SBIR-STTR Award

The non-tuberculous mycobacteria (NTM) are a growing public health concern as the number of opportunistic infections increases. Although not a reportable disease, there is growing epidemiologic evidence to suggest that NTM cause more infections today in the United States than Mycobacterium tuberculosis (Mtb) yet, unlike Mtb, there are few dedicated antimicrobial drug discovery programs specifically for NTM. Pulmonary disease caused by NTM is especially problematic in patients with underlying susceptibilities such as immunosuppressive medications, cystic fibrosis and other lung diseases, HIV and malignancies. Given the emergence of NTM as a public health issue, finding new antibacterial agents is of high importance. We have screened libraries of novel compounds for anti-NTM activity, focusing on M. abscessus, and have found several promising hits centered around three chemically tractable small molecule scaffolds that exhibit minimal cytotoxicity. The minimum inhibitory concentrations (MIC) values range from 0.5 to 4 ¿g/mL for different NTM, thus providing a relatively potent starting point for optimization. Importantly, each of these compounds also has activity against Mtb, enabling us to focus on broad-spectrum activity. We propose to perform medicinal chemistry hit-to-lead optimization, developing an understanding of the key structure-activity relationships driving antibacterial activity. In Aim 1, we will synthesie a small set of analogs for each of three scaffolds, focusing on efficient sites for derivatization tht will allow for rapid synthesis of 30-50 analogs. In addition, there are 76 commercially available analogs within these compound series, facilitating rapid assembly of at least 100 analogs for testing in Aim 2. The goal of Aim 2 is to prioritize the scaffolds based on biological properties, beginning with MIC testing against a panel of NTM, including M. abscessus, M. avium, M. intracellulare, and M. chelonae. Analogs that show anti-NTM activity will progress to a secondary screen against Mtb and a broad panel of clinically important Gram-positive and Gram-negative pathogens and fungi. Further characterization will include analysis of metabolic stability in human liver microsomes, assessment of bactericidal potential, serum protein binding potential and sensitivity to efflux inhibitors. The most promising scaffold with respect to breadthof antimicrobial spectrum, potency and pharmacologic properties will be selected for in-depth medicinal chemistry optimization in Aim 3, utilizing an iterative cycle of chemical synthesis followed by biological profiling to guide the development of SAR. Successful completion of Aim 3 is expected to produce one or more compound leads suitable for future in vivo testing. We believe these compounds represent an exciting and promising starting point for the development of a novel therapeutic agent with broad antimycobacterial activity.

Thesaurus Terms:
Analog;Anti-Bacterial Agents;Antibiotics;Antimicrobial;Antimicrobial Drug;Antimycobacterial Agents;Automobile Driving;Bactericide;Base;Benchmarking;Biological;Cells;Characteristics;Chemical Synthesis;Clinically Relevant;Complex;Cystic Fibrosis;Cytotoxicity;Data Set;Development;Disease;Dose;Drug Discovery;Drug Kinetics;Epidemiology;Exhibits;Frequencies (Time Pattern);Fungus;Future;Genus Mycobacterium;Goals;Gram-Negative Bacteria;Health;Hemolysis;Hiv;Human;Immunosuppressive Agents;In Vitro;In Vivo;Infection;Inhibitor/Antagonist;Lead;Lead Series;Libraries;Liver Microsomes;Lung Diseases;Malignant Neoplasms;Medical;Metabolic;Minimum Inhibitory Concentration Measurement;Modeling;Mycobacterial;Mycobacterium Infections;Mycobacterium Tuberculosis;Novel;Novel Therapeutics;Opportunistic Infections;Pathogen;Patients;Pharmaceutical Chemistry;Pharmaceutical Preparations;Predisposition;Process;Programs;Property;Protein Binding;Public Health Medicine (Field);Public Health Relevance;Resistance;Resistance Development;Scaffold;Screening;Series;Serum Proteins;Site;Small Molecule;Structure-Activity Relationship;Testing;Therapeutic;Therapeutic Agents;Toxic Effect;Toxicology;United States;

The nontuberculous Mycobacteria (NTM) are a growing public health concern as the number of opportunistic infections increases. Although not a reportable disease, there is growing epidemiologic evidence to suggest that NTM cause more infections today in the United States than Mycobacterium tuberculosis (Mtb) yet, unlike Mtb, there are few dedicated antimicrobial drug discovery programs specifically for NTM. Pulmonary disease caused by NTM is especially problematic in patients with underlying susceptibilities such as immunosuppressive medications, cystic fibrosis and other lung diseases, HIV and malignancies. Given the emergence of NTM as a public health issue, finding new antibacterial agents is of high importance. We have screened libraries of novel compounds for anti-NTM activity, focusing on M. abscessus (Mab), and identifying several promising small molecule screening hits with chemically-tractable scaffolds. Our Phase I SBIR grant focused on initial medicinal chemistry optimization of early drug leads that exhibited minimal cytotoxicity, high metabolic stability and low potential for resistance development. We achieved minimum inhibitory concentration (MIC) values ranging from 0.06 to 2 µg/mL for rapidly growing Mycobacteria (RGM), including Mab, M. chelonae, M. fortiutum and M. peregrinum. Importantly, these compounds also have activity against Mtb (MIC 4 to 16 µg/mL) and against permeabilized Gram-negative bacteria (GNB), potentially enabling us to attain broad spectrum antibacterial activity. We propose to continue development of a very promising benzothiazole cyclohexylcarboxamide series with Phase II SBIR support, focusing on advanced medicinal chemistry lead optimization with a goal of obtaining a strong drug candidate with demonstrated in vivo activity. In Aim 1, we will synthesize over a hundred analogs, which will be characterized in Aim 2 using a cascade of screening assays, beginning with MIC testing against RGM, followed by analysis of efflux, serum-binding, hemolysis, cytotoxicity, metabolic stability, frequency of resistance emergence, and microbiological spectrum including Mtb and GNB. Promising analogs will be screening for murine pharmacokinetic characteristics using an abbreviated pharmacokinetic protocol. The goal of Aims 1 and 2 will be to identify multiple lead compounds suitable for in vivo efficacy and toxicity testing during Aim 4. Aim 3 will establish mode of action, based on preliminary data indicating that the compounds target MmpL3, an essential protein thought to be involved in translocation of mycolic acids to or across the periplasmic space. Defining the mechanism will facilitate biochemical potency studies, thereby supporting the medicinal chemistry effort in Aim 1. In Aim 4, we will scale up synthesis of several lead compounds, begin to develop process chemistry strategies to improve synthetic efficiency, and evaluate chemical stability. We will utilized NIH preclinical services for the evaluation of maximum tolerated dose as well as efficacy in acute and chronic murine models of Mycobacterial infection. Successful completion of Aim 4 would bring this exciting chemical series to advanced preclinical development, setting the stage for identification of a candidate compound for clinical development. We believe this program holds great promise for development of a novel therapeutic agent with broad anti-mycobacterial activity.

Public Health Relevance Statement:


Public Health Relevance:
Mycobacterial pathogens are intrinsically resistant to most antibiotics, and pose an enormous human health challenge. While Mycobacterium tuberculosis has been the subject of extensive drug discovery efforts, the nontuberculous mycobacteria (NTM) pose a unique therapeutic challenge in the US. Current treatment options for NTM are severely limited, prompting this proposal for development of broad spectrum anti-mycobacterial agents.

NIH Spending Category:
Infectious Diseases; Orphan Drug; Rare Diseases; Tuberculosis

Project Terms:
Acute; Address; Amides; analog; Anti-Bacterial Agents; Antibiotics; antimicrobial drug; Antimycobacterial Agents; base; benzothiazole; Binding (Molecular Function); Biochemical; Biological Assay; Breathing; Cells; chemical stability; Chemicals; Chemistry; Childhood; Chronic; Clinical; clinically relevant; clinically significant; Collaborations; Cystic Fibrosis; cytotoxicity; Data; design; Development; Disease; Dose; drug candidate; drug discovery; Drug Kinetics; efficacy testing; Epidemiology; Evaluation; Exhibits; Feedback; Frequencies (time pattern); Genus Mycobacterium; Goals; Gram-Negative Bacteria; Gram-Positive Bacteria; Grant; Health; Hemolysis; HIV; Human; Immunosuppressive Agents; improved; In Vitro; in vivo; Infection; inhibitor/antagonist; Killings; Kinetics; Knowledge; Lead; lead series; Libraries; Lung diseases; Malignant Neoplasms; Maximum Tolerated Dose; Medical; Membrane; Metabolic; Minimum Inhibitory Concentration measurement; Modeling; Monitor; Mus; mutant; Mutate; Mutation; mycobacterial; Mycobacterium Infections; Mycobacterium tuberculosis; Mycolic Acid; National Institute of Allergy and Infectious Disease; novel; novel therapeutics; Opportunistic Infections; pathogen; Patients; periplasm; pH gradient; Pharmaceutical Chemistry; Pharmaceutical Preparations; pharmacokinetic characteristic; Phase; Population; pre-clinical; Predisposition; Process; programs; Promotor (Genetics); Property; Protein Binding; Proteins; Protocols documentation; public health medicine (field); public health relevance; Research Design; Resistance; Resistance development; resistance frequency; Route; scaffold; scale up; screening; Series; Serum; Services; Site; Small Business Innovation Research Grant; small molecule; Solubility; Staging; Structure-Activity Relationship; targeted sequencing; Testing; Therapeutic; Therapeutic Agents; therapy duration; Time; Toxicity Tests; United States; United States National Institutes of Health; Validation; Wor