Publications

We have found in our previous studies that some pyrimidine and purine derivatives of 4, 5-didehydro-5, 6-dideoxy-L-ascorbic acid possess pronounced cytostatic activities against some malignant human tumor cell lines [1]. In this connection we have synthesized a series of novel C-5 pyrimidine derivatives of 2, 3-di-O-benzyl-4, 5-didehydro-5, 6-dideoxy-L-ascorbic acid (Figure) by Stille reaction of the 5-iodouracil derivative of L-ascorbic acid with unsaturated stannanes. The novel compunds were evaluated for their cytostatic activities against malignant human tumor cell lines: pancreatic carcinoma, cervical carcinoma, breast carcinoma, laryngeal carcinoma, colon carcinoma, human T-lymphocytes, as well as human fibroblast cells. Inhibitory activity evaluations of those compounds against herpes simplex virus type 1 and 2, vaccinia virus, variccela-zoster virus, vesicular stomatitis virus, Coxsackie virus B4, respiratory syncytial virus, parainfluenza virus, reovirus-1, sindbis virus and Punta Toro virus were also performed. The results of antitumoral and antiviral evaluations will be presented. [1] (a) T. Gazivoda et al, Carbohydrate Res. 2006 (341) 433 ; (b) T. Gazivoda et al, Bioorg. Med. Chem. 2005 (13) 131 ; (c) S. Raic-Malic et al, J. Med. Chem. 2000 (43) 4806 ; (d) S. Raic-Malic et al, J. Med. Chem. 1999 (42) 2673.

During the last forty years we have witnessed impressive advances in the field of antiviral drug discovery culminating with the introduction of therapies able to stop human immunodeficiency virus (HIV) replication, or cure hepatitis C virus infections in people suffering from liver disease. However, there are important viral diseases without effective treatments, and the emergence of drug resistance threatens the efficacy of successful therapies used today. In this review, we discuss strategies to discover antiviral compounds specifically designed to combat drug resistance. Currently, efforts in this field are focused on targeted proteins (e.g. multi-target drug design strategies), but also on drug conformation (either improving drug positioning in the binding pocket or introducing conformational constraints), in the introduction or exploitation of new binding sites, or in strengthening interaction forces through the introduction of multiple hydrogen bonds, covalent binding, halogen bonds, additional van der Waals forces or multivalent binding. Among the new developments, proteolysis targeting chimeras (PROTACs) have emerged as a valid approach taking advantage of intracellular mechanisms involving protein degradation by the ubiquitin-proteasome system. Finally, several molecules targeting host factors (e.g. human dihydroorotate dehydrogenase and DEAD-box polypeptide 3) have been identified as broad-spectrum antiviral compounds. Implementation of herein described medicinal chemistry strategies are expected to contribute to the discovery of new drugs effective against current and future threats due to emerging and re-emerging viral pandemics.

We present a fast, convenient and inexpensive method that allows the automated, large-scale screening of chemical libraries for compounds that are converted by the herpes simplex virus type 1 (HSV-1) thymidine kinase (TK) into inhibitors of cell growth. The method is based on the use of budding yeast (Saccharomyces cerevisiae) transformed with the HSV-1 TK gene on a multicopy plasmid. Eight nucleoside analogs (acyclovir, ganciclovir, penciclovir, lobucavir, brivudin, sorivudine, IVDU and ara-T), for which the cytostatic action against mammalian cells expressing the HSV-1 TK gene has been well documented, were studied for their inhibitory effect on the growth of yeast expressing the viral TK. These nucleoside analogs had little or no inhibitory effect on the growth of yeasts transformed with the empty vector, but inhibited to a significant extent the growth of yeast expressing the viral TK. Use of HSV-1 TK-expressing yeast allows quick screening in multi-well plate format for compounds with potential use in HSV-1 TK suicide gene therapy. The method may also be used as a tool to selectively suppress or arrest the growth of one population of yeast out of mixed yeast cell cultures.

Expression of IN in CEM cells inhibits HIV-1 replication by a cumulative inhibitory effect on integration and particle production, in accord with the known pleiotropic interactions of IN. The inhibition of HIV-1 replication in CEM cells expressing the N-terminal domain of IN may lead to a novel approach for the gene therapy of AIDS.

The introduction of potent combinations of antiviral drugs is a major breakthrough in the treatment of HIV. We investigated the long-term virologic outcome and the development of resistance after initiating highly active antiretroviral therapy (HAART) in drug-naive patients in daily clinical practice. Twenty-five treatment-naive HIV-1 patients were started on HAART. Fifteen patients responded with a drop in viral load below the limit of detection during 35.5 (interquartile range: 7) months of therapy. In 6 of 10 patients with virologic failure, virus with resistance-related mutations against the received drugs emerged. Compared with responders (R), nonresponding (NR) patients were in a later disease stage at therapy start (p = 0.0089) with lower CD4 cell counts at baseline (p = 0.040), and a lower proportion of nonresponders showed protease inhibitor (PI) levels above C(min) (p = 0.049). More NR patients showed secondary PI mutations at baseline (p = 0.079), and the CCR2-64I coreceptor polymorphism was absent among NR patients, compared with 38.5% of R patients displaying CCR2-64I (p = 0.053), although the differences were not significant. In conclusion, starting HAART in antiretroviral drug-naive HIV-infected patients followed in daily clinical practice prevented viral breakthrough for up to 44 months in 60% of the patients. Virologic failure was associated with the development of resistance-related mutations, a later stage of disease at start of therapy and lower PI drug levels.

Industrial X-ray CT systems are increasingly used as dimensional measuring machines.However, micron level accuracy is not always achievable yet.The measurement accuracy is influenced by many factors, such as workpiece properties, X-ray voltage, filter, beam hardening, scattering and calibration methods [1-4].Since most of these factors are mutually correlated, it remains challenging to interpret measurement results and to identify the distinct error sources.Since simulations allow isolating the different affecting factors, they form a useful complement to experimental investigations.Dewulf et.al [5] investigated the influence of beam hardening correction parameters on the diameter of a calibrated steel pin in different experimental set-ups.It was clearly shown that inappropriate beam hardening correction can result in significant dimensional errors.This paper confirms these results using simulations of a pin surrounded by a stepped cylinder: a clear discontinuity in the measured diameter of the inner pin is observed where it enters the surrounding material.The results are expanded with an investigation of the beam hardening effect on the measurement results for both inner and outer diameters of the surrounding stepped cylinder.Accuracy as well as the effect on the uncertainty determination are discussed.The results are compared with simulations using monochromatic beams in order to have a benchmark which excludes beam-hardening effects and X-ray scattering.Furthermore, based on the above results, the authors propose a case-dependent calibration artefact for beam hardening correction and edge offset determination.In the final part of the paper, the investigations are expanded with experiments of a new set-up that includes non-cylindrical features; the effectiveness of the proposed calibration artefact is also studied.