Ligand Design for BRD4-targeting PROTAC^®

Creative Biolabs has knowledgeable and friendly customer services and technical support teams with many years of experience in the life sciences industry. Our powerful technology is designed to overcome the innate challenges of targeted protein degradation leveraging our broad knowledge of the ubiquitin-proteasome system to remove disease-causing proteins. Based on our powerful target protein degradation platform, we are confident to be a competent and trustworthy partner for your research and scientific projects.

About PROTAC^®

Currently, proteolysis-targeting chimeras (PROTAC^®s) have become a promising and attractive technology for modulating a protein of interest (POl) by degradation. PROTAC^® is a heterobifunctional molecule that connects a POl ligand to an E3 ubiquitin ligase (E3) recruiting ligand with an optimal linker. Degradation is initiated when PROTAC^® forms a ternary complex with POI and E3. Thereafter, subsequent ubiquitination of POI occurs, and then ubiquitinated POI is recognized and degraded by the 26S proteasome, which is part of the ubiquitin-proteasome system (UPS) in eukaryotic cells (Fig.1). PROTAC^® works in conjunction with the UPS system to achieve the regulation of protein levels.

Fig.1 Mode of action of PROTAC^®s. (Sun, 2019)

BRD4-targeting PROTAC^®

BRD4, a member of the bromodomain and extra-terminal domain (BET) family, links acetylated histones and transcription factors to the assembled transcriptional apparatus at specific cis-regulatory elements. It plays a vital role in the proliferation of cancer cells by regulating the expression of oncogenes, such as c-myc, bcl-xL, and bcl-6, and is therefore an attractive target for cancer treatment. The following are two examples of PROTAC^® targeting BRD4.

• The PROTAC^® ARV-825 is generated by coupling a BRD4-binding moiety (OTX015) with pomalidomide by a linker to induce efficient ubiquitination and proteasomal degradation of the BRD4. It can mediate the rapid degradation of BRD4, resulting in suppression of proliferation and induction of apoptosis in Burkitt’s lymphoma cell lines. In addition, ARV-825 almost completely degrades BRD4 at 10 nM within 6 hours, and maintains BRD4 degradation and downstream effects for up to 24 hours. These results indicated that PROTAC^® technology has great potential for the pursuit of effective therapeutics and significant improvement in drug development strategies.

• Small molecule BRD4 inhibitor JQ1 is conjugated to a thalidomide derivative to construct another PROTAC^®, named dBET1. BRD4 is completely degraded after 2 hours of treatment with 100 nM dBET1 in acute myeloid leukemia cells. Moreover, after 14 days of administration of dBET1 to tumor-bearing mice, tumor progression is significantly attenuated. Taken together, these results indicate that dBET1 can be a useful tool for therapeutic drug development.

Fig.2 Chemical structures of PROTAC^® ARV-825 and dBET1. (Gu, 2018)

Ligand Design for BRD4-targeting PROTAC^® at Creative Biolabs

Creative Biolabs has an experienced team of biologists and chemists. Led by outstanding scientists, our team is able to support various ligand designs that target BRD4, including small molecules, peptides, proteins, and antibodies, etc. In addition, we provide a variety of modifications and other strategies to increase the selectivity and potency of PROTAC^®, including adjusting the length and composition of the linker, changing the binding ligand to the target protein and/or E3 ligase, and changing the choice of recruited E3 ligases. With rich experience in molecular discovery, we can provide ligand designs with the following characteristics faster than other companies:

• Induced remarkable degradation of target proteins at micromolar concentrations
• Rapid and sustained depletion of target proteins
• Rapid, sustained, and robust inhibition of downstream signaling cascades
• Overcome drug resistance due to mutations
• High specificity for their target proteins
• Modifying the potency and selectivity

Creative Biolabs has a set of mature molecular discovery processes that cover all stages of PROTAC^® and offer professional after-sale services to achieve customer satisfaction. If you want to know more, please feel free to contact us and we will be happy to discuss our design services to help you.

References

1. Sun, X.; et al. PROTAC^®s: great opportunities for academia and industry. Signal Transduction and Targeted Therapy. 2019, 4(1): 1-33.
2. Gu, S.; et al. PROTAC^®s: an emerging targeting technique for protein degradation in drug discovery. BioEssays. 2018, 40(4): 1700247.