The development of new targeted therapies for metastatic breast cancer has improved patient outcomes yet results in different treatment results for individual patients. Host pharmacogenomic factors determine how drugs are processed in the body but these factors remain poorly understood according to current research. CYP3A4*22 and CYP3A5*3 contain two functional polymorphisms which create different drug metabolism rates in patients while current targeted therapies use cytochrome P450 enzymes CYP3A4 and CYP3A5 as their primary metabolic pathways.
Methods: The researchers studied the impact of CYP3A4 and CYP3A5 genetic polymorphisms on drug absorption and tumor development together with their corresponding molecular pathways and toxic effects in humanized CYP3A transgenic xenograft studies. The researchers used genotype-based cohorts to create breast cancer xenografts. The targeted therapies which metabolic process depends on CYP3A enzymes were given to patients for a treatment period of 28 days. The drug concentrations in plasma were determined by LC-MS/MS. The researchers assessed Ki-67 and TUNEL test results together with PI3K/AKT/mTOR pathway activity in tumor tissues. The researchers used multivariate regression modelling to study pharmacokinetic-pharmacodynamic interactions.
Results: Relative to wild-type controls, reduced-function genotypes (CYP3A4*22 and CYP3A5*3) had significantly increased systemic drug exposure, with 35-50% increases in AUC and reduced clearance (p < 0.001). Increased apoptotic indices, increased inhibition of oncogenic signalling pathways, and inhibition of tumor growth (r = 0.72, p < 0.001) were strongly associated with increased exposure. The CYP3A genotype was confirmed as an independent predictor of response by multivariate analysis (adjusted R² = 0.68). The indicators of hepatotoxicity were moderately increased in the variant genotypes, indicating a shift in the treatment window that is genotype-dependent.
Conclusions: The CYP3A4 and CYP3A5 polymorphisms markedly influence the response of patients with metastatic breast cancer to targeted treatments. The findings demonstrate that host pharmacogenomic testing can determine optimal precision oncology dosages which establish genotype-exposure-response relationships.
Keywords: CYP3A4 and CYP3A5; pharmacogenomics; precision oncology; breast cancer; personalized therapy; xenograft model; pharmacokinetics; PI3K/AKT/mTOR pathway; inhibition of tumor growth
How to cite this article: Ramana IV, Reddy DRS, CYP3A4 and CYP3A5 Polymorphisms as Predictors in Advanced Breast Cancer Treated with Emerging Therapies. Int J Drug Deliv Technol. 2026;16(4s): 710-720; DOI: 10.25258/ijddt.16.4s.83
Source of support: Nil
Conflict of interest: None