Summary

Background: NBTXR3, functionalized hafnium oxide nanoparticles, administered by intratumoral injection (ITI) and activated by radiotherapy (RT), such as stereotactic body RT (SBRT), increases energy deposit inside tumor cells and subsequently tumor cell death compared to RT alone, while sparing healthy tissues. This innovative approach, which does not engage liver and renal functions, might benefit patients (pts) with unresectable liver cancers.

Methods: Phase I/II clinical trial to evaluate NBTXR3 administered by ITI activated by SBRT (45 Gy / 3 fractions / 5-7 days or 50 Gy / 5 fractions / up to 15 days) in pts with hepatocellular carcinoma (HCC) or liver metastases [NCT02721056]. Phase I 3+3 dose escalation scheme with 5 NBTXR3 dose levels: 10, 15, 22, 33, and 42% of baseline tumor volume. Primary endpoints include Recommended Phase II Dose (RP2D) determination and early DLT incidence. Secondary endpoints include safety profile, liver disease scores evolution, and early efficacy by response rate (mRECIST/RECIST 1.1).

Results: Enrolment at all dose levels is complete, 23 pts treated: 6 pts at 10% (2 SBRT doses tested due to organ constraints), 4 pts each at 15% and 22% (due to fiducial displacement and ITI shift), 3 pts at 33% and 6 pts at 42%. No early DLT was observed at any dose level. 1 SAE (late onset G3 bile duct stenosis) related to NBTXR3 and RT occurred at 22%. No clinically meaningful changes in Child-Pugh score and APRI were observed post-treatment. There were 11 AEs related to NBTXR3 and/or ITI, of which grade 3 AEs were: 2 abdominal pain (ITI related) and 1 bile duct stenosis (NBTXR3 related) No grade 4-5 AEs were observed. CT-scan showed NBTXR3 within tumor without leakage to healthy tissues. To date, the best observed responses assessed by MRI in target lesions from evaluable pts for HCC (n=11) were 5 CR, 5 PR, 1 SD and for metastases (n=7) 5 PR, 2 SD.

Conclusions: NBTXR3 has demonstrated a very good safety and tolerability profile in these patient populations. The RP2D has been determined to be 42% of tumor volume. Early efficacy results highlight the potential for NBTXR3 to address an unmet medical need in pts with unresectable primary or metastatic liver cancer.

Summary

Background: Hafnium oxide nanoparticles, NBXTR3, were developed to increase the tumor-localized high energy deposit once activated by ionizing radiation such as stereotactic body radiotherapy (SBRT) and thus to increase tumor cell death compared to the same dose of radiation. NBTXR3 is characterized by a single intratumor/intralesional (IL) administration and fits into standard RT schedule with no change in patient’s flow, treatment protocol or equipment. Herein the preliminary results of a phase I/II clinical trial evaluating this combination in patients (pts) with hepatocellular carcinoma (HCC) or liver metastasis (mets).

Methods: HCC and liver mets patients were treated with an IL injection of NBTXR3 followed by SBRT (15 Gy*3 fractions). The phase I part of the trial follows a 3+3 dose escalation design at dose levels of NBTXR3 corresponding to 10%, 15%, 22%, 33% of the baseline tumor volume. This study aims primarily to identify the Recommended Dose and the incidence of early Dose Limiting Toxicities (DLTs) of NBTXR3 activated by SBRT. Secondary endpoints include assessment of global safety profile, liver function evaluated by Child-Pugh score (CPS), AST to Platelet Ratio Index (APRI), and response rate (mRECIST/RECIST 1.1). Results: Enrollment is at the last dose level, 33%, and completed at 10% (6 pts), 15% (4 pts) and 22% (4 pts). So far, no early DLTs nor severe adverse events related to NBTXR3 were observed. Both CPS and APRI did not reveal important variations in accordance to NBTXR3 low toxicity. The best observed target lesions responses, among 7 evaluable HCC pts for response (mRECIST), were: 3 complete responses, 3 partial responses (PR) and 1 stable disease (SD) and among 5 evaluable liver mets pts: 1 PR, 3 SD and 1 progressive disease (RECIST 1.1).

Conclusions: NBTXR3 is well tolerated at the 22% dose level with an overall positive safety profile. This innovative approach might constitute a valuable solution for pts with liver tumors beyond standard treatment lines. NBTXR3 was successful in a phase II/III in soft tissue sarcoma [NCT02379845] and is currently evaluated in head and neck [NCT01946867; NCT02901483], prostate [NCT02805894] and rectum cancers [NCT02465593].

Summary

The physical mode of action of NBTXR3 may represent a breakthrough approach for the local treatment of liver cancers, as it does not engage liver and renal functions, i.e. nanoparticles are not metabolized and not excreted by kidney. A phase I/II trial has been implemented for the treatment of hepatocellular carcinoma and liver metastasis [NCT02721056].

At the 2018 Gastrointestinal Cancers Symposium (also known as ASCO-GI) at San Francisco (CA, USA), Dr. Chajon presented preliminary results on this study.

Overall, the injection of NBTXR3 was safe and well tolerated at these levels. Patients received the planned RT. No DLT occurred. Enrollment is now opened at the 22% level. NBTXR3 shows promising results in terms of safety and antitumor activity and is also currently evaluated in other six clinical studies.