Determining a Tolerable Dose of Primaquine in G6PD-deficient Persons Without Malaria in Mali (PQSAFETY)

• Primary outcome: the change in hemoglobin concentration from baseline levels following a single low-dose of primaquine not to exceed 0.75 mg/kg. [ Time Frame: Between day 0 and day 10. ]
  

• To measure the occurrence of adverse events, graded by severity, at each primaquine dose among G6PD deficient men [ Time Frame: Days 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 14, and 28 ]

  Severity:

  1. = mild
  2. = moderate
  3. = severe
  4. = life threatening
  
  
• To measure the occurrence of absolute and fractional change in hemoglobin concentration (g/dL) on day 7 vs. baseline at each primaquine dose among G6PD deficient men, in comparison with G6PD normal men [ Time Frame: Days 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 14, and 28 ]
  
• To measure the occurrence of reticulocytosis (by microscopic quantification of reticulocytes stained with brilliant cresyl blue / 1,000 RBCs) on each day of followup, at each primaquine dose, among G6PD deficient men, in comparison with G6PD normal men [ Time Frame: Days 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 14, and 28 ]
  
• To monitor methemoglobin levels (%) on each day of followup, at each primaquine dose among G6PD deficient men, in comparison with G6PD normal men [ Time Frame: Days 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 14, and 28 ]
  Use of a Masimo Rad-57 pulse oximeter that measures methemoglobin levels non-invasively, based on absorption of light through the fingertip.
  
  
• To determine G6PD enzyme activity (semiquantitative testing, U/g Hb) [ Time Frame: Day 0 ]
  Semiquantitative testing will be performed on frozen blood samples to determine G6PD activity on day of enrolment
  
  
• Area Under Curve (AUC) for primaquine [ Time Frame: Hours 1, 2, 4, 6, 8, and 24 after primaquine administration ]
  Pharmacokinetic analysis of plasma concentration of primaquine at all sampled timepoints
  
  
• Maximal concentration (Cmax) for primaquine [ Time Frame: Hours 1, 2, 4, 6, 8, and 24 after primaquine administration ]
  Pharmacokinetic analysis of plasma concentration of primaquine at all sampled timepoints
  
  
• Area Under Curve (AUC) for carboxyprimaquine [ Time Frame: Hours 1, 2, 4, 6, 8, and 24 after primaquine administration ]
  Pharmacokinetic analysis of plasma concentration of carboxyprimaquine
  
  
• Maximal concentration (Cmax) for carboxyprimaquine [ Time Frame: Hours 1, 2, 4, 6, 8, and 24 after primaquine administration ]
  Pharmacokinetic analysis of plasma concentration of carboxyprimaquine
  
  
• Area Under Curve (AUC) for select minor metabolites of primaquine [ Time Frame: Hours 1, 2, 4, 6, 8, and 24 after primaquine administration ]
  Pharmacokinetic analysis of plasma concentration of metabolites of primaquine, exact metabolites to be determined by ongoing in vivo studies (including 5-hydroxyprimaquine)
  
  
• Maximal concentration (Cmax) for select minor metabolites of primaquine [ Time Frame: Hours 1, 2, 4, 6, 8, and 24 after primaquine administration ]
  Pharmacokinetic analysis of plasma concentration of metabolites of primaquine, exact metabolites to be determined by ongoing in vivo studies (including 5-hydroxyprimaquine)
  
  
• Cytochrome P450 (CYP) 2D6 genotyping [ Time Frame: Day 0 ]
  To determine whether a correlation between CYP 2D6 metabolism (weak metabolizer, intermediate metabolizer, normal metabolizer, ultrarapid metabolizer) and hemolysis exists.
  
  

Purpose: The purpose of this study is to determine the highest tolerable dose of primaquine within 0.75 mg/kg. A tolerable dose is defined as one in which:

• Two or fewer participants (< 30%) experience hemolysis;
• No participant experiences a drug-related serious adverse event; and
• No participant requires a blood transfusion.

Design:

• This is an open-label, phase 2, dose-adjustment study.
• The initial primaquine dose will be 0.40 mg/kg. Subsequent dose groups will be selected depending on the occurrence of adverse events in the previous dose group. Once the highest tolerable dose in G6PD-deficient (G6PDd) individuals is established, a control group of G6PD normal malaria-free men will be enrolled and evaluated under the highest tolerable dose of primaquine.

Study Population:

• Malian men aged 18-50 years without malaria infection.
• The majority of study participants will be G6PDd.

Study Size: This study will enroll 7 participants per dose group. If all dose groups are tested, this study will enroll approximately 28 participants.

Study visit and duration:

• Each participant will be followed for 28 days.
• Participants will be evaluated for hemolysis and adverse events on Days 1-10, 14, and 28 following their assigned primaquine dose.

Primary objective:

To measure the change in hemoglobin among G6PD deficient west-African men following a single low-dose of primaquine not to exceed 0.75 mg/kg.

Secondary objectives:

1. To measure the occurrence of adverse events, graded by severity, at each primaquine dose among G6PD deficient men

2. To measure the occurrence of markers of acute hemolytic anemia (AHA), at each primaquine dose among G6PD deficient men. AHA markers will include:

   • Absolute and fractional change in hemoglobin on day 7 vs. baseline
   • Urine color
   • Reticulocyte count
   • Bilirubin (both total and direct)
   • Methemoglobin concentration
   • Development of physical signs or symptoms of hemolytic anemia
3. To compare the change in hemoglobin, frequency and severity of adverse events, and occurrence of markers of AHA between G6PD deficient and non-deficient participants receiving the highest tolerable primaquine dose
4. To measure G6PD enzyme activity (semiquantitative testing, U / gHb)
5. To measure the pharmacokinetics of primaquine, carboxyprimaquine, and other metabolites according to plasma concentrations.
6. To genotype participant blood samples for cytochrome P450 2D6 (CYP2D6) single nucleotide polymorphisms (SNPs), to determine if potential hemolysis in G6PDd individuals is affected by CYP2D6 metabolizer status (e.g. weak metabolizers and/or intermediate metabolizers)