Biomedical subjects

Andreas Billich

Publications and source records attributed to Andreas Billich.

36 records · Page 2Linked to original sources

PubMed2004

Fluorescence-based assay of sphingosine kinases.

Sphingosine kinase enzymatic activity is commonly measured using radiolabeled substrates, with thin-layer chromatography and/or solvent extraction needed to detect the reaction product sphingosine-1-phosphate. We developed a fluorescence-based assay, using a sphingosine derivative labeled with a 7-nitrobenz-2-oxa-1,3-diazole moiety (15-NBD-Sph). Separation of substrate (15-NBD-Sph) from product (the corresponding phosphate) is achieved by extraction with chloroform/methanol at pH 8.5. The phosphate derivative is recovered by >98% in the aqueous phase and is directly detected and quantified by its fluorescence. 15-NBD-Sph is readily phosphorylated by human and murine sphingosine kinases 1 and 2. The suitability of the assay for measuring the activity of the kinases, both in the purified state and when contained in lysates of mammalian cells, was demonstrated. The present method is a convenient alternative to the radiometric assays and is particularly suited to the search for inhibitors of sphingosine kinases.

Animals↗

PubMed2004

Percutaneous absorption of drugs used in atopic eczema: pimecrolimus permeates less through skin than corticosteroids and tacrolimus.

For treatment of skin diseases with topical drugs, penetration of the agents into the relevant layers of the skin is required. Permeation through the skin should, however, be kept to a minimum, in order to avoid the risk of systemic side effects. Here we compared the in vitro skin penetration and permeation of two novel drugs used in the therapy of atopic eczema (pimecrolimus and tacrolimus) and three representative corticosteroids (betamethasone-17-valerate, clobetasol-17-propionate, and diflucortolon-21-valerate). Drug concentrations of pimecrolimus and corticosteroids in human skin were found to be in the same order of magnitude. Permeation of pimecrolimus through human skin was, however, lower by factors of 70-110 as compared to the steroids. When pimecrolimus was compared with tacrolimus in human, pig, or rat skin, similar concentrations of the two compounds were measured in the skin, whereas permeation of pimecrolimus through skin was consistently lower by factors of 9-10. Lipophilicity was found to be highest for pimecrolimus, its octanol-water distribution coefficient being higher by factors of 8 and 25-450 than that of tacrolimus and the corticosteroids, respectively. The low permeation of pimecrolimus may be explained by its higher lipophilicity (compared to tacrolimus and the corticosteroids) and higher molecular weight (compared to steroids). In conclusion, pimecrolimus appears to have a favourable skin penetration/permeation profile, featuring a low degree of percutaneous absorption.

Administration, Cutaneous↗

PubMed2004

Steroid sulfatase inhibitors.

Steroid sulfatase (STS) regulates the local production of estrogens and androgens from systemic precursors in several tissues. The enzyme catalyzes the hydrolysis of the sulfate esters of 3-hydroxy steroids, which are inactive transport or precursor forms of the active 3-hydroxy steroids. STS inhibitors are expected to block the local production and, consequently, to reduce the local levels of the hormones. Therefore, they are considered as potential new therapeutic agents for the treatment of estrogen- and androgen-dependent disorders. Indications range from cancers of the breast, endometrium and prostate to androgenetic alopecia and acne. In this review, we give a comprehensive summary of the current knowledge and problems in the field of medicinal chemistry of STS inhibitors. The various types of inhibitors are presented and their structure-activity relationships are discussed. In addition to potent arylsulfamate-based, irreversible inhibitors, novel types of reversible inhibitors were recently discovered. The recent publication of the X-ray structure of STS will further boost research activities on this attractive target.

Binding Sites↗

PubMed2004

6-[2-(adamantylidene)-hydroxybenzoxazole]-O-sulfamate, a steroid sulfatase inhibitor for the treatment of androgen- and estrogen-dependent diseases.

Steroid sulfatase (STS) offers a new target for the treatment of steroid hormone-dependent diseases, such as breast and prostate cancer and androgen-dependent skin diseases. We here characterize a novel non-estrogenic inhibitor of the enzyme, namely 6-[2-(adamantylidene)-hydroxybenzoxazole]-O-sulfamate (AHBS), with special attention to its potential use in the treatment of acne. The compound blocks STS activity in homogenates of human skin with IC(50)=16 nM. Following a single oral dose (5 mg/kg) in rats, the compound blocks STS in the skin by 95% at 8 h, followed by recovery of activity over 5 days. Following topical application to the skin, both in vitro and in vivo, AHBS passes through the stratum corneum leading to inhibition of STS activity in the dermal compartment with rapid onset and long duration. Topical application of AHBS to Göttingen minipigs for a period of 2 weeks does not induce symptoms of ichthyosis as seen in STS-deficient human subjects, but leads to a reduction of sebum secretion to the skin surface. Based on these data, clinical studies with AHBS in acne patients are warranted, in order to verify the hypothesis on the importance of the sulfatase pathway in androgen-dependent skin diseases.

Absorption↗

PubMed2004

Confocal fluorescence detection expanded to UV excitation: the first continuous fluorimetric assay of human steroid sulfatase in nanoliter volume.

Steroid sulfatase is an enzyme that currently enjoys considerable interest as a potential drug target in the treatment of estrogen- and androgen-dependent diseases, in particular breast cancer. We have purified human steroid sulfatase to apparent homogeneity from recombinant Chinese hamster ovary cells, and we established an assay with a new fluorogenic substrate, 3,4-benzocoumarin-7-O-sulfate (1). Substrate 1 features a K(m) value of 22.5 microM, which is close to the value for the natural substrate dehydroepiandrosterone sulfate (26 microM) and much lower than the K(m) values of other synthetic substrates (276-736 microM). Importantly, the cleavage of substrate 1 can be monitored continuously during the enzymatic cleavage, since a change in fluorescence intensity is detectable at the pH where the enzyme is active; in contrast, all other synthetic substrates described so far require alkalization to reveal a measurable absorbance or fluorescence signal. The adaptation of the assay to the 96-well format allows continuous monitoring of multiple wells in a microplate fluorescence reader. Applications of the assay for the determination of IC(50) and K(i) values of novel steroid sulfatase inhibitors are presented. Most importantly the assay was transferred to the nanoscale format (1-microl assay volume) in 2080-well plates with confocal fluorescence detection. This miniaturization will permit screening with a minimum throughput of 20000 compounds per day. The system presented demonstrates that the confocal detection platform used for nanoscreening can be successfully adapted to assays for which conventional ultraviolet dyes like coumarins are necessary. This strongly broadens the application range of confocal readers in drug screening.

Algorithms↗

PubMed2004

Early activation of sphingosine kinase in mast cells and recruitment to FcepsilonRI are mediated by its interaction with Lyn kinase.

Sphingosine kinase has been recognized as an essential signaling molecule that mediates the intracellular conversion of sphingosine to sphingosine-1-phosphate. In mast cells, induction of sphingosine kinase and generation of sphingosine-1-phosphate have been linked to the initial rise in Ca(2+), released from internal stores, and to degranulation. These events either precede or are concomitant with the activation of phospholipase C-gamma and the generation of inositol trisphosphate. Here we show that sphingosine kinase type 1 (SPHK1) interacts directly with the tyrosine kinase Lyn and that this interaction leads to the recruitment of this lipid kinase to the high-affinity receptor for immunoglobulin E (FcepsilonRI). The interaction of SPHK1 with Lyn caused enhanced lipid and tyrosine kinase activity. After FcepsilonRI triggering, enhanced sphingosine kinase activity was associated with FcepsilonRI in sphingolipid-enriched rafts of mast cells. Bone marrow-derived mast cells from Lyn(-/)(-) mice, compared to syngeneic wild-type cells, were defective in the initial induction of SPHK1 activity, and the defect was overcome by retroviral Lyn expression. These findings position the activation of SPHK1 as an FcepsilonRI proximal event.

Animals↗

PubMed2004

AIDSVAX VaxGen.

AIDSVAX, a bivalent vaccine consisting of a preparation of recombinant gp120 from two types of HIV, is being developed by VaxGen for the potential prevention of HIV infection. Two versions of the vaccine are in phase III trials: AIDSVAX B/E, in trials in Thailand, stimulates production of antibody to HIV subtypes common to South Asia, South East Asia and countries of the Pacific Rim; and AIDSVAX B/B, in trials in the US and Europe, stimulates the production of antibody to HIV subtypes that are found in the Americas, Europe, the Caribbean and Australia.

AIDS Vaccines↗

PubMed2003

6-(2-adamantan-2-ylidene-hydroxybenzoxazole)-O-sulfamate: a potent non-steroidal irreversible inhibitor of human steroid sulfatase.

We report the synthesis and results from the in vitro evaluation of 6-(adamantan-2-ylidene-hydroxybenzoxazole)-O-sulfamate 1 as an irreversible inhibitor of human steroid sulfatase (STS). Highly straightforward, condensation of 2-methyl-6-hydroxybenzoxazole with 2-adamantanone, subsequent elimination of water and sulfamoylation provide the title compound in 45% overall yield from the inexpensive 2,4-dihydroxyacetophenone. 1 was found to be a potent irreversible inhibitor of purified human steroid sulfatase (STS) and specific for this enzyme relative to human arylsulfatases A and B. In cellular assays with human keratinocytes, sebocytes and fibroblasts, 1 blocked STS activity with IC(50) values in the range of 0.15-0.8 nM, and in MCF-7 breast cancer cells with IC(50)=2.3 nM, while it did not bind to estrogen receptors alpha and beta. Thus, 1 is a candidate for further investigation of its potential as a drug to be used in androgen- and estrogen-dependent diseases.

Enzyme Inhibitors↗

PubMed2003

Estrogenic potential of 2-alkyl-4-(thio)chromenone 6-O-sulfamates: potent inhibitors of human steroid sulfatase.

2-Alkylchromen-4-one 6-O-sulfamates, a new class of potent steroid sulfatase (STS) inhibitors, were evaluated for their estrogenic potential. Structure-activity relationships for estrogenic activity were identified; however, no correlation with STS inhibition was found. Estrogenicity is favored by bulky side chains and can be effectively abrogated by an (additional) linear substituent. Compound 2g, which lacks estrogenicity while potently inhibiting STS, has an ideal in vitro profile for the treatment of breast cancer.

Benzopyrans↗

PubMed2003

Nortropinyl-arylsulfonylureas as novel, reversible inhibitors of human steroid sulfatase.

Steroid sulfatase (STS) has emerged as an attractive target for a range of estrogen- and androgen-dependent diseases. Searching for novel chemotypes as STS inhibitors, we identified nortropinyl-arylsulfonylurea 3 as a hit from high-throughput screening. A series of analogues was prepared in order to explore the essential structural elements for STS inhibition, and first structure-activity relationships were established. Mechanistic investigations revealed that the compounds are reversible, competitive inhibitors of STS.

Animals↗

PubMed2003

Phosphorylation of the immunomodulatory drug FTY720 by sphingosine kinases.

The immunomodulatory drug FTY720 is phosphorylated in vivo, and the resulting FTY720 phosphate as a ligand for sphingosine-1-phosphate receptors is responsible for the unique biological effects of the compound. So far, phosphorylation of FTY720 by murine sphingosine kinase (SPHK) 1a had been documented. We found that, while FTY720 is also phosphorylated by human SPHK1, the human type 2 isoform phosphorylates the drug 30-fold more efficiently, because of a lower Km of FTY720 for SPHK2. Similarly, murine SPHK2 was more efficient than SPHK1a. Among splice variants of the human SPHKs, an N-terminally extended SPHK2 isoform was even more active than SPHK2 itself. Further SPHK superfamily members, namely ceramide kinase and a "SPHK-like" protein, failed to phosphorylate sphingosine and FTY720. Thus, only SPHK1 and 2 appear to be capable of phosphorylating FTY720. Using selective assay conditions, SPHK1 and 2 activities in murine tissues were measured. While activity of SPHK2 toward sphingosine was generally lower than of SPHK1, FTY720 phosphorylation was higher under conditions favoring SPHK2. In human endothelial cells, while activity of SPHK1 toward sphingosine was 2-fold higher than of SPHK2, FTY720 phosphorylation was 7-fold faster under SPHK2 assay conditions. Finally, FTY720 was poorly phosphorylated in human blood as compared with rodent blood, in line with the low activity of SPHK1 and in particular of SPHK2 in human blood. To conclude, both SPHK1 and 2 are capable of phosphorylating FTY720, but SPHK2 is quantitatively more important than SPHK1.

Animals↗

PubMed2003

Microtiter plate cellular assay for human steroid sulfatase with fluorescence readout.

Steroid sulfatase (STS; E.C. 3.1.6.2) is an enzyme involved in the local production of estrogens and androgens in target organs. Inhibitors of steroid sulfatase activity are considered novel therapeutic agents for the treatment of different pathologic conditions, including cancers of breast, endometrium, and prostate and disorders of the pilosebaceous unit. Evaluation of steroid sulfatase inhibition in cells up to now has been a cumbersome process, involving the extraction of a radioactive cleavage product into organic solvents. Here, we describe a rapid, nonradioactive cellular assay in microtiter plate format, using 4-methylumbelliferyl sulfate as a substrate. The reaction product, 4-methylumbelliferone, is read in a fluorescence microtiter plate reader. Several cell lines were assayed for sulfatase activity. To increase the sensitivity of the assay, we developed a Chinese hamster ovary (CHO) cell line stably transfected with a cDNA encoding the human steroid sulfatase. The steroid sulfatase activity in transfected cells correlated with the presence of the enzyme in these cells, as determined by immunofluorescence. For most STS inhibitors tested, including estrone-3-O-sulfamate, the results from the CHO cellular assay were in good agreement with those from a standard cell-free assay.

Animals↗

PubMed2003

S-1360 Shionogi-GlaxoSmithKline.

Shionogi and GlaxoSmithKline, as the joint venture company Shionogi-GlaxoSmithKline Pharmaceuticals, is developing S-1360, an HIV integrase inhibitor as a potential treatment for HIV infection. As of October 2002, phase II trials were ongoing and launch is expected in 2004/2005.

Anti-HIV Agents↗

PubMed2003

HPV vaccine MedImmune/GlaxoSmithKline.

MedImmune, in collaboration with GlaxoSmithKline, is developing a vaccine consisting of self-assembling, virus-like particles for the prevention of human papillomavirus (HPV) infection of the genital tract and associated cervical cancer. The vaccine candidates include the prototype vaccine, MEDI-501 (a vaccine directed against HPV-11), MEDI-503 (directed against HPV-16) and MEDI-504 (directed against HPV-18). Following phase I studies, the HPV-16 and HPV-18 components were combined into a multivalent vaccine for subsequent trials; this vaccine is known as MEDI-517. Phase II trials of MEDI-517 were initiated by January 2000 and are currently ongoing.

Clinical Trials, Phase I as Topic↗

PubMed2002

2-Substituted 4-(thio)chromenone 6-O-sulfamates: potent inhibitors of human steroid sulfatase.

Steroid sulfatase (STS) has emerged as a highly attractive target for the therapy of a number of disorders. Starting with the known inhibitor estrone sulfamate (1) as lead compound and with the finding that steroid sulfamates containing a nonaromatic A-ring are inactive, chromen-4-one sulfamates were designed, prepared, and tested for their ability to block human STS. This new class of nonsteroidal inhibitors shows high potency when the sulfamate group and the side chain are situated in diagonally opposite positions (i.e., 2,6- and 3,7-substitution pattern). The highest activity is achieved with fully branched, bulky aliphatic side chains and with thiochromen-4-one as the core element. 2-(1-Adamantyl)-4H-thiochromen-4-on-6-O-sulfamate (6c) is the most potent STS inhibitor discovered so far, and it is about 170-fold superior to 1. As with 1, all chromenone sulfamates are irreversible inhibitors of STS with a biphasic time course of inactivation.

Adamantane↗

PubMed2002

4,4'-Benzophenone-O,O'-disulfamate: a potent inhibitor of steroid sulfatase.

We investigated whether the benzophenone moiety can be used as core element of steroid sulfatase (STS) inhibitors. While 4- and 3-benzophenone-O-sulfamates inhibit STS with IC(50) values between 5 and 7 microM irrespective of additional hydroxy and methoxy substituents at the second phenyl ring, benzophenone-O,O'-disulfamates show increased activity. With an IC(50) value of 190 nM the 4,4'-derivative is the first small monocyclic STS inhibitor coming close to the potency of the steroidal standard estrone sulfamate.

Arylsulfatases↗

PubMed2002

Thymosin alpha1. SciClone Pharmaceuticals.

Thymosin alpha1 (Talpha1), a synthetic 28-amino acid peptide with multiple biological activities primarily directed towards immune response enhancement, was originally developed by Alpha 1 Biomedicals for the treatment of hepatitis B virus (HBV) infection. SciClone developed and launched Talpha1, under the trade name Zadaxin, for the treatment of HBV and hepatitis C virus (HCV) infections. The drug is also being developed for the treatment of non-small cell lung cancer (NSCLC), hepatocellular carcinoma, AIDS and malignant melanoma. Talpha1 is able to potentiate the action of cytokines and also reduce the hematological toxicity of cytotoxic drug therapy (cyclophosphamide-, 5-fluorouracil-, dacarbazine- or ifosfamide-based regimens). These studies also demonstrated the mechanism of action of Talpha1 and its role as an immune system enhancer. By July 2001, it was in phase III trials in the US in combination with PEGylated interferon-alpha, and later the same month it was approved in the Philippines. SciClone received expanded approval for HBV and HCV infection in Mexico in July 2001. Talpha1 has been launched in Argentina, China, Peru, the Philippines and Singapore for the treatment of chronic HBV infection. The product subsequently received expanded approval for the treatment of both HBV and HCV infection in Argentina. Marketing approval was granted in India for HBV infection in February 2001. The company was working to expand this approval to include HCV infection. In March 2000, approval for treatment of HBV infection was granted in Thailand, Laos and Malta. Approval was also granted in Sri Lanka and Brunei in August 1999. In September 2000, SciClone announced that approval had been expanded to include the treatment of HCV infection as well as the previously approved HBV indication in both Peru and Sri Lanka. In January 1999, SciClone received approval for Talpha1 in Venezuela for the treatment of HBV and HCV infection. The company also filed a marketing application in New Zealand for Talpha1 to treat HBV infection. The drug was approved in South Korea in April 2000, as an influenza vaccine adjuvant and this was expected to be expanded to indude use for treatment of both HBV and HCV infections. In July 2001, it was approved in In September and October 2000, SciClone was granted patents in Mexico and Canada, respectively, for the use of Talpha1 for the treatment of HCV infection. In June 2000, SciClone was issued a Notice of Allowance by the US Patent and Trademark Office for use of Talpha1 in the treatment of HBV infection. The EPO granted a patent, exclusively licensed to SciClone, for the use of Talpha1 as a monotherapy or in combination with interferon, to treat for HCV infection. In April 2001, SciClone received a Notice of Allowance for a US patent covering newly described analogs of Talpha1. The patent gave the Philippines as an adjuvant to chemotherapy for the treatment of various cancers. In December 2001, Talpha1 entered a phase 1 trial program in Europe, with patient enrolment planned for 2002. SciClone exclusive composition-of-matter rights to several families of Talpha1 analogs that could have proprietary therapeutic or biologic distinctions from Talpha1. The company was issued US patents covering the use of Talpha1 for the treatment of HCV infection in August 1998 and the treatment of HBV infection in September 1999. A Notice of Allowance for a second US patent covering the use of Talpha1 was issued in October 1999. In April 1999, SciClone received allowance of a patent from the EPO covering the use of Talpha1 in small cell and non-small cell lung cancer. In August 2001, SciClone received a notice of allowance for patent protection in Japan covering the use of Talpha1. The patent, which extends until 2012, also covers the use of Talpha1 in combination with interferon-alpha for the treatment of HCV infection. SciClone was previously granted a Japanese patent for the use of Talpha1 in the treatment of HBV infection.

Adjuvants, Immunologic↗

PubMedDate not supplied

The effect of topical pimecrolimus on keratoconjunctivitis sicca and chronic superficial keratitis in dogs: results from an exploratory study.

OBJECTIVE: Pimecrolimus is an ascomycin derivative that interferes selectively with the activation of T cells and mast cells and inhibits the production of inflammatory cytokines. This study evaluated the efficacy of an experimental ophthalmic formulation of pimecrolimus in treating keratoconjunctivitis sicca (KCS) and chronic superficial keratitis (CSK) in dogs. ANIMALS AND PROCEDURES: Eight dogs with KCS and six with CSK were included. The dogs were of various breeds, suffered from chronic conditions, and had been pretreated unsuccessfully. The affected eyes were treated with 1 drop of an experimental, corn oil-based pimecrolimus 1% formulation three times a day. Parameters evaluated included Schirmer tear test (STT), ocular discharge, conjunctival inflammation, corneal inflammatory cell infiltrate and scarring, and comfort level. RESULTS: The effect of pimecrolimus 1% was pronounced (increase in STT values to higher than 4 mm/min, no signs of inflammation) or moderate (increase in STT values of 3-4 mm/min, mild signs of corneal/conjunctival inflammation) in a total of 6/8 animals with KCS. In 4/6 animals with CSK, the effect was either pronounced (total regression of fibrovascular infiltration into the cornea, no corneal scarring) or moderate (distinct regression of pannus, mild corneal scarring). The response to treatment was unsatisfactory in four of 14 animals. CONCLUSION: Results of this exploratory study suggest that topical 1% pimecrolimus may be a new effective treatment for keratoconjunctivitis sicca and chronic superficial keratitis in dogs.

Animals↗