A Novel Spirocyclic Dimer (36-286) Targeting the NF-Kappa B Pathway Displays Potent Anti-Tumor Properties in Chronic Lymphocytic Leukemia

Introduction: Chronic lymphocytic leukemia (CLL) is an incurable, heterogenetic disease dependent on B cell receptor (BCR) signaling with subsequent nuclear factor-kappa B (NF-κB) activation resulting in the evasion of apoptosis and enhanced malignant B cell growth. Targeted therapies such as ibrutinib (IBR; BTK inhibitor) and venetoclax (VEN; BCL2 antagonist) have revolutionized the management of CLL, however ~20% of patients relapse, signifying the urgent need for novel therapeutics for CLL patients especially those with refractory/relapse (ref/rel) disease. Additionally, various tumor microenvironment (TME) stimuli fuel CLL growth and contribute to drug resistance through the activation of numerous signaling pathways (BCR, CD40R, TLR, BAFFR) and consequential sustained NF-κB activation. Currently, there are no FDA approved drugs that effectively target the NF-κB protein family. Herein we introduce 36-286 (N3), a novel spirocyclic dimer which displays NF-κB inhibitory activity and elicits potent anti-leukemic properties. N3 is a dimer of a spirocyclic α-methylene-γ-butyrolactone analog that covalently binds to surface exposed cysteine residues on NF-κB proteins (IKKβ and P65) (Rana S et al, 2016). Our study aims to investigate N3's mode of action (MOA) and to establish its anti-leukemic effects in CLL including drug-resistant disease, thereby introducing a novel therapeutic option for rel/ref disease.