Therapeutic Drug Monitoring of Everolimus

Abstract

In 2014, the Immunosuppressive Drugs Scientific Committee of the International Association of Therapeutic Drug Monitoring and Clinical Toxicology called a meeting of international experts to provide recommendations to guide therapeutic drug monitoring (TDM) of everolimus (EVR) and its optimal use in clinical practice. EVR is a potent inhibitor of the mammalian target of rapamycin, approved for the prevention of organ transplant rejection and for the treatment of various types of cancer and tuberous sclerosis complex. EVR fulfills the prerequisites for TDM, having a narrow therapeutic range, high interindividual pharmacokinetic variability, and established drug exposure-response relationships. EVR trough concentrations (C0) demonstrate a good relationship with overall exposure, providing a simple and reliable index for TDM. Whole-blood samples should be used for measurement of EVR C0, and sampling times should be standardized to occur within 1 hour before the next dose, which should be taken at the same time everyday and preferably without food. In transplantation settings, EVR should be generally targeted to a C0 of 3-8 ng/mL when used in combination with other immunosuppressive drugs (calcineurin inhibitors and glucocorticoids); in calcineurin inhibitor-free regimens, the EVR target C0 range should be 6-10 ng/mL. Further studies are required to determine the clinical utility of TDM in nontransplantation settings. The choice of analytical method and differences between methods should be carefully considered when determining EVR concentrations, and when comparing and interpreting clinical trial outcomes. At present, a fully validated liquid chromatography tandem mass spectrometry assay is the preferred method for determination of EVR C0, with a lower limit of quantification close to 1 ng/mL. Use of certified commercially available whole-blood calibrators to avoid calibration bias and participation in external proficiency-testing programs to allow continuous cross-validation and proof of analytical quality are highly recommended. Development of alternative assays to facilitate on-site measurement of EVR C0 is encouraged.

Practical Recommendations for Therapeutic Drug Monitoring of Kinase Inhibitors in Oncology

“…In transplantation medicine, TDM is routinely applied for everolimus, using a window of 6–10 ng/mL or 3–8 ng/mL in combination therapy 94. No target for TDM has been validated in oncology.…”

“…Based on experience in transplant and pediatric patients, everolimus TDM seems feasible 94, 97. Although exposure–response relations are seen for everolimus in oncology, no formal PK‐target has been established yet.…”

Everolimus in the treatment of neuroendocrine tumors: efficacy, side-effects, resistance, and factors affecting its place in the treatment sequence

“…Balancing the anti-tumor activity and treatment-associated toxicity, as well as maintaining QOL is important in term of long-term continuation. Although it is not required in the real clinical practice, therapeutic drug monitoring may provide important information in this regard[167], as recommended for the use of immunosuppressants after organ transplantation[214]. Development of severe AEs, especially pulmonary toxicities and infections (Table 7)[22,23,75,76,93], can result in fatal outcomes, thus screening of occult infections and pulmonary function is mandatory before everolimus initiation.…”

Use of Everolimus in Liver Transplantation

“…Upon introduction of EVR in patients on CyA, concomitant CyA reduction is therefore warranted. 11,12,15 …”

“…This results in loading doses not being required and easier dose adjustments in clinical practice. 9-12 Studies investigating the exposure-response relationship have shown that EVR has a relatively narrow therapeutic window of 3 to 8 ng/mL, and monitoring of drug trough levels is warranted to adjust dose levels. 11,12 …”