ABSTRACT
Castration resistant prostate cancer (CRPC) remains an incurable disease stage with ineffective treatments options. Here, the androgen receptor (AR) coactivators CBP/p300, which are histone acetyltransferases, were identified as critical mediators of DNA damage repair (DDR) to potentially enhance therapeutic targeting of CRPC. Key findings demonstrate that CBP/p300 expression increases with disease progression and selects for poor prognosis in metastatic disease. CBP/p300 bromodomain inhibition enhances response to standard of care therapeutics. Functional studies, CBP/p300 cistrome mapping, and transcriptome in CRPC revealed that CBP/p300 regulates DDR. Further mechanistic investigation showed that CBP/p300 attenuation via therapeutic targeting and genomic knockdown decreases homologous recombination (HR) factors in vitro, in vivo, and in human prostate cancer (PCa) tumors ex vivo. Similarly, CBP/p300 expression in human prostate tissue correlates with HR factors. Lastly, targeting CBP/p300 impacts HR-mediate repair and patient outcome. Collectively, these studies identify CBP/p300 as drivers of PCa tumorigenesis and lay the groundwork to optimize therapeutic strategies for advanced PCa via CBP/p300 inhibition, potentially in combination with AR-directed and DDR therapies.
ABSTRACT
CCS1477 (inobrodib) is a potent, selective EP300/CBP bromodomain inhibitor which induces cell-cycle arrest and differentiation in hematologic malignancy model systems. In myeloid leukemia cells, it promotes rapid eviction of EP300/CBP from an enhancer subset marked by strong MYB occupancy and high H3K27 acetylation, with downregulation of the subordinate oncogenic network and redistribution to sites close to differentiation genes. In myeloma cells, CCS1477 induces eviction of EP300/CBP from FGFR3, the target of the common (4; 14) translocation, with redistribution away from IRF4-occupied sites to TCF3/E2A-occupied sites. In a subset of patients with relapsed or refractory disease, CCS1477 monotherapy induces differentiation responses in AML and objective responses in heavily pre-treated multiple myeloma. In vivo preclinical combination studies reveal synergistic responses to treatment with standard-of-care agents. Thus, CCS1477 exhibits encouraging preclinical and early-phase clinical activity by disrupting recruitment of EP300/CBP to enhancer networks occupied by critical transcription factors.
Subject(s)
Hematologic Neoplasms , Nuclear Proteins , Humans , Cell Line, Tumor , Transcription Factors , Protein Domains , Hematologic Neoplasms/drug therapy , Hematologic Neoplasms/genetics , E1A-Associated p300 ProteinABSTRACT
Resistance to androgen receptor (AR) blockade in castration-resistant prostate cancer (CRPC) is associated with sustained AR signaling, including through alternative splicing of AR (AR-SV). Inhibitors of transcriptional coactivators that regulate AR activity, including the paralog histone acetyltransferase proteins p300 and CBP, are attractive therapeutic targets for lethal prostate cancer. Herein, we validate targeting p300/CBP as a therapeutic strategy for lethal prostate cancer and describe CCS1477, a novel small-molecule inhibitor of the p300/CBP conserved bromodomain. We show that CCS1477 inhibits cell proliferation in prostate cancer cell lines and decreases AR- and C-MYC-regulated gene expression. In AR-SV-driven models, CCS1477 has antitumor activity, regulating AR and C-MYC signaling. Early clinical studies suggest that CCS1477 modulates KLK3 blood levels and regulates CRPC biopsy biomarker expression. Overall, CCS1477 shows promise for the treatment of patients with advanced prostate cancer. SIGNIFICANCE: Treating CRPC remains challenging due to persistent AR signaling. Inhibiting transcriptional AR coactivators is an attractive therapeutic strategy. CCS1477, an inhibitor of p300/CBP, inhibits growth and AR activity in CRPC models, and can affect metastatic CRPC target expression in serial clinical biopsies.See related commentary by Rasool et al., p. 1011.This article is highlighted in the In This Issue feature, p. 995.
Subject(s)
Androgen Receptor Antagonists/therapeutic use , Imidazoles/therapeutic use , Oxazoles/therapeutic use , Prostatic Neoplasms, Castration-Resistant/drug therapy , p300-CBP Transcription Factors/antagonists & inhibitors , Androgen Receptor Antagonists/pharmacology , Animals , Cell Line, Tumor/drug effects , Cell Proliferation/drug effects , Humans , Imidazoles/pharmacology , Male , Mice , Oxazoles/pharmacology , Xenograft Model Antitumor AssaysABSTRACT
A potent inhibitor of PI3Kδ that is ≥ 200 fold selective for the remaining three Class I PI3K isoforms and additional kinases is described. The hypothesis for selectivity is illustrated through structure activity relationships and crystal structures of compounds bound to a K802T mutant of PI3Kγ. Pharmacokinetic data in rats and mice support the use of 3 as a useful tool compound to use for in vivo studies.
Subject(s)
Phosphoinositide-3 Kinase Inhibitors , Protein Kinase Inhibitors/chemistry , Tryptophan/chemistry , Animals , Binding Sites , Computer Simulation , Female , Injections, Intravenous , Liver/metabolism , Male , Mice , Mice, Inbred BALB C , Mutation , Phosphatidylinositol 3-Kinases/genetics , Phosphatidylinositol 3-Kinases/metabolism , Protein Isoforms/antagonists & inhibitors , Protein Isoforms/genetics , Protein Isoforms/metabolism , Protein Kinase Inhibitors/chemical synthesis , Protein Kinase Inhibitors/pharmacokinetics , Protein Structure, Tertiary , Rats , Rats, Sprague-Dawley , Structure-Activity RelationshipABSTRACT
PI3Kδ is a lipid kinase and a member of a larger family of enzymes, PI3K class IA(α, ß, δ) and IB (γ), which catalyze the phosphorylation of PIP2 to PIP3. PI3Kδ is mainly expressed in leukocytes, where it plays a critical, nonredundant role in B cell receptor mediated signaling and provides an attractive opportunity to treat diseases where B cell activity is essential, e.g., rheumatoid arthritis. We report the discovery of novel, potent, and selective PI3Kδ inhibitors and describe a structural hypothesis for isoform (α, ß, γ) selectivity gained from interactions in the affinity pocket. The critical component of our initial pharmacophore for isoform selectivity was strongly associated with CYP3A4 time-dependent inhibition (TDI). We describe a variety of strategies and methods for monitoring and attenuating TDI. Ultimately, a structure-based design approach was employed to identify a suitable structural replacement for further optimization.
Subject(s)
Arthritis, Rheumatoid/drug therapy , Cytochrome P-450 CYP3A Inhibitors , Drug Discovery , Enzyme Inhibitors/pharmacology , Phosphoinositide-3 Kinase Inhibitors , Arthritis, Rheumatoid/enzymology , Benzimidazoles/chemistry , Benzimidazoles/pharmacology , Benzimidazoles/therapeutic use , Cell Line , Cytochrome P-450 CYP3A , Enzyme Inhibitors/chemistry , Enzyme Inhibitors/therapeutic use , Humans , Inhibitory Concentration 50 , Models, Molecular , Phosphatidylinositol 3-Kinases/chemistry , Protein Conformation , Substrate Specificity , Time FactorsABSTRACT
A novel series of [4-[4-(methylsulfonyl)phenyl]-6-(trifluoromethyl)-2-pyrimidine-based cyclooxygenase-2 (COX-2) inhibitors, which have a different arrangement of substituents compared to the more common 1,2-diarylheterocycle based molecules, have been discovered. For example, 2-(butyloxy)-4-[4-(methylsulfonyl)phenyl]-6-(trifluoromethyl)pyrimidine (47), a member of the 2-pyrimidinyl ether series, has been shown to be a potent and selective inhibitor with a favourable pharmacokinetic profile, high brain penetration and good efficacy in rat models of hypersensitivity.
Subject(s)
Amines/chemical synthesis , Cyclooxygenase 2 Inhibitors/chemical synthesis , Ethers/chemical synthesis , Pyrimidines/chemical synthesis , Sulfones/chemical synthesis , Amines/pharmacology , Animals , Brain/drug effects , Brain/metabolism , Chemistry, Pharmaceutical/methods , Cyclooxygenase 2/chemistry , Cyclooxygenase 2 Inhibitors/pharmacology , Disease Models, Animal , Drug Design , Ethers/pharmacology , Humans , Inflammation , Inhibitory Concentration 50 , Mice , Molecular Structure , Neurodegenerative Diseases/drug therapy , Pyrimidines/pharmacology , Rats , Sulfones/pharmacologyABSTRACT
GW406381 (8), currently undergoing clinical evaluation for the treatment of inflammatory pain is a member of a novel series of 2,3-diaryl-pyrazolo[1,5-b]pyridazine based cyclooxygenase-2 (COX-2) inhibitors, which have been shown to be highly potent and selective. Several examples of the series, in addition to possessing favourable pharmacokinetic profiles and analgesic activity in vivo, have also demonstrated relatively high brain penetration in the rat compared with the clinically available compounds, which may ultimately prove beneficial in the treatment of pain.
