The metabolism of primaquine to its active metabolite is dependent on CYP 2D6

Brandon S Pybus,Christian Ockenhouse,Qigui Li,Sean R Marcsisin,Gregory Deye,Jason Bennett,Diana Caridha,Larry A Walker,Colin Ohrt,Qiang Zeng,Xiannu Jin,Gregory A Reichard,Jason C Sousa,Victor Melendez

doi:10.1186/1475-2875-12-212

Brandon S Pybus, Christian Ockenhouse + Show 12 more

Open Access

https://doi.org/10.1186/1475-2875-12-212

Copy DOI

Abstract

BackgroundThe efficacy of the 8-aminoquinoline (8AQ) drug primaquine (PQ) has been historically linked to CYP-mediated metabolism. Although to date no clear evidence exists in the literature that unambiguously assigns the metabolic pathway or specific metabolites necessary for activity, recent literature suggests a role for CYP 2D6 in the generation of redox active metabolites.MethodsIn the present study, the specific CYP 2D6 inhibitor paroxetine was used to assess its effects on the production of specific phenolic metabolites thought to be involved in PQ efficacy. Further, PQ causal prophylactic (developing liver stage) efficacy against Plasmodium berghei in CYP 2D knockout mice was assessed in comparison with a normal C57 background and with humanized CYP 2D6 mice to determine the direct effects of CYP 2D6 metabolism on PQ activity.ResultsPQ exhibited no activity at 20 or 40 mg/kg in CYP 2D knockout mice, compared to 5/5 cures in normal mice at 20 mg/kg. The activity against developing liver stages was partially restored in humanized CYP 2D6 mice.ConclusionsThese results unambiguously demonstrate that metabolism of PQ by CYP 2D6 is essential for anti-malarial causal prophylaxis efficacy.

Highlights

The efficacy of the 8-aminoquinoline (8AQ) drug primaquine (PQ) has been historically linked to Cytochrome P450 (CYP)-mediated metabolism
If PQ efficacy is solely dependent upon CYP 2D6 metabolism, this could present a serious problem for eradication efforts centred around PQ use, as many populations throughout the world have high prevalence of allelic frequency for poor and intermediate activity CYP 2D6 [10]
CYP2D6-mediated hydroxylation of primaquine In order to understand the role of CYP 2D6 in the biotransformation and bio-activation of primaquine, several experiments were conducted with primaquine and recombinant CYP2D6

Summary

Methods

Chemicals used Chemicals used were: primaquine (Sigma, St Louis, MO, USA, #160393), paroxetine (Sigma, #P9623), nicotinamide adenine dinucleotide phosphate, oxidized form (NADP) (Sigma, # 077 K7000), acetonitrile (Fisher Scientific, Waltham, MA, USA, #972970), glucose-6phosphate (G6P) (Sigma, # 046 K3779), glucose-6phosphate dehydrogenase (G6PD) (Sigma, # 068 K3795), and magnesium chloride (MgCl2) (Sigma, #102 K0154). IVIS study for C57BL/6 and knockout mice PQ was administered orally on days −1, 0, and 1 with respect to sporozoite inoculation. At 24, 48, and 72 hours post-sporozoite infection, all inoculated mice were tested using the Caliper Life Sciences (Hopkinton, MA, USA) IVIS Spectrum instrument. The suspension solution of oral agents were prepared in 0.5% (w/v) hydroxyethyl cellulose and 0.2% (0.5% HECT, v/v) Tween-80 in distilled water, using homogenizer (PRO Scientific Inc, Monroe, CT, USA) with 10 mm open slotted generator to homogenize drug powder mixture at 20,000-22,000 rpm for 5 min in ice bath. D-Luciferin potassium salt, (Xenogen, California and Goldbio, St Louis, MO, USA), the luciferase substrate, was intraperitoneally inoculated into mice at a concentration of 200 mg/kg 15 min before bioluminescence analysis.

Background

Results

72 Hrs min max Luminescence