An Efficient UPLC-MS/MS Method Established to Detect Relugolix Concentration in Rat Plasma

Liying Xing, Yanan Liu, Ya-Nan Liu, Hongye Yao, Tingting Wang, Fuchen Xie, Shunbin Luo, Pingping Luo, Shengling Tang
Frontiers in pharmacology · 2022 · vol. 13 , pp. 874973 · doi:10.3389/fphar.2022.874973 · PMID:35784757 · PMC9243301 · W4282961985
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⚙ AI-generated summary by claude@2026-06, 2026-06-08 ⓘ

An efficient UPLC-MS/MS method was developed to detect relugolix in rat plasma, finding that daidzein co-administration decreased relugolix Cmax and AUC.

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⚙ AI-generated deep summary by claude@2026-06, 2026-06-09 ⓘ

The paper studied the development and validation of an ultra-performance liquid chromatography–tandem mass spectrometry (UPLC-MS/MS) assay to quantify relugolix concentrations in rat plasma, including a pharmacokinetic assessment after oral administration of relugolix alone (12 mg/kg) versus relugolix with daidzein (50 mg/kg) to evaluate a possible food-drug interaction. Using an apalutamide internal standard and an FDA/related bioanalytical guideline framework for validation, the method showed strong linearity across 0.7–1000 ng/mL and acceptable precision/accuracy, with stability, extraction recovery, and matrix effect meeting verification rules. Administration with daidzein decreased relugolix Cmax and AUC0–t by about 15.56% and 21.36%, respectively, though pharmacokinetic parameters were not statistically different, which the authors interpret as reflecting an induction trend in metabolism rather than a significant effect. The paper does not explicitly discuss endometriosis or adenomyosis; it was included in the corpus via a keyword match in the upstream search index.

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Abstract

Relugolix, a gonadotropin-releasing hormone (GnRH) receptor antagonist, has been well studied in the treatment of endometriosis symptomatic. It is mainly metabolized by the CYP3A subfamily of P450 enzymes, while minorly metabolized by CYP2C8. Daidzein in different dose groups exhibited a certain induction on the mRNA expression level of CYP3A4 and resulted in the potent induction of CYP3A4. However, it is still unknown whether daidzein and relugolix interact. We developed an effective ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method to study the effect of daidzein on the pharmacokinetics of relugolix in rats after oral administration of 12 mg/kg relugolix in a single or mixed of 50 mg/kg daidzein. The results showed that the method had respectable linearity (r 2 > 0.999) on the scale of 0.7-1000 ng/mL. The intra-day precision was between 3.0% and 8.4% in this assay, and the inter-day was between 4.0% and 11.7%. The intra-day accuracy was from -4.3% to 6.1%, and the inter-day was 2.9% to 12.1%. Another three key indicators, including the stability, the recovery rate of extraction and the new technique's matrix effect, were perfectly in accord with the test verification rule in the biological medium by the United States Food and Drug Administration. Meanwhile, treatment with daidzein led to a decrease in Cmax and AUC0-t of relugolix by about 15.56% and 21.36%, respectively. Although there was no statistical difference in pharmacokinetic parameters, it reflected the induction trend of daidzein on relugolix metabolism for food-drug interaction. It would provide reference and improvement value for subsequent experiments.

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endometriosis

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