Targeted delivery of a human Bcl-2-specific protein binder effectively induces apoptosis of cancer cells

Variable Lymphocyte Receptor B Technologies - Are They Ready for Prime Time?

OBJECTIVE

To review the current and the potential research and clinical use of VLRBs.

METHODS

A literature search was conducted for English studies published in the past 20 years using the terms "Variable Lymphocyte Receptor," "VLR," "VLRB" or "Repebody." Only primary reports were included.

RESULTS

VLRB-based technologies are currently being investigated for diagnosis, imaging, and treatment of diverse conditions including solid organ and hematological malignancies, infectious diseases, autoimmunity, and degenerative and metabolic disorders. VLRB mAbs can be used to directly recognize disease biomarkers, such as B cells from chronic lymphocytic leukemia, or to deliver drugs to the brain or cancer cells. The VLRB C-terminal multimerization domain has been utilized to create vaccines while VLR-based chimeric antigen receptor (CAR) T cell constructs are being investigated for cancer therapies.

CONCLUSIONS

The extensive knowledge gained with VLRB mAbs in diverse in vitro and in vivo models emphasizes their promise for translation into clinical applications and readiness for prime time.

Intracellular protein delivery: New insights into the therapeutic applications and emerging technologies

The inability to cross the plasma membranes traditionally limited the therapeutic use of recombinant proteins. However, in the last two decades, novel technologies made delivering proteins inside the cells possible. This allowed researchers to unlock intracellular targets, once considered 'undruggable', bringing a new research area to emerge. Protein transfection systems display a large potential in a plethora of applications. However, their modality of action is often unclear, and cytotoxic effects are elevated, whereas experimental conditions to increase transfection efficacy and cell viability still need to be identified. Furthermore, technical complexity often limits in vivo experimentation, while challenging industrial and clinical translation. This review highlights the applications of protein transfection technologies, and then critically discuss the current methodologies and their limitations. Physical membrane perforation systems are compared to systems exploiting cellular endocytosis. Research evidence of the existence of either extracellular vesicles (EVs) or cell-penetrating peptides (CPPs)- based systems, that circumvent the endosomal systems is critically analysed. Commercial systems, novel solid-phase reverse protein transfection systems, and engineered living intracellular bacteria-based mechanisms are finally described. This review ultimately aims at finding new methodologies and possible applications of protein transfection systems, while helping the development of an evidence-based research approach.

Dissecting the impact of target-binding kinetics of protein binders on tumor localization

Systematic control of in vivo behavior of protein-based therapeutics is considered highly desirable for improving their clinical outcomes. Modulation of biochemical properties including molecular weight, surface charge, and binding affinity has thus been suggested to enhance their therapeutic effects. However, establishing a relationship between the binding affinity and tumor localization remains a debated issue. Here we investigate the influence of the binding affinity of proteins on tumor localization by using four repebodies having different affinities to EGFR. Biochemical analysis and molecular imaging provided direct evidence that optimal affinity with balanced target binding and dissociation can facilitate deep penetration and accumulation of protein binders in tumors by overcoming the binding-site-barrier effect. Our findings suggest that binding kinetics-based protein design can be implicated in the development of fine-tuned protein therapeutics for cancers.

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High binding affinity limits the tumor localization of protein binders in vivo

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Moderate-affinity binders can exhibit better tumor localization than higher binders

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Binding kinetics of binders play a central role in controlling tumor localization

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Exploring the optimal affinity of binders can enhance their therapeutic potential