National Prociency Testing Result of CYP2D6*10 Genotyping for Adjuvant Tamoxifen Therapy in China

CYP2D6 gene polymorphism and apatinib affect the metabolic profile of fluvoxamine

This study aimed 1) to investigate the influence of CYP2D6 variants on the catalyzing of fluvoxamine, and 2) to study the interaction between fluvoxamine and apatinib. An enzymatic reaction system was setup and the kinetic profile of CYP2D6 in metabolizing fluvoxamine was determined. In vivo, drug-drug interaction was investigated using Sprague–Dawley (SD) rats. Fluvoxamine was given gavage with or without apatinib. Ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was used to determine the concentrations of fluvoxamine and desmethyl-fluvoxamine. The results demonstrated that the relative clearance rates of CYP2D6.A5V, V104A, D337G, F164L, V342M, R440C and R497C increased significantly compared with CYP2D6.1, ranging from 153.626% ± 6.718% to 394.310% ± 33.268%. The activities of other variants reduced to different extent, or even lost function, but there was no statistical difference. The IC₅₀ of apatinib against fluvoxamine disposition was determined, which is 0.190 μM in RLM and 6.419 μM in HLM, respectively. In vivo, apatinib can enhance the plasma exposure of fluvoxamine remarkably characterized by increased AUC, Tmax and Cmax. Meanwhile, the produce of desmethyl fluvoxamine was dramatically inhibited, both AUC and C_max decreased significantly. Mechanistically, apatinib inhibit the generation of fluvoxamine metabolite with a mixed manner both in RLM and HLM. Furthermore, there were differences in the potency of apatinib in suppressing fluvoxamine metabolism among CYP2D6.1, 2 and 10. In conclusion, CYP2D6 gene polymorphisms and drug-drug interaction can remarkably affect the plasma exposure of fluvoxamine. The present study provides basis data for guiding individual application of fluvoxamine.

Cost-effectiveness Analysis of CYP2D6*10 Pharmacogenetic Testing to Guide the Adjuvant Endocrine Therapy for Postmenopausal Women with Estrogen Receptor Positive Early Breast Cancer in China

BACKGROUND

A CYP2D6 gene polymorphism is related to the effect of tamoxifen treatment in patient with estrogen-receptor positive (ER) positive breast cancer and CYP2D6*10 T/T can lead to a poor prognosis in Asian patients. Although one-off pharmacogenetic testing may optimize adjuvant endocrine therapy, testing prior to tamoxifen initiation incurs additional costs.

AIM

We conducted a study to assess the cost-effectiveness of CYP2D6*10 pharmacogenetic testing to guide the adjuvant endocrine therapy compared with tamoxifen without CYP2D6*10 testing in China.

METHODS

A semi-Markov model was developed to evaluate costs and health outcomes represented as quality adjusted life year (QALY) gained. Input data were obtained from the public literature. The results were expressed as incremental cost per QALY gained. A one-way deterministic sensitivity analysis explored the impact of uncertainty in the model parameters on results, and probabilistic uncertainty was assessed through a Monte Carlo probabilistic sensitivity analysis.

RESULTS

In the base-case analysis, in the CYP2D6*10 testing and alternative adjuvant endocrine therapy group, the incremental total cost was US$17,966.95 and the incremental QALY was 3.582. Thus, the incremental cost-effectiveness ratio was US$5015.693 per QALY gained. Compared with a willingness-to-pay threshold of US$26,508/QALY in China, the CYP2D6*10 testing is the dominant strategy in postmenopausal women with ER-positive breast cancer in China, and the increased cost of genetic testing was completely worthwhile. The sensitivity analyses showed that the model we built was quite stable.

CONCLUSION

From the perspective of the Chinese healthcare system, CYP2D6*10 pharmacogenetic testing was cost effective for postmenopausal women with ER-positive early breast cancer.

CYP2D6*10 pharmacogenetic-guided SERM could be a cost-effective strategy in Chinese patients with hormone receptor-positive breast cancer

Aim: To assess the cost-effectiveness of CYP2D6*10 genetic testing for the management of Chinese women with hormone receptor-positive (HR+) breast cancer treated with selective estrogen receptor modulator. Methods: A Markov model was developed to evaluate a total expected cost and an incremental cost-effectiveness ratio (ICER). Robustness of the model was addressed in one-way analyses and probabilistic sensitivity analysis. Results: The cost of strategies of tamoxifen, toremifene without genotyping and the strategy base on CYP2D6*10 genotype were $63,879.19, $90,156.60 and $95,021.41, and the quality-adjusted life years gained are 8.1588, 12.89687 and 13.85911, respectively. The incremental cost-effectiveness ratio of the CYP2D6*10 testing versus toremifene were 5,055.74221/quality-adjusted life year, respectively. Conclusion: CYP2D6*10 pharmacogenetic-guided selective estrogen receptor modulator can be a cost-effective strategy in the Chinese patients with hormone receptor-positive breast cancer.

Effect of OATP1B1 genetic polymorphism on the uptake of tamoxifen and its metabolite, endoxifen

Overexpression lentivirus platform was established of OATP1B1 (organic anion transporting polypeptides 1B1) wild‑type and mutant type genetic polymorphism in vitro, and using this platform we investigated and compared the uptake of tamoxifen and its metabolites by mutating the 388 and the 521 bases. The overexpression lentivirus cell platforms were successfully constructed, including OATP1B1*1a-HEK293T and OATP1B1*1b-HEK293T and OATP1B1*5-HEK293T cell model, the infection efficiency is not less than 80%. It shows a high level of gene expression at the mRNA and protein level. The tamoxifen and endoxifen can be taken up into the cells through organic anion transporter polypeptide 1B1, and OATP1B1521T>C inhibits the function of the transport protein, resulting in the content of drug in cell lysis liquid in OATP1B1*5-HEK293T group is lower than in OATP1B1*1a-HEK293T group (tamoxifen or endoxifen), with statistical significance. The content of the drug in cell lysis liquid in OATP1B1*1b-HEK293T group and the OATP1B1*1a-HEK293T group, similar with no statistical significance. These results suggest that tamoxifen and endoxifen can be transported by OATP1B1. However, OATP1B1 521T>C can inhibit the effects of OATP1B1 on tamoxifen and endoxifen in the cells.