CTIM-21. NRG-BN010: A SAFETY RUN-IN AND PHASE II STUDY EVALUATING THE COMBINATION OF TOCILIZUMAB, ATEZOLIZUMAB, AND FRACTIONATED STEREOTACTIC RADIOTHERAPY IN RECURRENT GLIOBLASTOMA – TRIAL IN PROGRESS

Abstract BACKGROUND The glioblastoma (GBM) tumor microenvironment (TME) is characterized by a paucity of effector T cells and massive infiltration of immunosuppressive tumor-associated macrophages (TAMs). Inhibition of the interleukin-6 receptor (IL6R) has been demonstrated in preclinical models to repolarize TAMs toward an immunostimulatory phenotype, rendering GBM more susceptible to PD-1/PD-L1 inhibition. Additional preclinical data suggest that fractionated stereotactic radiotherapy (FSRT) can stimulate the release and presentation of tumor-specific antigens, acting as an in-situ vaccine and potentially converting a “cold” TME to a T cell-inflamed state. We designed a safety run-in and phase II study to evaluate the efficacy, safety, and impact on the TME of the combination of IL6R inhibition (tocilizumab), PD-L1 inhibition (atezolizumab), and FSRT in patients with recurrent GBM (rGBM). METHODS NRG-BN010 (NCT04729959) is open to enrollment for adults with rGBM following prior radiotherapy and has 3 components: a safety run-in to determine the recommended phase II dose (RP2D) of the treatment regimen, a phase II single-arm nonsurgical cohort to assess efficacy of the treatment regimen at the RP2D, and a window-of-opportunity surgical cohort. Once the safety run-in (n=12, 3 + 3 design) has determined the RP2D, the phase II and surgical cohorts will open. Phase II patients (n=25, Simon 2-stage design, primary endpoint objective radiographic response) receive an initial pre-FSRT cycle of tocilizumab (plus atezolizumab if included in the RP2D). Within 3-7 days later, the patient receives FSRT (8 Gy x 3 fx), followed by resumption of systemic therapy. Surgical cohort patients (n=16, 1:1 randomization) receive a neoadjuvant cycle of atezolizumab with (n=8) vs. without (n=8) tocilizumab, then FSRT 3-7 days later, then surgical resection 7-14 days after FSRT. Post-operatively, all patients resume systemic therapy at the RP2D. Fresh tumor tissues will be subjected to deep immune profiling to understand the impact of tocilizumab on TAMs in the GBM TME.