IT-36PHASE 1/2 STUDY OF THE COMBINATION OF INDOXIMOD AND TEMOZOLOMIDE FOR ADULT PATIENTS WITH TEMOZOLOMIDE-REFRACTORY PRIMARY MALIGNANT BRAIN TUMORS

BACKGROUND: Indoleamine 2, 3-dioxygenase (IDO) is a key immune-modulatory enzyme that inhibits CD8+ T cells and enhances the suppressor activity of Tregs. IDO is expressed in 50 to 90% of glioblastoma (GBM) and is correlated with poor prognosis. IDO pathway inhibitors such as indoximod (1-Methyl-D-tryptophan) can improve anti-tumor T cell response slowing the tumor growth in vivo. We have demonstrated a synergistic effect of indoximod when combined with temozolomide (TMZ) and radiation in a syngeneic orthotopic brain tumor model. This phase 1 study is designed to determine maximal tolerated dose (MTD) of indoximod in combination with TMZ in GBM followed by an expansion phase 2 testing the preliminary activity of the combination in relevant situations with the addition of bevacizumab or stereotactic radiosurgery. METHODS: After progression to standard front line-therapy, patients with GBM are enrolled in a dose escalation study of indoximod (600, 1000 or 1200 mg twice daily given orally) with a standard fixed dose of TMZ. In the phase 2 part, patients are separated into 3 cohorts: cohort 2a: indoximod with TMZ, cohort 2b: indoximod with TMZ and bevacizumab (for patients who are currently on bevacizumab), cohort 2c: indoximod with TMZ and stereotactic radiosurgery. STATISTICAL ANALYSIS: The study uses a 3 + 3 dose escalation design, until reaching the MTD or the maximal specified dose. Sample size in phase 2 is based on the primary endpoint of 6 months progression free survival (PFS). CORRELATIVE STUDIES: Assessment of primary tumor samples for IDO expression, evaluation of serum for potential biomarkers of IDO pathway activity (kynurenine and tryptophan) and a pharmacokinetic analysis will be performed. RESULTS: Study is ongoing. Updates are to be presented at the meeting.