Quantification of ribociclib in dried blood spots by LC–MS/MS: Method development and clinical validation

C Louwrens Braal,Mei H Lam,Tineke Rienks,Claudia J Van Tilborg,Wendy Heuts,Joan B Heijns,Monique E.M.M Bos,Ron H.J Mathijssen,Peter De Bruijn,Stijn L.W Koolen

doi:10.1016/j.jpba.2021.114118

Abstract

A reliable, specific, selective and robust liquid chromatography-tandem mass spectrometry (LC–MS/MS) method was developed for the determination of ribociclib in both dried blood spot (DBS) samples and potassium EDTA plasma. DBS samples were obtained simultaneously with a plasma sample in advanced breast cancer patients treated with ribociclib. A 6 mm disk from the central part of the dried blood spot sample was punched, followed by extraction of ribociclib using liquid-liquid extraction spiked with ribociclib-d6 as internal standard. Concentrations of ribociclib in DBS samples were correlated with corresponding plasma concentrations. From the blood sample also hematocrit was determined. The method was validated for selectivity, sensitivity, precision, lower limit of detection, linearity, stability and accuracy according to the food and drug administration (FDA) guideline. The within- and between-run precisions were ≤10.6 and ≤1.07 %, respectively; while the average accuracy ranged from 100 to 103 %. The influence of hematocrit on validation parameters was tested in the range of 0.20 – 0.40 L/L. No influence of hematocrit on validation parameters was observed. Regression analysis and a Bland-Altman plot indicated correlation between the results obtained from DBS and plasma samples. A strong correlation (R2 >0.97) between DBS samples and plasma concentration from 17 breast cancer patients was found. A number of 12 out of 17 processed DBS samples (71 %) fell inside the acceptable range of 20 % difference of simultaneously obtained plasma samples. The lower limit of quantification in DBS is 10.0 ng/mL and linearity was demonstrated up to 1000 ng/mL. In conclusion, the newly developed assay met the required standard for validation. The methods were used to study ribociclib disposition in patients with advanced breast cancer.

Highlights

Worldwide, hormone sensitive breast cancer is the most common cancer diagnosis among women
Ribociclib dried blood spot (DBS) samples were proven to be stable for at least 5 months when stored in a controlled cabin (T = 20 ◦C; relative air humidity (RH) 25 %), at ambient temperature (T = 20 ◦C) protected from light or in a fridge (T = 3−7 ◦C); with mean percentages to control of 104 %, 101 % and 105 %, respectively (Table 2)
The assay was successfully applied to quantify dried blood spot and plasma samples of breast cancer patients treated with ribociclib

Summary

Introduction

Hormone sensitive breast cancer is the most common cancer diagnosis among women. [1] Endocrine therapy is an effective, well-tolerated treatment option for metastatic and advanced breast cancer, almost all patients develop resistance. Ment option, i.e. the class of oral cyclin dependent kinase (CDK) 4/6 inhibitors, has been introduced for patients with advanced or metastatic hormone sensitive breast cancer. There are currently three CDK4/6 inhibitors – palbociclib, ribociclib and abemaciclib – approved by the Food and Drug Administration (FDA) for hormone sensitive metastatic or advanced breast cancer in combination with endocrine therapy. [5] A randomized phase III trial is ongoing to identify the pharmacokinetic targets and exposure-response relationship for the three CDK4/6 inhibitors. For that reason and to offer a more patient friendly sampling technique, dried blood spot (DBS) sampling has been developed. Advantages of the DBS method are a better stability because of less enzymatic degradation compared to plasma; easier to sample a trough concentration by self-sampling and patients with phlebitis are no longer excluded from frequent blood sampling. [8,9,10]

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Conclusion