ABSTRACT
Potent estrogen receptor ligands typically contain a phenolic hydrogen-bond donor. The indazole of the selective estrogen receptor degrader (SERD) ARN-810 is believed to mimic this. Disclosed herein is the discovery of ARN-810 analogs which lack this hydrogen-bond donor. These SERDs induced tumor regression in a tamoxifen-resistant breast cancer xenograft, demonstrating that the indazole NH is not necessary for robust ER-modulation and anti-tumor activity.
Subject(s)
Antineoplastic Agents/pharmacology , Cinnamates/pharmacology , Drug Resistance, Neoplasm/drug effects , Indazoles/pharmacology , Receptors, Estrogen/antagonists & inhibitors , Selective Estrogen Receptor Modulators/pharmacology , Tamoxifen/pharmacology , Animals , Antineoplastic Agents/chemical synthesis , Antineoplastic Agents/chemistry , Cell Proliferation/drug effects , Cell Survival/drug effects , Cinnamates/chemical synthesis , Cinnamates/chemistry , Dose-Response Relationship, Drug , Drug Screening Assays, Antitumor , Female , Indazoles/chemical synthesis , Indazoles/chemistry , Mammary Neoplasms, Experimental/drug therapy , Mammary Neoplasms, Experimental/metabolism , Mammary Neoplasms, Experimental/pathology , Mice , Molecular Structure , Receptors, Estrogen/metabolism , Selective Estrogen Receptor Modulators/chemical synthesis , Selective Estrogen Receptor Modulators/chemistry , Structure-Activity Relationship , Tamoxifen/chemical synthesis , Tamoxifen/chemistryABSTRACT
Selective estrogen receptor degraders (SERDs) have shown promise for the treatment of ER+ breast cancer. Disclosed herein is the continued optimization of our indazole series of SERDs. Exploration of ER degradation and antagonism in vitro followed by in vivo antagonism and oral exposure culminated in the discovery of indazoles 47 and 56, which induce tumor regression in a tamoxifen-resistant breast cancer xenograft.
Subject(s)
Antineoplastic Agents/therapeutic use , Breast Neoplasms/drug therapy , Estrogen Receptor Antagonists/therapeutic use , Indazoles/therapeutic use , Tamoxifen/therapeutic use , Animals , Antineoplastic Agents/chemistry , Breast Neoplasms/metabolism , Breast Neoplasms/pathology , Cinnamates/therapeutic use , Drug Resistance, Neoplasm , Estrogen Receptor Antagonists/metabolism , Female , Indazoles/chemistry , Rats , Structure-Activity Relationship , Xenograft Model Antitumor AssaysABSTRACT
Corticotropin releasing factor-binding protein (CRF-BP) binds CRF and urocortin 1 (Ucn 1) with high affinity, thus preventing CRF receptor (CRFR) activation. Despite recent progress on the molecular details that govern interactions between CRF family neuropeptides and their cognate receptors, little is known concerning the mechanisms that allow CRF-BP to bind CRF and Ucn 1 with picomolar affinity. We conducted a comprehensive alanine scan of 76 evolutionarily conserved residues of CRF-BP and identified several residues that differentially affected the affinity for CRF over Ucn 1. We determined that both neuropeptides derive their similarly high affinity from distinct binding surfaces on CRF-BP. Alanine substitutions of arginine 56 (R56A) and aspartic acid 62 (D62A) reduce the affinity for CRF by approximately 100-fold, while only marginally affecting the affinity for Ucn 1. The selective reduction in affinity for CRF depends on glutamic acid 25 in the CRF peptide, as substitution of Glu(25) reduces the affinity for CRF-BP by approximately 2 orders of magnitude, but only in the presence of both Arg(56) and Asp(62) in human CRF-BP. We show that CRF-BP(R56A) and CRF-BP(D62A) have lost the ability to inhibit CRFR1-mediated responses to CRF that activate luciferase induction in HEK293T cells and ACTH release from cultured rat anterior pituitary cells. In contrast, both CRF-BP mutants retain the ability to inhibit Ucn 1-induced CRFR1 activation. Collectively our findings demonstrate that CRF-BP has distinct and separable binding surfaces for CRF and Ucn 1, opening new avenues for the design of ligand-specific antagonists based on CRF-BP.
