CTIM-05. A PHASE 1/2 STUDY OF THE COMBINATION OF INDOXIMOD AND TEMOZOLOMIDE FOR ADULT PATIENTS WITH TEMOZOLOMIDE-REFRACTORY PRIMARY HIGH-GRADE GLIOMAS

BACKGROUND Optimal management of progressive high-grade gliomas (HGG) is not fully defined and outcomes are poor. Indoleamine 2,3-dioxygenase 1 (IDO1) is an enzyme which converts tryptophan to kynurenines, which contribute to the immunosuppresive tumor microenvironment (TME). Targeting the TME by inhibiting IDO1 is a strategy for potential improvement in survival in HGG. METHODS A phase 1/2 trial using the IDO1 inhibitor indoximod was conducted in progressive grade 3 and 4 gliomas. The phase 1 cmponent used a 3 + 3 design escalating indoximod from 600mg po BID to 1200mg po BID in conjunction with temozolomide (150 mg/m2, 5/28 days). The phase 2 component consisted of 3 cohorts: A) indoximod+temozolomide B) indoximod+temozolomide+bevacizumab (patients already on bevacizumab) C) indoximod+temozolomide+stereotactic radiosurgery (SRS). Patients were treated until progression or toxicity. RESULTS 33.3% of patients developed indoximod TEAEs. There were no dose limiting toxicities in the phase 1 component (n=12). 1200 mg BID was established as the phase 2 dose of indoximod. In the phase 2 component (n=148) PFS6 was 74% (A), 93% (B), 70% (C). Median OS was 289 days [10.3 months](A), 159 days [5.7 months](B), 285 days [10.2 months](C). Correlative study results will be available for meeting presentation. CONCLUSIONS The IDO1 inhibitor indoximod proved safe and tolerable in conjunction with temozolomide, bevacizumab, and SRS in patients with progressive HGG. There was a trend toward better survival outcomes when indoximod was combined with temozolomide alone or temozolomide+SRS.