Abstract Malignant gliomas, the most common primary brain tumors, are highly invasive and neurologically destructive tumors with very poor prognosis due to the impossibility of removing tumor tissue completely by surgery and the limited activity of therapeutic agents. PHA-848125 is a dual CDKs and TRKA inhibitor and is therefore potentially active against two major pathways involved in glioma pathogenesis: signaling mediated by tyrosine kinase growth factor receptors and control of G1-S phase progression of the cell cycle. PHA-848125 has demonstrated good antitumor activity in many preclinical tumor models, good tolerability in Phase 1 studies and it is currently undergoing Phase 2 clinical trials. To explore the rationale for pursuing brain tumors as a clinical indication for PHA-848125, we firstly analyzed distribution of the 14C-labeled compound, demonstrating that it is able to efficiently cross the blood brain barrier. Next, we tested in vitro activity of the compound on a panel of glioma cell lines showing that it was able to inhibit cell proliferation (IC50: 1.4–2.5 µM), DNA synthesis (inhibition of BrdU incorporation ranging from 39 to 92 %), cell cycle markers (inhibition of Phospho-pRb, cdc6, cyclin A and cyclin B1 expression) and signal transduction markers (inhibition of Phospho-TRKA, Phospho-MAPK and Phospho-AKT). Significantly, it was also able to induce cell death through autophagy (mainly in cells with functional Retinoblastoma protein) or apoptosis (in cells with disrupted Retinoblastoma pathway). Antitumor efficacy in vivo was evaluated both in subcutaneous and intracranially implanted tumors. PHA-848125 showed significant antitumor efficacy by oral route: tumor growth inhibition of 71% and 80% on U87MG and U251 subcutaneous xenograft models, respectively and a 30% increase in survival time in the intracranial U251 model. Finally, in the U87MG xenograft model, the combination of PHA-848125 with temozolomide resulted in a synergistic effect and a clear therapeutic gain was also observed with a triple treatment adding PHA-848125 to radiotherapy and temozolomide. In conclusion, preclinical data obtained to date suggest that PHA-848125 may become a useful agent in chemotherapy regimens for glioma patients and support its evaluation in Phase 2 trials for this indication. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):PR-3.