Accelerating drug development for neuroblastoma - New Drug Development Strategy: an Innovative Therapies for Children with Cancer, European Network for Cancer Research in Children and Adolescents and International Society of Paediatric Oncology Europe Neuroblastoma project.

INTRODUCTION: Neuroblastoma, the commonest paediatric extra-cranial tumour, remains a leading cause of death from cancer in children. There is an urgent need to develop new drugs to improve cure rates and reduce long-term toxicity and to incorporate molecularly targeted therapies into treatment. Many potential drugs are becoming available, but have to be prioritised for clinical trials due to the relatively small numbers of patients. Areas covered: The current drug development model has been slow, associated with significant attrition, and few new drugs have been developed for neuroblastoma. The Neuroblastoma New Drug Development Strategy (NDDS) has: 1) established a group with expertise in drug development; 2) prioritised targets and drugs according to tumour biology (target expression, dependency, pre-clinical data; potential combinations; biomarkers), identifying as priority targets ALK, MEK, CDK4/6, MDM2, MYCN (druggable by BET bromodomain, aurora kinase, mTORC1/2) BIRC5 and checkpoint kinase 1; 3) promoted clinical trials with target-prioritised drugs. Drugs showing activity can be rapidly transitioned via parallel randomised trials into front-line studies. Expert opinion: The Neuroblastoma NDDS is based on the premise that optimal drug development is reliant on knowledge of tumour biology and prioritisation. This approach will accelerate neuroblastoma drug development and other poor prognosis childhood malignancies.

DHFR-mediated effects of methotrexate in medulloblastoma and osteosarcoma cells: the same outcome of treatment with different doses in sensitive cell lines.

Although methotrexate (MTX) is the most well-known antifolate included in many standard therapeutic regimens, substantial toxicity limits its wider use, particularly in pediatric oncology. Our study focused on a detailed analysis of MTX effects in cell lines derived from two types of pediatric solid tumors: medulloblastoma and osteosarcoma. The main aim of this study was to analyze the effects of treatment with MTX at concentrations comparable to MTX plasma levels in patients treated with high-dose or low-dose MTX. The results showed that treatment with MTX significantly decreased proliferation activity, inhibited the cell cycle at S-phase and induced apoptosis in Daoy and Saos-2 reference cell lines, which were found to be MTX-sensitive. Furthermore, no difference in these effects was observed following treatment with various doses of MTX ranging from 1 to 40 µM. These findings suggest the possibility of achieving the same outcome with the application of low-dose MTX, an extremely important result, particularly for clinical practice. Another important aspect of treatment with high-dose MTX in clinical practice is the administration of leucovorin (LV) as an antidote to reduce MTX toxicity in normal cells. For this reason, the combined application of MTX and LV was also included in our experiments; however, this application of MTX together with LV did not elicit any detectable effect. The expression analysis of genes involved in the mechanisms of resistance to MTX was a final component of our study, and the results helped us to elucidate the mechanisms of the various responses to MTX among the cell lines included in our study.

Second complete remission of relapsed medulloblastoma induced by metronomic chemotherapy.

Prognosis for children with relapsed medulloblastoma remains poor. Metronomic chemotherapy may offer some benefit to patients treated initially with intensive regimens. However, dosing and duration of such palliative treatment have not been systematically studied. Here we describe a child with medulloblastoma relapsing after initial high-dose chemotherapy and standard radiotherapy. The patient was then treated with metronomic chemotherapy and achieved second complete remission after 21 months of treatment. Three months off therapy he relapsed again and died from progressive disease. This case illustrates the potential benefit of metronomic chemotherapy but also shows the uncertainty of when to stop metronomic chemotherapy while balancing toxicity.

Pretreatment plasma folate modulates the pharmacodynamic effect of high-dose methotrexate in children with acute lymphoblastic leukemia and non-Hodgkin lymphoma: "folate overrescue" concept revisited.

BACKGROUND: To evaluate the influence of pretreatment plasma folate concentrations on methotrexate exposure in children with acute lymphoblastic leukemia/non-Hodgkin lymphoma treated with high-dose methotrexate, we assessed time profiles of plasma homocysteine, folate, and vitamin B(12) concentrations in children treated with high-dose methotrexate with leucovorin rescue. METHODS: We analyzed 98 treatment courses. The study endpoints were to determine how methotrexate exposure is related to homocysteine accumulation and whether it is influenced by pretreatment plasma folate. RESULTS: Peak concentrations of homocysteine increased from the start of the intravenous infusion through cessation of methotrexate therapy up to time point t(42), when this trend was reversed by administration of folinic acid. The area under the curve (AUC) for plasma homocysteine showed decreasing course-to-course tendencies with a statistically significant decrease only between courses 1 and 2 (P 10 nmol/L. Correspondingly, in the courses with low initial folate, peak plasma concentrations of methotrexate were significantly higher than in courses with high precourse concentrations of plasma folate. CONCLUSION: Endogenous pretreatment plasma folate modulates the magnitude of the methotrexate effect, providing support for a "folate overrescue" concept.

Severe encephalopathy induced by the first but not the second course of high-dose methotrexate mirrored by plasma homocysteine elevations and preceded by extreme differences in pretreatment plasma folate.

Plasma homocysteine has recently been associated with the occurrence of methotrexate-related neurotoxicity. We observed extreme elevations of homocysteine in a 9-year-old boy presenting with leukemia treated with the ALL-BFM 95 protocol. Coma occurred at about the 71st hour from the first methotrexate administration, and lasted for 30 h but MRI and CT studies showed no intracranial pathology. The second course of high-dose methotrexate was administered with no complications. Homocysteine areas under the curve (AUC) were calculated as the sum of areas of rectangles during the 6-hour intervals from T(0) to T(72) hours (AUC(0--72)) and methotrexate AUCs were evaluated using MW/PHARM 3.3 software. The AUC of homocysteine during the first, toxic course was 5.2 times higher than AUC during the second administration, whereas AUC of methotrexate also differed by a factor of 5. Plasma concentrations of folate prior to the first and the second courses, respectively, were 4.4 versus 45 micromol/l making this difference the most striking discriminator between the two courses. Mutation analysis showed that the patient was heterozygous for the C 677 T mutation in the MTHFR gene. We suggest that plasma homocysteine, pretreatment plasma folate and possibly the presence of MTHFR mutations may be biomarkers of methotrexate toxicity and possibly its antifolate effect targeted towards the tumor as well.