Objectives: TMC310911 is a novel HIV type-1 (HIV-1) protease inhibitor with broad in vitro antiviral activity. In this phase 2a, open-label randomized study, the antiviral activity, pharmacokinetics, and safety and tolerability of ritonavir-boosted TMC310911 was assessed.
Methods: In this study, treatment-naive HIV-1 patients (aged 18–60 years) received 1 of the 4 dosing regimens of TMC310911: 150 mg twice-daily (bid) (n = 8), 300 mg bid (n = 8), 75 mg bid (n = 9), or 300 mg once-daily (qd) (n = 8), for 14 days, all coadministered with 100 mg of ritonavir, as only antiretroviral therapy.
Results: The mean change from baseline in HIV-1 RNA (log10 copies per milliliter; primary efficacy endpoint) was −1.30 (75 mg bid), −1.14 (150 mg bid), −1.07 (300 mg bid), and −1.06 (300 mg qd) on day 8 and −1.53 (75 mg bid), −1.79 (150 mg bid), −1.69 (300 mg bid), and −1.55 (300 mg qd) on day 15. At steady state (day 14), the mean maximum plasma concentration and mean area under the plasma concentration–time curve from 0 to 12 hours tended to increase dose proportionally for bid doses; TMC310911 daily exposures for the 300 mg qd treatment and 150 mg bid treatment were comparable. The most common (≥10%) treatment-emergent adverse events were fatigue (27.3%) and nausea (12.1%); no deaths or serious treatment-emergent adverse events were reported in this study.
Conclusions: Combination treatment with TMC310911 and ritonavir showed potent antiviral activity (>1.5 log10 copies/mL decrease in plasma HIV-1 RNA) at all evaluated doses, and treatment was generally safe and well tolerated.
*ICH Study Center, Hamburg, Germany;
†EPIMED, Vivantes Auguste-Viktoria Klinikum, Berlin, Germany;
‡Department of Infectious Diseases and Pulmonary Medicine, Charité-Universitätsmedizin Berlin, Berlin, Germany;
§Goethe-University Hospital/Medical Center-Infectious Diseases-Unit, Frankfurt, Germany;
‖Research and Early Development Department, Janssen Infectious Diseases BVBA, Beerse, Belgium;
¶Department of General Practice, Katholieke Universiteit Leuven, Leuven, Belgium; and
#Department of Infectious Diseases, Janssen Research & Development, High Wycombe, Buckinghamshire, United Kingdom.
Correspondence to: René Verloes, MD, Janssen Infectious Diseases, Turnhoutseweg 30, Beerse B2340, Belgium (e-mail: email@example.com).
Supported by Janssen Research & Development, Ireland (previously known as Tibotec Pharmaceuticals Ltd.). Sponsor also provided formal review of manuscript.
H-J.S., K.A., D.S., and C.S. were investigators for this study. H-J.S. is the Director of the ICH Study Center, Hamburg, Germany, and has been an advisory board member and consultant for Abbott, Gilead Sciences, ViiV Healthcare, Boehringer Ingelheim, Merck Sharp & Dohme, Janssen-Cilag and Bristol-Myers Squibb; K.A. is the CEO of EPIMED and Director of the Clinic for Internal Medicine in the Vivantes Auguste-Viktoria-Klinikum, Berlin, Germany. D.S. is an employee of Charité-Universitätsmedizin Berlin, Germany. C.S. is Internal Medicine/Infectious Diseases Consultant at Goethe-University Hospital/Medical Center-Infectious Diseases-Unit, Frankfurt, Germany; he has received travel grants and speaker's honoraria from Janssen Research and Development LLC, Ireland. I.D., I.S., R.M.W.H., C.T., P.M., B.J., K.M., K.S., and R.V. are employees of Janssen Research & Development.
H-J.S., K.A., D.S., and C.S. were investigators for this study and were involved in study conduct. I.D., R.M.W.H., I.S., K.S., and R.V. were involved in study design; R.M.W.H. was also involved in interpretation of data; K.M. was involved in the study conduct; B.J. was the project leader and P.M. and C.T. were involved in analysis and interpretation of the data. All authors met International Committee of Medical Journal Editors criteria and all those who fulfilled those criteria are listed as authors. All authors approved submission to the journal.
The study is registered at ClinicalTrials.gov (NCT00838162).
Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's Web site (www.jaids.com).
Received June 19, 2013
Accepted September 09, 2013
Inhibition of HIV type-1 (HIV-1) proteases has been an important strategy for blocking progression of HIV-1 infection.1,2 This has led to the development and wide spread use of several protease inhibitors (PIs) as antiretroviral therapy (ART). Since their discovery in early 1990s, PIs have contributed to a dramatic decline in HIV-related mortality and morbidity; PIs are the key components of some of the most active combinations of antiretroviral drugs used in HIV therapy.
As low drug bioavailability is frequently observed for PIs, ritonavir, the HIV PI known to improve the pharmacokinetic (PK) profile and bioavailability of other drugs,3–5 is generally coadministered with other PIs.6 Although the ritonavir-boosted PI therapies provide a robust treatment option, their long-term use may still be confronted by development of resistance.7,8 Also, high pill burden associated with some first-generation PIs can lead to poor adherence, consequent loss of virus suppression, and subsequent disease progression in patients.9,10 Therefore, to overcome some of these limitations, the availability of novel PIs in HIV clinical development remains important.
The newly introduced second-generation ARTs focus on having a high genetic barrier to development of resistance, a concept especially important for PIs.11 Despite the success of these novel ARTs and treatment regimens, development of cross-resistance between different PIs and poor drug tolerability remain challenges in successful HIV-1 treatment.12
TMC310911 is a novel HIV-1 PI that has shown marked in vitro antiviral activity against both wild-type HIV-1 and a broad panel of HIV-1 recombinant clinical isolates, including multi-PI–resistant strains with decreased susceptibility to currently approved PIs.12 In addition, in vitro resistance selection with HIV-1 in the presence of TMC310911 caused a very limited emergence of strains carrying mutations leading to resistance.12 The broad activity on multi-PI–resistant strains and high genetic barrier makes TMC310911 a promising candidate for HIV therapy of both treatment-naive and PI-experienced patients.
The phase 1 studies of TMC310911 in healthy volunteers showed linear PK following single-dose and multiple dose administrations; systemic exposure to TMC310911 was 40% higher when administered under fasted conditions. Coadministration of low-dose ritonavir substantially increased the systemic exposure to TMC310911 in these studies. TMC310911 was found to be generally safe and well tolerated in healthy volunteers; no dose-limiting toxicity was observed up to 2000 mg (Hoetelmans et al, manuscript in preparation). We report here findings from the phase 2, open-label randomized study in treatment-naive HIV-1 patients, that assessed antiviral activity, plasma PK, and safety and tolerability of 4 different dosage regimens of TMC310911, coadministered with low-dose (100 mg) ritonavir.
Participants were 18–60 years of age (inclusive), had HIV-1 infection for ≥6 months before screening, had not been treated with a therapeutic HIV vaccine within 1 year before enrollment, and never been treated with a drug indicated for the treatment of HIV infection or a drug with anti-HIV activity indicated for the treatment of hepatitis B infection. All patients had a plasma viral load of >5000 HIV-1 RNA copies per milliliter and CD4+ cell count >200 cells per cubic millimeter and did not start ART before the baseline visit. Major exclusion criteria included HIV-2 infection, hepatorenal disease, life expectancy of <6 months, acute HIV-1 infection, preexisting HIV PI drug resistance,13 active AIDS-defining illness [Category C conditions according to the Centers for Disease Control and Prevention (CDC) Classification System for HIV Infection 1993] except stable cutaneous Kaposi's sarcoma, and wasting syndrome due to HIV infection (if not actively progressive) or any active clinically significant disease. Women of childbearing potential were not included; all men except those who were vasectomized or used an acceptable method of contraception throughout the study.
Patients agreed to refrain from consuming beverages containing alcohol or quinine (24 hours before receiving the study drug until the last PK blood sample was collected) and grapefruit (7 days before receiving the study drug until the last PK blood sample was collected). Additionally, patients refrained from strenuous exercise, extreme exposure to the sun, and use of tanning devices throughout the study.
Patients were not allowed to take cytochrome P450 enzyme 3A (CYP3A) inducers before starting the study drug treatment and also throughout the study; CYP3A and CYP2D6 substrates were not allowed during the treatment phase of the study.
The study was conducted in accordance with the ethical principles that have their origin in the Declaration of Helsinki and that are consistent with Good Clinical Practices, applicable regulatory requirements, and in compliance with the study protocol. The protocol was reviewed and approved by an independent ethics committee. All patients provided written informed consent before entering the study.
This open-label, randomized phase 2a study was conducted from April 27, 2009, to February 21, 2011, at 4 study centers in Germany. The study consisted of a 6-week screening period, 2-week treatment period, and a 4-week follow-up period. Enrolled patients were randomly assigned (1:1) using a central randomization system to receive either TMC310911 150 mg twice-daily (bid) or TMC310911 300 mg bid for 14 days. Two more treatment groups, 75 mg bid and 300 mg once-daily (qd) TMC310911 for 14 days were included following 2 protocol amendments. Patients in these 2 additional groups were not randomized. All doses of TMC310911 were administered under fed condition and were coadministered with 100 mg of ritonavir bid for 14 days, except the 300-mg qd TMC310911 group that received 100 mg of ritonavir qd for 14 days. Highly active ART could be started from day 15 onwards at the discretion of the investigator, in consultation with the patient, and according to local standard of care.
Patients were withdrawn from the study if they withdrew their consent, experienced a grade 3 or 4 treatment-emergent adverse event (TEAE) considered to be possibly related to study drug, experienced confirmed QTc prolongation >500 ms, or ≥60 ms change from baseline, or if they developed seizures.
TMC310911 (Janssen R & D, Cork, Ireland) was supplied as a solution of 25 mg/mL strength for oral use. Ritonavir (Norvir; Abbvie Laboratories, Abbott Park, IL) was supplied as capsules or film-coated tablets of 100 mg strength. Ritonavir capsules were used for patients in the TMC310911 75, 150, and 300 mg bid groups and ritonavir tablets were used for patients in the TMC310911 300 mg qd group.
The primary efficacy endpoint was the change in viral load from baseline, during a 14-day treatment period. The secondary efficacy endpoint of the study was changes in CD4+ cell count during the 14-day treatment period. Plasma viral load of patients was assessed at screening, 1 week before the start of study drug treatment, every day during the first 4 days of treatment [days 1 (baseline), 2, 3, and 4], every alternate day during the remaining period of treatment (days 6, 8, 10, 12, and 14), on day 15, after 1 to 2 weeks post last TMC310911 administration, and after 4 weeks post last TMC310911 administration during the follow-up period, using the Roche Amplicor HIV-1 monitor test (version 1.5).
Viral genotypic and phenotypic resistance determinations were performed at baseline and at the end of treatment using the vircoTYPE HIV-1 and Antivirogram assays (Janssen Diagnostics BVBA, Beerse, Belgium). Resistance determinations were typically performed at the end of the dosing period or withdrawal if viral load was >1000 HIV-1 RNA copies per milliliter; an attempt for resistance determination was made if viral load was <1000 HIV-1 RNA copies per milliliter. The development of a mutation was defined as the detection of a mutation by population sequencing at endpoint that was not detected at baseline. Loss of phenotypic susceptibility to an antiretroviral drug was defined as having a fold-change value above the biological/clinical cut-off of the Antivirogram at endpoint but not at baseline. The International AIDS Society–USA (IAS–USA) Drug Resistance Mutations13 were used as reference for determination of PI-associated resistance-associated mutations (RAMs).
Assessments for a Full Pharmacokinetic Profile
Blood samples were collected on day 1 and day 14 (predose and 0.5, 1, 2, 3, 5, 8, and 12 hours postdose) and on days 2, 3, 4, 6, 8, 10, and 12 (only predose). On day 15, following the last dose of TMC310911, blood samples were collected 12 hours postdose for the bid regimen groups and 24 hours postdose for the qd regimen group. Plasma samples were analyzed for concentrations of TMC310911 using validated liquid chromatographic mass spectrometry/mass spectrometry. The lower limit of quantification of TMC310911 was 1.00 ng/mL.
Pharmacokinetic parameters calculated from plasma concentration–time data included the following: predose plasma concentration (C0h), minimum plasma concentration (Cmin), maximum plasma concentration (Cmax), time to reach Cmax (tmax), and area under the curve (AUC) from 0 hours to the last measurable plasma concentration as calculated by the linear trapezoidal rule (AUClast). Additionally, average steady-state concentration (Css,av; calculated as AUCτ/τ at steady state, where τ = dosing interval) and fluctuation index (variation between maximum and minimum plasma concentration at steady state, calculated as 100 × [(Cmax−Cmin)/Css,av]) were estimated.
Safety assessments included monitoring for TEAEs (according to Division of AIDS grading scales14), clinical laboratory tests, vital signs, physical examinations, and electrocardiograms (ECG; in triplicate). Type and incidence of all HIV-related TEAEs were also recorded.
Based on the results from a previous study with nonnucleoside reverse transcriptase inhibitors, the intraparticipant standard deviation for the viral load reduction from baseline was assumed not to exceed 0.35 log10 copies per milliliter. At a 2-sided significance level of 5%, and with 8 patients in each group, the anticipated width of the 95% confidence interval was ±0.3 of the observed difference.
The intent-to-treat population was used for all efficacy and safety analyses and included all patients who received at least 1 dose of study drug. All data were summarized descriptively. Analysis of PK data was carried out at Kinesis Pharma B.V. (Breda, The Netherlands). Noncompartmental analysis was performed using WinNonlin Professional version 4.1 (Pharsight Corporation, Sunnyvale, CA). SAS version 9.1.3 (SAS Institute, Inc., Cary, NC) was used for all statistical calculations.
Patient Disposition and Baseline Characteristics
A total of 41 patients were screened, of which 33 were enrolled and received the TMC310911 treatment; all patients completed the study (see Figure S1, Supplemental Digital Content, http://links.lww.com/QAI/A467). All patients were white men except 1 white woman and 1 African man in the TMC310911 75 mg bid group. Median age of patients was 32 years (range: 22–49 years). The majority of patients (63.6%) had HIV-1 RNA levels between 10,000 and 100,000 copies per milliliter; median HIV-1 infection duration was 2.7 years (range: 0.4–11.4 years) (see Table S1, Supplemental Digital Content, http://links.lww.com/QAI/A467). At baseline, 51.5% patients had CD4+ cell count between 200 and 500 cells per cubic millimeter and the remaining patients (48.5%) had CD4+ cell count ≥500 cells per cubic millimeter. None of the patients were positive for hepatitis A, B, or C infection. The median number of PI RAMs as per the IAS–USA mutation chart13 was 3 (range: 1–6), but no primary PI mutations were detected at baseline. Twenty patients had ≥3 PI RAMs at baseline. The median number of nucleoside reverse transcriptase inhibitor and nonnucleoside reverse transcriptase inhibitor RAMs was 0.
A decrease in HIV-1 RNA versus baseline was observed from day 4 onwards in all treatment groups. On day 8, the mean change from baseline in HIV-1 RNA (log10 copies/mL) in the groups was −1.30 (75 mg bid), −1.14 (150 mg bid), −1.07 (300 mg bid), and −1.06 (300 mg qd), and on day 15, the respective changes were −1.53, −1.79, −1.69, and −1.55 (Fig. 1). During the follow-up period, HIV-1 RNA values increased for all patients except for 7 of the 8 patients who started highly active ART on day 15.
All patients except 1 from the 300 mg qd group had at least 1 log10 viral load drop from baseline by the end of the treatment. One patient in the 150 mg bid group had undetectable (<50 copies/mL) viral load on day 15. Viral load of <400 copies per milliliter on day 15 was recorded in 3 (33.3%) patients in the 75 mg bid group, 4 (50.0%) patients in the 150 mg bid group, 1 (12.5%) patient in the 300 mg bid group, and in none of the patients in the 300 mg qd group. On day 14, the highest response rate (proportion of patients with viral load <400 copies/mL) was observed in TMC310911 150 mg bid group (Fig. 1).
Mean (standard error) changes from baseline to day 15 in CD4+ cell count (× 106 cells/L) were −33.7 (27.04) in the 75 mg bid group, −2.8 (31.44) in the 150 mg bid group, −2.0 (41.23) in the 300 mg bid group, and 92.5 (58.70) in the 300 mg qd group.
Paired baseline/day 15 genotypes were available only for 18 patients (8 in the 75 mg bid, 1 in the 150 mg bid, 5 in the 300 mg bid, and 4 in the 300 mg qd group); in the remaining patients, resistance could not be determined because of too low viral load (<1000 copies/mL HIV RNA). In 1 patient in the 75 mg bid group, an emerging PI RAM was detected on day 15 (A71I/T on day 15 compared with A71T at baseline). There were no emerging primary PI mutations detected. Based on the phenotyping results, none of the 18 patients showed a decreased susceptibility to the 8 currently approved PIs or TMC310911 (Table 1). No differences were observed when individual log10 HIV-1 RNA profiles of patients with ≥3 PI RAMs at baseline were compared with profiles of patients with <3 PI RAMs at baseline.
On day 1 of treatment, the mean Cmax and the mean AUC from 0 to 12 hours (AUC12h) of TMC310911 increased in a less than dose proportional manner for the dose increases from 75 to 150 mg bid and from 150 to 300 mg bid. At steady state (day 14), the mean Cmax and the mean AUC12h tended to increase dose proportionally with increasing TMC310911 doses from 75 to 300 mg bid. On day 1 and at steady state, AUC12h was higher for the 300 mg qd dose regimen compared with the bid dose regimens. Daily exposure of TMC310911 at steady state (AUC24h) for the 300 mg qd treatment was comparable with the daily exposure (2 × AUC12h) of the 150 mg bid treatment (Table 2). On day 14 of treatment with TMC310911 in combination with ritonavir, the mean Cmax and mean AUC12h were highest for the 300 mg bid group and lowest for the 75 mg qd group (Fig. 2).
A total of 19 patients experienced at least 1 TEAE during the treatment period. Overall, the most common (≥10%) TEAEs were fatigue and nausea. Most of the TEAEs were grade 1 or 2 in severity (Table 3). No deaths or serious TEAEs were reported during the study. None of the TEAEs led to study discontinuation.
No clinically relevant changes were observed in clinical laboratory values. However, 2 patients (1 each from 150 mg bid and 300 mg qd groups) showed grade 4 transient increases in alanine aminotransferase and aspartate aminotransferase levels; the increases observed in patients from 150 mg bid group were considered to be possibly treatment related, whereas a transient CMV hepatitis was diagnosed by reverse–transcription polymerase chain reaction in the patient of the 300 mg qd group.
No clinically meaningful changes were recorded in vital signs or ECG parameters. During the study, none of the patients showed clinically significant changes in QTcF or QTcB (values >450 ms, or ≥30 ms increases from baseline in QTcF or ≥60 ms increases from baseline in QTcB). Seven patients showed QTcB increases from baseline between 30 and 60 ms [3 (33.3%) in 75 mg bid, 2 (25.0%) in 150 mg bid, 1 (12.5%) in 300 mg bid, and 1 (12.5%) in 300 mg qd group]; however, these increases were not clinically significant.
In this study, oral treatment of ritonavir-boosted TMC310911 for 14 days showed potent antiviral activity in the treatment-naive HIV-1 patients. A decrease in log10 HIV-1 RNA versus baseline was observed from day 4 onwards. All patients except 1 in the 300 mg qd group had at least 1 log10 drop in HIV-1 RNA from baseline during treatment. Previous in vitro studies have demonstrated potent antiviral activity [median 50% effective concentration (EC50) of 14 nM] of TMC310911 against wild-type HIV-1.12 The results of this study further underline the antiviral potency of TMC310911 and provide the first evidence of clinical effectiveness of TMC310911. Antiviral efficacy of TMC310911 was similar with bid and qd treatments as seen by the similar mean decreases from baseline in HIV-1 RNA across bid and qd treatment groups on day 8 and day 15. The maximum number of patients (50%) having a viral load of <400 copies per milliliter were in the 150 mg bid group; also, 1 patient in this group had undetectable viral load at the end of the treatment period.
An increase of CD4+ cell count was seen in patients in the 300 mg qd group, although a minimal decrease in CD4+ cell count was observed in patients in 150 mg and 300 mg bid groups. In view of small group sizes and high variability, the increase in CD4+ cell count observed in the 300 mg qd group and the minimal decrease in the other groups could represent inexplicable changes and should be interpreted with great caution, given the short duration of TMC310911 treatment in this study.
Increasing levels of resistance and cross-resistance that develop with successive failure of different currently approved PIs poses a major challenge for a successful HIV therapy. In the present study, based on the paired baseline/day 15 genotype data available from 18 patients, only 1 patient in the 75 mg bid group with the A71T polymorphism at baseline showed an emerging A71I/T PI RAM at day 15. A71T and A71I are minor resistance mutations, which by themselves do not have a substantial effect on phenotype.13 Based on the phenotyping results, none of the patients showed a decreased susceptibility to the currently approved PIs or TMC310911. These findings were in agreement with the previous in vitro findings with TMC310911 where it showed broad activity against multiple resistant viruses and a high genetic barrier to the development of resistance.
TMC310911 exhibited a linear PK profile at steady state, when coadministered with ritonavir for 14 days. Ritonavir, a known CYP450 3A4 inhibitor,4 improves PK profiles of PIs when administered concurrently.5 The PK properties of TMC310911 in this study should be interpreted taking the coadministration of ritonavir into consideration. The daily systemic exposure of TMC310911 at steady state (AUC24h) for the 300 mg qd treatment was comparable with the daily exposure (2 × AUC12h) of the 150 mg bid treatment, which is a favorable finding in terms of frequency of administration of TMC310911. The mean Cmin values for all treatment groups were above the target trough concentration of approximately 70 ng/mL of TMC310911 for treatment-naive and early treatment-experienced patients (based on antiviral activity corrected for protein binding).15
All 3 bid dosage regimens and the 300 mg qd dosage regimen of TMC310911 were generally safe and tolerable in the studied population. Most TEAEs were gastrointestinal system related, similar to TEAEs reported in previous phase 1 studies (Hoetelmans et al, manuscript in preparation). No deaths or serious TEAEs were reported during the trial. No clinically relevant changes were observed in laboratory findings or ECG parameters.
TMC310911 is structurally closely similar to darunavir (PREZISTA), an approved antiretroviral agent indicated for the treatment of HIV infection.16 Similar to our findings, the most common TEAEs reported in darunavir clinical studies were also related to gastrointestinal system.17 Darunavir has also been associated with severe hepatotoxicity.17 In the present study, 1 patient in the 150 mg bid treatment group had grade 4 hypertransaminasemia (alanine transaminase levels 438 U/L); however, no concomitant therapy for increased transaminase levels was initiated and the adverse event resolved by day 15. Further studies of TMC310911 are warranted to confirm the hepatic safety of this drug in HIV-infected populations.
The efficacy findings observed in this short-term study of TMC310911 were similar to those found earlier in monotherapy trials of HIV PIs boosted with ritonavir. In the current study, 1 patient (150 mg bid group) showed <50 copies per milliliter of viral load with only 14 days of treatment. As the efficacy results indicate 150 mg bid or 300 mg qd as the clinically effective dose for TMC310911, it could become another attractive once-daily regimen with reduced dose intensity. In addition, the good tolerability that needs to be confirmed in further studies may further improve the acceptance of TMC310911 treatment in HIV-infected patients. Due to its high genetic barrier, TMC310911 seems promising for class-sparing regimens and pretreated patients with virological failure. The strategy to start induction therapy at high HIV-1 viral loads with a class-sparing but robust ART with a high genetic resistance barrier seems to be a feasible approach using TMC310911 treatment.
Although in this study TMC310911 has shown potent antiviral activity in treatment-naive HIV-1–infected patients, the efficacy of TMC310911 should also be evaluated in treatment-experienced patients. Nevertheless, efficacy, safety, and PK findings from this study provide a strong basis for further evaluation of TMC310911 in larger clinical trials of longer durations that may include treatment-naive and treatment-experienced HIV-infected patients carrying resistant virus. Furthermore, this study was conducted almost exclusively in white men and hence further studies would be necessary to demonstrate PK and safety of TMC310911 in women, other ethnic background, and in special situations, such as co-existing viral hepatitis and end-organ disease.
In treatment-naive HIV-1–infected patients, treatment with TMC310911 (in combination with 100 mg of ritonavir) showed potent antiviral activity at 75, 150, and 300 mg bid as well as 300 mg qd dosage regimens. At steady state, TMC310911 showed a linear PK profile and the daily systemic exposure was similar for the 300 mg qd and 150 mg bid dosing regimens. The TMC310911/ritonavir combination treatment was found to be generally safe and well tolerated in the studied population.
The authors acknowledge Drs. G. Van't Klooster, P. Wigerinck, A. Raoof, A. Bollen, M. Schöller, E. Lathouwers, H. Muller, R. Leemans, E. Van Beirendonck, and N. Pemble for their contributions in study design and during the conduct of the study. Dr. Shruti Shah (SIRO Clinpharm Pvt. Ltd.) provided writing assistance, and Dr. Bradford Challis (Janssen Research & Development, LLC.) provided additional editorial support for this manuscript. The authors thank the study participants, without whom this study would not have been accomplished.
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antiretroviral therapy; antiviral activity; HIV-1 protease inhibitor; pharmacokinetics; ritonavir; TMC310911
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