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Atoguanil™ is a novel complex of atovaquone (ATV) and proguanil (PG) with enhanced ATV bioavailability compared to Malarone®. This pilot study assessed whether the relative bioavailability (F rel ) of ATV, PG, and the primary PG metabolite cycloguanil (CG) following a single oral dose in the fed state of Atoguanil was similar to Malarone despite a 50% lower ATV dose. This open-label, single-dose, randomized 2-period, 2-treatment, balanced crossover study was conducted between 17th November 2021 and 18th March 2022. Eligible participants (aged 18–55 years) were randomized (1:1) in period 1 to Atoguanil (ATV/PG 500/348 mg) or Malarone (ATV/PG hydrochloride 1000/400 mg) administered following a high-fat, high caloric meal. After a 24-day washout period, participants crossed treatment arms. For the doses tested, F rel was assumed similar if 90%CIs were between 80 and 125% for the geometric mean ratio of the least square mean differences for each exposure parameter. In 15 evaluable participants, F rel was similar for ATV C max (93.6% [90%CI 83.6, 104.9]) but not AUC 0-inf (77.8% [67.4, 89.8]), for PG AUC 0-inf (95.6% [92.1, 99.2]) but not C max (82.4% [75.8, 89.5]), and for both CG C max (100.8% [95.0, 107.0]) and AUC 0-inf (102.9% [98.4, 107.7]). Nine adverse events occurred; all were of mild severity and not considered treatment related. At the doses tested, ATV F rel was lower following Atoguanil versus Malarone based on AUC 0-inf , though when adjusted for dose F rel increased by 156%. Both drugs were well tolerated with no safety concerns. ClinicalTrials.gov: NCT04866602 (April 26th, 2021)

Administration of sulfadoxine-pyrimethamine at times of vaccination—intermittent preventive treatment in infants (IPTi)—is a promising strategy to prevent malaria. However, rising resistance to this combination is a concern. We investigated a shortacting and longacting antimalarial drug as alternative regimens for IPTi. We undertook a double-blind, placebo-controlled trial of IPTi in an area of high resistance to sulfadoxine-pyrimethamine at sites of moderate (n=1280 infants enrolled) and low (n=1139) intensity of malaria transmission in Tanzania. Infants aged 8–16 weeks were randomly assigned in blocks of 16 to sulfadoxine (250 mg) plus pyrimethamine (12·5 mg; n=319 in moderate-transmission and 283 in low-transmission sites), chlorproguanil (15 mg) plus dapsone (18·75 mg; n=317 and 285), mefloquine (125 mg; n=320 and 284), or placebo (n=320 and 284), given at the second and third immunisations for diphtheria, pertussis, and tetanus, and for measles. Research team and child were masked to treatment. Recruitment was stopped early at the low-transmission site because of low malaria incidence. The primary endpoint was protective efficacy against all episodes of clinical malaria at 2–11 months of age. Analysis was by intention to treat. This study is registered with ClinicalTrials.gov, number NCT00158574. All randomly assigned infants were analysed. At the moderate-transmission site, mefloquine had a protective efficacy of 38·1% (95% CI 11·8–56·5, p=0·008) against clinical malaria in infants aged 2–11 months, but neither sulfadoxine-pyrimethamine (−6·7%, −45·9 to 22·0) nor chlorproguanil-dapsone (10·8%, −24·6 to 36·1) had a protective effect. No regimen had any protective efficacy against anaemia or hospital admission. Mefloquine caused vomiting in 141 of 1731 (8%) doses given on day 1 (odds ratio vs placebo 5·50, 95% CI 3·56–8·46). More infants died in the chlorproguanil-dapsone and mefloquine groups (18 and 15, respectively) than in the sulfadoxine-pyrimethamine or placebo groups (eight deaths per group; p=0·05 for difference between chlorproguanil-dapsone and placebo). IPTi with a longacting, efficacious drug such as mefloquine can reduce episodes of malaria in infants in a moderate-transmission setting. IPTi with sulfadoxine-pyrimethamine has no benefit in areas of very high resistance to this combination. The appropriateness of IPTi should be measured by the expected incidence of malaria and the efficacy, tolerability, and safety of the drug. IPTi Consortium and the Gates Malaria Partnership.

Chlorproguanil-dapsone (CD) has been linked to hemolysis in symptomatic glucose-6-phosphate dehydrogenase deficient (G6PDd) children. Few studies have explored the effects of G6PD status on hemolysis in children treated with Intermittent Preventive Treatment in infants (IPTi) antimalarial regimens. We sought to examine the joint effects of G6PD status and IPTi antimalarial treatment on incidence of hemolysis in asymptomatic children treated with CD, sulfadoxine-pyrimethamine (SP), and mefloquine (MQ). A secondary analysis of data from a double-blind, placebo-controlled trial of IPTi was conducted. Hemoglobin (Hb) measurements were made at IPTi doses, regular follow-up and emergency visits. G6PD genotype was determined at 9 months looking for SNPs for the A- genotype at coding position 202. Multivariable linear and logistic regression models were used to examine hemolysis among children with valid G6PD genotyping results. Hemolysis was defined as the absolute change in Hb or as any post-dose Hb <8 g/dL. These outcomes were assessed using either a single follow-up Hb on day 7 after an IPTi dose or Hb obtained 1 to 14 or 28 days after each IPTi dose. Relative to placebo, CD reduced Hb by approximately 0.5 g/dL at day 7 and within 14 days of an IPTi dose, and by 0.2 g/dL within 28 days. Adjusted declines in the CD group were larger than in the MQ and SP groups. At day 7, homo-/hemizygous genotype was associated with higher odds of Hb <8 g/dL (adjusted odds ratio = 6.7, 95% CI 1.7 to 27.0) and greater absolute reductions in Hb (-0.6 g/dL, 95% CI -1.1 to 0.003). There was no evidence to suggest increased reductions in Hb among homo-/hemizygous children treated with CD compared to placebo, SP or MQ. While treatment with CD demonstrated greater reductions in Hb at 7 and 14 days after an IPTi dose compared to both SP and MQ, there was no evidence that G6PD deficiency exacerbated the adverse effects of CD, despite evidence for higher hemolysis risk among G6PDd infants.

Chlorproguanil-dapsone (Lapdap), developed as a low-cost antimalarial, was withdrawn in 2008 after concerns about safety in G6PD deficient patients. This trial was conducted in 2004 to evaluate the safety and effectiveness of CD and comparison with artemether-lumefantrine (AL) under conditions of routine use in G6PD normal and G6PD deficient patients with uncomplicated malaria in The Gambia. We also examined the effects of a common genetic variant that affects chlorproguanil metabolism on risk of treatment failure. 1238 children aged 6 months to 10 years with uncomplicated malaria were randomized to receive CD or artemether-lumefantrine (AL) and followed for 28 days. The first dose was supervised, subsequent doses given unsupervised at home. G6PD genotype was determined to assess the interaction between treatment and G6PD status in their effects on anaemia. The main endpoints were clinical treatment failure by day 28, incidence of severe anaemia (Hb<5 g/dL), and haemoglobin concentration on day 3. One third of patients treated with AL, and 6% of patients treated with CD, did not complete their course of medication. 18% (109/595) of children treated with CD and 6.1% (36/587) with AL required rescue medication within 4 weeks, risk difference 12% (95%CI 8.9%-16%). 23 children developed severe anaemia (17 (2.9%) treated with CD and 6 (1.0%) with AL, risk difference 1.8%, 95%CI 0.3%-3.4%, P = 0.02). Haemoglobin concentration on day 3 was lower among children treated with CD than AL (difference 0.43 g/dL, 95% CI 0.24 to 0.62), and within the CD group was lower among those children who had higher parasite density at enrollment. Only 17 out of 1069 children who were typed were G6PD A- deficient, of these 2/9 treated with CD and 1/8 treated with AL developed severe anaemia. 5/9 treated with CD had a fall of 2 g/dL or more in haemoglobin concentration by day 3. AL was well tolerated and highly effective and when given under operational conditions despite poor adherence to the six-dose regimen. There were more cases of severe malaria and anaemia after CD treatment although G6PD deficiency was uncommon. Clinicaltrials.gov NCT00118794.

Background. We conducted a randomized, placebo-controlled, double-blind trial to establish the efficacy of atovaquone-proguanil to prevent malaria with the goal of simulating weekly dosing in a human Plasmodium falciparum challenge model. Methods. Thirty volunteers randomly received 1 of the following dose regimens: (1) 250 milligrams of atovaquone and 100 milligrams of proguanil (250/100 milligrams) 1 day prior to infectious mosquito challenge (day -1), (2) 250/100 milligrams on day 4 after challenge, (3) 250/100 milligrams on day -7 , (4) 500 milligrams of atovaquone and 200 milligrams of proguanil (500/200 milligrams) on day -7 or, (5) 1000 milligrams of atovaquone and 400 milligrams of proguanil (1000/400 milligrams) on day — 7. All regimens included matching placebo such that all volunteers received identical pill numbers. Six volunteers served as open-label infectivity controls. Volunteers underwent mosquito sporozoite challenge with P. falciparum 3D7 strain. Follow-up consisted of serial microscopy and close clinical monitoring for 90 days. Results. Six of 6 infectivity controls developed parasitemia as expected. Two of 5 evaluable volunteers receiving 250/100 milligrams 7 days prior to challenge and 1 of 6 volunteers receiving 1000/400 milligrams 7 days prior to challenge were microscopically diagnosed with malaria. All other volunteers were protected. Atovaquone exposure (area under the curve) during liver stage development was low in 2 of 3 volunteers with prophylactic failure (423 and 199 ng/mL X days compared with a mean for protected volunteers of 1903 ng/mL X days), as was peak concentration (165 and 81 ng/mL compared with a mean of 594 ng/mL in volunteers with prophylactic success). Elimination half-life was short in volunteers with prophylactic failure (2.4,2.0, and 3.3 days compared with a mean of 4.1 days in volunteers with prophylactic success). Conclusions. Single-dose atovaquone-proguanil provides effective malaria chemoprophylaxis against P. falciparum challenge at dosing intervals supportive of weekly dosing. Postexposure prophylaxis 4 days after challenge was 100% effective.

Concerns about the tolerability of mefloquine highlight the need for new drugs to prevent malaria. Atovaquone-proguanil (Malarone; GlaxoSmithKline) was safe and effective for prevention of falciparum malaria in lifelong residents of malaria-endemic countries, but experience in nonimmune people is limited. In a randomized, double-blind study, nonimmune travelers received malaria prophylaxis with atovaquone-proguanil (493 subjects) or mefloquine (483 subjects). Information about adverse events (AEs) and potential episodes of malaria was obtained 7, 28, and 60 days after travel. AEs were reported by an equivalent proportion of subjects who had received atovaquone-proguanil or mefloquine (71.4% versus 67.3%; difference, 4.1%; 95% confidence interval, -1.71 to 9.9). Subjects who received atovaquone-proguanil had fewer treatment-related neuropsychiatric AEs (14% versus 29%; P = .001), fewer AEs of moderate or severe intensity (10% versus 19%; P = .001), and fewer AEs that caused prophylaxis to be discontinued (1.2% versus 5.0%; P = .001), compared with subjects who received melfoquine. No confirmed diagnoses of malaria occurred in either group. Atovaquone-proguanil was better tolerated than was mefloquine, and it was similarly effective for malaria prophylaxis in nonimmune travelers.

Increasing resistance to sulfadoxine-pyrimethamine is leading to a decline in its effectiveness. We aimed to assess the safety profile of chlorproguanil-dapsone (CD), and to compare the safety and efficacy of this drug with that of sulfadoxine-pyrimethamine (SP) as treatment for uncomplicated falciparum malaria. We undertook a double-blind, randomised trial in 1850 consecutively recruited children with uncomplicated falciparum malaria, pooling data from five African countries. Analyses were based on all randomised patients with available data. CD was significantly more efficacious than SP (odds ratio 3·1 [95% CI 2·0–4·8]); 1313 patients (96%) given CD and 306 (89%) given SP achieved acceptable clinical and parasitological response by day 14. Adverse events were reported in 46% and 50% of patients randomised to CD and SP, respectively (treatment difference −4·4%, [95% CI −10·1 to 1·3]). Haemoglobin in the CD group was significantly lower than in the SP group at day 7, a difference of −4 g/L (95% CI −6 to −2). Mean day 14 haemoglobin (measured only for the small number of patients whose day 7 data caused concern) was 94 g/L (92–96) and 97 g/L (92–102) after CD and SP, respectively. Glucose-6-phosphate dehydrogenase deficient patients on CD had greater odds than those on SP of having a fall of 20 g/dL or more in haemoglobin when baseline temperature was high. Methaemoglobinaemia was seen in the CD group (n=320, mean 0·4% [95% CI 0·4–0·4]) before treatment, 4·2% (95% CI 3·8–4·6) (n=301) at day 3, and 0·6% (0·6–0·7) (n=300) at day 7). CD had greater efficacy than SP in Africa and was well tolerated. Haematological adverse effects were more common with CD than with SP and were reversible. CD is a useful alternative where SP is failing due to resistance.

Background Malaria is a leading cause of mortality, particularly in sub-Saharan African children. Prompt and efficacious treatment is important as patients may progress within a few hours to severe and possibly fatal disease. Chlorproguanil-dapsone-artesunate (CDA) was a promising artemisinin-based combination therapy (ACT), but its development was prematurely stopped because of safety concerns secondary to its associated risk of haemolytic anaemia in glucose-6-phosphate dehydrogenase (G6PD)-deficient individuals. The objective of the study was to assess whether CDA treatment and G6PD deficiency are risk factors for a post-treatment haemoglobin drop in African children <5 years of age with uncomplicated malaria. Methods This case–control study was performed in the context of a larger multicentre randomized clinical trial comparing safety and efficacy of four different ACT in children with uncomplicated malaria. Children, who after treatment experienced a haemoglobin drop ≥2 g/dl (cases) within the first four days (days 0, 1, 2, and 3), were compared with those without an Hb drop (controls). Cases and controls were matched for study site, sex, age and baseline haemoglobin measurements. Data were analysed using a conditional logistic regression model. Results G6PD deficiency prevalence, homo- or hemizygous, was 8.5% (10/117) in cases and 6.8% (16/234) in controls (p = 0.56). The risk of a Hb drop ≥2 g/dl was not associated with either G6PD deficiency (adjusted odds ratio (AOR): 0.81; p = 0.76) or CDA treatment (AOR: 1.28; p = 0.37) alone. However, patients having both risk factors tended to have higher odds (AOR: 11.13; p = 0.25) of experiencing a Hb drop ≥2 g/dl within the first four days after treatment, however this finding was not statistically significant, mainly because G6PD deficient patients treated with CDA were very few. In non-G6PD deficient individuals, the proportion of cases was similar between treatment groups while in G6PD-deficient individuals, haemolytic anaemia occurred more frequently in children treated with CDA (56%) than in those treated with other ACT (29%), though the difference was not significant (p = 0.49). Conclusion The use of CDA for treating uncomplicated malaria may increase the risk of haemolytic anaemia in G6PD-deficient children.

The increasing prevalence of resistance to antimalarial drugs reduces options for malaria prophylaxis. Atovaquone/proguanil (Malarone; GlaxoSmithKline) has been >95% effective in preventing Plasmodium falciparum malaria in lifelong residents of areas of holoendemicity, but data from persons without clinical immunity or who are at risk for Plasmodium vivax malaria have not been described. We conducted a randomized, double-blinded study involving 297 people from areas of nonendemicity in Indonesia who migrated to Papua (where malaria is endemic) ⩽26 months before the study period. Subjects received prophylaxis with 1 Malarone tablet (250 mg of atovaquone and 100 mg of proguanil hydrochloride; n = 148) or placebo (n = 149) per day for 20 weeks. Hematologic and clinical chemistry values did not change significantly. The protective efficacy of atovaquone/proguanil was 84% (95% confidence interval [CI], 44%–95%) for P. vivax malaria, 96% (95% CI, 72%–99%) for P. falciparum malaria, and 93% (95% CI, 77%–98%) overall. Atovaquone/proguanil was well tolerated, safe, and effective for the prevention of drug-resistant P. vivax and P. falciparum malaria in individuals without prior malaria exposure who migrated to Papua, Indonesia.

Chlorproguanil-dapsone exerts lower resistance pressure on Plasmodium falciparum than does sulfadoxine-pyrimethamine, but is rapidly eliminated. We aimed to find out whether chlorproguanil-dapsone results in a higher retreatment rate for malaria than sulfadoxine-pyrimethamine. In a randomised trial of paediatric outpatients with uncomplicated falciparum malaria, patients received either chlorproguanil-dapsone or sulfadoxine-pyrimethamine and were followed up for up to 1 year. Sites were in Kenya (n=410) and Malawi (n=500). We used perprotocol analysis to assess the primary outcome of annual malaria incidence. Drop-outs were 117 of 410 (28·5%) in Kenya, and 342 of 500 (68·4%) in Malawi. Follow-up was for a median of 338 days (IQR 128–360) and 342 days (152–359) in Kilifi (chlorproguanil-dapsone and sulfadoxine-pyrimethamine, respectively), and for 120 days (33–281) and 84 days (26–224) in Blantyre. Mean annual malaria incidence was 2·5 versus 2·1 in Kenya (relative risk 1·16, 95% Cl 0·98–1·37), and 2·2 versus 2·8 in Malawi (0·77, 0·63–0·94). 4·3% versus 12·8%, and 5·4% versus 20·1%, of patients were withdrawn for treatment failure in Kenya and Malawi, respectively. In Kenya haemoglobin concentration of 50 g/L or less caused exit in 6·9% of chlorproguanil-dapsone patients and 1·5% of sulfadoxine-pyrimethamine patients, but most anaemia occurred before re-treatment. In Malawi only one patient exited because of anaemia. Despite the rapid elimination of chlorproguanil-dapsone, children treated with this drug did not have a higher incidence of malaria episodes than those treated with sulfadoxine-pyrimethamine. Treatment failure was more common with sulfadoxine-pyrimethamine. Cause of anaemia in Kenya was probably not adverse reaction to chlorproguanil-dapsone, but this observation requires further study.