The influence of light sources on sunitinib measurements with photoisomerization

An Optimized LC-MS/MS Method for Quantification of Sunitinib and N -Desethyl Sunitinib in Human Plasma and Its Application for Therapeutic Drug Monitoring

BACKGROUND

Sunitinib (SUN) malate is an oral, multitargeted, tyrosine kinase inhibitor approved for the treatment of metastatic renal cell carcinoma, imatinib-resistant or imatinib-intolerant gastrointestinal stromal tumors, and pancreatic neuroendocrine tumors. SUN has a narrow therapeutic window and high variability in interpatient pharmacokinetic parameters. Clinical detection methods for SUN and N -desethyl SUN limit the application of SUN to therapeutic drug monitoring. All published methods for quantifying SUN in human plasma require strict light protection to avoid light-induced isomerism or the use of additional quantitative software. To avoid these difficult processes in clinical routines, the authors propose a novel method that merges the peaks of the E -isomer and Z -isomer of SUN or N -desethyl SUN into a single peak.

METHODS

The E -isomer and Z -isomer peaks of SUN or N -desethyl SUN were merged into a single peak by optimizing the mobile phases to decrease the resolution of the isomers. A suitable chromatographic column was selected to obtain a good peak shape. Thereafter, the conventional and single-peak methods (SPM) were simultaneously validated and compared according to the guidelines published by the Food and Drug Administration in 2018 and the Chinese Pharmacopoeia in 2020.

RESULTS

The verification results showed that the SPM was superior to the conventional method in the matrix effect and met the requirements for biological sample analysis. SPM was then applied to detect the total steady-state concentration of SUN and N -desethyl SUN in tumor patients who received SUN malate.

CONCLUSIONS

The established SPM makes the detection of SUN and N -desethyl SUN easier and faster without light protection or extra quantitative software, making it more appropriate for routine clinical use. The clinical application results showed that 12 patients took 37.5 mg per day, with a median total trough steady-state concentration of 75.0 ng/mL.

Molecular and Functional Analysis of Sunitinib-Resistance Induction in Human Renal Cell Carcinoma Cells

Resistance in clear cell renal cell carcinoma (ccRCC) against sunitinib is a multifaceted process encompassing numerous molecular aberrations. This induces clinical complications, reducing the treatment success. Understanding these aberrations helps us to select an adapted treatment strategy that surpasses resistance mechanisms, reverting the treatment insensitivity. In this regard, we investigated the dominant mechanisms of resistance to sunitinib and validated an optimized multidrug combination to overcome this resistance. Human ccRCC cells were exposed to single or chronic treatment with sunitinib to obtain three resistant clones. Upon manifestation of sunitinib resistance, morphometric changes in the cells were observed. At the molecular level, the production of cell membrane and extracellular matrix components, chemotaxis, and cell cycle progression were dysregulated. Molecules enforcing the cell cycle progression, i.e., cyclin A, B1, and E, were upregulated. Mass spectrometry analysis revealed the intra- and extracellular presence of N-desethyl sunitinib, the active metabolite. Lysosomal sequestration of sunitinib was confirmed. After treatment with a synergistic optimized drug combination, the cell metabolic activity in Caki-1-sunitinib-resistant cells and 3D heterotypic co-cultures was reduced by >80%, remaining inactive in non-cancerous cells. These results demonstrate geno- and phenotypic changes in response to sunitinib treatment upon resistance induction. Mimicking resistance in the laboratory served as a platform to study drug responses.