Disclaimer: Early release articles are not considered as final versions. Any changes will be reflected in the online version in the month the article is officially released.
Volume 31, Number 9—September 2025
Dispatch
CYP2D6 Genotype and Primaquine Treatment in Patients with Malaria, Venezuela
Suggested citation for this article
Abstract
We determined CYP2D6*4 and CYP2D6* genotypes and metabolizer phenotypes in 96 patients with suspected malaria in Venezuela and found intermediate or poor metabolizer phenotypes in ≈25% of cases. Nine of 44 malaria patients had Plasmodium vivax recurrence. Public health authorities should evaluate the benefits of increasing total doses of primaquine for treatment.
Malaria is prevalent in different tropical and subtropical regions, including those in Africa, Asia, and Latin America (1). In Latin America, Brazil, Colombia, and Venezuela account for 76.8% of all reported cases. Most (72.1% in 2023) cases in that region are attributed to Plasmodium vivax (1). Sucre State is a malaria-endemic region in Venezuela, where P. vivax is almost the only species (2). Treatment of P. vivax malaria involves a combination therapy of chloroquine and primaquine, a prodrug that requires metabolic activation to elicit its antimalarial effect against hypnozoites (3).
Activation of primaquine is catalyzed by the metabolic enzyme cytochrome P450 2D6 (CYP2D6), which belongs to the CYP450 superfamily, a group of enzymes responsible for metabolism of many commonly prescribed drugs (4). The CYP2D6 gene is highly polymorphic and has >150 different alleles (4), encoding CYP2D6 isoforms with normal, decreased, increased, or no activity. In Venezuela, several CYP2D6 genotypes exhibiting the most prevalent null allele, CYP2D6*4 (1846 G>A, rs3892097), and the less frequent CYP2D6*6 allele (1707delT, rs5030655) have been documented (5,6). For instance, the CYP2D6*4 allele was observed at a frequency of 14% in an urban admixed population from Aragua, a nonmalaria state, and in Amerindian populations at frequencies of 4.2%–42.5% from Zulia (nonmalaria state) and 1.7%–5.45% from Bolivar (malaria state). The CYP2D6*6 allele was observed at frequencies ranging from 0.3% to 1.2% in 2 urban admixed populations (5,6).
Malaria patients’ response to primaquine treatment is contingent on the level of CYP2D6 activity. In cases where CYP2D6 activity is low, probability of treatment failure is higher (4). Because CYP2D6 is necessary for primaquine metabolism, we determined the genotype of the most common CYP2D6*4 variant and a less common CYP2D6*6 variant with null activity and predicted the metabolizer phenotype in a sample of Mestizo persons with suspected P. vivax malaria from malaria-endemic Sucre state, Venezuela. We also evaluated the response to the standard treatment with primaquine.
We conducted this study by using a sample of 96 patients (60 men and 36 women) exhibiting malaria symptoms. The patients were unrelated to each other and >18 years of age. We recruited the patients in December 2022 from 4 health centers in the city of Cumaná, municipality of Sucre, Sucre state, Venezuela (Figure). We collected peripheral blood samples from the patients after they provided informed consent as approved by the Instituto de Investigaciones Biomédicas, Universidad de Carabobo Bioethics Committee (approval no. CBIIB-UC/2022-2).
We performed microscopic malaria diagnosis and validated positive results by using PCR (3). We extracted genomic DNA as previously described (7) and conducted genotyping in accordance with previously outlined methods (5). If we observed no nucleotide change in the 2 allelic variants analyzed, we designated the allele as CYP2D6*1.
We predicted metabolizer phenotype by using the activity score (AS) system (8). In brief, we assigned values to the identified alleles ranging from 0 for no-function alleles (*4, *6) to 2 for normal-function alleles (*1). The AS value of a given genotype is the sum of the assigned values for each allele. We designated patients with AS of 0 as poor metabolizers, AS of 1 as intermediate metabolizers, and AS of 2 as normal metabolizers (8,9).
Among 96 participants, 44 (45.83%) were malaria positive. As expected, P. vivax malaria was predominant; 43 (97.72%) of the 44 malaria-positive patients were infected with P. vivax, and 1 (2.27%) was infected with P. falciparum. Of the 44 malaria-positive patients, 30 (68.18%) were men and 14 (31.81%) were women, which we anticipated: men have a higher malaria risk than women because their occupations are more likely to involve outdoor work, like fishing. The patients received standard oral primaquine treatment (0.25 mg/kg/d for 14 days) (3). The day after treatment started, we evaluated patients for malaria recurrence, which was characterized by fever and parasitemia (10).
We compared samples from the 52 malaria-negative participants and the 44 malaria-positive participants and found similar genotype profiles. CYP2D6*1*1 was the predominant genotype, which indicated a normal metabolizer phenotype. We saw a percentage of 75% in the 96 patients with the CYP2D6*1*1 genotype across both nonmalaria and malaria patients (Table). The other 25% of analyzed genotypes manifested as intermediate or poor metabolizer phenotypes, among which the CYP2D6*1*4 genotype showed the highest frequency and had an average of 17.75% across both groups. That frequency is substantially higher than the low frequency (2.37%) of that genotype identified within the population identified in Madagascar (11). However, in 5 areas of Brazil, the CYP2D6*1*4 genotype exhibited a high frequency (35%–50%) (12). That variation can be attributed to the different ethnic origins of the genotype, which differ across regions. The ancestors of the population of Madagascar are believed to be from Asia and Africa, whereas the ancestors of the highly heterogeneous populations from Venezuela and Brazil are thought to be from Spain and Portugal. In addition, the CYP2D6*4 genotype frequency within the group from Europe is high (13). The metabolizer phenotype profile showed notable similarity across both groups; 75% of patients exhibited a normal metabolizer profile, 20.8% showed an intermediate metabolizer profile, and 4.19% displayed a poor metabolizer profile. Those values agree with values observed in ethnicity from Europe, thereby providing further substantiation for the initial assertion (13).
P. vivax recurrence was observed in 9 (20.5%) patients (6 men and 3 women); 7 exhibited an intermediate metabolizer phenotype, and 2 exhibited a poor metabolizer phenotype. That phenomenon might be attributed to a substantial correlation between the CYP2D6 alleles with diminished activity, such as CYP2D6*4 and *6, and the occurrence of primaquine therapeutic failure in patients infected with P. vivax (4). High rates of relapses have already been reported in Venezuela (14; J. Huber et al., unpub. data, https://www.medrxiv.org/content/medrxiv/early/2022/05/12/2022.04.19.22274042.full). The recurrence of P. vivax shown in this study might be preventable by administering a higher dose (7.0 mg/kg) of primaquine instead of the conventional dose (3.5 mg/kg) (10).
The first limitation of this study is the low number of patients; thus, our results might not be representative of all malaria-infected populations. Second, we only conducted patient monitoring on day 28 and thus only determined the clinical and parasitologic response and not the absence of P. vivax recurrence, which requires meticulous monitoring over a period of ≈6 months (9); thus, we might have missed recurrence that occurred after 28 days.
We estimated that ≈25% of malaria patients had nonfunctional alleles that would impair efficacy of primaquine. The corresponding predicted intermediate metabolizer phenotype was 20.8% and the poor metabolizer phenotype was 4.19% in a sample of malaria patients and nonmalaria patients susceptible to infection with P. vivax in Sucre, a malaria-endemic state of Venezuela. Those data are consistent with the 20.5% recurrence rate observed in P. vivax patients. To effectively treat malaria in the region, we recommend that public health authorities evaluate the potential benefits of increasing total doses of primaquine (7.0 mg/kg; 0.5 mg/kg/d) over a period of 14 days as an alternative to the current treatment regimen.
Mr. Pacheco is a PhD student at Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional. His research focuses on tropical infectious diseases and facilitating appropriate control solutions for policy makers.
Acknowledgments
We thank all the patients who participated in the study; the staff of Ambulatorio La Llanada, Ambulatorio Cascajal, Hospital Julio Rodríguez, and Centro de Diagnóstico Integral El Peñón of the state of Sucre, Venezuela, who provided technical assistance to the authors in the collection of samples; and Juan Ernesto Ludert for support in performing some of the experiments in his laboratory at Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional. We used DeepL Write (https://www.deepl.com/es/write) to enhance the quality of the writing style.
This work was supported by Instituto de Investigaciones Biomédicas, Universidad de Carabobo Venezuela.
References
- World Health Organization. World malaria report 2024 [cited 2025 Feb 8]. https://www.who.int/teams/global-malaria-programme/reports/world-malaria-report-2024
- Wide A, Pabón R, De Abreu N, Bargues MD, Salcedo A, Capaldo J, et al. Prevalence of asymptomatic Plasmodium vivax infections in the north-eastern focus of malaria of Venezuela. Bol Mal Salud Amb. 2016;56:160–71.
- Centers for Disease Control and Prevention. Malaria diagnosis (United States). Treatment of uncomplicated malaria 2024 [cited 2025 Feb 10]. https://www.cdc.gov/malaria/hcp/clinical-guidance/treatment-uncomplicated.html
- Olvany JM, Williams SM, Zimmerman PA. Global perspectives on CYP2D6 associations with primaquine metabolism and Plasmodium vivax radical cure. Front Pharmacol. 2022;13:
752314 . DOIPubMedGoogle Scholar - Flores-Angulo C, Villegas C, Mora Y, Martínez JA, Oropeza T, Moreno N. [Allelic variants of the CYP2D6: *4, *6 and *10 in a sample of resident from the Aragua state, Venezuela] [in Spanish]. Rev Peru Med Exp Salud Publica. 2015;32:746–51. DOIPubMedGoogle Scholar
- Griman P, Moran Y, Valero G, Loreto M, Borjas L, Chiurillo MA. CYP2D6 gene variants in urban/admixed and Amerindian populations of Venezuela: pharmacogenetics and anthropological implications. Ann Hum Biol. 2012;39:137–42. DOIPubMedGoogle Scholar
- Rivero J, Urdaneta L, Zoghbi N, Pernalete M, Rubio-Palis Y, Herrera F. Optimization of extraction procedure for mosquitos DNA suitable for PCR-based techniques. Int J Trop Insect Sci. 2004;24:266–9. DOIGoogle Scholar
- Gaedigk A, Dinh JC, Jeong H, Prasad B, Leeder JS. Ten years’ experience with the CYP2D6 activity score: a perspective on future investigations to improve clinical predictions for precision therapeutics. J Pers Med. 2018;8:15. DOIPubMedGoogle Scholar
- Nofziger C, Turner AJ, Sangkuhl K, Whirl-Carrillo M, Agúndez JAG, Black JL, et al. PharmVar GeneFocus: CYP2D6. Clin Pharmacol Ther. 2020;107:154–70. DOIPubMedGoogle Scholar
- Chamma-Siqueira NN, Negreiros SC, Ballard SB, Farias S, Silva SP, Chenet SM, et al. Higher-dose primaquine to prevent relapse of Plasmodium vivax malaria. N Engl J Med. 2022;386:1244–53. DOIPubMedGoogle Scholar
- Mehlotra RK, Gaedigk A, Howes RE, Rakotomanga TA, Ratsimbasoa AC, Zimmerman PA. CYP2D6 genetic variation and its implication for vivax malaria treatment in Madagascar. Front Pharmacol. 2021;12:
654054 . DOIPubMedGoogle Scholar - Salles PF, Perce-da-Silva DS, Rossi AD, Raposo LR, Ramirez Ramirez AD, Pereira Bastos OM, et al. CYP2D6 allele frequency in five malaria vivax endemic areas from Brazilian Amazon region. Front Pharmacol. 2021;12:
542342 . DOIPubMedGoogle Scholar - Kane M. CYP2D6 overview: allele and phenotype frequencies. In: Pratt VM, Scott SA, Pirmohamed M, Esquivel B, Kattman BL, Malheiro AJ, editors. Medical genetics summaries. Bethesda (MD): National Center for Biotechnology Information; 2012. p. 1–34.
- Sojo-Milano M, Cáceres JL, Pizzo NN, Rojas J, Maldonado A, Rubio-Pulgar N, et al. Malaria recurrent Plasmodium vivax. Municipio Cajigal, Estado Sucre, Venezuela. Rev Biomed. 2008;19:3–15.
Figure
Table
Suggested citation for this article: Pacheco C, Hernández-Acosta A, Pulido N, Ceballos Y, Saavedra D, Gómez C, et al. CYP2D6 genotype and primaquine treatment in patients with suspected malaria, Venezuela. Emerg Infect Dis. 2025 Sep [date cited]. https://doi.org/10.3201/eid3109.250316
Original Publication Date: August 04, 2025
1These authors were co–principal investigators.
Table of Contents – Volume 31, Number 9—September 2025
EID Search Options |
---|
|
|
|
Please use the form below to submit correspondence to the authors or contact them at the following address:
Flor Herrera, Universidad de Carabobo, Urb. San Pablo, Calle Hicelle, No 6, Turmero 2115, Venezuela
Top