# Nqo2 in Primaquine-Induced Hemolysis of G6PD-deficient RBCs

> **NIH NIH R01** · UNIVERSITY OF VIRGINIA · 2024 · $746,958

## Abstract

Primaquine and tafenoquine are the only approved drugs that can eliminate plasmodium vivax (P. vivax) infection
from its liver phase (i.e. radical cure). However, both primaquine and tafenoquine are contraindicated in patients
with a glucose-6-phosophate dehydrogenase deficiency (G6PDd) because they can cause potentially life-
threatening hemolytic anemia. Approximately half a billion humans have some form of G6PDd and they are
concentrated in malaria endemic regions. As a result, there is no cure available for the approximately 1 million
G6PDd humans infected with P. vivax. NAPDH (and to a lesser extent NADH) fuel anti-oxidation pathways as
electron donors. Primaquine metabolites (PMs) generate toxic reactive oxygen species (ROS) by a redox cycling
reaction wherein PMs receives an electron (from NADPH or NADH) to generate a PM radical, which in turn
donates its electron to oxygen to generate superoxide. The transfer of electrons (from NADPH or NADH) to PMs
requires an enzymatic reductase – however, the reductase has never been identified. Herein we present the
novel finding that the enzymes NQO1 and NQO2 both transfer electrons to PMs and drive superoxide generation.
To the best of our knowledge, this is the first identification of reductases in RBCs that participate in and may be
required for ROS generation by PMs. The data generated thus far are largely in vitro. The next necessary step
is in vivo studies, which are the focus of this grant. NQO1 and NQO2 have widespread effects in multiple organs
and drug metabolism by the liver. Accordingly, to allow testing of hypotheses focused on RBCs, we generated
two novel mouse strains with floxed exons either NQO1 or NQO2 (i.e. conditional knockouts). RBC specific
knockouts will be generated by crossing these animals with erythroid specific CRE transgenic mice. We have
also generated humanized G6PDd mice that undergo primaquine induced hemolysis. Combining these tools,
we propose three hypothesis driven specific aims to investigate the mechanistic roles of NQO1 (Specific Aim
1) or NQO2 (Specific Aim 2) in primaquine induced hemolysis in humanized G6PDd mice. A third specific aim
(Specific Aim 3) investigates joint effects of NQO1 and NQO2, addressing issues of potential redundant
pathways. The proposed aims will use both in vitro and in vivo systems to test the roles of NQO1 or NQO2 in
driving PM dependent generation of superoxide, cellular and biochemical damage, and in vivo hemolysis of
G6PDd RBCs. The studies are designed to drive both basic discovery and also translational approaches, as
NQO1 and/or NQO2 inhibitors may decrease primaquine induced hemolysis in G6PDd RBCs. Further
translation is found in that NQO2 is unique in its use of dihydronicotinamide riboside (NRH) as an electron donor.
NRH is part of the vitamin B3 complex and is largely derived from diet. It is well known that within patients with
the same G6PD variant, some patients briskly hemolyze when taking primaquine while others do no...

## Key facts

- **NIH application ID:** 10852672
- **Project number:** 1R01HL172874-01
- **Recipient organization:** UNIVERSITY OF VIRGINIA
- **Principal Investigator:** JAMES C. ZIMRING
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $746,958
- **Award type:** 1
- **Project period:** 2024-05-15 → 2028-04-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10852672

## Citation

> US National Institutes of Health, RePORTER application 10852672, Nqo2 in Primaquine-Induced Hemolysis of G6PD-deficient RBCs (1R01HL172874-01). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/10852672. Licensed CC0.

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