DPYD*7 as a Predictor of Severe Fluoropyrimidine-Related Adverse Events

Can we identify patients carrying targeted deleterious DPYD variants with plasma uracil and dihydrouracil? A GPCO-RNPGx retrospective analysis

OBJECTIVES

Dihydropyrimidine dehydrogenase (DPD) deficiency is the main cause of severe fluoropyrimidine-related toxicities. The best strategy for identifying DPD-deficient patients is still not defined. The EMA recommends targeted DPYD genotyping or uracilemia (U) testing. We analyzed the concordance between both approaches.

METHODS

This study included 19,376 consecutive French patients with pre-treatment plasma U, UH2 and targeted DPYD genotyping (*2A, *13, D949V, *7) analyzed at Eurofins Biomnis (2015-2022).

RESULTS

Mean U was 9.9 ± 10.1 ng/mL (median 8.7, range 1.6-856). According to French recommendations, 7.3 % of patients were partially deficient (U 16-150 ng/mL) and 0.02 % completely deficient (U≥150 ng/mL). DPYD variant frequencies were *2A: 0.83 %, *13: 0.17 %, D949V: 1.16 %, *7: 0.05 % (2 homozygous patients with U at 22 and 856 ng/mL). Variant carriers exhibited higher U (median 13.8 vs. 8.6 ng/mL), and lower UH2/U (median 7.2 vs. 11.8) and UH2/U2 (median 0.54 vs. 1.37) relative to wild-type patients (p<0.00001). Sixty-six% of variant carriers exhibited uracilemia <16 ng/mL, challenging correct identification of DPD deficiency based on U. The sensitivity (% patients with a deficient phenotype among variant carriers) of U threshold at 16 ng/mL was 34 %. The best discriminant marker for identifying variant carriers was UH2/U2. UH2/U2<0.942 (29.7 % of patients) showed enhanced sensitivity (81 %) in identifying deleterious genotypes across different variants compared to 16 ng/mL U.

CONCLUSIONS

These results reaffirm the poor concordance between DPD phenotyping and genotyping, suggesting that both approaches may be complementary and that targeted DPYD genotyping is not sufficiently reliable to identify all patients with complete deficiency.

Review - The impact of pharmacogenetics on the outcome of immune checkpoint inhibitors

The development of immune checkpoint inhibitors (ICIs) has a tremendous effect on the treatment options for multiple types of cancer. Nonetheless, there is a large interpatient variability in response, survival, and the development of immune-related adverse events (irAEs). Pharmacogenetics is the general term for germline genetic variations, which may cause the observed interindividual differences in response or toxicity to treatment. These genetic variations can either be single-nucleotide polymorphisms (SNPs) or structural variants, such as gene deletions, amplifications or rearrangements. For ICIs, pharmacogenetic variation in the human leukocyte antigen molecules has also been studied with regard to treatment outcome. This review presents a summary of the literature regarding the pharmacogenetics of ICI treatment, discusses the most important known genetic variations and offers recommendations on the application of pharmacogenetics for ICI treatment.

The Evaluation of Dihydropyrimidine Dehydrogenase Enzyme Level in the Serum of Colorectal Cancer Iraqi Males on Fluoropyrimidine-Based Chemotherapy (Capecitabine)

The cornerstone of systemic chemotherapy for colorectal cancer (CRC) revolves around fluoropyrimidines. This class encompasses 5-fluorouracil (5-FU), which is administered intravenously, along with its oral prodrug counterpart, capecitabine. Central to the metabolism of both 5-FU and capecitabine is the pivotal enzyme dihydropyrimidine dehydrogenase (DPD). Operating at the rate-limiting juncture, DPD assumes a critical role. Notably, a deficiency in DPD significantly elevates the risk quotient for encountering unfavorable outcomes linked to the administration of fluoropyrimidines. This study seeks to assess the significance of DPD enzyme levels in the serum of Iraqi colorectal cancer male patients undergoing fluoropyrimidine-based chemotherapy, specifically with capecitabine. It adopts a case-control design and comprises 80 male participants. Those males are divided into two distinct groups. Group 1 comprises 45 male patients diagnosed with CRC who have experienced relapse subsequent to undergoing chemotherapy based on fluoropyrimidine (capecitabine). Their ages span from 41 to 71 years, and they were treated at the Misan Health Directorate/Misan Center for Tumor Treatment. Group 2 encompasses 35 male patients diagnosed with CRC who underwent fluoropyrimidine-based chemotherapy (capecitabine) without encountering relapse. Their ages range from 40 to 57 years. All participants were provided with comprehensive information regarding the research, and data collection occurred through a structured questionnaire. Subsequent to capecitabine-based treatment, serum samples were collected from CRC patients (stage III). The findings from this research indicate a notable elevation in DPD enzyme activity. Furthermore, a significant reduction in enzyme activity was observed among patients who experienced relapse, in contrast to those who remained non-relapsed. The results indicate that individuals with an insufficiency in DPD are notably more vulnerable to experiencing severe and potentially life-threatening side effects upon exposure to the commonly utilized chemotherapy drug, 5-FU.