Biomedical subjects

J Rösel

Publications and source records attributed to J Rösel.

14 recordsLinked to original sources

PubMed2000

New anilinophthalazines as potent and orally well absorbed inhibitors of the VEGF receptor tyrosine kinases useful as antagonists of tumor-driven angiogenesis.

The sprouting of new blood vessels, or angiogenesis, is necessary for any solid tumor to grow large enough to cause life-threatening disease. Vascular endothelial growth factor (VEGF) is one of the key promoters of tumor induced angiogenesis. VEGF receptors, the tyrosine kinases Flt-1 and KDR, are expressed on vascular endothelial cells and initiate angiogenesis upon activation by VEGF. 1-Anilino-(4-pyridylmethyl)-phthalazines, such as CGP 79787D (or PTK787 / ZK222584), reversibly inhibit Flt-1 and KDR with IC(50) values < 0.1 microM. CGP 79787D also blocks the VEGF-induced receptor autophosphorylation in CHO cells ectopically expressing the KDR receptor (ED(50) = 34 nM). Modification of the 1-anilino moiety afforded derivatives with higher selectivity for the VEGF receptor tyrosine kinases Flt-1 and KDR compared to the related receptor tyrosine kinases PDGF-R and c-Kit. Since these 1-anilino-(4-pyridylmethyl)phthalazines are orally well absorbed, these compounds qualify for further profiling and as candidates for clinical evaluation.

Administration, Oral↗

PubMed2000

PTK787/ZK 222584, a novel and potent inhibitor of vascular endothelial growth factor receptor tyrosine kinases, impairs vascular endothelial growth factor-induced responses and tumor growth after oral administration.

PTK787/ZK 222584 (1-[4-chloroanilino]-4-[4-pyridylmethyl] phthalazine succinate) is a potent inhibitor of vascular endothelial growth factor (VEGF) receptor tyrosine kinases, active in the submicromolar range. It also inhibits other class III kinases, such as the platelet-derived growth factor (PDGF) receptor beta tyrosine kinase, c-Kit, and c-Fms, but at higher concentrations. It is not active against kinases from other receptor families, such as epidermal growth factor receptor, fibroblast growth factor receptor-1, c-Met, and Tie-2, or intracellular kinases such as c-Src, c-Abl, and protein kinase C-alpha. PTK787/ZK 222584 inhibits VEGF-induced autophosphorylation of kinase insert domain-containing receptor (KDR), endothelial cell proliferation, migration, and survival in the nanomolar range in cell-based assays. In concentrations up to 1 microM, PTK787/ZK 222584 does not have any cytotoxic or antiproliferative effect on cells that do not express VEGF receptors. After oral dosing (50 mg/kg) to mice, plasma concentrations of PTK787/ZK 222584 remain above 1 microM for more than 8 h. PTK787/ZK 222584 induces dose-dependent inhibition of VEGF and PDGF-induced angiogenesis in a growth factor implant model, as well as a tumor cell-driven angiogenesis model after once-daily oral dosing (25-100 mg/kg). In the same dose range, it also inhibits the growth of several human carcinomas, grown s.c. in nude mice, as well as a murine renal carcinoma and its metastases in a syngeneic, orthotopic model. Histological examination of tumors revealed inhibition of microvessel formation in the interior of the tumor. PTK787/ZK 222584 is very well tolerated and does not impair wound healing. It also does not have any significant effects on circulating blood cells or bone marrow leukocytes as a single agent or impair hematopoetic recovery after concomitant cytotoxic anti-cancer agent challenge. This novel compound has therapeutic potential for the treatment of solid tumors and other diseases where angiogenesis plays an important role.

Angiogenesis Inhibitors↗

PubMed1999

Mechanisms and kinetics of procathepsin D activation.

In vitro, procathepsin D is activated to pseudocathepsin D by incubation at low pH. To investigate the mechanism of this activation, recombinant human procathepsin D and two mutants were generated in a baculovirus expression system. One mutant carried a point mutation within the catalytic domain, which resulted in a catalytically inactive enzyme form (D77A). The other carried a point mutation within the propeptide, which prevented activation by processing at the 'autoproteolysis-site' (L26P). Neither mutant is capable of processing itself to form pseudocathepsin D, and L26P is not able to process D77A. Despite the inability of L26P to cleave either its own or a wild-type prosequence, it did exhibit activity against a synthetic peptide substrate. The ability of intact precursor (zymogen) to cleave a peptide, but not a protein substrate, offers new insights into the mechanism of inhibition by the propeptide. Mature cathepsin D can process the inactive D77A mutant to the pseudoform, demonstrating that processed species are capable of cleaving zymogen molecules in an intermolecular interaction. In addition, kinetic studies provide evidence for a two-phase mechanism for the conversion of procathepsin D to pseudocathepsin D, one phase where the first molecules of pseudocathepsin D are formed at a low rate and a second phase where the process is autocatalytically accelerated by newly formed pseudocathepsin D molecules. Finally, with the help of the mutants L26P and D77A it was observed that at least two additional proteinase activities, found in conditioned media from insect cell culture, are capable of activating procathepsin D by cleaving it within the proregion. This observation suggests that there are likely to be multiple proteinases in the extracellular matrix that are capable of activating procathepsin D, thereby triggering the second autocatalytic phase. This may also be important for solid tumors, where the presence of cathepsin D has been correlated with tumor growth and invasion.

Amino Acid Sequence↗

PubMed1999

Author errata.

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Retraction Notice↗

PubMed1998

New aza-dipeptide analogues as potent and orally absorbed HIV-1 protease inhibitors: candidates for clinical development.

On the basis of previously described X-ray studies of an enzyme/aza-dipeptide complex,8 aza-dipeptide analogues carrying N-(bis-aryl-methyl) substituents on the (hydroxethyl)hydrazine moiety have been designed and synthesized as HIV-1 protease inhibitors. By using either equally (12) or orthogonally (13) protected dipeptide isosteres, symmetrically and asymmetrically acylated aza-dipeptides can be synthesized. This approach led to the discovery of very potent inhibitors with antiviral activities (ED50) in the subnanomolar range. Acylation of the (hydroxethyl)hydrazine dipeptide isostere with the L-tert-leucine derivative 29 increased the oral bioavailability significantly when compared to the corresponding L-valine or L-isoleucine derivatives. The bis(L-tert-leucine) derivatives CGP 75355, CGP 73547, CGP 75136, and CGP 75176 combine excellent antiviral activity with high blood concentration after oral administration. Furthermore, they show no cross-resistance with saquinavir-resistant strains and maintain activity against indinavir-resistant ones. Consequently they qualify for further profiling as potential clinical candidates.

Administration, Oral↗

PubMed1998

One-step purification of cathepsin D by affinity chromatography using immobilized propeptide sequences.

In vivo, active cathepsin D proteinase is generated by removal of a 44-residue propeptide at its N-terminus. Here we report that mature cathepsin D and pseudocathepsin D (a partially activated form of cathepsin D with 25 amino acid residues removed from the propeptide) bind to the immobilized propeptide, while procathepsin D does not. The N-terminal 25 amino acid residues of the propeptide are sufficient for this binding. Based on this observation, a simple one-step procedure was developed to purify mature cathepsin D from whole cell extracts to near homogeneity. This method has the advantage over existing affinity-purification systems that active forms of the proteinase can be separated from inactive precursors and other aspartic proteinases. Furthermore, this technique was effective for pepsin as well, suggesting it may have general utility for all activated aspartic proteinases and perhaps other families of proteinases.

Amino Acid Sequence↗

PubMed1997

Semicochliodinol A and B: inhibitors of HIV-1 protease and EGF-R protein tyrosine kinase related to asterriquinones produced by the fungus Chrysosporium merdarium.

The known bisalkylated 2,5-dihydroxybenzoquinones didemethylasterriquinone D and isocochliodinol as well as the new metabolites semicochliodinol A and B have been isolated as inhibitors of HIV-1 protease from the culture broth of the fungus Chrysosporium merdarium P-5656. The structures were elucidated by spectroscopic methods. The NMR spectra of two compounds were completely assigned. The metabolites inhibit HIV-1 protease with an IC50 value as low as 0.17 microM and epidermal growth factor receptor protein tyrosine kinase at 15 to 60 microM and are therefore valuable lead compounds for these targets. Molecular modelling of the HIV-1-protease-inhibitor complexes showed hydrogen bonding between the dihydroxybenzoquinone moiety of didemethylasterriquinone D and isocochliodinol to both active-site aspartic acids (Asp25/Asp25') of the protease and the indole parts of the inhibitors filling the P2 and P2' pockets of the protease.

Benzoquinones↗

PubMed1996

Profile of CGP 61755: a novel and potent HIV-1 protease inhibitor that shows enhanced anti-HIV activity when combined with other antiretroviral agents in vitro.

CGP 61755 is a novel hydroxyethylene derivative produced by a high yield 10 step chemical synthesis. It is highly specific for HIV-1 protease with an IC50 of 1 nM. The ED90 in MT-2, PBLs and macrophages is infected with laboratory strains of HIV-1 or clinical isolates is 30-100 nM. In chronically infected macrophages the ED90 is 1000 nM (1000 nM for saquinavir and 10 microM for indinavir). When the antiviral activity of CGP 61755 on HIV-1 infected lymphocytes was examined using serum free medium an ED99 of 60 nM was determined, while in the presence of 10% human serum the same activity was achieved with 120 nM. When examined in combination with RT inhibitors or protease inhibitors, either in a co-culture of CEM-SS and chronically infected H9IIIB cells or in a free virus lymphocyte infection, cooperativity of the antiviral activities was observed. Dog pharmacokinetic studies comparing p.o. and i.v. data indicate that CGP 61755 has a bioavailability between 50 and 80%. Following oral administration the area under the concentration curve (AUC) values increased in a dose proportional manner. The plasma levels of the drug at 6 hours after oral administration were above the ED90. Based on these properties we believe that CGP 61755 has an attractive profile that justifies further preclinical evaluation of the drug.

Animals↗

PubMed1996

Aza-peptide analogs as potent human immunodeficiency virus type-1 protease inhibitors with oral bioavailability.

A series of aza-peptide analogs with a (hydroxyethyl)hydrazine isostere has been synthesized as HIV-1 protease inhibitors using a simple synthetic scheme. Structure-activity studies based on the X-ray of a previously described inhibitor-enzyme complex led to potent inhibitors with antiviral activity in the low-nanomolar range. The S-configuration of the transition-state hydroxyl group was preferred in this series. Small modifications of the P2P3 and P2'P3' substituents had little effect on enzyme inhibition but greatly influenced the pharmacokinetic profile. As a result of these studies, the symmetrically acylated compound 8a and its close analog 24a bearing a methyl carbamate in P3 and an ethyl carbamate in P3' position were identified as potent inhibitors with plasma concentrations exceeding antiviral ED50 values 150-fold following oral application in mice.

Administration, Oral↗

PubMed1995

[(Alkylamino)methyl]acrylophenones: potent and selective inhibitors of the epidermal growth factor receptor protein tyrosine kinase.

[(Alkylamino)methyl]acrylophenones and (alkylamino)propiophenones, bearing a spacer moiety such as the benzyloxy or (benzoylsulfonyl)oxy group in the 4-position, represent a novel class of inhibitors of the epidermal growth factor (EGF) receptor protein tyrosine kinase with a high degree of selectivity versus other tyrosine and serine/threonine kinases. The most active compounds inhibited the EGF receptor protein tyrosine kinase from A431 cell membranes with IC50 values of < 0.5 microM. Derivatives with a benzyloxy substituent in the 4-position of the aromatic ring inhibited both the EGF receptor kinase and the proliferation of an EGF-dependent mouse epidermal keratinocyte cell line (BALB/MK) but were only marginally active in the inhibition of the cellular EGF-dependent tyrosine phosphorylation. Compound 18 inhibited ligand-induced tyrosine phosphorylation and BALB/MK cell proliferation with IC50 values of approximately 100 and 1.21 microM, respectively, and showed antitumor activity in vivo in a nude mouse model. However, the discrepancy between the IC50 values for antiproliferative activity and cellular tyrosine phosphorylation as well as the relatively low tolerability in animals suggests a second site of action of this class of inhibitors. Nevertheless, [(alkylamino)methyl]acrylophenones and (alkylamino)propiophenones may prove to be interesting tools for studying the action of tyrosine kinases.

Animals↗

PubMed1995

Comparative analysis of the X-ray structures of HIV-1 and HIV-2 proteases in complex with CGP 53820, a novel pseudosymmetric inhibitor.

BACKGROUND: The human immunodeficiency virus (HIV) is the causative agent of acquired immunodeficiency syndrome (AIDS). Two subtypes of the virus, HIV-1 and HIV-2, have been characterized. The protease enzymes from these two subtypes, which are aspartic acid proteases and have been found to be essential for maturation of the infectious particle, share about 50% sequence identity. Differences in substrate and inhibitor binding between these enzymes have been previously reported. RESULTS: We report the X-ray crystal structures of both HIV-1 and HIV-2 proteases each in complex with the pseudosymmetric inhibitor, CGP 53820, to 2.2 A and 2.3 A, respectively. In both structures, the entire enzyme and inhibitor could be located. The structures confirmed earlier modeling studies. Differences between the CGP 53820 inhibitory binding constants for the two enzymes could be correlated with structural differences. CONCLUSIONS: Minor sequence changes in subsites at the active site can explain some of the observed differences in substrate and inhibitor binding between the two enzymes. The information gained from this investigation may help in the design of equipotent HIV-1/HIV-2 protease inhibitors.

Amino Acid Sequence↗

PubMed1989

A derivative of staurosporine (CGP 41 251) shows selectivity for protein kinase C inhibition and in vitro anti-proliferative as well as in vivo anti-tumor activity.

Analogues of staurosporine were synthesized and their ability to inhibit protein kinases was examined. Staurosporine is a potent but non-selective inhibitor of in vitro protein kinase C(PKC) activity (IC50 6.0 nM). The derivative CGP 41 251 had reduced PKC activity with an IC50 of 50 nM but showed a high degree of selectivity when assayed for inhibition of cyclic AMP-dependent protein kinase (IC50 2.4 microM), S6 kinase (IC50 5.0 microM) and tyrosine-kinase-specific activity of epidermal growth factor receptor (IC50 3.0 microM). Staurosporine and CGP 41 251 exerted growth inhibition in the human bladder carcinoma line T-24, human promyelocytic leukemia line HL-60 and bovine corneal endothelial cells at concentrations which correlated well with in vitro PKC inhibition. In addition, both compounds inhibited the release of H2O2 from human monocytes pre-treated with 12-O-tetradecanoyl-phorbol-13-acetate at non-toxic concentrations. In vivo anti-tumor activity was examined in T-24 human bladder carcinoma xenografts in athymic nude mice. Tumor growth inhibition tests revealed significant anti-tumor activity (2p less than 0.001) at 1/10 of the maximum tolerated doses for both compounds. By contrast, a closely related derivative of staurosporine (CGP 42 700) was inactive at concentrations of over 100 microM in all in vitro enzyme and anti-proliferative assays as well as in animal tumor models. Our data suggest an association between PKC inhibition and anti-proliferative and anti-tumor activity.

Alkaloids↗

PubMed1983

Isolation of early viral proteins from poxvirus-infected chick embryo fibroblasts by DNA-cellulose chromatography and inhibition of their synthesis by chicken interferon.

Up to seven early poxvirus-specific proteins have been isolated from vaccinia-WR-infected and cowpox-virus-infected chick embryo fibroblasts by affinity chromatography on native DNA-cellulose columns. The proteins have been characterized by one-dimensional sodium dodecyl sulfate/polyacrylamide gel electrophoresis and by nonequilibrium pH-gradient electrophoresis. The molecular weights of the viral proteins were determined by comparison with proteins of known molecular weight and are comparable to several of the vaccinia-WR-specific DNA-binding proteins isolated previously from infected L-929 cells by Solosky J. M., Esteban M. and Holowczak J.A. [J. Virol. 25, 263-273 (1978)]. The viral proteins binding reversibly to native DNA have been classified as immediate early viral gene products. Synthesis of cowpox-virus-induced early DNA-binding proteins is inhibited in chick cells pretreated with homologous interferon at a concentration of 500--1000 units/ml.

Animals↗

PubMed1983

Reversible inhibition of poxvirus replication by cycloheximide during the early phase of infection.

Infection of primary chick embryo fibroblasts with Vaccinia WR, IHD-W, and cowpox virus even at high m.o.i. does not cause drastic early inhibition of host cell protein synthesis. This contrasts with the infection by these viruses of many eucaryotic cells. Cellular protein synthesis of mouse L cells is also only partially inhibited after infection with cowpox virus up to a m.o.i. of 2500 e.b. As predicted by Moss and Filler (1970, J. Virol. 5, 99-108) no irreversible inhibition of poxvirus replication is observed in these cells following the addition of cycloheximide early after infection. The viral cores which accumulate in chick embryo fibroblasts in the presence of cycloheximide are further uncoated after removal of the protein synthesis inhibitor. These poxvirus host cell systems can be used to identify in vivo immediate and putative delayed early viral gene products. Formation of progeny virus, viral DNA synthesis, the sequential formation of viral proteins, and sensitivity to interferon has been demonstrated in chick embryo fibroblasts after reversal of the cycloheximide block. These studies indicate a synchronized replication cycle of poxvirus after reversal of the cycloheximide block.

Animals↗