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Biomedical subjects

László Orfi

Publications and source records attributed to László Orfi.

15 recordsLinked to original sources
PubMed2006

Comparison of the cytotoxic effects of receptor tyrosine kinase inhibitors on macrophage functions; possible side effects in the immune defense.

Certain receptor tyrosine kinase (RTK) inhibitors reduced the phagocytic capacity of rat macrophages, without influencing the binding of bacteria to macrophage surface. The NO production of elicited rat macrophages was also decreased due to the inhibition of the expression of NOS II. The most potent inhibitory compound was PD166326 (6-(2,6-dichloro-phenyl)-2-(4-hydroxy-phenylamino)-8-methyl-8H-pyrido[2,3-d]pyrimidin-7-one) belonging to a family of RTK inhibitors of broad spectra. These impairing effects could be explained by the apoptosis inducing property of the inhibitor, evidenced by the destroyed mitochondrial membrane potential. The MTT cell viability test indicated a slight, but significant injury of macrophages. In addition to this compound, two other tested RTK inhibitors caused less marked impairment of macrophage functions, while four compounds were not efficient on macrophages at all. Nevertheless, these damaging effects of the inhibitors did not reduce the anti-tumor effect of the RTK inhibitors on COS 7 cells as evidenced by MTT test and apoptosis study. However, these side effects may be important when RTK inhibitors are selected against tumor growth, indicating that certain inhibitors may impair the immune defense during therapeutical application.

Animals↗
PubMed2005

Proteomic characterization of the angiogenesis inhibitor SU6668 reveals multiple impacts on cellular kinase signaling.

Knowledge about molecular drug action is critical for the development of protein kinase inhibitors for cancer therapy. Here, we establish a chemical proteomic approach to profile the anticancer drug SU6668, which was originally designed as a selective inhibitor of receptor tyrosine kinases involved in tumor vascularization. By employing immobilized SU6668 for the affinity capture of cellular drug targets in combination with mass spectrometry, we identified previously unknown targets of SU6668 including Aurora kinases and TANK-binding kinase 1. Importantly, a cell cycle block induced by SU6668 could be attributed to inhibition of Aurora kinase activity. Moreover, SU6668 potently suppressed antiviral and inflammatory responses by interfering with TANK-binding kinase 1-mediated signal transmission. These results show the potential of chemical proteomics to provide rationales for the development of potent kinase inhibitors, which combine rather unexpected biological modes of action by simultaneously targeting defined sets of both serine/threonine and tyrosine kinases involved in cancer progression.

Angiogenesis Inhibitors↗
PubMed2005

Synthesis of selective SRPK-1 inhibitors: novel tricyclic quinoxaline derivatives.

SR protein-specific kinase-1 (SRPK-1) has been identified as a validated target for hepatitis B virus (HBV). A series of novel tricyclic quinoxaline derivatives was designed and synthesised as potential kinase inhibitory antiviral agents and was found to be active and selective for SRPK-1 kinase. Most of these novel compounds have drug-like properties according to experimentally determined LogP and LogS values.

Antiviral Agents↗
PubMed2005

Acid-base profiling of imatinib (gleevec) and its fragments.

The site-specific basicities of imatinib (Gleevec, a new signal transduction inhibitor drug of chronic myeloid leukemia) and two of its fragment compounds were quantitated in terms of protonation macroconstants, microconstants, and group constants by NMR-pH and pH-potentiometric titrations. Sequential protonation of imatinib follows the N(34), N(11), N(31), N(13) order, in which N(11) and N(31) show commensurable basicity, but negligible intramolecular interaction. Fragment compounds include two "halves" of imatinib, and their moiety-specific basicities confirm the NMR-based protonation sequence of the parent compound. NMR-pH profiles, macro- and/or microscopic protonation schemes, and species-specific distribution diagrams are presented. On the basis of these data, imatinib is shown to be predominantly neutral, monocationic, and tricationic at intestinal, blood, and gastric pH, respectively. The molecular hypotheses on imatinib binding to the Bcr-Abl oncogene fusion protein are interpreted at the site-specific level in view of the moiety basicities of imatinib.

Antineoplastic Agents↗
PubMed2005

TT232, a novel signal transduction inhibitory compound in the therapy of cancer and inflammatory diseases.

TT-232 is a structural analogue of somatostatin exhibiting strong and selective growth-inhibitory effects, inhibition of neurogenic inflammation, as well as general anti-inflammatory and analgesic potential without the wide-ranging endocrine side effects of the parent hormone and its "traditional" analogues. The anti-inflammatory action of TT-232 is mediated through the SSTR4 receptor, and its antitumor activity is mediated through the SSTR1 receptor and by the tumor-specific isoform of pyruvate kinase. Its mechanism of action is in line with a new era of molecular medicine called signal transduction therapy, where "false" intracellular or intercellular communication is inhibited or corrected without interfering with basic cell functions and machinery. TT232 has passed phase I clinical trials without toxicity and significant side effects, and phase II studies are running for oncological and anti-inflammatory indications, respectively. This compound has the perspective to become the first drug in molecularly targeted therapy of inflammation where a combined effect of anti-inflammatory, analgesic, and neurogenic inflammation-inhibiting activity can be achieved.

Amino Acid Sequence↗
PubMed2005

Drug discovery in the kinase inhibitory field using the Nested Chemical Library technology.

Kinase inhibitors are at the forefront of modern drug research, where mostly three technologies are used for hit-and-lead finding: high throughput screening of random libraries, three-dimensional structure-based drug design based on X-ray data, and focused libraries around limited number of new cores. Our novel Nested Chemical Library (NCL) (Vichem Chemie Research Ltd., Budapest, Hungary) technology is based on a knowledge base approach, where focused libraries around selected cores are used to generate pharmacophore models. NCL was designed on the platform of a diverse kinase inhibitory library organized around 97 core structures. We have established a unique, proprietary kinase inhibitory chemistry around these core structures with small focused sublibraries around each core. All the compounds in our NCL library are stored in a big unified Structured Query Language database along with their measured and calculated physicochemical and ADME/toxicity (ADMET) properties, together with thousands of molecular descriptors calculated for each compound. Biochemical kinase inhibitory assays on selected, cloned kinase enzymes for a few hundred NCL compound sets can provide sufficient biological data for rational computerized design of new analogues, based on our pharmacophore model-generating 3DNET4W QSPAR (quantitative structure-property/activity relationships) approach. Using this pharmacophore modeling approach and the ADMET filters, we can preselect synthesizable compounds for hit-and-lead optimization. Starting from this point and integrating the information from QSPAR, high-quality leads can be generated within a small number of optimization cycles. Applying NCL technology we have developed lead compounds for several validated kinase targets.

Algorithms↗
PubMed2004

Characterization of a conserved structural determinant controlling protein kinase sensitivity to selective inhibitors.

Some protein kinases are known to acquire resistance to selective small molecule inhibitors upon mutation of a conserved threonine at the ATP binding site to a larger residue. Here, we performed a comprehensive mutational analysis of this structural element and determined the cellular sensitivities of several disease-relevant tyrosine kinases against various inhibitors. Mutant kinases possessing a larger side chain at the critical site showed resistance to most compounds tested, such as ZD1839, PP1, AG1296, STI571, and a pyrido[2,3-d]pyrimidine inhibitor. In contrast, indolinones affected both wild-type and mutant kinases with similar potencies. Resistant mutants were established for pharmacological analysis of betaPDGF receptor-mediated signaling and allowed the generation of a drug-inducible system of cellular Src kinase activity. Our data establish a conserved structural determinant of protein kinase sensitivity relevant for both signal transduction research and drug development.

Amino Acid Sequence↗
PubMed2004

High-affinity interaction of tyrosine kinase inhibitors with the ABCG2 multidrug transporter.

Tyrosine kinase inhibitors (TKIs) are promising new agents for specific inhibition of malignant cell growth and metastasis formation. Because most of the TKIs have to reach an intracellular target, specific membrane transporters may significantly modulate their effectiveness. In addition, the hydrophobic TKIs may interact with so-called multidrug transporters and thus alter the cellular distribution of unrelated pharmacological agents. In the present work, we show that certain TKIs, already in the clinical phase of drug development, directly interact with the ABCG2 multidrug transporter protein with a high affinity. We found that in several in vitro assay systems, STI-571 (Gleevec; imatinib mesylate), ZD1839 (Iressa; gefitinib), and N-[4-[(3-bromophenyl)amino]-6-quinazolinyl]-2-butynamide (EKI-785) interacted with ABCG2 at submicromolar concentrations, whereas other multidrug transporters, human multidrug resistance protein (P-glycoprotein, ABCB1) and human multidrug resistance protein 1 (ABCC1), showed much lower reactivity toward these agents. Low concentrations of the TKIs examined selectively modulated ABCG2-ATPase activity, inhibited ABCG2-dependent active drug extrusion, and significantly affected drug resistance patterns in cells expressing ABCG2. Our results indicate that multidrug resistance protein modulation by TKIs may be an important factor in the clinical treatment of cancer patients. These data also raise the possibility that an extrusion of TKIs by multidrug transporters, e.g., ABCG2, may be involved in tumor cell TKI resistance.

Adenosine Triphosphatases↗
PubMed2004

Improved, high yield synthesis of 3H-quinazolin-4-ones, the key intermediates of recently developed drugs.

Purine bases and their bioisosteric analogs are widely used as building blocks in combinatorial chemistry. Recently a great number of fused pyrimidine derivatives became known as potential drug molecules against various types of proliferative diseases, caused by over-expression of protein kinases. One of the most important compound families are quinazolines : e.g. the best inhibitor of EGFR tyrosine kinase is PD153035 (6,7-dimethoxy-4-(3'-bromophenyl)amino-quinazoline) and IRESSA (gefitinib, ZD1839), developed from this compound family, is presently the only one approved and granted drug by the FDA for the treatment of advanced non-small-cell lung cancer (NSCLC). KF31327 (3-ethyl-8-[2-(4-hydroxymethylpiperidino)benzylamino]-2,3-dihydro-1H-imidazo[4,5-g]-quinazoline-2-thione dihydrochloride) from this group, showed significantly higher inhibitory activity on cyclic GMP-specific phosphodiesterase compared with those of sildenafil (Viagra). The synthetic procedures of the example compounds are based on imidoyl chloride intermediates that were prepared from the appropriate 3H-quinazoline-4-ones. Although the key intermediates, quinazoline-4-ones, have been known since more than hundred years, their synthetic procedures have been improved much only in the past ten years. In this paper we reviewed the efficient synthetic methods of quinazolin-4-ones, and presented a novel, reliable method for their synthesis. There was no considerable effect of microwave-, or traditional thermal activation on the yield and compound purity.

Drugs, Investigational↗
PubMed2004

Comparison of predictive ability of water solubility QSPR models generated by MLR, PLS and ANN methods.

ADME/Tox computational screening is one of the most hot topics of modern drug research. About one half of the potential drug candidates fail because of poor ADME/Tox properties. Since the experimental determination of water solubility is time-consuming also, reliable computational predictions are needed for the pre-selection of acceptable "drug-like" compounds from diverse combinatorial libraries. Recently many successful attempts were made for predicting water solubility of compounds. A comprehensive review of previously developed water solubility calculation methods is presented here, followed by the description of the solubility prediction method designed and used in our laboratory. We have selected carefully 1381 compounds from scientific publications in a unified database and used this dataset in the calculations. The externally validated models were based on calculated descriptors only. The aim of model optimization was to improve repeated evaluations statistics of the predictions and effective descriptor scoring functions were used to facilitate quick generation of multiple linear regression analysis (MLR), partial least squares method (PLS) and artificial neural network (ANN) models with optimal predicting ability. Standard error of prediction of the best model generated with ANN (with 39-7-1 network structure) was 0.72 in logS units while the cross validated squared correlation coefficient (Q(2)) was better than 0.85. These values give a good chance for successful pre-selection of screening compounds from virtual libraries, based on the predicted water solubility.

Chemical Phenomena↗
PubMed2003

Validation subset selections for extrapolation oriented QSPAR models.

One of the most important features of QSPAR models is their predictive ability. The predictive ability of QSPAR models should be checked by external validation. In this work we examined three different types of external validation set selection methods for their usefulness in in-silico screening. The usefulness of the selection methods was studied in such a way that: 1) We generated thousands of QSPR models and stored them in 'model banks'. 2) We selected a final top model from the model banks based on three different validation set selection methods. 3) We predicted large data sets, which we called 'chemical universe sets', and calculated the corresponding SEPs. The models were generated from small fractions of the available water solubility data during a GA Variable Subset Selection procedure. The external validation sets were constructed by random selections, uniformly distributed selections or by perimeter-oriented selections. We found that the best performing models on the perimeter-oriented external validation sets usually gave the best validation results when the remaining part of the available data was overwhelmingly large, i.e., when the model had to make a lot of extrapolations. We also compared the top final models obtained from external validation set selection methods in three independent and different sizes of 'chemical universe sets'.

Computer Simulation↗
PubMed2002

Evaluation of lipophilicity and antitumour activity of parallel carboxamide libraries.

Searching for molecules possessing antitumour activity, a parallel molecule library of aromatic carboxamides has been designed and synthesised. This work resulted in a "thiophene" sub-library containing a thiophene core and of a "furoyl" sub-library with a furoyl core, respectively. In both sub-libraries substitutions were carried out with six different groups resulting in six pairs of compounds differing in only the heteroatom of aromatic ring of the cores. To study the importance of the type of cores and the specific substitutions in relation to their lipophilicity and antitumour activity, lipophilicity of carboxamides was determined by chromatographical data (log k') and by software calculated parameters (CLOGP). Pairs of compounds were tested for their ability to inhibit the proliferation of the A431 cells by MTT assay. The isosteric molecule pairs were successfully separated. Our results showed that the experimentally determined (log k') and the calculated (CLOGP) lipophilicity parameters correlated well with each other. Furthermore, lipophilicity values of the thiophene sub-library were always higher than those in the furoyl sub-library. Moreover, compounds of the thiophene sub-library were more active than their respective furoyl pairs in our MTT antiproliferative assay. From these observations we can conclude that the higher the lipophilicity values the higher the antitumour activity of the carboxamides synthesised. Therefore, determination of lipophilicity by measuring the log k' or by calculating the CLOGP values of the carboxamide sub-libraries may help to predict their biological activities.

Amides↗
PubMed2002

Interaction of tyrosine kinase inhibitors with the human multidrug transporter proteins, MDR1 and MRP1.

Specific tyrosine kinase inhibitors (TKIs) are rapidly developing clinical tools applied for the inhibition of malignant cell growth and metastasis formation. Most of these newly developed TKI molecules are hydrophobic, thus rapidly penetrate the cell membranes to reach intracellular targets. However, a large number of tumor cells overexpress multidrug transporter membrane proteins, which efficiently extrude hydrophobic drugs and thus may prevent the therapeutic action of TKIs. In the present work, we demonstrate that the most abundant and effective cancer multidrug transporters, MDR1 and MRP1, directly interact with several TKIs under drug development or already in clinical trials. This interaction with the transporters does not directly correlate with the hydrophobicity or molecular structure of TKIs, and shows a large variability in transporter selectivity and affinity. We suggest that performing enzyme- and cell-based multidrug transporter interaction tests for TKIs may greatly facilitate drug development, and allow the prediction of clinical TKI resistance based on this mechanism. Moreover, diagnostics for the expression of specific multidrug transporters in the malignant cells, combined with information on the interactions of the drug transporter proteins with TKIs, should allow a highly effective, individualized clinical treatment for cancer patients.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2002

Relationship between lipophilicity and antitumor activity of molecule library of Mannich ketones determined by high-performance liquid chromatography, clogP calculation and cytotoxicity test.

A series of Mannich ketones were synthesized in order to study the relative importance of structure and specific substitutions in relation to their lipophilicity and antitumor activity. Substitutions were carried out with morpholinyl, pirrolidinyl, piperidyl and tetrahydro-isoquinolyl groups in various positions on three different skeletons. Lipophilicity of Mannich ketones was characterised by chromatography data (log k') and by software calculated parameters (clogP). Compounds were tested on their ability to inhibit the proliferation of the A431 human adenocarcinoma cell line evaluated by MTT and apoptosis assays. The results suggest that the higher the lipophilicity values (log k' and clogP), the higher the antitumor and apoptotic activity of Mannich ketones. Determination of lipophilicity by measuring the log k' or by calculating the clogP values of the compounds may help to predict their biological activities.

Antineoplastic Agents↗