Biomedical subjects

M D Hughes

Publications and source records attributed to M D Hughes.

At least 19 recordsLinked to original sources

PubMed2001

Predictors of virologic and clinical outcomes in HIV-1-infected patients receiving concurrent treatment with indinavir, zidovudine, and lamivudine. AIDS Clinical Trials Group Protocol 320.

BACKGROUND: A substantial proportion of patients with HIV infection will not respond to antiretroviral therapy. Early predictors of response to treatment are needed to identify patients who are at risk for treatment failure. OBJECTIVE: To determine predictors of virologic and clinical response to indinavir, zidovudine, and lamivudine therapy. DESIGN: Observational analysis of one treatment group in a phase III trial. SETTING: 40 AIDS Clinical Trials units. PATIENTS: 489 patients receiving indinavir, zidovudine, and lamivudine who had 1) a CD4 count of 0.200 x 10(9) cells/L or less after 8 or more weeks of study therapy and 2) plasma HIV-1 RNA measurements obtained at baseline and week 8. MEASUREMENTS: HIV-1 RNA level and CD4 cell count at weeks 0, 4, 8, 24, and 40. Clinical progression was defined as a new AIDS-defining illness or death. RESULTS: Patients' levels of HIV-1 RNA at the 8th study week of therapy predicted whether patients would achieve virologic suppression to below 500 (or 50) copies/mL at study week 24. An HIV-1 RNA level less than 500 copies/mL at week 24 was achieved in 71% of patients whose level at week 8 had been less than 500 copies/mL, 53% of those with a level of 500 copies/mL or more and at least 2-log(10) copies/mL reduction since baseline, 29% of those with a level of 500 copies/mL or more with a 1- to 1.99-log(10) copies/mL reduction, and 9% of those with a level of 500 copies/mL or greater and less than 1-log(10) copies/mL reduction since baseline (P < 0.001). HIV-1 RNA level at week 8 also predicted clinical progression. HIV-1 disease progressed in 2.2% of the patients with a week-8 HIV-1 RNA level less than 500 copies/mL, 2.3% of patients with 500 copies/mL or greater and at least 2-log(10) copies/mL reduction since baseline, 4.9% of patients with 500 copies/mL or greater and 1- to 1.99-log(10) copies/mL reduction since baseline, and 10.6% of patients with 500 copies/mL or greater and less than 1-log(10) copies/mL decrease since baseline (P = 0.009). After adjustment for HIV-1 RNA level, patients with a higher week-8 CD4 cell count were more likely to have a week-24 HIV-1 RNA level less than 500 copies/mL (relative risk for patients with a week-8 CD4 count >/= 0.10 x 10(9) cells/L, 1.47 [95% CI, 1.00 to 2.16] compared with <0.050 x 10(9) cells/L; relative risk for patients with a week-8 CD4 count of 0.05 to 0.099 x 10(9) cells/L, 0.98 [CI, 0.61 to 1.57] compared with <0.050 x 10(9) cells/L). After adjustment for HIV-1 RNA level, patients with a week-8 CD4 count of 0.05 x 10(9) cells/L or greater (compared with <0.05 x 10(9) cells/L) had a decreased hazard for clinical progression (hazard ratio, 0.25 [CI, 0.09 to 0.67]). CONCLUSIONS: The HIV-1 RNA level and CD4 cell count achieved at 8 weeks of treatment are important predictors of subsequent virologic and clinical outcomes.

Adult↗

PubMed2001

Virologic and CD4 cell response to zidovudine or zidovudine and lamivudine following didanosine treatment of human immunodeficiency virus infection.

To optimize nucleoside reverse transcriptase inhibitor (nRTI) antiretroviral therapy, 137 subjects who had been treated with didanosine monotherapy for more than 3 years in the AIDS Clinical Trials Group (ACTG) 175 study were randomized to zidovudine and didanosine (dual therapy) or zidovudine, didanosine, and lamivudine (triple therapy). Evaluation of early (8 week) change in HIV plasma RNA demonstrated that addition of lamivudine and zidovudine provided significantly greater virologic suppression compared to the addition of zidovudine alone (mean decrease of 1.27 vs. 0.74 log(10) copies/ml, n = 108, p = 0.007). Both dual and triple therapy provided significant long-term decreases (from study entry to mean at Weeks 40 and 48) in HIV plasma RNA: 0.62 and 0.86 log(10) copies/ml, respectively (n = 110). However, the difference between treatments was not significant (p = 0.16). At 48 weeks, 26% of subjects starting study treatment had <500 copies/ml of plasma HIV RNA. The CD4 count response was greater at 4 weeks for triple versus dual therapy: a mean increase of 51 vs. 12 CD4 cells/ml(3) (n = 126, p = 0.039). The difference at Weeks 40 and 48 was not significant (a 22 cell increase vs. a 1 cell decrease, n = 129, p = 0.41). Zidovudine and didanosine treatment, with or without lamivudine, was well tolerated and only 2 of 137 (1.5%) of study participants developed an AIDS-defining event over 48 weeks.

Adult↗

PubMed2001

Dose-finding designs for HIV studies.

We present a class of simple designs that can be used in early dose-finding studies in HIV. Such designs, in contrast with Phase I designs in cancer, have a lot of the Phase II flavor about them. Information on efficacy is obtained during the trial and is as important as that relating to toxicity. The designs proposed here sequentially incorporate the information obtained on viral reduction. Initial doses are given from some fixed range of dose regimens. The doses are ordered in terms of their toxic potential. At any dose, a patient can have one of three outcomes: inability to take the treatment (toxicity), ability to take the treatment but insufficient reduction in viral load (viral failure), and ability to take the treatment as well as a sufficient reduction of viral load (success). A clear goal for some class of designs would be the identification of the dose leading to the greatest percentage of successes. Under certain assumptions, which we identify and discuss, we can obtain efficient designs for this task. Under weaker, sometimes more realistic assumptions, we can still obtain designs that have good operating characteristics in identifying a level, if such a level exists, having some given or greater success rate. In the absence of such a level, the designs will come to an early closure, indicating the ineffectiveness of the new treatment.

Anti-HIV Agents↗

PubMed2001

Impact of protease inhibitor-containing combination antiretroviral therapies on height and weight growth in HIV-infected children.

OBJECTIVE: To examine beneficial or detrimental effects of protease inhibitor (PI)-containing antiretroviral regimens on height and weight growth in children with human immunodeficiency virus (HIV) infection. METHODS: A prospective cohort study was conducted of 906 HIV-infected children, from pediatric research clinics in the United States, who were between 3 months and 18 years of age and who had height and weight assessed in 1995 (before introduction of PIs in this population) and at least once more through 1999. Changes in age- and gender-adjusted height and weight growth associated with PI use were assessed. RESULTS: Compared with a healthy reference population, children were more affected in height (mean z score: -0.90 [18th percentile]) than in weight (mean z score: -0.42 [34th percentile]) at baseline (1995). Two thirds of children received at least 1 PI during 1996 to 1999. In the multivariate mixed effects regression models adjusted for baseline log(10) CD4 cell count, baseline age, gender, and race/ethnicity, the use of PIs was associated with per-year gains of 0.13 z scores in height and 0.05 z scores in weight relative to the expected growth with non-PI-containing regimens (eg, after 1 year of PI use, a representative 6-year-old boy in our study would be approximately 0.7 cm taller and 0.1 kg heavier than if he had not received PIs). No significant differential effects of PIs on height or weight growth according to specific agents or children's sociodemographic or clinical characteristics were found. CONCLUSIONS: Although the use of PI-containing regimens was not associated with growth retardation, it was associated with only small annual increments in height and weight growth in HIV-infected children.

Adolescent↗

PubMed2000

Analysis and design issues for studies using censored biomarker measurements with an example of viral load measurements in HIV clinical trials.

For many biomarkers, the range (L,R) over which they can be quantified is restricted by technical limitations, leading to some measurements that are left or right censored. However, despite the widespread availability of statistical methods for the analysis of censored data, many studies use an imputed value for censored measurements (for example, replacing a value <L by L, or by L/2). Commonly, an analysis that ignores such imputation is then used. In clinical trials, this leads to bias and a loss of power in evaluating treatment effects. In this paper, a review of appropriate statistical methods for parametric and non-parametric analysis of such measurements is presented. This includes methods for situations in which baseline measurements are available. New results concerning design issues such as sample size determination are also presented. The paper is illustrated using two examples of studies that included censored measurements of viral load in HIV-infected subjects.

Biomarkers↗

PubMed2000

The delivery of antisense therapeutics.

Antisense oligonucleotides, ribozymes and DNAzymes have emerged as novel, highly selective inhibitors or modulators of gene expression. Indeed, their use in the treatment of diseases arising from genetic abnormalities has become a real possibility over the past few years. The first antisense drug molecule is now available for clinical use in Europe and USA. However, their successful application in the clinic will require improvements in cellular targeting and intracellular delivery. This review aims to look at recent advances in the in vitro and in vivo delivery of antisense oligodeoxynucleotides and ribozymes.

Animals↗

PubMed2000

Treatment-mediated changes in human immunodeficiency virus (HIV) type 1 RNA and CD4 cell counts as predictors of weight growth failure, cognitive decline, and survival in HIV-infected children.

This meta-analysis of 5 large studies of the Pediatric AIDS Clinical Trials Group was undertaken to evaluate the predictive value of antiretroviral treatment-mediated changes in 3 markers of human immunodeficiency virus (HIV) type 1 disease progression-HIV-1 RNA level, CD4 cell count, and CD4 percentage-for weight growth failure, cognitive decline, and survival in HIV-infected children. Proportional hazards models were used to assess the prognostic value of the markers at baseline and after 24 weeks of treatment, with data from 1089 children. Among children receiving nucleoside with or without nonnucleoside reverse-transcriptase inhibitors, higher immunologic and lower virologic markers at baseline and after 24 weeks were significant independent predictors of survival, whereas virologic markers were significant predictors of weight growth and cognitive failure in children >1 year old. The finding of differential age effects on pediatric-specific clinical outcomes emphasizes the need for continued investigation of treatment effects in children.

Acquired Immunodeficiency Syndrome↗

PubMed2000

Effect of lamivudine in HIV-infected persons with prior exposure to zidovudine/didanosine or zidovudine/zalcitabine.

Nucleoside analog-based regimens remain an integral component of combination therapy for use in both antiretroviral treatment-naive and experienced HIV-infected patients. To further define treatment responses to new antiretroviral therapy in patients with long-term experience to dual nucleoside analog therapy (zidovudine [ZDV] plus didanosine [ddI] or ZDV plus zalcitabine [ddC]), 325 subjects derived from the AIDS Clinical Trials Group (ACTG) 175 trial were randomized to three different combination regimens: (1) continuation of ZDV + ddI or ZDV + ddC (continuation arm), (2) addition of 3TC to ZDV + ddI or ZDV + ddC (addition arm), or (3) a switch to ZDV + 3TC therapy (switch arm). Both the addition and switch arms sustained significantly greater short-term (baseline to week 4) mean CD4+ cell count increases compared with the continuation arm (+36, +28 versus -4 cells/mm3; p = 0.012) and long-term CD4+ cell count responses (baseline to weeks 40/48: +32, +19 versus -9 cells/mm3; p = 0.003). Superior short-term (baseline to week 8) mean decreases in plasma HIV RNA (p < 0.001) were achieved by both the addition and switch arms (0.53 log10 and 0.54 log10 copies/ml, respectively) compared with the continuation arm (0.13 copies/ml) whereas no differences in long-term virologic suppression were observed (p = 0.30). At week 48, no differences were observed in the proportions of subjects who had HIV RNA levels below 500 copies/mL: 18% of subjects in each treatment arm (3-way p = 1.0). Overall, the treatments were well tolerated and only nine subjects (3%) died or developed one or more AIDS-defining events. While this study confirms the intrinsic antiretroviral activity of 3TC, only modest marker changes and limited short-term viral suppression are seen with incremental addition of the drug. The current approach of using 3TC in maximally suppressive regimens is preferred.

Adult↗

PubMed2000

Differences between women and men in adverse events and CD4+ responses to nucleoside analogue therapy for HIV infection. The Aids Clinical Trials Group 175 Team.

OBJECTIVE: To prospectively examine differences in baseline characteristics and study outcomes between HIV-infected women and men during a clinical trial of nucleoside analogue therapy. METHODS: ACTG 175 randomized HIV-infected patients with CD4+ counts between 200 and 500 cells/mm3 to one of four nucleoside analogue regimens: zidovudine (ZDV), didanosine (ddI), ZDV + ddI, or ZDV + zalcitabine (ddC). Differences in time to first dose modification, voluntary withdrawal, development of toxicity and symptomatology, and AIDS progression were compared by gender. RESULTS: The study included 438 women and 2029 men. Baseline values of HIV RNA plasma concentrations were significantly lower for women (0.3 log10) than men in a subset of patients in whom assays were taken and this difference persisted after adjustment for CD4+ count. Women reported reducing dosage and discontinue ddI-containing regimens more frequently than men did; adjustment for weight did not completely explain this difference. Women were at lower risk than men for progression to a study endpoint (19% of women versus 24% of men; p <.0001). Among those antiretroviral-naive study subjects receiving ZDV, men were four times more likely to progress to a study endpoint than women. CONCLUSIONS: Differences in pretreatment characteristics and on study experiences were demonstrated between women and men enrolled in this clinical trial. The suggestion of a gender difference in response to ZDV monotherapy by antiretroviral-naive study subjects and the lower baseline values for HIV RNA in women compared with those in men provides evidence for gender differences in the relationship between virus replication, CD4+ decline, and responses to nucleoside analogue therapy.

Adult↗

PubMed2000

The values of quantitative serum HIV-1 RNA levels and CD4 cell counts for predicting survival time among HIV-positive individuals with CD4 counts of < or = 50 x 10(6) cells/l.

OBJECTIVE: To evaluate the HIV-1 RNA level as a predictor of survival time among individuals with advanced AIDS. METHODS: The serum HIV-1 RNA level, the CD4 cell count, and other clinical variables were evaluated at baseline, as predictors of survival time, among 56 retrospectively identified HIV-1 positive individuals with < or = 50 x 10(6) CD4 cells/l who attended the Beth Israel Deaconess Medical Center, Division of Infectious Diseases, between 1 July 1989 and 30 September 1993. RESULTS: During follow-up, 55 of these 56 patients died. The median survival time was 20.5 months. In univariate Cox proportional hazard modeling neither the baseline HIV-1 RNA level nor the CD4 cell count were predictive of survival time. However, in multivariate models longer survival time was associated with the use of trimethoprim-sulphamethoxazole at entry [hazard ratio (HR), 0.42; P = 0.007], whereas shorter survival time was associated with a history of an AIDS-defining illness other than Pneumocystis carinii pneumonia (HR, 2.87; P = 0.007). Correlative analysis revealed a modest correlation of the baseline CD4 cell count with survival time (Spearman p = 0.41; P = 0.002). However, no correlation was found between HIV RNA levels and survival time (P = 0.5). CONCLUSIONS: In this population with very advanced disease, the HIV-1 RNA level was a poor discriminator of survival time, being inferior to the CD4 cell count and to specific clinical variables such as the nature of the prior AIDS-defining illness and the type of Pneumocystis carinii pneumonia prophylaxis employed. Among individuals with advanced AIDS, these data emphasize the relative importance of the CD4 cell count and of specific clinical factors, over the HIV-1 RNA level in predicting survival time.

AIDS-Related Opportunistic Infections↗

PubMed2000

Both serum HIV type 1 RNA levels and CD4+ lymphocyte counts predict clinical outcome in HIV type 1-infected subjects with 200 to 500 CD4+ cells per cubic millimeter. AIDS Clinical Trials Group Study 175 Virology Study Team.

To evaluate HIV-1 RNA and CD4+ cell responses to therapy as predictors of clinical progression and to evaluate levels and trends of these markers prior to clinical failure, HIV-1 RNA measurements were retrospectively obtained on subjects who progressed to AIDS or death and a random sample of subjects who did not. Samples were taken from AIDS Clinical Trials Group Study 175, a randomized trial comparing nucleoside analog therapies in subjects with CD4+ cell counts of between 200 and 500 cells/mm3. HIV-1 RNA and CD4+ cell count independently predicted clinical progression. Risk of subsequent progression is best captured by the change to the last measured value for CD4+ cell count and the area under the curve minus baseline, a measure of viral replication over time, for HIV-1 RNA. Subjects who failed had lower CD4+ cell counts, greater rates of CD4+ cell decline, and higher HIV-1 RNA levels, but not greater rates of HIV-1 RNA increase than subjects who did not. Subjects who maintained more than 200 CD4+ cells/mm3 and fewer than 10,000 copies of HIV-1 RNA per milliliter had low risk of progression. During the first few months of therapy, treatments are best monitored by regular HIV-1 RNA and less frequent CD4+ cell measurements. Thereafter, both markers should be monitored on a similar schedule to identify rapidly declining CD4+ cell counts, or adverse levels of either. These results further delineate the prognostic significance of HIV-1 RNA and CD4+ cell count and should help to better define their utility in the practice setting.

Adult↗

PubMed2000

A comparison of two dosing regimens of zidovudine in Thai adults with early symptomatic HIV infection. Conducting clinical HIV trials in South-East Asia.

AIM: To compare the clinical and immunological efficacy, and tolerance of two dosage regimens of zidovudine (ZDV) in an adult Thai population with early symptomatic human immunodeficiency virus (HIV) disease and to identify important clinical issues associated with conducting HIV trials in South-East Asia. METHODS: HIV-infected Thai adults, with early symptomatic HIV disease and CD4 lymphocyte counts less than 400/mm3, who were managed in the infectious diseases clinics at two university teaching hospitals in Bangkok, Thailand, were enrolled in a randomised, open-label, dose-regimen comparison trial of ZDV. Two oral ZDV dosing regimens: regimen A, 100 mg tid+200 mg nocte (ZDV-A) vs regimen B, 250 mg bid (ZDV-B) were compared. The main outcome measures were: 1. Clinical efficacy: rate of progression to acquired immunodeficiency syndrome (AIDS) or death. 2. Immunologic efficacy: changes in CD4 lymphocyte numbers compared to baseline; rate of decline of CD4 lymphocyte numbers to less than 100/mm3. 3. Toxicity, as defined by clinical symptomatology and laboratory parameters. RESULTS: Two hundred and four patients were enrolled (103 ZDV-A; 101 ZDV-B) of whom 195 were followed beyond baseline. Patients were typical of those encountered with HIV in Thailand: mean age 33 years; 89% male; 88% heterosexual HIV acquisition; mean baseline CD4 lymphocyte count 241/mm3. Follow-up while on therapy was comparable for the two groups (mean+/-SD): 533+/-236 days (ZDV-A) vs 592+/-210 days (ZDV-B). One hundred and eleven patients (57%; 51 ZDV-A; 60 ZDV-B) were treated for at least 22 months (669+/-30 days). Clinical and immunological outcomes for ZDV-A and ZDV-B, including rate of progression to AIDS or death, development of non-AIDS-defining opportunistic infections, mean changes in CD4 lymphocyte numbers/mm3, difference in area under the CD4:time distribution curve and difference in the rate of decline of CD4 lymphocyte numbers to less than 100/mm3, were not significantly different. The presence of oral hairy leukoplakia or unintentional weight loss of 10-20% at enrollment were significantly associated with the later development of AIDS (p=0.03 and 0.04, respectively). ZDV-associated toxicity was similar for both regimens. Maintaining protocol adherence and appropriate clinical follow-up emerged as important practical issues. CONCLUSION: In Thai adults, ZDV 100 mg tid+200 mg nocte and ZDV 250 mg bid have similar clinical and immunological efficacy. Rates of ZDV toxicity are comparable to those reported in non-Asian populations. Despite limitations in medical care access and maintaining long-term follow-up, successful trials of antiretroviral agents are feasible in South-East Asia and multi-drug treatment trials should be pursued in appropriate institutions.

Adolescent↗

PubMed1999

Autoregressive models for describing non-linear changes in biological parameters fitted using BUGS.

Many biological processes give outcome data which show a curvilinear association with time which tends to an asymptote. We show how autoregressive models can be used to describe this association within individual subjects. We also present a Bayesian approach implemented using statistical software, BUGS, to fit these models in a multi-level (hierarchical) setting that describes variation in the association between subjects. Peak expiratory flow data from a clinical trial involving subjects with asthma are used to illustrate the methods.

Anti-Inflammatory Agents↗

PubMed1999

Population pharmacokinetics of nevirapine, zidovudine, and didanosine in human immunodeficiency virus-infected patients. The National Institute of Allergy and Infectious Diseases AIDS Clinical Trials Group Protocol 241 Investigators.

The population pharmacokinetics of nevirapine (NVP), zidovudine (ZDV), and didanosine (ddI) were evaluated in a total of 175 patients infected with human immunodeficiency virus randomized to receive either a double combination of ZDV plus ddI or a triple combination of NVP plus ZDV plus ddI as a substudy of the AIDS Clinical Trials Group Protocol 241. Levels (approximating 3.5 determinations/patient) of the three drugs in plasma were measured during 44 of a total 48 weeks of study treatment, and a set of potential covariates was available for nonlinear mixed-effect modeling analysis. A one-compartment model with zero-order input and first-order elimination was fitted to the NVP data. Individual oral clearance (CL) and volume of distribution (V) averaged 0.0533 liters/h/kg of body weight and 1.17 liters/kg, respectively. Gender was the only covariate which significantly correlated with the CL of NVP. ZDV and ddI data were described by a two-compartment model with zero-order input and first-order elimination. Individual mean oral CL, VSS (volume of distribution at steady state), and V of ZDV were 1.84 liters/h/kg and 6.68 and 2.67 liters/kg, respectively, with body weight and age as correlates of CL and body weight as a correlate of VSS. The average individual oral CL, VSS, and V of ddI were 1.64 liters/h/kg and 3.56 and 2.74 liters/kg, respectively, with body weight as a significant correlate of both CL and VSS. The relative bioavailability (F) of ZDV and ddI in the triple combination compared to that in the double combination was also evaluated. No significant effects of the combination regimens on the F of ddI were detected (FTRIPLE = 1.05 and FDOUBLE = 1 by definition), but the F of ZDV was markedly reduced by the triple combination, being only 67.7% of that of the double combination. Large (>50%) intraindividual variability was associated with both ZDV and ddI pharmacokinetics. Individual cumulative area under the plasma drug level-time curve of the three drugs was calculated for the entire study period as a measure of drug exposure based on the individual data and the final-model estimates of structural and statistical parameters.

Acquired Immunodeficiency Syndrome↗

PubMed1998

Neuromuscular function in HIV infection: analysis of a placebo-controlled combination antiretroviral trial. AIDS Clinical Group 175/801 Study Team.

OBJECTIVE: To determine the frequency of peripheral neuropathy and myopathy in HIV-infected subjects enrolled in a combination antiretroviral treatment trial. DESIGN AND METHODS: AIDS Clinical Trial Group (ACTG) protocol 175 was a multicenter, double-blind, placebo-controlled, clinical trial. A total of 2467 subjects were randomized to one of four single or combination regimens, containing zidovudine (ZDV), didanosine (ddl), zalcitabine (ddC), and their respective placebos. Site investigators reported peripheral neuropathy, and the diagnosis of distal symmetrical neuropathy (DSP) was established by the study authors. Myalgia, muscle weakness and creatine phosphokinase (CPK) were prospectively assessed in a subset of the antiretroviral-naive cohort (n = 1067). RESULTS: Of 222 site diagnoses of neuropathy, 109 (49%) were DSP. There was a significant difference between treatment arms for rate of DSP and time to first grade 2 or higher DSP (ZDV-ddC, 6%; ZDV, 4%; ZDV-ddl, 4%; ddl, 3%; P = 0.029). Age and Karnofsky score were significant predictors of DSP. Fifty-six (54%) out of 104 patients with DSP remained on study medication at full (n = 29) or reduced (n = 27) dose within 6 months of developing neuropathy. There was no significant difference between treatment arms in the rate of myalgia or muscle weakness. The median CPK of subjects on ZDV-ddC was significantly higher than other study treatments, although CPK levels did not correlate with symptoms of myopathy. Only six subjects were diagnosed with myopathy during the study (one ZDV-ddl, one ZDV-ddC, and four ddl). CONCLUSIONS: DSP and myopathy may occur with current dosing regimens of combination antiretroviral therapy, and should be diagnosed using stringent criteria. ZDV-ddC was associated with the highest rate of DSP, although features of myopathy were not significantly different between treatment regimens.

Adult↗

PubMed1998

Statistical issues for HIV surrogate endpoints: point/counterpoint. An NIAID workshop.

This paper summarizes the proceedings of an NIAID-sponsored workshop on statistical issues for HIV surrogate endpoints. The workshop brought together statisticians and clinicians in an attempt to shed light on some unresolved issues in the use of HIV laboratory markers (such as HIV RNA and CD4+ cell counts) in the design and analysis of clinical studies and in patient management. Utilizing a debate format, the workshop explored a series of specific questions dealing with the relationship between markers and clinical endpoints, and the choice of endpoints and methods of analysis in clinical studies. This paper provides the position statements from the two debaters on each issue. Consensus conclusions, based on the presentations and discussion, are outlined. While not providing final answers, we hope that these discussions have helped clarify a number of issues, and will stimulate further consideration of some of the highlighted problems. These issues will be critical in the proper assessment and use of future therapies for HIV disease.

Biomarkers↗

PubMed1998

CD4 cell count as a surrogate endpoint in HIV clinical trials: a meta-analysis of studies of the AIDS Clinical Trials Group.

OBJECTIVE: To evaluate initial changes in CD4 cell count as a surrogate endpoint for clinical outcome in HIV-infected patients. DESIGN: Meta-analysis of all relevant Phase II and III randomized clinical trials undertaken by the Adult AIDS Clinical Trials Group. METHODS: Individual patient data were obtained from each clinical trial, and the difference between a pair of treatments in their effect on clinical outcome (AIDS or death, or death alone) during 2 years of follow-up was evaluated. The proportion of treatment effect explained (PTE) was the proportion of this difference explained by the change in CD4 cell count 6 months after starting treatment, evaluated using proportional hazards models. A weighted average PTE across treatment comparisons was obtained. The association between the difference between treatments in clinical outcome, expressed as hazard ratio, and the difference in mean change in CD4 cell count was evaluated using regression analysis. RESULTS: There were 15 clinical trials involving 24 treatment comparisons. The weighted average PTE for both progression to AIDS or death was 0.16 [95% confidence interval (Cl), 0.07-0.26] and for death was 0.10 (95% Cl, 0.00-0.20). There were significant associations between treatment differences in effect on AIDS or death, and on death alone, and the difference in mean change in CD4 cell count. A difference in mean change in CD4 cell count of 30 or 40 x 10(6)/l or more in favor of the test treatment indicated with high probability that there was a corresponding difference in progression to AIDS or death. CONCLUSIONS: The small PTE suggest that other mechanisms of drug action not captured by initial change in CD4 cells are important. CD4 cell count is a weak surrogate endpoint, but has some value as an aid for screening treatments for drug development or preliminary regulatory approval.

Anti-HIV Agents↗

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↗