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Efficacy and Safety of Darunavir/Ritonavir at 48 Weeks in Treatment-naïve, HIV-1–infected Adolescents

Results From a Phase 2 Open-label Trial (DIONE)

Flynn, Patricia MD*; Komar, Svitlana MD; Blanche, Stephane MD; Giaquinto, Carlo MD§; Noguera-Julian, Antoni MD, PhD; Welch, Steven MRCPCH; Lathouwers, Erkki MSc**; Van de Casteele, Tom PhD**; Kakuda, Thomas N. PharmD††; Opsomer, Magda MD**

Author Information
The Pediatric Infectious Disease Journal: September 2014 - Volume 33 - Issue 9 - p 940-945
doi: 10.1097/INF.0000000000000308
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Abstract

Darunavir is an HIV-1 protease inhibitor (PI) with demonstrated sustained efficacy and a favorable safety and tolerability profile in a wide range of treatment-experienced patients.1,2 Darunavir is approved for use in combination with low-dose ritonavir and other antiretroviral agents for treatment of HIV-1 infection in treatment-naïve and treatment-experienced adults.3,4 Twice-daily darunavir/ritonavir is also indicated for use in combination with other antiretrovirals in treatment-experienced pediatric patients at least 3 years of age,5 based on the findings of the phase 2 DELPHI (Darunavir EvaLuation in Pediatric, HIV-Infected, treatment-experienced patients; TMC114-C212; NCT00355524) and ARIEL (dArunavir in tReatment experIenced pEdiatric popuLation; TMC114-TiDP29-C228; NCT00919854) trials.6,7

In the DELPHI trial, weight-adjusted darunavir/ritonavir twice daily, combined with other antiretrovirals, demonstrated a favorable safety/tolerability profile and a significant virologic response in treatment-experienced children and adolescents (6 to <18 years).6 Weight-adjusted darunavir/ritonavir twice daily also showed good efficacy with no new safety concerns in treatment-experienced pediatric patients 3 to <6 years of age (ARIEL).7

Although darunavir/ritonavir is indicated for use in treatment-experienced pediatric patients, the efficacy and safety of once-daily darunavir/ritonavir in treatment-naïve pediatric patients has not been established. Furthermore, limited clinical trial data exist for once-daily treatment options in the pediatric patient population. DIONE (DarunavIr Once-daily in treatment-Naïve adolescents; TMC114-TiDP29-C230; NCT00915655) evaluated the pharmacokinetics, safety, tolerability and antiviral activity of an 800/100 mg darunavir/ritonavir once-daily dose in treatment-naïve adolescents.

METHODS

Study Population and Design

DIONE was a phase 2, 48-week, open-label, single-arm study in treatment-naïve, HIV-1–infected adolescents. The study consisted of a screening period of 4 weeks, a 48-week treatment period and a 4-week follow-up period. Patients received once-daily darunavir/ritonavir 800/100 mg in combination with a background regimen of 2 nucleoside reverse transcriptase inhibitors (NRTIs), either zidovudine/lamivudine or abacavir/lamivudine.

Main inclusion criteria were: antiretroviral treatment-naïve adolescents ≥12 to <18 years of age, weighing ≥40 kg, with a screening HIV-1 RNA plasma viral load ≥1000 copies/mL. Patients were excluded if they had primary or acute HIV-1 infection, had life expectancy <6 months, were pregnant or breast-feeding, had any active clinically significant disease or presented with any active conditions included in the World Health Organization listing of Clinical Stage 4.8

The study protocol was reviewed and approved by the appropriate institutional review board or ethics committee(s) and health authorities, and the study was conducted in accordance with the Declaration of Helsinki. All patients were informed and asked whether they wished to participate. Parents or legal representatives and patients (as appropriate) provided consent.

Efficacy Analyses

The primary and final analyses were performed at weeks 24 and 48, respectively (when all patients had been treated for 24 or 48 weeks, respectively, or discontinued earlier). The primary efficacy endpoint was viral load <50 copies/mL at week 24 [intent-to-treat (ITT)-time-to-loss of virologic response (TLOVR) algorithm]. Plasma viral load levels were determined using the Amplicor HIV-1 monitor test (Roche Diagnostics).

Secondary efficacy evaluations included: viral load <50 copies/mL at week 48 [ITT-TLOVR, noncompleter = failure (NC = F), observed case and TLOVR nonvirologic failure (non-VF) censored analyses); viral load <400 copies/mL; ≥1 log10 viral load change from baseline (NC = F)]; Food and Drug Administration “snapshot” analysis at weeks 24 and 48 and change in CD4+ cell count at weeks 24 and 48.

Pharmacokinetic Analyses

Blood samples were collected from all patients for assessment of darunavir and ritonavir plasma concentrations. Two sparse samples were collected, at least 1 hour apart, at weeks 4, 24 and 48. At week 2, rich (intensive) sampling was performed predose and 1, 3, 6, 12 and 24 hours postdose. Plasma darunavir and ritonavir concentrations were determined using a previously validated high performance liquid chromatography with tandem mass spectrometry method with a lower limit of quantification of 5.00 ng/mL for both compounds.9

Population pharmacokinetic parameters for darunavir [area under the concentration-time curve from time 0 to 24 hours (AUC0–24h) and plasma concentration at 0 hours (C0h)] were estimated from the rich and sparse blood sampling. The 2-compartment pharmacokinetic model with first-order absorption in adults was adjusted to accommodate the difference in exposure after administration of the clinical trial formulation and the commercial tablet formulation.10 This model was then further adjusted to accommodate data from children 3 to <18 years of age receiving twice-daily darunavir in the ARIEL, DELPHI and the DUET studies and once-daily darunavir intake based on inclusion of data from the ARIEL substudy and DIONE.11 Antiviral activity and safety parameters were subjected to a pharmacokinetic/pharmacodynamic analysis.

Adherence

Antiretroviral medication adherence was assessed using the Study Adherence Questionnaire, developed by The Paediatric European Network for Treatment of AIDS,12 and pill counts based on self-returned medication at each visit. Adherent patients were defined as those who did not miss any darunavir/ritonavir dose (or of the background regimen) in the 3 days before the timepoint of interest, as stated by the caregiver or patient, or those taking >95% of pills, both for darunavir and ritonavir.

Resistance Analyses

Resistance determinations (genotyping/phenotyping) were performed at screening (genotyping only), baseline, week 24, week 48 and at early withdrawal, if the viral load was ≥1000 copies/mL. Attempts were made for extra post-baseline resistance determinations of patients experiencing VF, even if the viral load was between 50 and 1000 copies/mL. Viral phenotypic and genotypic determinations were performed using the Antivirogram and Virco Type HIV-1 assays (Janssen-Virco, Beerse, Belgium), respectively.

Safety Analyses

Safety analyses were performed on the ITT population. At each visit, patients and caregivers provided information on adverse events (AEs)/HIV-1–related events. Investigators assessed the relationship of AEs to darunavir/ritonavir or background antiretrovirals. Based on known PI class effects,13,14 any rash-related, cardiac, gastrointestinal, pancreatic, liver-related, lipid-related, glucose-related and hematologic AEs were considered of special interest. Clinical laboratory data were also collected at each visit. Descriptive statistics were generated for all tests performed (actual values and changes from baseline). Additionally, laboratory abnormalities were calculated according to the Division of AIDS severity list.15

Sample Size and Statistical Analyses

Based on a standard deviation (SD) for log-transformed darunavir AUC0–24h of 0.26 in treatment-naïve adults,16 for a sample size of 12 patients, the observed mean AUC0–24h was estimated as 87.2–114.6% of the true mean AUC0–24h with 90% confidence. Similarly, based on a SD for log-transformed C0h of 0.49, the observed mean C0h was estimated as 77.5–129.0% of the true mean C0h with 90% confidence. Assuming a true primary endpoint response (<50 copies/mL, ITT-TLOVR) rate of 75% at week 24, a sample size of 12 patients would yield a 2-sided 95% confidence interval for virologic response of 49–100%. Finally, assuming a true likelihood of AEs occurring at 5% and 10%, the probability of observing ≥1 event in this sample size is 46% and 72%, respectively.

RESULTS

Baseline Characteristics and Patient Disposition

Participants were recruited from 6 centers in France, Italy, Spain, Ukraine, United Kingdom and United States. Twelve patients were screened and all were treated and completed the study, including the week 4 follow-up visit; there were no discontinuations. Median treatment duration was 48.5 weeks.

Baseline characteristics are shown in Table 1. Half the patients were recruited in Ukraine. No patients harbored any virus with primary (major) PI or NRTI resistance-associated mutations (RAMs). The median number of International AIDS Society-US PI RAMs17 was 4 (range 1–6). One patient harbored virus with a single darunavir RAM (V11I) at baseline. Phenotypic data indicated that all patients were susceptible to all commercially available PIs (including darunavir) and NRTIs, including those used in the background regimens.

TABLE 1
TABLE 1:
Patient Baseline Demographics and Disease Characteristics

Virologic Response

The primary endpoint was virologic response defined as the percent of patients with a confirmed viral load <50 copies/mL (ITT-TLOVR) at week 24. The response to treatment increased progressively over time until week 24 when 92% (11/12) had a confirmed virologic response (Fig. 1). The median time to virologic response was 16 weeks. At week 48, 10 patients (83%) had a confirmed virologic response (Fig. 1). Week 48 sensitivity analyses demonstrated that virologic response was consistent across the different imputation methods [observed case (92%), NC = F (92%) and TLOVR non-VF censored (83%) analyses]. With the Food and Drug Administration “snapshot” algorithm, at week 24 and week 48, virologic response was achieved by 100% and 92% of patients, respectively.

FIGURE 1
FIGURE 1:
Proportion of patients (mean ± SE) achieving viral load <50 copies/mL (ITT-TLOVR) over 48 weeks after treatment with darunavir/ritonavir 800/100 mg once daily plus zidovudine/lamivudine (n = 6) or abacavir/lamivudine (n = 6).

At week 24, 100% of patients had a confirmed viral load <400 copies/mL (ITT-TLOVR). At week 48, this suppression was maintained in 92% (11/12) of patients. Furthermore, at weeks 24 and 48, all patients had a confirmed ≥1 log10 decrease in plasma viral load versus baseline. At week 48, the overall decrease from baseline in mean [standard error (SE)] log10 plasma viral load (NC = F) was 2.98 (0.182) log10 copies/mL.

Immunologic Response

At week 24, the mean (SE) increase in CD4+ cell count from baseline was 175 (19.5) cells/mm3 and the median (range) percent of CD4+ cells increased from baseline by 10% (−1% to 16%). At week 48, there was a further increase in mean (SE) CD4+ cell count from baseline to 221 (22.4) cells/mm3. At this timepoint, the median (range) percent of CD4+ cells had increased from baseline by 14% (−4% to 19%).

Resistance Analysis

The patient with the darunavir V11I RAM at baseline had a confirmed virologic response (ITT-TLOVR) from week 16, which was maintained through to week 48. One patient was never suppressed (ITT-TLOVR) and had an unconfirmed viral load <50 copies/mL at week 24, but had a viral load >50 copies/mL thereafter. This patient had a treatment-emergent primary PI mutation (M46I). From the adherence data (questionnaire and pill count), this patient was nonadherent from week 24 onwards for darunavir/ritonavir and abacavir/lamivudine. In addition, 1 patient was a viral rebounder (confirmed ≥50 copies/mL, after response) at week 40. The viral loads for this patient were 2610, 10,300 and 175 copies/mL at weeks 40, 42 and 43, respectively. At week 48, the viral load was undetectable (<50 copies/mL). This patient was adherent to antiviral medication throughout the study. A treatment-emergent NRTI RAM (K219Q) was detected. Both of these patients remained susceptible to all commercially available PIs (including darunavir) and NRTIs, including those in the background regimen (abacavir and lamivudine for the never-suppressed patient; zidovudine/lamivudine for the rebounder), except for tenofovir disoproxil fumarate (the rebounder).

Pharmacokinetic Analyses

The geometric mean (SD) darunavir AUC0–24h at week 48 was 80.7 (23.6) μg·h/mL, 90.0% of the target adult exposure [geometric mean of 89.7 μg·h/mL in adults in ARTEMIS (AntiRetroviral Therapy with TMC114 ExaMined In naive Subjects; TMC114-C211; NCT00258557)].18 The geometric mean (SD) darunavir C0h was 1.93 (0.87) μg/mL. The mean (SD) plasma concentration-time profile for darunavir is illustrated in Fig. 2. No apparent relevant relationships were observed between darunavir AUC0–24h or C0h and virologic response or change in log10 viral load from baseline at week 48 (data not shown). Furthermore, no apparent relevant relationships were observed between darunavir AUC0–24h or C0h and the occurrence of AEs of clinical interest (data not shown).

FIGURE 2
FIGURE 2:
Mean (SD) plasma concentration-time profile of darunavir at week 2.

Adherence

By pill count, 7 patients (58%) were adherent (>95%) and 5 patients (42%) were nonadherent (≤95%) to darunavir/ritonavir. By the Study Adherence Questionnaire, 10 patients (83%) were adherent to darunavir/ritonavir and 11 patients (92%) were adherent to the antiretrovirals in the background regimen.

Safety and Tolerability

Over 48 weeks, 11 patients (92%) experienced at least 1 AE; the most frequent AEs were vomiting (4/12, 33%), anemia (3/12, 25%) and nausea (3/12, 25%; Table 2). No AEs led to treatment discontinuation. Grade 3 or 4 AEs occurred in 3 patients (25%), the most common of which was anemia (2 patients). All other grade 3 or 4 events occurred in 1 patient. Four patients (33%) experienced at least 1 serious AE. Three serious AEs were grade 4 (both anemia cases and 1 case of neutropenia), and 2 SAEs were grade 2 (cervical dysplasia and traumatic brain injury). One SAE (anemia) was considered to be doubtfully related to darunavir/ritonavir and the other 4 SAEs were considered not related to darunavir/ritonavir. The hematologic AEs were attributed by the investigator to zidovudine.

TABLE 2
TABLE 2:
Overview of AEs and Laboratory Abnormalities

AEs at least possibly related to darunavir were reported in 2 patients (17%); 1 patient had 2 AEs (grade 1 nausea and vomiting) and the second patient had 4 AEs (grade 2 abdominal pain, diarrhea and nausea; grade 1 dizziness; Table 2). Grade 2–4 treatment-emergent, lipid- and glucose-related laboratory abnormalities were observed for total cholesterol, low-density lipoprotein and high-serum glucose under fasting conditions (Table 2). There were no clinically or statistically significant changes in vital signs during the study and no treatment-emergent electrocardiogram abnormalities.

DISCUSSION

Management of HIV-1–infected adolescents is clinically challenging. For example, these patients require help adjusting to their HIV status and in adhering to their antiretroviral regimens.4,5 Medication adherence is a challenge among adolescents,19,20 with several factors (eg, pill burden, irregular routines, lack of familial and social support, depression and alcohol or substance abuse) contributing to nonadherence.21 Therefore, dosing regimens that potentially improve treatment adherence are needed for this demographic.

Current HIV treatment recommendations for adolescents generally follow adult guidelines, although data in this population are limited,4 partly because of the perception that clinical trials are too burdensome and complex. However, in observational studies, adolescents usually have higher rates of VF and are less likely to achieve virologic suppression than young adults.22–25 Nevertheless, some studies demonstrated greater immunologic responses in adolescents versus young adults (which may reflect greater thymic productivity)26,27 and similar mortality in the 2 groups.

Few studies have compared antiretroviral regimens in children and adolescents. At 4 years, the PENPACT-1 study showed no significant differences in virologic, immunologic or clinical outcomes between non-nucleoside reverse transcriptase inhibitor and PIs as first- and second-line agents in pediatric patients 30 days to 18 years of age.28 More studies are needed to evaluate PIs in children and adolescents.

In DIONE, the efficacy and safety of an 800/100 mg darunavir/ritonavir once-daily dose was demonstrated in HIV-1–infected adolescents ≥12 to <18 years of age. Virologic response increased progressively to week 24, and most patients maintained this response at week 48. Although a virologic response occurred in all of the viral clades, the number of patients in DIONE is too small to draw conclusions about virologic response verus clade. In treatment-naïve adults in ARTEMIS, darunavir/ritonavir was efficacious irrespective of the HIV-1 subtype.29 The virologic response rate in DIONE, albeit in a small number of patients, is comparable with that in ARTEMIS, where 84% of treatment-naïve adult patients had a confirmed virologic response after 48 weeks of receiving 800/100 mg darunavir/ritonavir once daily.16 The immunologic response in DIONE also compares favorably with that in ARTEMIS.16

As expected, baseline resistance and VF frequency was very low in treatment-naïve adolescents, hence the influence of baseline genotypes on virologic response could not be evaluated in DIONE. However, no patients developed darunavir RAMs or lost phenotypic susceptibility to any commercially available PI (including darunavir) or any NRTI in the background regimens. This finding is consistent with data in treatment-experienced pediatric and adult patients where a diminished virologic response only occurred in those with at least 3 darunavir RAMs6,16,30 and is consistent with the high genetic barrier of darunavir to resistance development.31

Adherence in DIONE, by self-report questionnaire, was comparable with adherence in the ≥12- to <18-year- old patient subgroup in the DELPHI trial and in adults in ARTEMIS (83% in both DELPHI6 and ARTEMIS).32 In addition, consistent pharmacokinetic results were obtained in adolescents compared with in adults (geometric mean darunavir AUC0–24h 80.7 vs. 89.7 μg·h/mL).18 No apparent relationships were observed between the darunavir pharmacokinetic parameters AUC0–24h or C0h and virologic response or the change in log10 viral load from baseline over 48 weeks. Additionally, no apparent relationships were observed between darunavir AUC0–24h or C0h and the occurrence of AEs of interest. However, these results should be viewed with caution as there were only a small number of patients in DIONE. This lack of a dose-response relationship in adolescents may indicate that exposure in many DIONE patients is on the plateau of the dose-response curve. This is also true of once-daily and twice-daily darunavir pharmacokinetic results obtained in adult populations.30

No new safety findings were reported in DIONE. The safety data are in line with the known safety profile of once- and twice-daily darunavir/ritonavir in treatment-naïve and -experienced HIV-1–infected adults and treatment-experienced children aged 6 to <18 years.6,16,26 Although a quarter of patients experienced a hematologic AE, all of these patients were also receiving zidovudine, which is known to be associated with hematologic abnormalities.33

The main limitation of this single-arm, open-label study is its relatively small sample size, with half the participants from the same institution. However, the consistency of our findings compared with previous darunavir trials provides some additional reassurance of their validity.6,7,14 A second limitation is that only 2 background regimens were used in this study (zidovudine/lamivudine and abacavir/lamivudine). However, darunavir/ritonavir has demonstrated similar efficacy and safety with a number of other antiretroviral backgrounds,2,27 suggesting that these findings can be translated to other background regimens.

In conclusion, once-daily darunavir/ritonavir in combination with a background regimen of 2 NRTIs demonstrated sustained efficacy over 48 weeks in treatment-naïve, HIV-1–infected patients aged 12 to <18 years. Additionally, darunavir/ritonavir was well-tolerated, indicating that darunavir/ritonavir may be safely and effectively administered as an 800/100 mg once-daily dose to adolescent patients. These findings support the use of darunavir/ritonavir 800/100 mg once daily in this treatment-naïve, HIV-1–infected adolescent patient population.

ACKNOWLEDGMENTS

The authors would like to thank the patients and their families for their participation and support during the studies; the DIONE Janssen study team, the study center staff and principal investigators; F. Tomaka, E. Wong and the Janssen PREZISTA team for their input into this article. This study was sponsored by Janssen Research and Development. Medical writing support assistance in coordinating and collating author contributions was provided by J. Gregson of Gardiner-Caldwell Communications, Macclesfield, United Kingdom; this support was funded by Janssen.

Authors’ contributions: All authors substantially contributed to the study’s conception, design and performance. P.F., S.K., S.B., C.G., A.N.-J. and S.W. all participated in recruiting patients and reported data for those patients. E.L. made a significant contribution to the virology analyses and data interpretation. TvdC as a clinical statistician was involved in all data analyses. T.N.K. had significant involvement in the pharmacokinetic analyses and data interpretation. M.O. was the trial physician of the study. All authors were involved in the development of this article, interpretation of the data, have read and approved the final version and have met the criteria for authorship as established by the ICMJE.

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    Keywords:

    adolescents; darunavir; HIV-1; ritonavir; treatment-naïve

    © 2014 by Lippincott Williams & Wilkins, Inc.