Effect of treating glioblastoma with a cytokine inhibitor, ibudilast, in combination with temozolomide on survival in a patient-derived xenograft model.

2062 Background: Recurrence in patients with glioblastoma (GBM) is inevitable, even in patients with O-6-Methylguanine-DNA Methyl Transferase ( MGMT) methylation. We identified increased expression of the inflammatory cytokine, Macrophage Inhibitory Factor (MIF) and its receptor CD74 in patients with recurrent tumors. High levels of MIF and CD74 were associated with poor overall survival in GBM patients. This study aims to determine efficacy of Ibudliast (MN-166; 3-isobutyryl-2-isopropylpyrazolo-[1,5-a]pyridine) to block MIF expression and decrease tumor burden. Ibudilast is an anti-inflammatory drug that was developed for the treatment of bronchial asthma. Methods: The patient derived cell lines (PDCLs) RN1 ( MGMT unmethylated), BAH1 ( MGMT methylated), and HW1 ( MGMT methylated) were treated in vitrowith different concentrations of ibudilast in combination with temozolomide (TMZ). Patient derived xenograft (PDX) models of GBM were developed and treated with the combination of ibudilast and TMZ. Overall survival was calculated. Results: Regardless of MGMT status, significant synergism between ibudilast and TMZ was observed in the PDCLs. Efficacy was associated with significantly decreased expression of its targets, MIF and CD74. Downstream proteins such as Src and Akt were also significantly inhibited. The combination induced apoptosis. RN1 tumors were established intracranially in Balb/c nude mice. Significant increases in survival times of the mice were recorded when treated with the combination. Conclusions: Ibudilast in combination with TMZ resulted in significant blockage of MIF expression, increased apoptosis and longer survival in vivo. A human pilot study for recurrent GBM patients is underway.