Protein Binding Evolution: Targeting ‘Undruggable’ Proteins

For years, a significant portion of the human proteome has remained largely inaccessible to traditional drug development. These so-called “undruggable” proteins present a formidable challenge to researchers seeking new therapies for a wide range of diseases, including cancer and genetic disorders. However, recent advances are beginning to dismantle the notion of intractability, offering promising new avenues for treatment.

What Makes a Protein “Undruggable”?

Traditionally, drug discovery relies on identifying small molecules that can bind to specific pockets or active sites on a target protein, modulating its function. Many proteins, however, lack these well-defined binding pockets. As explained in a recent review, undruggable proteins often have extended and flat functional interfaces, lacking well-defined ligand-binding pockets, making it difficult for conventional drugs to gain purchase. Others simply lack specific ligands to modulate their function. Some even function as disease inhibitors, requiring a drug to activate them rather than suppress them – a counterintuitive challenge for traditional drug design.

This limitation has historically excluded a substantial number of therapeutically relevant proteins from consideration. Kinases, receptors, and channel proteins – those with clear binding sites – have been the focus of much medicinal science, leading to the development of numerous effective drugs. But what about the others?

New Strategies for Targeting the Intractable

Researchers are now employing a diverse toolkit of strategies to overcome these hurdles. One approach, highlighted in the review, involves covalent regulation, where drugs form a strong, irreversible bond with the target protein. This can be particularly effective against proteins that lack traditional binding pockets. Another strategy focuses on allosteric inhibition, targeting sites on the protein distant from the active site, which can still alter its function.

Beyond these, scientists are exploring methods to disrupt protein-protein interactions, which are crucial for many cellular processes. Interfering with these interactions can be difficult, but new techniques are emerging to identify molecules that can selectively block these interfaces. nucleic acid-based approaches – using molecules like RNA to target proteins – are gaining traction, as are immunotherapies designed to harness the body’s own immune system to attack disease-causing proteins.

The Power of Protein Degraders

A particularly exciting area of development involves protein degraders. These molecules don’t simply inhibit a protein’s function; they tag it for destruction by the cell’s natural protein disposal system. This approach offers the potential for a more complete and sustained therapeutic effect. According to recent research, protein degraders are proving effective against targets previously considered undruggable.

Understanding Protein Evolution Offers New Clues

Recent research published in 2024 suggests that understanding how protein binding sites evolve could unlock further strategies for targeting these challenging surfaces. Scientists used synthetic coevolution – engineering new interactions between proteins – to simulate the formation of protein complexes. The findings indicate that “silent” surfaces have a shallower energy landscape than natural binding sites, disfavoring tight binding. This suggests that these surfaces, while seemingly inaccessible, might be coaxed into forming more stable interactions with carefully designed molecules.

The study involved creating synthetic protein complexes and observing how they interacted. Researchers found that naturally occurring binding sites converged on a stable configuration, while synthetic interfaces explored multiple, less stable arrangements. This suggests that evolution favors tight binding, and that artificially creating such binding sites requires overcoming inherent energetic barriers.

KRAS Mutations: A Case Study in Therapeutic Challenges

The challenges of targeting undruggable proteins are particularly evident in the case of KRAS mutations, a common driver of cancer. For decades, KRAS was considered largely untreatable due to its lack of a conventional drug-binding pocket. However, recent breakthroughs have led to the development of drugs that specifically target certain KRAS mutations, demonstrating the potential of these new approaches. These advancements are not without their complexities, however, as cancer cells can evolve resistance to these therapies, highlighting the need for continued research, and innovation.

Looking Ahead

The field of “undruggable” protein targeting is rapidly evolving. While significant challenges remain, the convergence of innovative strategies – from covalent regulation and protein degraders to a deeper understanding of protein evolution – is offering renewed hope for the development of therapies for diseases that were once considered beyond reach. The ability to design molecules that bind to these previously inaccessible targets represents a major step forward in the quest for more effective and targeted treatments.

Further research is needed to refine these techniques and address potential limitations, but the progress made in recent years suggests that the era of truly undruggable proteins may be coming to an end.