p70S6 kinase phosphorylation for pharmacodynamic monitoring.

Inhibitors of the mammalian target of rapamycin (mTOR) are administered as immunosuppressant as well as antineoplastic agents. Because of the narrow therapeutic index of mTOR inhibitors, drug monitoring is required, and this is usually done by measuring blood drug levels. Increasing knowledge of the signaling pathways of the mTOR protein kinase provides an opportunity for pharmacodynamic drug monitoring. With the different laboratory methods it is becoming possible to measure new biomarkers to control the influence of mTOR activity. One of these biomarkers is phospho-S6 kinase, with its isoform p70S6K.