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Biomedical subjects

A Fässler

Publications and source records attributed to A Fässler.

8 recordsLinked to original sources
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↗
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↗
PubMed1996

Synthesis of potent and orally active HIV-protease inhibitors.

A series of potent HIV-protease inhibitors has been prepared. Several of the newly synthesized compounds showed high plasma even after oral administration to animals. Based on the overall biological profile, CGP 61755 was chosen for further preclinical evaluation. For this compound, a 10 step synthesis potentially suitable for large scale production was developed.

Administration, Oral↗
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↗
PubMed1980

[Glaucomatous visual fields: observation of development with the Octopus automatic perimeter (author's transl)].

The analytical program Delta was used to determine long-term fluctuations and accuracy of measurement of the program 31 of the Octopus when used with glaucoma patients. Program 31 examines the 30 degree field. The test locations are arranged in a square grid with 6 degree resolution. The program Delta determines and compares 1) the disturbed area in %; 2) the total loss, the total sensitivity being around 2000 dB; 3) the total loss in dB per mean number of disturbed points. 32 eyes of 22 patients with established glaucomatous field defects were examined twice within 2 to 6 days and 2 months later, twice again within this number of days. The size of the disturbed area served for classification of our sample into 3 groups: 1st group: disturbed area 1-33%; 2nd group: disturbed area 34-66%; 3rd group: disturbed area 67-100%. Long-term fluctuations and accuracy of measurement were determined as follows: 1) Disturbed area between 0.7 +/- 8% in group 3 and 1.7 +/- 13% in group 2. 2) The total loss increases proportionately to the disturbed area and was 4.9 +/- 29.2 dB in group 1 and 31.8 +/- 82.4 dB in group 3. 3) The total loss per mean number of disturbed points was 0.5 +/- 2 dB in group 1 and 0.3 +/- 1.2 dB in group 2. This means that, if the learning effect is over, changes of more than 2 dB, especially if several adjacent points are affected, are a significant loss, the learning effect, as determined in an earlier study, may go up as high as 2dB per point.

Adult↗
PubMed1979

Effects of taurine, glycine and GABA on convulsions produced by strychnine in the rabbit.

The action of intravenously injected taurine, glycine and GABA has been tested on convulsions induced by strychnine using electroencephalographic and electromyographic recordings. The dose of strychnine necessary to produce a generalized tonic-clonic seizure was 0.55 +/- 0.15 mg/kg intravenously for rabbits pretreated with taurine, which was significantly higher than for control animals (0.38 +/- 0.13 mg/kg). After pretreatment with glycine, the strychnine dose required to evoke convulsions (0.51 +/- 0.22 mg/kg) was also higher than the control values, but the difference was statistically not significant. The convulsive dose of strychnine in animals pretreated with GABA was slightly but not significantly lower than in control animals (0.31 +/- 0.13 mg/kg). These results suggest that taurine is the most effective amino acid to protect rabbits from seizures induced by strychnine.

Animals↗