Does artesunate prolong the electrocardiograph QT interval in patients with severe malaria?

Assessment of the proarrhythmic effects of repurposed antimalarials for COVID-19 treatment using a comprehensive in vitro proarrhythmia assay (CiPA)

Due to the outbreak of the SARS-CoV-2 virus, drug repurposing and Emergency Use Authorization have been proposed to treat the coronavirus disease 2019 (COVID-19) during the pandemic. While the efficiency of the drugs has been discussed, it was identified that certain compounds, such as chloroquine and hydroxychloroquine, cause QT interval prolongation and potential cardiotoxic effects. Drug-induced cardiotoxicity and QT prolongation may lead to life-threatening arrhythmias such as torsades de pointes (TdP), a potentially fatal arrhythmic symptom. Here, we evaluated the risk of repurposed pyronaridine or artesunate-mediated cardiac arrhythmias alone and in combination for COVID-19 treatment through in vitro and in silico investigations using the Comprehensive in vitro Proarrhythmia Assay (CiPA) initiative. The potential effects of each drug or in combinations on cardiac action potential (AP) and ion channels were explored using human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) and Chinese hamster ovary (CHO) cells transiently expressing cardiac ion channels (Nav1.5, Cav1.2, and hERG). We also performed in silico computer simulation using the optimized O'Hara-Rudy human ventricular myocyte model (ORd model) to classify TdP risk. Artesunate and dihydroartemisinin (DHA), the active metabolite of artesunate, are classified as a low risk of inducing TdP based on the torsade metric score (TMS). Moreover, artesunate does not significantly affect the cardiac APs of hiPSC-CMs even at concentrations up to 100 times the maximum serum concentration (Cmax). DHA modestly prolonged at APD90 (10.16%) at 100 times the Cmax. When considering Cmax, pyronaridine, and the combination of both drugs (pyronaridine and artesunate) are classified as having an intermediate risk of inducing TdP. However, when considering the unbound concentration (the free fraction not bound to carrier proteins or other tissues inducing pharmacological activity), both drugs are classified as having a low risk of inducing TdP. In summary, pyronaridine, artesunate, and a combination of both drugs have been confirmed to pose a low proarrhythmogenic risk at therapeutic and supratherapeutic (up to 4 times) free Cmax. Additionally, the CiPA initiative may be suitable for regulatory use and provide novel insights for evaluating drug-induced cardiotoxicity.

Usher syndrome IIIA: a review of the disorder and preclinical research advances in therapeutic approaches

Usher syndrome (USH) is an autosomal recessive disorder characterized by sensorineural hearing loss, progressive pigmentary retinopathy, and vestibular dysfunction. The degree and onset of hearing loss vary among subtypes I, II, and III, while blindness often occurs in the second to fourth decades of life. Usher type III (USH3), characterized by postlingual progressive sensorineural hearing loss, varying levels of vestibular dysfunction, and varying degrees of visual impairment, typically manifests in the first to second decades of life. While USH3 is rare, it is highly prevalent in certain populations. RP61, USH3, and USH3A symbolize the same disorder, with the latter symbol used more frequently in recent literature. This review focuses on the clinical features, epidemiology, molecular genetics, treatment, and research advances for sensory deficits in USH3A.

The cardiovascular effects of amodiaquine and structurally related antimalarials: An individual patient data meta-analysis

BACKGROUND

Amodiaquine is a 4-aminoquinoline antimalarial similar to chloroquine that is used extensively for the treatment and prevention of malaria. Data on the cardiovascular effects of amodiaquine are scarce, although transient effects on cardiac electrophysiology (electrocardiographic QT interval prolongation and sinus bradycardia) have been observed. We conducted an individual patient data meta-analysis to characterise the cardiovascular effects of amodiaquine and thereby support development of risk minimisation measures to improve the safety of this important antimalarial.

METHODS AND FINDINGS

Studies of amodiaquine for the treatment or prevention of malaria were identified from a systematic review. Heart rates and QT intervals with study-specific heart rate correction (QTcS) were compared within studies and individual patient data pooled for multivariable linear mixed effects regression. The meta-analysis included 2,681 patients from 4 randomised controlled trials evaluating artemisinin-based combination therapies (ACTs) containing amodiaquine (n = 725), lumefantrine (n = 499), piperaquine (n = 716), and pyronaridine (n = 566), as well as monotherapy with chloroquine (n = 175) for uncomplicated malaria. Amodiaquine prolonged QTcS (mean = 16.9 ms, 95% CI: 15.0 to 18.8) less than chloroquine (21.9 ms, 18.3 to 25.6, p = 0.0069) and piperaquine (19.2 ms, 15.8 to 20.5, p = 0.0495), but more than lumefantrine (5.6 ms, 2.9 to 8.2, p < 0.001) and pyronaridine (-1.2 ms, -3.6 to +1.3, p < 0.001). In individuals aged ≥12 years, amodiaquine reduced heart rate (mean reduction = 15.2 beats per minute [bpm], 95% CI: 13.4 to 17.0) more than piperaquine (10.5 bpm, 7.7 to 13.3, p = 0.0013), lumefantrine (9.3 bpm, 6.4 to 12.2, p < 0.001), pyronaridine (6.6 bpm, 4.0 to 9.3, p < 0.001), and chloroquine (5.9 bpm, 3.2 to 8.5, p < 0.001) and was associated with a higher risk of potentially symptomatic sinus bradycardia (≤50 bpm) than lumefantrine (risk difference: 14.8%, 95% CI: 5.4 to 24.3, p = 0.0021) and chloroquine (risk difference: 8.0%, 95% CI: 4.0 to 12.0, p < 0.001). The effect of amodiaquine on the heart rate of children aged <12 years compared with other antimalarials was not clinically significant. Study limitations include the unavailability of individual patient-level adverse event data for most included participants, but no serious complications were documented.

CONCLUSIONS

While caution is advised in the use of amodiaquine in patients aged ≥12 years with concomitant use of heart rate-reducing medications, serious cardiac conduction disorders, or risk factors for torsade de pointes, there have been no serious cardiovascular events reported after amodiaquine in widespread use over 7 decades. Amodiaquine and structurally related antimalarials in the World Health Organization (WHO)-recommended dose regimens alone or in ACTs are safe for the treatment and prevention of malaria.

Development and Validation of an In Silico Decision Tool To Guide Optimization of Intravenous Artesunate Dosing Regimens for Severe Falciparum Malaria Patients

Most deaths from severe falciparum malaria occur within 24 h of presentation to a hospital. Intravenous (i.v.) artesunate is the first-line treatment for severe falciparum malaria, but its efficacy may be compromised by delayed parasitological responses. In patients with severe malaria, the life-saving benefit of the artemisinin derivatives is their ability to clear circulating parasites rapidly, before they can sequester and obstruct the microcirculation. To evaluate the dosing of i.v. artesunate for the treatment of artemisinin-sensitive and reduced ring stage sensitivity to artemisinin severe falciparum malaria infections, Bayesian pharmacokinetic-pharmacodynamic modeling of data from 94 patients with severe malaria (80 children from Africa and 14 adults from Southeast Asia) was performed. Assuming that delayed parasite clearance reflects a loss of ring stage sensitivity to artemisinin derivatives, the median (95% credible interval) percentage of patients clearing ≥99% of parasites within 24 h (PC24≥99%) for standard (2.4 mg/kg body weight i.v. artesunate at 0 and 12 h) and simplified (4 mg/kg i.v. artesunate at 0 h) regimens was 65% (52.5% to 74.5%) versus 44% (25% to 61.5%) for adults, 62% (51.5% to 74.5%) versus 39% (20.5% to 58.5%) for larger children (≥20 kg), and 60% (48.5% to 70%) versus 36% (20% to 53.5%) for smaller children (<20 kg). The upper limit of the credible intervals for all regimens was below a PC24≥99% of 80%, a threshold achieved on average in clinical studies of severe falciparum malaria infections. In severe falciparum malaria caused by parasites with reduced ring stage susceptibility to artemisinin, parasite clearance is predicted to be slower with both the currently recommended and proposed simplified i.v. artesunate dosing regimens.

Longitudinal study based on a safety registry for malaria patients treated with artenimol-piperaquine in six European countries

Background

European travellers to endemic countries are at risk of malaria and may be affected by a different range of co-morbidities than natives of endemic regions. The safety profile, especially cardiac issues, of artenimol (previously dihydroartemisinin)–piperaquine (APQ) Eurartesim^® during treatment of uncomplicated imported falciparum malaria is not adequately described due to the lack of longitudinal studies in this population. The present study was conducted to partially fill this gap.

Methods

Participants were recruited through Health Care Provider’s safety registry in 15 centres across 6 European countries in the period 2013–2016. Adverse events (AE) were collected, with a special focus on cardiovascular safety by including electrocardiogram QT intervals evaluated after correction with either Bazett’s (QTcB) or Fridericia’s (QTcF) methods, at baseline and after treatment. QTcB and/or QTcF prolongation were defined by a value > 450 ms for males and children and > 470 ms for females.

Results

Among 294 participants, 30.3% were women, 13.7% of Caucasian origin, 13.5% were current smoker, 13.6% current alcohol consumer and 42.2% declared at least one illness history. The mean (SD) age and body mass index were 39.8 years old (13.2) and 25.9 kg/m² (4.7). Among them, 75 reported a total of 129 AE (27 serious), 46 being suspected to be related to APQ (11 serious) and mostly labelled as due to haematological, gastrointestinal, or infection. Women and Non-African participants had significantly (p < 0.05) more AEs. Among AEs, 21 were due to cardiotoxicity (7.1%), mostly QT prolongation, while 6 were due to neurotoxicity (2.0%), mostly dizziness. Using QTcF correction, QT prolongation was observed in 17/143 participants (11.9%), only 2 of them reporting QTcF > 500 ms (milliseconds) but no clinical symptoms. Using QTcB correction increases of > 60 ms were present in 9 participants (6.3%). A trend towards increased prolongation was observed in those over 65 years of age but only a few subjects were in this group. No new safety signal was reported. The overall efficacy rate was 255/257 (99.2%).

Conclusions

APQ appears as an effective and well-tolerated drug for treatment of malaria in patients recruited in European countries. AEs and QT prolongation were in the range of those obtained in larger cohorts from endemic countries.

Trial registration This study has been registered in EU Post-Authorization Studies Register as EUPAS6942

Supplementary Information

The online version contains supplementary material available at 10.1186/s12936-021-03750-x.

Cardiac Arrhythmia in a Patient with Sickle Cell Anemia and Falciparum Malaria Treated with Intravenous Artesunate

Treatment of severe malaria with artemisinin derivatives in patients with comorbid conditions such as sickle cell anemia must be considered with precaution. We report here a case of possibly undocumented ventricular arrhythmia in a sickle cell anemia patient diagnosed with Plasmodium falciparum malaria and treated with intravenous artesunate. The patient suffered from wide complex tachycardia after treatment with artesunate 170 mg (2.4 mg/kg) i.v. bolus, tachycardia was managed with amiodarone (150 mg i.v. for 10 minutes). Electrocardiographic abnormalities, including QT prolongation, are common in patients with sickle cell anemia. The mortality rate in sickle cell anemia patients due to cardiovascular and pulmonary complications remains high. The probability of precipitation of ventricular arrhythmias may increase in patients with sickle cell anemia, diagnosed with malaria and treated with artemisinin derivatives.

Unconventional secretory pathway activation restores hair cell mechanotransduction in an USH3A model

The pathogenic variant c.144T>G (p.N48K) in the clarin1 gene (CLRN1) results in progressive loss of vision and hearing in Usher syndrome IIIA (USH3A) patients. CLRN1 is predicted to be an essential protein in hair bundles, the mechanosensory structure of hair cells critical for hearing and balance. When expressed in animal models, CLRN1 localizes to the hair bundle, whereas glycosylation-deficient CLRN1^N48K aggregates in the endoplasmic reticulum, with only a fraction reaching the bundle. We hypothesized that the small amount of CLRN1^N48K that reaches the hair bundle does so via an unconventional secretory pathway and that activation of this pathway could be therapeutic. Using genetic and pharmacological approaches, we find that clarin1 knockout (clrn1 ^KO/KO ) zebrafish that express the CLRN1 ^c.144T>G pathogenic variant display progressive hair cell dysfunction, and that CLRN1^N48K is trafficked to the hair bundle via the GRASP55 cargo-dependent unconventional secretory pathway (GCUSP). On expression of GRASP55 mRNA, or on exposure to the drug artemisinin (which activates GCUSP), the localization of CLRN1^N48K to the hair bundles was enhanced. Artemisinin treatment also effectively restored hair cell mechanotransduction and attenuated progressive hair cell dysfunction in clrn1 ^KO/KO larvae that express CLRN1 ^c.144T>G , highlighting the potential of artemisinin to prevent sensory loss in CLRN1 ^c.144T>G patients.

Delayed-onset hemolytic anemia in patients with travel-associated severe malaria treated with artesunate, France, 2011-2013

Artesunate is the most effective treatment for severe malaria. However, delayed-onset hemolytic anemia has been observed in ≈20% of travelers who receive artesunate, ≈60% of whom require transfusion. This finding could discourage physicians from using artesunate. We prospectively evaluated a cohort of 123 patients in France who had severe imported malaria that was treated with artesunate; our evaluation focused on outcome, adverse events, and postartesunate delayed-onset hemolysis (PADH). Of the 123 patients, 6 (5%) died. Overall, 97 adverse events occurred. Among the 78 patients who received follow-up for >8 days after treatment initiation, 76 (97%) had anemia, and 21 (27%) of the 78 cases were recorded as PADH. The median drop in hemoglobin levels was 1.3 g/dL; 15% of patients with PADH had hemoglobin levels of <7 g/dL, and 1 required transfusion. Despite the high incidence of PADH, the resulting anemia remained mild in 85% of cases. This reassuring result confirms the safety and therapeutic benefit of artesunate.

Hematological and biochemical effects of sub-chronic artesunate exposure in rats

Artesunate is a potent and rapidly acting blood schizontocide used to treat chloroquine resistant malaria. Artesunate has been reported to cause embryo, reduced reproductive capacity, hepatotoxicity, neurotoxicity and hematological abnormalities. Previously toxicity studies on artesunate have been done in 2–10 mg/kg dose range mostly for 7 days, scientific studies on sub-chronic exposure of artesunate is not been reported so for. The present study evaluates sub-chronic safety profile of artesunate on 45 days oral administration at 2, 4 and 8 mg/kg/day. Authentication of artesunate has been done by color test, pH, melting point, loss on drying, UV_max, TLC and HPLC study. Artesunate has non-significant effect on liver and kidney weight. Serum glutamate oxaloacetate transaminase (SGOT), serum glutamate pyruvate transaminase (SGPT), serum alkaline phosphate (ALP), cholesterol (TC), triglyceride (TG), total protein, albumin, bilirubin, creatinine, urea and glucose content were estimated after 45 days treatment along with hematological screening. Artesunate treatment for 45 days significantly increased (p < 0.05–0.001) SGOT, SGPT, ALP, TC, TG, total bilirubin, glucose level at 8 mg/kg/day dose. It has non-significant effect on serum total protein, albumin, creatinine and urea. Hemoglobin, total RBC, platelet, lymphocytes, basophil, mean cell volume and mean corpuscular hemoglobin concentration have not changed but total WBC, neutrophil, eosinophil, packed cell volume and mean cell hemoglobin were increased significantly (p < 0.01) at 8 mg/kg/day dose. Artesunate treatment at 4 and 8 mg/kg/day showed sinusoidal dilation, cytoplasmic vaculation, focal necrosis, sinusoidal congestion and extensive inflammatory changes, whereas kidney was free of any deleterious effect.

Conclusion

Sub-chronic exposure of artesunate at 8 mg/kg/day dose for 45 days period cause hepatic damage along with hematological abnormalities signifying safety concern.

Population pharmacokinetics of intravenous artesunate: a pooled analysis of individual data from patients with severe malaria

There are ~660,000 deaths from severe malaria each year. Intravenous artesunate (i.v. ARS) is the first-line treatment in adults and children. To optimize the dosing regimen of i.v. ARS, the largest pooled population pharmacokinetic study to date of the active metabolite dihydroartemisinin (DHA) was performed. The pooled dataset consisted of 71 adults and 195 children with severe malaria, with a mixture of sparse and rich sampling within the first 12 h after drug administration. A one-compartment model described the population pharmacokinetics of DHA adequately. Body weight had the greatest impact on DHA pharmacokinetics, resulting in lower DHA exposure for smaller children (6–10 kg) than adults. Post hoc estimates of DHA exposure were not significantly associated with parasitological outcomes. Comparable DHA exposure in smaller children and adults after i.v. ARS was achieved under a dose modification for intramuscular ARS proposed in a separate analysis of children.

General Pharmacology of Artesunate, a Commonly used Antimalarial Drug:Effects on Central Nervous, Cardiovascular, and Respiratory System

Artesunate, a semi-synthetic derivative of artemisinin, is used primarily as a treatment for malaria. Its effects on the central nervous system, general behavior, and cardiovascular, respiratory, and other organ systems were studied using mice, rats, guinea pigs, and dogs. Artesunate was administered orally to mice at doses of 125, 250, and 500 mg/kg and to rats and guinea pigs at 100, 200, and 400 mg/kg. In dogs, test drugs were administered orally in gelatin capsules at doses of 50, 100, and 150 mg/kg. Artesunate induced insignificant changes in general pharmacological studies, including general behavior, motor coordination, body temperature, analgesia, convulsion modulation, blood pressure, heart rate (HR) , and electrocardiogram (ECG) in dogs in vivo; respiration in guinea pigs; and gut motility or direct effects on isolated guinea pig ileum, contractile responses, and renal function. On the other hand, artesunate decreased the HR and coronary flow rate (CFR) in the rat in vitro; however, the extent of the changes was small and they were not confirmed in in vivo studies in the dog. Artesunate increased hexobarbital-induced sleeping time in a dose-related manner. Artesunate induced dose-related decreases in the volume of gastric secretions and the total acidity of gastric contents, and induced increases in pH at a dose of 400 mg/kg. However, all of these changes were observed at doses much greater than clinical therapeutic doses (2.4 mg/kg in humans, when used as an anti-malarial) . Thus, it can be concluded that artesunate is safe at clinical therapeutic doses.

Intravenous artesunate versus intravenous quinine in the treatment of severe falciparum malaria: a retrospective evaluation from a UK centre

INTRODUCTION

Despite evidence from developing world trials that intravenous (IV) artesunate (AS) is superior to IV quinine (Q) in severe falciparum malaria (FM), IV AS remains unlicensed in the UK with national guidelines listing it as an acceptable alternative to IV Q as the drug of choice. We retrospectively evaluate the safety and effectiveness of IV AS in returning travellers with severe FM.

METHODS

We identified adults admitted to the Infectious Diseases unit with severe FM and treated with IV Q (1991-2009) or IV AS (2009-2011). Outcomes included adverse events, mortality, length of stay, admission to intensive care and, where data were available, parasite/fever clearance time and hypoglycaemic events.

RESULTS

Of 167 patients, 24 received IV AS and 143 IV Q. There was one potential AS-associated adverse event, a case of late onset haemolysis. Median length of stay (LOS) was significantly shorter for AS (3·5 versus 5 days, P = 0·017), even after adjusting for African ethnicity (for LOS ≥3 days, mhor = 0·33, P = 0·027; crude OR = 0·29, P = 0·013). In the AS group, there were no fatalities (versus five in Q group, NS) and fewer intensive care unit (ICU) admissions (NS). Median parasite clearance was significantly faster in AS (65 versus 85 hours in Q, P = 0·0045) with no hypoglycaemic episodes (versus five in Q).

DISCUSSION

We found IV AS to be safe and effective, with shorter LOS, faster parasite and fever clearance, no fatalities or hypoglycaemic events, and fewer ICU admissions versus IV Q. This corroborates both developing world trials and smaller European case series (although these lacked comparison groups). As well as obvious benefits for patients, there are potential resource savings. A case of late-onset haemolysis may represent an adverse event, particularly as it has been documented elsewhere, warranting further investigation. Nonetheless, our experience suggests IV AS should be first-line for treating severe FM in the UK.

pH-responsive artemisinin derivatives and lipid nanoparticle formulations inhibit growth of breast cancer cells in vitro and induce down-regulation of HER family members

Artemisinin (ART) dimers show potent anti-proliferative activities against breast cancer cells. To facilitate their clinical development, novel pH-responsive artemisinin dimers were synthesized for liposomal nanoparticle formulations. A new ART dimer was designed to become increasingly water-soluble as pH declines. The new artemisinin dimer piperazine derivatives (ADPs) remained tightly associated with liposomal nanoparticles (NPs) at neutral pH but were efficiently released at acidic pH's that are known to exist within solid tumors and organelles such as endosomes and lysosomes. ADPs incorporated into nanoparticles down regulated the anti-apoptotic protein, survivin, and cyclin D1 when incubated at low concentrations with breast cancer cell lines. We demonstrate for the first time, for any ART derivative, that ADP NPs can down regulate the oncogenic protein HER2, and its counterpart, HER3 in a HER2+ cell line. We also show that the wild type epidermal growth factor receptor (EGFR or HER1) declines in a triple negative breast cancer (TNBC) cell line in response to ADP NPs. The declines in these proteins are achieved at concentrations of NP109 at or below 1 µM. Furthermore, the new artemisinin derivatives showed improved cell-proliferation inhibition effects compared to known dimer 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.

Antiparasitic therapy

Parasitic diseases affect more than 2 billion people globally and cause substantial morbidity and mortality, particularly among the world's poorest people. This overview focuses on the treatment of the major protozoan and helminth infections in humans. Recent developments in antiparasitic therapy include the expansion of artemisinin-based therapies for malaria, new drugs for soil-transmitted helminths and intestinal protozoa, expansion of the indications for antiparasitic drug treatment in patients with Chagas disease, and the use of combination therapy for leishmaniasis and human African trypanosomiasis.

Fatal Myocarditis in Course of Plasmodium falciparum Infection: Case Report and Review of Cardiac Complications in Malaria

We describe a fatal case of imported malaria where the sole finding revealed at the postmortem evaluation was an acute lymphocytic myocarditis with myocardiolysis. This case recalls the potential importance of myocardial injury in the prognosis of malaria and prompts a reevaluation of current perspectives on the pathogenesis of severe falciparum infection. In the light of this, we have reviewed the cases of cardiac complications in malaria published to date.

CMCH and MORU: a Highly Successful Collaboration

Chittagong Medical College and Hospital (CMCH) in Chittagong, Bangladesh, and Mahidol-Oxford Tropical Medicine Research Unit (MORU) of Bangkok, Thailand, are partners in a highly successful and productive research collaboration that is now heading into its tenth year. It produced arguably one of the most important clinical trials in tropical medicine this decade, the South-East-Asia-Quinine-Artesuante-Malaria-Trial (SEAQUAMAT) study, and has continued to evolve and grow ever since. The collaboration has successfully completed a number of significant clinical studies which have given important new insights into the management and pathogenesis of malaria and, to date, generated 14 peer-reviewed international journal publications. With each passing year, the size of the collaboration continues to increase along with the number and complexity of research studies undertaken. It has also helped to provide valuable postgraduate training to develop clinical services and increase capacity for high quality research in Bangladesh. The partners have complementary knowledge, skills and expertise and share common goals and it is hoped that this will remain a highly successful collaboration long into the future.

Artemisinin Antimalarials: Preserving the "Magic Bullet"

The artemisinins are the most effective antimalarial drugs known. They possess a remarkably wide therapeutic index. These agents have been used in traditional Chinese herbal medicine for more than 2,000 years but were not subjected to scientific scrutiny until the 1970s. The first formal clinical trials of the artemisinins, and the development of methods for their industrial scale production, followed rapidly. A decade later, Chinese scientists shared their findings with the rest of the world; since then, a significant body of international trial evidence has confirmed these drugs to be far superior to any available alternatives. In particular, they have the ability to rapidly kill a broad range of asexual parasite stages at safe concentrations that are consistently achievable via standard dosing regimens. As their half-life is very short, there was also thought to be a low risk of resistance. These discoveries coincided with the appearance and spread of resistance to all the other major classes of antimalarials. As a result, the artemisinins now form an essential element of recommended first-line antimalarial treatment regimens worldwide. To minimize the risk of artemisinin resistance, they are recommended to be used to treat uncomplicated malaria in combination with other antimalarials as artemisinin combination therapies (ACTs). Their rollout has resulted in documented reductions in malaria prevalence in a number of African and Asian countries. Unfortunately, there are already worrisome early signs of artemisinin resistance appearing in western Cambodia. If this resistance were to spread, it would be disastrous for malaria control efforts worldwide. The enormous challenge for the international community is how to avert this catastrophe and preserve the effectiveness of this antimalarial “magic bullet”. Drug Dev Res 71: 12–19, 2010. © 2009 Wiley-Liss, Inc.