Summary

Purpose: Elderly head and neck squamous cell carcinoma (HSNCC) patients (pts) ineligible for standard of care treatment require new therapeutic approaches. NBTXR3, hafnium oxide nanoparticles, may represent such an option. NBTXR3 is activated by radiotherapy, enhancing its effects, leading to physical destruction of cancer cells. A Phase I/II trial [NCT01946867] is underway to evaluate NBTXR3 in elderly (≥70 years) or frail pts with HNSCC of the oral cavity and oropharynx ineligible for cisplatin or intolerant to cetuximab.

Method & Materials: Pts received a single intratumoral injection of NBTXR3 and intensity modulated radiation therapy (IMRT; 70 Gy/35 fractions/7 weeks). The study was a 3 + 3 dose escalation to test the NBTXR3 dose equivalent to 5, 10, 15, and 22% of baseline tumor volume, followed by a dose expansion. Primary endpoints include Recommended Phase 2 Dose (RP2D) determination and early dose limiting toxicities (DLT). Presence of NBTXR3 in surrounding healthy tissues and efficacy (RECIST 1.1 principles) were also evaluated.

Results: Enrollment for the dose escalation phase was completed at all dose levels: 5% (3 pts), 10% (3 pts), 15% (5 pts), and 22% (8 pts). No early DLT or SAE related to NBTXR3 or injection were observed. One G1 AE (asthenia; 22%) related to NBTXR3 and four AEs (G2 oral pain, G1 tumor hemorrhage, G1 asthenia, and G1 injection site hemorrhage) related to injection were reported. RT-related toxicity was as expected. The RP2D has been determined to be 22%. CT-scan assessment demonstrated absence of NBTXR3 in surrounding tissues. Among 13 evaluable pts treated at doses ≥10%, 9 achieved complete response of the injected lesion. The final dose escalation safety results will be presented herein.

Conclusion: NBTXR3 was well tolerated at all tested doses and demonstrated a good safety profile. A dose expansion phase has started with the identified RP2D. NBTXR3 is currently being evaluated in a phase II/III trial in soft tissue sarcoma [NCT02379845] and phase I/II trials in prostate [NCT02805894], liver [NCT02721056] and rectal [NCT02465593] cancers.

Clinical Relevance & Application: The results of this study highlight the potential of NBTXR3 as a novel treatment option for elderly and/or frail pts with locally advanced HNSCC and address an unmet medical need.

Summary

Introduction: New therapeutic approaches are needed for elderly or frail head and neck squamous cell carcinoma (HNSCC) patients (pts) ineligible for standard of care. NBTXR3, hafnium oxide nanoparticles injected intratumorally, may represent an option. Otherwise inert, NBTXR3 augments the radiation therapy (RT) dose within tumor cells when activated by RT, increasing tumor cell death compared to RT alone.

Objectives: The purpose of this Phase I was to evaluate safety (dose limiting toxicity; DLT) and determine the NBTXR3 recommended phase 2 dose (RP2D) in elderly or frail HNSCC pts.

Methods: Eligible pts had stage III or IV HNSCC of oral cavity or oropharynx, were aged ≥70 years or ≥65 years and unable to receive cisplatin but eligible for RT [NCT01946867]. A 3+3 dose escalation design was employed, with NBTRX3 dose levels of 5%, 10%, 15% and 22% of baseline tumor volume. Following intratumoral NBTXR3 injection, pts received IMRT (70 Gy; 35 fractions/7 weeks). Primary endpoints were RP2D and DLT. Localization of NBTXR3 and preliminary efficacy (RECIST 1.1) were also evaluated.

Results and Conclusion: Dose escalation is complete; 19 pts received NBTXR3: 3 at 5%, 3 at 10%, 5 at 15% and 8 at 22%. No NBTXR3-related DLTs or SAEs were observed. Four related AEs were reported: one AE at 15% (G1 tumor hemorrhage) and 3 AEs at 22% (G2 oral pain; G1 asthenia, G1 injection site hemorrhage). IMRT toxicity was as expected and post-injection CT scan showed NBTXR3 localized within the injected tumor. DSMB determined RP2D to be 22%. Among 13 evaluable pts at doses ≥10%, 9 had a complete response of injected tumor. Results demonstrate that NBTXR3 activated by RT is a well-tolerated therapy with encouraging anti-tumor activity. RP2D expansion is ongoing. NBTXR3 may be an option for elderly or frail pts with locally advanced HNSCC.