A-485

A-485 is acetyl-CoA competitive p300/CBP catalytic inhibitor. A-485 selectively inhibited proliferation across lineage-specific tumor types, including several hematological malignancies and androgen receptor-positive prostate cancer. A-485 inhibited the androgen receptor transcriptional program in both androgen sensitive and castrate resistant prostate cancer. A-485 inhibited the activity of the p300-BHC (bromodomain-HAT-C/H3) domain (IC50 = 9.8 nM) as well as CBP-BHC (IC50 = 2.6 nM). A-485 is assayed against other HAT family members and does not inhibit the activity of PCAF, HAT1, MYST3, MYST4, TIP60 and GCN5L2 at 10 µM and is selective over BET bromodomain proteins and >150 non-epigenetic targets. The compound only displayed substantial binding (>90%) to dopamine and serotonin transporters at 10 µM along with modest inhibition of Plk3 (IC50=2.7 µM). As A-485 does not achieve significant brain exposure, it is unlikely to modulate these transporters in vivo. A-485 is selective for p300/CBP over other HATs and histone methyltransferases (HMTs) in cells. It only inhibits H3K27Ac and H3K18Ac. A-485 selectively inhibits hematological and prostate cancer cell proliferation and that inhibition of p300/CBP-mediated global histone acetylation does not necessarily translate to an anti-proliferative phenotype. A-485 is primarily metabolized by CYP3A4 in vitro. A-485 also exhibits modest inhibition of CYP2C8 (IC50=0.99 μM) and CYP2C9 (IC50=1.65 μM). There was no activity toward hERG (>30 μM)^[1].

HeLa cells were SILAC labeled with heavy isotopes of arginine and lysine. The cells were treated with A-485 (10 μM) or vehicle control for 16 hours. Cell were lysed in ice-cold lysis buffer [50 mM Hepes, pH7.5, 150 mM NaCl, 1 mM EDTA, 1% NP-40, 0.1% sodium deoxycholate, 1x complete protease inhibitor cocktail]. Proteins were proteolyzed with trypsin, and acetylated peptides were analyzed.

A-485 displays favorable ADME properties and PK profile. A-485 inhibits tumor growth in a castration resistant xenograft model. Treatment of A-485 in LuCaP-77 CR tumor bearing mice tumor induces a decrease in tumor c-Myc protein levels and moderate body weight loss^[1].