Effectiveness of BNT162b2 and mRNA-1273 Second Doses and Boosters for Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Infection and SARS-CoV-2-Related Hospitalizations: A Statewide Report From the Minnesota Electronic Health Record Consortium.

Using vaccine data combined with electronic health records, we report that mRNA boosters provide greater protection than a 2-dose regimen against SARS-CoV-2 infection and related hospitalizations. The benefit of a booster was more evident in the elderly and those with comorbidities.

High intensity ultrasound assisted decaffeination process of coffee beans in aqueous medium.

The purpose of this study was to determine the influence of ultrasound intensity, pulse and temperature on extraction of caffeine, from Arabica coffee beans using water as solvent, and ultrasound frequency of 24 kHz. A central composite design was used, using ultrasound intensity (31.5-105 W cm-2), pulse (0.30-1) and extraction temperature of the extraction (30-60 °C) as independent factor. The caffeine recovery and caffeine diffusion coefficient were response variables. The ultrasound intensity and extraction temperature significantly influenced the caffeine recovery rate and the diffusion coefficient of caffeine. Activation energy of 48.95 kJ mol-1 for the caffeine diffusion coefficient in ultrasound assisted extraction was observed. The best results were obtained at 68.25-105 W cm-2 ultrasound intensity and 60 °C temperature, corresponding to caffeine recovery of 58.4-69.4% and diffusion coefficient of 8.92-10.57 × 10-11 m2 s-1. The pulse effect was not significant in the range of the studied variables.

Scalable preparation and differential pharmacologic and toxicologic profiles of primaquine enantiomers.

Hematotoxicity in individuals genetically deficient in glucose-6-phosphate dehydrogenase (G6PD) activity is the major limitation of primaquine (PQ), the only antimalarial drug in clinical use for treatment of relapsing Plasmodium vivax malaria. PQ is currently clinically used in its racemic form. A scalable procedure was developed to resolve racemic PQ, thus providing pure enantiomers for the first time for detailed preclinical evaluation and potentially for clinical use. These enantiomers were compared for antiparasitic activity using several mouse models and also for general and hematological toxicities in mice and dogs. (+)-(S)-PQ showed better suppressive and causal prophylactic activity than (-)-(R)-PQ in mice infected with Plasmodium berghei. Similarly, (+)-(S)-PQ was a more potent suppressive agent than (-)-(R)-PQ in a mouse model of Pneumocystis carinii pneumonia. However, at higher doses, (+)-(S)-PQ also showed more systemic toxicity for mice. In beagle dogs, (+)-(S)-PQ caused more methemoglobinemia and was toxic at 5 mg/kg of body weight/day given orally for 3 days, while (-)-(R)-PQ was well tolerated. In a novel mouse model of hemolytic anemia associated with human G6PD deficiency, it was also demonstrated that (-)-(R)-PQ was less hemolytic than (+)-(S)-PQ for the G6PD-deficient human red cells engrafted in the NOD-SCID mice. All these data suggest that while (+)-(S)-PQ shows greater potency in terms of antiparasitic efficacy in rodents, it is also more hematotoxic than (-)-(R)-PQ in mice and dogs. Activity and toxicity differences of PQ enantiomers in different species can be attributed to their different pharmacokinetic and metabolic profiles. Taken together, these studies suggest that (-)-(R)-PQ may have a better safety margin than the racemate in human.

Anti-relapse activity of mirincamycin in the Plasmodium cynomolgi sporozoite-infected Rhesus monkey model.

BACKGROUND: Mirincamycin is a close analog of the drug clindamycin used to treat Plasmodium falciparum blood stages. The clinical need to treat Plasmodium vivax dormant liver stages and prevent relapse with a drug other than primaquine led to the evaluation of mirinicamycin against liver stages in animals. METHODS: cis-mirinicamycin and trans-mirinicamycin were evaluated as prophylaxis against early liver stages of Plasmodium berghei in mice and as antirelapse hypnozoiticides against Plasmodium cynomolgi in the Rhesus monkey (Macaca mulatta). RESULTS: Mirincamycin was very effective against early liver stages of P. berghei in mice: both cis and trans enantiomers were 90-100% causally prophylactic at 3.3 mg/kg/day for 3 days orally. Both cis and trans mirincamycin, however, failed to kill dormant liver stages (hypnozoites) in the P. cynomolgi infected Rhesus monkey, the only preclinical hypnozoite model. Mirincamycin enantiomers at 80 mg/kg/day for 7 days orally, a dose that generated exposures comparable to that seen clinically, did not prevent relapse in any of four monkeys. CONCLUSIONS: Although efficacy against early liver stages of P. berghei was thought to correlate with anti-hypnozoite activity in primates, for mirincamycin, at least, there was no correlation. The negative P. cynomolgi hypnozoite data from Rhesus monkeys indicates that mirincamycin is unlikely to have potential as a clinical anti-relapse agent.

Assessment of the prophylactic activity and pharmacokinetic profile of oral tafenoquine compared to primaquine for inhibition of liver stage malaria infections.

BACKGROUND: As anti-malarial drug resistance escalates, new safe and effective medications are necessary to prevent and treat malaria infections. The US Army is developing tafenoquine (TQ), an analogue of primaquine (PQ), which is expected to be more effective in preventing malaria in deployed military personnel. METHODS: To compare the prophylactic efficacy of TQ and PQ, a transgenic Plasmodium berghei parasite expressing the bioluminescent reporter protein luciferase was utilized to visualize and quantify parasite development in C57BL/6 albino mice treated with PQ and TQ in single or multiple regimens using a real-time in vivo imaging system (IVIS). As an additional endpoint, blood stage parasitaemia was monitored by flow cytometry. Comparative pharmacokinetic (PK) and liver distribution studies of oral and intravenous PQ and TQ were also performed. RESULTS: Mice treated orally with three doses of TQ at 5 mg/kg three doses of PQ at 25 mg/kg demonstrated no bioluminescence liver signal and no blood stage parasitaemia was observed suggesting both drugs showed 100% causal activity at the doses tested. Single dose oral treatment with 5 mg TQ or 25 mg of PQ, however, yielded different results as only TQ treatment resulted in causal prophylaxis in P. berghei sporozoite-infected mice. TQ is highly effective for causal prophylaxis in mice at a minimal curative single oral dose of 5 mg/kg, which is a five-fold improvement in potency versus PQ. PK studies of the two drugs administered orally to mice showed that the absolute bioavailability of oral TQ was 3.5-fold higher than PQ, and the AUC of oral TQ was 94-fold higher than oral PQ. The elimination half-life of oral TQ in mice was 28 times longer than PQ, and the liver tissue distribution of TQ revealed an AUC that was 188-fold higher than PQ. CONCLUSIONS: The increased drug exposure levels and longer exposure time of oral TQ in the plasma and livers of mice highlight the lead quality attributes that explain the much improved efficacy of TQ when compared to PQ.

Pharmacokinetic evaluation of intravenous artesunate in adults with uncomplicated falciparum malaria in Kenya: a phase II study.

BACKGROUND: Alternatives to treatment for malaria treatment of travellers are needed in the USA and in Europe for travellers who return with severe malaria infections. The objective of this study is to show the pharmacokinetic (PK) profile of intravenous artesunate (AS), which was manufactured under good manufacturing practice (GMP) conditions, in adults with uncomplicated falciparum malaria in Kenya. METHODS: The PK parameters of intravenous AS manufactured under current cGMP were evaluated after a single dose of drug at 2.4 mg/kg infused over 2 min in 28 adults with uncomplicated Plasmodium falciparum malaria. Plasma concentrations of AS and dihydroartemisinin (DHA) were measured using a validated liquid chromatography-mass spectrometry (LC-MS/MS) methodology. Pharmacokinetic data were analysed with a compartmental analysis for AS and DHA. RESULTS: The results suggest there were no drug-related adverse events in any of the patients. After intravenous infusion, the concentration of the parent drug rapidly declined, and the AS was converted to DHA. AS and DHA showed mean elimination half-lives of 0.17 hours and 1.30 hours, respectively. The high mean peak concentration (Cmax) of AS was shown to be 28,558 ng/mL while the Cmax of DHA was determined to be 2,932 ng/mL. Significant variability was noted in the PK profiles of the 28 patients tested. For example, Cmax values of AS were calculated to range from 3,362 to 55,873 ng/mL, and the Cmax value of DHA was noted to vary from 1,493 to 5,569 ng/mL. The mean area under the curve (AUC) of AS was shown to be approximately half that of DHA (1,878 ng · h/mL vs 3,543 ng · h/mL). The DHA/AS ratio observed was 1.94 during the one-day single treatment, and the AUC and half- life measured for DHA were significantly larger and longer than for AS. CONCLUSIONS: Intravenous AS can provide much higher peak concentrations of AS when compared to concentrations achieved with oral therapy; this may be crucial for the rapid elimination of parasites in patients with severe malaria. Given the much longer half-life of DHA compared to the short half-life of AS, DHA also plays a significant role in treatment of severe malaria.

Tafenoquine and NPC-1161B require CYP 2D metabolism for anti-malarial activity: implications for the 8-aminoquinoline class of anti-malarial compounds.

BACKGROUND: Tafenoquine (TQ) is an 8-aminoquinoline (8AQ) that has been tested in several Phase II and Phase III clinical studies and is currently in late stage development as an anti-malarial prophylactic agent. NPC-1161B is a promising 8AQ in late preclinical development. It has recently been reported that the 8AQ drug primaquine requires metabolic activation by CYP 2D6 for efficacy in humans and in mice, highlighting the importance of pharmacogenomics in the target population when administering primaquine. A logical follow-up study was to determine whether CYP 2D activation is required for other compounds in the 8AQ structural class. METHODS: In the present study, the anti-malarial activities of NPC-1161B and TQ were assessed against luciferase expressing Plasmodium berghei in CYP 2D knock-out mice in comparison with normal C57BL/6 mice (WT) and with humanized/CYP 2D6 knock-in mice by monitoring luminescence with an in vivo imaging system. These experiments were designed to determine the direct effects of CYP 2D metabolic activation on the anti-malarial efficacy of NPC-1161B and TQ. RESULTS: NPC-1161B and TQ exhibited no anti-malarial activity in CYP 2D knock-out mice when dosed at their ED100 values (1 mg/kg and 3 mg/kg, respectively) established in WT mice. TQ anti-malarial activity was partially restored in humanized/CYP 2D6 knock-in mice when tested at two times its ED100. CONCLUSIONS: The results reported here strongly suggest that metabolism of NPC-1161B and TQ by the CYP 2D enzyme class is essential for their anti-malarial activity. Furthermore, these results may provide a possible explanation for therapeutic failures for patients who do not respond to 8AQ treatment for relapsing malaria. Because CYP 2D6 is highly polymorphic, variable expression of this enzyme in humans represents a significant pharmacogenomic liability for 8AQs which require CYP 2D metabolic activation for efficacy, particularly for large-scale prophylaxis and eradication campaigns.

Nanoparticle formulations of decoquinate increase antimalarial efficacy against liver stage Plasmodium infections in mice.

Decoquinate has potent activity against both Plasmodium hepatic development and red cell replication when tested in vitro. Decoquinate, however, is practically insoluble in water. To achieve its maximal in vivo efficacy, we generated nanoparticle formulations of decoquinate with a mean particle size less than 400 nm. Three separate preparations at doses of decoquinate 0.5-5 mg/kg were examined in mice infected with Plasmodium berghei. Oral administration of nanoparticle decoquinate at a dose of 1.25 mg/kg effectively inhibited the liver-stage parasite growth and provided complete causal prophylactic protection. This efficacy is 15 fold greater than that observed for microparticle decoquinate, which requires minimal dose of 20 mg/kg for the same inhibitory effect. Further in vitro studies utilizing dose-response assays revealed that decoquinate nanoformulation was substantially more potent than decoquinate microsuspension in killing both liver and blood stage malarial parasites, proving its potential for therapeutic development. FROM THE CLINICAL EDITOR: In this study, a nanoparticle formulation of decoquinate is shown to have superior bioavailability and efficacy in a mouse model of malaria, paving the way to the development of novel, potentially less toxic and more effective therapeutics to combat a disease that still has an enormous impact on a global scale despite the available partially effective therapies.

The use of a prodrug approach to minimize potential CNS exposure of next generation quinoline methanols while maintaining efficacy in in vivo animal models.

The use of mefloquine (MQ) for antimalarial treatment and prophylaxis has diminished largely in response to concerns about its neurologic side effects. An analog campaign designed to maintain the efficacy of MQ while minimizing blood-brain barrier (BBB) penetration has resulted in the synthesis of a prodrug with comparable-to-superior in vivo efficacy versus mefloquine in a P. berghei mouse model while exhibiting a sixfold reduction in CNS drug levels. The prodrug, WR319670, performed poorly compared to MQ in in vitro efficacy assays, but had promising in vitro permeability in an MDCK-MDR1 cell line BBB permeability screen. Its metabolite, WR308245, exhibited high predicted BBB penetration with excellent in vitro efficacy. Both WR319670 and WR308245 cured 5/5 animals in separate in vivo efficacy studies. The in vivo efficacy of WR319670 was thought to be due to the formation of a more active metabolite, specifically WR308245. This was supported by pharmacokinetics studies in non-infected mice, which showed that both IV and oral administration of WR319670 produced essentially identical levels of WR319670 and WR308245 in both plasma and brain samples at all time points. In these studies, the levels of WR308245 in the brain were 1/4 and 1/6 that of MQ in similar IV and oral studies, respectively. These data show that the use of WR319670 as an antimalarial prodrug was able to maintain efficacy in in vivo efficacy screens, while significantly lowering overall penetration of drug and metabolites across the BBB.

To live free or being a parasite: The optimal foraging behavior may favor the evolution of entomopathogenic nematodes.

Facultative parasites can alternate between a free-living and a parasitic existence to complete their life cycle. Yet, it remains uncertain which lifestyle they prefer. The optimal foraging theory suggests that food preferences align with fitness benefits. To test this hypothesis, we investigated the facultative parasite nematode Rhabditis regina, assessing its host preference and the associated benefits. Two experiments were conducted using wild nematode populations collected from Phyllophaga polyphylla, their natural host. In the first experiment, we used a behavioral arena to assess host preference between the natural host and two experimental hosts: Spodoptera frugiperda which is an alternative host and dead Tenebrio molitor, which simulates a saprophytic environment. In the second experiment, we subjected wild nematodes to "experimental evolution" lasting 50 generations in S. frugiperda and 53 generations in T. molitor carcass. We then compared life history traits (the size, survival, number of larvae, and glycogen and triglycerides as energy reserves) of dauer larvae with those nematodes from P. polyphylla (control group). We found a significant preference for P. polyphylla, which correlated with higher values in the nematode's life history traits. In contrast, the preference for S. frugiperda and the saprophytic environment was lower, resulting in less efficient life history traits. These findings align with the optimal foraging theory, as the nematode's parasitic preferences are in line with maximizing fitness. This also indicates that R. regina exhibits specificity to P. polyphylla and is better adapted to a parasitic lifestyle than a free-living one, suggesting an evolutionary pathway towards parasitism.

Short-Term Adverse Effects of the Fourth Dose of Vaccination against COVID-19 in Adults over 40 Years of Age.

Booster vaccines are a strategy to mitigate the conditions in the health, social, and economic fields that the COVID-19 pandemic has brought. A series of adverse effects have been observed since the first vaccination. The present investigation aims to describe the short-term adverse effects of the fourth dose against COVID-19 in adults older than 40 from a region of Peru. The study population was over 40 years of age at the COVID-19 vaccination center in Trujillo, Peru. A 21-day follow-up was conducted from vaccination with the fourth dose, considering sex, age, body mass index, comorbidities, history of COVID-19 infection, vaccination schedule, and simultaneous vaccination against influenza as variables of interest. Multinomial logistic regression with robust variance was used to estimate the risk ratio (RR). In total, 411 people were recruited, and it was found that 86.9% of the participants presented adverse effects after injection with the fourth dose of the vaccine against COVID-19. Pain at the injection site was the most reported symptom after 3 days. Assessment of adverse effects after 3 days found that age ≥ 60 years was associated with a lower likelihood of adverse effects compared to those younger than 60 years (RRc: 0.32; 95% CI: 0.0.18-0.59), males compared to females were associated with a lower likelihood of adverse effects (RRc: 0.54; 95% CI 0.30-0.98), being overweight (RRc: 2.34; 95% CI: 1.12-4.89), and last vaccine with Pfizer-BioN-Tech (RRc: 0.42; 95% CI: 0.18-0.96). Associated adverse effects are mild to moderate. Injection site pain and general malaise are the most frequent adverse effects.

The metabolism of primaquine to its active metabolite is dependent on CYP 2D6.

BACKGROUND: The efficacy of the 8-aminoquinoline (8AQ) drug primaquine (PQ) has been historically linked to CYP-mediated metabolism. Although to date no clear evidence exists in the literature that unambiguously assigns the metabolic pathway or specific metabolites necessary for activity, recent literature suggests a role for CYP 2D6 in the generation of redox active metabolites. METHODS: In the present study, the specific CYP 2D6 inhibitor paroxetine was used to assess its effects on the production of specific phenolic metabolites thought to be involved in PQ efficacy. Further, PQ causal prophylactic (developing liver stage) efficacy against Plasmodium berghei in CYP 2D knockout mice was assessed in comparison with a normal C57 background and with humanized CYP 2D6 mice to determine the direct effects of CYP 2D6 metabolism on PQ activity. RESULTS: PQ exhibited no activity at 20 or 40 mg/kg in CYP 2D knockout mice, compared to 5/5 cures in normal mice at 20 mg/kg. The activity against developing liver stages was partially restored in humanized CYP 2D6 mice. CONCLUSIONS: These results unambiguously demonstrate that metabolism of PQ by CYP 2D6 is essential for anti-malarial causal prophylaxis efficacy.

CYP450 phenotyping and metabolite identification of quinine by accurate mass UPLC-MS analysis: a possible metabolic link to blackwater fever.

BACKGROUND: The naturally occurring alkaloid drug, quinine is commonly used for the treatment of severe malaria. Despite centuries of use, its metabolism is still not fully understood, and may play a role in the haemolytic disorders associated with the drug. METHODS: Incubations of quinine with CYPs 1A2, 2C9, 2C19, 2D6, and 3A4 were conducted, and the metabolites were characterized by accurate mass UPLC-MS(E) analysis. Reactive oxygen species generation was also measured in human erythrocytes incubated in the presence of quinine with and without microsomes. RESULTS: The metabolites 3-hydroxyquinine, 2'-oxoquininone, and O-desmethylquinine were observed after incubation with CYPs 3A4 (3-hydroxyquinine and 2'-oxoquininone) and 2D6 (O-desmethylquinine). In addition, multiple hydroxylations were observed both on the quinoline core and the quinuclidine ring system. Of the five primary abundance CYPs tested, 3A4, 2D6, 2C9, and 2C19 all demonstrated activity toward quinine, while 1A2 did not. Further, quinine produced robust dose-dependent oxidative stress in human erythrocytes in the presence of microsomes. CONCLUSIONS: Taken in context, these data suggest a CYP-mediated link between quinine metabolism and the poorly understood haemolytic condition known as blackwater fever, often associated with quinine ingestion.

The Coincidental Evolution of Virulence Partially Explains the Virulence in a Generalist Entomopathogenic.

PURPOSE: The parasites' virulence is labile after jumping to a new host species, and it might derivate in gaining virulence against a new host as a side effect of living in a non-host environment (coincidental evolution of virulence hypothesis). METHODS: To test this hypothesis, we monitored the experimental evolution of the Rhabditis regina nematode for over 290 generations (4 years) in three environments (strains): (1) the natural host, Phyllophaga polyphylla, (2) an alternate host, Tenebrio molitor, and (3) saprophytic medium (beef; the food that may provide evidence for the coincidental evolution of virulence). Each strain was exposed to P. polyphylla, T. molitor, or Galleria mellonella. We compared the host survival and immune response (proPO, PO, and lytic activity) of infected versus uninfected hosts. RESULTS: The saprophytic nematodes gained virulence only against G. mellonella. However, the P. polyphylla strain was more effective in killing P. polyphylla than T. molitor, and the T. molitor strain was more effective against T. molitor than P. polyphylla. Additionally, one dauer larva was sufficient to kill the hosts. Finally, the immune response did not differ between the challenged and control groups. CONCLUSION: The coincidental evolution of virulence partially explains our results, but they might also support the short-sighted hypothesis. Additionally, we found evidence for immunomodulation because nematodes passed unnoticed to the immune response. It is crucial to analyze the virulence of entomopathogens from the point of view of the evolution of virulence to be aware of potential scenarios that might limit biological control.

Pharmacokinetic profiles of artesunate following multiple intravenous doses of 2, 4, and 8 mg/kg in healthy volunteers: phase 1b study.

BACKGROUND: Severe malaria results in over a million deaths every year, most of them in children aged less than five years and living in sub-Saharan Africa. Injectable artesunate (AS) was recommended as initial treatment for severe malaria by WHO in 2006. The Walter Reed Army Institute of Research (WRAIR) has been developing a novel good manufacturing practice (GMP) injection of AS, which was approved by the US FDA for investigational drug use and distribution by the CDC. METHODS: Tolerability and pharmacokinetics of current GMP intravenous AS, as an anti-malarial agent, were evaluated after ascending multiple doses of 2, 4, and 8 mg/kg daily for three days with 2-minute infusion in 24 healthy subjects (divided into three groups) in the Phase 1 clinical trial study. RESULTS: Results showed that there were no dose-dependent increases in any adverse events. Drug concentrations showed no accumulation and no decline of the drug during the three days of treatment. After intravenous injection, parent drug rapidly declined and was converted to dihydroartemisinin (DHA) with overall mean elimination half-lives ranging 0.15-0.23 hr for AS and 1.23-1.63 hr for DHA, but the peak concentration (C(max)) of AS was much higher than that of DHA with a range of 3.08-3.78-folds. In addition, the AUC and C(max) values of AS and DHA were increased proportionally to the AS climbing multiple doses. DISCUSSION: The safety of injectable AS, even at the highest dose of 8 mg/kg increases the probability of therapeutic success of the drug even in patients with large variability of parasitaemia.

CYP450 phenotyping and accurate mass identification of metabolites of the 8-aminoquinoline, anti-malarial drug primaquine.

BACKGROUND: The 8-aminoquinoline (8AQ) drug primaquine (PQ) is currently the only approved drug effective against the persistent liver stage of the hypnozoite forming strains Plasmodium vivax and Plasmodium ovale as well as Stage V gametocytes of Plasmodium falciparum. To date, several groups have investigated the toxicity observed in the 8AQ class, however, exact mechanisms and/or metabolic species responsible for PQ's haemotoxic and anti-malarial properties are not fully understood. METHODS: In the present study, the metabolism of PQ was evaluated using in vitro recombinant metabolic enzymes from the cytochrome P450 (CYP) and mono-amine oxidase (MAO) families. Based on this information, metabolite identification experiments were performed using nominal and accurate mass measurements. RESULTS: Relative activity factor (RAF)-weighted intrinsic clearance values show the relative role of each enzyme to be MAO-A, 2C19, 3A4, and 2D6, with 76.1, 17.0, 5.2, and 1.7% contributions to PQ metabolism, respectively. CYP 2D6 was shown to produce at least six different oxidative metabolites along with demethylations, while MAO-A products derived from the PQ aldehyde, a pre-cursor to carboxy PQ. CYPs 2C19 and 3A4 produced only trace levels of hydroxylated species. CONCLUSIONS: As a result of this work, CYP 2D6 and MAO-A have been implicated as the key enzymes associated with PQ metabolism, and metabolites previously identified as potentially playing a role in efficacy and haemolytic toxicity have been attributed to production via CYP 2D6 mediated pathways.

Ketotifen is an antimalarial prodrug of norketotifen with blood schizonticidal and liver-stage efficacy.

Ketotifen is known to exhibit antimalarial activity in mouse and monkey malaria models. However, the low plasma levels and short half life of the drug do not adequately explain its in vivo efficacy. We synthesized most of the known metabolites of ketotifen and evaluated their antimalarial activity and pharmacokinetics in mice. Norketotifen, the de-methylated metabolite of ketotifen, was a more potent antimalarial in vitro as compared to ketotifen, and exhibited equivalent activity in vivo against asexual blood and developing liver-stage parasites. After ketotifen dosing, norketotifen levels were much higher than ketotifen relative to the IC50s of the compounds against Plasmodium falciparum in vitro. The data support the notion that the antimalarial activity of ketotifen in mice is mediated through norketotifen.

Absolute bioavailability of cis-mirincamycin and trans-mirincamycin in healthy rhesus monkeys and ex vivo antimalarial activity against Plasmodium falciparum.

The pharmacokinetics, oral bioavailability, and ex vivo antimalarial activity of mirincamycin isomers in a healthy rhesus monkey model were assessed to support lead optimization of novel nonhemolytic drugs for radical cure and causal prophylaxis of malaria. Fourteen male rhesus monkeys were randomized to four groups, which included cis and trans isomers by the oral and intravenous routes, with vehicle-only controls for each dosing route. Concentration-time data were collected for 7 days and were analyzed by noncompartmental analysis. cis-Mirincamycin had an absolute oral bioavailability of 13.6%, which was slightly higher than that of trans-mirincamycin (11.7%), but this difference was not statistically significant. There was a statistically significant difference between the area under the concentration-time curve from zero to 48 h (AUC(0-48)) of cis-mirincamycin and that of trans-mirincamycin after oral dosing. When cultured in vitro with the W2 clone of Plasmodium falciparum, the 50% inhibitory concentrations for cis-mirincamycin, trans-mirincamycin, and dihydroartemisinin were 11,300, 12,300, and 2.30 nM, respectively. However, when dosed primate plasma was cultured ex vivo against the W2 clone, both isomers had much greater relative potencies than their in vitro activities relative to results for dihydroartemisinin, an increase of approximately 100-fold for the cis isomer and 150-fold for the trans isomer. Further, oral ex vivo activity was significantly higher than intravenous activity for both isomers, particularly during the first 90 min following dosing, suggesting the first-pass formation of one or more metabolites with blood-stage antimalarial activity. Identification of the metabolic pathways and metabolites may help to further delineate the properties of this class of drugs with previously demonstrated liver-stage antimalarial activity.

New imidazolidinedione derivatives as antimalarial agents.

A series of new N-alky- and N-alkoxy-imidazolidinediones was prepared and assessed for prophylactic and radical curative activities in mouse and Rhesus monkey models. New compounds are generally metabolically stable, weakly active in vitro against Plasmodium falciparum clones (D6 and W2) and in mice infected with Plasmodium berghei sporozoites. Representative compounds 8e and 9c showed good causal prophylactic activity in Rhesus monkeys dosed 30 mg/kg/day for 3 consecutive days by IM, delayed patency for 19-21 days and 54-86 days, respectively, as compared to the untreated control. By oral, 9c showed only marginal activity in causal prophylactic and radical curative tests at 50 mg/kg/day×3 and 30 mg/kg/day×7 plus chloroquine 10 mg/kg for 7 days, respectively.