PubMed Health⌕ Search

Biomedical subjects

D J Kempf

Publications and source records attributed to D J Kempf.

At least 37 records · Page 2Linked to original sources
PubMed1995

ABT-538 is a potent inhibitor of human immunodeficiency virus protease and has high oral bioavailability in humans.

Examination of the structural basis for antiviral activity, oral pharmacokinetics, and hepatic metabolism among a series of symmetry-based inhibitors of the human immunodeficiency virus (HIV) protease led to the discovery of ABT-538, a promising experimental drug for the therapeutic intervention in acquired immunodeficiency syndrome (AIDS). ABT-538 exhibited potent in vitro activity against laboratory and clinical strains of HIV-1 [50% effective concentration (EC50) = 0.022-0.13 microM] and HIV-2 (EC50 = 0.16 microM). Following a single 10-mg/kg oral dose, plasma concentrations in rat, dog, and monkey exceeded the in vitro antiviral EC50 for > 12 h. In human trials, a single 400-mg dose of ABT-538 displayed a prolonged absorption profile and achieved a peak plasma concentration in excess of 5 micrograms/ml. These findings demonstrate that high oral bioavailability can be achieved in humans with peptidomimetic inhibitors of HIV protease.

Administration, Oral↗
PubMed1995

Selection and analysis of human immunodeficiency virus type 1 variants with increased resistance to ABT-538, a novel protease inhibitor.

Inhibitors of the human immunodeficiency virus protease represent a promising new class of antiretroviral drugs for the treatment of AIDS. We now report the in vitro selection of viral variants with decreased sensitivity to a symmetry-based protease inhibitor, ABT-538, currently being tested in clinical trials. Molecular characterization of the variants shows that an isoleucine-to-valine substitution at position 84 results in a substantial decrease in sensitivity to the drug. Moreover, an additional mutation at position 82, valine to phenylalanine, further decreases viral susceptibility to ABT-538. Three-dimensional analysis of the protease-drug complex provides a structural explanation for the relative drug resistance induced by these two mutations. These findings emphasize the importance of closely monitoring patients receiving ABT-538 for the emergence of viral resistance and provide information that may prove useful in designing the next generation of protease inhibitors.

Amino Acid Sequence↗
PubMed1994

Selection of multiple human immunodeficiency virus type 1 variants that encode viral proteases with decreased sensitivity to an inhibitor of the viral protease.

Inhibitors of the human immunodeficiency virus type 1 (HIV-1) protease represent a promising addition to the available agents used to inhibit virus replication in a therapeutic setting. HIV-1 is capable of generating phenotypic variants in the face of a variety of selective pressures. The potential to generate variants with reduced sensitivity to a protease inhibitor was examined by selecting for virus growth in cell culture in the presence of the protease inhibitor A-77003. Virus variants grew out in the presence of the inhibitor, and these variants encoded proteases with reduced sensitivity to the inhibitor. Variants were identified that encoded changes in each of the three subsites of the protease that interact with the inhibitor. HIV-1 displays significant potential for altering its interaction with this protease inhibitor, suggesting the need for multiple protease inhibitors with varying specificities.

Amino Acid Sequence↗
PubMed1994

Design of orally bioavailable, symmetry-based inhibitors of HIV protease.

A series of novel inhibitors of HIV-1 protease with excellent oral bioavailability is described. Differential acylation of the two amino groups of symmetry-based diamine core groups 2-5 led to unsymmetrically substituted inhibitors 17-43, many of which inhibited HIV protease at subnanomolar concentrations. Anti-HIV activity in vitro was observed at 0.1-1 microM. A systematic evaluation of the pharmacokinetic behavior of these inhibitors in rats identified the influence of aqueous solubility, molecular size and hydrogen-bonding functionality. Compound 30 (A-80987) was selected for further evaluation based on a favorable Cmax/ ED50 ratio (> 20) and half-life (> 2 h).

Administration, Oral↗
PubMed1994

A C2 symmetry-based HIV protease inhibitor, A77003, irreversibly inhibits infectivity of HIV-1 in vitro.

A C2 symmetry-based HIV protease inhibitor, A77003, exerts potent antiviral activity against a wide spectrum of HIV isolates in vitro. In this study, we asked whether A77003 could cause irreversible conformational changes to HIV-1, whether the amounts of viral RNA and p24 capsid protein per virion were altered, and how the infectivity of the virus produced in the presence of the drug was affected. We found that the number of viral particles and per-virion viral RNA content of the virus produced in the presence of A77003 did not significantly differ from those of the virus produced in the absence of the drug, whereas significant morphological changes were observed as assessed by transmission electron microscopy. However, the virus produced in the presence of A77003 contained substantially less p24gag protein per virion particle as compared to those produced in the absence of the drug or in the presence of AZT. Virions produced in the presence of A77003 showed up to 50-fold less infectious capability in subsequent tissue culture than control virions produced in the absence of drug or in the presence of AZT. This reduction in infectivity was maintained for at least 10 days in culture. The present data suggest that A77003 impairs HIV-1 protease-mediated Gag processing, interferes with the assembly and maturation of the virus, and leads to an irreversible loss of the infectivity of the virus, although a low but positive level of reversion to infectivity during the 10-day assay occurs. These features of A77003 (and perhaps similar HIV protease inhibitors as well) anti-HIV activity should represent desirable properties for antiviral therapy of AIDS and related diseases.

Antiviral Agents↗
PubMed1994

Human immunodeficiency virus type 1 virions composed of unprocessed Gag and Gag-Pol precursors are capable of reverse transcribing viral genomic RNA.

The structural proteins and enzymes of the human immunodeficiency virus type 1 core are translated as part of two polyprotein precursors, Gag and Gag-Pol, which are cleaved by a virally encoded protease. Viruses grown in the presence of inhibitors of the protease contain core particles that are aberrantly assembled, and upon infection of susceptible cells, they do not synthesize viral DNA. Through the use of a proteinase inhibitor (A77003), we determined that the viral reverse transcriptase can efficiently synthesize viral DNA as part of the unprocessed Gag-Pol precursor. We also found that the stabilities of core particles composed of unprocessed precursors were considerably enhanced. These observations suggest that for viruses composed of unprocessed precursors, replication is interrupted before the reverse transcription step.

DNA, Viral↗
PubMed1994

Characterization of human immunodeficiency virus type 1 variants with increased resistance to a C2-symmetric protease inhibitor.

Inhibitors of the human immunodeficiency virus type 1 protease represent a promising class of antiviral drugs for the treatment of AIDS, and several are now in clinical trials. Here, we report the in vitro selection of viral variants with decreased sensitivity to a C2-symmetric protease inhibitor (A-77003). We show that a single amino acid substitution (Arg to Gln or Lys) at position 8 of the protease results in a substantial decrease in the inhibitory activity of the drug on the enzyme and a comparable increase in viral resistance. These findings, when analyzed by using the three-dimensional structure of the protease-drug complex, provide a strategic guide for the future development of inhibitors of the human immunodeficiency virus type 1 protease.

Amino Acid Sequence↗
PubMed1993

Symmetry-based inhibitors of HIV protease. Structure-activity studies of acylated 2,4-diamino-1,5-diphenyl-3-hydroxypentane and 2,5-diamino-1,6-diphenylhexane-3,4-diol.

The structure-activity relationships in two series of novel, symmetry-based inhibitors of HIV protease, the enzyme responsible for maturation of the human immunodeficiency virus, are described. Beginning with lead compounds 3-6, the effect of adding polar, heterocyclic end groups to one or both ends of the symmetric or pseudosymmetric inhibitors was probed. Aqueous solubility was enhanced > 1000-fold while maintaining potent inhibition of purified HIV-1 protease and anti-HIV activity in vitro. Pharmacokinetic studies in rats indicated a substantial difference in the absorption properties of mono-ol-based and diol-based inhibitors. The oral bioavailability of inhibitor 19 in rats was 19%; however, the Cmax obtained failed to exceed the anti-HIV EC50 in vitro. Substantial plasma levels of potent inhibitors of the diol class were not obtained after oral administration in rats; however, the optimal combination of aqueous solubility and in vitro antiviral activity of several inhibitors support their potential use in intravenous therapy.

Amino Alcohols↗
PubMed1993

Partial inhibition of the human immunodeficiency virus type 1 protease results in aberrant virus assembly and the formation of noninfectious particles.

The production of infectious particles by human immunodeficiency virus type 1 is dependent on the accurate cleavage of its Gag and Gag/Pol precursors by a virally encoded protease. In the absence of protease activity, morphologically abnormal particles which are noninfectious are formed. Recently, inhibitors of the protease of human immunodeficiency virus type 1 have been developed as potential therapeutic agents. We have examined the basis for the loss of infectivity at the limiting inhibitor concentrations that are likely to be achieved in clinical settings. We found that subtle defects in processing are correlated with profound deficits in infectivity. Further, we correlated this partially disrupted processing with an altered virion morphology. These data suggest that accurate and complete processing is essential to the formation of infectious, morphologically normal virions and that the pathway by which these precursors are processed and assembled is sensitive to partial inhibition of the protease by an inhibitor disproportionate to the effect of the inhibitor on the viral protease itself.

Cells, Cultured↗
PubMed1992

In vitro inhibition of human immunodeficiency virus (HIV) type 1 replication by C2 symmetry-based HIV protease inhibitors as single agents or in combinations.

C2 symmetry-based human immunodeficiency virus (HIV) protease inhibitors were examined in vitro as single agents or in combination with 3'-azido-2',3'-dideoxythymidine (AZT) or 2',3'-dideoxyinosine for activity against HIV type 1 (HIV-1). Ten C2 symmetry-based or pseudo-C2 symmetry-based HIV protease inhibitors were active against a laboratory strain (HIV-1IIIB) in the HIV-1 cytopathic effect inhibition assay. Three inhibitors, A75925, A76928, and A77003, selected to represent a range of aqueous solubility and antiviral activity, were active against four different HIV-1 strains tested. These three inhibitors exhibited a significant inhibition of the cytopathic effect of HIV-1 against the CD4+ ATH8 cell line, with 90% inhibitory concentrations ranging from 0.1 to 4 microM. Cellular toxicity was negligible at up to 20 microM. Furthermore, they completely inhibited the replication of monocytotropic strain HIV-1Ba-L in purified monocytes and macrophages at 0.75 to 2 microM. Potent inhibitory activity against a primary HIV-1 isolate and an AZT-resistant HIV-1 variant was also observed for all three inhibitors in phytohemagglutinin-activated peripheral blood mononuclear cells. When these three HIV protease inhibitors and AZT or 2',3'-dideoxyinosine were used in combinations against a primary HIV isolate in phytohemagglutinin-activated peripheral blood mononuclear cells and the results were analyzed with the COMBO program package, their antiviral activities were identified to be synergistic in some cases and additive in others. The present data warrant further investigations of these compounds as potential antiviral agents for the therapy of HIV infections.

Didanosine↗
PubMed1991

Potent HIV-1 protease inhibitors with antiviral activities in vitro.

A series of novel difluoroketones with low molecular weight (less than 600 m.u.) and which are potent inhibitors of the HIV-1 protease (IC50 = 1.0 to 21 nM) were synthesized. These compounds also exhibited antiviral activity by inhibition of the cytopathic effect of HIV-1(3)B in MT-4 cells in vitro.

Antiviral Agents↗
PubMed1991

Antiviral and pharmacokinetic properties of C2 symmetric inhibitors of the human immunodeficiency virus type 1 protease.

Specific processing of the human immunodeficiency virus (HIV) gag and gag-pol polyprotein gene products by the HIV protease is essential for the production of mature, infections progeny virions. Inhibitors of HIV protease block this maturation and thus prohibit the spread of HIV in vitro. Previously, we reported a series of novel, symmetric inhibitors of HIV protease designed to match the C2 symmetric structure of the active site of the enzyme. In response to the poor aqueous solubility of those lead compounds, we designed a series of analogs with substantially improved (greater than 10(4) fold) solubility. These inhibitors showed anti-HIV activity in H9 and MT4 cells at 0.05 to 10 microM, and in most cases, they were noncytotoxic at concentrations in excess of 100 microM. Further examination of one inhibitor (A-77003) revealed broad-spectrum activity against both HIV types 1 and 2, including azidothymidine-resistant HIV, in a variety of transformed and primary human cell lines. After administration of the inhibitors to rats, short half-lives and, with two notable exceptions, moderate oral bioavailability were observed. Additional pharmacokinetic studies in dogs and monkeys revealed the potential utility of A-77003 as an intravenous anti-HIV agent.

Amino Acid Sequence↗
PubMed1991

Stereocontrolled synthesis of psi[CH = CH] dipeptide isosteres.

A new stereocontrolled synthesis of the psi[CH = CH] dipeptide isostere is described. They key step of the sequence relies on the stereospecific alpha-alkylation of delta-amino-gamma-mesyloxy-alpha,beta-unsaturated esters. The broad availability of nucleophilic alpha-side chains by this method allows the preparation of a wide variety of psi[CH = CH] isosteres with predictable stereochemistry.

Alkylation↗
PubMed1990

Design, activity, and 2.8 A crystal structure of a C2 symmetric inhibitor complexed to HIV-1 protease.

A two-fold (C2) symmetric inhibitor of the protease of human immunodeficiency virus type-1 (HIV-1) has been designed on the basis of the three-dimensional symmetry of the enzyme active site. The symmetric molecule inhibited both protease activity and acute HIV-1 infection in vitro, was at least 10,000-fold more potent against HIV-1 protease than against related enzymes, and appeared to be stable to degradative enzymes. The 2.8 angstrom crystal structure of the inhibitor-enzyme complex demonstrated that the inhibitor binds to the enzyme in a highly symmetric fashion.

Amino Acid Sequence↗
PubMed1990

Renin inhibitors based on dipeptide analogues. Incorporation of the hydroxyethylene isostere at the P2/P3 sites.

The synthesis of a series of renin inhibitors in which the P2 and P3 amino acids are replaced with the hydroxyethylene dipeptide isostere is reported. In vitro evaluation of the inhibitors has revealed that this isostere is an acceptable amide-bond replacement in which activity is maintained and stability is enhanced. Structure-activity relationships of this series resemble but do not parallel those of the corresponding dipeptide-containing inhibitors.

Chemical Phenomena↗
PubMed1990

Potent, low molecular weight renin inhibitors containing a C-terminal heterocycle: hydrogen bonding at the active site.

A series of low-nanomolar renin inhibitors containing novel C-terminal heterocycles has been designed by formally cyclizing the C-terminus of a glycol-based inhibitor to the second hydroxyl. Molecular modeling suggests that the heterocyclic oxygen hydrogen bonds as an acceptor to the flap region of renin and that the second hydroxyl in the glycol-based inhibitors behaves similarly.

Carbamates↗