Abstract B008: Personalized antisense oligonucleotide treatment in a patient with relapsed NFIA :: CBFA2T3 acute myelogenous leukemia

Abstract Introduction Although driver oncogenic fusions offer an appealing therapeutic target, there is a critical shortage of targeted therapies against many fusions. Customizable direct target inhibition would address this gap. We developed an individualized antisense oligonucleotide (ASO) targeting the NFIA::CBFA2T3 fusion for a patient with relapsed acute myelogenous leukemia (AML). Diagnosed at 5 months of age with isolated central nervous system (CNS) AML, the patient underwent surgical resection, radiation therapy, and multiple rounds of systemic and intrathecal (IT)/intraventricular chemotherapy over 18 months. Ultimately, widespread leptomeningeal and extra-CNS AML progression occurred, requiring extraventricular drain (EVD) placement prior to ASO administration. We hypothesized the ASO would eliminate NFIA::CBFA2T3 fusion expression and reduce viability of fusion-bearing cells. Methods CLIA-certified whole transcriptome RNA sequencing was performed at relapse. A panel of five unique ASO constructs were designed against the NFIA::CBFA2T3 fusion breakpoint. Constructs were tested in 3 model cell lines and 1 patient-derived cell line. Neurotoxicity of the lead ASO was evaluated in NOD scid gamma (NSG) mice. A single patient IND application with a dose escalation schema received IRB and FDA approval. GMP-grade ASO (2 mg) was administered via IT injection at disease progression after informed consent was obtained. Adverse events were reported per CTCAE v5.0. Pharmacokinetic analysis on cerebrospinal fluid (CSF) and peripheral blood was performed using liquid chromatography/mass spectrometry. Results The lead ASO diminished NFIA::CBFA2T3 transcript expression by 83% in HEK293T cells expressing NFIA::CBFA2T3 and reduced cell number by 57% (p