A groundbreaking development in peptide drug discovery is on the horizon, as researchers at the University of Bath have created a novel bacterial platform that can produce, stabilize and test millions of peptides in a single experiment. This innovative approach addresses longstanding challenges in the field of peptide therapeutics, which are gaining traction due to significant advancements, including the success of weight loss drugs such as semaglutide and tirzepatide. With over 80 peptide medications currently available and many more undergoing clinical trials, the peptide therapeutics market is anticipated to reach $68.83 billion by 2028.
Peptides, known for their therapeutic potential, often face hurdles due to their structural flexibility, susceptibility to enzymatic degradation, and difficulty in cellular entry. One promising strategy to enhance peptide stability is known as peptide stapling—a technique that chemically locks peptides into a stable conformation. Despite its advantages, the discovery process for potent and drug-like peptides remains cumbersome and resource-intensive, typically involving multiple synthesis and purification steps. The new approach from the University of Bath simplifies this process significantly.
Published in the journal Cell Chemical Biology, the researchers have harnessed bacteria to streamline the drug discovery process. By enabling bacteria to produce, chemically stabilize, and evaluate millions of peptide molecules within living cells, this method offers a faster, cleaner, and more scalable route for identifying potential therapies, particularly for targets that have historically eluded conventional drug development.
Revolutionizing Drug Discovery with Bacteria
The innovative bacterial platform employs stapled peptides—chemically constrained molecules that retain a stable, biologically active shape. Typically, peptides adopt specific structures to bind their targets, but outside the cellular environment, they can lose this structure, which limits their therapeutic efficacy. Jody Mason, a senior author of the study and biochemist at the University of Bath, explained, “Many biologically active peptides adopt an alpha-helical structure when they bind their targets, but in solution they often flop around and lose that structure. By inserting a chemical crosslink, known as a staple, between two residues, One can stabilize the helix.” This stabilization enhances binding affinity to targets, increases resistance to degradation, and improves cellular entry potential, thereby transforming less effective peptides into more drug-like candidates.
In this system, the production of stapled peptides occurs directly inside living bacterial cells. Instead of the conventional method of synthesizing peptides and then stapling them, the researchers integrated the stapling reaction into the cellular screening process. This allows the biological environment to select both the peptide sequence and the optimal geometry for stability simultaneously. Peptides are expressed in bacteria as part of genetically encoded libraries, with each cell generating a unique peptide sequence. The addition of small bis-alkylating molecules facilitates the reaction with engineered cysteine residues, creating the staple and cyclizing the peptide within the cell.
Enhancing Discovery Efficiency
This novel approach enables the simultaneous generation of millions of peptide candidates within the bacteria, significantly accelerating the discovery process. It eliminates the need for complex, multi-step synthesis and purification, which has traditionally slowed down peptide drug development. This method is more environmentally friendly and scalable, promising to enhance peptide therapeutic discovery beyond the capabilities of conventional laboratory techniques.
The effectiveness of this platform is further exemplified through the use of the Transcription Block Survival (TBS) assay, which connects peptide activity directly to bacterial survival. In this setup, bacteria are engineered so that a transcription factor, which the research team aims to inhibit, blocks the expression of an essential gene. If the transcription factor is active, the bacteria cannot grow. However, if a peptide successfully inhibits this factor, the cell can grow, highlighting the peptide’s potential effectiveness.
Mason noted that the TBS assay efficiently filters out peptide sequences that are unstable, non-specific, toxic, or poorly expressed. “Only peptides that are stable, functional, and able to selectively engage the target inside the cell allow their host cells to grow,” he explained. This streamlined process not only increases discovery speed but similarly ensures that the identified peptides are more likely to be effective in human cells, as they must survive within a living cellular environment.
Targeting Challenging Proteins
The researchers demonstrated the platform’s potential by targeting CREB1 (cAMP responsive element binding protein 1), an oncogenic transcription factor involved in various cancers. CREB1 regulates genes that control cell proliferation, survival, and metastasis, making it a high-priority target, albeit one historically deemed “undruggable.” Mason indicated, “Transcription factors like CREB1 are often considered undruggable because their interaction surfaces are challenging for small molecules to target.” The screening process yielded cyclic peptides with nanomolar binding affinity that successfully disrupted the CREB1-DNA interaction. When made cell-permeant, the lead peptide inhibited CRE-dependent transcription and reduced cancer cell viability.
After identifying promising peptides within the bacterial system, the team synthesized and evaluated them in biochemical and cellular assays. The results confirmed that these peptides effectively bind to CREB1, disrupt protein-DNA interactions, and selectively induce cancer cell death in laboratory settings.
A New Era for Peptide Therapeutics
This pioneering work at the University of Bath marks a significant advancement in the discovery and optimization of peptide therapeutics. By leveraging biological processes to identify the most functional peptides, the platform can explore millions of candidates in one experiment, vastly enhancing the efficiency of drug discovery.
Mason expressed optimism about the implications of this technology, stating, “This technology opens up completely new ways to move after cancer targets that have long been considered undruggable.” The adaptability of this core technology means it can potentially target a wide array of protein interactions, paving the way for advancements in oncology, infectious diseases, and other therapeutic fields.
As researchers move toward testing their peptides in more complex tissue models and animal studies, this bacterial platform stands as a promising blueprint for next-generation peptide therapeutics. By marrying scalability, flexibility, and in-cell validation, it has the potential to transform the landscape of drug discovery, providing novel solutions for diseases that have long defied traditional therapies.
As the field of peptide therapeutics evolves, the implications of this research could be profound, offering new tools to tackle some of medicine’s most challenging targets. Interested readers are encouraged to engage in discussions about the future of peptide drugs and share their thoughts.
Disclaimer: This article is for informational purposes only and does not constitute professional medical advice.
