Sonodynamic Therapy With ExAblate System in Glioblastoma Patients

Despite progress made in many cancer treatments, High-Grade Gliomas (HGG) remain an extraordinary challenge. Their aggressive and infiltrative nature, the limited efficacy and inherent risk of surgical resection combined with radiotherapy, and the difficulty in delivering anticancer drugs to the brain, make the prognosis for patients with gliomas grim. Therefore, new and less-invasive alternatives to existing procedures are needed.

Sono-Dynamic Therapy (SDT) represents an emerging approach that offers the possibility of noninvasively eradicating solid tumors in a site-directed manner. It involves the delivery of a non-toxic chemical agent that selectively accumulates into target areas and the subsequent exposure of the targeted tissue to relatively low-intensity ultrasound. These procedures (sensitization and ultrasound exposure) are both per se harmless, but, when combined, result in activation of the chemical agent and subsequent cytotoxic events limited to the target tissue volume. SDT offers significant advantages because ultrasound energy can be tightly focused and delivered through the intact skull to deep areas of the brain, depending on the frequency. SDT is achieved by focusing low-intensity and lowfrequency ultrasound, which, as opposite to high-intensity ultrasonic beams, can be focused effectively within the whole intracranial space with the currently available device ExAblate 4000, Insightec, Haifa, Israel). This would enable to target also tumors in the peripheral area of the intracranial space. 5-ALA is a PpIX (Protoporphyrin IX) precursor that selectively accumulates in HGGs because of an enhanced uptake and metabolism from tumor cells. It is used for intra-operative guidance in surgery as tumoral tissues shows an exceeding fluorescence under certain light conditions due to PpIX accumulation, as compared to the normal surrounding parenchyma. It is therefore a good candidate for SDT. 5-ALA can exert sono-dynamic effects against HGGs, as it has been shown in several preclinical studies. Pre-clinical data on a safety experiment conducted at the University of Virginia showed that SDT with 5-ALA was not exerting a toxic effect to the normal brain [Raspagliesi L. et al. 2021].

The idea of the present study is to investigate the antitumor effects of SDT in patients affected by HGGs attained with low-frequency Focused Ultrasound. Focused Ultrasound under MRI-guidance can be safely delivered through an intact human skull to perform SDT in combination with 5-ALA with a low risk of transient adverse effects, and will be evaluated during follow-up visits, postprocedural serial MRI, and histology.

The main goal of this prospective, non-randomized, single-arm study is to evaluate the safety and feasibility of SDT in patients with newly diagnosed cerebral glioblastomas using the ExAblate Model 4000 Type-2 "Neuro-System". The ExAblate Model 4000 Type-2 "Neuro-System" is intended for use as a tool to induce targeted tumor's inhibition of growth and cell destruction in patients with cerebral lobar glioblastomas.

Patients harboring newly diagnosed lobar glioblastoma according to RANO criteria will provide informed consent, will be screened, and will undergo study SDT treatment using the ExAblate Model 4000 Type-2 "Neuro-System". After SDT treatment, patients will perform a strict neuro-radiological follow-up (minimum of 2 MRI) and undergo tumor resection about 15-21 days after SDT, according to the clinical and radiological status.

The main purpose of this study is to evaluate the safety and feasibility of SDT. In particular, safety will be evaluated by patient examination and MRI during the treatment, and by follow-up by daily clinical visits and MRI every 5 (± 2) days according to clinical and radiologic findings. Safety data will be assessed during each visit through a combination of MRI evaluations, clinical assessments, and neurological examinations, according to the clinical findings assessed until the decision to proceed with surgical resection. Feasibility will be evaluated performing 4 MRI (Day 1, 5, 10, 15) after SDT treatment evaluating tumor size, morphology and perilesional edema until tumor resection.

A secondary objective of the present study is to assess the efficacy of the treatment; in particular, to investigate the antitumor effects of SDT in patients affected by HGGs attained with low-frequency

Focused Ultrasound, the following data will be collected:

• Tumor volume changes after SDT according to sonicated tumors volumes (by imaging).
• Histology after tumor resection, comprising assessment of apoptosis and necrosis.

Despite all current treatment modalities, glioblastoma patient's prognosis remains dismal. By proving that procedure is safe and feasible this study will establish the SDT treatment modality as a possible alternative or a synergistic tool to current treatment modalities. It will also pave the way to the application of SDT in other forms of brain tumors, both intra- and extra-axial, and to the development of tumor specific sono-sensitizers.