Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0019693 (HIV)
 170,526 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Viral entry is an early stage and specific of the infection in which different viral and cellular targets are accessible to therapeutic treatment. CXCR4 and CCR5 act in this process as coreceptor molecules of HIV for its entry into the host cell. The predominant role played by the CCR5 coreceptor in the transmission and spreading of HIV makes this molecule the target of choice for blocking this mechanism. In the last few years, different specific inhibitors of HIV coreceptors have been generated of which only one, Maraviroc, has been approved for clinical use. The synthetic inhibitors developed act as allosteric antagonists that induce a non-permissive state or configuration of the coreceptor for binding viral envelope-glycoproteins. The CCR5 antagonists act on a wide spectrum of viruses with affinity or tropism for this receptor (virus R5), are absorbed orally and have powerful antiviral activity. However, the optimistic perspective offered by these new molecules has to be moderated due to the possible and expected appearance of viral resistances, on the one hand, and the propagation of viral species with affinity or tropism for the CXCR4 receptor (virus X4). This situation is a reality verified in the first clinical trials with these drugs and they acutely and urgently show the need to have effective and non-toxic CXCR4 inhibitors available to block this alternative viral replication and escape route.
 ...
PMID:[Viral entry as therapeutic target. Current situation of entry inhibitors]. 1913 15

Maraviroc (MVC, Celsentri) is an allosteric and reversible inhibitor of the CCR5 chemokine coreceptor. MVC is the first marketed CCR5 antagonist and the only oral entry inhibitor approved so far for the treatment of HIV infection. It has been approved for adults with previous antiretroviral exposure. MVC exclusively inhibits the replication of R5- tropic HIV-1 variants after binding to the transmembrane CCR5 receptor cavity. MVC is rapidly absorbed following oral administration, and plasma T(max) is achieved within 0.5- 4 hours after a 300 mg dose. Renal clearance is approximately 10-12 L/h. MVC is a substrate of the cytochrome P450 isoenzyme 3A4; therefore dose adjustments are required when co-administrated with other drugs that induce or inhibit CYP3A4. In addition, MVC dose adjustments are advised in patients with renal failure (CLcr <80 ml/min) only if they receive CYP3A4 inhibitors.
 ...
PMID:[Pharmacokinetics, interactions and mechanism of action of maraviroc]. 1913 16

Maraviroc is the first co-receptor antagonist to be approved for use in HIV infected patient. In a phase II trial, in which the drug was administered as a single therapy, the most suitable maintenance dose was 300 mg, once or twice per day. The MOTIVATE double blind, placebo-compared studies, were carried out on patients infected by HIV-1 with R5 tropism and resistant to drugs from three families of retrovirals. Maraviroc two times per day achieved < 50 copies/mL in 45.5% of the patients compared to 16.7% in the placebo group (p < 0.001). The CD4+ lymphocyte count had a mean of 63 cells/mm(3) higher with Maraviroc. The drug was shown to be superior in all patient groups regardless of the baseline viral load, the baseline CD4+ lymphocyte count or the number of accompanying active drugs. In the study on patients infected by HIV with X4/dual/mixed tropism, Maraviroc, was not virologically effective, but did produce a CD4 increase higher than the placebo. Maraviroc was compared with Efavirenz in the study on patients with no previous treatment and with R5-tropic virus. At 48 weeks, the percentage of patients with a viral load of <50 copies/mL was 69.3% in the group that received Efavirenz and 65.3% in the Maraviroc group. In conclusion, Maraviroc has demonstrated its increased efficacy in patients with CCR5-tropic virus and a long history of antiretroviral use and failure, and in patients with no previous treatment.
 ...
PMID:[Maraviroc efficacy in clinical studies on the development of the molecule]. 1913 17

Maraviroc (MVC) is a new antagonist of the CCR5 coreceptor and is the first antiviral compound available that has a cell factor essential for HIV entry as a target. The information available from clinical studies with MVC suggests that the main cause of therapeutic failure is, more than the tropism change, the rapid selection of pre-existing strains with an affinity for CXCR4, not detected by the reference test. A recently developed tropism test with an improved sensitivity will help to detect the minority, but clinically significant, presence of strains that use CXCR4. Evidence of resistance to MVC has been shown in vivo in some patients. The mechanism of this resistance appears to be related to changes in gp120 and mainly in the V3 region which enables the virus to recognise the CCR5-co-receptor bound to the MVC molecule. From a practical point of view, standardised tests are currently unavailable to assess susceptibility to MVC, although in dose-response phenotype tests a maximum percentage inhibition (MPI) < 95% would be indicative of resistance to the compound. Similarly, although some mutations associated with resistance in V3, and other zones of gp120, have been described, this preliminary information suggests different resistance patterns and at the moment, we do not know the canonical mutations to be able to establish genotyping algorithms.
 ...
PMID:[Mechanisms of resistance and failure of treatment with maraviroc]. 1913 19

Maraviroc is a selective and slowly reversible antagonist of the CCR5 co-receptor which has shown to have powerful antiviral activity, in vitro, against a wide range of HIV clinical isolates, including strains multi-resistant to 4 classes of pre-existing antiretroviral drugs. Maraviroc is active against HIV populations that only use the CCR5 coreceptor to enter the cell and has not demonstrated significant activity in the treatment of viral populations that use the CXCR4 co-receptor. The mechanism of action of maraviroc, non-competitive with other antiretroviral drugs, and the absence of crossed resistance with the rest of their families, has led to Maraviroc being a drug available for use in rescue antiretroviral treatment. However, the excellent tolerance of maraviroc compared to the placebo in phase III clinical trials, its safety and its favourable pharmacological interactions profile with other drugs commonly used in HIV infected patients with comorbidity brings to light other scenarios in which Maraviroc could be useful.
 ...
PMID:[At what time and with which combinations should maraviroc be indicated in the new antiretroviral treatment scenario?]. 1913 20

This monograph discusses most important aspects Maraviroc, the development and application perspectives of this drug, as well as main questions raised in its use. Maraviroc is the first CCR5 antagonist approved for treating HIV infection. Its imidazopyridine structure interacts with CCR5 and induces a co-receptor conformation that prevents glycoproteins binding to the viral envelope. It has powerful antiviral activity and acts on a wide spectrum of viruses with affinity for this receptor. This situation means that a tropism test has to be done before treatment to define whether the patient is a carrier of R5 variants. Maraviroc is indicated in HIV infected patients who have received previous antiretroviral treatment. It has a low toxicity and, according to preliminary data, a high genetic barrier. The resistance mechanism is associated with changes in the V3 region which allow the virus to recognise the CCR5 co-receptor bound to the Maraviroc molecule. The main cause of treatment failure is the selection of pre-existing X4 strains not detected by the reference test. Maraviroc can be combined with any other antiretroviral on the market or in clinically advanced development. The indication of Maraviroc in the early phases of the infection is not currently recommended and will depend whether it is shown to be inferior when compared other treatments or a benefit in other pathogenic aspects, such as recovery of CD4 lymphocytes or a reduction in viral reservoirs.
 ...
PMID:[Conclusions and perspectives. Maraviroc]. 1913 22

The advent of HIV-1 resistance to antiretroviral medications, the need for lifelong antiretroviral therapy (ART) for HIV-infected individuals, and the goal of minimizing ART-related adverse effects and toxicity all drive the need for new antiretroviral drugs. Two new classes of antiretroviral medications for HIV treatment, the CCR5 and integrase inhibitors, have recently been approved for use in patients in whom previous HIV treatment regimens have failed. These new agent classes are a welcome addition to other antiretroviral classes, which include nucleoside reverse transcriptase inhibitors, non-nucleoside reverse transcriptase inhibitors, protease inhibitors and fusion inhibitors. Maraviroc is a CCR5 co-receptor antagonist that blocks HIV binding to the CCR5 receptor, which is a CD4 co-receptor necessary for cell entry. It is approved for use in ART-experienced patients with CCR5-tropic HIV, and was found to significantly reduce HIV viral load and increase CD4+ cell count when combined with an optimized background ART regimen (OBR). Treatment failure with maraviroc has been described and is primarily associated with the presence of CXCR4-tropic virus. Vicriviroc is another CCR5 co-receptor antagonist that is in late clinical trials. Raltegravir is the first US FDA-approved HIV-1 integrase inhibitor. It is approved for use in ART-experienced patients and was found to significantly reduce HIV viral load and increase CD4+ cell counts compared with placebo in combination with an OBR. Raltegravir has also been studied in treatment-naive patients and was found to be non-inferior to an efavirenz-based regimen. Elvitegravir is another HIV-1 integrase inhibitor in clinical development. Other new antiretroviral agents in clinical development include PRO140, a monoclonal antibody against CCR5, and bevirimat, a maturation inhibitor that prevents late-stage gag polyprotein processing. A number of other drug targets, such as CCR5 co-receptor agonists, CXCR4 co-receptor antagonists, novel fusion inhibitors, and alternative antiretroviral strategies, such as immune stimulation and gene therapy, are under investigation.
 ...
PMID:Novel targets for antiretroviral therapy: clinical progress to date. 1919 35

Inhibition of the human immunodeficiency virus type 1 (HIV-1) coreceptor is an encouraging new approach to pharmacotherapy against HIV. The HIV-1 strain makes use of either the CCR5 or the CXCR4 coreceptor to gain access into host CD4+ cells. Maraviroc, the first HIV-1 CCR5 coreceptor antagonist, blocks entry of HIV-1. This recently approved drug has demonstrated clinically significant decreases in plasma concentrations of HIV-1 RNA and increases in CD4+ cell counts; however, it is indicated only for use as salvage therapy. Drug resistance is a concern, as is selective pressure on viral coreceptor use, because viral coreceptor targets may switch as disease progresses. In addition, before maraviroc therapy can be started, costly assays are required to determine the host's viral coreceptor tropism. Emerging therapies targeting CXCR4, the other HIV coreceptor, have shown promise in decreasing plasma concentrations of HIV-1 RNA. Long-term studies with both targets are required to explore the critical issues of efficacy and immunologic safety, as the function of these coreceptors is linked to host chemokine pathways.
 ...
PMID:Maraviroc, a CCR5 coreceptor antagonist that blocks entry of human immunodeficiency virus type 1. 1924 48

Maraviroc (Pfizer's UK-427857, Selzentry or Celsentri outside the USA) is the first agent in the new class of oral HIV-1 entry inhibitors to acquire approval by the US Food and Drug Administration and the European Medicine Agency. Considering the mechanism of action, it is expected that this drug will be effective only in a subpopulation of HIV-1-infected people, namely those harbouring the R5 virus. The favourable toxicity profile of the drug has been demonstrated in Phase III clinical trials in treatment-naive (MERIT) and treatment-experienced (MOTIVATE) patients. In the latter population, maraviroc showed a superior antiviral efficacy and immunological activity compared with optimized backbone therapy + placebo. However, in MERIT, a prospective double-blind, randomized trial in treatment-naive patients, maraviroc + zidovudine/lamivudine failed to prove non-inferiority to efavirenz + zidovudine/lamivudine as standard of care regimen in the 48 week intention-to-treat analysis. Using an assay with higher sensitivity for minority CXCR4-using (X4) HIV variants (the enhanced Trofile assay-Monogram), non-inferiority was reached for the maraviroc- versus efavirenz-based combination. These data indicate the important impact of the sensitivity of tropism testing on treatment outcome of maraviroc-containing regimens. This paper discusses both the prospective and retrospective analyses of the MERIT data and highlights the impact of these results on daily practice in HIV care.
 ...
PMID:Maraviroc: perspectives for use in antiretroviral-naive HIV-1-infected patients. 1937 64

Maraviroc, the only CCR5 antagonist HIV inhibitor currently approved, has potent antiviral activity in treatment-experienced individuals infected with CCR5-using HIV-1 (R5 HIV-1). However, recent data from the MOTIVATE trials indicate that R5 HIV-1 can develop resistance to Maraviroc, underscoring the need for additional CCR5 antagonists. The CCR5 antagonist aplaviroc (APL) is active against Maraviroc-resistant viral strains but its clinical development has ended because of dose-related toxicity. Here we demonstrate that reduction of CCR5 density (receptors/cell) with the immunomodulatory drug rapamycin (RAPA) enhances the antiviral activity of APL, allowing lower, non-toxic effective doses. In the presence of RAPA, the concentration of APL required for 90% inhibition of R5 HIV-1 in primary CD4 lymphocytes was reduced by as much as 25-fold. We conclude that low doses of RAPA may reduce the anti-HIV effective dose of APL-derivatives currently in development and thus minimize their potential toxicity. Combinations of RAPA and CCR5 antagonists could provide an effective means to control drug-resistant R5 HIV in patients, most notably those infected with Maraviroc-resistant viruses.
 ...
PMID:Rapamycin enhances aplaviroc anti-HIV activity: implications for the clinical development of novel CCR5 antagonists. 1950 Dec 60


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>