Relapsed or progressive solid tumors and leukemias have a very poor prognosis in children despite intense multimodal treatment protocols involving polychemotherapy, surgery, and radiation. Therefore, innovative treatment strategies targeting specific molecular mechanisms are urgently required. A novel class of compounds with promising anti-tumoral activities is histone deacetylase (HDAC)-inhibitors. HDACs are key enzymes involved in regulation of chromatin-structure and function of several proteins, and aberrant activities of HDACs are found in many cancer cells. Pharmacological inhibition of HDACs causes cell cycle arrest, apoptosis, differentiation, inhibition of clonogenic growth, and anti-angiogenic effects in numerous cancer cells. In addition, promising anti-tumoral activity has been shown in several pre-clinical pediatric tumor models such as neuroblastoma, medulloblastoma, glioblastoma, retinoblastoma, rhabdomyosarcoma, osteosarcoma, Ewing's sarcoma, ATRT, and acute lymphoblastic leukemia. Several HDAC inhibitors are now in Phase I-III clinical trials in adult patients demonstrating a good safety profile and promising anti-neoplastic activity. The first of these compounds, suberoylanilide hydroxamic acid (SAHA, vorinostat, Zolinza), was recently approved by the FDA for the treatment of refractory cutaneous T-cell lymphoma. Vorinostat showed linear pharmacokinetics, good oral bioavailability and a broad range of anti-tumor activity in a Phase I clinical trial including 73 adult relapsed tumor patients. The determined peak plasma levels were in the range of 658±439 ng/ml (corresponding to 2.5±1.7 µM). At these concentrations, anti-tumoral effects on pediatric cancer cells and leukemias have been documented in vitro. Furthermore, vorinostat passes the blood brain barrier in mice, thus making it a suitable compound for the treatment of brain tumors.
The aim of this study is to define a dose recommendation of vorinostat in pediatric oncology, to determine pharmacokinetics of vorinostat in children, determine response rates, safety and feasibility. The design is an open, multicenter Phase I/II trial. Children and adolescents (3-18 years) with relapsed or therapy-refractory solid tumor, lymphoma or leukemia following standard treatment protocols in pediatric oncology will be included. 50 patients will be recruited over 2 years. Vorinostat will be taken orally once per day on an outpatient basis and the dose will be escalated until the individual maximum tolerated dose is established. This dose will then be applied for 3 months, when tumor response will be evaluated. Patients without progression at first response evaluation will continue treatment for a maximum of 9 months. After end of treatment (EOT) follow-up evaluations will be performed for 3 months. Pharmacokinetic studies will be performed in plasma, and in optional cerebrospinal fluid samples. Biomarkers (BMP4, IL-6, IL10 induction following Vorinostat treatment, basal histone acetylation, HDACs and H23B in archived tumor samples) will be determined and correlated with treatment response.
