P07.13.b a randomized study of low-intensity focused ultrasound for blood-brain barrier disruption for brain metastasis from non-small cell lung cancer (limitless)

Abstract BACKGROUND The blood-brain barrier (BBB) limits the efficacy of systemic therapies for brain metastases (BM), for which non-small cell lung cancer (NSCLC) is the most common etiology. BBB disruption (BBBD) has been demonstrated, in preclinical models, to improve systemic drug delivery for BM. Low-intensity focused ultrasound (LIFU) results in non-invasive BBBD synergistically with intravenously (IV) administered microbubble oscillators. This randomized controlled trial (RCT) aims to determine the safety and efficacy of LIFU-mediated BBBD for NSCLC BM with immunotherapy. METHODS LIMITLESS is an ongoing prospective, multicenter, parallel-arm, open-label RCT that randomizes patients with NSCLC BM on pembrolizumab monotherapy prescribed as per standard-of-care to LIFU plus pembrolizumab (arm 1) or pembrolizumab alone (arm 2) in 2:1 ratio. Included patients have age ≥18 years, normal organ function, Karnofsky Performance Status ≥70, EGFR- and ALK-negative primary tumor, and ≤3 BM with ≥1 BM meeting measurable disease criteria as per response assessment in neuro-oncology for BM (RANO-BM). Patients on both arms receive standard-of-care therapy, while those on arm 1 also undergo LIFU before each dose of pembrolizumab (200 mg IV every 3 weeks). These patients undergo pre-treatment MRI brain, followed by IV administration of oscillating microbubbles for enhanced sonication. MR-guided BBBD is then performed using a 220 kHz LIFU device with real-time acoustic feedback for maintaining effective cavitation. Pembrolizumab is infused immediately thereafter, and a repeat MRI is done 24-48 hours later to confirm the closure of BBB each cycle. The primary study endpoint is the overall objective response rate (ORR) at 6 months, as assessed using RANO-BM criteria. Using a Bayesian design for power analysis, a superior ORR of 60% is assumed for the LIFU arm versus 30% in the control arm for a total sample size of N=96, 64 subjects in LIFU and 32 in the control arm, for 80% power using a two-sided chi-square test with an alpha of 0.05. For the upper-bound estimate ORR of 45% in the LIFU arm and 30% in the control arm, the study needs N=369 subjects; 246 in the LIFU arm and 123 in the control arm. The secondary outcomes are the best objective response rate and median time-to-response per treatment arm. The exploratory outcomes are median progression-free survival (PFS), overall survival (OS), median intracranial PFS, median extracranial PFS, and quality of life. RESULTS Patient enrollment commenced in 2022. CONCLUSION Findings from this trial will be critical to liquid biopsy in brain metastases (Clinical trial information: NCT05317858).