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V DeGruttola

Publications and source records attributed to V DeGruttola.

17 recordsLinked to original sources
PubMed1999

Clinical trials using HIV-1 RNA-based primary endpoints: statistical analysis and potential biases.

Clinical trial endpoints based on magnitude of reduction in HIV-1 RNA levels provide an important complement to endpoints based on percentage of patients achieving complete virologic suppression. However, interpretation of magnitude of reduction can be biased by measurement limitations of virologic assays, particularly lower and upper limits of quantification. Using data from two AIDS Clinical Trials Group (ACTG) studies, widely used crude methods of analyzing HIV-1 RNA reductions were compared with methods that take into account censoring of HIV-1 RNA measurements. Such methods include Kaplan-Meier and censored regression analyses. It was found that standard crude methods of analysis consistently underestimated treatment effects. In some cases, the bias induced by crude methods masked statistically significant differences between treatment arms. Although statistically significant, adjustment for baseline HIV-1 RNA levels had little effect on estimated treatment differences. Furthermore, convenient parametric analyses performed as well as more complex nonparametric analyses. It is concluded that conveniently implemented censored data analyses should be conducted in preference to widely used crude analyses of magnitude of HIV-1 RNA reduction. To obtain complete information about virologic response to antiretroviral therapy, such analyses of magnitude of virologic response should be used to complement analyses of the percentage of patients having complete virologic suppression.

Bias↗
PubMed1999

Treatment with amprenavir alone or amprenavir with zidovudine and lamivudine in adults with human immunodeficiency virus infection. AIDS Clinical Trials Group 347 Study Team.

Amprenavir is a human immunodeficiency virus (HIV) protease inhibitor with a favorable pharmacokinetic profile and good in vitro activity. Ninety-two lamivudine- and protease inhibitor-naive individuals with >/=50 CD4 cells/mm3 and >/=5000 HIV RNA copies/mL were assigned amprenavir (1200 mg) alone or with zidovudine (300 mg) plus lamivudine (150 mg), all given every 12 h. After a median follow-up of 88 days, the findings of a planned interim review resulted in termination of the amprenavir monotherapy arm. Among 85 subjects with confirmed plasma HIV RNA determination, 15 of 42 monotherapy versus 1 of 43 triple-therapy subjects had an HIV RNA increase above baseline or 1 log10 above nadir (P=.0001). For subjects taking triple therapy at 24 weeks, the median decrease in HIV RNA was 2.04 log10 copies/mL, and 17 (63%) of 27 evaluable subjects had <500 HIV RNA copies/mL. Treatment with amprenavir, zidovudine, and lamivudine together reduced the levels of HIV RNA significantly more than did amprenavir monotherapy.

Adult↗
PubMed1998

Use of changes in plasma levels of human immunodeficiency virus type 1 RNA to assess the clinical benefit of antiretroviral therapy.

Data from 1330 human immunodeficiency virus type 1 (HIV-1)-infected patients enrolled in seven antiretroviral treatment trials were analyzed to characterize the clinical benefit of treatment-mediated reductions in plasma HIV-1 RNA levels. The risk of a new AIDS-defining event or death was reduced proportionally to the magnitude of the reduction of the HIV-1 RNA level during the first 6 months of therapy. Pretherapy HIV-1 RNA levels were prognostic independently of on-therapy levels. In addition, the reduction in risk associated with any given reduction of the level of HIV-1 RNA did not vary by pretherapy level. Having either a reduction in HIV-1 RNA level or an increase in CD4+ lymphocyte count, or both, was associated with a delay in clinical disease progression. This indicates that patient prognosis should be assessed using both HIV-1 RNA and CD4+ lymphocyte responses to therapy.

Acquired Immunodeficiency Syndrome↗
PubMed1998

Efficient trial designs for studying combination antiretroviral treatments in patients with various resistance profiles.

Selecting antiretroviral therapies for human immunodeficiency virus type 1-infected persons is complicated by the availability of a vast number of potentially useful drug combinations and by extensive variation among patients in their resistance to various drugs. AIDS clinical trials have used designs in which a handful of drug regimens in a few patient classes can be compared. Here is proposed implementation of innovative designs with factorial structure that permit assessment of many treatment arms and patient classes in a single trial; when and how they can be appropriately used are discussed. These designs are efficient, permit systematic investigation of correlations between genetic mutations and in vivo drug resistance, and provide insight into important drug interactions in people that conventional designs are unable to provide. Through creative application of these designs, identification of superior drug combinations and the science of understanding in vivo joint drug dynamics and genotypic resistance will progress at an optimum pace.

Anti-HIV Agents↗
PubMed1996

Lack of effect of cimetidine on lymphocyte subsets in patients infected with human immunodeficiency virus type 1.

Cimetidine, widely used for peptic ulcer disease, blocks type 2 histamine receptors present on immune cells, including T cells, B cells, and monocytes. As an earlier published study showed evidence of increases in CD4 cell counts due to this drug, we conducted a randomized, placebo-controlled, 8-week trial of oral cimetidine (400 mg p.o. t.i.d.) in a study involving 182 patients infected with human immunodeficiency virus (HIV). Overall, cimetidine-treated patients had a decline in CD4+ cell counts that was no different from the decline for placebo-treated persons, neither during the first 8 weeks of the trial (mean drop, 7.1% [standard error, 12.1-1.8] vs. 6.7% [standard error, 11.6-1.5]) nor during the subsequent 8 weeks of open-label administration of cimetidine. No differences were evident between the treatment groups in terms of the percentage reactive to p24 antigen at baseline, and p24 antigen concentrations did not change from baseline to the end of week 8. In summary, cimetidine is well tolerated by HIV-infected individuals but alters neither CD4+ cell counts nor at least one quantitative measure of viral load, HIV p24 antigen levels.

Adult↗
PubMed1996

Association of plasma human immunodeficiency virus type 1 RNA level with risk of clinical progression in patients with advanced infection. AIDS Clinical Trials Group (ACTG) 116B/117 Study Team. ACTG Virology Committee Resistance and HIV-1 RNA Working Groups.

Human immunodeficiency virus (HIV)-1 RNA level in plasma was evaluated as a surrogate marker for disease progression in a clinical trial of advanced HIV-1 infection. Baseline HIV-1 RNA level was an independent predictor of disease progression (relative hazard [RH] for each doubling of HIV-1 RNA level, 1.26; 95% confidence interval [CI], 1.03-1.54; P = .02), after adjusting for the week 4 change in HIV-1 RNA level, baseline CD4 cell count, syncytium-inducing phenotype, clinical status at study entry, and therapy randomization. A 50% reduction in HIV-1 RNA level was associated with a 27% decrease in the adjusted risk of disease progression during the study (RH, 0.73; 95% CI, 0.52-1.02; P = .07). The partial validation of HIV-1 RNA as a predictor for clinical end points has implications for the use of HIV-1 RNA in clinical trials and practice.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Randomized study of didanosine monotherapy and combination therapy with zidovudine in hemophilic and nonhemophilic subjects with asymptomatic human immunodeficiency virus-1 infection. AIDS Clinical Trial Groups.

To evaluate the safety and efficacy of didanosine (ddl) monotherapy and three different combinations of zidovudine (ZDV) and ddl in asymptomatic human immunodeficiency virus-1 (HIV-1) infection, we conducted an open-label, phase I/II study in 126 asymptomatic HIV-1-infected hemophilic and nonhemophilic subjects with a CD4 count of 200 to 500/mm3 stratified for prior zidovudine treatment and baseline CD4 count. Study arms included arm A, low-dose combination (ZDV 150 mg and ddl 134 mg, daily); arm B, moderate-dose combination (ZDV 300 mg and ddI 334 mg, daily); arm C, high-dose combination (ZDV 600 mg and ddl 500 mg, daily), and arm D, ddl monotherapy (ddl 500 mg, daily). Earlier, more frequent hepatotoxicity was experienced by hemophilic subjects (P = .008), but there were no differences in toxicity between treatment arms (P = .51), nor were there any differences in the rate of development of clinical endpoints by treatment (P = .41). Smaller median CD4 increases occurred over the first 12 weeks for arms A and D, 44/mm3 and 42/mm3, than arms B and C, 105/mm3 and 114/mm3, respectively, (P = .015). Hemophilia status (P = .0004) and prior ZDV experience (P = .044) independently predicted weaker CD4 responses during the first 12 weeks of treatment. Using a regression model and adjusting for hemophilia status, prior ZDV treatment, and baseline CD4, there was a significant reduction in quantitative viral load from baseline by week 12 for all treatment arms combined (P = .0001), with significantly lower median percent reduction for arm A (56.3%) than arms B, C, and D (94.6%, 98.5%, and 91.9%, respectively, P = .015). Although greater hepatoxicity and weaker CD4 responses occur in hemophilic subjects, didanosine monotherapy and combination therapy with zidovudine are safe and effective in asymptomatic HIV-1-infected patients.

Adult↗
PubMed1995

Zidovudine resistance and HIV-1 disease progression during antiretroviral therapy. AIDS Clinical Trials Group Protocol 116B/117 Team and the Virology Committee Resistance Working Group.

OBJECTIVE: To evaluate the association between resistance of human immunodeficiency virus type 1 (HIV-1) to zidovudine and clinical progression. DESIGN: Retrospective analysis of specimens from patients in the AIDS Clinical Trials Group (ACTG) protocol 116B/117, a randomized comparison of didanosine with continued zidovudine therapy in patients with advanced HIV-1 disease who had received 16 weeks or more of previous zidovudine therapy. SETTING: Participating ACTG virology laboratories. PATIENTS: 187 patients with baseline HIV-1 isolates. MEASUREMENTS: Zidovudine susceptibility testing and assays for syncytium-inducing phenotype were done on baseline HIV-1 isolates. Relative hazards for clinical progression or death associated with baseline clinical, virologic, and immunologic factors were determined from Cox proportional hazards regression models. RESULTS: Compared with other patients, 15% (26 of 170) with isolates showing high-level zidovudine resistance (50% inhibitory zidovudine concentration > or = 1.0 microM) had 1.74 times the risk for progressing to a new AIDS-defining event or death (95% CI, 1.00 to 3.03) and 2.78 times the risk for death (CI, 1.21 to 6.39) in analyses that controlled for baseline CD4+ T-lymphocyte count, syncytium-inducing HIV-1 phenotype, disease stage, and randomized treatment assignment. The clinical benefit of didanosine was not limited to patients with highly zidovudine-resistant baseline HIV-1 isolates. CONCLUSIONS: High-level resistance of HIV-1 to zidovudine predicted more rapid clinical progression and death when adjusted for other factors. However, patients with advanced HIV-1 disease may benefit from a change in monotherapy from zidovudine to didanosine whether high-level HIV-1 resistance to zidovudine is present or absent, and laboratory assessment of zidovudine resistance is not necessary for deciding when to switch monotherapy from zidovudine to didanosine.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Human immunodeficiency virus type 1 quantitative cell microculture as a measure of antiviral efficacy in a multicenter clinical trial.

A quantitative cell microculture assay (QMC) was used to measure the human immunodeficiency virus type 1 (HIV-1) peripheral blood mononuclear cell (PBMC)-associated titer in 109 subjects rolled in an open-label phase I/II study of didanosine monotherapy or combination therapy with zidovudine. The titer was inversely correlated with CD4+ cell count at baseline (r = .37, P = .001). After 12 weeks of therapy, subjects showed a significant decreases in virus titer and those with the highest baseline virus titers had the greatest increase in CD4+ cell number (r = .430, P = .002). The QMC assay was more sensitive (98%) for assessing the antiretroviral effect of therapy than was immune complex-dissociated HIV p24 antigen (32%) or plasma culture (3.4%). Estimated sample sizes for phase I/II clinical trials were derived using the within-subject QMC SD of .72 log10 infectious units per 10(6) PMBC.

CD4 Lymphocyte Count↗
PubMed1995

Evaluating surrogate markers.

We discuss approaches for efficiently evaluating potential surrogate markers; in particular, we focus on case-cohort designs in which marker evaluation is undertaken only for a random sample of subjects within a randomized trial and for all other subjects who develop a major clinical outcome. These designs will be useful in clinical trials in which a highly significant treatment difference on clinical outcome has been obtained. In addition, we describe a method for using data from all available studies using a meta-analysis to explore the association of treatment effects on the potential marker and on clinical outcome. This may be the most effective approach for marker evaluation because it uses data from both large and small trials and incorporates information from trials in which nonsignificant treatment differences on the major clinical outcome are obtained.

Biomarkers↗
PubMed1994

Serum p24 antigen level as an intermediate end point in clinical trials of zidovudine in people infected with human immunodeficiency virus type 1. Aids Clinical Trials Group Virology Laboratories.

Serum p24 antigen levels were examined in subjects from three clinical trials of zidovudine to determine whether the pattern of change in serum p24 antigen during the first 8-16 weeks of therapy was associated with human immunodeficiency virus type 1 (HIV-1) disease progression or death. Among 406 patients with AIDS and a first episode of Pneumocystis carinii pneumonia, 65% had measurable pretreatment concentrations of serum p24 antigen (> or = 10 pg/mL). Changes during treatment were not associated with reduced mortality. In 637 mildly symptomatic patients, 24% had measurable concentrations, and changes were marginally associated with increased time until more advanced disease. Among 683 asymptomatic patients, 18% had measurable concentrations, and changes were not associated with increased time until progression. Despite the small number of clinical events and the low rate of serum p24 antigen positivity in the latter two studies, pretreatment serum p24 antigen levels were predictive of clinical outcome; subsequent measurements appear to be of limited use in evaluating zidovudine therapy.

AIDS-Related Complex↗
PubMed1989

Infectiousness of HIV between male homosexual partners.

To estimate the risk of transmission of HIV per receptive anal sexual contact, 329 homosexually-active men, representing 155 sexual partnerships, were enrolled into a study. Information on HIV infection status and sexual behavior within and outside the primary relationship was collected. Of these 329 men, 24 had AIDS and 31 had ARC. Of the 155 couples, 35 consisted of partners that were both HIV +; 62 of partners that were both HIV-; and 58 were discordant. A binomial model was fit to data obtained in the first visit to estimate per contact risk of HIV transmission. Assuming a constant risk of transmission per sexual contact between infected and uninfected partners, the estimated risk is about 5 to 30 per 1000 receptive anal exposures to ejaculate. Although the average risk of HIV transmission per sexual contact appears to be low, there appears to be great variability in infectivity. To model this variability over time and across individuals, more complex models must be fit to longitudinal studies of sexual partners.

AIDS-Related Complex↗
PubMedDate not supplied

Models for empirical Bayes estimators of longitudinal CD4 counts.

In this paper we consider the choice of model used in estimation of trajectories of CD4 T-cell counts by empirical Bayes estimators. Tsiatis et al. have demonstrated that empirical Bayes estimates of CD4 values correct for the bias resulting from measurement error when using CD4 as a covariate in a Cox model to predict clinical events. Here, empirical Bayes estimates from a random effects model are compared to estimates from the more general stochastic regression model presented in Taylor et al. Empirical Bayes estimators based on the two models are judged according to their ability to provide parameter estimates in a Cox model predicting clinical outcomes. Data from ACTG 118 are used as an illustration.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

Surrogate endpoints.

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Anti-HIV Agents↗