PROTACs: A promising strategy in Drug Development

Thanks to its capability to recruit the natural protein degradation system of a cell, PROTACs (PROteolysis TArgeting Chimera) appears as a very promising technology in cancer therapy and disease treatment. As a distributor of innovative reagents for life science researchers, tebu-bio provides you with all the necessary tools to develop or test your own PROTACs system.

In Drug Development, most of the strategies are based on the use of antibodies, siRNA and small molecules to inhibit the activity of specific proteins involved in diseases. Despite undeniable recognized advantages, such molecules can present some drawbacks such as size and cell permeability for antibodies or delivery and off-target issues for siRNA. Even small molecule inhibitors need high exposure to achieve sufficient protein inhibition and can cause toxic side effects and drug resistance.

Spurred by the fact that, during critical mutations of proteins (such as RAS protein), tumourigenesis events can occur and complicate the design or identification of inhibitory molecules, in the last few years researchers have been more focused on strategies to degrade the targeted proteins rather than trying to inhibit their activities. Among all the strategies developed, one has emerged as the most promising: the PROTACs.

About PROTACs

The PROTACs (PROteolysis TArgeting Chimera) technology, uses the natural Ubiquitin / Proteasome system to degrade the disease targeted protein.

As shown in figure 1, PROTACs are bifunctional molecules, composed of three parts. A specific E3 ligand to recruit the E3 ligase and the cellular Ubiquitination machinery, a ligand (small molecule) to link specifically to the targeted protein, and a PEG linker to connect the two ligands. By the binding of each ligand to their targets, the PROTACs will form a ternary complex, bringing the E3 ligase to the proximity of the targeted disease proteins. Thereafter, the E3 ligase will recruit an E2 conjugated enzyme, and the complex will poly-ubiquitinate the targeted protein. This poly-ubiquitination will lead it to the cells proteasome system for its degradation, while the PROTACs complex (not degraded by the proteasome) dissociates from the proteins and will initiate a new catalytic cycle with a new targeted protein (fig. 2).

Thanks to its very promising potential in Drug Development, the first PROTACs molecules are now under clinical trial, led by an anti-prostate cancer candidate (developed by Arvinas), or collaboration between Arvinas and Pfizer to bring to the clinic a breast cancer PROTAC molecule.
Recent studies have underlined the importance of ligands and linker optimization to get the best PROTAC solution for a stable ternary complex formation, and an efficient disease targeted protein degradation. Finally, even if many companies and research labs have already started active protein degradation programs, the PROTACs research field is only at its beginning.

PROTACs design and optimization

As a provider of Innovative Reagents and solutions for Life Science researchers, tebu-bio can provide you with high-quality solutions for all the development steps of your PROTACs molecule.

From the design…

Thanks to a broad network of suppliers around the world, tebu-bio can provide all the different elements (from the ligands to the linkers) you need to develop your PROTACs model.

A full list of chemical compounds linked to Ubiquitin and Proteasome, from Focus Biomolecules:

• E3 Ubiquitin Ligase
• Proteasome inhibitors or substrates
• E1 ubiquitin inhibitors

Focus Biomolecules have also launched a program to produce and offer an already made protein degrader (for BRD4..) and in the near future a full set of building blocks for rapid production of PROTACs molecule.

BPS Bioscience, specialized in many research fields such as Immunotherapy, CAR-T cell therapy, Neuroscience, and many others, have also developed a full offer of PROTACs solutions composed of:

• E3 Ubiquitin Ligase complex
• Bromodomains, kinases and Ubiquitins recombinant proteins
• and also small molecule inhibitors and ligands.

And finally, tebu-bio can offer you more than 2000 high purity PEGylation products, and click chemistry solutions to find the best linker for your PROTACs model, allowing an optimal ternary complex formation and protein degradation. As a worldwide leading PEG supplier, BroadPharm can also perform a custom synthesis of PEG products depending on your specific needs.

… to the test to assess PROTAC’s efficiency.

Evaluating the capability of your PROTACs molecule to recruit the E3 ubiquitin Ligase, but also the targeted protein, is crucial. For this purpose, BPS Bioscience have developed an assay to evaluate the PROTACs efficiency in recruiting BET Bromodomain family and Cereblon (CRBN), which is a substrate recognition component of a BDX E3 protein ligase complex (mediate the ubiquitination steps) (Fig. 5). Provided as a convenient AlphaLISA format, this PROTAC Optimization Kit (composed of Cereblon FLAG tag and BRD3 (BD2 GST tag recombinant protein), will allow you to test your PROTACs molecule targeting BRD3 proteins, design new molecules targeting CRBN, and also compare the activities of different PROTACs molecule.

Already known as an expert in the detection of the ubiquitylation of your target proteins thanks to their TUBEs (Tandem Ubiquitin Binding Entities) technology (more information on our blog – Fig. 6), LifeSensors also have a number of commercially available PROTACs solutions. More than providing compounds and tools such as building blocks, LifeSensors have also developed a full offer of plate-based format assays to measure the ubiquitylation of a protein.

• Ubitest: Based on Tube technology, this test platform replaces traditional immuno-blotting methods for measuring cellular ubiquitylation.
• ELISA-Based in-vitro Ubiquitylation Assay
• Ubiquant ELISA and AlphaLISA: Based on the Tube technology, this assays allows the quantitative measurement of PROTACs’ effect on a targeted protein.

Ranging from throughput from immunoblot to 384-well formats, LifeSensors assay concepts can be readily adapted for a vast range of applications on a custom basis and accelerate the process of PROTAC-based drug discovery.

Interested in developing your own PROTACs Model? Or you would like to benefit from these tools to optimize your model?

Contact your local tebu-bio office for more information and advice in finding the right solutions optimized for your research.