Nachman SA, Stanley K, Yogev R, Pelton S, Wiznia A, Lee S, Mofenson L, Fiscus S, Rathore M, Jimenez E, Borkowsky W, Pitt J, Smith ME, Wells B, McIntosh K, for the Pediatric AIDS Clinical Trials Group 338 Study Team . Nucleoside Analogs Plus Ritonavir in Stable Antiretroviral Therapy–Experienced HIV-Infected ChildrenA Randomized Controlled Trial. JAMA. 2000;283(4):492-498. doi:10.1001/jama.283.4.492
Author Affiliations: Departments of Pediatrics, State University of New York at Stony Brook (Dr Nachman), Jacobi Medical Center, Albert Einstein College of Medicine (Dr Wiznia), New York University Medical Center (Dr Borkowsky), and Department of Pediatric Infectious Disease, College of Physicians and Surgeons, Columbia University (Dr Pitt), New York, NY; Center for Biostatistics in AIDS Research, School of Public Health, Harvard University (Dr Stanley and Ms Lee), Section of Pediatric Infectious Diseases, Boston Medical Center (Dr Pelton), and Department of Medicine, Division of Infectious Disease, Children's Hospital of Boston (Dr McIntosh), Boston, Mass; Division of Infectious Diseases, Children's Memorial Hospital, Chicago, Ill (Dr Yogev); Pediatric Adolescent and Maternal AIDS Branch, Center for Research for Mothers and Children, National Institute of Child Health and Human Development (Dr Mofenson) and Division of AIDS, National Institute of Allergy and Infectious Diseases (Dr Smith), National Institutes of Health, Bethesda, Md; Department of Microbiology and Immunology, School of Medicine, University of North Carolina at Chapel Hill (Dr Fiscus); Department of Pediatrics, Health Science Center, University of Florida, Jacksonville (Dr Rathore); Department of Pediatrics, San Juan City Hospital, San Juan, Puerto Rico (Dr Jimenez); and Section of Pediatric Infectious Disease, Social and Scientific Systems, Rockville, Md (Ms Wells).
Context Although protease inhibitors are used routinely in adults with human
immunodeficiency virus (HIV) infection, the role of these drugs in the treatment
of clinically stable HIV-infected children is not clear.
Objective To evaluate the safety, tolerance, and virologic response produced by
a change in antiretroviral therapy in HIV-infected children who were clinically
and immunologically stable while receiving previous therapy.
Design The Pediatric AIDS Clinical Trials Group 338, a multicenter, phase 2,
randomized, open-label controlled trial conducted from February 6 to April
30, 1997 (patient entry period); patients were followed up for 48 weeks.
Setting Pediatric HIV research clinics in the United States and Puerto Rico.
Patients Two hundred ninety-seven antiretroviral-experienced, protease inhibitor–naive,
clinically stable HIV-infected children aged 2 to 17 years.
Interventions Children were randomized to receive zidovudine, 160 mg/m2
3 times per day, plus lamivudine, 4 mg/kg 2 times per day (n = 100); the same
regimen plus ritonavir, 350 mg/m2 2 times per day (n = 100); or
ritonavir, 350 mg/m2 2 times per day, and stavudine, 4 mg/kg 2
times per day (n = 97).
Main Outcome Measure Plasma HIV-1 RNA levels at study weeks 12 and 48, compared among the
3 treatment groups.
Results At study week 12, 12% of patients in the zidovudine-lamivudine group
had undetectable plasma HIV RNA levels (<400 copies/mL) compared with 52%
and 54% of patients in the 2- and 3-drug ritonavir-containing groups, respectively
(P<.001). Through study week 48, 70% of children
continued receiving their ritonavir-containing regimen. At study week 48,
42% of children receiving ritonavir plus 2 nucleosides compared with 27% of
those receiving ritonavir and a single nucleoside had undetectable HIV RNA
levels (P = .04); however, similar proportions in
each group continuing initial therapy had HIV RNA levels of less than 10,000
copies/mL (58% vs 48%, respectively; P = .19).
Conclusions In our study, change in antiretroviral therapy to a ritonavir-containing
regimen was associated with superior virologic response at study week 12 compared
with change to a dual nucleoside analog regimen. More children receiving ritonavir
in combination with 2 compared with 1 nucleoside analog had undetectable HIV
RNA levels at study week 48.
In early 1997 many children infected with human immunodeficiency virus
(HIV) were receiving single or dual nucleoside analog therapy and were clinically
and immunologically stable,1,2
despite increasing plasma HIV RNA levels. However, the availability of protease
inhibitors and their demonstrated success in adults raised the question of
how they should be used in children. Pediatric AIDS Clinical Trials Group
(PACTG) Protocol 338 was undertaken to evaluate the safety, tolerance, and
virologic efficacy of changing from current antiretroviral treatment in clinically
and immunologically stable, protease inhibitor–naive children to either
dual nucleoside analog therapy or a 2- or 3-drug regimen containing a protease
Current antiretroviral guidelines for treatment of HIV-infected children
and adults recommend initiation of therapy with a combination of antiretroviral
drugs, including a protease inhibitor.3,4
Preliminary results from PACTG Protocol 3385
were instrumental in clarifying the role of protease inhibitors for children
in these guidelines. Therapeutic results at 1 year are presented in this article.
The PACTG 338 study was a multicenter, randomized, phase 2 clinical
trial that compared change from current therapy to either zidovudine plus
lamivudine or 1 of 2 ritonavir-containing regimens (a 3-drug regimen of ritonavir,
zidovudine, and lamivudine or a 2-drug regimen of ritonavir and stavudine)
in HIV-infected, clinically stable children. All subjects were aged 24 months
to 17 years; had stable CD4 cell number or percentage maintained in Centers
for Disease Control and Prevention (CDC) immune category 1 or 2 during the
4 months prior to study entry6; had experienced
no new CDC clinical category C diagnosis in the 12 months prior to study entry;
received continuous antiretroviral therapy in the 16 weeks prior to study
entry; and were either zidovudine- and lamivudine-naive or had received no
more than 6 weeks of zidovudine and lamivudine in the year prior to study
entry and none in the 4 months prior to study entry. Exclusion criteria included
current grade 3 or 4 adverse effect (as judged by protocol-specified, standard
pediatric toxicity criteria); active opportunistic and/or serious bacterial
infection; documented hypersensitivity to any of the therapies under study;
prior protease inhibitor therapy; or current diagnosis of malignancy or pregnancy.
Children were stratified by CD4 cell percentage (<25% vs ≥25%
of the normal range) and randomized in a balanced fashion to 1 of 3 open-label
treatment arms. Medication doses dispensed were 160 mg/m2 of zidovudine
(maximal dose, 200 mg/dose) 3 times per day and 4 mg/kg of lamivudine (maximal
dose, 150 mg/dose) twice per day; that same regimen with 350 mg/m2
of ritonavir (maximal dose, 600 mg/dose) twice per day; or 350 mg/m2 of ritonavir twice per day and 4 mg/kg of stavudine (maximal dose,
40 mg/dose) twice per day.
The primary objective of the study was to evaluate the safety and tolerance
of these 3 treatment regimens and compare the change in plasma HIV RNA copy
number between entry and study weeks 12 and 48 among the regimens. The duration
of study treatment for each patient was initially planned to be 48 weeks but
was subsequently extended to 120 weeks. Only 48-week outcomes are presented
here. Randomized study treatment was discontinued for children who experienced
a virologic failure, disease progression, or persistent grade 3 or higher
drug-related adverse effects. Such children were offered the best available
therapy at the discretion of their clinician, themselves, or their parents.
All subjects were enrolled for the full study period of 48 weeks.
A primary virologic failure at week 12 was defined as a failure to achieve
either HIV RNA copy number of at least 2.0 log10 copies/mL below
baseline values or to maintain at least 10,000 copies/mL. A subsequent virologic
failure was defined as a persistent 0.75 log10 increase above the
nadir in HIV RNA copy number for patients who had an initial HIV RNA copy
number decrease of more than 2 log10 but whose RNA remained at
more than 10,000 copies/mL at study week 12, or as a persistent increase in
HIV RNA to more than 10,000 copies/mL for patients who had an initial HIV
RNA decrease to less than 10,000 copies/mL.
Two hundred ninety-eight HIV-infected children from 48 sites were enrolled
in the study. The institutional review board at each institution approved
the study, and informed consent was obtained from all patients or their parents.
Evaluations were performed within 14 days prior to randomization (the
preentry visit), at study entry, and every 4 weeks during the study. These
visits included a medical history, physical examination, a complete blood
cell count with differential and serum chemistries. Lymphocyte surface markers
were evaluated at preentry; entry; study weeks 4, 8, 12, and every 12 weeks
thereafter and were performed by local laboratories participating in the National
Institute of Allergy and Infectious Diseases (NIAID) Flow Cytometry Quality
Assurance Program.7 Specimens for HIV-1 RNA
were obtained at preentry; entry; and at study weeks 4, 12, 24, 36, 44, 48,
and every 12 weeks thereafter. The NucliSens Assay (Organon Teknika, Durham,
NC)8 was used in the assessment of HIV RNA
copy number.9 Specimens from individuals from
preentry through week 12 were assayed for HIV RNA copy number in batched fashion;
subsequent specimens were run at the specified individual time points. The
lower limit of assay quantification for RNA was 400 copies/mL. Assay results
were adjusted using Virology Quality Assurance (VQA) standards.10
All adverse events were graded using protocol-specified, standard toxicity
criteria for pediatric populations. Only those events occurring during therapy
or less than 60 days after termination of initial study medication were included
in the analysis.
A minimum of 80 children were planned to be enrolled in each of the
3 arms of this study. This sample size would ensure a power of 80% to detect
a difference of one third in the average change in log10 RNA copy
number between 2 therapy arms using a 2-sided P =
.05 level of significance. The primary end point of the study was initially
specified to be the change in HIV RNA from baseline. However, since the majority
of patients in the ritonavir arms were observed to have HIV RNA copy numbers
below the level of assay quantification (<400 copies/mL) at the week 12
interim analysis, the primary end point for the study was changed to the proportion
of children with values below the level of assay quantification, consistent
with other, similar studies.
Comparisons among treatment groups used the Fisher exact test for categorical
variables and Wilcoxon/Kruskal-Wallis test for continuous variables.11,12 An RNA assay result was categorized
as below the level of quantification (undetectable) if the VQA-adjusted result
was less than 400 copies/mL. Comparisons of the rates of undetectable RNA
by baseline RNA values used the Fisher exact test for ordered categorical
data.13 The baseline RNA value was defined
to be the geometric mean of the preentry and the entry values. Patients with
undetectable baseline RNA values could not contribute to the determination
of the change from detectable to undetectable RNA and so were excluded from
Some patients experienced virologic failure and discontinued their randomized
study treatment. These patients remained on study follow-up but received nonprotocol
alternative antiretroviral treatment that could affect their subsequent virologic
evaluation during follow-up. To avoid confounding the study-related evaluations
by such nonstudy antiretroviral treatment, a child was classified as having
an undetectable level of RNA at a specific study week only if the child was
still receiving initial randomized study treatment at that time. The number
of patients on the treatment arm at baseline serves as the denominator for
this conservative definition of response rate.
Periodic interim monitoring of this study by an independent study monitoring
committee was planned at weeks 12 and 24 using protocol-specified criteria
for the stopping or modification of a treatment arm. The criterion for stopping
a specific treatment at the week 12 interim analysis was the detection of
a statistically and medically significant difference in virologic efficacy
between any 2 treatment arms; a virologically inferior arm was defined as
a one in which the average change in HIV RNA copy number was at least 1.5
log10 less than that in another arm or in which the proportion
of children who achieved HIV RNA levels below quantification was at least
50% lower than that in another arm. All analyses were based on an intent-to-treat
approach.14 All P
values were 2-sided, were not adjusted for multiple comparisons, and were
not adjusted for interim analyses.
Two hundred ninety-eight children entered the study between February
6 and April 30, 1997. One child was not included in the analysis because the
child never started study therapy due to an illness (Figure 1). Baseline patient characteristics (Table 1) were well balanced among the treatment groups. The 11 children
with prior stavudine experience who entered the study were equally distributed
among the treatment arms. The median duration of follow-up was 12.7 months,
varying between 12.4 and 12.8 months for the 3 treatment groups.
The week 12 interim analysis of the first 136 children enrolled was
conducted on August 11, 1997. This analysis showed that the proportion of
children whose HIV RNA copy number reached an undetectable level (<400
copies/mL) in the zidovudine and lamivudine group (14% [6/43]) was significantly
less than in the 2 ritonavir-containing treatment groups (61% [28/46] in the
triple-therapy group and 57% [27/47] in the dual-therapy ritonavir group; P<.001 for both comparisons). Based on this interim
analysis, children in the zidovudine and lamivudine group with HIV RNA levels
greater than 10,000 copies/mL were offered combination ritonavir, nevirapine,
and stavudine treatment identified as the step 2 phase of the study; children
who had HIV RNA levels of up to 10,000 copies/mL continued taking their original,
randomized zidovudine and lamivudine treatment. Forty-eight children enrolled
in step 2; 25% (12/48) enrolled in step 2 between study weeks 30 and 36 of
their initial randomization, and the remainder enrolled after study week 36.
Therefore, analyses of the zidovudine and lamivudine group patients in this
article are only included through study week 24 (when all patients were still
receiving their original, randomized treatment).
The overall week 12 analysis results are presented in Table 2. At study week 12, 12% of the zidovudine plus lamivudine
group had undetectable plasma HIV RNA compared with 52% and 54% of those in
the 2- and 3-drug ritonavir-containing arms, respectively (P<.001). The proportion of children (taking initial treatment) at
study week 24 who had HIV RNA below the level of assay quantification was
8% (8 of 95) for the zidovudine and lamivudine group, 34% (31 of 92) for the
stavudine and ritonavir group, and 47% (44 of 93) for the triple-therapy group.
The pairwise differences between the zidovudine and lamivudine group and the
other 2 treatment groups at study weeks 4, 12, and 24 were statistically significant
(P<.001). For children in the 2 ritonavir-containing
study arms, the differences between these 2 groups at study weeks 4, 12, 24,
and 36 were not statistically significant. However, a significant difference
was observed at study week 48. The proportion of children receiving initial
treatment at study week 48 with HIV RNA below the level of quantification
was 27% (25 of 92) for the stavudine and ritonavir group and 42% (39 of 93)
for the triple-therapy group (P = .04). At the same
time, the proportion of children with HIV RNA less than 10,000 copies/mL was
similar in both ritonavir-containing treatment groups (P = .19).
We analyzed whether baseline HIV RNA copy number, CD4 cell count, or
age were predictors of long-term virologic success in the ritonavir-containing
treatment groups. In those children continuing their initial treatment at
study week 48, only lower baseline HIV RNA copy number was associated with
a greater proportion of children achieving HIV RNA levels below quantification
(Table 3). Sixty-nine percent
of children with baseline HIV RNA between 2.6 and 3 log10 copies/mL
achieved RNA levels below quantification at study week 48 compared with only
19% of children with baseline HIV RNA between 5 and 6 log10 copies/mL.
There was no statistically significant association of baseline CD4 cell count
or age at study entry with virologic response (data not shown).
There was no difference in the median CD4 cell count for all 3 treatment
groups combined between study entry and week 24 (671 vs 744 × 106/L) (Figure 2). In the ritonavir-containing
study arms, median CD4 cell counts at week 48 for the children receiving stavudine
and ritonavir and those receiving triple therapy were 767 and 818 ×
106/L, respectively (P = .47). However,
there was a significant difference in CD4 percentage between the 2 ritonavir-containing
treatment groups at study week 48, with medians of 29% vs 33% for the 2-drug
vs 3-drug combinations (P<.01).
Overall, 72% of the children experienced a moderate (grade 2) or worse
toxic event while receiving initial therapy, and 21% experienced a severe
(grade 3) or worse toxic event. However, there were no significant differences
between the treatment groups with respect to the overall rates of toxicity.
The overall rate of severe or worse toxic effects was 22% for those receiving
zidovudine and lamivudine; 23% for the stavudine and ritonavir group; and
17% for the triple-therapy group. The most commonly observed adverse events
were nausea or vomiting (24%) (grade 2 or higher: >3 episodes of vomiting
per day, duration of >3 days, nausea resulting in decreased oral intake);
rash (19%) (grade 2 or higher: diffuse maculopapular rash, dry desquamation,
or worse); fever of 38.5°C or more (18%); and neutropenia (absolute neutrophil
count <750 × 106/L) (18%). Moderate or worse nausea or
vomiting was more frequent in children receiving triple therapy, compared
with those receiving zidovudine and lamivudine alone (Table 4). Neutropenia of a moderate or worse degree was less frequent
in children receiving stavudine and ritonavir than either of the study arms
that contained zidovudine.
Three reasons that children needed permanent discontinuation of their
initial randomized study treatments were: (1) HIV RNA greater than 10,000
copies/mL, (2) adverse events or intolerance, or (3) other nontoxicity or
virologic failure reasons. By study week 48, initial therapy had been discontinued
prematurely for 62% of patients in the zidovudine and lamivudine group, 35%
in the stavudine and ritonavir group, and 28% in the triple-therapy group
(Figure 3). While intolerance was
the most frequent reason for discontinuation of initial ritonavir therapy
by study week 4, by study week 48 the rates of discontinuation due to intolerance
were similar for the 3 treatment groups. Thirty-six percent of the 197 children
in the ritonavir-containing arms were receiving full-dose therapy, and 31%
were no longer receiving ritonavir at study week 48. Discontinuation of initial
treatment due to an increase in HIV RNA copy number after study week 12 was
not common in the zidovudine and lamivudine group until study week 36, at
which time it became the predominant reason.
This study was the first large, randomized clinical trial to evaluate
the use of ritonavir in HIV-infected children. Of the 297 evaluable children
who entered the study, 197 received ritonavir-containing antiretroviral treatment
regimens. After 12 weeks of therapy, a significant and sustained decrease
in HIV RNA copy number was observed in children changed from their previous
nucleoside analog antiretroviral therapy to a ritonavir-containing regimen.
Fifty-three percent of children who received a ritonavir-containing regimen
had HIV RNA levels below the limit of assay quantification at study week 12
compared with only 12% of children who had been randomized from their previous
regimen to the zidovudine and lamivudine study arm (P<.001).
Thus, changing from a single or dual nucleoside regimen to another dual nucleoside
regimen had little virologic benefit for clinically stable pediatric patients.
As a consequence, children randomized to the zidovudine and lamivudine study
arm who had HIV RNA levels of more than 10,000 copies/mL after study week
12 were changed to a protease-containing regimen (stavudine, nevirapine, and
ritonavir) in the step 2 phase of this study and are still undergoing follow-up.
After 48 weeks of therapy, 42% of the children receiving triple therapy
maintained HIV RNA levels below the limit of assay quantification, compared
with only 27% of children receiving dual therapy with ritonavir and stavudine.
This difference was not noted at study weeks 24 and 36. In addition, there
was no significant difference in the proportion of children with HIV RNA viral
number below 10,000 copies/mL between the 2 ritonavir-containing treatment
groups at study week 48. These data suggest that dual therapy including ritonavir
has comparable activity to triple therapy including ritonavir in terms of
moderate reduction in HIV RNA copy numbers (to levels <10,000 copies/mL)
but that triple therapy with ritonavir was superior to dual therapy in maintaining
HIV RNA copy numbers below the level of assay quantitation. Although initial
evaluation at week 24 suggested that the 2-drug combination of stavudine and
ritonavir was as effective as zidovudine, lamivudine, and ritonavir in effecting
an undetectable viral load, this outcome did not appear to be fully sustained
when a longer interval (48 weeks) was examined. It is important to note that
even triple therapy was less than 50% effective in maximally suppressing the
viral load. It is difficult to evaluate the effect of therapy on clinical
outcomes, as few outcome events had occurred by 48 weeks. The effect of treatment
must therefore be evaluated over extended periods before definitive conclusions
can be drawn regarding any comparisons of highly active antiretroviral therapies.
There were no cases of Pneumocystis carinii pneumonia
reported during the study period. One case of cytomegalovirus disease was
reported in the stavudine plus ritonavir treatment group and none in any of
the other treatment groups.
Several reasons may have contributed to the relatively low success rate.
First, children tend to have higher plasma HIV RNA levels than adults,15 and the higher the viral load, the lower the success
rate appears. Second, although more than two thirds of the children were still
taking their initially assigned ritonavir-containing treatment at study week
48, only half of them were still receiving the full dose of ritonavir, and
resistant virus may have been present. Third, all these children were antiretroviral-treatment
experienced and often only changed 2 drugs, not 3. Fourth, adherence to multiple-drug
regimens is difficult in children. These factors may have contributed to the
overall lower success rates when compared with adult antiretroviral trials.
There were no significant differences in absolute CD4 cell counts after
48 weeks of therapy between the 2 ritonavir-containing regimens; however,
a greater increase in CD4 percentage was seen in children receiving triple
therapy. This discrepancy between CD4 cell count and percentage suggests that
CD4 percentage may be a more sensitive or accurate measure of immune response
to antiretroviral therapy than absolute CD4 cell count when nucleoside analog
therapy suppresses white blood cell counts over time. Another potential reason
for the lack of a significant change in CD4 cell number between treatment
regimens is that many children entered the study with absolute CD4 cell counts
that were already normal for age (the median age at entry was approximately
7 years, and the median entry CD4 cell count in the study arms was 644 to
693 × 106/L; normal for this age group is >500 × 106/L). Additional studies are needed to investigate the importance of
more specialized phenotypes within the larger CD4 cell group.
Ritonavir was relatively well tolerated by the children in this study.
Seventy percent continued taking ritonavir for the 48 weeks of the study.
While nausea and vomiting appeared to be the most common adverse effect in
the ritonavir arms, taste was the biggest obstacle for the health care providers.
To increase the palatability of the ritonavir, coating the mouth with peanut
butter or with chocolate or vanilla pudding or applying ice chips were recommended.
In many cases, these methods or others devised at individual sites were effective
in permitting successful drug administration. When possible, capsules were
substituted for the liquid formulation. A few children able to tolerate ritonavir
early in the study were unable to tolerate it weeks or months later. Other
toxic events noted in the study included fever and skin rash, which appeared
at approximately the same rates in all 3 treatment groups, and neutropenia,
which appeared more commonly in the zidovudine and lamivudine treatment arms.
There were no differences overall in the rate of grade 3 or 4 toxic events
across all treatment groups.
Baseline HIV RNA copy number was an important prognostic factor in virologic
response to therapy. Sixty-nine percent of children who entered the study
with HIV RNA levels under 1000 copies/mL achieved HIV RNA levels below the
limit of assay quantitation by study week 48, compared with only 19% of children
who entered with baseline HIV RNA levels greater than 100,000 copies/mL. A
similar finding has been reported in HIV-infected adults16
but was not observed in a smaller study in children.17
These data suggest that change in antiretroviral therapy in children should
be considered when HIV RNA levels are only moderately elevated, rather than
waiting until HIV RNA levels become excessively high.
This study demonstrated that ritonavir-containing treatment regimens
have potent antiviral effects, and, therefore, children who are nucleoside-experienced
should be switched to a protease inhibitor–containing treatment regimen
to successfully decrease their viral load. To extend the durability of the
viral load suppression, 2 nucleosides instead of 1 should be part of the combination.
Ritonavir was generally well tolerated and associated with a toxicity profile
commonly seen with protease inhibitor therapy. While there appeared to be
some late-onset problems with intolerance, 70% of children continued their
ritonavir-containing treatment through study week 48. Protease inhibitor–containing
combination therapy should be viewed as part of the standard therapy for children
with HIV disease.