A Potent and Specific Approach to Targeting B-Cell Lymphoma: Disrupting Malignant Protein-Protein Interactions Using CD19-Targeted Stapled Peptide Amphiphile Nanoparticles

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PROJECT SUMMARY/ABSTRACT This project seeks to engineer a potent, specific, and clinically relevant treatment platform to target B-cell lymphoma, which is often refractory to chemotherapeutic treatments. To accomplish that goal, this project develops a peptide-based nanoparticle platform for disrupting oncogenic protein-protein interactions (PPIs) and inducing cell death specifically in lymphoma B cells without targeting other cells. Cancer cells often upregulate pro-survival PPIs to sequester and inactivate tumor suppressor proteins and evade programmed cell death, which is one of the hallmarks of cancer. Despite intensive pharmacologic efforts to target and disrupt oncogenic PPIs, only one FDA-approved small-molecule drug exists to do so. Synthetic peptides, in contrast, have emerged as promising tools for disrupting PPIs because they more accurately mimic the large, alpha- helical binding domains known to be crucial for many PPIs. However, major barriers remain to successful in vivo delivery of therapeutic peptides to their intracellular targets, including: (i) short circulation half-lives, (ii) non-specific cellular targeting, (iii) poor cellular penetration, and (iv) poor binding affinity due to loss of alpha- helical secondary structure. Two molecular engineering approaches, hydrocarbon “stapled” peptides and peptide-amphiphile (PA) nanoparticles, have been used to overcome subsets of these obstacles, though neither overcomes them all simultaneously. Hydrocarbon stapled peptides are formed by adding a hydrocarbon “staple” across alpha-helical turns of a peptide to physically lock it in an alpha-helical conformation and more accurately mimic the structure of the native protein and improve binding affinity to its target. PA nanoparticles, meanwhile, enhance therapeutic peptide circulation times, serum stability, and cellular uptake, and can be functionalized with targeting moieties to actively target specific cell types. This project seeks to simultaneously overcome the barriers to therapeutic peptide delivery by combining hydrocarbon stapled peptides and PA nanoparticles. This work aims to do so in three ways. First, synthesize and characterize a p53-mimicking stapled PA (p53-sPA) designed to reactivate tumor suppressor protein p53 and reinstate cell death in diffuse large B cell lymphoma (DLBCL), a cancer in which most clinical cases have wildtype p53 inactivated by aberrant PPIs. Second, deliver p53-reactivating nanoparticles specifically to malignant DLBCL cells using antibody single-chain variable fragments (scFvs) specific for B-cell surface antigen CD19. Lastly, combat chemotherapeutic resistance in DLBCL using mixed PA nanoparticles to spatially constrain the delivery of synergistic peptide therapeutics targeting the p53 and BCL2 pro-survival PPIs. The success of these aims will create a new treatment paradigm for potently and specifically killing cancer cells while avoiding the development of chemotherapeutic resistance.