Single Low-dose Primaquine Efficacy and Safety.

Background: The World Health Organization has recommended addition of a 0.25 mg/kg single-dose primaquine (PQ) to standard artemisinin-based combination therapy (ACT) for elimination of malaria in low transmission-settings and for containment in areas threatened by artemisinin resistance. However, PQ metabolism is dependent on a highly polymorphic cytochrome P450 (CYP) 2D6 isoenzyme which probably compromises the drugs' safety and efficacy, particularly in individuals with reduced isoenzyme activity. This trial therefore, aims to assess the safety and efficacy of 0.25 mg/kg single-dose PQ when added to standard artemether-lumefantrine regimen for clearance and sterilization of Plasmodium falciparum gametocytes in patients with CYP450 2D6 reduced/null activity as compared to those with normal/increased enzyme activity.

Methods: On hundred and fifty-five children aged between 1 and 10 years and with uncomplicated P. falciparum malaria will be enrolled, treated with standard artemether-lumefantrine regimen plus a 0.25 mg/kg single-dose of PQ and then followed up on days 0, 1, 2, 3, 7, 14, 21 and 28 for clinical and laboratory assessment. Primaquine will be administered together with the first dose of artemether-lumefantrine. Safety assessment will be performed using the Primaquine Roll Out Monitoring Pharmacovigilance Tool (PROMPT). Gametocytes will be detected and quantified by microscopy and Pfs25 mRNA quantitative nucleic acid sequence based amplification (QT-NASBA) on days 0 and 7. For a subset of 100 participants, post-treatment infectiousness will be assessed by mosquito feeding assays on day 7. The CYP2D6 status will be determined using a polymerase chain reaction (PCR) followed by a restriction fragment length polymorphism (RFLP). The primary outcome will be the safety of single low-dose primaquine in patients with CYP2D6 reduced/null compared to those with normal/increased activity.

Expected outcomes: The findings will provide the much-needed information on the safety and efficacy of single low-dose primaquine for clearance and sterilization of P. falciparum gametocytes in individuals with reduced/null compared to those with normal/increased CYP450 2D6 isoenzyme activity prior to the implementation of the treatment policy particularly in Africa.