Atovaquone-proguanil for treating uncomplicated malaria

Antiviral Potential of the Antimicrobial Drug Atovaquone against SARS-CoV-2 and Emerging Variants of Concern

The antimicrobial medication malarone (atovaquone/proguanil) is used as a fixed-dose combination for treating children and adults with uncomplicated malaria or as chemoprophylaxis for preventing malaria in travelers. It is an inexpensive, efficacious, and safe drug frequently prescribed around the world. Following anecdotal evidence from 17 patients in the provinces of Quebec and Ontario, Canada, suggesting that malarone/atovaquone may present some benefits in protecting against COVID-19, we sought to examine its antiviral potential in limiting the replication of SARS-CoV-2 in cellular models of infection. In VeroE6 expressing human TMPRSS2 and human lung Calu-3 epithelial cells, we show that the active compound atovaquone at micromolar concentrations potently inhibits the replication of SARS-CoV-2 and other variants of concern including the alpha, beta, and delta variants. Importantly, atovaquone retained its full antiviral activity in a primary human airway epithelium cell culture model. Mechanistically, we demonstrate that the atovaquone antiviral activity against SARS-CoV-2 is partially dependent on the expression of TMPRSS2 and that the drug can disrupt the interaction of the spike protein with the viral receptor, ACE2. Additionally, spike-mediated membrane fusion was also reduced in the presence of atovaquone. In the United States, two clinical trials of atovaquone administered alone or in combination with azithromycin were initiated in 2020. While we await the results of these trials, our findings in cellular infection models demonstrate that atovaquone is a potent antiviral FDA-approved drug against SARS-CoV-2 and other variants of concern in vitro.

Atovaquone-proguanil for treating uncomplicated Plasmodium falciparum malaria

BACKGROUND

The World Health Organization (WHO) in 2015 stated atovaquone-proguanil can be used in travellers, and is an option in malaria-endemic areas in combination with artesunate, as an alternative treatment where first-line artemisinin-based combination therapy (ACT) is not available or effective. This review is an update of a Cochrane Review undertaken in 2005.

OBJECTIVES

To assess the efficacy and safety of atovaquone-proguanil (alone and in combination with artemisinin drugs) versus other antimalarial drugs for treating uncomplicated Plasmodium falciparum malaria in adults and children.

SEARCH METHODS

The date of the last trial search was 30 January 2020. Search locations for published trials included the Cochrane Infectious Diseases Group Specialized Register, CENTRAL, MEDLINE, Embase, and LILACS. To include recently published and unpublished trials, we also searched ClinicalTrials.gov, the metaRegister of Controlled Trials and the WHO International Clinical Trials Registry Platform Search Portal.

SELECTION CRITERIA

Randomized controlled trials (RCTs) reporting efficacy and safety data for atovaquone-proguanil or atovaquone-proguanil with a partner drug compared with at least one other antimalarial drug for treating uncomplicated Plasmodium falciparum infection.

DATA COLLECTION AND ANALYSIS

For this update, two review authors re-extracted data and assessed certainty of evidence. We meta-analyzed data to calculate risk ratios (RRs) with 95% confidence intervals (CI) for treatment failures between comparisons, and for safety outcomes between and across comparisons. Outcome measures include unadjusted treatment failures and polymerase chain reaction (PCR)-adjusted treatment failures. PCR adjustment differentiates new infection from recrudescent infection.

MAIN RESULTS

Seventeen RCTs met our inclusion criteria providing 4763 adults and children from Africa, South-America, and South-East Asia. Eight trials reported PCR-adjusted data to distinguish between new and recrudescent infection during the follow-up period. In this abstract, we report only the comparisons against the three WHO-recommended antimalarials which were included within these trials. There were two comparisons with artemether-lumefantrine, one trial from 2008 in Ethiopia with 60 participants had two failures with atovaquone-proguanil compared to none with artemether-lumefantrine (PCR-adjusted treatment failures at day 28). A second trial from 2012 in Colombia with 208 participants had one failure in each arm (PCR-adjusted treatment failures at day 42). There was only one comparison with artesunate-amodiaquine from a 2014 trial conducted in Cameroon. There were six failures with atovaquone-proguanil at day 28 and two with artesunate-amodiaquine (PCR-adjusted treatment failures at day 28: 9.4% with atovaquone-proguanil compared to 2.9% with artesunate-amodiaquine; RR 3.19, 95% CI 0.67 to 15.22; 1 RCT, 132 participants; low-certainty evidence), although there was a similar number of PCR-unadjusted treatment failures (9 (14.1%) with atovaquone-proguanil and 8 (11.8%) with artesunate-amodiaquine; RR 1.20, 95% CI 0.49 to 2.91; 1 RCT, 132 participants; low-certainty evidence). There were two comparisons with artesunate-mefloquine from a 2012 trial in Colombia and a 2002 trial in Thailand where there are high levels of multi-resistant malaria. There were similar numbers of PCR-adjusted treatment failures between groups at day 42 (2.7% with atovaquone-proguanil compared to 2.4% with artesunate-mefloquine; RR 1.15, 95% CI 0.57 to 2.34; 2 RCTs, 1168 participants; high-certainty evidence). There were also similar PCR-unadjusted treatment failures between groups (5.3% with atovaquone-proguanil compared to 6.6% with artesunate-mefloquine; RR 0.8, 95% CI 0.5 to 1.3; 1 RCT, 1063 participants; low-certainty evidence). When atovaquone-proguanil was combined with artesunate, there were fewer treatment failures with and without PCR-adjustment at day 28 (PCR-adjusted treatment failures at day 28: 2.16% with atovaquone-proguanil compared to no failures with artesunate-atovaquone-proguanil; RR 5.14, 95% CI 0.61 to 43.52; 2 RCTs, 375 participants, low-certainty evidence) and day 42 (PCR-adjusted treatment failures at day 42: 3.82% with atovaquone-proguanil compared to 2.05% with artesunate-atovaquone-proguanil (RR 1.84, 95% CI 0.95 to 3.56; 2 RCTs, 1258 participants, moderate-certainty evidence). In the 2002 trial in Thailand, there were fewer treatment failures in the artesunate-atovaquone-proguanil group compared to the atovaquone-proguanil group at day 42 with PCR-adjustment. Whilst there were some small differences in which adverse events were more frequent in the atovaquone-proguanil groups compared to comparator drugs, there were no recurrent associations to suggest that atovaquone-proguanil is strongly associated with any specific adverse event.

AUTHORS' CONCLUSIONS

Atovaquone-proguanil was effective against uncomplicated P falciparum malaria, although in some instances treatment failure rates were between 5% and 10%. The addition of artesunate to atovaquone-proguanil may reduce treatment failure rates. Artesunate-atovaquone-proguanil and the development of parasite resistance may represent an area for further research.

Clinical implications of Plasmodium resistance to atovaquone/proguanil: a systematic review and meta-analysis

Background

Atovaquone/proguanil, registered as Malarone^®, is a fixed-dose combination recommended for first-line treatment of uncomplicated Plasmodium falciparum malaria in non-endemic countries and its prevention in travellers. Mutations in the cytochrome bc₁ complex are causally associated with atovaquone resistance.

Methods

This systematic review assesses the clinical efficacy of atovaquone/proguanil treatment of uncomplicated malaria and examines the extent to which codon 268 mutation in cytochrome b influences treatment failure and recrudescence based on published information.

Results

Data suggest that atovaquone/proguanil treatment efficacy is 89%–98% for P. falciparum malaria (from 27 studies including between 18 and 253 patients in each case) and 20%–26% for Plasmodium vivax malaria (from 1 study including 25 patients). The in vitro P. falciparum phenotype of atovaquone resistance is an IC₅₀ value >28 nM. Case report analyses predict that recrudescence in a patient presenting with parasites carrying cytochrome b codon 268 mutation will occur on average at day 29 (95% CI: 22, 35), 19 (95% CI: 7, 30) days longer than if the mutation is absent.

Conclusions

Evidence suggests atovaquone/proguanil treatment for P. falciparum malaria is effective. Late treatment failure is likely to be associated with a codon 268 mutation in cytochrome b, though recent evidence from animal models suggests these mutations may not spread within the population. However, early treatment failure is likely to arise through alternative mechanisms, requiring further investigation.

Current therapies and future possibilities for drug development against liver-stage malaria

Malaria remains a global public health threat, with half of the world's population at risk. Despite numerous efforts in the past decade to develop new antimalarial drugs to surmount increasing resistance to common therapies, challenges remain in the expansion of the current antimalarial arsenal for the elimination of this disease. The requirement of prophylactic and radical cure activities for the next generation of antimalarial drugs demands that new research models be developed to support the investigation of the elusive liver stage of the malaria parasite. In this Review, we revisit current antimalarial therapies and discuss recent advances for in vitro and in vivo malaria research models of the liver stage and their importance in probing parasite biology and the discovery of novel drug candidates.

New insight-guided approaches to detect, cure, prevent and eliminate malaria

New challenges posed by the development of resistance against artemisinin-based combination therapies (ACTs) as well as previous first-line therapies, and the continuing absence of vaccine, have given impetus to research in all areas of malaria control. This review portrays the ongoing progress in several directions of malaria research. The variants of RTS,S and apical membrane antigen 1 (AMA1) are being developed and test adapted as multicomponent and multistage malaria control vaccines, while many other vaccine candidates and methodologies to produce antigens are under experimentation. To track and prevent the spread of artemisinin resistance from Southeast Asia to other parts of the world, rolling circle-enhanced enzyme activity detection (REEAD), a time- and cost-effective malaria diagnosis in field conditions, and a DNA marker associated with artemisinin resistance have become available. Novel mosquito repellents and mosquito trapping and killing techniques much more effective than the prevalent ones are undergoing field testing. Mosquito lines stably infected with their symbiotic wild-type or genetically engineered bacteria that kill sympatric malaria parasites are being constructed and field tested for stopping malaria transmission. A complementary approach being pursued is the addition of ivermectin-like drug molecules to ACTs to cure malaria and kill mosquitoes. Experiments are in progress to eradicate malaria mosquito by making it genetically male sterile. High-throughput screening procedures are being developed and used to discover molecules that possess long in vivo half life and are active against liver and blood stages for the fast cure of malaria symptoms caused by simple or relapsing and drug-sensitive and drug-resistant types of varied malaria parasites, can stop gametocytogenesis and sporogony and could be given in one dose. Target-based antimalarial drug designing has begun. Some of the putative next-generation antimalarials that possess in their scaffold structure several of the desired properties of malaria cure and control are exemplified by OZ439, NITD609, ELQ300 and tafenoquine that are already undergoing clinical trials, and decoquinate, usnic acid, torin-2, ferroquine, WEHI-916, MMV396749 and benzothiophene-type N-myristoyltransferase (NMT) inhibitors, which are candidates for future clinical usage. Among these, NITD609, ELQ300, decoquinate, usnic acid, torin-2 and NMT inhibitors not only cure simple malaria and are prophylactic against simple malaria, but they also cure relapsing malaria.

Atovaquone-proguanil in the treatment of imported uncomplicated Plasmodium falciparum malaria: a prospective observational study of 553 cases

Background

Each year, thousands of cases of uncomplicated malaria are imported into Europe by travellers. Atovaquone-proguanil (AP) has been one of the first-line regimens used in France for uncomplicated malaria for almost ten years. While AP’s efficacy and tolerance were evaluated in several trials, its use in “real life” conditions has never been described. This study aimed to describe outcome and tolerance after AP treatment in a large cohort of travellers returning from endemic areas.

Methods

Between September 2002 and January 2007, uncomplicated malaria treated in nine French travel clinics with AP were followed for 30 days after AP initiation. Clinical and biological data were collected at admission and during the follow-up.

Results

A total of 553 patients were included. Eighty-eight percent of them were born in Africa, and 61.8% were infected in West Africa, whereas 0.5% were infected in Asia. Migrants visiting friends and relatives (VFR) constituted 77.9% of the patients, the remainder (32.1%) were backpackers. Three-hundred and sixty-four patients (66%) fulfilled follow-up at day 7 and 265 (48%) completed the study at day 30. Three patients had treatment failure. One-hundred and seventy-seven adverse drug reactions (ADR) were reported during the follow-up; 115 (77%) of them were digestive ADR. Backpackers were more likely to experiment digestive ADR compared to VFR (OR = 3.8; CI 95% [1.8-8.2]). Twenty patients had to be switched to another regimen due to ADR.

Conclusion

This study seems to be the largest in terms of number of imported uncomplicated malaria cases treated by AP. The high rate of reported digestive ADR is striking and should be taken into account in the follow-up of patients since it could affect their adherence to the treatment. Beside AP, artemisinin combination therapy (ACT) is now recommended as first-line regimen. A comparison of AP and ACT, in terms of efficacy and tolerance, would be useful.

Antimalarial pharmacology and therapeutics of atovaquone

Atovaquone is used as a fixed-dose combination with proguanil (Malarone) for treating children and adults with uncomplicated malaria or as chemoprophylaxis for preventing malaria in travellers. Indeed, in the USA, between 2009 and 2011, Malarone prescriptions accounted for 70% of all antimalarial pre-travel prescriptions. In 2013 the patent for Malarone will expire, potentially resulting in a wave of low-cost generics. Furthermore, the malaria scientific community has a number of antimalarial quinolones with a related pharmacophore to atovaquone at various stages of pre-clinical development. With this in mind, it is timely here to review the current knowledge of atovaquone, with the purpose of aiding the decision making of clinicians and drug developers involved in the future use of atovaquone generics or atovaquone derivatives.

Advances in the treatment of malaria

Malaria still claims a heavy toll of deaths and disabilities even at the beginning of the third millennium. The inappropriate sequential use of drug monotherapy in the past has facilitated the spread of drug-resistant P. falciparum, and to a lesser extend P. vivax, strains in most of the malaria endemic areas, rendering most anti-malarial ineffective. In the last decade, a new combination strategy based on artemisinin derivatives (ACT) has become the standard of treatment for most P. falciparum malaria infections. This strategy could prevent the selection of resistant strains by rapidly decreasing the parasitic burden (by the artemisinin derivative, mostly artesunate) and exposing the residual parasite to effective concentrations of the partner drug. The widespread use of this strategy is somehow constrained by cost and by the inappropriate use of artemisinin, with possible impact on resistance, as already sporadically observed in South East Asia. Parenteral artesunate has now become the standard of care for severe malaria, even if quinine still retains its value in case artesunate is not immediately available. The appropriateness of pre-referral use of suppository artesunate is under close monitoring, while waiting for an effective anti-malarial vaccine to be made available.

Concordance of sleep and pain outcomes of diverse interventions: an umbrella review

BACKGROUND/OBJECTIVE

Pain influences sleep and vice versa. We performed an umbrella review of meta-analyses on treatments for diverse conditions in order to examine whether diverse medical treatments for different conditions have similar or divergent effects on pain and sleep.

METHODS

We searched published systematic reviews with meta-analyses in the Cochrane Database of Systematic Reviews until October 20, 2011. We identified randomized trials (or meta-analyses thereof, when >1 trial was available) where both pain and sleep outcomes were examined. Pain outcomes were categorized as headache, musculoskeletal, abdominal, pelvic, generic or other pain. Sleep outcomes included insomnia, sleep disruption, and sleep disturbance. We estimated odds ratios for all outcomes and evaluated the concordance in the direction of effects between sleep and various types of pain and the correlation of treatment effects between sleep and pain outcomes.

RESULTS

151 comparisons with 385 different trials met our eligibility criteria. 96 comparisons had concordant direction of effects between each pain outcome and sleep, while in 55 the effect estimates were in opposite directions (P<0.0001). In the 20 comparisons with largest amount of evidence, the experimental drug always had worse sleep outcomes and tended to have worse pain outcomes in 17/20 cases. For headache and musculoskeletal pain, 69 comparisons showed concordant direction of effects with sleep outcomes and 36 showed discordant direction (P<0.0001). For the other 4 pain types there were overall 27 vs. 19 pairs with concordant vs. discordant direction of effects (P = 0.095). There was a weak correlation of the treatment effect sizes for sleep vs. headache/musculoskeletal pain (r = 0.17, P = 0.092).

CONCLUSIONS

Medical interventions tend to have effects in the same direction for pain and sleep outcomes, but exceptions occur. Concordance is primarily seen for sleep and headache or musculoskeletal pain where many drugs may both disturb sleep and cause pain.

Malaria prevention in travelers

A common approach to malaria prevention is to follow the "A, B, C, D" rule: Awareness of risk, Bite avoidance, Compliance with chemoprophylaxis, and prompt Diagnosis in case of fever. The risk of acquiring malaria depends on the length and intensity of exposure; the risk of developing severe disease is primarily determined by the health status of the traveler. These parameters need to be assessed before recommending chemoprophylaxis and/or stand-by emergency treatment. This review discusses the different strategies and drug options available for the prevention of malaria during and post travel.

Therapy of uncomplicated falciparum malaria in Europe: MALTHER - a prospective observational multicentre study

BACKGROUND

Malaria continues to be amongst the most frequent infectious diseases imported to Europe. Whilst European treatment guidelines are based on data from studies carried out in endemic areas, there is a paucity of original prospective treatment data. The objective was to summarize data on treatments to harmonize and optimize treatment for uncomplicated malaria in Europe.

METHODS

A prospective observational multicentre study was conducted, assessing tolerance and efficacy of treatment regimens for imported uncomplicated falciparum malaria in adults amongst European centres of tropical and travel medicine.

RESULTS

Between December 2003 and 2009, 504 patients were included in 16 centres from five European countries. Eighteen treatment regimens were reported, the top three being atovaquone-proguanil, mefloquine, and artemether-lumefantrine. Treatments significantly differed with respect to the occurrence of treatment changes (p = 0.005) and adverse events (p = 0.001), parasite and fever clearance times (p < 0.001), and hospitalization rates (p = 0.0066) and durations (p = 0.001). Four recrudescences and two progressions to severe disease were observed. Compared to other regimens, quinine alone was associated with more frequent switches to second line treatment, more adverse events and longer inpatient stays. Parasite and fever clearance times were shortest with artemether-mefloquine combination treatment. Vomiting was the most frequent cause of treatment change, occurring in 5.5% of all patients but 9% of the atovaquone-proguanil group.

CONCLUSIONS

This study highlights the heterogeneity of standards of care within Europe. A consensus discussion at European level is desirable to foster a standardized management of imported falciparum malaria.

Peroxisome proliferator activating receptor (PPAR) in cerebral malaria (CM): a novel target for an additional therapy

Cerebral malaria (CM) is a global life-threatening complication of Plasmodium infection and represents a major cause of morbidity and mortality among severe forms of malaria. Despite developing knowledge in understanding mechanisms of pathogenesis, the current anti-malarial agents are not sufficient due to drug resistance and various adverse effects. Therefore, there is an urgent need for the novel target and additional therapy. Recently, peroxisome proliferator-activated receptor (PPAR) a nuclear receptors (NR) and agonists of its isoforms (PPARγ, PPARα and PPARβ/δ) have been demonstrated to exhibit anti-inflammatory and immunomodulatory properties, which are driven to a new approach of research on inflammatory diseases. Although many studies on PPARs have confirmed their diverse biological role, there is a lack of knowledge of its therapeutic use in CM. The major objective of this review is to explore the possible experimental studies to link these two areas of research. We focus on the data describing the beneficial effects of this receptor in inflammation, which is observed as a basic pathology in CM. In conclusion, PPARs could be a novel target in treating inflammatory diseases, and continued work with the available and additional agonists screened from various sources may result in a potential new treatment for CM.

Comparative effectiveness of medical interventions in adults versus children

OBJECTIVE

To estimate the comparative effectiveness of medical interventions in adults versus children.

STUDY DESIGN

We identified from the Cochrane Database of Systematic Reviews (Issue 1, 2007) meta-analyses with data on at least 1 adult and 1 pediatric randomized trial with binary primary efficacy outcome. For each meta-analysis, we calculated the summary odds ratio of the adult trials and the pediatric trials, respectively; the relative odds ratio (ROR) of the adult versus pediatric odds ratios per meta-analysis; and the summary ROR across all meta-analyses. ROR <1 means that the experimental intervention is more unfavorable in children than adults.

RESULTS

Across 128 eligible meta-analyses (1051 adult and 343 pediatric trials), the summary ROR did not show a statistically significant difference between adults and children (0.96; 95% confidence intervals, 0.86 to 1.08). However, in all meta-analyses except for 1, the individual ROR's 95% confidence intervals could not exclude a relative difference in efficacy over 20%. In two-thirds, the relative difference in observed point estimates exceeded 50%. Nine statistically significant discrepancies were identified; 4 of them were also clinically important.

CONCLUSIONS

Treatment effects are on average similar in adults and children, but available evidence leaves large uncertainty about their relative efficacy. Clinically important discrepancies may occur.

Evidence for perinatal and child health care guidelines in crisis settings: can Cochrane help?

BACKGROUND

It is important that healthcare provided in crisis settings is based on the best available research evidence. We reviewed guidelines for child and perinatal health care in crisis situations to determine whether they were based on research evidence, whether Cochrane systematic reviews were available in the clinical areas addressed by these guidelines and whether summaries of these reviews were provided in Evidence Aid.

METHODS

Broad internet searches were undertaken to identify relevant guidelines. Guidelines were appraised using AGREE and the clinical areas that were relevant to perinatal or child health were extracted. We searched The Cochrane Database of Systematic Reviews to identify potentially relevant reviews. For each review we determined how many trials were included, and how many were conducted in resource-limited settings.

RESULTS

Six guidelines met selection criteria. None of the included guidelines were clearly based on research evidence. 198 Cochrane reviews were potentially relevant to the guidelines. These reviews predominantly addressed nutrient supplementation, breastfeeding, malaria, maternal hypertension, premature labour and prevention of HIV transmission. Most reviews included studies from developing settings. However for large portions of the guidelines, particularly health services delivery, there were no relevant reviews. Only 18 (9.1%) reviews have summaries in Evidence Aid.

CONCLUSIONS

We did not identify any evidence-based guidelines for perinatal and child health care in disaster settings. We found many Cochrane reviews that could contribute to the evidence-base supporting future guidelines. However there are important issues to be addressed in terms of the relevance of the available reviews and increasing the number of reviews addressing health care delivery.

In vitro atovaquone/proguanil susceptibility and characterization of the cytochrome b gene of Plasmodium falciparum from different endemic regions of Thailand

BACKGROUND

The emergence of Plasmodium falciparum resistant to most currently used antimalarial drugs is the major problem in malaria control along the Thai-Myanmar and Thai-Cambodia borders. Although artemisinin-based combination therapy has been recommended for the treatment of multidrug-resistant falciparum malaria, these combinations are not available for some people, such as travelers from North America. A fixed-dose combination of atovaquone and proguanil (Malarone) has been proved to be effective for the treatment and prophylaxis of malaria which is already approved by countries in North America and Europe. Determination of the phenotypes and genotypes related to atovaquone/proguanil response in Thai isolates of P. falciparum will be useful for rationale drug use. The main purpose of this study was to explore the in vitro atovaquone/proguanil susceptibility of recently adapted Thai isolates of P. falciparum. Genotypic characterization of the cytb gene of these isolates was also determined since it has been reported that point mutations, particularly codon 268 in the cytochrome b gene (cytb) have been linked to atovaquone/proguanil treatment failure.

METHODS

Eighty three P. falciparum isolates collected during 1998 to 2005 from four different multidrug resistance areas of Thailand were determined for the in vitro atovaquone/proguanil susceptibilities using radioisotopic assay. Mutations in the cytb gene were determined by PCR-RFLP and sequence analysis.

RESULTS

The mean atovaquone and proguanil IC50 was 3.4 nM and 36.5 muM, respectively. All 83 Thai isolates were atovaquone sensitive. None of the 83 isolates contained the mutations at codon 268 of the cytb gene. DNA sequencing of the cytb gene of 20 parasite isolates showed no other mutations.

CONCLUSION

In agreement with a recent efficacy study of atovaquone/proguanil, the present information indicates that atovaquone/proguanil can be one of the drugs of choice for the treatment and prophylaxis of multidrug-resistant falciparum malaria in Thailand.