Fixed-Dose Artesunate–Amodiaquine Combination vs Chloroquine for Treatment of Uncomplicated Blood Stage P. vivax Infection in the Brazilian Amazon: An Open-Label Randomized, Controlled Trial
Fixed-Dose Artesunate-Amodiaquine Combination vs Chloroquine for Treatment of Uncomplicated Blood Stage P. vivax Infection in the Brazilian Amazon: An Open-Label Randomized, Controlled Trial
Andre M. Siqueira (andre.siqueira@ini 0 1 2 4
Aline C. Alencar 1 2 4
Gisely C. Melo 1 2 4
Belisa L. Magalhaes 1 2 4
Kim Machado 2 4
Aristóteles C. Alencar Filho 2 8
Andrea Kuehn 2 4 7
Marly M. Marques 2 4
Monica Costa Manso 2 4
Ingrid Felger 2 6
José L. F. Vieira 2 5
Valerie Lameyre 2 10
Claudio T. Daniel-Ribeiro 2 9
Marcus V. G. Lacerda 1 2 3 4
0 Instituto Nacional de Infectologia Evandro Chagas , Fundação Oswaldo Cruz, Rio de Janeiro
1 Universidade do Estado do Amazonas , Manaus
2 Received 7 May 2016; editorial decision 3 October 2016; accepted 18 October 2016; pub- lished online December 16, 2016. Fundação Oswaldo Cruz, Av. Brasil 4365 - Rio de Janeiro, RJ , Brazil
3 Instituto Leônidas e Maria Deane , Fundação Oswaldo Cruz, Manaus , Brazil
4 Fundação de Medicina Tropical Dr. Heitor Vieira Dourado
5 Universidade Federal do Pará , Belém , Brazil
6 Swiss Tropical and Public Health Institute , Basel , Switzerland
7 ISGlobal, Barcelona Center for International Health Research (CRESIB), Hospital Clínic - Universitat de Barcelona , Barcelona , Spain
8 Universidade Federal do Amazonas , Manaus , Brazil
9 Instituto Oswaldo Cruz , Fundação Oswaldo Cruz, Rio de Janeiro
10 Access to Medicines Department , Sanofi , Paris , France
Background. Despite increasing evidence of the development of Plasmodium vivax chloroquine (CQ) resistance, there have been no trials comparing its efficacy with that of artemisinin-based combination therapies (ACTs) in Latin America. Methods. This randomized controlled trial compared the antischizontocidal efficacy and safety of a 3-day supervised treatment of the fixed-dose combination artesunate-amodiaquine Winthrop® (ASAQ) versus CQ for treatment of uncomplicated P. vivax infection in Manaus, Brazil. Patients were followed for 42 days. Primary endpoints were adequate clinical and parasitological responses (ACPR) rates at day 28. Genotype-adjustment was performed. Results. From 2012 to 2013, 380 patients were enrolled. In the per-protocol (PP) analysis, adjusted-ACPR was achieved in 100% (165/165) and 93.6% (161/172) of patients in the ASAQ and CQ arm (difference 6.4%, 95% CI 2.7%; 10.1%) at day 28 and in 97.4% (151/155) and 77.7% (129/166), respectively (difference 19.7%, 95% CI 12.9%; 26.5%), at day 42. Apart from ITT D28 assessment, superiority of ASAQ on ACPR was demonstrated. ASAQ presented faster clearance of parasitaemia and fever. Based on CQ blood level measurements, CQ resistance prevalence was estimated at 11.5% (95% CI: 7.5-17.3) up to day 42. At least one emergent adverse event (AE) was recorded for 79/190 (41×6%) in the ASAQ group and for 85/190 (44×7%) in the CQ group. Both treatments had similar safety profiles. Conclusions. ASAQ exhibited high efficacy against CQ resistant P. vivax and is an adequate alternative in the study area. Studies with an efficacious comparator, longer follow-up and genotype-adjustment can improve CQR characterization. Clinical Trials Registration. NCT01378286.
There were an estimated 214 million malaria episodes and 438
000 related deaths in 2015 . Plasmodium vivax is the
malaria-causing parasite species with the widest geographical
distribution, resulting in 2.85 billion people at risk . Studies from
all P. vivax endemic areas demonstrate that this infection can
progress to have severe and fatal outcomes [3, 4], rendering the
long-held belief that P. vivax is benign as no longer valid .
Resistance to antimalarials is a major barrier for
case-management and control of transmission [6, 7] and
requires constant monitoring. For more than 60 years, the
mainstay of P. vivax treatment has been a combination of
chloroquine (CQ) with primaquine (PQ) as an antirelapse
drug [8, 9]. This combination’s synergistic schizontocidal
effect, which is associated with the parasite’s usually lower
biomass and shorter duration of gametocytes presence
compared with those of Plasmodium falciparum, may have
contributed to slower development of CQ resistance in P.
vivax . However, there has been an increasing number of
reports of CQ resistance (CQR) in regions where this
parasite is endemic [10–12], especially in Southeast Asia and
the Pacific region [13–15], where 5 countries have already
adopted artemisinin-based combination therapies (ACTs).
these therapies provide fast parasite clearance and prevent
recrudescences  as first-line treatment for P. vivax .
In Latin America, where P. vivax is the most prevalent
species causing malaria  despite recent evidence of CQR [11,
17–20], no studies comparing the efficacy of ACTs to that of
CQ have been reported.
The combination of artesunate–amodiaquine (ASAQ) against
P. falciparum has been adopted in many countries and is one of
the World Health Organization (WHO) prequalified
antimalarials. The ASAQ fixed-dose combination (FDC) tested in this study
(artesunate–amodiaquine Winthrop, or ASAQ Winthrop) was
codeveloped by DNDi and Sanofi. This formulation was shown
to result in better compliance and reduced risk of emergence of
P. falciparum resistance when compared with loose-dose
combinations and coblisters [21, 22]. We conducted this clinical trial in
order to evaluate the efficacy and safety of the ASAQ FDC
compared with that of CQ against uncomplicated P. vivax infection.
Our study was undertaken at Fundação de Medicina Tropical
Dr. Heitor Vieira Dourado (FMT-HVD), Manaus, in the
Brazilian Western Amazon region. Malaria transmission is
restricted to rural areas, and P. vivax causes around 90% of
malaria cases . Antimalarials are only provided in health
units after diagnostic confirmation of infection. National
guidelines recommend CQ (total dose of 25 mg/kg over 3 days)
and PQ (0.5 mg/kg/day over 7 days) for P. vivax infection
treatment and artemether–lumefantrine or artesunate–mefloquine
for P. falciparum . Studies showed therapeutic failure rates
as high as 10% with CQ monotherapy for P. vivax in 2005 .
This was an open-label, randomized, noninferiority, controlled
trial that compared the efficacy and safety of ASAQ (Winthrop;
Sanofi, Morocco) and CQ (Farmanguinhos, Brazil) for
treatment of uncomplicated P. vivax blood stage infection. The
study was based on the WHO antimalarial drug efficacy
protocols modified for P. vivax [25, 26]. Patients were followed up for
42 days to assess drug efficacy and safety.
The ethics review board of FMT-HVD (0426/2011) and the
National Brazilian Committee of Ethics (16532/2011) approved
the study. All adult patients and legal guardians of children
provided written informed consent. The protocol is available in the
Individuals aged >6 months with a body weight >5 kg with
slide-confirmed P. vivax monoinfection, parasite density
between 250 and 100 000 parasites/µL, and axillary temperature
≥37.5°C or history of fever in the last 48 hours were considered
eligible. Exclusion criteria included pregnant or breast-feeding
women; plan of leaving the study area in the following 42 days;
known hypersensitivity to 1 of the investigational products;
blurred vision suggesting retinopathy; presence of at least 1
severe criterion of malaria; known severe concomitant or
underlying disease; and women of childbearing potential unwilling to
use an effective contraceptive method during the study.
Procedures, Randomization, and Concealment
Enrolled patients were randomly assigned to 1 of the treatment
arms by a study nurse through a computer-generated list that
linked each patient’s study number to an opaque zone, thus,
concealing the assigned treatment arm. Neither the study
doctors nor the laboratory personnel responsible for reading the
slides and the polymerase chain reaction (PCR) test had access
to patients’ allocation during the study.
ASAQ was administered as a fixed-dose combination with
3 oral formulations (25/67.5 mg, 50/135 mg, 100/270 mg) and
CQ as 150-mg tablets. Dosing was based on established weight
bands for each drug (Supplementary Table 1). Study nurses
supervised all dosing at enrollment and 24 and 48 hours after.
When necessary, tablets were dissolved in water and
administered orally using a syringe to ensure proper dosing to children.
Patients were followed on an outpatient basis. PQ was withheld
until day 42 or at day of recurrence. Recurrences during
follow-up were treated with fixed-dose artesunate–mefloquine
combination (Farmanguinhos, Brazil). The dose was
administered a second time if vomiting occurred within 30 minutes.
Visits for clinical and microscopic assessments were
scheduled on days 1, 2, 3, 7, 14, 28, and 42 after enrollment. Laboratory
blood assessments (total blood cell count, bilirubin, glycemia,
aspartate aminotransferase, alanine aminotransferase [ALT],
and creatinine) were performed at enrollment and repeated
on day 7 and day 28. Electrocardiograms were performed at
enrollment, day 2, and day 28 for all participants aged >10 years
and evaluated by a cardiologist. Blood samples were collected
on day 7 and day of recurrence for CQ and desetylchloroquine
(DCQ) blood assays, measured using high-performance liquid
chromatography as previously described . The sum of CQ
and DCQ blood levels was used to classify parasites as sensitive
or resistance based on the 100-ng/mL cutoff level, as previously
established [12, 26, 28]. Technical problems with sample storage
and collection, consisting of insufficient volume of blood for the
analyses, prevented measurement of day 7 blood levels of AQ.
Two experienced technicians examined microscopic blood
smears. Parasite density was calculated using the white cell
count from the nearest total blood cell count (usually from
enrollment, day 7, or day 28) .
Real-time PCR was performed on filter-paper samples from
enrollment or recurrences to confirm P. vivax monoinfection
according to described protocols . For the genotyping
procedures for comparing day 0 and recurrence samples, 3 highly
polymorphic gene regions were chosen according to diversity
and discriminatory potential in the region, namely, msp1F3,
MS2, and MS8 [31–34]. As there is no standard
recommendation for classifying P. vivax recurrences due to difficulties
distinguishing reinfection, recrudescence, and relapse [35, 36], we
adapted the classification method recommended by WHO for
P. falciparum . For each recurrence, samples were classified
as homologous if at least 1 allele for each loci investigated was
detected in both paired samples and as heterologous if all alleles
for a given marker were different. A recurrent homologous
P. vivax episode could derive either from a
recrudescent-resistant parasite or from a dormant liver stage. For this study, we
chose to treat these events as treatment failures after correction.
Further details on the molecular characterization are provided
in the Supplementary Materials.
Statistical Analyses and Sample Calculation
We assumed a 90% efficacy rate for CQ within 28 days  and
95% efficacy for ASAQ . The noninferiority margin was
defined at 5%, considering alpha at 2.5% for the unilateral test
and power of 90%, a sample size of 145 individuals per arm,
increased to 190 after adding 15% loss to follow-up and 10%
risk of mixed infections.
The primary endpoint was genotype-adjusted adequate cure
and parasitological response (ACPR) at day 28 for the per-protocol
(PP) population. Secondary endpoints, performed in both the PP
and intention-to-treat (ITT) populations, included crude ACPR on
day 28 and ACPR on day 14 and day 42, prevalence and incidence
of positive asexual parasitemia and gametocyte carriage,
hemoglobin changes from baseline, and incidence of adverse events (AEs).
Noninferiority was demonstrated if the lower bound of the
95% confidence interval (CI) of the risk difference between the
2 arms was greater than −0.05 in the PP population populations.
The CIs were calculated using normal approximation, with
continuity correction in the Wald limits applied in the case of
empty cells . If noninferiority was shown, a 2-sided Fisher
exact test to assess superiority was performed in the ITT
population. This analysis was performed despite not being described
in the protocol-following recommendation  and due to the
large difference observed. Both the PP and ITT are presented.
Time to recurrence was assessed by survival curves using the
Kaplan-Meier estimator and log-rank tests. The proportion of
patients with negative blood slides for both asexual and sexual
parasites and fever clearance was analyzed at days 1, 2, and 3. A general
estimating equation (GEE) model  was used to compare
person-week gametocyte densities during follow-up; this consisted of a
univariate analysis with robust standard errors, with the number of
gametocyte-positive slides per individual per week as the outcome.
Anemia was graded according to WHO references .
Neutropenia and elevation of ALT were considered AEs of
special interest [42–44]. An independent data monitoring
committee comprised of 3 renowned experts reviewed the study
protocol and evaluated the results of efficacy and safety
analyses. An additional analysis was performed only for the CQ arm
to investigate a possible association between delayed parasite
clearance (>72 hours) as the dependent variable and risk of
recurrence, the outcome variable, using logistic regression.
Patients were enrolled between January 2012 and June 2013
(Figure 1). Most patients were adult males and resided in the
nonactive transmission Manaus urban area (Table 1).
Noninferiority was demonstrated (97.5% CI lower
bound = 2.74) as genotype-adjusted ACPR rates at day 28
of 100% (165/165) for ASAQ and 93.6% (161/172) for CQ.
Although superiority of ASAQ was not demonstrated on day 28
in the ITT population (P = .345), it was demonstrated in the PP
population and on day 42 for both populations (Tables 2 and 3;
Figure 2). The difference was larger between day 28 and day 42.
Through genotype classification, 64.8% (34/54) of the CQ
arm recurrences (ITT population) were homologous compared
Table 1. Demographic and Disease Characteristics at Baseline in the
Amodiaquine (n = 189)
with half (3/6) in the ASAQ arm (Figure 3A and Table 3). CQ/
DCQ blood levels on the day of recurrence were measured for
48 of 54 patients, with 19 being >100 ng/mL, resulting in a CQR
prevalence of 11.5% (95% CI, 7.5–17.3). This result was further
corroborated by both homologous (14/34) and heterologous
(5/6) recurrences emerging in the circulation, with CQ/DCQ
blood levels as high as 533 ng/mL (Figure 3B).
Parasitemia clearance was faster, and the proportion of patients
clearing fever at day 1 was higher for ASAQ (Tables 2 and 3).
Table 2. Adequate Clinical and Parasitological Response (ACPR) by Time
Point for the Per-Protocol Population
n = 165 (%) n = 172 (%)
Genotype classification of failuresa
19⋅7% (12⋅9–26⋅5) <⋅001
Data are expressed as percentage or mean (range; standard deviation), unless specified
Abbreviation: ACPR, adequate cure and parasitological response.
aGenotyping detailed data available in Table Supplementary S1.
Table 3. Efficacy Assessments at Day 28 and Day 42 for the Intention-to-Treat Population
Amodiaquine, n = 189 (%)
Genotyping detailed data available in Supplementary Table S1.
Abbreviation: ACPR, adequate cure and parasitological response.
aLosses to follow-up and samples with genotype assessment..
From day 7, 2.4% of patients treated with ASAQ and 14.7% in
the CQ group presented with microscopically detected
gametocytes during follow-up (P < .001). The GEE model demonstrated
a lower overall gametocyte-positive density in the ASAQ arm
compared with that of CQ (4.7 vs 12.2 gametocyte-positive
slides/100 person-weeks, respectively; P < .001). Risk of
developing gametocytemia after treatment initiation in patients with no
gametocytes at inclusion (ASAQ, n = 83; CQ, n = 76) was higher
for CQ (20.2% vs 55.4%; P < 0·001). There was no association
between delayed parasite clearance and risk of recurrence (odds
ratio = 1.1; 95% CI, 0.7–1.6; P = .836) in the CQ arm.
There was a relative decrease of hemoglobin (Hb) between
inclusion and day 7 for all patients (−2.5; standard
deviation = 8.4), with greater reduction observed for ASAQ (−4.2
[7.4] vs −0.9 [9.0]; P < .001). There was a similar proportion of
patients who presented with grade 2 or higher anemia at day
7 (3 [1.6%] vs 2 [1.1%]). At day 28, patients who received CQ
presented with a higher increase from baseline (0.3 [13.2] vs 3.7
[12.0]; P = .005). Overall AE rates were similar (Table 4). Severe
AEs were only observed in the ASAQ arm, none with sequelae.
We observed high efficacy of the ASAQ FDC against
CQ-resistant P. vivax with respect to ACPR and other efficacy
outcomes. This is the first study to compare the ASAQ
combination with chloroquine against P. vivax infection and the first
trial to compare an ACT with CQ in Latin America .
A remarkable result of this study is the high efficacy of ASAQ
at day 42 (for which all recurrences occurred after day 40).
Interpretation of failures occurring after day 28 is complicated
by the possibility of recurrences being relapses or reinfections [9,
25]. Despite this caveat, we believe the observed late recurrences
indicate the existence of low-grade resistance to CQ, which would
suppress but not completely eliminate circulating parasites .
This is based on 2 important assumptions: very low risk of
reinfection, as most patients (90.5%) resided in urban areas with no active
malaria transmission , and negligible contribution of relapses,
which usually occur after day 35 in the region [32, 45, 46].
In the absence of PQ administration, the drug’s elimination
half-life is an important property to be considered against P. vivax
due to the post-treatment prophylactic effect . Its influence is
illustrated by 2 trials that compared the ASAQ loose-dose
combination to dihydroartemisinin–piperaquine, an ACT with a longer
half-life. Lower efficacy against late recurrences of ASAQ  was
not confirmed when PQ was coadministered . This rationale
is supported by the higher efficacy of CQ in preventing late
recurrences compared with drugs with shorter half-lives (arthemeter–
lumefantrine) in areas of low prevalence of CQR . Thus, our
results provide strong evidence of a higher-than-expected CQR
prevalence because, even though CQ and its metabolites’ half-lives
are longer, there was a large number of recurrences in the CQ arm.
The genotype-adjusted ACPR rates were measured in
an attempt to gain a more rigorous case definition of CQR.
Genotyping has been applied in P. vivax efficacy studies with
interesting results [35, 36]. However, unlike in P. falciparum,
there are no well-defined criteria to differentiate recrudescence
from reinfection and relapse . PCR correction will not
necessarily lead to more precise estimation of efficacy in areas
of low endemicity, where homologous hypnozoites are more
ASAQ was more effective in clearing patent gametocytemia.
CQ may take up to 4 days for gametocyte clearance . Studies
have found an association between prolonged gametocytemia
and asexual stage recurrence . It is not clear if use of an ACT
has an effect on reducing transmission.
Hb reduction at day 7 was higher in patients who received
ASAQ. Possible explanations include higher inflammatory
response and/or oxidative stress associated with treatment,
suppression of the blood marrow by artesunate, and pitting [50,
51]. The risk of severe anemia after ACT is considered low ;
indeed, there was no severe anemia in our study.
The safety and tolerability of ASAQ FDC were consistent
with what was found in previous studies that used this
combination in the approved indication “treatment of uncomplicated
P. falciparum malaria” . Sinus bradycardia occurred without
symptoms or clinical complications, and there was no
difference regarding the corrected QT inverval (QTc).
A limitation of our study was the small number of children
included. This population is at higher risk of treatment failure
[53, 54], for which age-stratified sampling would be
important. There was a higher loss to follow-up in the ASAQ arm,
which had an impact on the efficacy assessment in the ITT
population. An examination of the notification database did
not reveal a higher rate of failure among losses. As we were
not able to assess the pharmacokinetic profile of amodiaquine,
evaluation of the effect of a longer elimination half-life in
this population on efficacy against late recurrences was not
Most Frequent Adverse Events Reported in the Safety Population
n = 190 (%)a
n = 190 (%)
By not coadministering PQ, we were able to estimate CQR,
which at 11.5%, considering concurrent blood drug levels
criterion, is very high. This is important, as patients receiving CQ
are at higher risk of recurring episodes from resistant parasites
that arise from either recrudescence or relapse. These findings
also suggest that the usual methods for measuring CQ efficacy
are prone to underestimate the true CQR rates. Most studies of
P. vivax efficacy restrict follow-up to 28 days in order to
minimize the contribution of relapses, considering CQ elimination
half-life. We believe this can result in underestimation of
resistance, which, in our study, could be as high as 30% based on the
risk difference against an efficacious comparator. This difference
highlights the need to develop better designs and strategies for
measuring antimalarial efficacy against P. vivax.
This is the first trial to compare an ACT with CQ as blood
schizontocidal against P. vivax in Latin America. We
demonstrated that CQR is underestimated in the region and that a
change in treatment policy should be considered. Recently
Only AEs that affected at least 4% in each group are listed.
Abbreviations: AE, adverse event; ALAT, alanine aminotransferase.
a The patient with mixed infection detected by polymerase chain reaction was included in
the safety analyses.
b Only events that affected at least 1% of the population in each group are listed.
c ALAT >5 × upper limit of normal (ULN) value, or ALAT >3 × ULN if ALAT was >ULN on
day 0, or ALAT >3 × ULN associated with total bilirubin >2×ULN.
d Neutrophil count <400/mm3 in children aged 3 months to 12 years or <750/mm3 in
children aged >12 years or adults. ¶Events were classified as serious AEs based on the need
for intravenous medication to alleviate the symptoms.
*There were no investigational product discontinuation or deaths in the study. Full recovery
occurred for all AEs.
Plasmodium vivax has received increased attention, requiring
development of new strategies and tools . The choice of
an effective schizontocidal drug, therefore, cannot be
underestimated. Although CQ is still the first-line therapy in most
endemic countries, resistance is a growing problem, probably
underestimated because of coadministration with PQ and
misclassification of recrudescence as relapse. The decision to
substitute CQ for an ACT as the drug of choice for treating P. vivax
infections is complex and should be based on different factors,
including the prevalence of CQ-resistant parasites; the current
treatment adopted for P. falciparum; efficacy of the partner
drug; interaction of the ACT with PQ; and the potential impact
of reducing transmission . In order to establish unified
treatment recommendations for P. falciparum and P. vivax, it
is necessary to provide a more effective option and reduce the
risk of treating P. falciparum with CQ due to misdiagnosis .
We believe that CQ should be replaced by a more efficacious
alternative in this region and expect policymakers to consider
these findings in order to define the best strategies to accelerate
the path toward malaria eradication.
Supplementary materials are available at Clinical Infectious Diseases
online. Consisting of data provided by the author to benefit the reader, the
posted materials are not copyedited and are the sole responsibility of the
author, so questions or comments should be addressed to the author.
Funding. This study was funded by Sanofi. The study sponsor
participated in the development the protocol, interpreted the data, helped write the
report, and performed monitoring.
Acknowledgements. We acknowledge Director-President of FMT-HVD
Professor Maria Alecrim for the institutional support, all the personnel from
the Malaria Laboratory for their contribution in running the trial, and the
study monitor from Sanofi. We thank the patients and their families for taking
part in the study. C. T. D. R. and M. V. G. L. are recipients of a grant from the
Conselho Nacional de Desenvolvimento Científico e Tecnológico as Bolsistas
de Produtividade and A. M. S. receives a short-term training grant from
WHO’s Special Programme for Research and Training in Tropical Diseases.
Author contributions. A. M. S., V. L., C. D. T. R., and M. V. G. L.
designed and coordinated the study. A. M. S., A. C. A., B. L. M., K. M., M.
M. M., and M. C. M. participated in data collection. G. C. M., A. K., M. M.
M., I. F., and J. L. F. V. participated in the laboratory analyses. A. M. S., V.
L., and M. V. G. L. conducted the statistical analyses. A. M. S. wrote the first
draft of the manuscript. All authors participated in data interpretation and
approved the final version and take responsibility for accuracy and
completeness of data reporting and for the decision to submit for publication.
Potential conflicts of interest. V. L. is employed by Sanofi. All other
authors report no conflicts. All authors have submitted the ICMJE Form
for Disclosure of Potential Conflicts of Interest. Conflicts that the editors
consider relevant to the content of the manuscript have been disclosed.
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