Case report: recurrence of Plasmodium vivax malaria due to defective cytochrome P450 2D6 function in Pos Lenjang, Pahang, Malaysia

Cytochrome P450 2D6 (CYP2D6) and glucose-6-phosphate dehydrogenase (G6PD) genetic variations in Thai vivax malaria patients: Implications for 8-aminoquinoline radical cure

BACKGROUND

Primaquine and tafenoquine are the only licensed drugs that effectively kill the hypnozoite stage and are used to prevent Plasmodium vivax malaria relapse. However, both primaquine and tafenoquine can cause acute hemolysis in glucose-6-phosphate dehydrogenase (G6PD)-deficient people with varying degrees of severity depending on G6PD variants. Additionally, primaquine efficacy against malaria parasites was decreased in individuals with impaired cytochrome P450 2D6 (CYP2D6) activity due to genetic polymorphisms. This study aimed to characterize G6PD and CYP2D6 genetic variations in vivax malaria patients from Yala province, a malaria-endemic area along the Thai-Malaysian border, and determine the biochemical properties of identified G6PD variants.

METHODOLOGY/PRINCIPLE FINDINGS

Multiplexed high-resolution melting assay and DNA sequencing detected five G6PD variants, including G6PD Kaiping, G6PD Vanua Lava, G6PD Coimbra, G6PD Mahidol, and G6PD Kerala-Kalyan. Biochemical and structural characterization revealed that G6PD Coimbra markedly reduced catalytic activity and structural stability, indicating a high susceptibility to drug-induced hemolysis. While Kerala-Kalyan had minor effects, it is possible to develop mild adverse effects when receiving radical treatment. CYP2D6 genotyping was performed using long-range PCR and DNA sequencing, and the phenotypes were predicted using the combination of allelic variants. Decreased and no-function alleles were detected at frequencies of 53.4% and 14.2%, respectively. The most common alleles were CYP2D6*36+*10 (25.6%), *10 (23.9%), and *1 (22.2%). Additionally, 51.1% of the intermediate metabolizers showed CYP2D6*10/*36+*10 as the predominant genotype (15.9%).

CONCLUSIONS/SIGNIFICANCE

Our findings provide insights about genetic variations of G6PD and CYP2D6 in 88 vivax malaria patients from Yala, which may influence the safety and effectiveness of radical treatment. Optimization of 8-aminoquinoline administration may be required for safe and effective treatment in the studied population, which could be a significant challenge in achieving the goal of eliminating malaria.

Association between CYP2D6 phenotype and recurrence of Plasmodium vivax infection in south Korean patients

Background

Primaquine is activated by CYP2D6 in the hepatocytes. In Korea, primaquine is the only hypnozoitocidal agent used for patients with vivax malaria. Thus, patients with poor CYP2D6 activity could have an increased risk of primaquine failure and subsequent relapse. The study sought to identify the association between CYP2D6 phenotype and recurrence of malaria in Korean patients.

Methods

A total of 102 patients with vivax malaria were prospectively enrolled from eight institutions in Korea. An additional 38 blood samples from patients with recurred vivax malaria were provided by the Korea Disease Control and Prevention Agency. Malaria recurrence was defined as more than one episode of vivax malaria in the same or consecutive years. CYP2D6 star alleles, phenotypes, and activity scores were examined.

Results

Genotyping for CYP2D6 was successful in 101 of the prospectively enrolled patients and 38 samples from the Korea Disease Control and Prevention Agency, of which 91 were included in the no-recurrence group and 48 were included in the recurrence group. Reduced CYP2D6 activity (intermediate metabolizer) phenotype was more common in the recurrence group than in the no-recurrence group (OR, 2.33 (95% CI, 1.14–4.77); p = 0.02). Patients with lower CYP2D6 activity had a higher probability of recurrence (p = 0.029).

Conclusion

This study suggests that CYP2D6 polymorphism may affect primaquine efficacy and thus Plasmodium vivax recurrence in Korea.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12936-022-04311-6.

Four Times of Relapse of Plasmodium vivax Malaria Despite Primaquine Treatment in a Patient with Impaired Cytochrome P450 2D6 Function

Plasmodium vivax exhibits dormant liver-stage parasites, called hypnozoites, which can cause relapse of malaria. The only drug currently used for eliminating hypnozoites is primaquine. The antimalarial properties of primaquine are dependent on the production of oxidized metabolites by the cytochrome P450 isoenzyme 2D6 (CYP2D6). Reduced primaquine metabolism may be related to P. vivax relapses. We describe a case of 4 episodes of recurrence of vivax malaria in a patient with decreased CYP2D6 function. The patient was 52-year-old male with body weight of 52 kg. He received total gastrectomy and splenectomy 7 months before the first episode and was under chemotherapy for the gastric cancer. The first episode occurred in March 2019 and each episode had intervals of 34, 41, and 97 days, respectively. At the first and second episodes, primaquine was administered as 15 mg for 14 days. The primaquine dose was increased with 30 mg for 14 days at the third and fourth episodes. Seven gene sequences of P. vivax were analyzed and revealed totally identical for all the 4 samples. The CYP2D6 genotype was analyzed and intermediate metabolizer phenotype with decreased function was identified.

Impact of CYP2D6 Genetic Variation on Radical Cure of Plasmodium vivax Malaria

Plasmodium vivax (P. vivax) is the most widespread human malaria parasite, with 2.5 billion people at risk of infection worldwide. P. vivax forms liver hypnozoites, which trigger further symptomatic episodes (relapses) weeks or months after the initial episode. Radical cure of vivax malaria requires hypnozoitocide therapy to prevent relapses. The two US Food and Drug Administration (FDA)-approved hypnozoiticides for human use, primaquine, and tafenoquine, are pro-drugs, that require in vivo conversion into metabolites with redox activity. This mini-review focuses on the association between CYP2D6-mediated hydroxylation and hypnozoitocide efficacy of primaquine and tafenoquine. Studies in murine models show that the antimalarial activity of primaquine and tafenoquine is abolished by CYP2D knock-out and partially restored by knock-in of humanized CYP2D6. Human studies explored the impact of CYP2D6 genetic variation and genotype-inferred CYP2D6 phenotype on anti-relapse efficacy. Most, but not all, studies with primaquine report higher rates of relapse in patients with decreased CYP2D6 activity (activity scores (AS) ≤ 1) compared to normal activity (AS ≥ 1.5). Potential factors for discordance among studies include risk of reinfection in endemic areas, adherence to primaquine-treatment, assignment of CYP2D6 phenotypes based on CYP2D6 polymorphism and choice of AS values for dichotomizing the study cohorts. Tafenoquine anti-relapse efficacy did not differ between patients with AS < 1 vs. AS ≥ 1.5 in 2 studies. Absence/small number of poor CYP2D6 metabolizers in AS ≤ 1 groups, combined with lesser dependence of tafenoquine on CYP2D6-mediated conversion into active redox metabolites may account for this result. Additional tafenoquine studies with larger representation of poor CYP2D6 metabolizers are warranted.

CYP2D6 Genetic Variation and Its Implication for Vivax Malaria Treatment in Madagascar

Plasmodium vivax is one of the five human malaria parasite species, which has a wide geographical distribution and can cause severe disease and fatal outcomes. It has the ability to relapse from dormant liver stages (hypnozoites), weeks to months after clearance of the acute blood-stage infection. An 8-aminoquinoline drug primaquine (PQ) can clear the hypnozoites, and thus can be used as an anti-relapse therapeutic agent. Recently, a number of studies have found that its efficacy is compromised by polymorphisms in the cytochrome P450 2D6 (CYP2D6) gene; decreased or absence of CYP2D6 activity contributes to PQ therapeutic failure. The present study sought to characterize CYP2D6 genetic variation in Madagascar, where populations originated from admixture between Asian and African populations, vivax malaria is endemic, and PQ can be deployed soon to achieve national malaria elimination. In a total of 211 samples collected from two health districts, CYP2D6 decreased function alleles CYP2D6*10, *17, *29, *36+*10, and *41 were observed at frequencies of 3.55-17.06%. In addition, nonfunctional alleles were observed, the most common of which were CYP2D6*4 (2.13%), *5 (1.66%), and the *4x2 gene duplication (1.42%). Given these frequencies, 34.6% of the individuals were predicted to be intermediate metabolizers (IM) with an enzyme activity score (AS) ≤ 1.0; both the IM phenotype and AS ≤ 1.0 have been found to be associated with PQ therapeutic failure. Furthermore, the allele and genotype frequency distributions add to the archaeological and genomic evidence of Malagasy populations constituting a unique, Asian-African admixed origin. The results from this exploratory study provide fresh insights about genomic characteristics that could affect the metabolism of PQ into its active state, and may enable optimization of PQ treatment across human genetic diversity, which is critical for achieving P. vivax elimination.