NBTXR3 activated by SBRT combined with nivolumab or pembrolizumab in patients with advanced cancers

Summary

Introduction: Immune checkpoint inhibitors (ICIs) have improved treatment outcomes in a variety of cancers; however the majority of patients (pts) exhibit resistance. Emerging evidence suggests radiation therapy (RT) can enhance response to ICIs by producing an immunomodulatory effect. NBTXR3, composed of functionalized hafnium oxide nanoparticles, is injected intratumorally and activated by RT. NBTXR3 increases RT energy deposition inside tumor cells and subsequent tumor cell death, without adding toxicity to healthy tissues. Preclinical data demonstrate NBTXR3/RT can trigger a local and systemic anti-tumor immune response and overcome anti-PD-1 resistance. NBTXR3/RT combined with anti-PD-1 may prime the immune system to increase the proportion of ICI responders or convert ICI non-responders to responders.

Materials and Methods: A multicenter, open-label, phase I trial [NCT03589339] evaluating NBTXR3/SBRT/anti-PD-1 (nivolumab or pembrolizumab) in 3 cohorts (1) Locoregional recurrent or recurrent and metastatic HNSCC amenable to HN re-irradiation, (2) lung or (3) liver metastases from any primary cancer eligible for anti-PD-1. Stereotactic body RT (SBRT) is delivered at tumor-site specific doses per standard practice. Primary objective is to determine the NBTXR3/SBRT/anti-PD-1 recommended phase 2 dose in each cohort. Secondary objectives are anti-tumor response (objective response rate), safety, and feasibility of NBTXR3 injection.

Results: Nine pts have been treated, 3 HNSCC, 4 lung and 2 liver. HNSCC was the primary cancer in 2 pts in the lung and 1 pt in the liver cohort. 7/9 pts were anti-PD-1 non-responders. Overall tumor regression was observed in 8/9 pts. NBTXR3/SBRT/anti-PD-1 resulted in tumor regression in 6/7 pts who had progressed on prior anti-PD-1. One anti-PD-1 naïve HNSCC pt achieved a complete response lasting over a year in the injected lymph node. 2 SAEs related to anti-PD-1 and possibly related to NBTXR3 (G5 pneumonitis, G4 hyperglycemia) were observed in 1 anti-PD-1 naïve HNSCC pt and considered DLTs. This pt also experienced 2 other SAEs (G4 diabetic ketoacidosis, G4 acute kidney injury) related to anti-PD-1. SBRT-related safety profile was as expected.

Conclusions: Safety data from this first-in-human phase I trial evaluating NBTXR3/SBRT/anti-PD-1 in pts with advanced cancers show NBTXR3 intratumoral injection is feasible and well-tolerated in HNSCC, lung, and liver metastases. NBTXR3/SBRT/anti-PD-1 demonstrated promising signs of efficacy and led to tumor regression in pts having progressed on prior anti-PD-1. These data support further development of NBTXR3/SBRT in combination with anti-PD-1 as well as other ICIs.