Preclinical Evaluation Of New Drugs Research Articles

Comprehensive Review on the Genus Haloxylon: Pharmacological and Phytochemical Properties.

This review aimed to review the biological, pharmacological, and phytochemical aspects of the genus Haloxylon. Plants of the genus Haloxylon have been used for a long time in traditional medicine, and they are distributed in the western Mediterranean region to the Middle East, Iran, Mongolia, Burma, and southwest China. The studied parts of Haloxylon species include aerial parts, leaves, branches, seeds, roots, rhizosphere, soil, and whole plants, used to treat several diseases, including sexual disorders, hepatobiliary disorders, eye disorders, skin diseases and hemorrhoids, diarrhea, and effective in the treatment of various ailments such as snake bite, stomach ache, diabetes, wounds, earache and sciatica pain, windbreak dune fixation, feeding of livestock and firewood. Till now, no review on the genus Haloxylon has been conducted. This review aimed to provide updated information on the genus Haloxylon, including traditional medicinal uses, valorization and exploitation of medicinal plants, phytochemistry, botanical characterization, pharmacological and toxicological research focusing on the medicinal properties of several Haloxylon species, especially their antioxidant, antibacterial, anti-inflammatory, cytotoxic and antifungal activities, as well as the effect of each bioactive molecule isolated from these species and their pharmacological use, including the preclinical evaluation of new drugs. The present work was conducted using various scientific databases, including Science Direct, Scopus, PubMed, Google Scholar, etc. Correct plant names were verified from plantlist.org. The results of this search were interpreted, analyzed, and documented based on the obtained bibliographic information. Among all species of the Chenopodiaceae family, 6 species of the Haloxylon genus have approved antioxidant activity, 5 species have antibacterial activity, 3 species have anti-inflammatory activity, 2 species have cytotoxic activity, and 3 species have antifungal activity. The majority of the chemical constituents of this plant include flavonoids, alkaloids, phenols, saponins, glycosides, and tannins. Among them, the main bioactive constituents would be present in the alkaloid fraction. The study of more than 9 Haloxylon plants has identified more than 46 compounds. Pharmacological research proved that crude extracts and some pure compounds obtained from Haloxylon had activities for the treatment of different diseases. The objective of the present study was focused on antioxidant, antibacterial, anti-inflammatory, cytotoxic and antifungal diseases. From the study of the phytochemistry of the Haloxylon family, it was concluded that all studied plants had active compounds. Among them, 11 isolated molecules have medicinal activities with antioxidant properties, 10 molecules showed antibacterial effects, more than 6 molecules have anti-inflammatory properties, more than 9 isolated molecules have medicinal activities against cytotoxic diseases, and more than 28 molecules have antifungal effects. Therefore, the safety of Haloxylon herbal medicine should be considered a top priority in the early stages of development and clinical trials. Several previously conducted studies have validated multiple traditional uses of Haloxylon species. Further research is needed on Haloxylon plants before they can be fully utilized in the clinic as a potent drug candidate, as researchers are mainly focusing on alkaloids, diterpenoids, and triterpenoids, whereas there are many other types of compounds that may possess novel biological activities.

Generation of cynomolgus monkey airway, liver ductal, and kidney organoids with pharmacokinetic functions

Over the past decades, the pre-clinical evaluation of new drugs requires toxicological screening in animal models. The development of non-animal and nonclinical screening models could potentially play a role in the prediction of human pharmacokinetics of new drug candidates. In this study, we established stable organoids of the cynomolgus monkey airway, liver ductal, and kidney that could be passaged and cryopreserved. Drug sensitivity analyses revealed that very low doses of gemcitabine and 5-fluorouridine were toxic to the airway, liver ductal, and kidney organoids. Only high doses of regorafenib were toxic to liver ductal organoids while airway organoids were resistant to all doses of pemetrexed. These organoids showed tissue-specific expression of drug-metabolizing enzymes and drug transporter genes with liver ductal organoids exhibiting the most significant expression of all drug-metabolizing enzymes and transporters. The systematic evaluation of the pharmacokinetic functions of the cynomolgus monkey kidney, liver ductal, and airway organoids could find application in the pre-clinical toxicological studies of new drugs.

Mouse model of NASH that replicates key features of the human disease and progresses to fibrosis stage 3.

Nonalcoholic fatty liver disease (NAFLD) is the most common liver disease in the United States and the world; with no Food and Drug Administration–approved pharmacological treatment available, it remains an area of unmet medical need. In nonalcoholic steatohepatitis (NASH), the most important predictor of clinical outcome is the fibrosis stage. Moreover, the Food and Drug Administration recommends that clinical trials for drugs to treat this disease include patients with fibrosis stage 2 or greater. Therefore, when using animal models for investigating the pathophysiology of NAFLD and for the preclinical evaluation of new drugs, it is important that the animals develop substantial fibrosis. The aim of this study was to develop a mouse model of NAFLD that replicated the disease in humans, including obesity and progressive liver fibrosis. Agouti yellow mutant mice, which have hyperphagia, were fed a Western diet and water containing high‐fructose corn syrup for 16 weeks. Mice became obese and developed glucose intolerance. Their gut microbiota showed dysbiosis with changes that replicate some of the changes described in humans with NASH. They developed NASH with activity scores of 5–6 and fibrosis, which was stage 1 after 16 weeks, and stage 3 after 12 months. Changes in liver gene expression assessed by gene‐set enrichment analysis showed 90% similarity with changes in human patients with NASH. Conclusion: Ay mice, when fed a Western diet similar to that consumed by humans, develop obesity and NASH with liver histology, including fibrosis, and gene expression changes that are highly similar to the disease in humans.

Traditional Uses, Pharmacological, and Phytochemical Studies of Euphorbia: A Review.

Plants of the genus Euphorbia have long been used as traditional medicine in China, Europe, America, Turkey, India, Africa, Iran, and Pakistan for their great medicinal value and health benefits. Their stems, leaves, roots, and latex are widely used to treat respiratory infections, body and skin irritations, digestive disorders, inflammatory infections, body pain, snake or scorpion bites, pregnancy, sensory disturbances, microbial and anticancer diseases. This review aims to provide updated information on the genus Euphorbia, including traditional medicinal uses, valuation and exploitation of medicinal plants, phytochemistry, botanical characterization, pharmacological and toxicological research focused on the medicinal properties of several Euphorbias in particular their antibacterial, anti-tumor, and cell manifestations, in addition to the effect of each isolated bioactive molecule from these species and their pharmacological use including preclinical evaluation of new drugs. This work was conducted using scientific databases such as: PubMed, Google Scholar, Scopus, Science Direct, etc. In addition, ChemDraw software has been used for the drawing of chemical molecules. The correct names of the plants were confirmed from plantlist.org. The results of this review research were interpreted, analyzed and documented based on the bibliographical information obtained. Among all the species of the Euphorbiaceae family, 15 species have been demonstrated to exhibit anticancer activity, 21 species have antibacterial activity, and 10 species have cytotoxic activity. The majority of the chemical constituents of this plant include triterpenoid glycosides, diterpenoids, flavonoids, and the 4α-methyl steroids. Among them, the main bioactive constituents are present in the diterpenoid fraction. The study of more than 33 steroid plants identified more than 104 compounds. Pharmacological research proved that the crude extracts and some pure compounds obtained from Euphorbia had activities for the treatment of different diseases. The objective of the present study was focused on cytotoxic, antibacterial and antitumor diseases. The study of the phytochemistry of the Euphorbia families led to the conclusion that all the plants studied had active compounds, of which 27 plants were characterized by their cytotoxic effects, 7 had antibacterial effects and 10 plants had anti-tumor activities. Therefore, the safety of Euphorbia herbal medicine should be considered a top priority in the early stages of development and clinical trials. Many previous studies have validated many traditional uses of Euphorbia species. The latex of some Euphorbia species seems to be toxic however, studies dealing with the safety and quality of these species are still incomplete. Extensive studies are needed on the Euphorbia plants before they can be fully used in clinics as a potent drug candidate, as researchers are focusing mainly on diterpenoids and triterpenoids, while there are many other types of compounds that may possess new biological activities.

Abstract GMM-021: UTILIZATION OF PATIENT-DERIVED TUMOR XENOGRAFT (PDX) MODELS IN ONCOLOGY

Abstract BACKGROUND: The 5-year survival rate of patients with recurrent epithelial ovarian cancer is only 30%, in part due to relapse and resistance to first-line platinum-based chemotherapy. Even with marked progress toward understanding ovarian cancer biology, the translation of research findings into new therapies is still an enormous barrier to progress. Recent data suggests a 90% failure rate for new oncology drugs in the clinic. Development and preclinical testing of new cancer therapies has been limited by the availability of clinically relevant models that recapitulate the molecular and phenotypic characteristics of primary ovarian cancers. To overcome this barrier, we have initiated collaborative project between Stephenson Cancer Center (SCC) and Oklahoma Medical Research Foundation (OMRF) with the goal to generate a biobank of patient-derived xenograft (PDX) models derived directly from ovarian cancer patients undergoing therapy. RESULTS: PDX tumor models are generated in the Patient-Derived Xenograft and Preclinical Therapeutics (PDX-PCT) Core at OMRF and used to improve preclinical evaluation of new drugs towards more personalized medicine. We have collected blood samples and tumor tissues from consenting patients having primary debulking surgery at Stephenson Cancer Center since 2015 (>140 unique patients). Fresh tumor tissue is minced into small tumor chunks (~2 mm) and implanted into immunocompromised mice. PDXs are expanded for 3-4 passages and characterized based on tumor type, histology and molecular characteristics. Immunohistochemical and molecular analysis showed that histology of the original patient tumors as well as the expression of commonly used markers for high-grade serous ovarian cancer such as cytokeratin, PAX8 and WT1 are perfectly maintained in the derivative PDX lines. Genotyping of patients' tumors and their corresponding PDXs using Illumina's Exome Array revealed that single nucleotide polymorphism (SNP) profile found in the original tumors is perfectly maintained in PDX lines. One of the PDX limitations is that human tumor stromal and immune cells are being replaced with mouse equivalents upon in vivo propagation of PDXs, which negatively affects quality of genomic or proteomic analyses. To overcome this challenge, we optimized a method to deplete mouse cells from PDX tumors by magnetic cells separation. Our data showed that ovarian cancer PDXs contain around 28-54% of human tumor cells, where the rest are mouse cells. We also optimized protocols to utilize pure population of human tumor cells isolated from PDXs to transduce these with lentiviral vectors expressing GFP and/or luciferase to generate luciferized PDXs. Luciferized ovarian PDXs are excellent models used for non-invasive orthotopic tumor growth and drug response monitoring. CONCLUSIONS: Collection of our PDXs illustrates heterogeneity and diversity of human ovarian tumors. However, each PDX maintains essential molecular features of the original patients' tumor. Our goal is to generate clinically faithful ovarian tumor models that will provide a platform to learn more about cancer biology and to screen these for new better therapies. Citation Format: Magdalena Cybula, Katherine Moxley, Lin Wang, Luyao Wang, Magdalena Bieniasz. UTILIZATION OF PATIENT-DERIVED TUMOR XENOGRAFT (PDX) MODELS IN ONCOLOGY [abstract]. In: Proceedings of the 12th Biennial Ovarian Cancer Research Symposium; Sep 13-15, 2018; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2019;25(22 Suppl):Abstract nr GMM-021.

Tissue and host species-specific transcriptional changes in models of experimental visceral leishmaniasis.

Background: Human visceral leishmaniasis, caused by infection with Leishmania donovani or L. infantum, is a potentially fatal disease affecting 50,000-90,000 people yearly in 75 disease endemic countries, with more than 20,000 deaths reported. Experimental models of infection play a major role in understanding parasite biology, host-pathogen interaction, disease pathogenesis, and parasite transmission. In addition, they have an essential role in the identification and pre-clinical evaluation of new drugs and vaccines. However, our understanding of these models remains fragmentary. Although the immune response to Leishmania donovani infection in mice has been extensively characterized, transcriptomic analysis capturing the tissue-specific evolution of disease has yet to be reported. Methods: We provide an analysis of the transcriptome of spleen, liver and peripheral blood of BALB/c mice infected with L. donovani. Where possible, we compare our data in murine experimental visceral leishmaniasis with transcriptomic data in the public domain obtained from the study of L. donovani-infected hamsters and patients with human visceral leishmaniasis. Digitised whole slide images showing the histopathology in spleen and liver are made available via a dedicated website, www.leishpathnet.org. Results: Our analysis confirms marked tissue-specific alterations in the transcriptome of infected mice over time and identifies previously unrecognized parallels and differences between murine, hamster and human responses to infection. We show commonality of interferon-regulated genes whilst confirming a greater activation of type 2 immune pathways in infected hamsters compared to mice. Cytokine genes and genes encoding immune checkpoints were markedly tissue specific and dynamic in their expression, and pathways focused on non-immune cells reflected tissue specific immunopathology. Our data also addresses the value of measuring peripheral blood transcriptomics as a potential window into underlying systemic disease. Conclusions: Our transcriptomic data, coupled with histopathologic analysis of the tissue response, provide an additional resource to underpin future mechanistic studies and to guide clinical research.

Tissue and host species-specific transcriptional changes in models of experimental visceral leishmaniasis

Background: Human visceral leishmaniasis, caused by infection with Leishmania donovani or L. infantum, is a potentially fatal disease affecting 50,000-90,000 people yearly in 75 disease endemic countries, with more than 20,000 deaths reported. Experimental models of infection play a major role in understanding parasite biology, host-pathogen interaction, disease pathogenesis, and parasite transmission. In addition, they have an essential role in the identification and pre-clinical evaluation of new drugs and vaccines. However, our understanding of these models remains fragmentary. Although the immune response to Leishmania donovani infection in mice has been extensively characterized, transcriptomic analysis capturing the tissue-specific evolution of disease has yet to be reported. Methods: We provide an analysis of the transcriptome of spleen, liver and peripheral blood of BALB/c mice infected with L. donovani. Where possible, we compare our data in murine experimental visceral leishmaniasis with transcriptomic data in the public domain obtained from the study of L. donovani-infected hamsters and patients with human visceral leishmaniasis. Digitised whole slide images showing the histopathology in spleen and liver are made available via a dedicated website, www.leishpathnet.org. Results: Our analysis confirms marked tissue-specific alterations in the transcriptome of infected mice over time and identifies previously unrecognized parallels and differences between murine, hamster and human responses to infection. We show commonality of interferon-regulated genes whilst confirming a greater activation of type 2 immune pathways in infected hamsters compared to mice. Cytokine genes and genes encoding immune checkpoints were markedly tissue specific and dynamic in their expression, and pathways focused on non-immune cells reflected tissue specific immunopathology. Our data also addresses the value of measuring peripheral blood transcriptomics as a potential window into underlying systemic disease. Conclusions: Our transcriptomic data, coupled with histopathologic analysis of the tissue response, provide an additional resource to underpin future mechanistic studies and to guide clinical research.

Tissue and host species-specific transcriptional changes in models of experimental visceral leishmaniasis.

Background: Human visceral leishmaniasis, caused by infection with Leishmania donovani or L. infantum, is a potentially fatal disease affecting 50,000-90,000 people yearly in 75 disease endemic countries, with more than 20,000 deaths reported. Experimental models of infection play a major role in understanding parasite biology, host-pathogen interaction, disease pathogenesis, and parasite transmission. In addition, they have an essential role in the identification and pre-clinical evaluation of new drugs and vaccines. However, our understanding of these models remains fragmentary. Although the immune response to Leishmania donovani infection in mice has been extensively characterized, transcriptomic analysis capturing the tissue-specific evolution of disease has yet to be reported. Methods: We provide an analysis of the transcriptome of spleen, liver and peripheral blood of BALB/c mice infected with L. donovani. Where possible, we compare our data in murine experimental visceral leishmaniasis with transcriptomic data in the public domain obtained from the study of L. donovani-infected hamsters and patients with human visceral leishmaniasis. Digitised whole slide images showing the histopathology in spleen and liver are made available via a dedicated website, www.leishpathnet.org. Results: Our analysis confirms marked tissue-specific alterations in the transcriptome of infected mice over time and identifies previously unrecognized parallels and differences between murine, hamster and human responses to infection. We show commonality of interferon-regulated genes whilst confirming a greater activation of type 2 immune pathways in infected hamsters compared to mice. Cytokine genes and genes encoding immune checkpoints were markedly tissue specific and dynamic in their expression, and pathways focused on non-immune cells reflected tissue specific immunopathology. Our data also addresses the value of measuring peripheral blood transcriptomics as a potential window into underlying systemic disease. Conclusions: Our transcriptomic data, coupled with histopathologic analysis of the tissue response, provide an additional resource to underpin future mechanistic studies and to guide clinical research.

The Rat Gambling Task as a model for the preclinical development of treatments for gambling disorder

ABSTRACTGambling is a harmless pastime for many, but for some it can become problematic with serious social and financial consequences. To date, no pharmacological treatments for gambling disorder have been approved. Progress in this regard is undoubtedly hampered by the lack of established preclinical models that allow for the screening of the potential efficacy of new approaches. The Rat Gambling Task (rGT), based on the Iowa Gambling Task in humans, is a model of some of the decision-making processes involved in gambling. The purpose of the present review is to summarize the literature to date on the use of the rGT for preclinical testing of pharmacological agents. First, the rGT is described and compared to the IGT. Next, validity is examined to establish the rGT as a viable model for preclinical evaluation of new drugs. Finally, the available data on the effects of pharmacological challenges on the rGT are reviewed focusing on dopamine, norepinephrine, serotonin and opioid systems. It is concluded that the rGT may provide a viable preclinical model for new drug development for the treatment of gambling.

Rapid, Serial, Non-invasive Assessment of Drug Efficacy in Mice with Autoluminescent Mycobacterium ulcerans Infection

BackgroundBuruli ulcer (BU) caused by Mycobacterium ulcerans is the world's third most common mycobacterial infection. There is no vaccine against BU and surgery is needed for patients with large ulcers. Although recent experience indicates combination chemotherapy with streptomycin and rifampin improves cure rates, the utility of this regimen is limited by the 2-month duration of therapy, potential toxicity and required parenteral administration of streptomycin, and drug-drug interactions caused by rifampin. Discovery and development of drugs for BU is greatly hampered by the slow growth rate of M. ulcerans, requiring up to 3 months of incubation on solid media to produce colonies. Surrogate markers for evaluating antimicrobial activity in real-time which can be measured serially and non-invasively in infected footpads of live mice would accelerate pre-clinical evaluation of new drugs to treat BU. Previously, we developed bioluminescent M. ulcerans strains, demonstrating proof of concept for measuring luminescence as a surrogate marker for viable M. ulcerans in vitro and in vivo. However, the requirement of exogenous substrate limited the utility of such strains, especially for in vivo experiments.Methodology/Principal FindingFor this study, we engineered M. ulcerans strains that express the entire luxCDABE operon and therefore are autoluminescent due to endogenous substrate production. The selected reporter strain displayed a growth rate and virulence similar to the wild-type parent strain and enabled rapid, real-time monitoring of in vitro and in vivo drug activity, including serial, non-invasive assessments in live mice, producing results which correlated closely with colony-forming unit (CFU) counts for a panel of drugs with various mechanisms of action.Conclusions/SignificanceOur results indicate that autoluminescent reporter strains of M. ulcerans are exceptional tools for pre-clinical evaluation of new drugs to treat BU due to their potential to drastically reduce the time, effort, animals, compound, and costs required to evaluate drug activity.

A novel orally available inhibitor of focal adhesion signaling increases survival in a xenograft model of diffuse large B-cell lymphoma with central nervous system involvement

Central nervous system dissemination is a relatively uncommon but almost always fatal complication in diffuse large B-cell lymphoma patients. Optimal therapy for central nervous involvement in this malignancy has not been established. In this paper, we aimed to evaluate the therapeutic effect of E7123, a celecoxib derivative that inhibits focal adhesion signaling, in a novel xenograft model of diffuse large B-cell lymphoma with central nervous system involvement. Cells obtained after disaggregation of HT subcutaneous tumors (HT-SC cells) were intravenously injected in NOD/SCID mice. These mice received oral vehicle or 75 mg/kg of E7123 daily until they were euthanized for weight loss or signs of sickness. The antitumor effect of E7123 was validated in an independent experiment using a bioluminescent mouse model. Intravenously injected HT-SC cells showed higher take rate and higher central nervous system tropism (associated with increased expression of β1-integrin and p130Cas proteins) than HT cells. The oral administration of E7123 significantly increased survival time in 2 independent experiments using mice injected with unmodified or bioluminescent HT-SC cells. We have developed a new xenograft model of diffuse large B-cell lymphoma with central nervous system involvement that can be used in the pre-clinical evaluation of new drugs for this malignancy. E7123 is a new, well-tolerated and orally available therapeutic agent that merits further investigation since it may improve current management of diffuse large B-cell lymphoma patients with central nervous system involvement.

Airway responsiveness in an allergic rabbit model

Background Animal models of allergy and bronchial hyperresponsiveness (BHR) are useful in researching pulmonary diseases and evaluating drug effects on the airways. Neonatally immunised rabbits exhibit several features of asthma as adults, including early and late airway responses following antigen challenge, oedema and inflammatory cell infiltration into the lung, BHR to inhaled histamine and methacholine (compared with naïve rabbits) and exacerbations of BHR following antigen challenge. Therefore this model can be used to investigate the underlying mechanisms of BHR and for the preclinical evaluation of new drugs for the treatment of asthma. Aim To describe the characteristics of airway responses in a rabbit model of allergic inflammation and to evaluate the relationship between skin test reactivity to antigen, airway inflammation and BHR. Methods New Zealand White rabbits were neonatally immunised against Alternaria tenius. At 3 months of age, airway responsiveness was measured to aerosolised histamine, methacholine or allergen. Bronchoalveolar lavage (BAL) was performed and cell counts recorded. Direct skin tests were performed to assess skin reactivity to allergen and passive cutaneous anaphylaxis (PCA) tests were performed to determine titres of circulating IgE. Results In a population of allergic rabbits, allergen challenge induced a significant bronchoconstriction, airway inflammation and BHR. Skin test responsiveness to allergen did not correlate with various indices of pulmonary mechanics e.g. baseline sensitivity to methacholine and histamine, or allergen-induced BHR. In contrast, skin test responsiveness did predict airway inflammation as assessed by measurements of eosinophil recruitment to the lung. Conclusion The allergic rabbit is a useful model to further our understanding of allergic diseases. Recording lung function using a minimally invasive procedure allows repeated measurements to be made in rabbits longitudinally, and each animal may thus be used as its own control. Our observations do not support the use of skin responsiveness to allergen as a predictor of airway sensitivity as we observed no correlation between skin sensitivity and airway responsiveness to inhaled histamine, methacholine or allergen. However, skin reactivity did predict airway inflammation as assessed by measurements of eosinophil recruitment to the lung. Our results also further highlight the likely dissociation between airway inflammation and BHR.

Prediction of drug-induced cardiotoxicity using human embryonic stem cell-derived cardiomyocytes

Recent withdrawals of prescription drugs from clinical use because of unexpected side effects on the heart have highlighted the need for more reliable cardiac safety pharmacology assays. Block of the human Ether-a-go go Related Gene (hERG) ion channel in particular is associated with life-threatening arrhythmias, such as Torsade de Pointes (TdP). Here we investigated human cardiomyocytes derived from pluripotent (embryonic) stem cells (hESC) as a renewable, scalable, and reproducible system on which to base cardiac safety pharmacology assays. Analyses of extracellular field potentials in hESC-derived cardiomyocytes (hESC-CM) and generation of derivative field potential duration (FPD) values showed dose-dependent responses for 12 cardiac and noncardiac drugs. Serum levels in patients of drugs with known effects on QT interval overlapped with prolonged FPD values derived from hESC-CM, as predicted. We thus propose hESC-CM FPD prolongation as a safety criterion for preclinical evaluation of new drugs in development. This is the first study in which dose responses of such a wide range of compounds on hESC-CM have been generated and shown to be predictive of clinical effects. We propose that assays based on hESC-CM could complement or potentially replace some of the preclinical cardiac toxicity screening tests currently used for lead optimization and further development of new drugs.

Cell-based biosensors: current trends of the development.

In the last decade, a number of laboratories have developed devices that combine electronic components with living cells, including neurons. These devices can be used as cell-based biosensors or labs-on-a-chip for testing of the tumor cell sensitivity to anti-cancer drugs, detection of toxins and chemical substances and pre-clinical evaluation of new drugs. Here we review briefly the existing types of the cell-based biosensors and the strategies employed to improve these complex devices. We argue that, for the neuron-based biosensors, introduction of structure in the connections of the synaptic network should significantly improve the utility of such devices.

Hemodynamic response of a canine model of chronic heart failure to intravenous dobutamine, nitroprusside, enalaprilat, and digoxin.

The hemodynamic effects of acute intravenous administration of nitroprusside, dobutamine, enalaprilat, and digoxin was investigated in a canine model of chronic heart failure (CHF) produced by multiple sequential intracoronary microembolizations. Dobutamine (4 micrograms/kg/min) increased cardiac output (2.4 +/- 0.1 vs. 4.0 +/- 0.4 l/min; p < .001) and LV ejection fraction (LVEF; 26 +/- 1 vs. 30 +/- 4%; p < .01), and decreased systemic vascular resistance (SVR; 3620 +/- 170 vs. 2470 +/- 190 dynes sec cm-5; p < .001). Nitroprusside (3 micrograms/kg/min) acted as a venodilator; it decreased pulmonary artery wedge pressure (16 +/- 1 vs. 13 +/- 1 mmHg; p < .01) and SVR (3730 +/- 440 vs. 3210 +/- 280 dynes sec cm-5; NS) but had no effect on cardiac output. Enalaprilat (1.875 mg) produced a significant increase of cardiac output (3.0 +/- 0.5 vs. 3.8 +/- 0.5 l/min; p < .001) and LVEF (22 +/- 1 vs. 30 +/- 1%; p < .01), and decreased SVR (3280 +/- 400 vs. 2450 +/- 250 dynes sec cm-5; p < .01). Intravenous digoxin at a cumulative dose of 0.75 mg increased LVEF (23 +/- 2 vs. 31 +/- 2%; p < .01) but had no effect on SVR. These data indicate that this canine model of CHF responds to acute pharmacologic intervention in a manner comparable to that seen in patients with CHF. Accordingly, this model may be a useful tool for the preclinical evaluation of new drugs targeted toward the treatment of CHF and for investigating the mechanisms of action of drugs currently used for the treatment of this disease state.

Chemosensitivity profiles of human cancers assessed by the 6-day SRC assay on serially xenografted tumors.

To assess the potential value of the 6-day subrenal capsule (SRC) assay in preclinical evaluation of new drugs using serially xenografted human tumors as source of tumor tissue, we studied the response of 31 human tumor lines (8 malignant melanomas, 12 sarcomas, 9 lung carcinomas and 2 colon carcinomas) to relevant standard drugs and to a new imidazotetrazine, Mitozolomide. Mitozolomide was found to be the most active drug tested in 50% of the lung carcinomas and as active as CCNU in melanomas. The activity of the standard anticancer drugs against subrenal grafts closely resembled the patterns seen with the same tumors in the clinic. In further attempts to validate the procedure, sensitivity profiles of some tumors were concurrently determined in the subcutaneous (s.c.) nude mouse model. In 11 out of the 12 tumors, the two assays selected the same drug as being the most active and in most of these tumors the two procedures gave the same ranking for the different drugs. Also, when the relative sensitivities of a series of melanoma xenografts to each of two drugs (DTIC and CCNU) were tested, the two assays gave the same ranking of the xenografts for each drug. The concordance between the two assays and the fact that the s.c. nude mouse assay reflects the chemosensitivity of the parent tumor in patients, suggest that the application of the 6-day SRC assay to xenografted tumors is a valid and useful procedure permitting rapid preclinical evaluation of new drugs to be carried out at relatively low cost.