Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.7.49 (reverse transcriptase)
31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Efavirenz (EFV, Sustiva, Stocrin, DMP-266, L-743,726) is a potent and selective non-nucleoside inhibitor of HIV-1 reverse transcriptase. Pharmacokinetics of EFV was studied in rats and monkeys, the safety assessment species. In rats, after 2 and 5 mg/kg i.v. administrations, the mean CLp, Vdss, and T1/2 were 67 ml/min/kg, 5.0 liters/kg, and 1 h, respectively. EFV was metabolized completely, and the products were excreted almost exclusively via bile. At the higher dose of 15 mg/kg, the CLp was reduced by 36%, implying saturation of metabolism processes. A similar phenomenon occurred in monkeys, where the CLp declined by 60% as the i.v. dose was increased from 5 to 15 mg/kg. After oral dosing, the bioavailability of EFV in rats (10 mg/kg) and monkeys (2 mg/kg) was 16% and 42%, respectively. Higher doses in both species led to disproportionate increases in the AUC and higher Tmax values, suggesting saturation of metabolism and/or prolongation of absorption. The delay in Tmax was more pronounced in monkeys where the plasma concentrations reached plateaus and were sustained for 4 to 20 h. In rats, the prolongation of absorption was due to delayed gastric emptying as demonstrated by >10-fold slower transit of [14C]polyethylene glycol through the stomach of EFV-pretreated animals. The delayed gastric emptying in monkeys also was observed when the animals dosed at 160 mg/kg exhibited emesis, 8 h postdose, which was found to contain a substantial portion of the dose. These results demonstrated that in rats and monkeys, both delayed gastric emptying and saturation of metabolic processes played significant roles in the nonlinear pharmacokinetics of EFV.
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PMID:Nonlinear pharmacokinetics of efavirenz (DMP-266), a potent HIV-1 reverse transcriptase inhibitor, in rats and monkeys. 988 7

Efavirenz (Sustiva) is a potent and specific inhibitor of the HIV-1 reverse transcriptase and is approved for the treatment of HIV infection. The metabolism of efavirenz in different species has been described previously. Efavirenz is primarily metabolized in rats to the glucuronide conjugate of 8-OH efavirenz. Electrospray ionization-liquid chromatography/mass spectrometry analyses of bile samples from rats dosed with either efavirenz or with 8-OH efavirenz revealed three polar metabolites, M9, M12, and M13, with pseudomolecular ions [M-H](-) at m/z 733, 602, and 749, respectively. The characteristic mass spectral fragmentation patterns obtained for metabolites M9 and M13 suggested that these were glutathione-sulfate diconjugates, and the presence of a glutathione moiety in metabolite M9 was confirmed by liquid chromatograpy/nuclear magnetic resonance (NMR) analysis of bile extracts. Metabolite M12 was characterized by liquid chromatography/mass spectrometry as a glucuronide-sulfate diconjugate. Unambiguous structures of M9, M12, and M13 were obtained from one-dimensional proton and carbon NMR as well as proton-proton (correlated spectroscopy, two-dimensional shift correlation), proton-carbon heteronuclear multiple quantum correlation, and long-range proton-carbon (heteronuclear multiple bond correlation) correlated two-dimensional NMR analyses of metabolites isolated from rat bile. The mass spectral and NMR analyses of M10, which was isolated from rat urine, suggested a cysteinylglycine-sulfate diconjugate. The isolation of these polar metabolites for further characterization by NMR was aided by mass spectral analyses of HPLC fractions and solid phase extraction extracts during the isolation steps. The complete characterization of these novel diconjugates demonstrates that further phase II metabolism of polar conjugates such as sulfates could take place in vivo.
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PMID:Liquid chromatography/mass spectrometry and high-field nuclear magnetic resonance characterization of novel mixed diconjugates of the non-nucleoside human immunodeficiency virus-1 reverse transcriptase inhibitor, efavirenz. 1046 Aug 5

Efavirenz (Sustiva, Fig. 1) is a potent and specific inhibitor of HIV-1 reverse transcriptase approved for the treatment of HIV infection. To examine the potential differences in the metabolism among species, liquid chromatography/mass spectrometry profiles of efavirenz metabolites in urine of rats, guinea pigs, hamsters, cynomolgus monkeys, and humans were obtained and compared. The metabolites of efavirenz were isolated, and structures were determined unequivocally by mass spectral and NMR analyses. Efavirenz was metabolized extensively by all the species as evidenced by the excretion of none or trace quantities of parent compound in urine. Significant species differences in the metabolism of efavirenz were observed. The major metabolite excreted in the urine of all species was the O-glucuronide conjugate (M1) of the 8-hydroxylated metabolite. Efavirenz was also metabolized by direct conjugation with glucuronic acid, forming the N-glucuronide (M2) in all five species. The sulfate conjugate of 8-OH efavirenz (M3) was found in the urine of rats and cynomolgus monkeys but not in humans. In addition to the aromatic ring-hydroxylated products, metabolites with a hydroxylated cyclopropane ring (at C14) were also isolated. GSH-related products of efavirenz were identified in rats and guinea pigs. The cysteinylglycine adduct (M10), formed from the GSH adduct (M9), was found in significant quantities in only rat and guinea pig urine and was not detected in other species. In vitro metabolism studies were conducted to show that the GSH adduct was produced from the cyclopropanol intermediate (M11) in the presence of only rat liver and kidney subcellular fractions and was not formed by similar preparations from humans or cynomolgus monkeys. These studies indicated the existence of a specific glutathione-S-transferase in rats capable of metabolizing the cyclopropanol metabolite (M11) to the GSH adduct, M9. The biotransformation pathways of efavirenz in different species were proposed based on some of the in vitro results.
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PMID:Identification and characterization of efavirenz metabolites by liquid chromatography/mass spectrometry and high field NMR: species differences in the metabolism of efavirenz. 1053 18

Accumulating data have brought the nonnucleoside reverse transcriptase (RT) inhibitors (NNRTIs) into the forefront of antiretroviral therapy. Among the emerging compounds in this class, a particularly attractive one is efavirenz (Sustiva), recently approved for clinical use by the U.S. Food and Drug Administration. In the present study, the equilibrium dissociation constants for efavirenz binding to the different catalytic forms of human immunodeficiency virus type 1 RT as well as the association and dissociation rates have been determined using a steady-state kinetic approach. In addition, the same enzymological analysis has been extended to the thio-substituted analog, sefavirenz, which showed comparable activity in vitro against RT. Both compounds have been found to act as purely uncompetitive inhibitors at low drug concentrations (5 to 50 nM) and as mixed noncompetitive inhibitors at higher doses (50 to 500 nM). This behavior can be interpreted in terms of the relative affinities for the different catalytic forms of the enzyme. Both efavirenz and sefavirenz showed increasing affinities for the different forms of RT in the following order: free enzyme < (i.e., bound with lower affinity) binary RT-template-primer (TP) complex < ternary RT-TP-deoxynucleoside triphosphate (dNTP) complex. The rate of binding of the two inhibitors to the different enzyme-substrate complexes was well below the diffusion limit (on the order of 10(4) M(-1) s(-1)); however, both inhibitors, when bound to the ternary RT-TP-dNTP complex, showed very low dissociation rates, on the order of 10(-4) s(-1) for both compounds, typical of tightly binding inhibitors. Thus, efavirenz and its thio-substituted derivative sefavirenz appear to be peculiar in their mechanism of action, being selective tightly binding inhibitors of the ternary RT-TP-dNTP complex. Efavirenz is the first clinically approved NNRTI to show this property.
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PMID:Selective interaction of the human immunodeficiency virus type 1 reverse transcriptase nonnucleoside inhibitor efavirenz and its thio-substituted analog with different enzyme-substrate complexes. 1077 Jul 50

DuPont Merck's non-nucleoside reverse transcriptase inhibitor DMP 266 (called Sustiva or efavirenz) will be available through an expanded access program starting in October 1997. A filing for Food and Drug Administration (FDA) marketing approval is expected in March 1998. Volunteers must have CD4 counts lower than 50 in the last 3 months and be failing current treatment regimens. DMP 266 has shown effectiveness in viral suppression when combined with indinavir. Two new trials are currently enrolling for combination therapy using DMP 266 with AZT/3TC. Contact information is provided for further details.
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PMID:DMP 266 now available. 1136 51

Gilead Sciences will offer an expanded access program for its anti-HIV agent, adefovir (Preveon). Prospective enrollees must have CD4 counts less than 50, a viral load of over 30,000 copies/ml by PCR within the past 2 months, and failed at least two nucleoside analogs and one protease inhibitor. Because adefovir has extremely modest activity, it can only function as an adjunct to other potent drug combinations. There is concern that the eligibility requirements will be problematic. DuPont Merck's non-nucleoside reverse transcriptase inhibitor Sustiva is undergoing participant registration for its expanded access program. Participants must have CD4 counts less than 50 but may have any viral load level. Glaxo's expanded access program for abacavir (1592U89) is an open-label trial with eligibility being CD4 counts less than 100. Glaxo has also opened an expanded access program for patients with moderate to severe AIDS dementia.
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PMID:Three drugs now in expanded access. 1136 20

DuPont Merck is opening an expanded access program for efavirenz (Sustiva), a non-nucleoside reverse transcriptase inhibitor (NNRTI). Efavirenz (formerly called DMP-266), the most potent NNRTI to date, is taken only once a day. To participate, patients must be failing therapy or be intolerant of current therapy. The patients are required to take the drug with another anti-HIV drug that they have never taken. Contact information for efavirenz studies, including a pediatric trial, is provided.
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PMID:DMP 266 (Sustiva) expanded access. 1136 50

Sustiva (DMP 266 or efavirenz) has been available on an expanded access program since October 1. Sustiva is a non-nucleoside reverse transcriptase inhibitor, has fewer side effects than other drugs of its class, and is taken once a day at bedtime. Criteria for the program are T4 counts under 50 in patients whose current therapy is not working. Adefovir dipivoxil (bis-POM PMEA or Preveon) is a nucleotide analog that is also available through an expanded access program. Adefovir's properties make it less vulnerable to resistance. It is not as potent as other drugs of the same class; however, its effect seems to last longer. It is also effective against some herpesviruses and hepatitis B. Contact information is provided for both programs.
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PMID:Expanded access programs. 1136 31

Merck Pharmaceuticals has relaxed the criteria for expanded access for efavirenz (Sustiva or DMP-266). Under the new guidelines, patients who have ever had a CD4 count below 400 can now participate; earlier guidelines limited the program to those with counts below 50 within the last 90 days. European entry criteria will change shortly. Efavirenz must be used in conjunction with another antiretroviral that the patient has not taken previously. The drug is not recommended for use as monotherapy, and patients who have failed on non-nucleoside reverse transcriptase inhibitors are less likely to benefit from Sustiva because of a common mutation. Contact information is given for enrolling in the program.
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PMID:Efavirenz (Sustiva) expanded access now to 400 CD4. 1136 52

Dupont Merck announced an expanded access program for Efavirenz (Sustiva, DMP 266). The non-nucleoside reverse transcriptase inhibitor is taken just once a day, and 88 percent of people taking it in combination with indinavir achieved undetectable viral load. The program is open to people with CD4 counts below 400 who have no other viable treatment options. A contact telephone number is provided for further information.
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PMID:Efavirenz expanded access. 1136 75


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