DARPins: Promising Scaffolds for Theranostics

Abstract

Monoclonal antibodies are the classical basis for targeted therapy, but the development of alternative binding proteins has made it possible to use non-immunoglobulin proteins as targeting modules. The advantages of DARPins, scaffold proteins based on ankyrin repeats, over antibodies are as follows: small size, stability over a wide range of temperatures and pH values, low aggregation tendency, and ease of production in heterologous expression systems. The differences in the structure of the paratope of DARPin and antibodies broaden the spectrum of target molecules, while the ease of creating hybrid fusion proteins allows one to obtain bispecific and multivalent constructs. In this article, we summarize recent data on the development of therapeutic and imaging compounds based on DARPins.

Resources and Methods for Engineering “Designer” Glycan-Binding Proteins

“…As high-throughput protein engineering methods become more common, future efforts may provide protein scaffolds for GBP engineering that bind glycans with higher affinity and avidity than what is currently available. Recently, designed ankyrin repeat proteins (DARPins) have been produced as highly stable, small molecular weight, modular scaffolds [ 120 ]. DARPins are based on ankyrin proteins, some of which have glycan binding pockets [ 121 ]; however, as of 2020, DARPins have yet to be used for GBP engineering.…”

Natural and Designed Toxins for Precise Therapy: Modern Approaches in Experimental Oncology

“…Over time, the variety of toxins used in the design of targeted therapy has grown [ 17 , 18 ], but the next breakthrough was made due to molecular cloning, which allowed for the production of the third-generation immunotoxins: fusion proteins consisting of antibody fragments linked to enzymatically active toxin domains [ 5 , 19 ]. Antibodies are mostly used in a single-chain form (scFv); however, over the past 20 years, a variety of nonclassical antibodies have been introduced in biotechnology [ 1 ], as well as scaffold proteins of different origin [ 2 , 20 ].…”

“…If a toxin has natural tropism to surface molecules of human cells, the receptor-binding domains are usually removed. Cancer antigen targeting is usually provided by antibodies, antibody fragments or alternative scaffolds [ 1 , 2 ]. Proper tumor accumulation can be achieved by the selection of targeting molecules with high affinity to the antigen, though the optimal range of affinity can depend on the biology of the target.…”

“…Protein toxins possessing such features as high cytotoxicity and efficiency have become promising components for anticancer therapy. Cancer cells frequently upregulate surface receptors that promote growth and survival, that is why various antigen-specific proteins including antibodies, antibody fragments (e.g., Fab and scFv), and other protein scaffolds (e.g., affibody and DARPin) have been developed as a moiety to target cancer cells [ 1 , 2 ]. Being genetically encoded, toxins can be expressed as fusion proteins with targeting moieties mentioned above and can have a wide range of modifications to prolong circulation in the bloodstream and increase tumor retention.…”

Near-infrared activated cyanine dyes as agents for photothermal therapy and diagnosis of tumors

“…In recent years, phototherapy has significantly advanced thanks to the use of lasers as light sources; nano-objects for the delivery of sensitizers [ 10 - 13 ]; targeted dyes [ 14 , 15 ]; increased dye circulation time in the blood [ 16 ]; and sustained release of dyes [ 17 ]. Also, conjugation of dyes with immunoadjuvants is promising in photoimmunotherapy because it leads to the triggering of a systemic immune response [ 18 ].…”