Pharmacogenetic assessment of tafenoquine efficacy in patients with Plasmodium vivax malaria.

Plasmodium vivax has the largest geographic range of human malaria species and is challenging to manage and eradicate due to its ability to establish a dormant liver stage, the hypnozoite, which can reactivate leading to relapse. Until recently, the only treatment approved to kill hypnozoites was the 8-aminoquinoline, primaquine, requiring daily treatment for 14 days. Tafenoquine, an 8-aminoquinoline single-dose treatment with activity against P. vivax hypnozoites, has recently been approved by the US Food and Drug Administration and Australian Therapeutic Goods Administration for the radical cure of P. vivax malaria in patients 16 years and older. We conducted an exploratory pharmacogenetic analysis (GSK Study 208099) to assess the role of host genome-wide variation on tafenoquine efficacy in patients with P. vivax malaria using data from three GSK clinical trials, GATHER and DETECTIVE Part 1 and Part 2. Recurrence-free efficacy at 6 and 4 months and time to recurrence up to 6 months postdosing were analyzed in 438 P. vivax malaria patients treated with tafenoquine. Among the approximately 10.6 million host genetic variants analyzed, two signals reached genome-wide significance (P value ≤ 5 × 10). rs62103056, and variants in a chromosome 12 intergenic region, were associated with recurrence-free efficacy at 6 and 4 months, respectively. Neither of the signals has an obvious biological rationale and would need replication in an independent population. This is the first genome-wide association study to evaluate genetic influence on response to tafenoquine in P. vivax malaria.

Comparative ophthalmic assessment of patients receiving tafenoquine or chloroquine/primaquine in a randomized clinical trial for Plasmodium vivax malaria radical cure.

PURPOSE: Ophthalmic safety observations are reported from a clinical trial comparing tafenoquine (TQ) efficacy and safety versus sequential chloroquine (CQ)/primaquine (PQ) for acute Plasmodium vivax malaria. METHODS: In an active-control, double-blind study, 70 adult subjects with microscopically confirmed P. vivax malaria were randomized (2:1) to receive 400 mg TQ × 3 days or 1500 mg CQ × 3 days then 15 mg PQ × 14 days. MAIN OUTCOME MEASURES: clinically relevant changes at Day 28 and Day 90 versus baseline in the ocular examination, color vision evaluation, and corneal and retinal digital photography. RESULTS: Post-baseline keratopathy occurred in 14/44 (31.8%) patients with TQ and 0/24 with CQ/PQ (P = 0.002). Mild post-baseline retinal findings were reported in 10/44 (22.7%) patients receiving TQ and 2/24 (8.3%) receiving CQ/PQ (P = 0.15; treatment difference 14.4%, 95% CI - 5.7, 30.8). Masked evaluation of retinal photographs identified a retinal hemorrhage in one TQ patient (Day 90) and a slight increase in atrophy from baseline in one TQ and one CQ/PQ patient. Visual field sensitivity (Humphrey™ 10-2 test) was decreased in 7/44 (15.9%) patients receiving TQ and 3/24 (12.5%) receiving CQ/PQ; all cases were < 5 dB. There were no clinically relevant changes in visual acuity or macular function tests. CONCLUSIONS: There was no evidence of clinically relevant ocular toxicity with either treatment. Mild keratopathy was observed with TQ, without conclusive evidence of early retinal changes. Eye safety monitoring continues in therapeutic studies of low-dose tafenoquine (300 mg single dose). CLINICAL TRIAL REGISTRATION: Clinicaltrials.gov identifier: NCT01290601.

Primaquine administration after falciparum malaria treatment in malaria hypoendemic areas with high incidence of falciparum and vivax mixed infection: pros and cons.

Mixed infections of Plasmodium falciparum and Plasmodium vivax is high (approximately 30%) in some malaria hypoendemic areas where the patients present with P. falciparum malaria diagnosed by microscopy. Conventional treatment of P. falciparum with concurrent chloroquine and 14 days of primaquine for all falciparum malaria patients may be useful in areas where mixed falciparum and vivax infections are high and common and also with mild or moderate G6PD deficiency in the population even with or without subpatent vivax mixed infection. It will be possibly cost-effective to reduce subsequent vivax illness if the patients have mixed vivax infection. Further study to prove this hypothesis may be warranted.

The efficacy and adverse effects of GPO-VIR (stavudine+lamivudine+nevirapine) in treatment-naïve adult HIV patients.

A descriptive, combined retrospective and prospective study was conducted at the Anonymous Clinic, Chon Buri Hospital, Chon Buri Province, Thailand from November 10, 2003 to January 4, 2004. A total of 83 adult HIV-treatment-naïve patients undergoing treatment with GPO-VIR (stavudine, lamivudine, and nevirapine) for at least one year were studied. The objectives of the study were to assess the efficacy of GPO-VIR by evaluating body weight changes, CD4 T-cell count changes, the occurrence of opportunistic infections, and long-term side effects, such as lipodystrophy, during treatment. Of 83 studied patients, approximately half (52.3%) of them had a body weight increase > 10% of pre-treatment body weight after 12 months treatment. After taking GPO-VIR, CD4 T-cell counts increased rapidly, by a median of 78 x 10(6) cells/l during the first three months. 39.5% of the patients attained median CD4 counts > 200 x 10(6) cells/I, and 11.6% achieved > 500 x 10(6) cells/l after 2 years of treatment. The occurrence of opportunistic infections was significantly lower after treatment with GPO-VIR (p = 0.001). Subjective assessment of lipodystrophy by physicians and patients showed that 16.8% had symptoms of lipodystrophy within 2 years of GPO-VIR treatment. There was a significant association between older age group (40-49 years) and occurrence of lipodystrophy (p = 0.043). GPO-VIR is an inexpensive and effective antiretroviral drug regimen for initiating treatment of naïve patients, but careful assessment for lipodystrophy is necessary, especially after one year of treatment.

The epidemiology of patients with severe malaria who died at the Hospital for Tropical Diseases, 1991-2004.

This study is a retrospective case series of the causes of death among patients with severe malaria. Data from the medical records of patients who were admitted to the Intensive Care Unit (ICU) of the Hospital for Tropical Diseases, Mahidol University, Bangkok, Thailand between 1991 and 2004 were analyzed. The overall hospital mortality rate was 0.2% and the ICU mortality rate was 1.8% for patients with malaria. Thirty-five patients died of malaria in the ICU during the study period, while a total of 1,866 patients were treated for malaria in the ICU during the study period. The most common complication of malaria was cerebral malaria (77.1%). The socioeconomic and demographic characteristics of those who died are examined here, as well as the cost of their treatment.