Low grade gliomas (LGG) are the most frequent brain tumor type in children. They are often chemosensitive. However, more than 50% of these tumors will progress within the first 5 years after the start of the treatment and need a second-line therapy. In most cases, patients are still young and the risk of side effects from radiation therapy will call for another medical treatment. If a tumor does not respond to first-line chemotherapy, the prognosis worsens with 25% of deaths within the first 5 years for optic gliomas. Vinblastine (Velbe®) is an effective drug for low grade gliomas with both antiproliferative and antiangiogenic effects. An update of the Canadian phase II of weekly vinblastine (6 mg/m²/week) reported one complete response (CR), three partial responses (PR) and 9 minor responses (MR) in the first 31 patients. The 1-year progressionfree survival (PFS) rate was 57%. Tolerance of the treatment is fair allowing prolonged maintenance therapy as in Langerhans cell histiocytosis and anaplastic large cell lymphoma (ALCL). These data encourage proceeding with further testing this approach in pediatric low-grade glioma.

Nilotinib is a tyrosine kinase inhibitor (TKI) known to affect c-Kit, DDR1 and the PDGF receptors alpha and beta. PDGF is a growth factor for normal and tumoral astrocytes and oligodendrocytes. In addition, PDGF receptors are expressed on pediatric low-grade glioma vessels. Tumor response to this class of TKI has been reported occasionally . When used as monotherapy, this class of TKI was well tolerated in children, including those with brain tumors. Taking advantage of their different antiangiogenic mechanisms, their limited and non-overlapping toxicities, vinblastine and nilotinib could play an interesting role in the treatment of pediatric low-grade glioma. Nilotinib via PDGFRA and c-kit interactions may also interfere with the stroma of the tumor which is a key factor for tumor growth as shown in the NF1 mouse model. Both drugs have also immunostimulating effects especially in dendritic cells, that will be explored during treatment in selected patients. Previous to the phase II assessing the efficacy of the combination compared to vinblastine as single agent, nilotinib and vinblastine have to be administered by escalating dosages in order to identify the recommended doses of each agent when given in combination. This phase I part of the trial is justified by a possible interaction of the two drugs that are substrates of cytochrome P450 CYP3A4. Initial/starting dose of nilotinib (115 mg/m² BID) will be 50% of the recommended dose when used as monotherapy in adults (800 mg/day: 400 mg BID =230 mg/m2 BID). Initial/starting dose of vinblastine will be 50% of the recommended dose when used as monotherapy or in association with other chemotherapeutic drugs (i.e. 3 mg/m2 once a week). This justifies obtaining pharmacokinetic data on both drugs when used in combination. A phase I trial evaluating nilotinib as single agent in pediatrics in hematological malignancies is ongoing, run by the ITCC and the COG group, exploring the dose-levels 230 mg/m² to 460 mg/m² BID. The results of this phase I trial, expected by 2012, and the data of the current trial will be considered to decide whether a higher dose-level for nilotinib can be opened (350 mg/m² BID).