Analogs of the neuropeptide somatostatin are important therapeutics for the treatment of hormone secreting tumors with annual sales in excess of $1.3B. However, currently available peptide depots are only effective in approximately half the patients with growth hormone secreting tumors and patients with carcinoid tumors rapidly become resistant to the drug. These agents act by stimulating a G protein coupled receptor (GPCR) sst2A to activate Gi, but they also cause desensitization and internalization of the receptor resulting in reduced responsiveness. We hypothesize that biased agonists of somatostatin receptor that maintain strong Gi activation but do not induce internalization or desensitization would normalize hormone levels in a greater percentage of patients and in patients not adequately controlled by currently available agents. Here we propose to test this hypothesis by using assays for receptor internalization and site-specific phosphorylation to guide medicinal chemistry optimization of nonpeptide orally active somatostatin biased agonists with the goal of providing improved therapeutic options for many patients with these tumors. This approach is premised on our recent observations that the nonpeptide L-779,976 is a biased somatostatin receptor agonist with strong Gi activation, but more rapid release of recruited 2-arrestin and reduced loss of cell surface receptor compared to peptide agonists. In Phase I we propose to extend this pharmacologic characterization to a diverse panel of nonpeptide somatostatin agonists with the goal of demonstrating feasibility of the assays to support medicinal chemistry and prioritizing lead chemical series for subsequent optimization of both pharmacologic and pharmaceutical properties in Phase II. This will include rigorous measurement of their intrinsic efficacy and ability to induce receptor desensitization-- fundamental pharmacologic data that is surprisingly lacking in the literature for this important class of therapeutics. The product resulting from the Phase II efforts will be a novel orally available compound (or compounds) ready for preclinical toxicology studies in preparation to begin clinical development. In addition to improved clinical efficacy such oral agents would also reduce the need for physician office visits, eliminate the pain and discomfort of depot injections, and lower manufacturing costs compared to expensive peptide depot formulations. Beyond the creation of a novel therapeutic agent, this approach is innovative in the prospective use of receptor regulatory assays to guide early medicinal chemistry efforts, rather than the retrospective analysis of one or two compounds that have already succeeded in the clinic. GPCRs share many common regulatory and signaling mechanisms and are both the largest gene family in the human genome and a rich source of proven targets for drug discovery. Therefore, if successful, the impact of this work not only be to provide improved agents for patients with hormone secreting tumors, but it will also exemplify a novel and general strategy for optimizing agonist drugs targeting other GPCRs.
Public Health Relevance: This project uses assays for receptor internalization, site specific phosphorylation, desensitization &intrinsic efficacy to guide design and synthesis of novel orally available biased agonists of the somatostatin receptor sst2A with improved efficacy and reduced desensitization for the treatment of hormone secreting tumors. If successful, this work would provide a general strategy for agonist optimization of many additional GPCR drug targets.
Thesaurus Terms: 1,2-Dithia-5,8,11,14,17-Pentaazacycloeicosane Cyclic Peptide Deriv;1h-Naphtho(2,1-B)Pyran-1-One, 5-(Acetyloxy)-3-Ethenyldodecahydro-6,10,10b-Trihydroxy-3,4a,7,7,10a-Pentamethyl-;3'5'-Cyclic Ester Of Amp;Aids Chemotherapy;Ac-D(2)Nal(1)-4-Cl-Phe(2)-D(3)Pal(3,6)-Arg(5)-Ala(10)-Gnrh;Adenosine Cyclic 3',5'-Monophosphate;Adenosine Cyclic Monophosphate;Adenosine, Cyclic 3',5'-(Hydrogen Phosphate);Affinity;Agonist;Amentia;Area;Arrestins;Assay;Binding;Binding (Molecular Function);Bioassay;Biologic Assays;Biological Assay;Carcinoid;Carcinoid Neoplasm;Carcinoid Tumor;Cell Communication And Signaling;Cell Signaling;Cell Surface Receptors;Chemicals;Chemistry, Pharmaceutical;Chemotherapy-Hormones/Steroids;Clinic;Clinical;Clinical Evaluation;Clinical Testing;Coleonol;Cushing Disease;Cyclic Amp;Cyclic Somatostatin;D-Phenylalanyl-L-Cysteinyl-L-Phenyl-Alanyl-D-Tryptophyl-L-Lysyl-L-Threonyl-N-[2-Hydroxy-1-(Hydroxymethyl)Propyl]-L-Cysteinamide Cyclic (2-7)-Disulfide;Data;Dementia;Depot Preparation;Development;Diabetic Kidney Disease;Diabetic Nephropathy;Diabetic Retinopathy;Diarrhea;Disease;Disorder;Drug Delivery;Drug Delivery Systems;Drug Formulations;Drug Targeting;Drug Targetings;Drug Resistance;Drugs;Endocrine Gland Secretion;Epilepsy;Epileptic Seizures;Epileptics;Evaluation;Formulation;Formulations, Drug;Forskolin;G Protein-Complex Receptor;G-Protein-Coupled Receptors;Ghn;Gene Family;Goals;Government;Growth Hormone;Growth Hormone 1;Growth Hormone Inhibiting Factors;Growth Hormone-Inhibiting Hormone;Growth Hormone Excess;Hormones;Human Genome;Injection Of Therapeutic Agent;Injections;Intracellular Communication And Signaling;L-Cysteinamide, D-Phenylalanyl-L-Cysteinyl-L-Phenylalanyl-D-Tryptophyl-L-Lysyl-L-Threonyl-N-(2-Hydroxy-1-(Hydroxymethyl)Propyl)-, Cyclic (2-7)-Disulfide, (R-(R*,R*))-;Laboratories;Lead;Licensing;Ligands;Literature;Measurement;Medication;Medicinal Chemistry;Molecular Interaction;Neuroendocrine Neoplasm;Neuroendocrine Tumors;Neuropeptides;Octreotide;Office Visits;Oral;Pain;Painful;Patient Agents;Patients;Pb Element;Peptides;Persons;Pharmaceutic Chemistry;Pharmaceutic Preparations;Pharmaceutical Agent;Pharmaceutical Chemistry;Pharmaceutical Preparations;Pharmaceuticals;Pharmacologic Substance;Pharmacological Substance;Phase;Phosphorylation;Physiologic;Physiological;Pituitary Acth Hypersecretion;Pituitary Growth Hormone;Pituitary-Dependent Cushing's Disease;Pituitary-Dependent Cushing's Disorder;Position;Positioning Attribute;Preparation;Property;Property, Loinc Axis 2;Protein Phosphorylation;Receptor Protein;Receptors, Somatotropin Release Inhibiting Hormone;Recruitment Activity;Regulation;Resistance;Role;Srih;Srih Receptors;Srih-14;Sth;Sales;Seizure Disorder;Series;Signal Transduction;Signal Transduction Systems;Signaling;Site;Somatostatin;Somatostatin Receptor;Somatostatin-14;Somatotrophin Increased;Somatotropin;Somatotropin Release Inhibiting Factors;Somatotropin Release-Inhibiting Hormone;Source;Structure-Activity Relationship;System;System, Loinc Axis 4;Testing;Texas;Therapeutic;Therapeutic Agents;Therapeutic Hormone;Toxicology;Treatment Efficacy;Universities;Well-Differentiated Endocrine Neoplasm;Work;Adenoma;Adenosine 3'5' Monophosphate;Analog;Analog L;Arrestin 2;Base;Biological Signal Transduction;Camp;Cell Surface Receptor;Chemical Structure Function;Chronic Pain;Chronic Painful Condition;Clinical Efficacy;Clinical Test;Comparative Efficacy;Cost;Desensitization;Design;Designing;Disease /Disorder;Disease/Disorder;Drug /Agent;Drug Candidate;Drug Discovery;Drug Resistant;Drug/Agent;Epilepsia;Epileptiform;Epileptogenic;Growth Hormone Release Inhibiting Factor;Hghn;Heavy Metal Pb;Heavy Metal Lead;Improved;Innovate;Innovation;Innovative;New Therapeutics;Next Generation Therapeutics;Novel;Novel Therapeutics;Peptide Analog;Physician Office Visit;Pre-Clinical;Preclinical;Prospective;Receptor;Receptor Internalization;Recruit;Research Clinical Testing;Resistance To Drug;Resistant;Resistant To Drug;Social Role;Somatostatin Analog;Somatotropic Hormone;Structure Function Relationship;Therapeutic Efficacy;Therapeutic Target;Therapeutically Effective;Tumor;University
