PROTAC ligands are essential molecular building blocks of PROteolysis-Targeting Chimeras (PROTACs)—a rapidly growing class of small-molecule therapeutics designed to eliminate disease-causing proteins rather than temporarily inhibit them.
A PROTAC is a heterobifunctional molecule composed of two ligands connected by a chemical linker. One ligand binds a protein of interest (POI), while the other recruits an E3 ubiquitin ligase, enabling selective and catalytic protein degradation via the proteasome.
PROTACs function through a well-defined degradation mechanism, including simultaneous binding of the protein of interest and an E3 ligase, target ubiquitination, proteasomal degradation of the target protein, andPROTAC release and reuse.
Because activity is driven by protein elimination rather than occupancy, PROTACs often outperform conventional inhibitors in resistant disease settings.
PROTAC technology has been clinically validated in prostate cancer PROTAC development with BMS-986365, a first-in-class CRBN PROTAC engineered as a dual androgen receptor (AR) degrader and antagonist (see Figure 1).
Figure 1. BMS-986365: AR degrader via CRBN-mediated ubiquitination
This optimized AR degrader demonstrated:
These results establish CRBN-based PROTAC ligands as clinically relevant tools for overcoming AR pathway resistance.
PROTAC chemistry is also enabling novel immunotherapy strategies. In Targeted Antigen Degradation Tumor Vaccines (TAgD-TVac), tumor antigens are conjugated to VHL-based PROTAC ligands (see Figure 2) to accelerate proteasome-dependent degradation and MHC-I cross-presentation.
Figure 2. Tumor antigens functionalized with AHPC analog, supplied by BroadPharm, for targeted E3 ligase recruitment.
Using the VHL ligand (S,R,S)-AHPC, antigen-ligand conjugates demonstrated:
This approach highlights how VHL-based PROTAC ligands can extend protein degradation strategies beyond direct oncology targets.
As a worldwide leading supplier of PROTAC ligands and bioconjugation linkers, BroadPharm provides a comprehensive catalog to support PROTAC discovery and optimization:
Nayak, S., Norris, J. D., Ammirante, M., Rychak, E., Wardell, S. E., Liao, D., ... & Xu, S. (2026). Discovery of BMS-986365, a first-in-class dual androgen receptor ligand-directed degrader and antagonist, for the treatment of advanced prostate cancer. Clinical Cancer Research, 32(1), 224-241.
Zhao, Y., Song, D., Wang, Z., Huang, Q., Huang, F., Ye, Z., ... & Xu, Q. (2025). Antitumour vaccination via the targeted proteolysis of antigens isolated from tumour lysates. Nature Biomedical Engineering, 9(2), 234-248.