Genetic Modulation of Silodosin Exposure and Efficacy: The Role of CYP3A4, CYP3A5, and UGT2B7 Polymorphisms in Benign Prostatic Hyperplasia Management

Abstract

Objectives: Silodosin, a selective α1A-adrenoceptor antagonist, is used to treat lower urinary tract symptoms (LUTS) associated with benign prostatic hyperplasia (BPH). Genetic polymorphisms in drug-metabolizing enzymes and transporters may contribute to interindividual variability in its efficacy and safety. This study aimed to investigate the influence of CYP3A4, CYP3A5, UGT2B7, and ABCB1 polymorphisms on silodosin pharmacokinetics, efficacy, and safety in Russian patients with BPH. Methods: A prospective observational study included 103 Russian male patients with moderate-to-severe LUTS (IPSS > 8) due to BPH, treated with silodosin (8 mg daily) for 8 weeks. Genotyping for CYP3A4*1B, CYP3A4*22, CYP3A5*3, UGT2B7 (rs73823859, rs7439366, and rs7668282), and ABCB1 (rs4148738, rs1045642, rs2032582, and rs1128503) was performed using real-time PCR. The silodosin minimum steady-state plasma concentration (Css min) was measured via HPLC-MS. Efficacy was evaluated by the International Prostate Symptom Score (IPSS), quality of life scale, maximum urinary flow rate (Qmax), residual urine volume (RUV), and prostate volume at the baseline and week 8. Adverse drug reactions (ADRs) were recorded. Results: CYP3A4*22 CT carriers (n = 6) exhibited higher Css min (17.59 ± 2.98 vs. 9.0 ± 10.47 ng/mL, p = 0.049) but less absolute IPSS improvement (p < 0.05), likely due to higher baseline symptom severity. However, the change in IPSS (ΔIPSS_1-4) from the baseline to week 8 did not differ significantly (-5.78 ± 5.29 vs. -6.0 ± 4.54, p = 0.939). CYP3A5*3 GG homozygotes (n = 96) showed greater ΔIPSS_1-4 improvement (-6.25 ± 4.60 vs. 0.0 ± 9.53, p = 0.042) and a lower IPSS at day 28 (7.64 ± 4.50 vs. 20.0 ± 6.55, p < 0.001). UGT2B7 rs7439366 TT carriers (n = 34) had an improved Qmax (ΔQmax_1-4 5.4 vs. 3.3 and 2.0 mL/s for CC and CT, p = 0.041). ABCB1 1236C>T TT homozygotes (n = 25) showed a trend toward reduced RUV (p = 0.053). No polymorphisms were associated with adverse drug reactions (15 events in 42 patients, 35.7%). Conclusions: Genetic polymorphisms CYP3A4*22, CYP3A5*3, and UGT2B7 rs7439366 may modulate silodosin pharmacokinetics and efficacy parameters in BPH patients but not safety. Larger-scale studies are warranted to validate these initial findings.

Keywords: ABCB1; CYP3A4; CYP3A5; UGT2B7; benign prostatic hyperplasia; pharmacogenetics; pharmacokinetics; polymorphism; silodosin.