PROTAC BRD9-binding moiety 1 hydrochloride

Target: This ligand targets bromodomain-containing protein 9 (BRD9) in biochemical or cellular target-engagement studies.

Mechanism of Action: Used as the target-protein recognition element, this ligand provides the binding interface for bromodomain-containing protein 9 (BRD9). In PROTAC design, a derivatizable position on the ligand can be connected through an optimized linker to an E3 ligase ligand, such as a CRBN, VHL, or IAP recruiter, while preserving productive target engagement. The resulting bifunctional molecule brings bromodomain-containing protein 9 (BRD9) into proximity with the recruited E3 ligase, enabling ternary-complex formation. If the complex has favorable geometry and residence time, target lysine ubiquitination is promoted, leading to proteasome-dependent degradation in experimental systems.

• BRD9-Target Engagement: This BRD9-binding moiety 1 hydrochloride is intended for constructing PROTACs that recruit BRD9 to an E3 ligase, enabling ubiquitination and proteasomal degradation. Its use supports mapping productive ternary complex formation, optimizing linker length, and evaluating degradation efficiency relative to binding affinity in cellular systems.

• Transcriptional Repression Studies: By driving selective BRD9 degradation, PROTACs incorporating this ligand can dissect BRD9-dependent transcriptional programs. Researchers can combine degradation readouts with RNA and chromatin assays to determine how loss of BRD9 impacts enhancer regulation, cofactor recruitment, and downstream gene expression.

• Epigenetic Dependency Mapping: This ligand can be used to generate BRD9-degrading PROTACs for systematic dependency profiling across epigenetic networks. Comparing degradation potency and phenotypic outcomes across cell models helps identify contexts where BRD9 is a functional driver, supporting mechanistic studies of BET-like bromodomain biology.

• Mechanism-of-Action Validation: Incorporation of this moiety enables rigorous PROTAC mechanism studies, including dependence on proteasome activity and E3 ligase engagement. Researchers can test whether BRD9 loss correlates with ubiquitination kinetics, ternary complex stability, and recovery after washout to distinguish degradation-driven effects from occupancy-driven effects.

This BRD9-binding hydrochloride salt is designed for BRD9-directed PROTAC construction. Its acidic handle makes it suitable for linker attachment through standard coupling chemistry.

Structure: The structure is a hydrochloride salt of a BRD9-binding moiety containing a carboxymethoxyphenyl group, methoxy aryl substitution, a thienopyridinone-like heterocycle, and a sulfone-containing cyclic amidine feature. The free carboxylic acid provides a clear linker-ready handle.

Reactivity: As a BRD9-binding moiety bearing a carboxylic acid, this compound is suitable for amide coupling to amine-terminated alkyl, PEG, piperazine, or amino-acid-derived linkers. The resulting linker can be attached to CRBN, VHL, IAP, or other E3 ligase ligands through standard acid-amine coupling strategies. The aryl-heterocycle binding core should remain unmodified, and salt form should be considered during solubility and coupling-condition selection.