ABSTRACT
Mutations in estrogen receptor alpha (ERα) that confer resistance to existing classes of endocrine therapies are detected in up to 30% of patients who have relapsed during endocrine treatments. Because a significant proportion of therapy-resistant breast cancer metastases continue to be dependent on ERα signaling, there remains a critical need to develop the next generation of ERα antagonists that can overcome aberrant ERα activity. Through our drug-discovery efforts, we identified H3B-5942, which covalently inactivates both wild-type and mutant ERα by targeting Cys530 and enforcing a unique antagonist conformation. H3B-5942 belongs to a class of ERα antagonists referred to as selective estrogen receptor covalent antagonists (SERCA). In vitro comparisons of H3B-5942 with standard-of-care (SoC) and experimental agents confirmed increased antagonist activity across a panel of ERαWT and ERαMUT cell lines. In vivo, H3B-5942 demonstrated significant single-agent antitumor activity in xenograft models representing ERαWT and ERαY537S breast cancer that was superior to fulvestrant. Lastly, H3B-5942 potency can be further improved in combination with CDK4/6 or mTOR inhibitors in both ERαWT and ERαMUT cell lines and/or tumor models. In summary, H3B-5942 belongs to a class of orally available ERα covalent antagonists with an improved profile over SoCs.Significance: Nearly 30% of endocrine therapy-resistant breast cancer metastases harbor constitutively activating mutations in ERα. SERCA H3B-5942 engages C530 of both ERαWT and ERαMUT, promotes a unique antagonist conformation, and demonstrates improved in vitro and in vivo activity over SoC agents. Importantly, single-agent efficacy can be further enhanced by combining with CDK4/6 or mTOR inhibitors. Cancer Discov; 8(9); 1176-93. ©2018 AACR.This article is highlighted in the In This Issue feature, p. 1047.
Subject(s)
Breast Neoplasms/drug therapy , Drug Resistance, Neoplasm/drug effects , Estrogen Receptor Antagonists/administration & dosage , Estrogen Receptor alpha/antagonists & inhibitors , Indazoles/administration & dosage , Mutation , Administration, Oral , Animals , Breast Neoplasms/genetics , Cell Line, Tumor , Cell Proliferation/drug effects , Cell Survival/drug effects , Cysteine/antagonists & inhibitors , Drug Screening Assays, Antitumor , Drug Synergism , Estrogen Receptor Antagonists/chemistry , Estrogen Receptor Antagonists/pharmacology , Estrogen Receptor alpha/chemistry , Estrogen Receptor alpha/genetics , Female , Humans , Indazoles/chemistry , Indazoles/pharmacology , MCF-7 Cells , Mice , Protein Conformation/drug effects , Protein Kinase Inhibitors/administration & dosage , Protein Kinase Inhibitors/pharmacology , Xenograft Model Antitumor AssaysABSTRACT
We describe the synthesis and characterization of 3-alkoxy-pyrrolo[1,2-b]pyrazolines as novel selective androgen receptor (AR) modulators that possess excellent physicochemical properties for transdermal administration. Compound 26 bound to human AR with an IC50 of 0.7 nM with great selectivity over other nuclear hormone receptors and potently activated AR in a C2C12 muscle cell reporter gene assay with an EC50 of 0.5 nM. It showed high aqueous solubility of 1.3 g/L at pH 7.4, and an in silico model as well as a customized parallel artificial membrane permeability assay indicated good skin permeation. Indeed, when measuring skin permeation through excised human skin, an excellent flux of 2 µg/(cm(2)·h) was determined without any permeation enhancers. In a 2 week Hershberger model using castrated rats, the compound showed dose-dependent effects fully restoring skeletal muscle weight at 0.3 mg/kg/day after subcutaneous administration with high selectivity over prostate stimulation.
Subject(s)
Androgen Receptor Antagonists/chemistry , Androgens/chemistry , Azabicyclo Compounds/chemistry , Pyrazoles/chemistry , Receptors, Androgen/chemistry , Administration, Cutaneous , Androgen Receptor Antagonists/metabolism , Androgen Receptor Antagonists/pharmacokinetics , Androgens/metabolism , Animals , Area Under Curve , Azabicyclo Compounds/metabolism , Azabicyclo Compounds/pharmacokinetics , Binding Sites , Binding, Competitive , Cell Line , Chemical Phenomena , Crystallography, X-Ray , Humans , Male , Metabolic Clearance Rate , Mice , Models, Chemical , Models, Molecular , Molecular Structure , Protein Structure, Tertiary , Pyrazoles/metabolism , Pyrazoles/pharmacokinetics , Rats, Wistar , Receptors, Androgen/metabolism , Skin/metabolismABSTRACT
We have identified a novel 7-azaindole series of anaplastic lymphoma kinase (ALK) inhibitors. Compounds 7b, 7 m and 7 n demonstrate excellent potencies in biochemical and cellular assays. X-ray crystal structure of one of the compounds (7 k) revealed a unique binding mode with the benzyl group occupying the back pocket, explaining its potency towards ALK and selectivity over tested kinases particularly Aurora-A. This binding mode is in contrast to that of known ALK inhibitors such as Crizotinib and NVP-TAE684 which occupy the ribose binding pocket, close to DFG motif.