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)

The HIV-1 protease inhibitor ritonavir (ABT-538) undergoes cytochrome P450-mediated biotransformation in human liver microsomes to three major metabolites, Ml, M2 and M11, with wide interindividual variation in the rates of metabolite formation. The structures of these metabolites were determined with the use of electrospray ionization mass spectrometry. Chemical inhibition, metabolic correlation, immunoinhibition and metabolism by microsomes derived from specific CYP cDNA-transfected B-lymphoblastoid cell lines indicated that the CYP3A subfamily of enzymes was the major contributor to the formation of M1 and M11, whereas both CYP3A and CYP2D6 contributed to the formation of M2. None of the typical CYP3A substrates/inhibitors (e.g., ketoconazole, troleandomycin) were able to completely inhibit ritonavir metabolism, even at high concentrations. Ritonavir was found to be a potent inhibitor of CYP3A-mediated biotransformations (nifedipine oxidation, IC50) = 0.07 microM; 17alpha-ethynylestradiol 2-hydroxylation, IC50 = 2 microM; terfenadine hydroxylation, IC50 = 0.14 microM). Ritonavir was also found to be an inhibitor of the reactions mediated by CYP2D6 (IC50 = 2.5 microM) and CYP2C9/10 (IC50 = 8.0 microM). The results of this study indicate the potential for in vivo inhibition of the metabolism by ritonavir of drugs that are CYP3A, CYP2D6 and, to a lesser extent, CYP2C9/10 substrates.
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PMID:Cytochrome P450-mediated metabolism of the HIV-1 protease inhibitor ritonavir (ABT-538) in human liver microsomes. 861 51

HIV-1 protease-inhibitor treatments are associated with a syndrome of peripheral lipodystrophy, central adiposity, breast hypertrophy in women, hyperlipidaemia, and insulin resistance. The catalytic region of HIV-1 protease, to which protease inhibitors bind, has approximately 60% homology to regions within two proteins that regulate lipid metabolism: cytoplasmic retinoic-acid binding protein type 1 (CRABP-1) and low density lipoprotein-receptor-related protein (LRP). We hypothesise that protease inhibitors inhibit CRABP-1-modified, and cytochrome P450 3A-mediated synthesis of cis-9-retinoic acid, a key activator of the retinoid X receptor; and peroxisome proliferator activated receptor type gamma (PPAR-gamma) heterodimer, an adipocyte receptor that regulates peripheral adipocyte differentiation and apoptosis. Protease-inhibitor binding to LRP would impair hepatic chylomicron uptake and triglyceride clearance by the endothelial LRP-lipoprotein lipase complex. The resulting hyperlipidaemia contributes to central fat deposition (and in the breasts in the presence of oestrogen), insulin resistance, and, in susceptible individuals, type 2 diabetes. Understanding the syndrome's pathogenesis should lead to treatment strategies and to the design of protease inhibitors that do not cause this syndrome.
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PMID:Pathogenesis of HIV-1-protease inhibitor-associated peripheral lipodystrophy, hyperlipidaemia, and insulin resistance. 965 87

Human immunodeficiency virus 1 (HIV-1) protease inhibitors have dramatically reduced the morbidity and mortality due to HIV-1 infection. However, most of these antiretrovirals are also potent inhibitors (and occasionally inducers) of hepatic and intestinal cytochrome P450 systems and, therefore, have the potential to alter the elimination of any substance that utilizes these metabolic pathways. We describe a patient infected with HIV-1 who was treated with ritonavir and saquinavir and then experienced a prolonged effect from a small dose of methylenedioxymetamphetamine (MDMA or ecstacy) and a nearly fatal reaction from a small dose of gamma-hydroxybutyrate (GHB). We also discuss the potential for HIV-1 protease inhibitors to alter the metabolism of other abusable prescribed and illicit substances.
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PMID:Life-threatening interactions between HIV-1 protease inhibitors and the illicit drugs MDMA and gamma-hydroxybutyrate. 1052

Inhibitors of the protease of human immunodeficiency virus type 1 (HIV-1) may inhibit cytoplasmic retinoic acid-binding proteins, cytochrome P450 isoforms, as well as P-glycoproteins. These features of the protease inhibitors might enhance the activity of retinoids. To explore this hypothesis, myeloid leukemia cells were cultured with all-trans retinoic acid (ATRA) either alone or in combination with the HIV-1 protease inhibitors indinavir, ritonavir, and saquinavir. Consistent with the hypothesis, the HIV-1 protease inhibitors enhanced the ability of ATRA to inhibit growth and induce differentiation of HL-60 and NB4 myeloid leukemia cells, as measured by expression of CD11b and CD66b cell surface antigens, as well as reduction of nitroblue tetrazolium. Growth of ATRA-resistant UF-1 cells was also inhibited when cultured with the combination of ATRA and indinavir. Moreover, indinavir enhanced the ability of ATRA to induce expression of the myeloid differentiation-related transcription factor C/EBPepsilon messenger RNA in NB4 cells by 9.5-fold. Taken together, the results show that HIV-1 protease inhibitors enhance the antiproliferative and differentiating effects of ATRA on myeloid leukemia cells. An HIV-1 protease inhibitor might be a useful adjuvant with ATRA for patients with acute promyelocytic leukemia and possibly retinoid-resistant cancers.
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PMID:HIV-1 protease inhibitors decrease proliferation and induce differentiation of human myelocytic leukemia cells. 1107 54

The HIV-1 protease inhibitor (PI) saquinavir is available as a soft gelatin capsule (SGC) formulation. At the recommended dosage of saquinavir SGC (1200mg 3 times daily), this formulation provides around 8-fold greater exposure than the established hard gelatin capsule (HGC) formulation at the recommended dosage of 600mg 3 times daily. As with the HGC formulation, the most common adverse events seen with saquinavir SGC are gastrointestinal symptoms (e.g. diarrhoea, abdominal discomfort and nausea). Some of these may occur with a slightly higher frequency with the SGC than with the HGC formulation. Saquinavir SGC has only a minimal effect on nonfasting serum lipid and cholesterol levels. Like other PIs, saquinavir is metabolised by the cytochrome P450 (CYP) 3A4 isoenzyme and is susceptible to interactions with inducers (e.g. rifabutin and rifampicin) and inhibitors (e.g. clarithromycin and ketoconazole) of this enzyme. Ritonavir, nelfinavir, indinavir and delavirdine, all CYP3A4 inhibitors, greatly increase saquinavir plasma concentrations and the therapeutic implications of these interactions continue to be evaluated. While saquinavir is the least potent CYP 3A inhibitor among the PIs, several drugs (notably terfenadine, astemizole and cisapride) should not be given in combination with saquinavir. Therefore, although the SGC formulation enhances saquinavir exposure, it has a similar safety profile to the HGC formulation.
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PMID:Saquinavir soft gelatin capsule: a comparative safety review. 1134 24

Ritonavir is an HIV-1 protease inhibitor that is often used to improve the systemic availability of concurrently administered protease inhibitors by impairing their metabolism through cytochrome P450 (CYP) 3A4. Pharmacodynamic relationships between plasma ritonavir concentrations and efficacy and toxicity have also been described. To date, published high-performance liquid chromatographic (HPLC) methods for the determination of ritonavir in human plasma are often complex, requiring the use of a buffered mobile phase that contains amine-modifiers (i.e. diethylamine, triethylamine). In the method herein, ritonavir was precipitated with acetonitrile plus barium hydroxide and zinc sulphate. Chromatographic separation was accomplished using a C-18 base-deactivated (250 x 4.6 mm I.D., 5 atm particle size) analytic column with a mobile phase composed of acetonitrile:water (52:48, v/v). Quantification was performed at 239 nm. Calibration curves were linear from 0.5-25 microg/ml (R2 > 0.999); percent errors, as a measure of accuracy, were < 12.7%. Intra- and inter-assay relative standard deviations (RSD) were below 12.8%. This method provides a rapid and simple means for the accurate and precise analysis of ritonavir in human plasma. Furthermore, the assay requires neither the use of a buffered mobile phase adjusted to a specific pH, nor the addition of amine modifiers. This method has been successfully used to determine plasma ritonavir concentrations in drug interaction studies.
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PMID:Rapid and sensitive high-performance liquid chromatographic method for the determination of ritonavir in human plasma. 1156 87

The use of highly active antiretroviral therapy, the combination of at least three different antiretroviral drugs for the treatment of HIV-1 infection, has greatly improved the prognosis for HIV-1-infected patients. The efficacy of a combination of a protease inhibitor (PI) plus two nucleoside analogue reverse transcriptase inhibitors has been well established over a period of up to 3 years. However, virological treatment failure has been reported in 40-60% of unselected patients within 1 year after initiation of a PI-containing regimen. This observation may, at least in part, be attributed to the poor pharmacokinetic characteristics of the PIs. Given as a single agent the PIs have several pharmacokinetic limitations; relatively short plasma-elimination half-lives and a modest and variable oral bioavailability, which is, for some of the PIs, influenced by food. To overcome these suboptimal pharmacokinetics, high doses (requiring large numbers of pills) must be ingested, often with food restrictions, which complicates patient adherence to the prescribed regimen. Positive drug-drug interactions increase the exposure to the PIs, allowing administration of lower doses at reduced dosing frequencies with less dietary restrictions. In addition to increasing the potency of an antiretroviral regimen, combinations of PIs may enhance patient adherence, both of which will contribute to a more durable suppression of viral replication. The favourable pharmacokinetics of PIs in combination are a result of interactions through cytochrome P450 3A4 (CYP3A4) isoenzymes and, possibly, the multi-drug transporting P-glycoprotein (P-gp). Antiretroviral synergy between PIs and non-overlapping primary resistance patterns in the HIV-1 protease genome may further enhance the antiretroviral potency and durability of combinations of PIs. Many combinations contain ritonavir because this PI has the most pronounced inhibiting effects on CYP3A4. The combination of saquinavir and ritonavir, both in a dose of 400 mg twice-a-day, is the most studied double PI combination, with clinical experience extending over 3 years. Combination of a PI with a low dose of ritonavir (< or = 400 mg/day), only to boost its pharmacokinetic properties, seems an attractive option for patients who cannot tolerate higher doses of ritonavir. A recently introduced PI, lopinavir, has been co-formulated with low-dose ritonavir, which allows for a convenient three-capsules, twice-a-day dosing regimen. In an attempt to prolong suppression of viral replication combinations of PIs are becoming increasingly popular. However, further clinical studies are needed to identify the optimal combinations for treatment of antiretroviral naive and experienced HIV-1-infected patients. This review covers combinations of saquinavir, indinavir, nelfinavir, amprenavir and lopinavir with different doses of ritonavir, as well as the combinations of saquinavir and indinavir with nelfinavir.
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PMID:Combination of protease inhibitors for the treatment of HIV-1-infected patients: a review of pharmacokinetics and clinical experience. 1187 3

Atazanavir is a novel azapeptide protease inhibitor with high specificity for, and activity against, HIV-1 protease. The resistance profile of atazanavir is distinct, with an I50 L protease substitution appearing to be the signature mutation. Atazanavir was not associated with increases in total cholesterol, low density lipoprotein-cholesterol or triglyceride levels after 108 weeks. Atazanavir has a pharmacokinetic profile that allows for once-daily oral administration. It is a moderate inhibitor of hepatic cytochrome P450 enzymes and interacts with several drugs. In combination with stavudine plus didanosine, atazanavir 200, 400 or 500 mg once daily produced a rapid and sustained reduction from baseline in viral load of 2.57, 2.42 and 2.53 log(10) copies/mL, respectively, in treatment-naive patients after 48 weeks, compared with a decrease of 2.33 log(10) copies/mL with nelfinavir 750 mg three times daily. Nausea was the most clinically relevant adverse event reported in patients receiving atazanavir-based regimens.
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PMID:Atazanavir. 1290 86

We previously showed that HIV-1 protease inhibitors (PIs) slowed the proliferation of human myeloid leukemia cells and enhanced their differentiation in the presence of all-trans-retinoic acid. In this study, we found that PIs, including ritonavir, saquinavir, and indinavir, inhibited the growth of DU145 and PC-3 androgen-independent prostate cancer cells as measured by a clonal proliferation assay. Recent studies showed that ritonavir inhibited cytochrome P450 3A4 enzyme (CYP3A4) in liver microsomes. The CYP3A4 is involved in drug metabolism and acquisition of drug resistance. To clarify the drug interaction between ritonavir and other anticancer drugs, we cultured DU145 cells with docetaxel either alone or in combination with ritonavir. Ritonavir enhanced the antiproliferative and proapoptotic effects of docetaxel in the hormonally independent DU145 prostate cancer cells in vitro as measured by the clonogenic soft agar assay and detection of the activated form of caspase-3 and cleavage of poly(ADP-ribose) polymerase using Western blot analysis. Real-time PCR showed that docetaxel induced the expression of CYP3A4 at the transcriptional level, and ritonavir (10(-5) mol/L) completely blocked this induction. An ELISA-based assay also showed that ritonavir inhibited DNA binding activity of nuclear factor kappaB (NFkappaB) in DU145 cells, which is a contributor to drug resistance in cancer cells. Furthermore, combination treatment of docetaxel and ritonavir dramatically inhibited the growth of DU145 cells present as tumor xenografts in BNX nude mice compared with either drug alone. Importantly, docetaxel induced expression of CYP3A4 in DU145 xenografts, and ritonavir completely blocked this induction. Ritonavir also inhibited NFkappaB DNA binding activity in DU145 xenografts. Extensive histologic analyses of the liver, spleen, kidneys, bone marrow, skin, and subcutaneous fat pads from these mice showed no abnormalities. In summary, combination therapy of ritonavir and anticancer drugs holds promise for the treatment of individuals with advanced, drug resistant cancers.
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PMID:HIV-1 protease inhibitor, ritonavir: a potent inhibitor of CYP3A4, enhanced the anticancer effects of docetaxel in androgen-independent prostate cancer cells in vitro and in vivo. 1549 66

The HIV-1 protease inhibitors (PIs) are widely used in combination antiretroviral therapy for the management of HIV-1 infection. Certain characteristics of the PIs, in particular their metabolism being mainly via the cytochrome P450 isoenzyme group and their gastric absorption being pH dependent, make them prone to clinically significant drug interactions with other antiretrovirals, concomitant medication and complementary treatments. Owing to the nature of the disease, individuals with HIV are frequently prescribed complex treatment regimens (both for the management of intolerance, toxicity and viral resistance to antiretroviral therapy, and in the management of co-morbid states) that may interact with PI therapy. For many of these potential interactions, few data are available. This review will focus on the current use of PIs, highlighting some important management issues encountered with common pharmacokinetic interactions seen in clinical practice.
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PMID:The management of HIV-1 protease inhibitor pharmacokinetic interactions. 1594 77


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