Genetic variants in tamoxifen metabolism and early treatment discontinuation among premenopausal breast cancer patients

Purpose: Premenopausal, estrogen receptor (ER)-positive breast cancer patients should receive tamoxifen for at least 5 years, but many prematurely discontinue. Activation, transport, and deactivation of tamoxifen and its metabolites are controlled by proteins encoded by genes with functional variations. We examined the impact of genetic polymorphisms in the tamoxifen pathway on early treatment discontinuation. Methods: We included premenopausal women diagnosed with ER-positive breast cancer (2002–2011) in Denmark who initiated tamoxifen. We genotyped 26 genetic variants in 15 enzymes involved in tamoxifen metabolism. Early discontinuation was defined as tamoxifen use for &lt; 5 years. We estimated individual and combined effects of genetic variants using a Bayesian pathway approach. We report Bayes Factors (BF), wherein values &gt; 1 indicate support of an effect of the genetic pathway on discontinuation (compared with no effect). Results: Among 3,729 patients, 536 (14%) discontinued tamoxifen within 5 years. Genetic variants involved in tamoxifen activation impacted early discontinuation (BF = 7.5), in a manner driven almost entirely by CYP2D6 activity (BF = 22.6). Several variants in CYP2D6 and transporter genes synergistically increased the hazard of early discontinuation (e.g., CYP2D6*2 and ABCC2; BF = 138). Conclusions: Variants in enzymes responsible for activating tamoxifen metabolites—particularly within CYP2D6—influence early tamoxifen discontinuation. CYP2D6 variants synergistically interact with transporter gene variants, namely ABCC2, to further raise the risk of discontinuation.</p

Safety and immunogenicity of a freeze-dried, Vero cell culture-derived, inactivated Japanese encephalitis vaccine (KD-287, ENCEVAC®) versus a mouse brain-derived inactivated Japanese encephalitis vaccine in children: a phase III, multicenter, double-blinded, randomized trial

BACKGROUND: Although mouse brain-derived, inactivated Japanese encephalitis vaccines (JE-MBs) have been successfully used for a long time, potential rare neurological complications have prompted the development of a Vero cell culture-derived inactivated vaccine (JE-VC). In a phase III clinical study, we aimed to compare the safety and immunogenicity of a JE-VC, KD-287 with a JE-MB, JEV-GCC, in children. METHODS: In this multicenter, double-blinded, randomized controlled trial, the study population consisted of 205 healthy Korean children aged 12–23 months. Each subject was subcutaneously vaccinated with either KD-287 or JEV-GCC twice at an interval of 2 weeks and then vaccinated once 12 months after the second vaccination. Neutralizing antibodies were measured by the plaque reduction neutralization test using the homologous and heterologous, as a post hoc analysis, challenge virus strains. RESULTS: The three-dose regimen of KD-287 showed a comparable safety profile with JEV-GCC except higher incidence of fever after the first dose (30.4% and 14.7%, respectively). Most of the fever was mild degree (61.3% and 66.7%, respectively). KD-287 fulfilled the non-inferiority criteria for seroconversion rate (SCR) and geometric mean titer (GMT) of the neutralizing antibody, which were the primary endpoints, at 4 weeks after the third vaccination (95% CI: −1.00, 3.10 for the SCR difference and 10.8, 17.6 for the GMT ratio). The SCRs of KD-287 were all 100% and the GMTs were higher in the KD-287 group than in the JEV-GCC group after the second vaccination and before and after the third vaccination (GMT ratio: 5.59, 20.13, and 13.79, respectively, p < 0.001 in all). GMTs were higher in the KD-287 group in the heterologous analysis also (GMT ratio: 4.05, 5.15, and 4.19, respectively, p < 0.001 in all). CONCLUSIONS: This study suggests that the KD-287, a JE-VC is as safe as and may be more effective than the licensed MB-derived vaccine. KD-287 could thus be useful as a second-generation vaccine and substitute for the current JE-MB vaccine in Korean children. TRIAL REGISTRATION: ClinicalTrials.gov: NCT01150942 ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12879-014-0744-4) contains supplementary material, which is available to authorized users