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)

A phase I/II dose-ranging open-label 28-day monotherapy study of the safety, pharmacokinetics, and antiviral activity of nelfinavir mesylate (Viracept), an inhibitor of human immunodeficiency virus (HIV)-1 protease, was done in 65 HIV-1-infected subjects. After 28 days, 54 responding subjects entered an open-label extension that allowed for the addition of nucleoside inhibitors of reverse transcriptase and dose escalation to maintain durability. The drug was well-tolerated and demonstrated robust antiviral activity, with demonstrable superiority of the 750 mg and 1000 mg three times daily regimens. Thirty subjects who continued to receive therapy at 12 months attained a persistent 1.6 log10 reduction in HIV RNA, accompanied by a mean increase in CD4 cells of 180-200/mm3. Studies of viral genotype and phenotype after virus rebound revealed that the initial active site mutation allowing for nelfinavir resistance is mediated by a unique amino acid substitution in the HIV-1 protease D30N, which does not confer in vitro phenotypic cross-resistance to the currently available protease inhibitors.
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PMID:A preliminary evaluation of nelfinavir mesylate, an inhibitor of human immunodeficiency virus (HIV)-1 protease, to treat HIV infection. 960 30

Nelfinavir mesylate (Viracept, formally AG1343) is a potent and orally bioavailable human immunodeficiency virus (HIV) type 1 (HIV-1) protease inhibitor (K(i) = 2 nM) and is being widely prescribed in combination with HIV reverse transcriptase inhibitors for the treatment of HIV infection. The current studies evaluated the presence of metabolites circulating in plasma following the oral administration of nelfinavir to healthy volunteers and HIV-infected patients, as well as the levels in plasma and antiviral activities of these metabolites. The results showed that the parent drug was the major circulating chemical species, followed in decreasing abundance by its hydroxy-t-butylamide metabolite (M8) and 3'-methoxy-4'-hydroxynelfinavir (M1). Antiviral assays with HIV-1 strain RF-infected CEM-SS cells showed that the 50% effective concentrations (EC50) of nelfinavir, M8, and M1 were 30, 34, and 151 nM, respectively, and that the corresponding EC50 against another HIV-1 strain, IIIB, in MT-2 cells were 60, 86, and 653 nM. Therefore, apparently similar in vitro antiviral activities were demonstrated for nelfinavir and M8, whereas an approximately 5- to 11-fold-lower level of antiviral activity was observed for M1. The active metabolite, M8, showed a degree of binding to human plasma proteins similar to that of nelfinavir (ca. 98%). Concentrations in plasma of nelfinavir and its metabolites in 10 HIV-positive patients receiving nelfinavir therapy (750 mg three times per day) were determined by a liquid chromatography tandem mass spectrometry assay. At steady state (day 28), the mean plasma nelfinavir concentrations ranged from 1.73 to 4.96 microM and the M8 concentrations ranged from 0.55 to 1.96 microM, whereas the M1 concentrations were low and ranged from 0.09 to 0.19 microM. In conclusion, the findings from the current studies suggest that, in humans, nelfinavir forms an active metabolite circulating at appreciable levels in plasma. The active metabolite M8 may account for some of the antiviral activity associated with nelfinavir in the treatment of HIV disease.
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PMID:Circulating metabolites of the human immunodeficiency virus protease inhibitor nelfinavir in humans: structural identification, levels in plasma, and antiviral activities. 1125 19

Non-nucleoside reverse transcriptase inhibitors (NNRTIs) are the latest drugs used to treat HIV infection. Three NNRTIs are introduced: Viramune (nevirapine), Rescriptor (delavirdine), and Viracept (nelfinavir). Recommended doses, rates of absorption, side effects, distribution throughout the body, clinical studies, reactions with other drugs, and how the drugs are metabolized are given. A list of agents that may inhibit the effect of Rescriptor and Viracept, such as antihistamines, antibiotics and anti-convulsions, is presented.
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PMID:[New combination medications]. 1136 1

While it appears that protease inhibitors in combination therapies are saving lives, questions continue: (1) which combinations of protease inhibitors and other antiretroviral agents are most effective in restoring immune function, (2) how these combinations can be used most effectively, and (3) what is the best time to start using them? An evaluation is presented on the immunological value of specific drug cocktail combinations and a comparison of the best and worst drug combinations and the reasons for this assessment. It indicates that Norvir is the most effective of all four protease inhibitors in preventing opportunistic infections, lymphomas, and cancers. D4T and 3TC are the safest and most effective of the nucleosides for preventing or remitting opportunistic infections when used with protease inhibitors. Rescriptor is the most therapeutic of the two non-nucleoside reverse transcriptase inhibitors in increasing absorption of protease inhibitors. The best drug combination therapies are listed as follows: Norvir plus Rescriptor; Norvir plus D4T; Norvir plus 3TC; Norvir, Rescriptor, and D4T; Norvir, Rescriptor, and 3TC; Norvir, D4T, and 3TC; and Crixivan or Viracept plus Rescriptor plus either D4T or 3TC. The worst drug combination therapies are listed as follows: AZT plus ddI (used in combination with a protease inhibitor); AZT or ddI or Combivir (used in combinations with a protease inhibitor); and any two protease inhibitors used together in any person with active hepatitis or elevated liver enzymes or impaired kidney function.
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PMID:An evaluation of drug cocktail combinations for their immunological value in preventing/remitting opportunistic infections. 1136 16

The 38th Interscience Conference on Antimicrobial Agents and Chemotherapy featured information on new antiretroviral treatments, changes in dosing, and new vaccine information. Adefovir dipivoxil (Preveon) is a new nucleoside reverse transcriptase inhibitor that is administered once daily. A study of adefovir dipivoxil is described and the side effects are detailed. A clinical trial of the protease inhibitor Nelfinavir (Viracept) has shown that dosing twice a day may be as effective as the currently prescribed three times a day. Since lower dosing tends to increase a patient's adherence to treatment, it may have a long-term positive effect on treating HIV. Other drug treatments and possible changes in dosing are presented. A pneumococcal vaccine study is described, and it was found that the vaccine did not lead to an increase in viral load. Immunization against Pneumococcus is suggested for all adults who are HIV-infected.
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PMID:Antimicrobial agents and chemotherapy: highlights of the 38th Interscience Conference. 1136 34

Four protease inhibitors are compared: Saquinavir (Invirase, Fortovase), Indinavir (Crixivan), Ritonavir (Norvir), and Nelfinavir (Viracept). Key questions are answered on how dosages change when combined with nucleoside reverse transcriptase inhibitors (NRTIs), non-nucleoside reverse transcriptase inhibitors (NNRTIs), and other protease inhibitors. Information on administration and storage and the impact of each drug on disease development are reviewed. Drug interactions between protease inhibitors and other HIV drugs and non-HIV medications are described. Side effects are also discussed. Pediatric use is addressed, including suggested dosages. Contact information for each manufacturer is provided, along with approximate annual price for treatment.
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PMID:Protease inhibitors at a glance.... 1136 98

Agouron Pharmaceuticals trial results suggest additional treatment options for people taking or considering taking Viracept in combination with other anti-HIV drugs. The clinical test results with Viracept and other drugs are presented. Viracept was tested for safety and efficacy with Fortovase (saquinavir soft gel), Norvir (ritonavir), Crixivan (indinavir), 1592 (abacavir), and non-nucleoside reverse transcriptase inhibitors.
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PMID:Protease inhibitor combos. 1136 48

Antiretroviral therapy for human immunodeficiency virus (HIV) infection includes treatment with both reverse transcriptase inhibitors and protease inhibitors, which markedly suppress viral replication and circulating HIV RNA levels. Cytochrome P450 (P450) enzymes in human liver, chiefly CYP3A4, play a pivotal role in protease inhibitor biotransformation, converting these agents to largely inactive metabolites. However, the protease inhibitor nelfinavir (Viracept) is metabolized mainly to nelfinavir hydroxy-t-butylamide (M8), which exhibits potent antiviral activity, and to other minor products (termed M1 and M3) that are inactive. Since indirect evidence suggests that CYP2C19 underlies M8 formation, we examined the role of this inducible, polymorphic P450 enzyme in nelfinavir t-butylamide hydroxylation by human liver. Rates of microsomal M8 formation were 50.6 +/- 28.3 pmol of product formed/min/nmol P450 (n = 5 subjects), whereas kinetic analysis of the reaction revealed a KM of 21.6 microM and a Vmax of 24.6 pmol/min/nmol P450. In reconstituted systems, CYP2C19 catalyzed nelfinavir t-butylamide hydroxylation at a turnover rate of 2.2 min(-1), whereas CYP2C9, CYP2C8, and CYP3A4 were inactive toward nelfinavir. Polyclonal anti-CYP2C9 (cross-reactive with CYP2C19) and monoclonal anti-CYP2C19 completely inhibited microsomal M8 production, whereas monoclonal CYP2C9 and polyclonal CYP3A4 antibodies were without effect. Similarly, the CYP2C19 substrate omeprazole strongly inhibited (75%) hepatic nelfinavir t-butylamide hydroxylation at a concentration of only 12.5 microM. Our study shows that CYP2C19 underlies formation in human liver of M8, a bioactive nelfinavir metabolite. The inducibility of CYP2C19 by agents (e.g., rifampicin) often taken concurrently with nelfinavir, together with this P450's known polymorphic nature, may thus be important determinants of nelfinavir's antiviral potency.
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PMID:Conversion of the HIV protease inhibitor nelfinavir to a bioactive metabolite by human liver CYP2C19. 1544 16

Nelfinavir (Viracept) is an orally administered protease inhibitor. In combination with other antiretroviral drugs (usually nucleoside reverse transcriptase inhibitors [NRTIs]), nelfinavir produces substantial and sustained reductions in viral load in patients with HIV infection. Nelfinavir may be used in the treatment of adults, adolescents and children aged >or=2 years with HIV infection. It can also be used in pregnancy. Resistance to nelfinavir may develop, but the most common mutation (D30N, appearing mainly in HIV-1 subtype B) does not confer resistance to other protease inhibitors, thereby conserving these agents for later use. Although less effective than lopinavir/ritonavir, the preferred first-line treatment in US guidelines, nelfinavir is positioned as an alternative agent for the treatment of adults and adolescents with HIV infection and is an option for those unable to tolerate other protease inhibitors. Nelfinavir also has a role in the management of pregnant patients as well as paediatric patients with HIV infection.
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PMID:Nelfinavir: a review of its use in the management of HIV infection. 1622 78