CTIM-36. IMMUNOHISTOCHEMISTRY EVALUATION ON PRE-TREATMENT TUMOR TISSUE PREDICTS TREATMENT RESPONSE TO MN-166 (IBUDILAST) AND TEMOZOLOMIDE COMBINATION THERAPY IN GLIOBLASTOMA PATIENTS

Abstract STUDY DESIGN MN-166-GBM-1201 is a Phase I/II open-label clinical trial to evaluate MN166 (ibudilast) and temozolomide (TMZ) combination treatment in newly diagnosed and recurrent glioblastoma (GBM) patients. 62 GBM patients (34 newly diagnosed and 28 recurrent) were enrolled in the study. All patients received MN-166 and TMZ combination treatment until disease progression or withdrawal from the study for other reasons. METHODS Pre-treatment tumor tissue at initial surgery from 24 study participants was evaluated to determine potential predictors of response to MN-166, which has been shown to inhibit the interaction between macrophage migration inhibitory factor (MIF) and CD74 with ERK phosphorylation downstream of CD74. We looked at CD11b and CD3 expression to characterize the immune profile within the tumors and Ki67 to determine percentage of proliferating tumor cells, all of which were calculated by a masked researcher. Then, patients were stratified based on progression within the first five months after receiving MN-166 and TMZ. RESULTS Patients who did not progress within 5 months had a significantly lower percentage of CD3+ T cell infiltration than nonresponding patients (p = 0.045), and CD74 expression was lower in patients with no progression (p = 0.16). The other markers demonstrated no differences. MN-166 and TMZ combination therapy was generally safe and well tolerated. CONCLUSION CD3 expression was a good predictor for tumor progression for five months in recurrent GBM patients treated with MN-166 and TMZ. T cell infiltration within GBM tumors has been an active area of research with the success of immune checkpoint blockade (ICB) therapies in other cancers. Moreover, MN-166 has been shown to impact immune suppressive myeloid cells, which are linked to the immune suppressive tumor microenvironment and a resistance mechanism to ICB. Collectively, we postulate that the efficacy of MN-166 for treatment of GBM could be further enhanced by co-treatment with ICBs.