Single-Dose Tafenoquine to Prevent Relapse of Plasmodium vivax Malaria.

BACKGROUND: Treatment of Plasmodium vivax malaria requires the clearing of asexual parasites, but relapse can be prevented only if dormant hypnozoites are cleared from the liver (a treatment termed "radical cure"). Tafenoquine is a single-dose 8-aminoquinoline that has recently been registered for the radical cure of P. vivax. METHODS: This multicenter, double-blind, double-dummy, parallel group, randomized, placebo-controlled trial was conducted in Ethiopia, Peru, Brazil, Cambodia, Thailand, and the Philippines. We enrolled 522 patients with microscopically confirmed P. vivax infection (>100 to <100,000 parasites per microliter) and normal glucose-6-phosphate dehydrogenase (G6PD) activity (with normal activity defined as ≥70% of the median value determined at each trial site among 36 healthy male volunteers who were otherwise not involved in the trial). All patients received a 3-day course of chloroquine (total dose of 1500 mg). In addition, patients were assigned to receive a single 300-mg dose of tafenoquine on day 1 or 2 (260 patients), placebo (133 patients), or a 15-mg dose of primaquine once daily for 14 days (129 patients). The primary outcome was the Kaplan-Meier estimated percentage of patients who were free from recurrence at 6 months, defined as P. vivax clearance without recurrent parasitemia. RESULTS: In the intention-to-treat population, the percentage of patients who were free from recurrence at 6 months was 62.4% in the tafenoquine group (95% confidence interval [CI], 54.9 to 69.0), 27.7% in the placebo group (95% CI, 19.6 to 36.6), and 69.6% in the primaquine group (95% CI, 60.2 to 77.1). The hazard ratio for the risk of recurrence was 0.30 (95% CI, 0.22 to 0.40) with tafenoquine as compared with placebo (P<0.001) and 0.26 (95% CI, 0.18 to 0.39) with primaquine as compared with placebo (P<0.001). Tafenoquine was associated with asymptomatic declines in hemoglobin levels, which resolved without intervention. CONCLUSIONS: Single-dose tafenoquine resulted in a significantly lower risk of P. vivax recurrence than placebo in patients with phenotypically normal G6PD activity. (Funded by GlaxoSmithKline and Medicines for Malaria Venture; DETECTIVE ClinicalTrials.gov number, NCT01376167 .).

Tafenoquine plus chloroquine for the treatment and relapse prevention of Plasmodium vivax malaria (DETECTIVE): a multicentre, double-blind, randomised, phase 2b dose-selection study.

BACKGROUND: Clinical effectiveness of previous regimens to treat Plasmodium vivax infection have been hampered by compliance. We aimed to assess the dose-response, safety, and tolerability of single-dose tafenoquine plus 3-day chloroquine for P vivax malaria radical cure. METHODS: In this double-blind, randomised, dose-ranging phase 2b study, men and women (aged ≥16 years) with microscopically confirmed P vivax monoinfection (parasite density >100 to <100,000 per µL blood) were enrolled from community health centres and hospitals across seven sites in Brazil, Peru, India, and Thailand. Patients with glucose-6-phosphate dehydrogenase enzyme activity of less than 70% were excluded. Eligible patients received chloroquine (days 1-3) and were randomly assigned (1:1:1:1:1:1) by a computer-generated randomisation schedule to receive single-dose tafenoquine 50 mg, 100 mg, 300 mg, or 600 mg, primaquine 15 mg for 14 days, or chloroquine alone. Randomisation was stratified by baseline parasite count (≤7500 and >7500 per µL blood). The primary efficacy endpoint was relapse-free efficacy at 6 months from initial dose (ie, clearance of initial infection without subsequent microscopically confirmed infection), analysed by intention to treat. This study is registered with ClinicalTrials.gov, number NCT01376167. FINDINGS: Between Sept 19, 2011, and March 25, 2013, 329 patients were randomly assigned to a treatment group (chloroquine plus tafenoquine 50 mg [n=55], 100 mg [n=57], 300 mg [n=57], 600 mg [n=56]; or to chloroquine plus primaquine [n=50]; or chloroquine alone [n=54]). Relapse-free efficacy at 6 months was 57·7% (95% CI 43-70) with tafenoquine 50 mg, 54·1% (40-66) with tafenoquine 100 mg, 89·2% (77-95) with tafenoquine 300 mg, 91·9% (80-97) with tafenoquine 600 mg, 77·3% (63-87) with primaquine, and 37·5% (23-52) with chloroquine alone. Tafenoquine 300 mg and 600 mg had better efficacy than chloroquine alone (treatment differences 51·7% [95% CI 35-69], p<0·0001, with tafenoquine 300 mg and 54·5% [38-71], p<0·0001, with tafenoquine 600 mg), as did primaquine (treatment difference 39·9% [21-59], p=0·0004). Adverse events were similar between treatments. 29 serious adverse events occurred in 26 (8%) of 329 patients; QT prolongation was the most common serious adverse event (11 [3%] of 329), occurring in five (2%) of 225 patients receiving tafenoquine, four (8%) of 50 patients receiving primaquine, and two (4%) of 54 patients receiving chloroquine alone, with no evidence of an additional effect on QT of chloroquine plus tafenoquine coadministration. INTERPRETATION: Single-dose tafenoquine 300 mg coadministered with chloroquine for P vivax malaria relapse prevention was more efficacious than chloroquine alone, with a similar safety profile. As a result, it has been selected for further clinical assessment in phase 3. FUNDING: GlaxoSmithKline, Medicines for Malaria Venture.

Pharmacokinetic interactions and safety evaluations of coadministered tafenoquine and chloroquine in healthy subjects.

AIMS: The long-acting 8-aminoquinoline tafenoquine (TQ) coadministered with chloroquine (CQ) may radically cure Plasmodium vivax malaria. Coadministration therapy was evaluated for a pharmacokinetic interaction and for pharmacodynamic, safety and tolerability characteristics. METHODS: Healthy subjects, 18-55 years old, without documented glucose-6-phosphate dehydrogenase deficiency, received CQ alone (days 1-2, 600 mg; and day 3, 300 mg), TQ alone (days 2 and 3, 450 mg) or coadministration therapy (day 1, CQ 600 mg; day 2, CQ 600 mg + TQ 450 mg; and day 3, CQ 300 mg + TQ 450 mg) in a randomized, double-blind, parallel-group study. Blood samples for pharmacokinetic and pharmacodynamic analyses and safety data, including electrocardiograms, were collected for 56 days. RESULTS: The coadministration of CQ + TQ had no effect on TQ AUC0-t , AUC0-∞ , Tmax or t1/2 . The 90% confidence intervals of CQ + TQ vs. TQ for AUC0-t , AUC0-∞ and t1/2 indicated no drug interaction. On day 2 of CQ + TQ coadministration, TQ Cmax and AUC0-24 increased by 38% (90% confidence interval 1.27, 1.64) and 24% (90% confidence interval 1.04, 1.46), respectively. The pharmacokinetics of CQ and its primary metabolite desethylchloroquine were not affected by TQ. Coadministration had no clinically significant effect on QT intervals and was well tolerated. CONCLUSIONS: No clinically significant safety or pharmacokinetic/pharmacodynamic interactions were observed with coadministered CQ and TQ in healthy subjects.

Tafenoquine co-administered with dihydroartemisinin-piperaquine for the radical cure of Plasmodium vivax malaria (INSPECTOR): a randomised, placebo-controlled, efficacy and safety study.

BACKGROUND: Tafenoquine, co-administered with chloroquine, is approved for the radical cure (prevention of relapse) of Plasmodium vivax malaria. In areas of chloroquine resistance, artemisinin-based combination therapies are used to treat malaria. This study aimed to evaluate tafenoquine plus the artemisinin-based combination therapy dihydroartemisinin-piperaquine for the radical cure of P vivax malaria. METHODS: In this double-blind, double-dummy, parallel group study, glucose-6-phosphate dehydrogenase-normal Indonesian soldiers with microscopically confirmed P vivax malaria were randomly assigned by means of a computer-generated randomisation schedule (1:1:1) to dihydroartemisinin-piperaquine alone, dihydroartemisinin-piperaquine plus a masked single 300-mg dose of tafenoquine, or dihydroartemisinin-piperaquine plus 14 days of primaquine (15 mg). The primary endpoint was 6-month relapse-free efficacy following tafenoquine plus dihydroartemisinin-piperaquine versus dihydroartemisinin-piperaquine alone in all randomly assigned patients who received at least one dose of masked treatment and had microscopically confirmed P vivax at baseline (microbiological intention-to-treat population). Safety was a secondary outcome and the safety population comprised all patients who received at least one dose of masked medication. This study is registered with ClinicalTrials.gov, NCT02802501 and is completed. FINDINGS: Between April 8, 2018, and Feb 4, 2019, of 164 patients screened for eligibility, 150 were randomly assigned (50 per treatment group). 6-month Kaplan-Meier relapse-free efficacy (microbiological intention to treat) was 11% (95% CI 4-22) in patients treated with dihydroartemisinin-piperaquine alone versus 21% (11-34) in patients treated with tafenoquine plus dihydroartemisinin-piperaquine (hazard ratio 0·44; 95% CI [0·29-0·69]) and 52% (37-65) in the primaquine plus dihydroartemisinin-piperaquine group. Adverse events over the first 28 days were reported in 27 (54%) of 50 patients treated with dihydroartemisinin-piperaquine alone, 29 (58%) of 50 patients treated with tafenoquine plus dihydroartemisinin-piperaquine, and 22 (44%) of 50 patients treated with primaquine plus dihydroartemisinin-piperaquine. Serious adverse events were reported in one (2%) of 50, two (4%) of 50, and two (4%) of 50 of patients, respectively. INTERPRETATION: Although tafenoquine plus dihydroartemisinin-piperaquine was statistically superior to dihydroartemisinin-piperaquine alone for the radical cure of P vivax malaria, the benefit was not clinically meaningful. This contrasts with previous studies in which tafenoquine plus chloroquine was clinically superior to chloroquine alone for radical cure of P vivax malaria. FUNDING: ExxonMobil, Bill & Melinda Gates Foundation, Newcrest Mining, UK Government all through Medicines for Malaria Venture; and GSK. TRANSLATION: For the Indonesian translation of the abstract see Supplementary Materials section.

Antiviral activity and safety of aplaviroc with lamivudine/zidovudine in HIV-infected, therapy-naive patients: the ASCENT (CCR102881) study.

BACKGROUND: This Phase IIb study explored the antiviral activity and safety of the investigational CCR5 antagonist aplaviroc (APL) in antiretroviral-naive patients harbouring R5-tropic virus. METHODS: One hundred and forty-seven patients were randomized 2:2:1 to one of two APL dosing regimens or efavirenz (EFV). All dosage arms were administered twice daily and in combination with lamivudine/zidovudine (3TC/ZDV; Combivir, COM). Efficacy, safety, and pharmacokinetic parameters were assessed. RESULTS: This study was prematurely terminated due to APL-associated idiosyncratic hepatotoxicity. The primary endpoint of the study was the proportion of patients with plasma HIV-1 RNA <400 copies/ml who remained on randomized treatment through week 12. Of the 147 patients enrolled, 145 patients received one dose of treatment and were included in the intention-to-treat population. The proportion of patients with HIV-1 RNA <400 copies/ml at week 12 was 53%, 50% and 66% in the APL 600 mg twice daily, APL 800 mg twice daily, and EFV arms, respectively. Common clinical adverse events (AEs) were diarrhoea, nausea, fatigue and headache. APL demonstrated non-linear pharmacokinetics with high interpatient variability. In addition to the hepatic findings, there was an apparent dose-response relationship in the incidence of diarrhoea. CONCLUSIONS: Whereas target plasma concentrations of APL were achieved, the antiviral activity of APL as the third agent in a triple drug regimen did not appear to be comparable to EFV in this treatment-naive patient population.

Relationship of potency and resilience to drug resistant mutations for GW420867X revealed by crystal structures of inhibitor complexes for wild-type, Leu100Ile, Lys101Glu, and Tyr188Cys mutant HIV-1 reverse transcriptases.

The selection of drug resistant viruses is a major problem in efforts to combat HIV and AIDS, hence, new compounds are required. We report crystal structures of wild-type and mutant HIV-1 RT with bound non-nucleoside (NNRTI) GW420867X, aimed at investigating the basis for its high potency and improved drug resistance profile compared to the first-generation drug nevirapine. GW420867X occupies a smaller volume than many NNRTIs, yet accesses key regions of the binding pocket. GW420867X has few contacts with Tyr188, hence, explaining the small effect of mutating this residue on inhibitor-binding potency. In a mutated NNRTI pocket, GW420867X either remains in a similar position compared to wild-type (RT(Leu100Ile) and RT(Tyr188Cys)) or rearranges within the pocket (RT(Lys101Glu)). For RT(Leu100Ile), GW420867X does not shift position, in spite of forming different side-chain contacts. The small bulk of GW420867X allows adaptation to a mutated NNRTI binding site by repositioning or readjustment of side-chain contacts with only small reductions in binding affinity.

Hemolytic Potential of Tafenoquine in Female Volunteers Heterozygous for Glucose-6-Phosphate Dehydrogenase (G6PD) Deficiency (G6PD Mahidol Variant) versus G6PD-Normal Volunteers.

Tafenoquine is an 8-aminoquinoline under investigation for the prevention of relapse in Plasmodium vivax malaria. This open-label, dose-escalation study assessed quantitatively the hemolytic risk with tafenoquine in female healthy volunteers heterozygous for the Mahidol487A glucose-6-phosphate dehydrogenase (G6PD)-deficient variant versus G6PD-normal females, and with reference to primaquine. Six G6PD-heterozygous subjects (G6PD enzyme activity 40-60% of normal) and six G6PD-normal subjects per treatment group received single-dose tafenoquine (100, 200, or 300 mg) or primaquine (15 mg × 14 days). All participants had pretreatment hemoglobin levels ≥ 12.0 g/dL. Tafenoquine dose escalation stopped when hemoglobin decreased by ≥ 2.5 g/dL (or hematocrit decline ≥ 7.5%) versus pretreatment values in ≥ 3/6 subjects. A dose-response was evident in G6PD-heterozygous subjects (N = 15) receiving tafenoquine for the maximum decrease in hemoglobin versus pretreatment values. Hemoglobin declines were similar for tafenoquine 300 mg (-2.65 to -2.95 g/dL [N = 3]) and primaquine (-1.25 to -3.0 g/dL [N = 5]). Two further cohorts of G6PD-heterozygous subjects with G6PD enzyme levels 61-80% (N = 2) and > 80% (N = 5) of the site median normal received tafenoquine 200 mg; hemolysis was less pronounced at higher G6PD enzyme activities. Tafenoquine hemolytic potential was dose dependent, and hemolysis was greater in G6PD-heterozygous females with lower G6PD enzyme activity levels. Single-dose tafenoquine 300 mg did not appear to increase the severity of hemolysis versus primaquine 15 mg × 14 days.

Inclusion of full length human immunodeficiency virus type 1 (HIV-1) gag sequences in viral recombinants applied to drug susceptibility phenotyping.

Drug susceptibility phenotyping of recombinant clinical human immunodeficiency virus type 1 (HIV-1) isolates has been used widely to quantitatively assess viral resistance to antiretroviral agents. A novel method is described for HIV-1 drug susceptibility phenotyping. Recombinant virus that contains the entire HIV-1 Gag, protease (PR) and reverse transcriptase (RT) coding regions is generated from plasma of HIV-1 infected subjects, thus allowing the in vitro investigation of effects caused by all protein-coding sequence elements upstream from the drug targets on: (i) drug susceptibility; and (ii) viral replicative capacity. Mutations known to cause retarded viral growth kinetics (RT M184V and PR I50V) were introduced and analyzed in parallel using both the new Five Prime HIV assay (FPH) and a standard recombinant virus assay (RVA). The M184V and I50V mutants produced up to 4.8- and 5.9-fold higher p24 antigen levels, respectively, with the FPH when compared to the cultures containing RVA-derived viruses. The reduced number of homologous recombination events necessary to generate replication-competent provirus with the FPH is the most likely explanation for these findings. Long range RT-PCR products were generated from plasma of HIV-1 infected subjects and HIV-1 LTR sequences were added using one-step PCR-mediated recombination. FPH-recombinants generated from two patients with previous HIV PR and RT inhibitor therapy showed lower drug susceptibilities than mutants established in parallel by RVA, and relative in vitro replication of the FPH recombinant derived from one of these subjects was enhanced compared to the corresponding RVA mutant. Although there were changes from the HIV-1 subtype B consensus sequence in amino acids flanking the Gag p17/p24, p24/p2 or p2/p7 PR cleavage sites, none were within the 10 amino acids immediately flanking the sites. These data suggest that determinants of drug susceptibility may be encoded in Gag upstream of the p7/p1 and p1/p6 regions, and that some phenotyping assays may therefore be underdetermining the reduction of drug susceptibility in some viral isolates.

Changes in human immunodeficiency virus type 1 Gag at positions L449 and P453 are linked to I50V protease mutants in vivo and cause reduction of sensitivity to amprenavir and improved viral fitness in vitro.

Human immunodeficiency virus type 1 (HIV-1) Gag protease cleavage sites (CS) undergo sequence changes during the development of resistance to several protease inhibitors (PIs). We have analyzed the association of sequence variation at the p7/p1 and p1/p6 CS in conjunction with amprenavir (APV)-specific protease mutations following PI combination therapy with APV. Querying a central resistance data repository resulted in the detection of significant associations (P < 0.001) between the presence of APV protease signature mutations and Gag L449F (p1/p6 LP1'F) and P453L (p1/p6 PP5'L) CS changes. In population-based sequence analyses the I50V mutant was invariably linked to either L449F or P453L. Clonal analysis revealed that both CS mutations were never present in the same genome. Sequential plasma samples from one patient revealed a transition from I50V M46L P453L viruses at early time points to I50V M46I L449F viruses in later samples. Various combinations of the protease and Gag mutations were introduced into the HXB2 laboratory strain of HIV-1. In both single- and multiple-cycle assay systems and in the context of I50V, the L449F and P453L changes consistently increased the 50% inhibitory concentration of APV, while the CS changes alone had no measurable effect on inhibitor sensitivity. The decreased in vitro fitness of the I50V mutant was only partially improved by addition of either CS change (I50V M46I L449F mutant replicative capacity approximately 16% of that of wild-type virus). Western blot analysis of Pr55 Gag precursor cleavage products from infected-cell cultures indicated accumulation of uncleaved Gag p1-p6 in all I50V viruses without coexisting CS changes. Purified I50V protease catalyzed cleavage of decapeptides incorporating the L449F or P453L change 10-fold and 22-fold more efficiently than cleavage of the wild-type substrate, respectively. HIV-1 protease CS changes are selected during PI therapy and can have effects on both viral fitness and phenotypic resistance to PIs.