Scalable preparation and differential pharmacologic and toxicologic profiles of primaquine enantiomers.
ABSTRACT: 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.
Project description:The current interest in malaria elimination has led to a renewed interest in drugs that can be used for mass administration to minimize malaria transmission. Primaquine (PQ) is the only generally available drug with a strong activity against mature Plasmodium falciparum gametocytes, the parasite stage responsible for transmission. Despite concerns about PQ-induced hemolysis in glucose-6-phosphate dehydrogenase (G6PD)-deficient individuals, a single dose of PQ may be safe and efficacious in clearing gametocytes that persist after conventional treatment. As part of a mass drug intervention, we determined the hemolytic effect of sulfadoxine-pyrimethamine (SP) plus artesunate (AS) plus a single dose of primaquine (PQ; 0.75 mg/kg of body weight) in children aged 1 to 12 years. Children were randomized to receive SP+AS+PQ or placebo; those with a hemoglobin (Hb) level below 8 g/dl were excluded from receiving PQ and received SP+AS. The Hb concentration was significantly reduced 7 days after SP+AS+PQ treatment but not after placebo or SP+AS treatment. This reduction in Hb was most pronounced in G6PD-deficient (G6PD A-) individuals (-2.5 g/dl; 95% confidence interval [95% CI], -1.2 to -3.8 g/dl) but was also observed in heterozygotes (G6PD A) (-1.6 g/dl; 95% CI, -0.9 to -2.2 g/dl) and individuals with the wild-type genotype (G6PD B) (-0.5 g/dl; 95% CI, -0.4 to -0.6 g/dl). Moderate anemia (Hb level of <8 g/dl) was observed in 40% (6/15 individuals) of the G6PD A-, 11.1% (3/27 individuals) of the G6PD A, and 4.5% (18/399 individuals) of the G6PD B individuals; one case of severe anemia (Hb level of <5 g/dl) was observed. PQ may cause moderate anemia when coadministered with artemisinins, and excluding individuals based on G6PD status alone may not be sufficient to prevent PQ-induced hemolysis.
Project description:Individuals with glucose 6-phosphate dehydrogenase (G6PD) deficiency are at risk for the development of hemolytic anemia when given 8-aminoquinolines (8-AQs), an important class of antimalarial/antiinfective therapeutics. However, there is no suitable animal model that can predict the clinical hemolytic potential of drugs. We developed and validated a human (hu)RBC-SCID mouse model by giving nonobese diabetic/SCID mice daily transfusions of huRBCs from G6PD-deficient donors. Treatment of SCID mice engrafted with G6PD-deficient huRBCs with primaquine, an 8-AQ, resulted in a dose-dependent selective loss of huRBCs. To validate the specificity of this model, we tested known nonhemolytic antimalarial drugs: mefloquine, chloroquine, doxycycline, and pyrimethamine. No significant loss of G6PD-deficient huRBCs was observed. Treatment with drugs known to cause hemolytic toxicity (pamaquine, sitamaquine, tafenoquine, and dapsone) resulted in loss of G6PD-deficient huRBCs comparable to primaquine. This mouse model provides an important tool to test drugs for their potential to cause hemolytic toxicity in G6PD-deficient populations.
Project description:Albendazole is an anthelmintic drug widely used in the treatment of neurocysticercosis (NCC), an infection of the brain with Taenia solium cysts. However, drug levels of its active metabolite, albendazole sulfoxide (ABZSO), are erratic, likely resulting in decreased efficacy and suboptimal cure rates in NCC. Racemic albendazole sulfoxide is composed of ABZSO (+)-(R)- and (-)-(S) enantiomers that have been shown to differ in pharmacokinetics and activity against other helminths. The antiparasitic activities of racemic ABZSO and its (+)-(R)- and (-)-(S) enantiomers against T. solium cysts were evaluated in vitro. Parasites were collected from naturally infected pigs, cultured, and exposed to the racemic mixture or to each enantiomer (range, 10 to 500 ng/ml) or to praziquantel as a reference drug. The activity of each compound against cysts was assayed by measuring the ability to evaginate and inhibition of alkaline phosphatase (AP) and parasite antigen release. (+)-(R)-ABZSO was significantly more active than (-)-(S)-ABZSO in suppressing the release of AP and antigen into the supernatant in a dose- and time-dependent manner, indicating that most of the activity of ABZSO resides in the (+)-(R) enantiomer. Use of this enantiomer alone may lead to increased efficacy and/or less toxicity compared to albendazole.
Project description:Background:The World Health Organization recommendation on the use of a single low dose of primaquine (SLD-PQ) to reduce Plasmodium falciparum malaria transmission requires more safety data. Methods:We conducted an open-label, nonrandomized, dose-adjustment trial of the safety of 3 single doses of primaquine in glucose-6-phosphate dehydrogenase (G6PD)-deficient adult males in Mali, followed by an assessment of safety in G6PD-deficient boys aged 11-17 years and those aged 5-10 years, including G6PD-normal control groups. The primary outcome was the greatest within-person percentage drop in hemoglobin concentration within 10 days after treatment. Results:Fifty-one participants were included in analysis. G6PD-deficient adult males received 0.40, 0.45, or 0.50 mg/kg of SLD-PQ. G6PD-deficient boys received 0.40 mg/kg of SLD-PQ. There was no evidence of symptomatic hemolysis, and adverse events considered related to study drug (n = 4) were mild. The mean largest within-person percentage change in hemoglobin level between days 0 and 10 was -9.7% (95% confidence interval [CI], -13.5% to -5.90%) in G6PD-deficient adults receiving 0.50 mg/kg of SLD-PQ, -11.5% (95% CI, -16.1% to -6.96%) in G6PD-deficient boys aged 11-17 years, and -9.61% (95% CI, -7.59% to -13.9%) in G6PD-deficient boys aged 5-10 years. The lowest hemoglobin concentration at any point during the study was 92 g/L. Conclusion:SLD-PQ doses between 0.40 and 0.50 mg/kg were well tolerated in G6PD-deficient males in Mali. Clinical Trials Registration:NCT02535767.
Project description:Vivax malaria remains a major cause of morbidity in the subtropics. To undermine the stability of the disease, drugs are required that prevent relapse and provide reservoir reduction. A 14-day course of primaquine (PQ) is effective but cannot safely be used in routine practice because of its interaction with glucose-6-phosphate dehydrogenase (G6PD) deficiency for which testing is seldom available. Safe and effective use of PQ without the need for G6PD testing would be ideal. The efficacy and safety of an 8-week, once weekly PQ regimen was compared with current standard treatment (chloroquine alone) and a 14-day PQ regimen.200 microscopically confirmed Plasmodium vivax patients were randomly assigned to either once weekly 8-week PQ (0.75 mg/kg/week), once weekly 8-week placebo, or 14-day PQ (0.5mg/kg/day) in North West Frontier Province, Pakistan. All patients were treated with a standard chloroquine dose and tested for G6PD deficiency. Deficient patients were assigned to the 8-week PQ group. Failure was defined as any subsequent episode of vivax malaria over 11 months of observation. There were 22/71 (31.0%) failures in the placebo group and 1/55 (1.8%) and 4/75 (5.1%) failures in the 14-day and 8-week PQ groups, respectively. Adjusted odds ratios were: for 8-week PQ vs. placebo-0.05 (95%CI: 0.01-0.2, p<0.001) and for 14-day PQ vs. placebo-0.01 (95%CI: 0.002-0.1, p<0.001). Restricted analysis allowing for a post-treatment prophylactic effect confirmed that the 8-week regimen was superior to current treatment. Only one G6PD deficient patient presented. There were no serious adverse events.A practical radical treatment for vivax malaria is essential for control and elimination of the disease. The 8-week PQ course is more effective at preventing relapse than current treatment with chloroquine alone. Widespread use of the 8-week regimen could make an important contribution to reservoir reduction or regional elimination where G6PD testing is not available.ClinicalTrials.gov NCT00158587.
Project description:Haemolysis risk with single dose or short course primaquine was evaluated in glucose-6-phosphate dehydrogenase (G6PD) deficient people.Major electronic databases (to August 2016) were searched for single or short course 8-aminoquinolines (8-AQ) in (1) randomized comparisons against placebo in G6PD deficient people; and (2) observational comparisons in G6PD deficient compared to replete people. Two authors independently assessed eligibility, risk-of-bias, and extracted data.Five randomized controlled trials and four controlled observational cohorts were included. In G6PD deficient individuals, high-dose (0.75 mg/kg) PQ resulted in lower average haemoglobin levels at 7 days (mean difference [MD] -1.45 g/dl, 95% CI -2.17 to -0.74, 2 trials) and larger percentage fall from baseline to day 7 (MD -10.31%, 95% CI -17.69 to -2.92, 3 trials) compared to placebo. In G6PD deficient compared to replete people, average haemoglobin was lower at 7 days (MD -1.19 g/dl, 95% CI -1.94 to -0.44, 2 trials) and haemoglobin change from baseline to day 7 was greater (MD -9.10%, 95% CI -12.55 to -5.65, 5 trials). One small trial evaluated mid-range PQ dose (0.4-0.5 mg/kg) in G6PD deficient people, with no difference detected in average haemoglobin at day 7 compared to placebo. In one cohort comparing G6PD deficient and replete people there was a greater fall with G6PD deficiency (MD -4.99%, 95% CI -9.96 to -0.02). For low-dose PQ (0.1-0.25 mg/kg) in G6PD deficient people, haemoglobin change from baseline was similar to the placebo group (MD 1.72%, 95% CI -1.89 to 5.34, 2 trials). Comparing low dose PQ in G6PD deficient with replete people, the average haemoglobin was lower in the G6PD deficient group at 7 days (-0.57 g (95% CI -0.97 to -0.17, 1 trial)); although change from baseline was similar (MD -1.45%, 95% CI -5.69 to 2.78, 3 trials).Falls in average haemoglobin are less marked with the 0.1 to 0.25 mg/kg PQ than with the 0.75 mg/kg dose, and severe haemolytic events are not common. However, data were limited and the evidence GRADE was low or very low certainty.
Project description:The widespread use of primaquine (PQ) radical cure for P. vivax, is constrained by concerns over its safety. We used routinely collected patient data to compare the overall morbidity and mortality in patients treated with and without PQ without prior testing of Glucose-6-Phosphate-Dehydrogenase (G6PD) deficiency in Papua, Indonesia, where there is a low prevalence of G6PD deficiency. Records were collated from patients older than 1 year, with P. vivax infection, who were treated with an artemisinin combination therapy (ACT). The risks of re-presentation, hospitalization, major fall in haemoglobin and death within 30 days were quantified and compared between patients treated with and without PQ using a Cox regression model. In total 26,216 patients with P. vivax malaria presented to the hospital with malaria during the study period. Overall 27.56% (95% Confidence Interval (95%CI): 26.96-28.16) of 21,344 patients treated with PQ re-presented with any illness within 30 days and 1.69% (1.51-1.88) required admission to hospital. The corresponding risks were higher in the 4,872 patients not treated with PQ; Adjusted Hazard Ratio (AHR) = 0.84 (0.79-0.91; p<0.001) and 0.54 (0.41-0.70; p<0.001) respectively. By day 30, 14.15% (12.45-16.05) of patients who had received PQ had a fall in haemoglobin (Hb) below 7g/dl compared to 20.43% (16.67-24.89) of patients treated without PQ; AHR = 0.66 (0.45-0.97; p = 0.033). A total of 75 (0.3%) patients died within 30 days of treatment with a mortality risk of 0.27% (0.21-0.35) in patients treated with PQ, compared to 0.38% (0.24-0.60) without PQ; AHR = 0.79 (0.43-1.45; p = 0.448). In Papua, Indonesia routine administration of PQ radical cure without prior G6PD testing, was associated with lower risk of all cause hospitalization and other serious adverse clinical outcomes. In areas where G6PD testing is not available or cannot be delivered reliably, the risks of drug induced haemolysis should be balanced against the potential benefits of reducing recurrent P. vivax malaria and its associated morbidity and mortality.
Project description:Afghanistan's national guidelines recommend primaquine (PQ) for radical treatment of Plasmodium vivax malaria, but this is rarely implemented because of concerns over potential hemolysis in patients who have G6PD deficiency. Between August 2009 and February 2014, we conducted an open-label, randomized controlled trial of chloroquine (CQ) alone versus chloroquine plus primaquine (0.25 mg base/kg/day for 14 days) (CQ+PQ) in patients aged 6 months and older with microscopy confirmed P. vivax infection. In the CQ+PQ group, G6PD deficiency was excluded by fluorescent spot testing. The primary outcome was P. vivax recurrence assessed by survival analysis over one year follow-up. Of 593 patients enrolled, 570 attended at or after 14 days of follow-up. Plasmodium vivax recurrences occurred in 37 (13.1%) of 282 patients in the CQ+PQ arm versus 86 (29.9%) of 288 in the CQ arm (Cox proportional hazard ratio [HR] 0.37, 95% confidence interval [CI] 0.25-0.54) (intention-to-treat analysis). Protection against recurrence was greater in the first 6 months of follow-up (HR 0.082; 95% CI 0.029-0.23) than later (HR 0.65, 95% CI 0.41-1.03). Five of seven patients requiring hospital admission were considered possible cases of PQ-related hemolysis, and PQ was stopped in a further six; however, in none of these cases did hemoglobin fall by ? 2 g/dL or to below 7 g/dL, and genotyping did not detect any cases of Mediterranean variant G6PD deficiency. PQ 0.25 mg/kg/day for 14 days prevents relapse of P. vivax in Afghanistan. Patient visits during the first week may improve adherence. Implementation will require deployment of point-of-care phenotypic tests for G6PD deficiency.
Project description:This study assessed the safety of the new World Health Organization (WHO) recommendation of adding a single low-dose of primaquine (PQ) to standard artemisinin-based combination therapy (ACT), regardless of individual glucose-6-phosphate dehydrogenase (G6PD) status, for treatment of acute uncomplicated Plasmodium falciparum malaria in Tanzania.Men and non-pregnant, non-lactating women aged ≥1 year with uncomplicated P. falciparum malaria were enrolled and randomized to either standard artemether-lumefantrine (AL) regimen alone or with a 0.25 mg/kg single-dose of PQ. PQ was administered concomitantly with the first AL dose. All drug doses were supervised. Safety was evaluated between days 0 and 28. G6PD status was assessed using rapid test (CareStart™) and molecular genotyping. The primary endpoint was mean percentage relative reduction in haemoglobin (Hb) concentration (g/dL) between days 0 and 7 by genotypic G6PD status and treatment arm.Overall, 220 patients, 110 per treatment arm, were enrolled, of whom 33/217 (15.2 %) were phenotypically G6PD deficient, whereas 15/110 (13.6 %) were genotypically hemizygous males, 5/110 (4.5 %) homozygous females and 22/110 (20 %) heterozygous females. Compared to genotypically G6PD wild-type/normal [6.8, 95 % confidence interval (CI) 4.67-8.96], only heterozygous patients in AL arm had significant reduction in day-7 mean relative Hb concentration (14.3, 95 % CI 7.02-21.55, p=0.045), however, none fulfilled the pre-defined haemolytic threshold value of ≥25 % Hb reduction. After adjustment for baseline parasitaemia, Hb, age and sex the mean relative Hb reduction was not statistically significant in both heterozygous and hemizygous/homozygous patients in both arms. A majority of the adverse events (AEs) were mild and unrelated to the study drugs. However, six (4.4 %) episodes, three per treatment arm, of acute haemolytic anaemia occurred between days 0 and 7. Three occurred in phenotypically G6PD deficient patients, two in AL and one in AL + PQ arm, but none in genotypically hemizygous/homozygous patients. All patients with acute haemolytic anaemia recovered without medical intervention.The findings support that the WHO recommendation of adding a single low-dose of PQ to standard AL regimen is safe for the treatment of acute uncomplicated P. falciparum malaria regardless of G6PD status in Tanzania. Trial registration number NCT02090036.
Project description:Primaquine (PQ) actively clears mature Plasmodium falciparum gametocytes but in glucose-6-phosphate dehydrogenase deficient (G6PDd) individuals can cause hemolysis. We assessed the safety of low-dose PQ in combination with artemether-lumefantrine (AL) or dihydroartemisinin-piperaquine (DP) in G6PDd African males with asymptomatic P. falciparum malaria.In Burkina Faso, G6PDd adult males were randomized to treatment with AL alone (n = 10) or with PQ at 0.25 (n = 20) or 0.40 mg/kg (n = 20) dosage; G6PD-normal males received AL plus 0.25 (n = 10) or 0.40 mg/kg (n = 10) PQ. In The Gambia, G6PDd adult males and boys received DP alone (n = 10) or with 0.25 mg/kg PQ (n = 20); G6PD-normal males received DP plus 0.25 (n = 10) or 0.40 mg/kg (n = 10) PQ. The primary study endpoint was change in hemoglobin concentration during the 28-day follow-up. Cytochrome P-450 isoenzyme 2D6 (CYP2D6) metabolizer status, gametocyte carriage, haptoglobin, lactate dehydrogenase levels and reticulocyte counts were also determined. In Burkina Faso, the mean maximum absolute change in hemoglobin was -2.13 g/dL (95% confidence interval [CI], -2.78, -1.49) in G6PDd individuals randomized to 0.25 PQ mg/kg and -2.29 g/dL (95% CI, -2.79, -1.79) in those receiving 0.40 PQ mg/kg. In The Gambia, the mean maximum absolute change in hemoglobin concentration was -1.83 g/dL (95% CI, -2.19, -1.47) in G6PDd individuals receiving 0.25 PQ mg/kg. After adjustment for baseline concentrations, hemoglobin reductions in G6PDd individuals in Burkina Faso were more pronounced compared to those in G6PD-normal individuals receiving the same PQ doses (P = 0.062 and P = 0.022, respectively). Hemoglobin levels normalized during follow-up. Abnormal haptoglobin and lactate dehydrogenase levels provided additional evidence of mild transient hemolysis post-PQ.Single low-dose PQ in combination with AL and DP was associated with mild and transient reductions in hemoglobin. None of the study participants developed moderate or severe anemia; there were no severe adverse events. This indicates that single low-dose PQ is safe in G6PDd African males when used with artemisinin-based combination therapy.Clinicaltrials.gov NCT02174900 Clinicaltrials.gov NCT02654730.