A simple, precise, and sensitive HPLC method for quantification of letrozole in rat plasma: development, validation, and preclinical pharmacokinetics

Aswathi R Hegde,Srinivas Mutalik,Bharat Singh Padya,Soji Soman

doi:10.1186/s40543-021-00276-4

Aswathi R Hegde, Srinivas Mutalik + Show 2 more

Open Access

https://doi.org/10.1186/s40543-021-00276-4

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Abstract

A simple bioanalytical liquid chromatographic method was developed and validated to quantify letrozole (LTZ) in rat plasma. Protein precipitation using acidified chilled acetonitrile (containing 0.1% orthophosphoric acid) was used to extract LTZ from the plasma. Chromatographic separation was carried out on Kinetex C18 reverse phase (RP) column (250 mm × 4.6 mm i.d., 5 μm) using a mixture of 20 mM acetate buffer (pH 5.5) and acetonitirile (60:40 %v/v) eluting at 1.0 mL/min flow rate with the method responses measured at 240 nm. The optimized method was selective and established good linearity with recovery ranging between 91.16 and 99.44%. The validation experiments revealed that the method showed acceptable precision (2.61–7.48%) and accuracy (97.44–102.70%) and was found to be stable. The sensitivity of the method was demonstrated by the lowest concentration (LLOQ) detected at 75 ng/mL. Using the developed method, single-dose oral pharmacokinetics in Sprague-Dawley rats was carried out to successfully confirm the applicability of the method for the quantification of LTZ in biological matrix.

Highlights

A majority of the breast cancers are hormone dependent, of which estrogen plays an important role
Ultrapure water used in the preparation of sample and mobile phase was obtained from a Millipore Direct-Q® 3 water purification system (Millipore Corporation, MA, USA)
Being an extremely basic drug with a pKa value of 2.3, CBZ was used as the internal standard (IS), to assess the elution of LTZ by liquid-liquid extraction using methyl tertbutyl ether (MTBE)

Summary

Introduction

A majority of the breast cancers are hormone dependent, of which estrogen plays an important role. Exposure to circulating estrogen levels leads to the increased risk of developing breast cancer. Inhibition of aromatase enzyme to reduce the peripheral conversion to estrogen is an attractive strategy in the therapy of hormone-dependent breast cancer (Chumsri et al 2011). Conversion of androgens to estrogen can be effectively stopped by aromatase inhibitors (AIs), which block the aromatase enzyme impairing the growth and development of tumors Letrozole (LTZ) is a potent, non-steroidal, 3rd generation AI used to treat hormone-sensitive breast cancer. LTZ is approved for oral hormonal therapy by the USFDA and is sold under the brand name Femara® to treat local or metastatic breast cancer in post-menopausal women. LTZ undergoes complete absorption from the gastrointestinal tract and metabolizes to form the carbinol metabolite, which is inactive and further excreted in the urine (Acharjya et al 2012)

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