Introduction and Background of the Project

Introduction

Tuberculosis has been the infectious disease that has claimed the largest number of human lives throughout human history. Even today, it causes more deaths than AIDS and COVID-19, and the global tuberculosis pandemic can still be considered ongoing. A major characteristic of Mycobacterium tuberculosis is its slow growth rate and its frequent transition into a “dormant” state, in which the bacteria become almost inactive. In this state, currently available drugs are much less effective. As a result, standard tuberculosis treatment requires a long duration of at least six months. If treatment is discontinued prematurely, drug-resistant strains can emerge, leading to serious clinical and public health problems.

Dormant M. tuberculosis can also persist in human body for long periods and may resume growth later in life. This process, known as reactivation, is thought to be responsible for many cases of adult tuberculosis. For these reasons, the development of drugs that can suppress or eliminate dormant bacteria is expected to contribute to shorter treatment durations and to the fundamental control of tuberculosis. 

Project objective

The team discovered a protein capable of inducing bacterial dormancy and subsequently identified novel compounds through a search for molecules that strongly bind to the protein. Compounds were effective against actively growing M. tuberculosis, and its activity was further enhanced under conditions in which many M. tuberculosis enter the dormant state.

If a therapeutic agent can be developed that acts on both actively replicating and M. tuberculosis bacilli, it should contribute not only to the treatment of drug-resistant tuberculosis but also to shorter treatment durations and prevention of disease relapse, ultimately leading to the fundamental control of tuberculosis. Previous research for this study was supported by AMED under Grant Number JP16nk0101351 and 23gm1610009h.

In this project, we aim to scientifically and comprehensively evaluate whether this newly identified compound has sufficient potential to serve as a future lead compound for tuberculosis drug development.

Project design

In this project, we will conduct a series of stepwise evaluations to assess the drug discovery potential of candidate compounds. First, compounds produced by actinomycetes will be purified, and their derivatives will be chemically synthesized. Physicochemical properties of the compounds will then be evaluated, including solubility and lipophilicity under physiological conditions. In addition, membrane permeability and the presence of efflux will be examined.

Next, pharmacokinetic-related properties will be assessed by measuring plasma protein binding and determining the unbound fraction. Metabolic stability studies will be performed using liver microsomes and hepatocytes to evaluate fundamental in vivo disposition characteristics.

For safety assessment, potential off-target inhibitory effects will be examined, together with cardiac safety evaluation using hERG inhibition assays. Genotoxicity will also be assessed through Ames tests and in vitro micronucleus assays.

Based on these fundamental evaluations, promising compounds will be advanced to efficacy studies using a mouse tuberculosis infection model to verify in vivo anti-tuberculosis activity.

How can your partnership (project) address global health challenges?

The long duration of tuberculosis treatment, disease relapse due to treatment interruption, and the emergence of drug-resistant tuberculosis remain major global health challenges. In addition, asymptomatic infection caused by dormant M. tuberculosis serves as a reservoir for future disease development.

The therapeutic agent targeted in this project is expected to act not only on actively growing bacteria but also on dormant bacilli. Furthermore, because it targets a novel mechanism distinct from those of existing tuberculosis drugs, it may also be effective against multidrug-resistant tuberculosis.

Effective elimination of both active and dormant bacteria could eradicate asymptomatic infection, leading to shorter treatment durations, prevention of relapse, and suppression of disease transmission. This project is therefore expected to contribute to the treatment of drug-resistant tuberculosis, reduction of patient burden through shorter therapy, and long-term control of tuberculosis by eliminating its reservoir.

What sort of innovation are you bringing in your project?

Most existing tuberculosis drugs primarily target actively growing bacteria with high metabolic activity and show limited efficacy against dormant bacilli. As a result, current therapies have not succeeded in substantially shortening treatment duration.

In this project, we focus on a protein that is believed to play a critical role in the transition of M. tuberculosis into dormancy and adopt a novel approach to inhibit its function. Because this target differs from those of existing drugs, the approach may also be effective against multidrug-resistant tuberculosis.

By acting on both replicating and dormant bacteria, this strategy has the potential to shorten treatment duration, prevent relapse, and eliminate asymptomatic infection that serves as the reservoir of tuberculosis. This dual-action concept represents the major innovative aspect of the project.

Role and Responsibility of Each Partner

Niigata University will be responsible for overall project management, as well as the production and purification of compounds used in the studies, and for supplying these compounds to all partner institutions. In collaboration with TB Alliance, Niigata University will also conduct various preclinical evaluations, including ADME studies and pharmacokinetic (PK) analyses.

Cornell University will evaluate the effects of the compounds against Mycobacterium tuberculosis in vitro, including analyses of anti-tuberculosis activity and mechanisms of action.

Colorado State University will perform efficacy studies using animal models of tuberculosis infection to assess therapeutic effects in vivo.