A majority of Breast cancers (BC) express estrogen receptor alpha (ERa). While endocrine therapies targeting either estrogen production or ERa are effective, acquired resistance is common. Sequencing of metastatic endocrine therapy-resistant (ETR) tumors has shwown that ERa mutations are frequent (30-40%), do not respond to endocrine therapies and are the molecular drivers of ETR-BC. Thus, drugs designed to specifically target these ERa mutations in ETR-BC represent a significant unmet clinical need. We leveraged the recent structural characterization of the mutant ERa ligand binding domain (LBD) to rationally design bis-benzamides to fit the binding pocket. Following iterative rounds of modeling, synthesis, testing and optimization with >2000 bis-benzamides, we have identified a lead compound, ERX-315, that binds more avidly to ERa LBD. Our preliminary studies showed that ERX-315 has potent anti-proliferative activity against mutant ERa-driven tumors, as seen in genetically modified cell lines in vitro, patient derived explants (PDEs) ex vivo and patient derived xenografts (PDXs) in vivo. Importantly, a methylated version of ERX-315, ERX-314 binds the mutant ERa poorly and does not affect proliferation of these tumors. Ultrastructural and molecular studies reveal that ERX-315, but not ERX-314 (a methylated version of ERX-315, does not bind ERa, serves as a negative control) induces significant endoplasmic reticulum stress, leading to a shutdown of de novo protein synthesis and apoptotic cell death in BC. Importantly, ERX-315 does not induce endoplasmic reticulum stress or cell death in normal cells and is non-toxic in animal models. We have shown that this capacity of ERX- 315 to induce endoplasmic reticulum stress is unique among drugs targeting ERa, including selective ERa modulators and degraders, such as GDC-0180, AXD-9496 and fulvestrant. The objective of this direct Phase II SBIR proposal is to enable EtiraRx to perform IND-enabling studies for clinical translation of ERX-315 in ETR-BCs. We have shown that ERX-315 has favorable pharmacologic parameters for clinical translation and is amenable to good manufacturing practice manufacturing. In Aim 1, we will we will perform dose-ranging finding studies in two species and define maximum tolerated dose and toxicity at that dose. In Aim2, we will synthesize large-scale batches of ERX-315 and will perform single- and multi-dose pharmacokinetic studies and evaluate tissue biodistribution. We will define 30-day toxicity in rats and dogs with a 2-week recovery, and evaluate functional recovery, cardiovascular and respiratory safety. In Aim 3, We will test the efficacy of clinical grade ERX-315 in biologically and clinically relevant preclinical models of ETR-BC, including patient derived xenografts and patient derived explants. The intellectual property around ERX-315 is protected by multiple patents licensed to EtiraRx. a novel small molecule targeting mutant ERa, and with an unique ability to induce endoplasmic reticulum stress and apoptotic cell death. If successful, our proposed studies will enable within 2 years the first-in-class studies with ERX-315 in women with ETR-BC.
Public Health Relevance Statement: Project Narrative EtiraRx has licensed a first-in-class drug (ERX-315) that was designed to target the mutant forms of the estrogen receptor and induce cytotoxic cell death through a novel mechanism of enhancing endoplasmic reticulum stress. Funding from the SBIR will enable completion of critical preclinical studies for ERX-315, and accelerate progress towards a first-in-man clinical trial of a drug designed to target the mutant estrogen receptor or the major driver of endocrine therapy resistance and metastases in breast cancer
Project Terms: Oral Administration; Oral Drug Administration; intraoral drug delivery; Animals; Benzamides; malignant breast neoplasm; Breast Cancer; malignant breast tumor; Malignant Neoplasms; Cancers; Malignant Tumor; malignancy; neoplasm/cancer; Cardiovascular system; Cardiovascular; Cardiovascular Body System; Cardiovascular Organ System; Heart Vascular; circulatory system; Cell Death; necrocytosis; cell growth; Cellular Expansion; Cellular Growth; Cell Line; CellLine; Strains Cell Lines; cultured cell line; Clinical Trials; Canis familiaris; Canine Species; Dogs; Dogs Mammals; canine; domestic dog; Drug Design; Pharmaceutical Preparations; Drugs; Medication; Pharmaceutic Preparations; drug/agent; Endoplasmic Reticulum; Ergastoplasm; Estradiol; Aquadiol; Dimenformon; Diogyn; Diogynets; Estrace; Estradiol-17 beta; Estradiol-17beta; Estraldine; Ovocyclin; Ovocylin; Progynon; Therapeutic Estradiol; Estrogens; Therapeutic Estrogen; Grant; Growth; Generalized Growth; Tissue Growth; ontogeny; In Vitro; Natural Killer Cells; Cytotoxic cell; K lymphocyte; NK Cells; Lead; Pb element; heavy metal Pb; heavy metal lead; Mutation; Genetic Alteration; Genetic Change; Genetic defect; genome mutation; Neoplasm Metastasis; Metastasis; Metastasize; Metastatic Lesion; Metastatic Mass; Metastatic Neoplasm; Metastatic Tumor; Secondary Neoplasm; Secondary Tumor; cancer metastasis; tumor cell metastasis; Legal patent; Patents; Patients; Drug Kinetics; Pharmacokinetics; Pharmacology; Production; Proteins; Rattus; Common Rat Strains; Rat; Rats Mammals; Estrogen Receptors; Safety; Testing; Tissues; Body Tissues; Genetic Transcription; Gene Transcription; RNA Expression; Transcription; Translating; Woman; Work; Mediating; Clinical; Refractory; Phase; Biological; Recovery; Progression-Free Survivals; analog; Funding; hormone therapy; Endocrine Therapy; Hormonal Therapy; Intellectual Property; Genetic; programs; Oral; Heterograft; Heterologous Transplantation; Xenograft; Xenotransplantation; xeno-transplant; xeno-transplantation; Xenograft procedure; respiratory; Endocrine; meetings; mutant; Ribosomal Peptide Biosynthesis; Ribosomal Protein Biosynthesis; Ribosomal Protein Synthesis; protein synthesis; Protein Biosynthesis; functional recovery; Recovery of Function; Animal Models and Related Studies; model of animal; model organism; Animal Model; Molecular Modeling Nucleic Acid Biochemistry; Molecular Modeling Protein/Amino Acid Biochemistry; Molecular Models; molecular modeling; Toxicities; Toxic effect; ERalpha; ERa; Estradiol Receptor alpha; Estradiol Receptor a; Estrogen Receptor a; Estrogen Receptor alpha; Primary Tumor; Primary Neoplasm; Structure; novel; Binding Site Domain; Ligand Binding Domain; Maximal Tolerated Dose; Maximally Tolerated Dose; Maximum Tolerated Dose; Modeling; Property; response; Early-Stage Clinical Trials; Phase 1 Clinical Trials; phase I protocol; Phase I Clinical Trials; Bioavailable; Faslodex; ICI 182,780; ICI 182780; Fulvestrant; Molecular Interaction; Binding; Normal Cell; small molecule; ESR1; Estrogen Receptor 1; NR3A1; ESR1 gene; Dose; Breast tumor model; mammary cancer model; mammary tumor model; Breast Cancer Model; Detection; breast tumor cell; Breast Cancer Cell; Preclinical Models; Pre-Clinical Model; in vivo; Apoptotic; Small Business Innovation Research Grant; SBIR; Small Business Innovation Research; Xenograft Model; xenograft transplant model; xenotransplant model; Molecular; pre-clinical; preclinical; preclinical study; pre-clinical study; therapy resistant; resistance to therapy; resistant to therapy; therapeutic resistance; treatment resistance; nonsynonymous mutation; non-synonymous mutation; knock-down; knockdown; design; designing; clinical efficacy; Biodistribution; Outcome; Resistance; resistant; genetically modified cells; genetically engineered cells; clinically relevant; clinical relevance; therapy design; intervention design; treatment design; tumor; efficacy testing; endoplasmic reticulum stress; ER stress; Drug Targeting; targeted treatment; targeted drug therapy; targeted drug treatments; targeted therapeutic; targeted therapeutic agents; targeted therapy; Breast Cancer cell line; Breast tumor cell line; Metastatic breast cancer; transcriptome; global gene expression; global transcription profile; clinical translation; lead candidate; first-in-human; first in man; patient derived xenograft model; PDX model; Patient derived xenograft; therapeutically effective; efficacy validation; validate efficacy
