By G. Dennis. New Jersey City University.
The level of viral load on ART is the best predictor of subsequent virological failure; the risk for failure starts to increase at levels between 100 and 300 copies/ml (Nettles 2005 buy 40 mg levitra extra dosage visa, Delaguerre 2009 purchase 40mg levitra extra dosage, Garcia-Gasco 2008) and is highest for any drug class at 1000 to 10,000 copies/ml (Prosperi 2011). The rapid development of resistant variants is due to the high turnover of HIV – in an untreated patient approximately 10 million new viral particles are produced every day (Perelson 1996) – and the exceptionally high error rate of HIV reverse transcriptase. The latter leads to a high mutation rate and constant production of new viral strains, even in the absence of treatment. In the presence of antiretroviral drugs, the development of HIV-1 resistance depends on the selection of resistance- associated mutations (RAMs). If a virus has acquired one or more RAMs leading to reduced drug sensitivity, the mutant virus attains a replication advantage in comparison to wild-type virus when exposed to drugs (Drake 1993). The develop- ment of resistant viral strains is one of the main reasons for virological failure of antiretroviral therapy. However, with the strategic use of the newer drug classes, effective regimens are available even in salvage situations. The discussion about genotypic resistance and viral tropism in this chapter focuses on the methods of resistance and tropism testing, on mutation patterns emerging with ART use, their interpretations and clinical relevance. Most data are derived from patients with subtype B viruses, representing the main subtype in North America, Australia and Europe, but only approximately 10% of the global HIV-1 population. Non-B subtypes have increasingly been investigated, some exhibiting different resist- ance pathways and patterns (Snoeck 2006). Assays for resistance testing There are two established assays for measuring resistance or sensitivity of HIV to specific antiretroviral drugs – the genotypic and the phenotypic resistance tests (Wilson 2003). Genotypic resistance measurements should be distinguished between conventional (population-based) and ultrasensitive sequencing methods. The conventional genotypic assay accredited by the FDA is: • ViroSeq (Abbott Molecular/Applera Corp. Conventional (population-based) genotypic tests can only detect viral mutants when these comprise at least 15-20% of the total virus population. Patients with a low or non-detectable viral load may benefit from sequencing proviral DNA. Concordance of resistance data derived from viral RNA or proviral DNA sequencing is >80% (Boukli 2015, Ferrè 2015). The gold standard for resistance testing in viremic patients, however, continues to use HIV RNA of free virions in EDTA plasma, since resistant viruses may not necessarily be detectable in proviral DNA (Boukli 2015, De La Cruz 2015). Additionally, a large proportion of viruses from proviral DNA is unable to replicate (Ferre 2015). HIV Resistance and Viral Tropism Testing 301 Minority variants can be analyzed by elaborate ultrasensitive molecular biological methods (allele-specific real-time PCR, single genome sequencing) with limits of detection between 0. Ultrasensitive sequencing systems like GS FLX (Roche/454 Life Sciences), HiScanSQ (Illumina) and SOLiD (Life Technologies) are currently used for research purposes. With the availability of devices that are able to analyze smaller series at less cost, such as Ion Torrent PGM (Life Technologies) or MiSeq (Illumina), this next-generation technology can become used for routine diagnostics. Prior to general use, analysis and interpretation of test results and the significance in particular of minor variants must be clearly defined and routinely applicable. The clinical relevance of minority populations remains controversial although there is evidence for minor variants with NNRTI mutations (Li 2011). Recent data show that the next-generation sequencing (NGS) results for NNRTIs continue to require cautious interpretation. In a follow-up investigation of the STaR Study (TDF/FTC plus efavirenz or rilpivirine), in which retained baseline samples were reanalyzed by NGS for minor resistant viral populations, these were not in concor- dance with treatment success (Porter 2015). Phenotypic resistance tests are expensive and time consuming. While the cost of genotyping ranges anywhere from 260 to 400 €, depending on the assay and labo- ratory used, phenotyping costs at least double that. Examples for commercially available phenotypic resistance tests are: • PhenoSense HIV (Monogram Biosciences) • PhenoTecT™ (InPheno) • Phenoscript™ (VIRalliance) • Antivirogram (developed by Virco Lab, is no longer available for routine clinical use, only for research and drug discovery) Depending on the method and on the laboratory, 100–1,000 copies/ml are required for detection of resistance. Tables 1 and 2 show the advantages and disadvantages of phenotypic and genotypic resistance analyses. Table 1: Advantages and disadvantages of phenotypic resistance analysis Phenotypic resistance analysis Advantages Disadvantages • Direct measure of drug susceptibility • Detection of viral mutants only possible when • Measure of drug susceptibility feasible comprising ≥20% of the total virus population irrespective of the presence of unknown • Clinical cut-offs not available for all drugs resistance mutations • Costly (reimbursement by health insurance often • Measure of drug susceptibility feasible not guaranteed) irrespective of the complexity of resistance • Time-consuming (several weeks) patterns and the presence of resensitizing • HIV-1 subtyping not possible mutations • Interactions between antiviral drugs are not reflected in the test results • Test results are not affected by amino acid exchanges, which are only an intermediate step to resistance Basic principles of phenotyping Phenotypic resistance tests involve direct quantification of drug sensitivity. Viral replication is measured in cell culture under the selective pressure of increasing concentrations of antiretroviral drugs and is compared to viral replication of wild- type virus.
Two types of immune evasion have been identiﬁed: (1) tumor escape levitra extra dosage 60mg online, the loss of antigen presentation T-cell therapy using minor histocompatibility antigens through down-regulation of MHC and costimulatory molecules or The ﬁrst attempts at using minor histocompatibility antigen (mHag)– epigenetic down-regulation of TAA through demethylation buy levitra extra dosage 40 mg low cost, and (2) speciﬁc CTLs followed the discovery of the ﬁrst hematopoietic- 19-21 immune editing, T-cell suppression through the production of cyto- restricted mHag HA-1 by Goulmy et al. HA1-speciﬁc CTLs kines such as TGF- , the recruitment of suppressor cells, and other less have been successfully used to treat leukemia relapsing after HSCT, deﬁned mechanisms that favor an exhaustion T-cell phenotype. Because class II administration of T cells early in the course of the disease. Targeting molecules are predominantly restricted in their expression to multiple TAAs can reduce the risk from loss of TAA presentation, hematopoietic cells, these class II mHags are of particular interest 16-18 as we have shown for our leukemia and lymphoma strategies. In because of the potential leukemic speciﬁcity of CD4 T-cell 22,23 addition, demethylating agents such as 5 azacytidine can be used to alloresponses. The Leiden group has subsequently focused on 24 make the leukemia blasts or lymphoma cells reexpress antigen. Bleakely, et al demonstrated a have shown that patient-derived multi-TAA CTLs can efﬁciently feasible approach to generate mHag CTLs in vitro from unsensi- kill autologous tumors and that this effect was increased in the tized donors by stimulating naive CD8 T cells with recipient DCs. Leukemia-reactive T-cell clones are selected and tested to exclude recognition of patient ﬁbroblasts and for the ability to eliminate To counteract TGF- blockade, we have generated a retrovirus leukemia in a mouse model. Leukemia-recognizing T-cell clones vector expressing the dominant-negative TGF- type II receptor are further analyzed for their recognition element and the HLA (DNR) that prevents the formation of the functional tetrameric restriction of these CTLs. This approach successfully identiﬁed 29 TGF- receptor. Transduction of cytotoxic T cells with the DNR mHag-reactive T cells in every donor-recipient pair tested, leading can render the T cells resistant to this inhibitory cytokine. In vitro to the description of new mHags deﬁned at the genetic and protein 25 studies showed that DNR-transduced CTLs were resistant to the sequence level. However, these sophisticated, time-consuming, antiproliferative effects of recombinant TGF-. In addition, al- and expensive approaches are not widely available at present. Additional support for this approach comes clinical applicability. With the aim of creating a single CTL product have now begun a study using DNR-transduced LMP-CTLs for targeting myeloid and lymphoid malignancies in general, our patients with relapsed EBV HL and have shown persistence of the strategy has been to create DCs expressing entire sequences of transduced CTLs for up to 3 years, with clinical responses seen in multiple TAAs. In this way, the constraint of HLA restriction is the ﬁrst 8 patients ranging from stable disease to complete removed because the responding T cell can choose a cognate remissions (www. Using multiple TAAs, multispeciﬁc CTLs can be generated, eliminating the need to Identifying the so-called chemoresistant lymphoma stem cell or identify the speciﬁc TAA in the individual leukemia and decreasing leukemia initiating cell and targeting it will be necessary if Hematology 2014 567 immunotherapy is to eradicate residual disease, and it is increas- allogeneic HSCT, and have also been adopted in the autologous ingly clear that many hematological malignancies represent com- setting to favor the survival of tumor-speciﬁc T cells. Unfortunately, it is clear that true tumor-initiating cells are nity through blockade of the negative costimulation through anti protected by a low metabolic state and the BM niche that favors CTLA4 and anti PD1 to prevent T-cell exhaustion,37 are under dormancy, although preliminary studies suggest that it may be investigation, but are beyond the scope of this review. It appears that This has been helped by new technologies that support our ability to some myeloid malignancies have strong MDSC capacity, which generate potent antigen-speciﬁc CTLs expanded to clinical grade may limit the ability of T cells to eradicate bulk disease. The focus of research now moves toward clinical trials therapy may be more effective in remission when the leukemic bulk with adoptive T cells of deﬁned function to establish efﬁcacy in of suppressor cells is at its lowest. Tregs are increased in many diverse hematological malignancies. In the course of these trials, we lymphomas (eg, HL) and leukemia (eg, acute myeloid leukemia) will inevitably discover optimal approaches to T-cell therapy and and their presence may limit the full potential of T-cell therapy. Bollard, Children’s National Health System, Several factors are critical in the generation of potent CTLs. First, it 111 Michigan Ave NW, Washington, DC 20010; Phone: (832)824- is abundantly clear that short culture periods with limited exposure 4781; Fax: (202)476-6498; e-mail: cbollard@cnmc. Our current culture systems use IL-7 and IL-15 to induce 1. Progress in human tumour immunology and immuno- and expand CTLs from their naive or memory precursors. Graft-versus-leukemia within 3 weeks a T-cell product that has the capacity to persist and reactions after bone marrow transplantation. Graft-versus-leukemia effects of transplantation and donor CD4 and CD8 T cells favor the long-term persistence of CTLs in lymphocytes. T cells, whether CD4 or CD8, with potent cytotoxicity have 4.
The results of effectiveness studies are more applicable to the average patient than results from highly selected populations in efficacy studies cheap 60mg levitra extra dosage with visa. For each of the three key questions generic levitra extra dosage 60mg on-line, we evaluated specific outcome measures (where appropriate), as reported in Table 3. For efficacy and effectiveness, we focused on head-to-head trials comparing one second-generation antidepressant to another. When sufficient head-to-head evidence was not available, we evaluated placebo-controlled evidence of efficacy for medications not already approved by the FDA for the stated disorder. Observational studies were included to assess safety and tolerability. Studies were organized by disease state; we generalize efficacy, safety, and tolerability only to the disease state for which it was studied. Outcome measures and study eligibility criteria Outcome Outcome Measures Study Eligibility Criteria • Head-to-head randomized controlled clinical trials or meta-analyses • Response evaluating: • Remission - One second-generation • Speed of response/remission antidepressant compared with Efficacy/ • Relapse another Effectiveness • Quality of life • When sufficient evidence was not • Functional capacity available for head-to-head trials within • Hospitalization a specific diagnostic group, we evaluated: - Placebo-controlled trials • Overall adverse effect reports • Head-to-head randomized controlled • Withdrawals because of adverse effects clinical trials or meta-analyses • Serious adverse event reports evaluating: • Specific adverse events or withdrawals - One second-generation because of specific adverse events, antidepressant compared with including: another - gastrointestinal symptoms Safety/ Tolerability - hepatoxicity • When sufficient evidence was not - hyponatremia available for head-to-head trials within - loss of libido a specific diagnostic group, we - seizures evaluated - suicide - Placebo-controlled trials - weight gain - Observational studies, n > 1000 - others Second-generation antidepressants 12 of 190 Final Update 5 Report Drug Effectiveness Review Project METHODS A. Literature Search To identify articles relevant to each key question we searched PubMed, Embase, The Cochrane Library, CINAHL, PsycINFO, and the International Pharmaceutical Abstracts. We used either Medical Subject Headings (MeSH or MH) as search terms when available or key words when appropriate. We combined terms for selected indications (MDD, dysthymia, subsyndromal depression, seasonal affective disorder, general anxiety disorder, PTSD, OCD, panic disorder, social anxiety disorder, PMDD), drug interactions, and adverse events with a list of 12 specific second-generation antidepressants (citalopram, desvenlafaxine, escitalopram, fluoxetine, fluvoxamine, paroxetine, sertraline, mirtazapine, duloxetine, venlafaxine, bupropion, and nefazodone). We limited the electronic searches to “human” and “English language. We manually searched reference lists of pertinent and relevant review articles and letters ® to the editor. All citations were imported into an electronic database (Endnote v. Additionally, we handsearched the Center for Drug Evaluation and Research (CDER) database to identify unpublished research submitted to the FDA. Furthermore the Center for Evidence-based Policy at the Oregon Health and Science University (OHSU) contacted pharmaceutical manufacturers and invited them to submit dossiers, including citations, using a protocol issued by the Center for Evidence-based Policy (http://www. We received dossiers from six pharmaceutical companies. Study Selection Two persons independently reviewed abstracts. If both reviewers agreed that the trial did not meet eligibility criteria, we excluded it. We obtained the full text of all remaining articles. Records were considered for exclusion if they did not meet pre-established eligibility criteria with respect to study design or duration, patient population, interventions, outcomes, and comparisons to antidepressant medications outside our scope of interest. For this review, results from well-conducted, valid head-to-head trials provide the strongest evidence to compare drugs with respect to effectiveness, efficacy, and adverse events. RCTs of at least 6 weeks’ duration and an outpatient study population with a sample size greater than 40 participants were eligible for inclusion. We defined head-to-head trials as those comparing one second-generation antidepressant with another. We did not examine placebo-controlled trials in detail if head-to-head trials were available. We viewed FDA approval as evidence for general efficacy; therefore, we did not review placebo-controlled trials for FDA-approved indications except when outcome measures assessed quality of life or other health outcomes that are not generally required for FDA approval. If no head-to-head evidence was published, we reviewed placebo-controlled trials for indications of interest that had not already been approved by the FDA. We reviewed all placebo- controlled trials for indications without FDA approval to provide an overview of efficacy without taking drug equivalency into account. In other words, we did not evaluate the dosage of Second-generation antidepressants 13 of 190 Final Update 5 Report Drug Effectiveness Review Project one drug relative to the dosage of an alternative drug in a different trial.
Case-control study: A study that compares people with a specific disease or outcome of interest (cases) to people from the same population without that disease or outcome (controls) order 60 mg levitra extra dosage with visa. Clinical diversity: Differences between studies in key characteristics of the participants purchase levitra extra dosage 60 mg free shipping, interventions or outcome measures. Clinically significant: A result that is large enough to affect a patient’s disease state in a manner that is noticeable to the patient and/or a caregiver. Cohort study: An observational study in which a defined group of people (the cohort) is followed over time and compared with a group of people who were exposed or not exposed to a particular intervention or other factor of interest. A prospective cohort study assembles participants and follows them into the future. A retrospective cohort study identifies subjects from past records and follows them from the time of those records to the present. Combination Therapy: The use of two or more therapies and especially drugs to treat a disease or condition. Confidence interval: The range of values calculated from the data such that there is a level of confidence, or certainty, that it contains the true value. The 95% confidence interval is generally used in Drug Effectiveness Review Project reports. If the report were hypothetically repeated on a collection of 100 random samples of studies, the resulting 95% confidence intervals would include the true population value 95% of the time. Confounder: A factor that is associated with both an intervention and an outcome of interest. Controlled clinical trial: A clinical trial that includes a control group but no or inadequate methods of randomization. Control group: In a research study, the group of people who do not receive the treatment being tested. The control group might receive a placebo, a different treatment for the disease, or no treatment at all. Convenience sample: A group of individuals being studied because they are conveniently accessible in some way. Convenience samples may or may not be representative of a population that would normally be receiving an intervention. Crossover trial: A type of clinical trial comparing two or more interventions in which the participants, upon completion of the course of one treatment, are switched to another. Direct analysis: The practice of using data from head-to-head trials to draw conclusions about the comparative effectiveness of drugs within a class or group. Results of direct analysis are the preferred source of data in Drug Effectiveness Review Project reports. Dosage form: The physical form of a dose of medication, such as a capsule, injection, or liquid. The route of administration is dependent on the dosage form of a given drug. Various dosage forms may exist for the same compound, since different medical conditions may warrant different routes of administration. Dose-response relationship: The relationship between the quantity of treatment given and its effect on outcome. In meta-analysis, dose-response relationships can be investigated using meta- regression. Double-blind: The process of preventing those involved in a trial from knowing to which comparison group a particular participant belongs. While double-blind is a frequently used term Neuropathic pain 68 of 92 Final Update 1 Report Drug Effectiveness Review Project in trials, its meaning can vary to include blinding of patients, caregivers, investigators, or other study staff. Double-dummy: The use of two placebos in a trial that match the active interventions when they vary in appearance or method of administrations (for example, when an oral agent is compared with an injectable agent). Effectiveness: The extent to which a specific intervention used under ordinary circumstances does what it is intended to do. Effectiveness outcomes: Outcomes that are generally important to patients and caregivers, such as quality of life, responder rates, number and length of hospitalizations, and ability to work. Data on effectiveness outcomes usually comes from longer-term studies of a “real-world” population. Effect size/estimate of effect: The amount of change in a condition or symptom because of a treatment (compared to not receiving the treatment).
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