NBTXR3 Activated By Radiotherapy In Combination With Anti-PD-1 Therapy: A Phase I Study

International journal of radiation oncology, biology, physics, 2020 · Shen C, Frakes JM, Weiss J, Caudell J, Hackman T, Akulian J, et al.


C. Shen1, J.M. Frakes2, J. Weiss3, J. Caudell4, T. Hackman5, J. Akulian6, G.E. El-Haddad4, R. Dixon5, Y. Hu7, A. Pearson8, H. Barsoumian7, M.A. Cortez7, K. Jameson9, P. Said10, J.W. Welsh7, and T. Seiwert8

1 — University of North Carolina Hospitals, Chapel Hill, NC
2 — H. Lee Moffitt Cancer Center and Research Institute, Department of Radiation Oncology, Tampa, FL, 3 University of North Carolina Lineberger Comprehensive Cancer Center, Chapel Hill, NC
4 — Moffitt Cancer Center, Tampa, FL
5 — University of North Carolina School of Medicine, Chapel Hill, NC
6 — UNC Hospital, Chapel Hill, NC
7 — Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX
8 — University of Chicago, Chicago, IL
9 — Nanobiotix Corp, Cambridge, MA, United States
10 — Nanobiotix, Paris, France


Purpose/Objective(s): Immune checkpoint inhibitors (ICIs) are being increasingly used to improve patient outcomes across different cancer types. However, the response rate to ICIs remains low (∼15%), indicating the need for novel strategies to improve treatment outcome. Emerging evidence suggests that radiation therapy (RT) could potentially enhance the antitumor response and provide synergy with ICIs. RT dose and ultimate efficacy are however limited by toxicity related to exposure of healthy tissues. The first-in-class radioenhancer NBTXR3, administered by direct intratumoral injection, is designed at the nanoscale to increase RT dose deposition within tumor cells and RT-dependent tumor cell killing, without increasing toxicity to surrounding normal tissue. Preclinical and early clinical data suggest NBTXR3 activated by RT can trigger an anti-tumor immune response, producing both local and systemic (abscopal) effects. We hypothesize that NBTXR3 activated by RT, in combination with anti-PD-1 therapy (R3/RT/PD-1), will act synergistically to maximize the local RT effect and produce a systemic response sufficient to increase the proportion of ICI responders or convert ICI non-responders to responders.

Materials/Methods: This multicenter, open-label, phase I trial [NCT03589339] will evaluate safety and tolerability of R3/RT/PD-1 in three cohorts: (1) Locoregional recurrent or recurrent and metastatic head and neck squamous cell carcinoma (HNSCC) amenable to re-irradiation of the HN field, (2) Lung metastases, or (3) Liver metastases, both from any primary cancer eligible for anti-PD-1 treatment. Approximately two-thirds of patients in each cohort will be anti-PD-1 non-responders. NBTXR3 injected volume is based on a percentage of baseline gross tumor volume (GTV).

Results: The primary objective is to determine the R3/RT/PD-1 recommended phase 2 dose in each cohort. Secondary objectives are to evaluate anti-tumor response (objective response rate; ORR), safety and feasibility of NBTXR3 injection, and NBTXR3 body kinetic profile. Exploratory objectives will assess biomarkers of R3/RT/PD-1 response, including PD-L1 status by IHC, as well as mRNA and cytokine immune marker profiling. Recruitment is ongoing. To date, three patients have been treated, one in cohort 1 and two in cohort 2.

Conclusion: NBTXR3 activated by RT induces an anti-tumor immune response which may convert immunologically “cold” tumors into “hot” tumors. In combination R3/RT/PD-1 holds the potential to increase the proportion of ICI responders or convert ICI non-responders to responders.

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