst at predicting class 4 compounds oral exposure. CONCLUSION: The generic GastroPlus ACAT model provided reasonable predictions especially for BCS class 1 compounds. For compounds of other classes, the model may be refined by obtaining more information on solubility and permeability in secondary assays. This increases confidence that such a model can be used in discovery projects to understand the parameters limiting absorption and extrapolate predictions across species. Also, when predictions disagree with the observations, the model can be updated to test hypotheses and understand oral absorption.

Familial membranous glomerulopathy, toxic exposure and/or genetic sensibility?

Membranous nephropathy rarely occurs as a familial disease. We report two siblings (brother and sister) who presented with nephrotic syndrome and many vascular complications. HLA identities and potential toxic exposure may be concurring in these cases.

Recombinant human uncoupling protein-3 increases thermogenesis in yeast cells.

The long form of human uncoupling protein-3 (hUCP3L) is highly homologous to thermogenin (UCPI), the uncoupling protein of brown fat mitochondria, but is expressed predominantly in skeletal muscle. Its putative role is to regulate the coupling efficiency of oxidative phosphorylation and thus thermogenesis in skeletal muscle, a major thermogenic tissue in higher mammals. To study the functional relevance of hUCP3L, the protein was expressed in yeast cells under the control of the galactose promoter. Expression of hUCP3L induced a series of phenotype changes in the yeast cells. The cellular growth and the mitochondrial membrane potential were both diminished. The portion of cellular respiration coupled to oxidative phosphorylation decreased from 57% to 11% (P<0.001) and the cellular heat production, as measured by direct microcalorimetry, was increased by 33.3 +/- 3.2% (P<0.001) after induction of UCP3L. These observations demonstrate for the first time the intrinsic thermogenic properties of hUCP3L in intact cells.

High-throughput permeability pH profile and high-throughput alkane/water log P with artificial membranes.

This study reports on a novel, high-throughput assay, designed to predict passive, transcellular permeability in early drug discovery. The assay is carried out in 96-well microtiterplates and measures the ability of compounds to diffuse from a donor to an acceptor compartment which are separated by a 9-10 microm hexadecane liquid layer. A set of 32 well-characterized, chemically diverse drugs was used to validate the method. The permeability values derived from the flux factors between donor and acceptor compartments show a good correlation with gastrointestinal absorption in humans. For comparison, correlations based on experimental or calculated octanol/water distribution coefficients (log D(o/w,6.8)) were significantly lower. In addition, this simple and robust assay allows determination of pH permeability profiles, critical information to predict gastrointestinal absorption of ionizable drugs and difficult to obtain from cell culture experiments. Correction for the unstirred water layer effect allows to differentiate between effective and intrinsic membrane permeability and opens up the dynamic range of the method. In addition, alkane/water partition coefficients can be derived from intrinsic membrane permeabilities, making this assay the first high-throughput method able to measure alkane/water log P in the microtiterplate format.

Improving the oral bioavailability of the iron chelator HBED by breaking the symmetry of the intramolecular H-bond network.

Physicochemical analysis and Monte Carlo simulations were used to identify structural features which prevent oral absorption of HBED, a potent iron chelator. In water the dominant conformations of HBED involve the hydrophobic collapse of the two aromatic rings. These conformations are favored in polar media because they expose the polar phenolic hydroxy groups to the solvent and partially shield the nonpolar aromatic rings. In a less polar solvent such as chloroform, a symmetrical H-bond network between the carboxylates and the amines dominates the conformational space. This leads to the exposure of the phenolic hydroxy groups to the solvent, which is unfavorable for solvation. The low solubility of HBED in nonpolar solvents was confirmed experimentally by determination of the partition coefficients in octanol, chloroform, and cyclohexane and may explain the poor membrane permeability of this compound. The high conformational stability which disfavors partitioning into phospholipids is mainly due to the symmetrical H-bond network. Potentiometric titrations of a monoester of HBED in MeOH/water indicate that the protonation sequence was changed compared to that of the parent compound, suggesting that the symmetrical H-bond network was disrupted. Conformational analysis in chloroform confirmed that, in contrast to HBED, no symmetric interaction between the carboxylate and the nitrogen amines is possible in the half-ester and a variety of conformations which allow partial shielding of the polar phenolic OH groups are energetically possible. This theoretical model predicting a better solubility of the half-esters in nonpolar solvents was supported by the large increase in the partition coefficients in octanol, chloroform, and cyclohexane measured experimentally. The high absorbability predicted by physicochemical and computer simulation methods was corroborated by in vivo experiments in marmoset monkeys where the monoethyl ester derivative of HBED was well-absorbed orally while the parent compound was nearly ineffective in the same model.

Caco-2 cell permeability of a new (hydroxybenzyl)ethylenediamine oral iron chelator: correlation with physicochemical properties and oral activity.

This study describes the transport of CGP 75254A, a novel oral iron chelator, across Caco-2 cells in an attempt to model intestinal epithelial cell permeability in man. CGP 75254A was dosed to the apical side of Caco-2 cell monolayers, together with [14C]mannitol as an internal permeability standard. The apparent permeability (Papp) was calculated from the cumulative appearance of drug in the basolateral fluid with time. The [14C]mannitol Papp indicated that the Caco-2 monolayers remained intact and that the iron chelator was not toxic to the cells. Permeabilities of CGP 75254A were compared with the Caco-2 permeabilities of compounds of known absorption in man. The results predict that absorption of CGP 75254A is likely to be virtually complete at pH values between 5.5 and 7.0. However, at pH 8.0 permeability is predicted as negligible. Cell permeability data are in full accordance with key physicochemical properties of CGP 75254A and suggest that the drug is passively absorbed. The results, which suggest likely quantitative absorption in vivo, are supported by preliminary pharmacological experiments in marmosets.

Daily subcutaneous administration of recombinant human erythropoietin (rhEPO) in peritoneal dialysis patients: a European dose-response study.

In a prospective randomized open multicenter study, 107 anemic (Hct < = 28%) peritoneal dialysis (PD) patients were treated with s.c. rhEPO daily. The mean observation period was 299 days (range 14-479 days). Patients were randomly assigned to 3 groups with different initial doses: 5 U/kg (G5), 10 U/kg (G10), 20 U/kg (G20). Initial doses were maintained for at least 8 weeks unless the target Hct (30-35%) was achieved earlier. The weekly increase of Hct was significantly (p < 0.05) dose-dependent: 0.19% in G5, 0.5% in G10 and 0.94% in G20. In case of insufficient response (< 0.5% per week), the dose was doubled every 4 weeks. Final doses on achieving the target Hct ranged from 5 to 40 U/kg (median 20 U/kg). The dose was then reduced to 50% and adjusted individually. The median maintenance dose was 9.9 U/kg/day. No tendency towards higher blood pressure or intensification of antihypertensive treatment was observed. When rhEPO is administered daily, 10 U/kg/day (70 U/kg weekly) is the recommended starting dose. The need for higher doses used in unsatisfactory response, should lead to further examination to rule out iron deficiency and other reasons for non-response. The median maintenance dose reported here is the lowest published in the literature for PD patients and seems to be linked to the daily injections.

Continuous ambulatory peritoneal dialysis (CAPD) or center hemodialysis? Retrospective evaluation of the success of both methods.

In a retrospective study, the authors analysed the dialysis-technique success rate in 276 chronic renal patients. Of these, 137 patients have been treated with in center hemodialysis (CHD) from 1972 to 1989 and 139 with continuous ambulatory peritoneal dialysis (CAPD) from 1978 to 1989. The six-year technique success rate was 28% in CAPD and 31% in CHD (statistically not significantly different). Various risk factors influence the technique-success rate of both methods in the same way. The results suggest that in our center CAPD is as effective as CHD in the treatment of patients with end-stage renal failure.

Treatment of chronic renal failure: situation of CAPD.

The authors are using Continuous Ambulatory Peritroneal Dialysis (CAPD) in the treatment of chronic renal failure. Started in May 1978, their experience encompasses 19 patients (9 men, 10 women). The method, developed by Oreopoulos, consists of exchanging 2 liters of dialysate 4 times a day, 7 days a week. They report their clinical and biological results and the complications. The most frequent is peritonitis (1 episode per 9.3 patients months). The simplicity and the efficacy of CAPD permits them to treat 30% of the renal patients who need chronic dialysis.

[Decentralization of the ARTEMIS system in a nephrology service in a general hospital]. / Expérience de dècentralisation du système "ARTEMIS" dans un service de néphrologie en hôpital général.

"ARTEMIS" is a standardized and computerized medical file which is intended for improving the follow-up of hypertensive patients, the efficacy of treatment and for realising national-wide surveys. The software "LIED" of data base for "ARTEMIS" is nowadays transposable on mini-computer. In Nephrology Unit of General Hospital from Colmar, the system has been working since September 1985 with MICRO-MEGA E 32 (Thomson). The administrative and medical data are directly acquired by the doctors and secretaries of the Unit on a conversational mode from six terminals. There is no writing collecting of data. An evaluation of the system was realized with the 113 first hypertensive patients. The results were compared to those obtained from patients of Paris area.

Pharmacokinetics of cadralazine and its hydrazino-metabolite in patients with renal impairment after repeated administration of 5 mg once daily.

Since the hydrazino-pyridazine metabolite of cadralazine, CGP 22 639 is believed to contribute to the activity of the drug, its pharmacokinetics and that of cadralazine were investigated in 8 hypertensive patients with renal impairment. The creatinine clearance (CLcr) of patients ranged from 10 to 60 ml/min. The concentrations of cadralazine in plasma and urine, and of CGP 22 639 (plus its possible hydrazones) in plasma were measured after single and repeated administration of 5 mg of cadralazine once daily. A hypotension possibly linked to cadralazine treatment was recorded on day 3 for the patient with CLcr = 10 ml/min. Metabolite concentrations were found to be at least twice as high as in other patients indicating that in this patient, the daily dose of 5 mg was probably too high. The pharmacokinetics of cadralazine were not modified by repeated administration. The drug and its metabolite were eliminated more slowly in patients with low creatinine clearance. The t1/2 of CGP 22 639 was about twice the t1/2 of the unchanged drug. In patients whose CLcr ranged from 19-37 ml/min the mean accumulation factor of apparent CGP 22 639 was 1.7 times that of the unchanged drug. It shows that the apparent CGP 22 639 accumulated more than the unchanged drug. A starting daily dose of 2.5 mg of cadralazine in patients with CLcr < 40 ml/min appears to be suited to take into account the pharmacokinetics of CGP 22 639. This dose can be increased by 2.5 mg steps if the antihypertensive effect is not sufficient (maximum dose with CLcr < 40 ml/min: 10 mg).(ABSTRACT TRUNCATED AT 250 WORDS)

[Continuous ambulatory peritoneal dialysis in schizophrenia. Experimentation in 3 cases]. / La dialyse péritonéale continue ambulatoire chez les schizophrènes. Expérimentation dans trois cas.

The authors report their experience in using Continuous Ambulatory Peritoneal Dialysis (C.A.P.D.), in the treatment of chronic schizophrenia. This attempt refers to studies which confirm any role of endorphins in the origin of schizophrenia. Consecutively to american authors who found endorphins (molecular weight 3 300) in the dialysat of hemodialysed schizophrenics, they choose C.A.P.D. This continue technic of dialysis is more efficient than hemodialysis in removal of substances which molecular weight is between 1 500 and 5 000. This technic was used in 3 chronic schizophrenics: the disease has developed since 6 to 17 years and all the previous treatments failed. The duration of C.A.P.D. was 3 to 6 months. The only complication was one episode of inflammation of the peritoneum during 14 months of dialysis. Followed by the same staff with the AMDP 3 scale, the psychiatric evolution includes: --improvement and relapse in 2 patients (but we have to consider the difficulties of socioprofessional rehabilitation of these long term patients); --"clinical recovery" (17 months) in the third patient. The incidence of mothering and institutionalism is not negligible. Dosage of Met-enkephalin and beta-endorphin by radioimmunoassay in the drained dialysat did not show any difference between schizophrenics and the reference chronic renal patient. The results obtained with C.A.P.D. are not very satisfactory so far. But further research especially on the role of endorphins in schizophrenia and on their analysis technics in the body fluids perhaps will allow to treat schizophrenia again by dialysis.

[Evaluation of the control quality of arterial hypertension over a 10-year period at a hemodialysis center]. / Evaluation de la qualité du contrôle de l'hypertension artérielle pendant dix ans dans un centre d'hémodialyse.

Using the "Diaphane" computed medical record system enables multicentric statistical studies to be conducted. With this system, the quality of arterial hypertension control (supine systolic and diastolic arterial pressure before and after dialysis) was evaluated over a 10-year period in chronic haemodialysis patients in comparison with a multicentric population. A continuous statistical study of the results showed a regular voluntary decrease in arterial pressure. The evaluation of the quality of medical care represented by this comparison contributes to a therapeutic improvement.

[Continuous ambulatory peritoneal dialysis]. / La dialyse péritonéale continue ambulatoire.

In contrast with hemodialysis (HD) Continuous Ambulatory Peritoneal Dialysis (CAPD) is a permanent dialysis procedure proposed to the chronic renal patients. Through a permanent peritenoal catheter the patients exchange 2 litres of dialysate 4 times a day, 7 days a week, as soon as the dialysat/plasma concentration for urea reaches 1. Inflow and outflow of the fluid is obtained by gravity, without machine. The short term survival rate is comparable between HD and CAPD. After 5 years, some patients, loosing the residual renal function, need to increase the possibilities of CAPD. The recent disconnect systems reduce the rate of peritonitis down to 1 episode every 36 months. With the actual technology the severe complications such as sclerosing peritonitis decrease or even disappear. Maintenance of an adequate nutritional status in the patients remains an often difficult problem. CAPD may be proposed to nearly all the patients who prefer to be treated at home: children, working adults, diabetics and elderly. Long term studies are still needed to follow the peritoneal performances over time.

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An exceptionally stable 1:2 complex [FeL(2)](3-) is formed from the ligand H(3)L and Fe(III). In contrast, the affinity of this ligand for other biometals is relatively small. These properties make H(3)L a highly promising candidate for medical applications (e.g. for the treatment of iron overload).

A 5-year prospective follow-up study in essential cryofibrinogenemia patients.

INTRODUCTION: Cryofibrinogenemia may be essential, or secondary to diseases such as neoplasia, infection, thrombosis, and collagen vascular diseases. In a previous study, we reported the occurrence of neoplasia in some essential cryofibrinogenemia patients after a short period of follow-up. PURPOSE: We performed a prospective multi-center 5-year follow-up study in essential cryofibrinogenemia patients (2005-2009). RESULTS: 23 patients with essential cryofibrinogenemia were included, mean age 59 years (range: 33-79), 14 males. After a mean follow-up period of 24 months, 11/23 (47%) of cases that were initially diagnosed as essential cryofibrinogenemia were found to have an underlying lymphoma (6 T lymphoma and 5 B lymphoma). CONCLUSION: This prospective study suggests that some cases of cryofibrinogenemia that are initially considered as essential, may have underlying lymphoma. Thus, we further suggest that regular follow-up should be performed in patients with essential cryofibrinogenemia.