Therapeutic drug monitoring
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Over the last couple of decades, molecular diagnostics have played an increasing role in drug development. Especially within oncology, more and more drugs are being developed together with a predictive biomarker assay using the drug-diagnostic codevelopment model. Not only do these assays support the development process but also the use of the drugs after regulatory approval as an important treatment decision tool. ⋯ However, only for pembrolizumab, the PD-L1 immunohistochemical (IHC) 22C3 pharmDx assay has status as a companion diagnostic. For nivolumab and atezolizumab, the assays PD-L1 IHC 22C3 pharmDx and Ventana PD-L1 (SP142) have status as complementary diagnostics, which means that there are no requirements for testing included in the labeling for these drugs. Here, the authors discuss the clinical performance of the different IHC PD-L1 expression assays including the selection of the clinical cutoff values.