Preclinical evaluation of radiopharmaceutical toxicological prerequisites

Right ventricular myxoma in elderly is very rare and this is the 36th case report of right ventricular myxoma in Japan. A healthy 71-year-old female with no symptoms or constitutional signs except heart murmur was hospitalized. Findings of transthoracic echocardiogram, CT scan, MRI and angiocardiogram demonstrated a mobile tumor in the right ventricular outflow tract. Transesophageal echocardiogram clearly revealed that the stalk was arising from the right ventricular free wall. Under cardiac arrest, right atriotomy was made and a gelatinous tumor (4.5 x 2 x 2 cm in size, 7.3 g in weight) was excised with 5 mm of surrounding endocardium and a few millimeters of underlying myocardium through the tricuspid valve. Histopathologically, the tumor was diagnosed as a myxoma. Her postoperative course was uneventful.     

Reduction of adhesions after uterine myomectomy by Seprafilm membrane (HAL-F): a blinded, prospective, randomized, multicenter clinical study. Seprafilm Adhesion Study Group

OBJECTIVE: To assess the safety and efficacy of Seprafilm (HAL-F), Bioresorbable Membrane, (Genzyme Corporation, Cambridge, MA) in reducing the incidence, severity, extent, and area of uterine adhesions after myomectomy. DESIGN: Prospective, randomized, blinded, multicenter study. Adhesion reduction was assessed by an independent, blinded, gynecologic surgeon who reviewed videotapes of each patient's second-look laparoscopy. SETTING: Nineteen institutions across the United States. PATIENT(s): One hundred twenty-seven women undergoing uterine myomectomy with at least one posterior uterine incision > or = 1 cm in length. INTERVENTION(s): Patients were randomized to treatment with Seprafilm or to no treatment at the completion of the myomectomy. MAIN OUTCOME MEASURE(s): The incidence, severity, extent, and area of uterine adhesions at second-look laparoscopy. RESULT(s): The incidence, measured as the mean number of sites adherent to the uterine surface, was significantly less in treated patients (4.98 +/- 0.52 [mean +/- SEM] sites) than in no treatment patients (7.88 +/- 0.48 sites) as were the mean uterine adhesion severity scores (1.94 +/- 0.14 versus 2.43 +/- 0.10; treatment versus no treatment, respectively), mean extent scores (1.23 +/- 0.12 versus 1.68 +/- 0.10), and mean area of adhesions (13.2 +/- 1.67 versus 18.7 +/- 1.66 cm2). No adverse events occurred that were judged to be related to the use of Seprafilm. CONCLUSION(s): In this multicenter study, treatment of patients after myomectomy with Seprafilm significantly reduced the incidence, severity, extent, and area of postoperative uterine adhesions. Additionally, Seprafilm treatment was not associated with an increase in postoperative complications.     

Implant placement in large edentulous ridges expanded by GBR using a bioresorbable collagen membrane

In order to determine the specific effects of radical-induced reactions in the absence of complicating excited-state pathways, four different thiohydroxamic esters and their parent molecule, N-hydroxypyridine-2(1H)-thione, have been studied in murine L1210 leukemia cells for their ability to produce photobiological damage. Irradiation (lambda exc = 355 nm) of cells in the presence of thiopyridone esters, specific photolytic precursors of sulfur-, carbon- and oxygen-centered radicals, caused toxicity that was unambiguously demonstrated to result from radical photosensitization mechanisms. Cellular morphological changes were observed following irradiation but apoptosis was not found to take place. A good correlation was evident between lipid peroxidation, measured by the thiobarbituric acid method, and phototoxicity, assessed by the trypan blue exclusion assay, indicating that the ester derivatives exert their effects mainly in plasma and/or subcellular membranes. Irradiation performed under deaerated conditions also induced significant phototoxicity but the effects of deaeration were dependent on the ester used and are discussed in terms of the nature of the primary radical species generated in each case. Irradiation of L1210 cells in the presence of N-hydroxypyridine-2(1H)-thione, a nonspecific, photochemical source of hydroxyl radical, was also found to trigger phototoxicity and lipid peroxidation. However in this case, photodamage cannot yet be definitely attributed to a radical or type II mechanism although the apparent oxygen independence of phototoxicity would indicate that type II contribution is not significant.     

Preclinical evaluation of anticancer drugs: a model remaining a model!

Two criteria are firstly used in the selection of new anticancer agents:--originality of the mechanism of action and significant experimental antitumor activity in an in vivo animal model. Murine tumors grafted in syngenic mice and human tumor xenografts implanted in nude mice are old models which continue to be widely used. Such models are useful but have the tendency to select many false positives (compounds active in mice but inactive in patients). This discrepancy can be explained by differences due to biological materials and also to the methodologies used in laboratories and clinic. Such models will certainly continue to play a major role in the future but they will have to be used in conditions more relevant for clinical extrapolation. Transgenic mice developing in situ tumors constitute new innovative models for in vivo evaluation of anticancer agents. Finally, a putative new class of antitumor agents emerges with the signal transduction modulators: such compounds have antitumor and toxicological properties very different from those of conventional chemotherapeutic agents. If the first representatives prove to be useful in clinic, rules for toxicology, preclinical and clinical evaluation will have to be changed.     

Preclinical evaluation of the Kyocera Gyro centrifugal blood pump for cardiopulmonary bypass

The Kyocera Gyro pump has been developed as a completely seal-less centrifugal pump to overcome the problems of the conventional centrifugal pumps. The Gyro pump is a double pivot bearing-supported centrifugal pump with several specific design features, including its eccentric inlet port. We investigated the feasibility of the Gyro pump for cardiopulmonary bypass (CPB) in a bovine model, comparing it with the BioMedicus pump (BP-80). Ten healthy calves (5: Gyro pump, 5: BP-80) underwent 6 h of mildly hypothermic CPB at approximately 33 degrees C. Both pumps provided more than 50 ml/kg/min without any incidents. The haemodynamics of both groups remained stable within the normal range. All haematology and biochemistry data demonstrated no significant differences between the two groups. However, values of plasma-free haemoglobin and lactate dehydrogenase were less throughout the experiments of the Gyro pump than those of the BP-80. To obtain flow equivalent to that of the BP-80, the Gyro pump needed less rotational speeds than the BP-80 (2749.7 +/- 233.3 versus 3170.6 +/- 300.8 rpm. p < 0.05). Less rotational speed in addition to the difference in operating principle may contribute to less blood damage during the CPB OF the Gyro pump. After pumping for CPB, no leakage or thrombus formation was observed in either pump. The present study indicated that the Kyocera Gyro pump can be applied as a centrifugal pump for CPB with the same performance as the BP-80 and with relatively less haemolysis than the BP-80.     

Prevention of postoperative abdominal adhesions by a sodium hyaluronate-based bioresorbable membrane: a prospective, randomized, double-blind multicenter study

Two populations of hydrogen protons exist in magnetic resonance imaging: free protons and bound protons. Bound protons do not contribute to normal MR signal because they resonate somewhat off the center frequency of water. A special pulse sequence called magnetization transfer contrast (MTC) was developed to compensate for this off-resonance limitation. A saturation transfer of bound protons occurs during MTC, enabling a transfer of energy to the free proton pool and thereby contributing to the overall MR signal. This article describes MTC, reviews its applications and explains how it improves lesion conspicuity, small vessel detail and background suppression.     

Sintered carbonate apatites as bioresorbable bone substitutes

The dissolution behavior of sintered carbonate apatite was investigated in a 10 mM/L acetic acid solution adjusted to pH 5.0 at 37 degrees C, and compared to that of sintered hydroxyapatite and bone apatite for the purpose of establishing some similarities between the physicochemical dissolution of apatite biomaterials in vitro and their ability to be resorbed by osteoclasts in vivo. Both the sintered carbonate apatite and the bone apatite dissolved to an appreciable extent. Their solution compositions changed in an almost identical manner until toward the end of the reaction. The solution compositions for sintered carbonate apatite at 30 s was comparable with that for sintered hydroxyapatite at 3.8 days with respect to the degree of supersaturation, indicating that the former specimen is much more soluble than the latter specimen. Osteoclasts which were obtained from the long bones of 1-day-old neonatal rabbits resorbed bone and sintered carbonate apatite, but not sintered hydroxyapatite. These findings suggest that sintered carbonate apatites, which have characteristics that can be favorably compared with those of bone, especially with respect to its reactivity to acid media, would be useful as bioresorbable bone substitutes.     

Preclinical evaluation of single-cell oils that are highly enriched with arachidonic acid and docosahexaenoic acid

Measurement of the energy cost of walking in children with cerebral palsy or spina bifida is difficult due to the cumbersome nature of equipment used to assess oxygen consumption. Such information collected with a lightweight telemetric system, the Cosmed K2, correlated well with that from a non-portable breath-by-breath system associated with a treadmill. The K2 did not significantly affect regular gait pattern as measured by gait analysis, and repeatability was satisfactory. Measurement of the energy cost of walking in the individual is unreliable in detecting differences of less than 10%; comparison between groups is more useful.     

Studies on calf salmonellosis. 3. Preclinical evaluation of a Smd. Salmonella dublin live vaccine

Results of preclinical assay, preparation and conservation of a S.-dublin live vaccine based on streptomycin dependent mutants and for oral application are demonstrated and discussed in detail. The used oral vaccine is very good tolerated by calves and results in stable immunity after administration of a daily dose of 5 x 10(10) bis 1 x 10(11) living Smd.-mutants for 10 consecutive days. Complete immunity developes in calves within a period of two weeks after the last antigen administration and persists up to the age of 5 to 6 months. Conserving the vaccine at low temperatures (-15 degrees C) the number of living organism is far-reaching preserved in the first 5 months after preparation. After thawing the vaccine is to be used within a period of 3 days. With respect to the preparation of the live vaccine on semisynthetic nutritiv media some informations are given concerning the improvement of bacterial yield.     

Preclinical evaluation of a novel group B meningococcal conjugate vaccine that elicits bactericidal activity in both mice and nonhuman primates

Group B meningococcal (GBM) conjugate vaccines were prepared using chemically modified N-propionylated polysialic acid, from Escherichia coli K1 polysaccharide capsule, coupled by reductive amination to tetanus toxoid and purified recombinant GBM porin (rPorB). All conjugates elicited high antibody levels in mice with good booster responses. However, only rPorB conjugates elicited bactericidal activity specific against a broad spectrum of five different GBM serotypes. Bactericial activity was completely inhibited by free N-propionylated polysaccharide. In baboons and rhesus monkeys, rPorB conjugates elicited high antibody titers, with IgG booster responses 9- to 15-fold higher than primary responses. Bactericial activity increased 19- to 39-fold over preimmune values, using rabbit complement; increased bactericial activity was also confirmed with human and monkey complement. IgG cross-reactivity for unmodified N-acetyl polysaccharide was <5% for 79% of mice and <10% for 80% of primates. These studies strongly suggest that the N-propionylated polysialic acid-rPorB conjugate is an excellent vaccine candidate for human use.     

Preclinical drug development paradigms for chemopreventives

Preclinical screening studies and animal efficacy testing models currently are used by the National Cancer Institute's chemoprevention drug discovery program to assess and identify chemical agents and natural products that may have the potential to prevent human cancer. Identification of potential cancer preventing agents begins by subjecting each compound to a sequential series of short-term, in vitro prescreens of mechanistic, biochemical assays to provide quantitative data to help establish an early indication of chemopreventive efficacy and to assist in prioritizing agents for further evaluation in longer-term, in vitro transformation bioassays and whole animal models. Promising chemical agents or combinations of agents that work through different inhibitory mechanisms subsequently are tested in well-established, chemically induced, animal tumor models, which include models of the lung, bladder, mammaries, prostate, and skin. These preclinical bioassays afford a strategic framework for evaluating agents according to defined criteria, and not only provide evidence of agent efficacy, but also serve to generate valuable dose-response, toxicity, and pharmacokinetic data required prior to phase I clinical safety testing. Based on preclinical efficacy and toxicity screening studies, only the most successful agents considered to have potential as human chemopreventives progress into clinical chemoprevention trials.     

Preclinical antitumor activity of water-soluble paclitaxel derivatives

PURPOSE: Five water-soluble paclitaxel derivatives were extensively evaluated for their antitumor activities relative to the parent drug. METHODS: Both subcutaneous (s.c.) murine (M109 lung) and human (A2780 ovarian, L2987 lung) tumor models were used for this purpose. RESULTS: Consecutive daily intravenous (i.v.) paclitaxel therapy of mice bearing s.c. M109, beginning on day 4 or 5 posttumor implant and continuing for 5 days, resulted in a range of maximum gross log cell kill (LCK) values (reflective of delays in tumor growth) and maximum relative median survival time (% T/C) values (reflective of increases in lifespan) of 1.0-2.1 and 132-162% (and one outlying result of 235%), respectively. Against the same tumor model, using the same treatment schedule, each of the water-soluble derivatives was active, with maximum LCK of 1.3-2.5 and T/C of 124-254%. These LCK and %T/C values were always within 0.5 LCK and 15%, respectively, of the concomitantly obtained maximum effects of paclitaxel. When tested in several experiments against staged (50-100 mg) s.c. A2780 tumors, using various i.v. treatment schedules, the water-soluble derivatives achieved a maximum LCK of 1.4-3.8. Evaluated in parallel, paclitaxel achieved a maximum LCK of 2.1-4.5 following every other day x 5 i.v. therapy. When paclitaxel was assayed in several experiments using the staged (50-100 mg) s.c. L2987 tumor model, maximum LCK of 0.9->4.1 were produced following every other day x 5 i.v. therapy. Concomitant testing of the water-soluble derivatives, using the same i.v. treatment schedule, resulted in maximum LCK of 0.2->4.1. In each of the tumor models used, the consistently active, and usually the most active, water-soluble derivative was BMS-185660. The levels of activity observed were comparable (within 1 LCK) to those achieved concomitantly using paclitaxel, and its potency was only slightly inferior to the parent drug. CONCLUSIONS: Based on the evaluations performed in three distal site tumor models, we conclude that BMS-185660 is a water-soluble paclitaxel derivative with preclinical antitumor activity comparable to that of the parent drug.     

Preclinical assessment of hypoxic marker specificity and sensitivity

PURPOSE: In the search for a sensitive, accurate, and noninvasive technique for quantifying human tumor hypoxia, our laboratory has synthesized several potential radiodiagnostic agents. The purpose of this study was to assess and compare the hypoxic marking properties of both radioiodinated and Tc-99m labeled markers in appropriate test systems which can predict for in vivo activity. MATERIALS AND METHODS: Preclinical assessment of hypoxic marker specificity and sensitivity employed three laboratory assays with tumor cells in vitro and in vivo. Radiolabeled marker uptake and/or binding to whole EMT-6 tumor cells under extremely hypoxic and aerobic conditions was measured and their ratio defined hypoxia-specific factor (HSF). Marker specificity to hypoxic tumor tissue was estimated from its selective avidity to two rodent tumors in vivo, whose radiobiologic hypoxic fractions (HF) had been measured. The ratios of % injected dose/gram (%ID/g) of marker at various times in EMT-6 tumor tissue relative to that in the blood and muscle of scid mice were used to quantify hypoxia-specific activity. This tumor in this host exhibited an average radiobiologic HF of approximately 35%. As well, nuclear medicine images were acquired from R3327-AT (HF approximately =15%) and R3327-H (no measurable HF) prostate carcinomas growing in rats to distinguish between marker avidity due to hypoxia versus perfusion. RESULTS: The HSF for FC-103 and other iodinated markers were higher (5-40) than those for FC-306 and other Tc-99m labeled markers. The latter did not show hypoxia-specific uptake into cells in vitro. Qualitative differences were observed in the biodistribution and clearance kinetics of the iodinated azomycin nucleosides relative to the technetium chelates. The largest tumor/blood (T/B) and tumor/muscle (T/M) ratios were observed for compounds of the azomycin nucleoside class in EMT-6 tumor-bearing scid mice. These markers also showed a 3-4 x higher uptake into R3327-AT tumors relative to the well-perfused R3327-H tumors. While both FC-306 and CERETEC rapidly distributed at unique concentrations to different tissues, their avidity to EMT-6 and R3327-AT tumors did not correlate with tumor HF. CONCLUSIONS: The halogenated azomycin nucleosides with the lowest lipid/water partition coefficient values were found to yield the optimal hypoxia-specific signal in these animal tumors. Our Tc-99m-labeled azomycin chelates showed little or no hypoxia-specific uptake and had in vivo biodistribution and clearance kinetics similar to those of CERETEC, a perfusion agent with no known hypoxic binding activity.     

Preclinical evaluation of 111In-labeled B3 monoclonal antibody: biodistribution and imaging studies in nude mice bearing human epidermoid carcinoma xenografts

Biodistribution and imaging characteristics of monoclonal antibody B3 were evaluated in nude mice bearing A431 human epidermoid carcinoma xenografts. B3 is a murine IgG1k, recently isolated, reacting with a carbohydrate epitope abundantly and uniformly expressed by most carcinomas. B3 was conjugated to a new backbone-substituted derivative of diethylenetriaminepentaacetic acid, 2-(p-isothiocyanato benzyl)-cyclohexyl-diethylenetriaminepentaacetic acid, and labeled with 111In. Tumor-bearing mice were given i.v. injections of approximately 5 microCi of either 111In-B3 or 111In-MOPC-21, an isotype-matched control, and sacrificed in groups of five at 6 h and daily up to 168 h. Imaging was performed at 24, 72, and 144 h. Significant differences were observed in tumor uptake at all time points with peak values at 48 h (25 +/- 5.2% versus 6.3 +/- 0.4% of the injected dose/g tissue) (mean +/- SD) for 111In-B3 and 111In-MOPC-21, respectively (P < 0.001). All tumor to organ ratios increased with time for 111In-B3. In particular, tumor:liver ratios rose from 3.2 +/- 0.6 at 24 h to 6.3 +/- 1.2 at 168 h. Imaging results showed selective and progressive accumulation of 111In-B3 at the tumor site, whereas 111In-MOPC-21 did not show specific localization. In summary, 111In-labeled B3 demonstrated good and specific tumor targeting, which warrants its future clinical evaluation.     

Preclinical characterization of an anti-tat ribozyme for therapeutic application

A hammerhead ribozyme retroviral construct, denoted RRz2, targeting the coding region of the human immunodeficiency virus type 1 (HIV-1) tat gene, has shown itself to be effective in a range of test systems. Inhibition of the replication of HIV-1 IIIB and primary drug-resistant strains in pooled transduced CEMT4 cells was consistently found to be more than 80% compared with the control-vector transduced cells, whereas a mutant RRz2 gave approximately 45% inhibition. A multiple HIV-1 passage assay showed the absence of emergence of mutations within the specific viral RNA ribozyme target sequences. This lack of generation of ribozyme "escape mutants" occurred despite the almost complete disappearance of a HIV-1 quasi-species in the testing virus. When RRz2 was tested in peripheral blood lymphocytes (PBLs) from HIV-1-infected patients, paired analysis showed that cell viability in the ribozyme-transduced HIV-1-infected PBLs was significantly higher than that in the vector-transduced cells. This difference in viability (vector versus RRz2) was not observed in PBLs from non-HIV-1-infected donors. Taken together, these results indicate that the transfer of an anti-HIV-1 ribozyme gene into human T lymphocytes could have major impact on viral replication and T cell viability in the HIV-1-infected individual.     

Preclinical cognitive markers of dementia of the Alzheimer type.

56 nondemented elderly normal control (NC) Ss were studied at 3 consecutive annual administrations of the California Verbal Learning Test (CVLT). NC Ss with a positive family history for progressive dementia performed significantly worse than individuals with a negative family history for progressive dementia on several quantitative and qualitative indices of the CVLT and were more likely to undergo changes in diagnostic status over time (i.e., develop dementia of the Alzheimer type [DAT]). Stepwise discriminant function analyses of critical CVLT indices of the NC Ss and of 25 patients with mild DAT classified 5 NC Ss as DAT patients 1–2 yrs prior to their eventual changes in diagnostic status. Results suggest that specific memory deficits may serve as preclinical cognitive markers for DAT, especially in individuals with risk factors for DAT such as a positive family history. (PsycINFO Database Record (c) 2010 APA, all rights reserved)