Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.23.16 (HIV-1 protease)
 2,107 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Indinavir (IDV) (also called CRIXIVAN, MK-639, or L-735,524) is a potent and selective inhibitor of the human immunodeficiency virus type 1 (HIV-1) protease. During early clinical trials, in which patients initiated therapy with suboptimal dosages of IDV, we monitored the emergence of viral resistance to the inhibitor by genotypic and phenotypic characterization of primary HIV-1 isolates. Development of resistance coincided with variable patterns of multiple substitutions among at least 11 protease amino acid residues. No single substitution was present in all resistant isolates, indicating that resistance evolves through multiple genetic pathways. Despite this complexity, all of 29 resistant isolates tested exhibited alteration of residues M-46 (to I or L) and/or V-82 (to A, F, or T), suggesting that screening of these residues may be useful in predicting the emergence of resistance. We also extended our previous finding that IDV-resistant viral variants exhibit various patterns of cross-resistance to a diverse panel of HIV-1 protease inhibitors. Finally, we noted an association between the number of protease amino acid substitutions and the observed level of IDV resistance. No single substitution or pair of substitutions tested gave rise to measurable viral resistance to IDV. The evolution of this resistance was found to be cumulative, indicating the need for ongoing viral replication in this process. These observations strongly suggest that therapy should be initiated with the most efficacious regimen available, both to suppress viral spread and to inhibit the replication that is required for the evolution of resistance.
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PMID:Genetic correlates of in vivo viral resistance to indinavir, a human immunodeficiency virus type 1 protease inhibitor. 897 Sep 46

Two different responses to the therapy were observed in a group of patients receiving the protease inhibitor indinavir. In one, suppression of virus replication occurred and has persisted for 90 weeks (bDNA, < 500 human immunodeficiency virus type 1 [HIV-1] RNA copies/ml). In the second group, a rebound in virus levels in plasma followed the initial sharp decline observed at the start of therapy. This was associated with the emergence of drug-resistant variants. Sequence analysis of the protease gene during the course of therapy revealed that in this second group there was a sequential acquisition of protease mutations at amino acids 46, 82, 54, 71, 89, and 90. In the six patients in this group, there was also an identical mutation in the gag p7/p1 gag protease cleavage site. In three of the patients, this change was seen as early as 6 to 10 weeks after the start of therapy. In one patient, a second mutation occurred at the gag p1/p6 cleavage site, but it appeared 18 weeks after the time of appearance of the p7/p1 mutation. Recombinant HIV-1 variants containing two or three mutations in the protease gene were constructed either with mutations at the p7/p1 cleavage site or with wild-type (WT) gag sequences. When recombinant HIV-1-containing protease mutations at 46 and 82 was grown in MT2 cells, there was a 68% reduction in its rate of replication compared to the WT virus. Introduction of an additional mutation at the gag p7/p1 protease cleavage site compensated for the partially defective protease gene. Similarly, rates of replication of viruses with mutations M46L/I, I54V, and V82A in protease were enhanced both in the presence and in the absence of Indinavir when combined with mutations in the gag p7/p1 and the gag p1/p6 cleavage sites. Optimal rates of virus replication require protease cleavage of precursor polyproteins. A mutation in the cleavage site that enhanced the availability of a protein that was rate limiting for virus maturation would confer on that virus a significant growth advantage and may explain the uniform emergence of viruses with alterations at the p7/p1 cleavage site. This is the first report of the emergence of mutations in the gag p7/p1 protease cleavage sites in patients receiving protease therapy and identifies this change as an important determinant of HIV-1 resistance to protease inhibitors in patient populations.
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PMID:Drug resistance during indinavir therapy is caused by mutations in the protease gene and in its Gag substrate cleavage sites. 926 88

The putative virulence factor secreted aspartyl proteinase (SAP) of Candida albicans and the human immunodeficiency virus type 1 (HIV-1) protease both belong to the aspartyl proteinase family. The present study demonstrates that the HIV-1 protease inhibitor Indinavir is a weak but specific inhibitor of SAP. In addition, Indinavir reduces the amount of cell bound as well as released SAP antigen from C. albicans. Furthermore, viability and growth of C. albicans are markedly reduced by Indinavir. These findings indicate that HIV-1 protease inhibitors may possess antifungal activity and we speculate that in vivo SAP inhibition may add to the resolution of mucosal candidiasis in HIV-1 infected subjects.
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PMID:Human immunodeficiency virus type 1 protease inhibitor attenuates Candida albicans virulence properties in vitro. 1042 51

The secreted aspartyl proteinase (Sap) of Candida albicans, which is believed to represent an important virulence factor of this opportunistic yeast, and the human immunodeficiency virus type 1 (HIV-1) protease, which is obligatory for the production of infectious virions, both belong to the same family of aspartyl proteinases. We have previously shown that the HIV-1 protease inhibitor Indinavir directly inhibits secretion and proteinase activity of Sap in a dose-dependent manner. Furthermore, at very high concentrations, viability of C. albicans is markedly reduced by Indinavir, indicating that HIV-1 protease inhibitors may possess antifungal activity. We thus proposed that these drugs may add to the resolution of mucosal candidiasis in HIV-1 infected subjects. We have now compared three different HIV-1 protease inhibitors. The rank order of Sap inhibition, already significant at 0.1 mg/ml for all protease inhibitors, was Ritonavir > Indinavir > Saquinavir. However, the cross-reactivity of Ritonavir to pepsin was also more pronounced compared with the other two. Indinavir did not affect Candida viability at concentrations up to 1 mg/ml, in line with our previous study. In contrast, at this concentration Saquinavir was even fungicidal as assessed by three different viability assays (colony formation assay, MTT assay, propidium iodide staining) whereas Ritonavir significantly affected the mitochondrial activity only (MTT assay). No influence on Candida viability was observed for any of the three at concentrations of 0.1 mg/ml or lower. It remains to be examined whether HIV-1 protease inhibitors or derivatives thereof may be suitable for in vivo therapy of subjects suffering from mucosal candidiasis resistant to current antimycotics.
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PMID:Dissimilar attenuation of Candida albicans virulence properties by human immunodeficiency virus type 1 protease inhibitors. 1053 86

The interaction between HIV-1 protease and reversible inhibitors was studied by surface plasmon resonance biosensor technology. The steady-state binding level and the time course of association and dissociation could be observed by measuring the binding of inhibitors injected in a continuous flow of buffer to the immobilized enzyme. Fourteen low molecular weight inhibitors (500-700 Da), including the four clinically used HIV-1 protease inhibitors (indinavir, nelfinavir, ritonavir, and saquinavir), were analyzed. Affinities were estimated as B(50) values from a series of sensorgrams at different concentrations of inhibitors. These values were found to be correlated with inhibition constants (K(i)) determined by an enzyme inhibition assay (r(2) = 0.84, logarithmic values). Dissociation rates were estimated at a single saturating concentration of the inhibitors as t(1/2,obs), but these values did not correlate with K(i) (r(2) = 0.26, logarithmic values). Indinavir had the highest affinity (B(50) = 11 nM) and the fastest dissociation (t(1/2,obs) = 500 s) among the clinically used inhibitors while saquinavir had a lower affinity (B(50) = 25 nM) and the slowest dissociation rate (t(1/2,obs) = 6500 s). Since these two inhibitors have similar K(i) values, the differences in dissociation rates reveal important characteristics in the interaction that cannot be obtained by the inhibition studies. The biosensor data are expected to be of greater in vivo relevance since the experiments were performed in a buffer more similar to physiological conditions.
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PMID:Kinetic analysis of the interaction between HIV-1 protease and inhibitors using optical biosensor technology. 1068 32

Structures of the complexes of HIV protease inhibitor L--756,423 with the HIV-1 wild-type protease and of the inhibitors Indinavir, L-739,622 and Saquinavir with the mutant protease (9X) containing nine point mutations (Leu10Val, Lys20Met, Leu24Ile, Ser37Asp, Met46Ile, Ile54Val, Leu63Pro, Ala71Val, Val82Thr) have been determined. Comparative analysis of these structures reveals an alternate binding pocket for the P1-P3 group of Indinavir and L--756, 423. The alternate binding pocket is a result of concerted structural change in the 80s loop (residues 79-82) of the protease. The 80s loop is pulled away from the active site in order to accommodate the P1-P3 group, which is sandwiched between the flap and the 80s loop. This structural change is observed for the complexes of the wild type as well as the 9X mutant protease. The study reveals that the 80s loop is an intrinsically flexible loop in the wild-type HIV-1 protease and that mutations in this loop are not necessary to result in conformational changes. Conformation of this loop in the complex depends primarily upon the nature of the bound inhibitor and may be influenced by mutations in the protease. The results underscore the need to understand the intrinsic structural plasticity of the protease for the design of effective inhibitors against the wild-type and drug-resistant enzyme forms. In addition, the alternate binding pocket for the P1-P3 group of Indinavir and L--756,423 may be exploited for the design of potent inhibitors.
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PMID:An alternate binding site for the P1-P3 group of a class of potent HIV-1 protease inhibitors as a result of concerted structural change in the 80s loop of the protease. 1073 10

The drug interactions between four human immune deficiency virus (HIV-1) protease inhibitors have been characterized by in-vitro metabolic studies using rat liver microsomal fractions and in-vivo oral administration. In this study, a new HPLC analytical method developed by us was used for the simultaneous determination of saquinavir and nelfinavir in rat plasma and microsomes. The metabolic clearance rates (Vmax/Km) of saquinavir, nelfinavir, and indinavir were 170.9 +/- 10.9, 126.1 +/- 4-4, and 73.0 +/- 2.0 microL min(-1) (mg protein)(-1), respectively. Ritonavir was the strongest inhibitor with inhibition constants (Ki) of 1.64 microM for saquinavir, 0.95 microM for indinavir, and 1.01 microM for nelfinavir. Nelfinavir was the second strongest inhibitor with Ki's of 2.35 microM for saquinavir and 2.14 microM for indinavir. Indinavir was the third strongest inhibitor with Ki's of 2.76 microM for nelfinavir and 3.55 microM for saquinavir. Saquinavir was the weakest inhibitor for the other three HIV- 1 protease inhibitors. After oral co-administration in combination with another HIV-1 protease inhibitor, the AUCs of saquinavir, indinavir, and nelfinavir were significantly increased compared with mono-treatment. The AUCs of saquinavir were increased about 10.1-, 3.1- and 45.9-fold in the presence of indinavir, nelfinavir and ritonavir, respectively. The AUCs of indinavir were increased about 6.8-, 5.9- and 9.4-fold in the presence of nelfinavir, saquinavir and ritonavir, respectively. The AUCs of nelfinavir were increased about 2.2-, 6.6- and 8.5-fold in the presence of indinavir, saquinavir and ritonavir, respectively. The in-vivo effects observed after co-administration of two kinds of HIV-1 protease inhibitor were not always expected from in-vitro data, suggesting the presence of other interaction processes besides metabolism in the liver. These results provide useful information for the treatment of AIDS patients receiving combination therapy with two HIV-1 protease inhibitors.
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PMID:Pharmacokinetic interactions between HIV-1 protease inhibitors in rats: study on combinations of two kinds of HIV-1 protease inhibitors. 1109 68

The vast majority of HIV-1 infections in Africa are caused by the A and C viral subtypes rather than the B subtype prevalent in the United States and Western Europe. Genomic differences between subtypes give rise to sequence variations in the encoded proteins, including the HIV-1 protease. Because some amino acid polymorphisms occur at sites that have been associated with drug resistance in the B subtype, it is important to assess the effectiveness of protease inhibitors that have been developed against different subtypes. Here we report the enzymatic characterization of HIV-1 proteases with sequences found in drug-naive Ugandan adults. The A protease used in these studies differs in seven positions (I13V/E35D/M36I/R41K/R57K/H69K/L89M) in relation to the consensus B subtype protease. Another protease containing a subset of these amino acid polymorphisms (M36I/R41K/H69K/L89M), which are found in subtype C and other HIV subtypes, also was studied. Both proteases were found to have similar catalytic constants, k(cat), as the B subtype. The C subtype protease displayed lower K(m) values against two different substrates resulting in a higher (2.4-fold) catalytic efficiency than the B subtype protease. Indinavir, ritonavir, saquinavir, and nelfinavir inhibit the A and C subtype proteases with 2.5-7-fold and 2-4.5-fold weaker K(i)s than the B subtype. When all factors are taken into consideration it is found that the C subtype protease has the highest vitality (4-11 higher than the B subtype) whereas the A subtype protease exhibits values ranging between 1.5 and 5. These results point to a higher biochemical fitness of the A and C proteases in the presence of existing inhibitors.
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PMID:Catalytic efficiency and vitality of HIV-1 proteases from African viral subtypes. 1135 56

The design, synthesis, and biological evaluation of a series of HIV-1 protease inhibitors [(-)-6, (-)-7, (-)-23, (+)-24] based upon the 3,5,5-trisubstituted pyrrolin-4-one scaffold is described. Use of a monopyrrolinone scaffold leads to inhibitors with improved cellular transport properties relative to the earlier inhibitors based on bispyrrolinones and their peptide counterparts. The most potent inhibitor (-)-7 displayed 13% oral bioavailability in dogs. X-ray structure analysis of the monopyrrolinone compounds cocrystallized with the wild-type HIV-1 protease provided valuable information on the interactions between the inhibitors and the HIV-1 enzyme. In each case, the inhibitors assumed similar orientations for the P2'-P1 substituents, along with an unexpected hydrogen bond of the pyrrolinone NH with Asp225. Interactions with the S2 pocket, however, were not optimal, as illustrated by the inclusion of a water molecule in two of the three inhibitor-enzyme complexes. Efforts to increase affinity by displacing the water molecule with second and third generation inhibitors did not prove successful. Lack of success with this venture is a testament to the difficulty of accurately predicting the many variables that influence and build binding affinity. Comparison of the inhibitor positions in three complexes with that of Indinavir revealed displacements of the protease backbones in the enzyme flap region, accompanied by variations in hydrogen bonding to accommodate the monopyrrolinone ring. The binding orientation of the pyrrolinone-based inhibitors may explain their sustained efficacy against mutant strains of the HIV-1 protease enzyme as compared to Indinavir.
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PMID:Design, synthesis, and biological evaluation of monopyrrolinone-based HIV-1 protease inhibitors. 1272 47

Protease inhibitors in combination with other antiretroviral drugs have been shown to be efficacious in treating human immunodeficiency virus-1 (HIV-1) infection. The side effects of such a treatment usually involve perturbations of fat metabolism and insulin responsiveness. This has led to a number of studies on the adverse effects of these drugs in vitro. The concentrations of various protease inhibitors used in many of these studies were >20 microM. Although some investigators did address the toxicity of protease inhibitors, no overall effort was made to examine this effect during differentiation of fat or muscle. In this study, we assessed the toxicity of HIV-1 protease inhibitors over a range of concentrations (i.e., 0 to 100 microM) in nondifferentiating (e.g., human fibroblasts, 3T3-L1 preadipocytes, and L6 myoblasts) and differentiated cells (e.g., L6 myotubes). The most toxic protease inhibitor in all cell types was Saquinavir (sqv), whereas the least toxic protease inhibitor was Indinavir (idv). Ritonavir (rtv) and Amprenavir (apv) were more toxic than idv but not quite as toxic as sqv. In 3T3-L1 preadipocytes, treatment with sqv, rtv, and apv resulted in toxicity, whereas idv was not toxic even at the highest concentration used. Indinavir was not toxic to L6 myoblasts or L6 myotubes; however, sqv, rtv, and apv caused toxicity in L6 myoblasts. Saquinavir decreased L6 myotube viability in a dose-dependent manner. Human immunodeficiency virus-1 protease inhibitors were shown to be toxic in a variety of cell types. These effects on human fibroblasts and muscle cells have not been reported previously.
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PMID:The effect of human immunodeficiency virus-1 protease inhibitors on the toxicity of a variety of cells. 1456 Nov 12


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