PROTACAR Degrader-12 is an effective PROTAC that targets the androgen receptor (AR) co-activator binding site (AR-CBS). It induces AR degradation via the ubiquitin-proteasome system (UPS) pathway, inhibiting tumor cell growth by affecting DNA replication and cell division. Besides effectively degrading AR, it strongly inhibits the proliferation of MCF-7 cells and various mutant or drug-resistant breast cancer cells. PROTACAR Degrader-12 blocks the estrogen receptor α (ERα) signaling pathway through dual mechanisms of ERα protein downregulation and transcriptional activity inhibition, significantly suppressing mRNA expression of FOXA1, GREB1, SRC, and PELP1. It is applicable in breast cancer research.

PROTAC AR Degrader-12 (Compound 18o) demonstrates strong inhibitory activity against MCF-7 cells (IC50 = 0.13 μM) and LCC2 cells (IC50 = 0.54 μM), showing broad-spectrum efficacy against clinically relevant mutants. It effectively inhibits MCF-7 D538G (IC50 = 0.66 μM), MCF-7 Y537S (IC50 = 0.44 μM), and MCF-7 EGFR (IC50 = 0.52 μM) at submicromolar levels. In MCF-7 cells, PROTAC AR Degrader-12 (0.01-2 μM, 24 hours) degrades AR protein in a dose-dependent manner (DC50 = 0.72 μM) and exhibits time-dependent effects when used at 1 μM over 0-24 hours. It also results in concentration-dependent downregulation of ERα protein in MCF-7 cells. The compound significantly reduces ERα protein expression in MCF-7D538G, MCF-7Y537S, MCF-7EGFR, LCC2, and T47D cells, but not ERβ in PC9 cells. Additionally, at 1 μM over 24 hours, it induces reduction of ERα in MCF-7 cells through an indirect mechanism rather than direct targeting of CBS degradation. PROTAC AR Degrader-12 (0-5 μM, 0-24 hours) reduces AR protein expression via post-transcriptional degradation and inhibits ERα through transcriptional suppression. The compound exhibits potent antiproliferative activity in AR-overexpressing, ERα-deficient LNCaP prostate cancer cells (IC50 = 0.46 μM), but significantly reduced activity in AR-negative MDA-MB-231 cells (IC50 > 30 μM). PROTAC AR Degrader-12 effectively stabilizes AR protein at high temperatures but offers weak protection to ERα, indicating interaction with AR but not ERα in LCC2 cells. It significantly inhibits mRNA expression of FOXA1, GREB1, SRC, and PELP1 in MCF-7 cells (1 μM, 24 hours). Furthermore, PROTAC AR Degrader-12 (1-10 μM, 48 hours) induces S-phase cell cycle arrest in MCF-7 and LCC2 cells.

PROTAC AR Degrader-12 (Compound 18o) administered at 5-10 μM/kg via intraperitoneal injection every other day effectively inhibits tumor growth in MCF-7 and LCC2 cell xenograft mouse models. It promotes AR protein degradation and ERα signaling inhibition without causing weight loss or other toxicity.