Is amodiaquine failing in Rwanda? Efficacy of amodiaquine alone and combined with artesunate in children with uncomplicated malaria

Haematological consequences of acute uncomplicated falciparum malaria: a WorldWide Antimalarial Resistance Network pooled analysis of individual patient data

BACKGROUND

Plasmodium falciparum malaria is associated with anaemia-related morbidity, attributable to host, parasite and drug factors. We quantified the haematological response following treatment of uncomplicated P. falciparum malaria to identify the factors associated with malarial anaemia.

METHODS

Individual patient data from eligible antimalarial efficacy studies of uncomplicated P. falciparum malaria, available through the WorldWide Antimalarial Resistance Network data repository prior to August 2015, were pooled using standardised methodology. The haematological response over time was quantified using a multivariable linear mixed effects model with nonlinear terms for time, and the model was then used to estimate the mean haemoglobin at day of nadir and day 7. Multivariable logistic regression quantified risk factors for moderately severe anaemia (haemoglobin < 7 g/dL) at day 0, day 3 and day 7 as well as a fractional fall ≥ 25% at day 3 and day 7.

RESULTS

A total of 70,226 patients, recruited into 200 studies between 1991 and 2013, were included in the analysis: 50,859 (72.4%) enrolled in Africa, 18,451 (26.3%) in Asia and 916 (1.3%) in South America. The median haemoglobin concentration at presentation was 9.9 g/dL (range 5.0-19.7 g/dL) in Africa, 11.6 g/dL (range 5.0-20.0 g/dL) in Asia and 12.3 g/dL (range 6.9-17.9 g/dL) in South America. Moderately severe anaemia (Hb < 7g/dl) was present in 8.4% (4284/50,859) of patients from Africa, 3.3% (606/18,451) from Asia and 0.1% (1/916) from South America. The nadir haemoglobin occurred on day 2 post treatment with a mean fall from baseline of 0.57 g/dL in Africa and 1.13 g/dL in Asia. Independent risk factors for moderately severe anaemia on day 7, in both Africa and Asia, included moderately severe anaemia at baseline (adjusted odds ratio (AOR) = 16.10 and AOR = 23.00, respectively), young age (age < 1 compared to ≥ 12 years AOR = 12.81 and AOR = 6.79, respectively), high parasitaemia (AOR = 1.78 and AOR = 1.58, respectively) and delayed parasite clearance (AOR = 2.44 and AOR = 2.59, respectively). In Asia, patients treated with an artemisinin-based regimen were at significantly greater risk of moderately severe anaemia on day 7 compared to those treated with a non-artemisinin-based regimen (AOR = 2.06 [95%CI 1.39-3.05], p < 0.001).

CONCLUSIONS

In patients with uncomplicated P. falciparum malaria, the nadir haemoglobin occurs 2 days after starting treatment. Although artemisinin-based treatments increase the rate of parasite clearance, in Asia they are associated with a greater risk of anaemia during recovery.

History of malaria control in Rwanda: implications for future elimination in Rwanda and other malaria-endemic countries

BACKGROUND

Malaria was first reported in Rwanda in the early 1900s with significant heterogeneity and volatility in transmission over subsequent decades. Here, a comprehensive literature review of malaria transmission patterns and control strategies in Rwanda between 1900 and 2018 is presented to provide insight into successes and challenges in the country and to inform the future of malaria control in Rwanda.

METHODS

A systematic literature search of peer-reviewed publications (Web of Knowledge, PubMed, Google Scholar, and the World Health Organization Library (WHOLIS) and grey literature on malaria control in Rwanda between 1900 and 2019 was conducted with the following search terms: "malaria"", "Rwanda", "epidemiology", "control", "treatment", and/or "prevention." Reports and other relevant documents were also obtained from the Rwanda National Malaria Control Programme (NMCP). To inform this literature review and evidence synthesis, epidemiologic and intervention data were collated from NMCP and partner reports, the national routine surveillance system, and population surveys.

RESULTS

Two hundred sixty-eight peer-reviewed publications and 56 grey literature items were reviewed, and information was extracted. The history of malaria control in Rwanda is thematically described here according to five phases: 1900 to 1954 before the launch of the Global Malaria Eradication Programme (GMEP); (2) Implementation of the GMEP from 1955 to 1969; (3) Post- GMEP to 1994 Genocide; (4) the re-establishment of malaria control from 1995 to 2005, and (5) current malaria control efforts from 2006 to 2018. The review shows that Rwanda was an early adopter of tools and approaches in the early 2000s, putting the country ahead of the curve and health systems reforms created an enabling environment for an effective malaria control programme. The last two decades have seen unprecedented investments in malaria in Rwanda, resulting in significant declines in disease burden from 2000 to 2011. However, in recent years, these gains appear to have reversed with increasing cases since 2012 although the country is starting to make progress again.

CONCLUSION

The review shows the impact and fragility of gains against malaria, even in the context of sustained health system development. Also, as shown in Rwanda, country malaria control programmes should be dynamic and adaptive to respond and address changing settings.

High cure rates and tolerability of artesunate-amodiaquine and dihydroartemisinin-piperaquine for the treatment of uncomplicated falciparum malaria in Kibaha and Kigoma, Tanzania

BACKGROUND

The Tanzanian National Malaria Control Programme (NMCP) and its partners have been implementing regular therapeutic efficacy studies (TES) to monitor the performance of different drugs used or with potential use in Tanzania. However, most of the recent TES focused on artemether-lumefantrine, which is the first-line anti-malarial for the treatment of uncomplicated falciparum malaria. Data on the performance of other artemisinin-based combinations is urgently needed to support timely review and changes of treatment guidelines in case of drug resistance to the current regimen. This study was conducted at two NMCP sentinel sites (Kibaha, Pwani and Ujiji, Kigoma) to assess the efficacy and safety of artesunate-amodiaquine (ASAQ) and dihydroartemisinin-piperaquine (DP), which are the current alternative artemisinin-based combinations in Tanzania.

METHODS

This was a single-arm prospective evaluation of the clinical and parasitological responses of ASAQ and DP for directly observed treatment of uncomplicated falciparum malaria. Children aged 6 months to 10 years and meeting the inclusion criteria were enrolled and treated with either ASAQ or DP. In each site, patients were enrolled sequentially; thus, enrolment of patients for the assessment of one artemisinin-based combination was completed before patients were recruited for assessment of the second drugs. Follow-up was done for 28 or 42 days for ASAQ and DP, respectively. The primary outcome was PCR corrected cure rates while the secondary outcome was occurrence of adverse events (AEs) or serious adverse events (SAEs).

RESULTS

Of the 724 patients screened at both sites, 333 (46.0%) were enrolled and 326 (97.9%) either completed the 28/42 days of follow-up, or attained any of the treatment outcomes. PCR uncorrected adequate clinical and parasitological response (ACPR) for DP on day 42 was 98.8% and 75.9% at Kibaha and Ujiji, respectively. After PCR correction, DP's ACPR was 100% at both sites. For ASAQ, no parasite recurrence occurred giving 100% ACPR on day 28. Only one patient in the DP arm (1.1%) from Ujiji had parasites on day 3. Of the patients recruited (n = 333), 175 (52.6%) had AEs with 223 episodes (at both sites) in the two treatment groups. There was no SAE and the commonly reported AE episodes (with > 5%) included, cough, running nose, abdominal pain, diarrhoea and fever.

CONCLUSION

Both artemisinin-based combinations had high cure rates with PCR corrected ACPR of 100%. The two drugs had adequate safety with no SAE and all AEs were mild, and not associated with the anti-malarials. Continued TES is critical to monitor the performance of nationally recommended artemisinin-based combination therapy and supporting evidence-based review of malaria treatment policies. Trial registration This study is registered at ClinicalTrials.gov, No. NCT03431714.

Amodiaquine resistance in Plasmodium berghei is associated with PbCRT His95Pro mutation, loss of chloroquine, artemisinin and primaquine sensitivity, and high transcript levels of key transporters

Background: The human malaria parasite Plasmodium falciparum has evolved complex drug evasion mechanisms to all available antimalarials. To date, the combination of amodiaquine-artesunate is among the drug of choice for treatment of uncomplicated malaria. In this combination, a short acting, artesunate is partnered with long acting, amodiaquine for which resistance may emerge rapidly especially in high transmission settings. Here, we used a rodent malaria parasite Plasmodium berghei ANKA as a surrogate of P. falciparum to investigate the mechanisms of amodiaquine resistance. Methods: We used serial technique to select amodiaquine resistance by submitting the parasites to continuous amodiaquine pressure. We then employed the 4-Day Suppressive Test to monitor emergence of resistance and determine the cross-resistance profiles. Finally, we genotyped the resistant parasite by PCR amplification, sequencing and relative quantitation of mRNA transcript of targeted genes. Results: Submission of P. berghei ANKA to amodiaquine pressure yielded resistant parasite within thirty-six passages. The effective dosage that reduced 90% of parasitaemia (ED ₉₀) of sensitive line and resistant line were 4.29mg/kg and 19.13mg/kg, respectively. After freezing at -80ºC for one month, the resistant parasite remained stable with an ED ₉₀ of 18.22mg/kg. Amodiaquine resistant parasites are also resistant to chloroquine (6fold), artemether (10fold), primaquine (5fold), piperaquine (2fold) and lumefantrine (3fold). Sequence analysis of Plasmodium berghei chloroquine resistant transporter revealed His95Pro mutation. No variation was identified in Plasmodium berghei multidrug resistance gene-1 (Pbmdr1), Plasmodium berghei deubiquitinating enzyme-1 or Plasmodium berghei Kelch13 domain nucleotide sequences. Amodiaquine resistance is also accompanied by high mRNA transcripts of key transporters; Pbmdr1, V-type/H+ pumping pyrophosphatase-2 and sodium hydrogen ion exchanger-1 and Ca ²⁺/H ⁺ antiporter. Conclusions: Selection of amodiaquine resistance yielded stable "multidrug-resistant'' parasites and thus may be used to study common resistance mechanisms associated with other antimalarial drugs. Genome wide studies may elucidate other functionally important genes controlling AQ resistance in P. berghei.

Haemoglobin changes and risk of anaemia following treatment for uncomplicated falciparum malaria in sub-Saharan Africa

Background

Anaemia is common in malaria. It is important to quantitate the risk of anaemia and to distinguish factors related to the natural history of disease from potential drug toxicity.

Methods

Individual-patient data analysis based on nine randomized controlled trials of treatments of uncomplicated falciparum malaria from 13 sub-Saharan African countries. Risk factors for reduced haemoglobin (Hb) concentrations and anaemia on presentation and after treatment were analysed using mixed effect models.

Results

Eight thousand eight hundred ninety-seven patients (77.0% <5 years-old) followed-up through 28 days treated with artemisinin combination therapy (ACT, 90%, n = 7968) or non-ACT. At baseline, under 5’s had the highest risk of anaemia (77.6% vs. 32.8%) and higher parasitaemia (43,938 μl) than older subjects (2784 μl). Baseline anaemia increased the risk of parasitological recurrence.

Hb began to fall after treatment start. In under 5’s the estimated nadir was ~35 h (range 29–48), with a drop of −12.8% from baseline (from 9.8 g/dl to 8.7 g/dl, p = 0.001); in under 15’s, the mean Hb decline between day 0–3 was −4.7% (from 9.4 to 9.0 g/dl, p = 0.001). The degree of Hb loss was greater in patients with high pre-treatment Hb and parasitaemia and with slower parasite reduction rates, and was unrelated to age. Subsequently, Hb increased linearly (+0.6%/day) until day 28, to reach +13.8% compared to baseline.

Severe anaemia (<5 g/dl, 2 per 1000 patients) was transient and all patients recovered after day 14, except one case of very severe anaemia associated with parasite recurrence at day 28.

There was no systematic difference in Hb concentrations between treatments and no case of delayed anaemia.

Conclusion

On presentation with acute malaria young children with high parasitaemia have the highest risk of anaemia. The majority of patients experience a drop in Hb while on treatment as early as day 1–2, followed by a linear increase through follow-up. The degree of the early Hb dip is determined by pre-treatment parasitaemia and parasite clearance rates. Hb trends and rick of anaemia are independent of treatment.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-017-2530-6) contains supplementary material, which is available to authorized users.

Amodiaquine resistance in Plasmodium berghei is associated with PbCRT His95Pro mutation, loss of chloroquine, artemisinin and primaquine sensitivity, and high transcript levels of key transporters

Background: The human malaria parasite Plasmodium falciparum has evolved complex drug evasion mechanisms to all available antimalarials. To date, the combination of amodiaquine-artesunate is among the drug of choice for treatment of uncomplicated malaria. In this combination, a short acting, artesunate is partnered with long acting, amodiaquine for which resistance may emerge rapidly especially in high transmission settings. Here, we used a rodent malaria parasite Plasmodium berghei ANKA as a surrogate of P. falciparum to investigate the mechanisms of amodiaquine resistance. Methods: We used serial technique to select amodiaquine resistance by submitting the parasites to continuous amodiaquine pressure. We then employed the 4-Day Suppressive Test to monitor emergence of resistance and determine the cross-resistance profiles. Finally, we genotyped the resistant parasite by PCR amplification, sequencing and relative quantitation of mRNA transcript of targeted genes. Results: Submission of P. berghei ANKA to amodiaquine pressure yielded resistant parasite within thirty-six passages. The effective dosage that reduced 90% of parasitaemia (ED90) of sensitive line and resistant line were 4.29mg/kg and 19.13mg/kg, respectively. After freezing at -80ºC for one month, the resistant parasite remained stable with an ED90 of 18.22mg/kg. Amodiaquine resistant parasites are also resistant to chloroquine (6fold), artemether (10fold), primaquine (5fold), piperaquine (2fold) and lumefantrine (3fold). Sequence analysis of Plasmodium berghei chloroquine resistant transporter revealed His95Pro mutation. No variation was identified in Plasmodium berghei multidrug resistance gene-1 (Pbmdr1), Plasmodium berghei deubiquitinating enzyme-1 or Plasmodium berghei Kelch13 domain nucleotide sequences. Amodiaquine resistance is also accompanied by high mRNA transcripts of key transporters; Pbmdr1, V-type/H+ pumping pyrophosphatase-2 and sodium hydrogen ion exchanger-1 and Ca2+/H+ antiporter. Conclusions: Selection of amodiaquine resistance yielded stable “multidrug-resistant’’ parasites and thus may be used to study common resistance mechanisms associated with other antimalarial drugs. Genome wide studies may elucidate other functionally important genes controlling AQ resistance in P. berghei.

Maximizing antimalarial efficacy and the importance of dosing strategies

Artemisinin-based combination therapies (ACTs) are the cornerstone for the treatment of malaria. However, confirmed resistance to artemisinins in South-East Asia, and reports of reduced efficacy of ACTs raise major concerns for malaria treatment and control. Without new drugs to replace artemisinins, it is essential to define dosing strategies that maximize therapeutic efficacy, limit the spread of resistance, and preserve the clinical value of ACTs. It is important to determine the extent to which reduced efficacy of ACTs reflects true resistance versus sub-optimal dosing, and quantify other factors that determine treatment failure. Pooled analyses of individual patient data from multiple clinical trials, by investigators in the Worldwide Antimalarial Resistance Network, have shown high overall efficacy for three widely used ACTs, artemether-lumefantrine, artesunate-amodiaquine, and dihydroartemisinin-piperaquine. Analyses also highlight that suboptimal dosing leads to increased risk of treatment failure, especially among children. In the most recent study, an analysis of clinical trials of artesunate-amodiaquine, widely used among children in Africa, revealed a superior efficacy for fixed-dose combination tablets compared to loose non-fixed dose combinations. This highlights the benefits of fixed-dose combinations as a practical strategy for ensuring optimal antimalarial dosing and maximizing efficacy. Please see related article: http://www.biomedcentral.com/1741-7015/13/66.

The effect of dosing strategies on the therapeutic efficacy of artesunate-amodiaquine for uncomplicated malaria: a meta-analysis of individual patient data

BACKGROUND

Artesunate-amodiaquine (AS-AQ) is one of the most widely used artemisinin-based combination therapies (ACTs) to treat uncomplicated Plasmodium falciparum malaria in Africa. We investigated the impact of different dosing strategies on the efficacy of this combination for the treatment of falciparum malaria.

METHODS

Individual patient data from AS-AQ clinical trials were pooled using the WorldWide Antimalarial Resistance Network (WWARN) standardised methodology. Risk factors for treatment failure were identified using a Cox regression model with shared frailty across study sites.

RESULTS

Forty-three studies representing 9,106 treatments from 1999-2012 were included in the analysis; 4,138 (45.4%) treatments were with a fixed dose combination with an AQ target dose of 30 mg/kg (FDC), 1,293 (14.2%) with a non-fixed dose combination with an AQ target dose of 25 mg/kg (loose NFDC-25), 2,418 (26.6%) with a non-fixed dose combination with an AQ target dose of 30 mg/kg (loose NFDC-30), and the remaining 1,257 (13.8%) with a co-blistered non-fixed dose combination with an AQ target dose of 30 mg/kg (co-blistered NFDC). The median dose of AQ administered was 32.1 mg/kg [IQR: 25.9-38.2], the highest dose being administered to patients treated with co-blistered NFDC (median = 35.3 mg/kg [IQR: 30.6-43.7]) and the lowest to those treated with loose NFDC-25 (median = 25.0 mg/kg [IQR: 22.7-25.0]). Patients treated with FDC received a median dose of 32.4 mg/kg [IQR: 27-39.0]. After adjusting for reinfections, the corrected antimalarial efficacy on day 28 after treatment was similar for co-blistered NFDC (97.9% [95% confidence interval (CI): 97.0-98.8%]) and FDC (98.1% [95% CI: 97.6%-98.5%]; P = 0.799), but significantly lower for the loose NFDC-25 (93.4% [95% CI: 91.9%-94.9%]), and loose NFDC-30 (95.0% [95% CI: 94.1%-95.9%]) (P < 0.001 for all comparisons). After controlling for age, AQ dose, baseline parasitemia and region; treatment with loose NFDC-25 was associated with a 3.5-fold greater risk of recrudescence by day 28 (adjusted hazard ratio, AHR = 3.51 [95% CI: 2.02-6.12], P < 0.001) compared to FDC, and treatment with loose NFDC-30 was associated with a higher risk of recrudescence at only three sites.

CONCLUSIONS

There was substantial variation in the total dose of amodiaquine administered in different AS-AQ combination regimens. Fixed dose AS-AQ combinations ensure optimal dosing and provide higher antimalarial treatment efficacy than the loose individual tablets in all age categories.

Monitoring of efficacy and safety of artemisinin-based anti-malarials for treatment of uncomplicated malaria: a review of evidence of implementation of anti-malarial therapeutic efficacy trials in Tanzania

BACKGROUND

Prompt diagnosis and effective treatment are considered the cornerstones of malaria control and artemisinin-based combination therapy (ACT) is currently the main anti-malarial drugs used for case management. After deployment of ACT due to widespread parasite resistance to the cheap and widely used anti-malarial drugs, chloroquine and sulphadoxine/pyrimethamine, the World Health Organization recommends regular surveillance to monitor the efficacy of the new drugs. The present paper assessed the implementation of anti-malarial efficacy testing for monitoring the therapeutic efficacy of ACT for treatment of uncomplicated malaria in Tanzania before and after policy changes in 2006.

METHODS

A literature search was performed for published clinical trials conducted in Tanzania from 2001 to 2014. It focused on studies which assessed at least one form of ACT for treatment of uncomplicated falciparum malaria in children less than 10 years and reported efficacy and safety of the tested anti-malarials. References were imported into the Endnote library and duplicates removed. An electronic matrix was developed in Microsoft Excel followed by full text review with predetermined criteria. Studies were independently assessed and information related to ACT efficacy and safety extracted.

RESULTS

Nine papers were selected from 125 papers screened. The efficacy of both artemether-lumefantrine (AL) and artesunate-amodiaquine (AS + AQ) against uncomplicated P. falciparum infections in Tanzania was high with PCR-corrected cure rates on day 28 of 91-100% and 88-93.8%, respectively. The highest day-3 parasite positivity rate was 1.4%. Adverse events ranged from mild to serious but were not directly attributed to the drugs.

CONCLUSION

ACT is efficacious and safe for treatment of uncomplicated malaria in Tanzania. However, few trials were conducted in Tanzania before and after policy changes in 2006 and thus more surveillance should be urgently undertaken to detect future changes in parasite sensitivity to ACT.

Fixed dose artesunate amodiaquine - a phase IIb, randomized comparative trial with non-fixed artesunate amodiaquine

Background

Pharmacokinetic (PK) and pharmacodynamic (PD) data are limited for artesunate (AS) and amodiaquine (AQ) in uncomplicated Plasmodium falciparum.

Methods

From 2007-8, 54 P. falciparum-infected, Kenyan adults were assigned randomly fixed dose (FD) ASAQ (n = 26) or non-fixed (NF) ASAQ (n = 28). Total doses were 600 mg AS (both arms) + 1,620 mg (FD) or 1,836 mg (NF)AQ. Follow-up extended over 28 days. PK data were collected for AS, dihydroartemisinin (DHA), AS + DHA combined as DHA equivalents (DHAeq), AQ, desethylamodiaquine (DAQ),and their relationships assessed against the PD collected data consisting of parasitological efficacy, adverse events (AEs), and the Bazett’s corrected QTinterval (QTcB).

Results

Mean AUC 0-72 of dihydroartemisinin equivalents (DHAeq) when administered as a fixed dose (FD) compared to NF dose were similar: 24.2 ±4.6 vs 26.4±6.9 µmol*h/L (p = 0.68) Parasite clearance rates were also similar after 24 hrs: 17/25 (68%) vs 18/28(64.3%) (p = 0.86),as well as at 48 hrs: 25/8 (100%)vs 26 (92.9%)/28 (p = 0.49). Mean FD vs NF DAQ AUC_0-28 were 27.6±3.19 vs 32.7±5.53 mg*h/L (p = 0.0005). Two PCR-proven new infections occurred on Day (D) 28 for estimated, in vivo, DAQ minimum inhibitory concentrations of 15.2 and 27.5 ng/mL. Combining the FD and NF arms, the mean QTcB at D2+4 hrs increased significantly (p = 0.0059) vs baseline: 420 vs410 ms (∆ = 9.02 (95% confidence interval 2.72-15.31 ms), explained by falling heart rates, increasing DAQ concentrations and female sex in a general linear mixed effects model. Ten of 108 (9.26%) AEs (5/arm) reported by 37/54 (68.5%) patients were possibly or probably drug related. Severe, asymptomatic neutropaenia developed in 2/47 (4.25%) patients on D28: 574/µL (vsD0: 5,075/µL), and 777/µL (vsD0: 3,778/µL).

Conclusions

Tolerability of both formulations was good. For QTcB, a parameter for ECG modifications, increases were modest and due to rising DAQ concentrations and falling heart rates as malaria resolved. Rapid parasite clearance rates and no resistant infections suggest effective pharmacokinetics of both formulations.

Electronic supplementary material

The online version of this article (doi:10.1186/1475-2875-13-498) contains supplementary material, which is available to authorized users.

Polymorphisms in Plasmodium falciparum chloroquine resistance transporter and multidrug resistance 1 genes: parasite risk factors that affect treatment outcomes for P. falciparum malaria after artemether-lumefantrine and artesunate-amodiaquine

Adequate clinical and parasitologic cure by artemisinin combination therapies relies on the artemisinin component and the partner drug. Polymorphisms in the Plasmodium falciparum chloroquine resistance transporter (pfcrt) and P. falciparum multidrug resistance 1 (pfmdr1) genes are associated with decreased sensitivity to amodiaquine and lumefantrine, but effects of these polymorphisms on therapeutic responses to artesunate-amodiaquine (ASAQ) and artemether-lumefantrine (AL) have not been clearly defined. Individual patient data from 31 clinical trials were harmonized and pooled by using standardized methods from the WorldWide Antimalarial Resistance Network. Data for more than 7,000 patients were analyzed to assess relationships between parasite polymorphisms in pfcrt and pfmdr1 and clinically relevant outcomes after treatment with AL or ASAQ. Presence of the pfmdr1 gene N86 (adjusted hazards ratio = 4.74, 95% confidence interval = 2.29 – 9.78, P < 0.001) and increased pfmdr1 copy number (adjusted hazards ratio = 6.52, 95% confidence interval = 2.36–17.97, P < 0.001) were significant independent risk factors for recrudescence in patients treated with AL. AL and ASAQ exerted opposing selective effects on single-nucleotide polymorphisms in pfcrt and pfmdr1. Monitoring selection and responding to emerging signs of drug resistance are critical tools for preserving efficacy of artemisinin combination therapies; determination of the prevalence of at least pfcrt K76T and pfmdr1 N86Y should now be routine.

Plasmodium falciparum clearance in clinical studies of artesunate-amodiaquine and comparator treatments in sub-Saharan Africa, 1999-2009

BACKGROUND

Artemisinin-based combination therapy (ACT) is the recommended first-line therapy for uncomplicated Plasmodium falciparum malaria worldwide but decreased artemisinin susceptibility, phenotypically characterized as slow parasite clearance time (PCT), has now been reported in Southeast Asia. This makes it all too important to measure the dynamics of parasite clearance in African patients treated with ACT over time, to understand trends and detect changes early enough to intervene

METHODS

Individual patient data from 27 clinical trials of artesunate-amodiaquine (ASAQ) vs comparators conducted between 1999 and 2009 were analysed for parasite clearance on modified intent-to-treat (ITT) basis.

RESULTS

Overall 15,017 patients treated for uncomplicated P. falciparum malaria at 44 sites in 20 sub-Saharan African countries were included in the analysis; 51% (n=7,660) vs 49% (n=7,357) were treated with ASAQ and comparator treatments, respectively. Seventy-seven per cent (77%) were children under six years of age. The proportion of the patients treated with ASAQ with persistent parasitaemia on Day 2 was 8.6%, and 1.5% on Day 3. Risk factor for not clearing parasites on Day 2 and Day 3 calculated by multivariate logistic regression with random effect on site and controlling for treatment were: high parasitaemia before treatment was (adjusted risk ratios (AOR) 2.12, 95% CI 1.91-2.35, AOR 2.43, 95% CI 1.98-3.00, respectively); non-ACT treatment (p=0.001, for all comparisons). Anaemia (p=0.001) was an additional factor for Day 2 and young age (p=0.005) for Day 3.In patients treated with ASAQ in studies who had complete parasitaemia data every 24 hours up to Day 3 and additionally Day 7, the parasite reduction ratio was 93.9% by Day 1 and 99.9% by Day 2. Using the median parasitaemia before treatment (p0=27,125 μL) and a fitted model, the predicted PCT (pPCT = 3.614*ln (p0) - 6.135, r(2) = 0.94) in ASAQ recipients was 31 hours.

CONCLUSION

Within the period covered by these studies, rapid Plasmodium falciparum clearance continues to be achieved in Sub-Saharan African patients treated with ACT, and in particular with ASAQ. The prediction formula for parasite clearance time could be a pragmatic tool for studies with binary outcomes and once-daily sampling, both for research and monitoring purposes.

Pharmacovigilance of malaria intermittent preventive treatment in infants coupled with routine immunizations in 6 African countries

BACKGROUND

Intermittent preventive treatment in infants (IPTi) is a new malaria control strategy coupled with the delivery of routine immunizations recommended by the World Health Organization since 2009 for countries with moderate to high endemicity. To evaluate its safety profile and identify potential new adverse events (AEs) following simultaneous administration of sulfadoxine-pyrimethamine (SP-IPTi) with immunizations, we measured AE incidence and evaluated spontaneous AE reporting.

METHODS

A cohort event monitoring study was conducted on 24 000 infants in 2 countries after administration of SP-IPTi during routine immunizations. Additional pharmacovigilance training and supervision were conducted to stimulate AE passive reporting in 6 African countries.

RESULTS

No serious AEs were found by active follow-up, representing 95% probability that the rate does not exceed 1 per 8000. No serious AEs were found by retrospective review of hospital registers. The rate of moderate AEs probably linked to immunization and/or SP-IPTi was 1.8 per 1000 doses (95% confidence interval, 1.50-2.00). Spontaneous reporting of AEs remained <1% of cases collected by active follow-up.

CONCLUSIONS

Simultaneous administration of SP-IPTi and immunizations is a safe strategy for implementation with a low risk of serious AEs to infants. Strategies toward strengthening spontaneous reporting in Africa should include not only the provider but also beneficiaries or their caregivers.

Comparing changes in haematologic parameters occurring in patients included in randomized controlled trials of artesunate-amodiaquine vs single and combination treatments of uncomplicated falciparum in sub-Saharan Africa

BACKGROUND

Artesunate-amodiaquine (AS&AQ) is a widely used artemisinin combination therapy (ACT) for falciparum malaria. A comprehensive appreciation of its effects on haematology vs other anti-malarials is needed in view of potential safety liabilities.

METHODS

Individual-patient data analysis conducted on a database from seven randomized controlled trials conducted in sub-Saharan African comparing AS&AQ to reference treatments in uncomplicated falciparum malaria patients of all ages. Haematologic values (white cells total and neutrophil counts, haemoglobin/haematocrit, platelets) were analysed as both continuous and categorical variables for their occurrence, (severity grade 1-4) and changes during follow-up. Risks and trends were calculated using multivariate logistic random effect models.

RESULTS

4,502 patients (72% < 5 years old), from 13 sites in nine countries with 28-day follow-up were treated with AS&AQ (45%) or a comparator (other forms of ACT accounted for 27%, other combination 12%, mono-therapies 16%). Pre-treatment leucopaenia (3%) and neutropaenia (6%) were infrequent; anaemia was common (39%). The treatment-emergent adverse events incidence (TEAE = condition not present or less severe pre-treatment) was 11% for neutropaenia, 6% for thrombocytopaenia with AS&AQ and not different from treatment groups; anaemia was higher with AS&AQ (20%) or other forms of ACT (22%) than in non-artemisinin groups (4%, p = 0.001). Multivariate analysis showed that the risk of anaemia, thrombocytopaenia, and leucopaenia decreased with follow-up time, while neutropaenia increased; the risk of anaemia and thrombocytopaenia increased with higher baseline parasitaemia and parasitological reappearance. White cells total count was not a good surrogate for neutropaenia. No systematic significant difference between treatments was detected. Older patients were at lower risks.

CONCLUSION

The effects of AS&AQ on haematologic parameters were not different from those of other anti-malarial treatments used in sub-Saharan Africa. This analysis provides the basis for a broader evaluation of haematology following anti-malarial treatment. Continuing monitoring of haematologic safety on larger databases is required.

Intermittent preventive treatment in infants for the prevention of malaria in rural Western kenya: a randomized, double-blind placebo-controlled trial

Background

Intermittent preventive treatment in infants (IPTi) with sulphadoxine-pyrimethamine (SP) for the prevention of malaria has shown promising results in six trials. However, resistance to SP is rising and alternative drug combinations need to be evaluated to better understand the role of treatment versus prophylactic effects.

Methods

Between March 2004 and March 2008, in an area of western Kenya with year round malaria transmission with high seasonal intensity and high usage of insecticide-treated nets, we conducted a randomized, double-blind placebo-controlled trial with SP plus 3 days of artesunate (SP-AS3), 3 days of amodiaquine-artesunate (AQ3-AS3), or 3 days of short-acting chlorproguanil-dapsone (CD3) administered at routine expanded programme of immunization visits (10 weeks, 14 weeks and 9 months).

Principal Findings

1,365 subjects were included in the analysis. The incidence of first or only episode of clinical malaria during the first year of life (primary endpoint) was 0.98 episodes/person-year in the placebo group, 0.74 in the SP-AS3 group, 0.76 in the AQ3-AS3 group, and 0.82 in the CD3 group. The protective efficacy (PE) and 95% confidence intervals against the primary endpoint were: 25.7% (6.3, 41.1); 25.9% (6.8, 41.0); and 16.3% (−5.2, 33.5) in the SP-AS3, AQ3-AS3, and CD3 groups, respectively. The PEs for moderate-to-severe anaemia were: 27.5% (−6.9, 50.8); 23.1% (−11.9, 47.2); and 11.4% (−28.6, 39.0). The duration of the protective effect remained significant for up to 5 to 8 weeks for SP-AS3 and AQ3-AS3. There was no evidence for a sustained beneficial or rebound effect in the second year of life. All regimens were well tolerated.

Conclusions

These results support the view that IPTi with long-acting regimens provide protection against clinical malaria for up to 8 weeks even in the presence of high ITN coverage, and that the prophylactic rather than the treatment effect of IPTi appears central to its protective efficacy.

Trial Registration

ClinicalTrials.gov NCT00111163

Molecular correlates of high-level antifolate resistance in Rwandan children with Plasmodium falciparum malaria

Antifolate drugs have an important role in the treatment of malaria. Polymorphisms in the genes encoding the dihydrofolate reductase and dihydropteroate synthetase enzymes cause resistance to the antifol and sulfa drugs, respectively. Rwanda has the highest levels of antimalarial drug resistance in Africa. We correlated the efficacy of chlorproguanil-dapsone plus artesunate (CPG-DDS+A) and amodiaquine plus sulfadoxine-pyrimethamine (AQ+SP) in children with uncomplicated malaria caused by Plasmodium falciparum parasites with pfdhfr and pfdhps mutations, which are known to confer reduced drug susceptibility, in two areas of Rwanda. In the eastern province, where the cure rates were low, over 75% of isolates had three or more pfdhfr mutations and two or three pfdhps mutations and 11% had the pfdhfr 164-Leu polymorphism. In the western province, where the cure rates were significantly higher (P < 0.001), the prevalence of multiple resistance mutations was lower and the pfdhfr I164L polymorphism was not found. The risk of treatment failure following the administration of AQ+SP more than doubled for each additional pfdhfr resistance mutation (odds ratio [OR] = 2.4; 95% confidence interval [CI] = 1.01 to 5.55; P = 0.048) and each pfdhps mutation (OR = 2.1; 95% CI = 1.21 to 3.54; P = 0.008). The risk of failure following CPG-DDS+A treatment was 2.2 times higher (95% CI = 1.34 to 3.7) for each additional pfdhfr mutation, whereas there was no association with mutations in the pfdhps gene (P = 0.13). The pfdhfr 164-Leu polymorphism is prevalent in eastern Rwanda. Antimalarial treatments with currently available antifol-sulfa combinations are no longer effective in Rwanda because of high-level resistance.

Efficacy of artesunate-amodiaquine for treating uncomplicated falciparum malaria in sub-Saharan Africa: a multi-centre analysis

BACKGROUND

Artesunate and amodiaquine (AS&AQ) is at present the world's second most widely used artemisinin-based combination therapy (ACT). It was necessary to evaluate the efficacy of ACT, recently adopted by the World Health Organization (WHO) and deployed over 80 countries, in order to make an evidence-based drug policy.

METHODS

An individual patient data (IPD) analysis was conducted on efficacy outcomes in 26 clinical studies in sub-Saharan Africa using the WHO protocol with similar primary and secondary endpoints.

RESULTS

A total of 11,700 patients (75% under 5 years old), from 33 different sites in 16 countries were followed for 28 days. Loss to follow-up was 4.9% (575/11,700). AS&AQ was given to 5,897 patients. Of these, 82% (4,826/5,897) were included in randomized comparative trials with polymerase chain reaction (PCR) genotyping results and compared to 5,413 patients (half receiving an ACT). AS&AQ and other ACT comparators resulted in rapid clearance of fever and parasitaemia, superior to non-ACT. Using survival analysis on a modified intent-to-treat population, the Day 28 PCR-adjusted efficacy of AS&AQ was greater than 90% (the WHO cut-off) in 11/16 countries. In randomized comparative trials (n = 22), the crude efficacy of AS&AQ was 75.9% (95% CI 74.6-77.1) and the PCR-adjusted efficacy was 93.9% (95% CI 93.2-94.5). The risk (weighted by site) of failure PCR-adjusted of AS&AQ was significantly inferior to non-ACT, superior to dihydroartemisinin-piperaquine (DP, in one Ugandan site), and not different from AS+SP or AL (artemether-lumefantrine). The risk of gametocyte appearance and the carriage rate of AS&AQ was only greater in one Ugandan site compared to AL and DP, and lower compared to non-ACT (p = 0.001, for all comparisons). Anaemia recovery was not different than comparator groups, except in one site in Rwanda where the patients in the DP group had a slower recovery.

CONCLUSION

AS&AQ compares well to other treatments and meets the WHO efficacy criteria for use against falciparum malaria in many, but not all, the sub-Saharan African countries where it was studied. Efficacy varies between and within countries. An IPD analysis can inform general and local treatment policies. Ongoing monitoring evaluation is required.

Existing antimalarial agents and malaria-treatment strategies

In the absence of prompt and efficacious treatment, malaria patients may progress within a few hours from having minor symptoms to severe disease and death. These last years have seen the development of several artemisinin-based combinations, new treatments for severe malaria patients, and new strategies such as intermittent preventive treatment or the home-based/near-home management of malaria. The health sector is now confronted with several treatment options and strategies, in contrast with the period when chloroquine monotherapy was the standard treatment. The major challenge remains the large-scale deployment, in the most efficient way, of the tools available today, including artemisinin-based combination treatments, within health systems that remain extremely weak in malaria endemic countries, particularly in sub-Saharan Africa. Health system research, exploring new potential approaches for the large-scale implementation of these interventions, should be promoted in parallel with that on new therapeutic agents to be used in the unlucky event of the emergence and spread of artemisinin resistance. The prospects of substantially decreasing the malaria burden are brighter today than 20 - 30 years ago, but the efforts and resources committed to this purpose should be maintained over a long period.

Safety and efficacy of dihydroartemisinin-piperaquine in falciparum malaria: a prospective multi-centre individual patient data analysis

Background

The fixed dose antimalarial combination of dihydroartemisinin-piperaquine (DP) is a promising new artemisinin-based combination therapy (ACT). We present an individual patient data analysis of efficacy and tolerability in acute uncomplicated falciparum malaria, from seven published randomized clinical trials conducted in Africa and South East Asia using a predefined in-vivo protocol. Comparator drugs were mefloquine-artesunate (MAS3) in Thailand, Myanmar, Laos and Cambodia; artemether-lumefantrine in Uganda; and amodiaquine+sulfadoxine-pyrimethamine and artesunate+amodiaquine in Rwanda.

Methods and Findings

In total 3,547 patients were enrolled: 1,814 patients (32% children under five years) received DP and 1,733 received a comparator antimalarial at 12 different sites and were followed for 28–63 days. There was no significant heterogeneity between trials. DP was well tolerated with 1.7% early vomiting. There were less adverse events with DP in children and adults compared to MAS3 except for diarrhea; ORs (95%CI) 2.74 (2.13 to 3.51) and 3.11 (2.31 to 4.18), respectively. DP treatment resulted in a rapid clearance of fever and parasitaemia. The PCR genotype corrected efficacy at Day 28 of DP assessed by survival analysis was 98.7% (95%CI 97.6–99.8). DP was superior to the comparator drugs in protecting against both P.falciparum recurrence and recrudescence (P = 0.001, weighted by site). There was no difference between DP and MAS3 in treating P. vivax co-infections and in suppressing the first relapse (median interval to P. vivax recurrence: 6 weeks). Children under 5 y were at higher risk of recurrence for both infections. The proportion of patients developing gametocytaemia (P = 0.002, weighted by site) and the subsequent gametocyte carriage rates were higher with DP (11/1000 person gametocyte week, PGW) than MAS3 (6/1000 PGW, P = 0.001, weighted by site).

Conclusions

DP proved a safe, well tolerated, and highly effective treatment of P.falciparum malaria in Asia and Africa, but the effect on gametocyte carriage was inferior to that of MAS3.

The efficacy and safety of a new fixed-dose combination of amodiaquine and artesunate in young African children with acute uncomplicated Plasmodium falciparum

Background

Artesunate (AS) plus amodiaquine (AQ) is one artemisinin-based combination (ACT) recommended by the WHO for treating Plasmodium falciparum malaria. Fixed-dose AS/AQ is new, but its safety and efficacy are hitherto untested.

Methods

A randomized, open-label trial was conducted comparing the efficacy (non-inferiority design) and safety of fixed (F) dose AS (25 mg)/AQ (67.5 mg) to loose (L) AS (50 mg) + AQ (153 mg) in 750, P. falciparum-infected children from Burkina Faso aged 6 months to 5 years. Dosing was by age. Primary efficacy endpoint was Day (D) 28, PCR-corrected, parasitological cure rate. Recipients of rescue treatment were counted as failures and new infections as cured. Documented, common toxicity criteria (CTC) graded adverse events (AEs) defined safety.

Results

Recruited and evaluable children numbered 750 (375/arm) and 682 (90.9%), respectively. There were 8 (AS/AQ) and 6 (AS+AQ) early treatment failures and one D7 failure (AS+AQ). Sixteen (AS/AQ) and 12 (AS+AQ) patients had recurrent parasitaemia (PCR new infections 10 and 6, respectively). Fourteen patients per arm required rescue treatment for vomiting/spitting out study drugs. Efficacy rates were 92.1% in both arms: AS/AQ = 315/342 (95% CI: 88.7–94.7) vs. AS+AQ = 313/340 (95% CI: 88.6–94.7). Non-inferiority was demonstrated at two-sided α = 0.05: Δ (AS+AQ – AS/AQ) = 0.0% (95% CI: -4.1% to 4.0%). D28, Kaplan Meier PCR-corrected cure rates (all randomized children) were similar: 93.7% (AS/AQ) vs. 93.2% (AS+AQ) Δ = -0.5 (95% CI -4.2 to 3.0%). By D2, both arms had rapid parasite (F & L, 97.8% aparasitaemic) and fever (97.2% [F], 96.0% [L] afebrile) clearances.

Both treatments were well tolerated. Drug-induced vomiting numbered 8/375 (2.1%) and 6/375 (1.6%) in the fixed and loose arms, respectively (p = 0.59). One patient developed asymptomatic, CTC grade 4 hepatitis (AST 1052, ALT 936). Technical difficulties precluded the assessment and risk of neutropaenia for all patients.

Conclusion

Fixed dose AS/AQ was efficacious and well tolerated. These data support the use of this new fixed dose combination for treating P. falciparum malaria with continued safety monitoring.

Trial registration

Current Controlled Trials ISRCTN07576538

In-vivo efficacy of amodiaquine-artesunate in children with uncomplicated Plasmodium falciparum malaria in western Kenya

OBJECTIVES

To assess the efficacy of amodiaquine-artesunate in an area with high chloroquine resistance in western Kenya.

METHODS

Twenty-eight day in-vivo efficacy trial of amodiaquine-artesunate in 103 children aged 6-59 months in western Kenya with smear-confirmed uncomplicated Plasmodium falciparum malaria.

RESULTS

The 28-day uncorrected adequate clinical and parasitological response (ACPR) was 69.0%, with 15.5% Late Clinical Failure and 15.5% Late Parasitologic Failure rates. The PCR-corrected 28-day ACPR was 90.2%. Clinical risk factors for recurrent infection (recrudescences and reinfections) were lower axillary temperature at enrollment and low weight-for-age Z-score. The presence of single nucleotide polymorphisms pfcrt 76T and pfmdr1 86Y at baseline was associated with increased risk of recurrent infections, both reinfections and recrudescences.

CONCLUSION

Although artemether-lumefantrine (Coartem) is the first line ACT in Kenya, amodiaquine-artesunate is registered as an option for treatment of uncomplicated P. falciparum and remains an effective alternative to Coartem in western Kenya. Continued amodiaquine monotherapy in the private sector may jeopardize the future use of amodiaquine-artesunate as an alternative artemisinin-based combination therapy.

Artemisinin-based combination therapy for uncomplicated malaria in sub-Saharan Africa: the efficacy, safety, resistance and policy implementation since Abuja 2000

Following increased resistance of malaria parasites to conventional drugs in the malarial regions of the world, the WHO is promoting artemisinin-based combination therapy (ACT) for treating uncomplicated malaria. The objective of this report is to review the available scientific information on the efficacy, safety, resistance and policy implementation of ACT as it relates to sub-Saharan Africa since the Abuja 2000 Roll Back Malaria initiative. To achieve this, a Medline search was performed to identify scientific publications relevant to the review. The data reviewed indicated that ACT proved very effective in the treatment of uncomplicated Plasmodium falciparum malaria in the region. ACT was shown to be effective, safe and tolerable and no resistance has been detected so far. However, the major challenges to its widespread use in the region include its high cost, low drug quality and poor healthcare delivery systems, among others. It is absolutely imperative for sub-Saharan African countries to establish an effective national antimalarial drug policy which will provide safe, effective, high-quality, accessible and affordable antimalarial drugs such as ACT to the populations at risk of malaria but, at the same time, promote rational drug use in order to delay or prevent the development of antimalarial drug resistance.

[Assessing the application of Rwanda's national protocol for uncomplicated malaria treatment in healthcare institutions in Kigali City, Rwanda]

In November 2001, the National Health Ministry of Rwanda advocated a new therapeutic protocol replacing chloroquine by an amodiaquine+sulfadoxine-pyrimethamine combination for the treatment of uncomplicated malaria.

OBJECTIVES

This study had for aim to assess the application of this new protocol in Kigali healthcare institutions.

POPULATION AND METHODS

A knowledge, attitudes and practices study (KAP) was carried out between June and August 2003. A questionnaire was answered by 120 care providers working in 15 healthcare institutions selected randomly in health facilities treating uncomplicated malaria. Antimalarial treatments prescribed to 150 patients were also reviewed from consultation files and analyzed.

RESULTS

After analysis, 63.3% prescriptions were in line with the national protocol. Factors associated to the nonobservance of the national protocol were: the carer's ignorance of any recommended treatment, his doubt of efficacy of recommended drugs, and his fear of adverse effects.

CONCLUSIONS

The authors recommend informing the care providers about the national protocol. Findings also demonstrate the need to include care providers in any modifications of the national policy in terms of drug efficacy and potential adverse effects of the new strategy.

Artesunate–amodiaquine for the treatment of uncomplicated malaria

Without an effective vaccine for the prevention of malaria, a fundamental component of the strategy for the control of this disease is based on prompt and effective treatment. Due to the high resistance level of Plasmodium falciparum to the most affordable drugs such as chloroquine and sulfadoxine-pyrimethamine, artemisinin-based combination therapies are presently used in many countries or are being developed for registration. One artemisinin combination therapy that is drawing a certain degree of interest is the combination of artesunate (a short half-life drug) plus amodiaquine (a long half-life drug that is presently used in loose combination in many countries). The short half-life drug achieves substantial and rapid parasite killing, while a high concentration of the long half-life drug kills off the remaining malaria parasites. In addition to the effectiveness of 3 days of treatment (rapid clearance of fever and malaria parasites) in western and central Africa, where resistance to amodiaquine is low, the combination of artesunate plus amodiaquine may delay or prevent the emergence of resistance to both drugs. An important step is the recent registration in Morocco (the country where the drug is manufactured) of a fixed combination of artesunate plus amodiaquine by the Drugs for Neglected Diseases initiative with sanofi-aventis as the industrial partner. A prequalification dossier of this fixed combination has been submitted to the WHO. This new co-formulation will almost certainly increase its effectiveness by improving drug compliance.

The use of genotyping in antimalarial clinical trials: a systematic review of published studies from 1995-2005

BACKGROUND

The use of genotyping to distinguish recrudescent from new infections is currently recommended for all clinical antimalarial efficacy trials by the World Health Organization. However, genotyping-adjusted drug efficacy estimates may vary between trials due to the use of different genotyping methods and to the different settings in which these methods are applied.

METHODS

A systematic review of all clinical antimalarial efficacy trials published from 1995-2005 was performed to characterize the use of genotyping, including the methods used and the effect of these methods on estimates of drug efficacy.

RESULTS

In a multivariate analysis, the method of interpretation of genotyping results, the studied therapy, the location of the trial, and the duration of study follow-up all had statistically significant effects on the percent of genotyped outcomes classified as new infections.

CONCLUSION

Criteria for defining appropriate, standardized genotyping methods for use in different settings are needed to enable more accurate estimates of antimalarial drug efficacy and better comparison between trials. The advantages and disadvantages of different genotyping methods and their potential impact in various settings are discussed.

Safety and efficacy of dihydroartemisinin/piperaquine (Artekin®) for the treatment of uncomplicated Plasmodium falciparum malaria in Rwandan children

In Rwanda, amodiaquine+sulfadoxine/pyrimethamine (AQ+SP) is the current first-line treatment for malaria, introduced in 2001 as an interim strategy before the future deployment of an artemisinin-based combination treatment (ACT). Dihydroartemisinin/piperaquine (DHA-PQP) is a new co-formulated and well tolerated ACT increasingly used in Southeast Asia where it has proved to be highly effective against Plasmodium falciparum malaria. We tested the efficacy, safety and tolerability of DHA-PQP in children with uncomplicated P. falciparum malaria. A randomised, open trial was carried out in 2003-2004. Seven hundred and sixty-two children aged 12-59 months with uncomplicated P. falciparum malaria were randomly allocated to one of the following treatments: amodiaquine+artesunate; AQ+SP; or DHA-PQP. Patients were followed-up until Day 28 after treatment. Adverse events and clinical and parasitological outcomes were recorded. Children treated with DHA-PQP or AQ+AS had a significantly higher cure rate compared with those treated with amodiaquine+sulfadoxine/pyrimethamine (95.2% and 92.0% vs. 84.7%, respectively). Parasite clearance was significantly faster in children treated with DHA-PQP and AQ+AS compared with those treated with amodiaquine+sulfadoxine/pyrimethamine. The frequency of adverse events was significantly lower in patients treated with DHA-PQP than in those treated with combinations containing amodiaquine. A 3-day treatment with DHA-PQP proved to be efficacious with a good safety and tolerability profile and could be a good candidate for the next first-line treatment.

Artesunate�+�amodiaquine and artesunate�+�sulphadoxine?pyrimethamine for treatment of uncomplicated malaria in Democratic Republic of Congo: a clinical trial with determination of sulphadoxine and pyrimethamine-resistant haplotypes

We undertook a trial of artesunate + amodiaquine (AS + AQ) and artesunate + sulphadoxine-pyrimethamine (AS + SP) in 180 children of age 6-59 months with uncomplicated malaria in Democratic Republic of Congo. Children were randomly allocated to receive 3 days observed treatment of AS + AQ (n = 90) or 3 days of AS + SP (n = 90). Primary efficacy outcomes were 28-day parasite recurrence rates, and recrudescence rates were adjusted by genotyping to distinguish new infection and recrudescence. In addition, we determined the prevalence of molecular markers of resistance to sulphadoxine and pyrimethamine. Day 28 parasite recurrence rates were 16.9% (14/83; 95% CI: 9.5-26.7) in the AS + AQ group and 34.6% (28/81; 95% CI: 24.3-46.0) in the AS + SP group (P = 0.009). After PCR correction, recrudescence rates were 6.7% (5/74; 95% CI: 2.2-15.1) for AS + AQ and 19.7% (13/66; 95% CI: 10.9-31.3) for AS + SP (P = 0.02). There was no significant difference between the two arms in time to parasite clearance, fever clearance and gametocyte clearance. Parasite genotyping showed high frequencies of dihydrofolate reductase (dhfr) and dihydropteroate synthase (dhps) molecular SP-resistance markers, with 57% of the samples showing more than three mutations linked to SP resistance, and 27% with triple-dhfr/double-dhps haplotype, confirming that SP treatment failure rates are likely to be high. AS + AQ had significantly higher efficacy than AS + SP. These results contributed to the subsequent change to AS + AQ as first-line regimen in the country. Efforts to properly implement the new protocol and maintain adherence at acceptable levels should include health staff and patient sensitization. The 6.8% recrudescence rate indicates that AS + AQ should be monitored closely until a more effective artemisinin combination therapy regimen is needed and can be introduced.

Low efficacy of the combination artesunate plus amodiaquine for uncomplicated falciparum malaria among children under 5 years in Kailahun, Sierra Leone

OBJECTIVE

In 2004, Sierra Leone adopted artesunate plus amodiaquine as first-line antimalarial treatment. We evaluated the efficacy of this combination in Kailahun, where a previous study had shown 70.2% efficacy of amodiaquine in monotherapy.

METHODS

Method and outcome classification of the study complied with WHO guidelines. Children 6-59 months with uncomplicated malaria were followed-up for 28 days. PCR genotyping was used to distinguish recrudescence from reinfection. Reinfections were reclassified as cured.

RESULTS

Of 172 children who were referred to the study clinic, 126 satisfied inclusion criteria and were enrolled. No early treatment failures were reported. The day 14, efficacy was 98.2% (95% CI: 93.8-99.8). Of 65 recurrent parasitaemias analysed by PCR, 17 were recrudescences. The PCR-adjusted day 28 efficacy was 84.5% (95% CI: 76.4-90.7). All true failures occurred in the last 8 days of follow-up. Of 110 children who completed the 28-day follow-up, 54 (49.1%) experienced a novel infection.

CONCLUSION

The efficacy of this combination was disappointing. The high reinfection rate suggested little prophylactic effect. In Kailahun a more efficacious combination might be necessary in the future. The efficacy of AS + AQ needs to be monitored in Kailahun and in the other regions of Sierra Leone.

Pharmacovigilance of antimalarial treatment in Africa: is it possible?

Pharmacovigilance, defined as "the science and activities relating to the detection, assessment, understanding and prevention of adverse effects or any other possible drug related problem", is increasingly being recognized in Africa. Many African countries have simultaneously adopted artemisinin derivative based combination therapy (ACT) as first-line treatment for uncomplicated malaria, offering an opportunity to assess the safety of these drugs when used widely. While ACTs appear to be safe and well-tolerated, there is little experience with these medicines in Africa, outside clinical trials. Pharmacovigilance for ACTs and other combination treatments in Africa is essential. Malaria transmission intensity is high and antimalarial medicines are used frequently. Presumptive treatment of fever with antimalarials is common, often in the absence of a confirmed diagnosis, using drugs obtained without a prescription. Informal use of antimalarial drugs may increase the risk of incorrect dosing, inappropriate treatment, and drug interactions, which may impact negatively on drug safety. Furthermore, the administration of antimalarial treatments in patients with a concomitant illness, including HIV/AIDs, tuberculosis and malnutrition, is a concern. African countries are being encouraged to establish pharmacovigilance systems as ACTs are rolled out. However, pharmacovigilance is difficult, even in countries with a well-developed health care system. The rationale for pharmacovigilance of antimalarial drugs is discussed here, outlining the practical challenges and proposing approaches that could be adopted in Africa.

Efficacy of chloroquine, sulfadoxine–pyrimethamine and amodiaquine for treatment of uncomplicated Plasmodium falciparum malaria among children under five in Bongor and Koumra, Chad

We report two 28-day in-vivo antimalarial efficacy studies carried out in the urban centres of Bongor and Koumra, southern Chad. We assess chloroquine (CQ), sulfadoxine-pyrimethamine (SP) and amodiaquine (AQ) to treat Plasmodium falciparum uncomplicated malaria. Methods and outcome classification complied with latest WHO guidelines. Out of the 301 and 318 children aged 6-59 months included in Bongor and Koumra, respectively, 246 (81.7%) and 257 (80.8%) were eligible for analysis. In Bongor and Koumra, the 28-day PCR-adjusted failure rates for CQ were 23.7% (95% CI 14.7-34.8%) and 32.9% (95% CI 22.1-45.1%), respectively, and those for SP were 16.3% (95% CI 9.4-25.5%) and 4.3% (95% CI 1.2-10.5%). AQ failure rates were 6.4% (95% CI 2.1-14.3%) and 2.2% (95% CI 0.3-7.6%). The current use of CQ in Bongor and Koumra is questionable, and a more efficacious treatment is needed. Considering the reduced efficacy of SP in Bongor, AQ seems to be the best option for the time being. Following WHO recommendations that prioritize the use of artemisinin-based combinations, artesunate plus amodiaquine could be a potential first-line treatment. Nevertheless, the efficacy of this combination should be evaluated and the change carefully prepared, implemented and monitored.

Tolerability of amodiaquine and sulphadoxine-pyrimethamine, alone or in combination for the treatment of uncomplicated Plasmodium falciparum malaria in Rwandan adults

OBJECTIVE

To assess the tolerability and efficacy of amodiaquine (AQ)+sulphadoxine-pyrimethamine (SP), the first-line malaria treatment in Rwanda.

METHOD

Randomized, double-blind trial in 2003 in Kigali town. A total of 351 adult patients with uncomplicated Plasmodium falciparum malaria were randomly allocated to one of the following treatments: AQ+SP, AQ or SP. We followed patients until day 14 after treatment and recorded adverse events (AEs) and clinical and parasitological outcomes.

RESULTS

One hundred and eighteen patients reported at least one AE: 40% in the AQ, 39% in the AQ+SP and 21% in the SP groups. The AE was classified as possibly related to the antimalarial treatment for 86 patients. The Risk Ratio for at least one AE after treatment was significantly and about fourfold higher in patients receiving AQ or AQ+SP than in patients receiving SP. Pruritus and fatigue were significantly more frequent in patients treated with AQ or AQ+SP than in those receiving SP. Severe AEs, such as fatigue, nausea, dizziness and vomiting, were observed in four patients treated with AQ, in 10 treated with AQ+SP and in one patient treated with SP.

CONCLUSION

Amodiaquine+SP is not well tolerated and a substantial proportion of patients experienced pruritus and fatigue, thus decreasing their compliance and compromising the first line treatment implementation at national level. This renders AQ-containing regimens sub-optimal; better-tolerated treatments should be identified.

In-vitro susceptibility of Plasmodium falciparum to monodesethylamodiaquine, dihydroartemisinin and quinine in an area of high chloroquine resistance in Rwanda

Plasmodium falciparum in-vitro susceptibility to chloroquine (CQ), monodesethylamodiaquine, quinine and dihydroartemisinin was investigated in Rwandan patients with a parasitaemia of at least >or=4000/microl. The study was carried out in November-December 2003. Dihydroartemisinin was the most potent (GM IC(50)=2.6nmol/l, 95% CI 2.2-3.2) among the drugs tested. Resistance to chloroquine was 45% (33/74) and that to monodesethylamodiaquine 7% (5/74). All the tested isolates were susceptible to quinine. The mean IC(50) of monodesethylamodiaquine, quinine and dihydroartemisinin was significantly higher for chloroquine-resistant than for chloroquine-sensitive strains (P<0.05). The IC(50) of each drug was significantly and positively correlated to that of the other three drugs (P<0.005), and this correlation was higher between CQ and monodesethylamodiaquine (r=0.8). In-vitro CQ resistance is linked to that of the other drugs tested. Most worrying is the positive correlation between the IC(50) of dihydroartemisinin and the other drugs, more particularly with CQ, suggesting an increased tolerance of the parasites to all drugs.

Efficacy of Artesunate Plus Amodiaquine versus That of Artemether-Lumefantrine for the Treatment of Uncomplicated Childhood Plasmodium falciparum Malaria in Zanzibar, Tanzania

BACKGROUND

This is the first clinical trial comparing the efficacy of artesunate plus amodiaquine (ASAQ) and artemether-lumefantrine (AL)--the major artemisinin-based combination therapy (ACT) candidates for treatment of malaria in Africa--that involved an extended, 42-day follow-up period, polymerase chain reaction-adjusted parasitological cure rates (PCR APCRs), and systematic analyses of genetic markers related to quinoline resistance. METHODS. A total of 408 children with uncomplicated Plasmodium falciparum malaria in Zanzibar, Tanzania, were enrolled. Children who were 6-8 months of age and/or who weighed 6-8 kg were assigned to receive ASAQ for 3 days. Children who were 9-59 months of age and who weighted > or =9 kg were randomly assigned to receive either ASAQ or AL for 3 days in standard doses. Intention-to-treat analyses were performed.

RESULTS

Age- and weight-adjusted PCR-APCRs by follow-up day 42 were 91% (188 of 206 patients) in the ASAQ group and 94% (185 of 197 patients) in the AL group (odds ratio [OR] for the likelihood of cure, 2.07; 95% confidence interval [CI], 0.84-5.10; P=.115). A total of 5 and 7 recrudescences occurred after day 28 in the ASAQ and AL groups, respectively. On the assumption that 10 malaria episodes with uncertain PCR results were recrudescences, PCR-APCRs decreased to 88% in the ASAQ group and to 92% in the AL group. Unadjusted cure rates by day 42 were 56% (116 of 206 patients) in the ASAQ group versus 77% (151 of 197 patients) in the AL group (OR, 2.55; 95% CI, 1.66-3.91; P<.001). Rates of reinfection by day 42 were 36% (65 of 181 patients) in the ASAQ arm versus 17% (31 of 182 patients) in the AL arm (OR, 0.37; 95% CI, 0.22-0.60; P<.001). A significant selection of P. falciparum multidrug resistance gene 1 allele 86N was found in isolates associated with reinfection after AL treatment, compared with isolates at baseline (2.2-fold increase; P<.001).

CONCLUSIONS

Both treatments were highly efficacious, but AL provided stronger prevention against reinfection. The high proportion of recrudescences found after day 28 and the genetic selection by the long-acting partner drug underlines the importance of long follow-up periods in clinical trials. A long follow-up duration and performance of PCR genotyping should be implemented in programmatic surveillance of antimalarial drugs.

Evidence basis for antimalarial policy change in Sierra Leone: five in vivo efficacy studies of chloroquine, sulphadoxine-pyrimethamine and amodiaquine

OBJECTIVES

To provide nationally relevant information on the antimalarial efficacy of chloroquine (CQ), sulphadoxine-pyrimethamine (SP) and amodiaquine (AQ) in Sierra Leone, with a view to updating antimalarial policy in the country.

METHODS

Between October 2002 and May 2003, standard WHO methodology for in vivo efficacy assessment was used in five sites to study the therapeutic response of 6-59 months old uncomplicated Plasmodium falciparum malaria cases treated with CQ (n = 247), SP (n = 353) or AQ (n = 434). Follow-up was of 28 days, with polymerase chain reaction genotyping to distinguish late recrudescences from re-infections.

RESULTS

Overall 85.3% of patients reached an analysable endpoint. CQ failure proportions were very high, ranging from 39.5% (95% CI: 25.0-55.6) in Kabala to 78.8% (65.3-88.9) in Kailahun. Early failures under CQ were frequent. SP efficacy was also disappointing, with failure from 23.2% (13.9-34.9) in Kabala to 46.1% (35.4-57.0) in Kailahun. AQ resistance was more moderate, ranging from 5.4% (1.8-12.1) in Makeni to 29.8% (20.3-40.8) in Kailahun, with almost no early failures. AQ also provided more rapid fever and parasite clearance.

CONCLUSION

In a consensus meeting organized by the Ministry of Health and Sanitation, and based on these findings, artesunate (AS) + AQ and artemether-lumefantrine (Coartemtrade mark) were identified as the only options to rapidly replace CQ. The choice fell on AS + AQ because of expected high efficacy, lower cost in a blister presentation, and the absence of safety data on artemether-lumefantrine in pregnancy. Donor support is required to support this policy change. Throughout Africa, as SP resistance increases, these two regimens are probably the only options available while newer combinations are developed. Efficacy studies should focus on testing AQ and AS + AQ.