Article date: August 2019
By: Anna Svedberg, Svante Vikingsson, Anders Vikström, Niels Hornstra, Magnus Kentson, Eva Branden, Hirsh Koyi, Bengt Bergman, Henrik Gréen in Volume 85, Issue 8, pages 1704-1709
Aims
Erlotinib is a tyrosine kinase inhibitor used in the treatment of non‐small cell lung cancer highly metabolized by the cytochrome P450 (CYP) 3A. Hence, CYP3A4 activity might be a useful predictor of erlotinib pharmacokinetics in personalized medicine. The effect of erlotinib on CYP3A activity was therefore studied in non‐small cell lung cancer patients.
Methods
The study included 32 patients scheduled for erlotinib monotherapy. CYP3A activity was assessed using quinine as a probe before and during erlotinib treatment. Plasma from blood samples drawn 16 hours post quinine administration were analysed using HPLC with fluorescence detection to determine the quinine/3‐OH‐quinine ratio.
Results
Matched samples, available from 13 patients, showed an induction of CYP3A activity (P = 0.003, Wilcoxon's signed rank test) after 2 months of treatment. The quinine/3‐OH‐quinine ratio decreased from 20.2 (± 13.4) at baseline to 11.0 (± 4.34). Single‐point samples, available from 19 patients, supported the decrease in ratio (P = 0.007, Mann–Whitney U‐test).
Conclusions
An induction of CYP3A activity was observed after 2 months of erlotinib treatment which was also seen when subdividing based on gender. It could be important to take this into consideration for patients co‐administering other CYP3A‐metabolizing drugs during erlotinib treatment and also makes it difficult to use baseline CYP3A activity to predict erlotinib pharmacokinetics.
DOI: 10.1111/bcp.13953
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