Prediction of systemic free and total valproic acid by off-line analysis of exhaled breath in epileptic children and adolescents.

Therapeutic drug monitoring (TDM) of medications with a narrow therapeutic window is a common clinical practice to minimize toxic effects and maximize clinical outcomes. Routine analyses rely on the quantification of systemic blood concentrations of drugs. Alternative matrices such as exhaled breath are appealing because of their inherent non-invasive nature. This is especially the case for pediatric patients. We have recently showcased the possibility of predicting systemic concentrations of valproic acid (VPA), an anti-seizure medication by real-time breath analysis in two real clinical settings. This approach, however, comes with the limitation of the patients having to physically exhale into the mass spectrometer. This restricts the possibility of sampling from patients not capable or available to exhale into the mass spectrometer located on the hospital premises. In this work, we developed an alternative method to overcome this limitation by collecting the breath samples in customized bags and subsequently analyzing them by secondary electrospray ionization coupled to high-resolution mass spectrometry (SESI-HRMS). A total ofn= 40 patients (mean ± SD, 11.5 ± 3.5 y.o.) diagnosed with epilepsy and taking VPA were included in this study. The patients underwent three measurements: (i) serum concentrations of total and free VPA, (ii) real-time breath analysis and (iii) off-line analysis of exhaled breath collected in bags. The agreement between the real-time and the off-line breath analysis methods was evaluated using Lin's concordance correlation coefficient (CCC). CCC was computed for ten mass spectral predictors of VPA concentrations. Lin's CCC was >0.6 for all VPA-associated features, except for two low-signal intensity isotopic peaks. Finally, free and total serum VPA concentrations were predicted by cross validating the off-line data set. Support vector machine algorithms provided the most accurate predictions with a root mean square error of cross validation of 29.0 ± 7.4 mg l-1and 3.9 ± 1.4 mg l-1for total and free VPA (mean ± SD), respectively. As a secondary analysis, we explored whether exhaled metabolites previously associated with side-effects and response to medication could be rendered by the off-line analysis method. We found that five features associated with side effects showed a CCC > 0.6, whereas none of the drug response-associated peaks reached this cut-off. We conclude that the clinically relevant free fraction of VPA can be predicted by this combination of off-line breath collection with rapid SESI-HRMS analysis. This opens new possibilities for breath based TDM in clinical settings.

The Role of mTOR Inhibitors in the Treatment of Patients with Tuberous Sclerosis Complex: Evidence-based and Expert Opinions.

Tuberous sclerosis complex (TSC) is a genetic disorder arising from mutations in the TSC1 or TSC2 genes. The resulting over-activation of the mammalian target of rapamycin (mTOR) signalling pathway leaves patients with TSC susceptible to the growth of non-malignant tumours in multiple organs. Previously, surgery was the main therapeutic option for TSC. However, pharmacological therapy with mTOR inhibitors such as everolimus and sirolimus is now emerging as an alternate approach. Everolimus and sirolimus have already been shown to be effective in treating subependymal giant cell astrocytoma (SEGA) and renal angiomyolipoma (AML), and everolimus is currently being evaluated in treating TSC-related epilepsy. In November 2013 a group of European experts convened to discuss the current options and practical considerations for treating various manifestations of TSC. This article provides evidence-based recommendations for the treatment of SEGA, TSC-related epilepsy and renal AML, with a focus on where mTOR inhibitor therapy may be considered alongside other treatment options. Safety considerations regarding mTOR inhibitor therapy are also reviewed. With evidence of beneficial effects in neurological and non-neurological TSC manifestations, mTOR inhibitors may represent a systemic treatment for TSC.

New insights into the pathophysiology of the tuberous sclerosis complex: Crosstalk of mTOR- and hippo-YAP pathways in cell growth.

Tuberous Sclerosis Complex (TSC) is a genetic disease causing uncontrolled growth of hamartomas involving different organ systems. In the last decade, dysregulation of the mTORC1 pathway was shown to be a main driver of tumor growth in TSC. Recently, a new crosstalk was detected between the mTORC1 and the Hippo-YAP pathway, another major cell signaling cascade controlling cell growth and organ size. Elucidating this connection is an important step in understanding the complexity of TSC, enabling new pharmacological targets and therapeutical options.

Topical everolimus for facial angiofibromas in the tuberous sclerosis complex. A first case report.

BACKGROUND: Facial angiofibromas are present in most of the patients with the tuberous sclerosis complex and may cause severe disfiguration of the face. The tumor growth in tuberous sclerosis complex is promoted by the disinhibition of the mammalian target of rapamycin pathway. Thus, the systemic treatment with mammalian target of rapamycin inhibitors such as sirolimus and everolimus has recently been established to treat specific tuberous sclerosis complex-associated lesions. For patients who suffer from disfiguring facial angiofibromas only, there is a need for a topical use of mammalian target of rapamycin inhibitors. Sirolimus has been shown to be beneficial in treating facial angiofibromas. But the topical use of everolimus, which has the approval to treat tuberous sclerosis complex-associated tumors, namely giant cell astrocytomas and renal angiofibromas, has not been reported. PATIENTS AND RESULTS: We present a 10-year-old girl whose facial angiofibromas were successfully treated with an everolimus ointment without relevant side effects. In addition, we provide a short pharmacological overview of sirolimus and everolimus with focus on the topical use. CONCLUSIONS: Topical everolimus seems to be a favorable and safe option for patients with facial angiofibromas who do not require systemic treatment.