Theranostic AGuIX nanoparticles as radiosensitizer: A phase I, dose-escalation study in patients with multiple brain metastases (NANO-RAD trial)

BACKGROUND AND PURPOSE

Brain metastasis impacts greatly on patients' quality of life and survival. The phase I NANO-RAD trial assessed the safety and maximum tolerated dose of systemic administration of a novel gadolinium-based nanoparticle, AGuIX, in combination with whole brain radiotherapy in patients with multiple brain metastases not suitable for stereotactic radiotherapy.

MATERIALS AND METHODS

Patients with measurable brain metastases received escalating doses of AGuIX nanoparticles (15, 30, 50, 75, or 100 mg/kg intravenously) on the day of initiation of WBRT (30 Gy in 10 fractions) in 5 cohorts of 3 patients each. Toxicity was assessed using NCI Common Terminology Criteria for Adverse Events v4.03.

RESULTS

Fifteen patients with 354 metastases were included. No dose-limiting toxic effects were observed up to AGuIX 100 mg/kg. Plasma elimination half-life of AGuIX was similar for all groups (mean 1.3 h; range 0.8-3 h). Efficient targeting of metastases (T₁ MRI enhancement, tumor selectivity) and persistence of AGuIX contrast enhancement were observed in metastases from patients with primary melanoma, lung, breast, and colon cancers. The concentration of AGuIX in metastases after administration was proportional to the injected dose. Thirteen of 14 evaluable patients had a clinical benefit, with either stabilization or reduction of tumor volume. MRI analysis showed significant correlation between contrast enhancement and tumor response, thus supporting a radiosensitizing effect.

CONCLUSION

Combining AGuIX with radiotherapy for patients with brain metastases is safe and feasible. AGuIX specifically targets brain metastases and is retained within tumors for up to 1 week; ongoing phase II studies will more definitively assess efficacy.

Clinical trial design in brain metastasis: approaches for a unique patient population

Clinical trials in brain metastases present challenges and opportunities unique to this patient population. With the increase in awareness and screening for brain metastases, smaller and often asymptomatic lesions are detected, creating the opportunity for trials of pre-irradiation chemotherapy. The goal of earlier intervention is advanced by studies to prevent brain metastases in high-risk populations. Sequencing of systemic chemotherapy with experimental chemotherapy in the context of a clinical trial requires collaboration between the investigators and the treating medical oncologists beginning ideally during design of the study. Adaptive randomization improves the efficiency of randomized trials in the brain metastasis population. Finally, collaborative efforts between patients and physicians with the support from patient advocacy groups will help advance the quality and the clinical trial options for patients with brain metastases.