Targeted degradation of BRD4 by PROTACs: advances in cancer therapy

Area of Science:

• Oncology
• Molecular Biology
• Drug Discovery

Background:

• Bromodomain-containing protein 4 (BRD4) is a significant oncogenic driver in various cancers.
• Existing BRD4 inhibitors face challenges including resistance, toxicity, and poor isoform selectivity.
• Proteolysis-targeting chimera (PROTAC) technology presents a promising alternative for targeted protein degradation.

Purpose of the Study:

• To review advancements in BRD4-targeting PROTACs for cancer therapy over the last decade.
• To explore strategies for optimizing ternary complex design, bioorthogonal activation, and delivery systems for BRD4 PROTACs.
• To highlight the potential of PROTACs in overcoming limitations of conventional BRD4 inhibitors.

Main Methods:

• Systematic review of literature on BRD4-targeting PROTACs.
• Analysis of PROTAC design strategies including ligand integration (JQ1, ABBV-075, HJB97), macrocyclization, and dual-targeting.
• Examination of bioorthogonal activation methods (photocaging, chemical induction) and precision delivery systems (antibody-PROTACs, folate-PROTACs).

Main Results:

• PROTACs induce BRD4 degradation via the ubiquitin-proteasome system by recruiting BRD4 and E3 ligases (CRBN, VHL, MDM2, DCAF).
• Optimized PROTAC designs, including macrocyclization and dual-targeting, enhance potency and isoform selectivity.
• Bioorthogonal activation and advanced delivery systems mitigate off-target toxicity and improve therapeutic precision.

Conclusions:

• BRD4-targeting PROTACs represent a significant advancement in cancer therapy, offering targeted degradation of an oncogenic driver.
• Multidimensional optimization of PROTACs is driving their clinical translation.
• These novel degraders promise safer, more effective, and precisely controllable cancer treatment strategies.