In a new study published in Nature Communications, scientists have developed mirror-image monobodies targeting the BCR::ABL1 tyrosine kinase, a driver of certain types of leukemia. These findings mark a significant advancement in the development of D-protein therapeutics, which are composed of D-amino acids, offering unique advantages such as high metabolic stability and reduced immunogenicity.
The researchers employed an innovative approach to create these mirror-image monobodies. Using chemical synthesis, they first developed d-versions of the SH2 domain of BCR::ABL1, enabling the selection of L-binders from phage display libraries. These L-binders were then chemically synthesized into their mirror-image d-binders, which bind effectively to the physiological L-target. This process represents a significant step forward in creating therapeutics that are resistant to proteases and exhibit prolonged plasma stability.
Key Findings:
- High-Affinity Binding:
The synthesized d-monobodies demonstrated nanomolar binding affinities to the SH2 domain of BCR::ABL1. Their proper folding, stability, and ability to bind effectively to L-targets were confirmed through structural and functional analyses. - Unique Binding Mechanisms:
Crystal structures revealed unconventional binding modes of the monobodies, including targeting the phosphotyrosine (pY) pocket using glutamate residues. The study identified five distinct SH2 binding modes across previous and current research, highlighting the versatility and selectivity of monobody interactions. - Therapeutic Potential:
The d-monobodies inhibited BCR::ABL1 kinase activity and demonstrated their capability to bind BCR::ABL1 in both cell lysates and permeabilized cells. This opens doors to their potential application in leukemia treatment. - Efficient Synthesis Strategy:
The team developed a two-piece synthesis strategy for D-monobodies, allowing for faster development, reduced purification steps, and retained high-affinity binding. This approach could simplify the production of future d-protein therapeutics.
Broader Implications:
The study underscores the promise of monobodies as a robust platform for developing d-protein therapeutics due to their small size, lack of disulfide bonds, and adaptability to diverse target topologies. Additionally, the researchers highlighted the potential of mirror-image biological systems, pointing to advances in synthesizing mirror-image DNA polymerases, RNA polymerases, and ribosomes, which could eventually enable self-replicating mirror-image biological systems.
Future Directions:
Key next steps involve investigating the pharmacokinetics and biodistribution of D-monobodies in vivo, optimizing intracellular delivery methods, and exploring their stability in cellular environments. The team is also working on recombinant “supercharged” L-monobodies for cellular delivery, aiming to translate these findings into clinical applications.
This study represents a pivotal advance in mirror-image protein therapeutics, paving the way for innovative cancer treatments and expanding the therapeutic possibilities for targeting previously challenging molecules.