FDA Approves Pretomanid for Highly Drug-Resistant Forms of Tuberculosis

In continuation of my update on Pretomanid

 Pretomanid, a novel compound developed by the non-profit organization TB Alliance, was approved by the U.S. Food & Drug Administration (FDA) today for treating some of the most drug-resistant forms of tuberculosis (TB).1 The new drug was approved under the Limited Population Pathway for Antibacterial and Antifungal Drugs (LPAD pathway) as part of a three-drug, six-month, all-oral regimen for the treatment of people with extensively drug-resistant TB (XDR-TB) or multidrug-resistant TB (MDR-TB) who are treatment-intolerant or non-responsive (collectively “highly drug-resistant TB”).1,2

The LPAD pathway was established by FDA as a tool to encourage further development of antibacterial and antifungal drugs to treat serious, life-threatening infections that affect a limited population of patients with unmet needs. 

“FDA approval of this treatment represents a victory for the people suffering from these highly drug-resistant forms of the world’s deadliest infectious disease,” said Mel Spigelman, MD, president and CEO of TB Alliance. “The associated novel regimen will hopefully provide a shorter, more easily manageable and highly efficacious treatment for those in need.”

The three-drug regimen consisting of bedaquiline, pretomanid and linezolid – collectively referred to as the BPaL regimen – was studied in the pivotal Nix-TB trial across three sites in South Africa. The trial enrolled 109 people with XDR-TB as well as treatment-intolerant or non-responsive MDR-TB.2

Nix-TB data have demonstrated a successful outcome in 95 of the first 107 patients after six months of treatment with BPaL and six months of post-treatment follow-up.2 For two patients, treatment was extended to nine months. The new drug application contains data on 1,168 people who have received pretomanid in 19 clinical trials that have evaluated the drug’s safety and efficacy.2 Pretomanid has been clinically studied in 14 countries.

TB, in all forms, must be treated with a combination of drugs; the most drug-sensitive forms of TB require six months of treatment using four anti-TB drugs.3 Treatment of XDR-TB or treatment-intolerant/non-responsive MDR-TB has historically been lengthy and complex; most XDR-TB patients currently take a combination of as many as eight antibiotics, some involving daily injections, for 18 months or longer.3,4 Prior to recent introduction of new drugs for drug-resistant TB, the World Health Organization (WHO) has reported estimates for treatment success rates of XDR-TB therapy at approximately 34 percent and about 55 percent for MDR-TB therapy.4

“Until very recently, people infected with highly drug-resistant TB had poor treatment options and a poor prognosis,” said Dr. Francesca Conradie, principal investigator of the Nix-TB trial. “This new regimen provides hope with 9 out of 10 patients achieving culture negative status at 6 months post-treatment  with this short, all-oral regimen."

Pretomanid is a new chemical entity and a member of a class of compounds known as nitroimidazooxazines. TB Alliance acquired the developmental rights to the compound in 2002. It has been developed as an oral tablet formulation for the treatment of TB in combination with bedaquiline and linezolid, two other anti-TB agents, and is now indicated for use in a limited and specific population of patients.1 Adverse reactions reported during the Nix-TB trial of the BPaL regimen include hepatotoxicity, myelosuppression, as well as peripheral and optic neuropathy.1 Please see additional safety information in the Important Safety Information below.

Pretomanid is only the third new anti-TB drug approved for use by FDA in more than 40 years, as well as the first to be developed and registered by a not-for-profit organization.5,6 Pretomanid was granted Priority Review, Qualified Infectious Disease Product, and Orphan Drug status. As a product development partnership, TB Alliance has collaborated with and received significant support from numerous governments, academia, philanthropic institutions, the private sector, civil society organizations and other partners over the course of pretomanid’s development.

Pretomanid is expected to be available in the United States by the end of this year. In addition to the U.S. FDA, TB Alliance has submitted pretomanid as part of the BPaL regimen for review by the European Medicines Agency and has provided data to the World Health Organization for consideration of inclusion in treatment guidelines for highly drug-resistant TB.

https://en.wikipedia.org/wiki/Pretomanid

TB Medicine Pretomanid Enters Regulatory Review Process in the United States

 TB Alliance’s new drug application (NDA) for the novel tuberculosis (TB) drug candidate pretomanid has been accepted for review by the United States Food and Drug Administration (FDA). The application is for the use of pretomanid as part of a new regimen, in combination with bedaquiline and linezolid, for the treatment of extensively drug-resistant (XDR) TB, treatment intolerant multidrug-resistant (MDR) TB, and treatment non-responsive MDR-TB.

The NDA for pretomanid has been granted Priority Review by FDA. The Prescription Drug User Fee Act (PDUFA) action date for an FDA decision is in third quarter 2019.

TB Alliance will work with manufacturing partners to ensure that pretomanid, if approved for use in the BPaL regimen, will be accessible to those who need it.

About Pretomanid and the BPaL Regimen

Pretomanid is a new chemical entity and a member of a class of compounds known as nitroimidazooxazines. It has been studied in 20 clinical trials alone or in combination with other anti-TB drugs. Since TB Alliance began development of pretomanid in 2002, it has been administered in a clinical trial setting to more than 1,200 people in 14 countries.

The BPaL regimen (comprised of bedaquiline, pretomanid and linezolid) was first studied clinically in the Phase 3 Nix-TB trial. Nix-TB participants with XDR-TB and treatment intolerant or nonresponsive MDR-TB were enrolled for treatment with the BPaL regimen for six months, extendable to nine months, with the intent to cure. Nix-TB is an open label, single arm trial. According to a modified intention-to-treat analysis of interim results on the first 75 participants presented at the 2018 Union World Conference on Lung Health, 89% of the trial participants had a favorable outcome with their clinical infection resolved and sputum cultures negative for TB after six months of treatment and six months of post-treatment follow-up.

https://www.tballiance.org/portfolio/compound/pretomanid

https://en.wikipedia.org/wiki/Pretomanid

https://www.drugbank.ca/drugs/DB05154

TB Medicine Pretomanid Enters Regulatory Review Process in the United States

Mycobacterium tuberculosis is extraordinarily sensitive to killing by a vitamin C-induced Fenton reaction : Nature Communications : Nature Publishing Group

In a striking, unexpected discovery, researchers at Albert Einstein College of Medicine of Yeshiva University have determined that vitamin C kills drug-resistant tuberculosis (TB) bacteria in laboratory culture. The finding suggests that vitamin C added to existing TB drugs could shorten TB therapy, and it highlights a new area for drug design.

Dr. Jacobs and his colleagues observed that isoniazid-resistant TB bacteria were deficient in a molecule called mycothiol. "We hypothesized that TB bacteria that can't make mycothiol might contain more cysteine, an amino acid," said Dr. Jacobs. 

"So, we predicted that if we added isoniazid and cysteine to isoniazid-sensitive M. tuberculosis in culture, the bacteria would develop resistance. Instead, we ended up killing off the culture  something totally unexpected."

The Einstein team suspected that cysteine was helping to kill TB bacteria by acting as a "reducing agent" that triggers the production of reactive oxygen species (sometimes called free radicals), which can damage DNA.

"To test this hypothesis, we repeated the experiment using isoniazid and a different reducing agent vitamin C," said Dr. Jacobs. "The combination of isoniazid and vitamin C sterilized the M. tuberculosis culture. We were then amazed to discover that vitamin C by itself not only sterilized the drug-susceptible TB, but also sterilized MDR-TB and XDR-TB strains."

To justify testing vitamin C in a clinical trial, Dr. Jacobs needed to find the molecular mechanism by which vitamin C exerted its lethal effect. More research produced the answer: Vitamin C induced what is known as a Fenton reaction, causing iron to react with other molecules to create reactive oxygen species that kill the TB bacteria.

"We don't know whether vitamin C will work in humans, but we now have a rational basis for doing a clinical trial," said Dr. Jacobs. "It also helps that we know vitamin C is inexpensive, widely available and very safe to use. At the very least, this work shows us a new mechanism that we can exploit to attack TB.".....

Ref : http://www.einstein.yu.edu/news/releases/907/study-finds-vitamin-c-can-kill-drug-resistant-tb/


Mycobacterium tuberculosis is extraordinarily sensitive to killing by a vitamin C-induced Fenton reaction : Nature Communications : Nature Publishing Group

Diabetes drug can boost efficacy of TB medication without causing drug resistance

In continuation of my update on Metformin

A more effective treatment for tuberculosis (TB) could soon be available as scientists have discovered that Metformin (MET), a drug for treating diabetes, can also be used to boost the efficacy of TB medication without inducing drug resistance.

This discovery was made by a team of international scientists led by the Singapore Immunology Network (SIgN), a research institute under the Agency for Science, Technology and Research (A*STAR), Singapore.

TB is an air-borne infectious disease caused by a bacterium called Mycobacterium tuberculosis (Mtb), which often infects the lungs. Even though drugs are available to treat the disease, TB continues to be a major threat to public health, killing close to 1.5 million people every year .

Conventional drugs used to treat TB usually adopt a pathogen-targeted strategy which attacks and kills bacteria directly. This approach has caused Mtb strains to acquire drug resistance, making existing treatments become increasingly ineffective and resulting in a pressing need to design new therapeutic strategies for the disease.

MET as an adjunct treatment for TB

The team of scientists led by SIgN began searching for drugs that could control Mtb replication indirectly. They screened FDA-approved drugs and identified MET, an old anti-diabetic drug that could defend Mtb invasion without targeting the bacteria directly. Instead, MET targets the host cells to trigger the production of a chemical which then damages Mtb and stops its replication. Such indirect, host-targeted approach is less likely to engender drug resistance. The team also discovered that MET improves the efficacy of conventional anti-TB drugs when used in combination with them.

The scientists then validated the findings with patient data provided by the Tuberculosis Clinical Unit at the Tan Tock Seng Hospital, and consequently verified that the use of MET is indeed associated with improved TB control and decreased disease severity. This anti-diabetic drug is therefore a promising adjunctive therapy that could enhance the effectiveness of existing TB treatments. As it is a drug that is currently in use, another benefit of using MET as an adjunct treatment for TB is that it is likely to shorten the time required for clinical trials.

Diabetes drug can boost efficacy of TB medication without causing drug resistance

Developing the First Novel Drug Regimen from TB Alliance...

TB Alliance’s push to test new drugs in combination has been done to produce a regimen that not only would be faster and easier for patients, but also would tackle two other challenges as a major step in stopping the spread of drug-resistant TB—the complexity and high cost of treatment. This promising regimen eliminates the use of injectables and projects to reduce the cost of MDR-TB therapy by as much as 90 percent.

The study, NC-001, or New Combination 1, was a two-week trial successfully completed at two centers in South Africa. It involved the new combination therapy called PaMZ, consisting of the novel TB drug candidate, PA-824 (see below structure left); moxifloxacin (right structure), an established antibiotic not yet approved for use in first-line TB therapy and being developed in partnership with Bayer Healthcare AG; and pyrazinamide, an existing TB drug.

“Treating drug-sensitive and drug-resistant TB with the same regimen can simplify the delivery of TB treatment worldwide,” said Andreas Diacon, MD, the trial’s principal investigator and lead author of the Lancet study. “The results of this study give healthcare providers on the front lines of the TB epidemic hope for better, faster tools needed to stop this disease.”

 (Pyrazinamide)

Newscenter | Global Alliance for TB Drug Development

PA-824 - Aerosol: New Tool Against Tuberculosis?

We know the epidemic rates of HIV/TB coinfection as well as emerging multidrug-resistant  (MDR) and extensively drug-resistant (XDR) TB strains those are contributing to increased TB-associated deaths worldwide. 

Now PA-824 (see structure), a compound capable of being formulated into a dry powder, has not only shown promising activity against MDR (multidrug-resistant tuberculosis) and XDR (extensively drug-resistant tuberculosis, or latent TB) but has also proven safe and effective in patients coinfected with HIV and TB. Previous studies showed that PA-824 was well-tolerated in tablet form, however, side effects such as headache and stomach discomfort were reported. Aerosol delivery of PA-824 directly to the primary site of infection would limit systemic exposure and ultimately eliminate potentially bothersome side effects.

About  PA-824 :

Nitroimidazoles are widely used drugs in humans for a variety of primarily anaerobic microbial infections. Metronidazole, a 5-nitroimidazole, is an important bactericidal agent for the treatment of anaerobic infections  and shows excellent selective toxicity toward anaerobic bacterial and protozoal pathogens. This class of compounds has only recently begun to be explored for Mtb, because only anaerobic activity of metronidazole against Mtb has been reported. Bicyclic 4-nitroimidazoles such as PA-824 (a nitroimidazo-oxazine) and CGI-17341 (a nitroimidazo-oxazole) have inhibitory activity against aerobically growing and nonreplicating anaerobic Mtb. Although anaerobic conditions have not been demonstrated during TB disease in humans, various authors have suggested that an anaerobic microenvironment may contribute to a nonreplicating state that may be linked with latent disease in humans. Thus, PA-824 has been developed, in part, because it may be a promising lead for therapy against latent disease that may be linked to anaerobically persisting bacilli. The Global Alliance for TB Drug Development has recently initiated phase-I clinical trials with PA-824 

Researchers from the University of North Carolina School of Pharmacy, Chapel Hill, North Carolina; and Harvard School of Engineering and Applied Sciences, Cambridge, Massachusetts, lead by  Dr. Anthony J Hickey  have achieved this interesting finding, i.e., potential use of PA-824 dry powder aerosols in the treatment of TB.

In the study guinea pigs were used to evaluate the effects of PA-824 aerosols on TB infection. One month following infection with TB some guinea pigs received high daily aerosol treatments while others received low daily treatments for 4 weeks. Lung and spleen analysis of guinea pigs receiving the high dose of aerosol PA-284 showed less inflammation, bacterial burden and tissue damage.

"The present studies indicate the potential use of PA-824 dry powder aerosols in the treatment of TB,” say the researchers".

Ref : http://aac.asm.org/cgi/content/abstract/54/4/1436.

Ancient Chinese medicine for malaria could potentially aid in treatment of tuberculosis

In continuation of my update on Artemisinin

A centuries-old herbal medicine, discovered by Chinese scientists and used to effectively treat malaria, has been found to potentially aid in the treatment of tuberculosis and may slow the evolution of drug resistance.

In a promising study led by Robert Abramovitch, a Michigan State University microbiologist and TB expert, the ancient remedy artemisinin stopped the ability of TB-causing bacteria, known as Mycobacterium tuberculosis, to become dormant. This stage of the disease often makes the use of antibiotics ineffective.

The study is published in the journal Nature Chemical Biology.

"When TB bacteria are dormant, they become highly tolerant to antibiotics," Abramovitch said, an assistant professor in the College of Veterinary Medicine. "Blocking dormancy makes the TB bacteria more sensitive to these drugs and could shorten treatment times."

One-third of the world's population is infected with TB and the disease killed 1.8 million people in 2015, according to the Centers for Disease Control and Prevention.

Mycobacterium tuberculosis, or Mtb, needs oxygen to thrive in the body. The immune system starves this bacterium of oxygen to control the infection. Abramovitch and his team found that artemisinin attacks a molecule called heme, which is found in the Mtb oxygen sensor. By disrupting this sensor and essentially turning it off, the artemisinin stopped the disease's ability to sense how much oxygen it was getting.

"When the Mtb is starved of oxygen, it goes into a dormant state, which protects it from the stress of low-oxygen environments," Abramovitch said. "If Mtb can't sense low oxygen, then it can't become dormant and will die."

Abramovitch indicated that dormant TB can remain inactive for decades in the body. But if the immune system weakens at some point, it can wake back up and spread. Whether it wakes up or stays 'asleep' though, he said TB can take up to six months to treat and is one of the main reasons the disease is so difficult to control.

"Patients often don't stick to the treatment regimen because of the length of time it takes to cure the disease," he said. "Incomplete therapy plays an important role in the evolution and spread of multi-drug resistant TB strains."

He said the research could be key to shortening the course of therapy because it can clear out the dormant, hard-to-kill bacteria. This could lead to improving patient outcomes and slowing the evolution of drug-resistant TB.

After screening 540,000 different compounds, Abramovitch also found five other possible chemical inhibitors that target the Mtb oxygen sensor in various ways and could be effective in treatment as well.

"Two billion people worldwide are infected with Mtb," Abramovitch said. "TB is a global problem that requires new tools to slow its spread and overcome drug resistance. This new method of targeting dormant bacteria is exciting because it shows us a new way to kill it."

Ref : http://www.nature.com/nchembio/journal/vaop/ncurrent/full/nchembio.2259.html

Eliminating inherent drug resistance in tuberculosis....

In continuation of my update on drug resistant TB and the drug development for TB, I found this info interesting to share with.

Dr. John Blanchard of the Albert Einstein College of Medicine has come up with really  interesting  findings about how to "eliminate inherent drug resistance in tuberculosis".   

When the M. tuberculosis genome was sequenced a few years ago, the presence of  beta-lactamase enzyme was discovered. Most scientists didn't pay much attention to this discovery and beta-lactams   never have been systematically used to treat TB. However Dr. John,  thought it would be an attractive therapeutic target, considering several beta-lactamase inhibitors had been developed for other bacteria.

If we could inactivate this inactivator enzyme, it would expose TB bacteria to a whole new range of antibiotics," he says. 

While M. tuberculosis was resistant to most beta-lactamase inhibitors,  Blanchard's group found that the drug clavulanate was effective in shutting down the TB enzyme. 

The combination of clavulanate (see above right structure- its potassium salt) with the beta-lactam   meropenem (see below: left structure) could effectively sterilize laboratory cultures of TB within two weeks, including several XDR-strains (XDR strains are even more resilient than multi-drug resistant (MDR) strains).  Blanchard notes this finding was exciting since, despite such high rates of drug resistance, research into new TB drugs is not a high priority in industrialized countries (for socio-economic reasons), and thus the best short-term approach might be identifying other already FDA approved antibiotics that are effective against TB -like meropenem and clavulanate.

Blanchard is currently progressing with the next steps of the therapeutic process, which includes both detailed animal studies and setting up some small-scale trials with XDR-TB patients in developing nations...

(Source : a presentation at the American Society for Biochemistry and Molecular Biology’s annual meeting, titled “Drug resistance in tuberculosis,” by Dr. John Blanchard).

Ref : http://www.asbmb.org/News.aspx?id=7470&terms=John+Blanchard

A New approach for the TB drug discovery ?

We are aware that the development of new drugs to combat tuberculosis (TB) has become urgent, as strains of TB resistant to all major anti-TB drugs have emerged worldwide. The World Health Organization estimates that one third of the world's population is asymptomatically infected with TB and that ten percent will eventually develop the disease. More over people with HIV are more prone to TB and hence the need is urgent. As it has happened in other fields of drug discoveries, its something really interesting now it’s the turn of TB drugs, thanx to Barbara Gerratana, Asst., Prof.,. of Chemistry and Biochemistry, university's College of Chemical and Life Sciences, Maryland for their achievement. The significance of the research lies in the fact that “ the NAD+ synthetase enzyme is essential for the survival of the tuberculosis bacteria and hence it can be considered as a drug target.”. So even the structure based inhibitors specific for M. tuberculosis NAD+ synthetase, can be tried and tested for the tuberculosis activity.

Even the experts are really happy over the outcome of the research and following are the lines of appreciation from Clifton E. Barry, Chief of the Tuberculosis Research Section of the Intramural Research Division of the National Institute of Allergy and Infectious Diseases “NadE [NAD+ synthetase] represents one of a small handful of TB drug targets that has iron-clad validation, the lack of a crystal structure was the only serious impediment to drug development and this study represents a hugely important step forward. Inhibiting NadE even kills non-replicating cells, so this discovery may well benefit the one-third of the human population that carries latent bacteria.".

Most interesting part of the research is the fact that “there are only two pathways involved in producing NAD+ in the tuberculosis bacterium and both depend on the activity of NAD+ synthetase to obtain NAD+ (unlike in human beings, where in several different complex pathways..). One can target these two pathways and get good drugs, those are essential and there by one can overcome the drawbacks of the present drugs (current treatment of tuberculosis targets the active tuberculosis bacterium and has little effect on the non-replicating bacterium). Once again congrats for the research group……

A new avenue for TB therapy !

TB bacteria actually sends signals that encourage the growth of those organized granuloma structures, and for good reason: each granuloma serves as a kind of hub for the infectious bugs in the early stages of infection, allowing them to expand further and spread throughout the body. Which is something interesting in he sense that the earlier believed fact (i.e., masses of immune cells that form as a hallmark of tuberculosis (TB) have long been thought to be the body's way of trying to protect itself by literally walling off the bacteria) is being ruled out?. Scientists thought they were protective, but they are not - at least not in early infection. The bacteria use them to reproduce and disseminate themselves.
Not only do the bacteria expand themselves within the first granuloma to form, she added, but some of the immune cells in that initial mass leave to start new granulomas elsewhere. Those new granulomas then also serve as breeding grounds for the bacteria. The finding (Lalita Ramakrishnan and J.Davis). suggests a new avenue for TB therapy at an important time in the struggle against TB infection (not only the increasing number of patients, AIDS with TB and drug resistant TB). So if one can prevent granulomas that might be therapeutic either by intercepting the bacterial signal that spurs granulomas' formation or by manipulating the human immune system in some other way. Hope this research will go a long way in finding the solution to the epidemic drug resistant TB........

New Antituberculosis Compounds ?

We all know how TB has become a pandemic and several attempts to eradicate the disease have been tried and scientists are still finding new ways. However the most disadvantage part for the scientists lies in the fact that "the disease-causing bacteria have a sophisticated mechanism for surviving dormant in infected cells". i.e., TB bacteria have a sophisticated way to remove the damaged proteins — a protein-cleaving complex known as a proteasome — identified in earlier research by the Nathan lab. By breaking down damaged proteins, the proteasome allows the bacteria to remain dormant, and possibly go on to cause active TB. And hence finding drugs to disable the proteasome would be a new way to fight TB.

In developing proteasome-inhibitor drugs, scientists face several hurdles. A significant one is the fact that human cells also possess proteasomes, which are essential to their survival. To be effective, the drugs would have to specifically target the TB proteasome without adversely affecting the human protein-cleanup complex.

This study represents a shift in strategy for designing antibiotics that treat TB, says Dr. Lin (Assistant Research professor of Microbiology and Immunology at Weill Cornell Medical College). All the groups who tried focused on developing drugs that attacked the bacterium in its active phase, but this group has found a compound that may help to destroy it in its dormant stage.

The Weill Cornell team screened 20,000 compounds for TB proteasome inhibition activity. They identified and synthesized a group of inhibitors, which they then tested for their ability to inhibit the proteasome inside the mycobacteria. They also tested the compounds' effect on monkey epithelial cells and human immune system cells in culture. After reading this article, I could recollect the High Throughput Screening of my compounds (Southern Research Institute, Birmingham).  The newly synthesized compounds are specific, less toxic, more active and more over the inhibition of the TB proteasome is irreversible and about 1,000-fold more effective than the minor inhibition observed against human proteasomes.

The structural studies revealed that the inhibitor molecules block the proteasome's ability to degrade proteins in more than one way: by producing a direct chemical change to the proteasome active site, and by altering the conformation of the "pocket" into which protein fragments bind before being degraded. Congrats for this efforts and all the best for their future endeavor.... More....

Self-Poisoning of Mycobacterium tuberculosis by targeting GlgE in an a-glucan pathway...

In the past few years, extremely drug resistant strains of TB have arisen that can’t be eliminated by any drugs, so new strategies for attacking TB are urgently needed.

Now, researchers at Albert Einstein College of Medicine of Yeshiva University have found two novel ways of killing the bacteria that cause tuberculosis.

In searching for a new Achilles’ heel for M. tuberculosis, Dr. Jacobs and colleagues focused on an enzyme called GlgE. Previous research had suggested  that GlgE might be essential for the growth of TB bacteria.        (building polysaccharides) GlgE would also be an excellent drug target because there are no enzymes similar to it in humans or in the bacteria of the human gut.

Using genetic and biochemical approaches, William Jacobs and colleagues identified four enzymes involved in a pathway that converts a naturally-occurring sugar compound into polysaccharides called alpha-glucans. The scientists found that inactivating one of these enzymes, TreS, was not lethal to the bacteria, indicating that this pathway is not required for growth. 

However, inactivating GlgE was lethal, causing the buildup of toxic levels of the enzyme's sugar substrate, maltose-1-phosphate. In addition, the scientists found that the combined inactivation of TreS and an enzyme for an alternate alpha-glucan biosynthetic pathway was lethal, highlighting the important roles of alpha-glucan's in M. tuberculosis growth.

Sure enough, when the researchers inhibited GlgE, the bacteria underwent "suicidal self-poisoning": a sugar called maltose 1-phosphate accumulated to toxic levels that damaged bacterial DNA, causing the death of TB bacteria grown in Petri dishes as well as in infected mice.

The researchers discovered a second way of killing TB after observing a crucial connection between their novel alpha glucan pathway and a second pathway that also synthesizes alpha glucans. 

When the researchers knocked out one of the other enzymes in their novel pathway, the pathway's shutdown didn't kill the bacteria; similarly, inactivating an enzyme called Rv3032 in the second alpha glucan pathway failed to kill the microbes. But inactivating both of those enzymes caused what the researchers term synthetic lethality: two inactivations that separately were nonlethal but together cause bacterial death. 

Though the biological role of the GlgE pathway remains to be elucidated, GlgE and the alpha-glucan pathways more generally, are possible drug targets that can now be tested in in vivo models of tuberculosis infection....

"The bacteria that cause TB need to synthesize alpha glucans," notes Dr. Jacobs. "And from the bacterial point of view, you can't knock out both of these alpha glucan pathways simultaneously or you're dead. So if we were to make drugs against GlgE and Rv3032, the combination would be extremely potent. And since TB bacteria need both of those alpha glucan pathways to live, it's very unlikely that this combination therapy would leave behind surviving bacteria that could develop into resistant strains."

Ref :  http://www.nature.com/nchembio/journal/vaop/ncurrent/pdf/nchembio.340.pdf

Researchers identify potential way to combat TB

Researchers have identified a potential way to manipulate the immune system to improve its ability to fight off tuberculosis (TB).

TB is a major problem for both humans and cattle and the new findings could help scientists to create better drugs to combat the disease in both.

The disease is caused by the bacterium Mycobacterium tuberculosis, which infects the lungs. The mycobacteria are able to establish persistent TB infections by taking up residence in macrophages - cells of the immune system that would normally destroy invading microorganisms.

Now, in early stage research published in the Journal of Biological Chemistry, researchers from Imperial College London and Stanford University have revealed precisely how unusual sugars on the surface of the mycobacteria that cause TB are able to latch onto the macrophages and disarm them. They now hope that scientists at Imperial and elsewhere can use this knowledge to develop small molecule drugs that latch tightly onto the same site.

These drugs could potentially fight tuberculosis in a number of ways, say the researchers. They could create a barrier to prevent the mycobacteria from attaching to the macrophages; they could transport drugs to kill the mycobacteria; or they could change how the macrophages behave, so that they destroy the mycobacteria rather than harbouring them.

Professor Kurt Drickamer, a lead author of the research from the Department of Life Sciences at Imperial College London, said: "TB is hard to fight effectively because it can hide inside the cells of the immune system that should be able to destroy it. We were surprised to find that there is an extensive interaction between the macrophage and one particular type of molecule on the surface of the mycobacteria. The nature of the interaction gives us hope that we can make simple molecules that block the ability of the mycobacteria to subvert the macrophages.

Ref : http://www.jbc.org/content/288/40/28457.abstract?sid=eeb4801e-b429-4bbf-b0cd-446229088668

"Researchers identify potential way to combat TB

New TB vaccine ?

         On March 11, I did mention about the improvement for the existing BCG vaccine for tuberculosis. But this is something really interesting a new vaccine (AdAg85A vaccine) for TB, has been developed using a genetically modified adenovirus by a group of researchers lead by Prof. Zhou Xing of McMaster University. 
 

     As we are aware TB ranks second only to HIV among infectious killers worldwide, claiming nearly two million lives annually. The disease is evolving faster than therapies with the emergence in recent years of strains that are resistant to every last one of the antibiotic defences. This reserach is of great importance because of the fact that  new TB vaccine using a genetically modified adenovirus - a virus responsible for the common cold. After removing a small portion of the gene, they inserted part of the TB gene responsible for immunity. It is natural ways of making the body use its own immune machinery.

 

   And going by the claims that (based on all pre-clinical studies carried out on animals, including mice, guinea pigs -who are very prone to TB  and cattle), this vaccine appears to be a very promising candidate vaccine.

  Once they will be able to conlcude (may be after mid April/May), about the safety of the vaccine, this research will go a long way in the history of TB research... Congrats Prof. Xing and group.  More..

Beating Drug-Resistant TB.....

An antibiotic produced naturally by common soil bacteria kills Mycobacterium species that cause various human diseases, including tuberculosis (TB), according to a report published Monday (September 17) in EMBO Molecular Medicine. The antibiotic even kills drug-resistant strains that escape current TB treatments.

“I seldom get so tickled when I read a paper,” said William Jacobs, a microbiologist and immunologist at the Albert Einstein College of Medicine in New York, who did not participate in the research. The emergence of multidrug resistant strains of Mycobacterium tuberculosis “is a big problem,” he said. “This could be a godsend.”

Tuberculosis infections are commonly treated with a mixture of antibiotics, including one called isoniazid, which Jacobs described as “the cornerstone of TB therapy.”  Unfortunately, the most common drug-resistant strains of M. tuberculosis are isoniazid-resistant, he said.

Many researchers, including Stewart Cole, chair of the microbial pathogenesis department at the École Polytechnique Fédérale de Lausanne in Switzerland, have thus been searching for new M. tuberculosis-killing drugs. “In the past we’ve been working a lot on TB drug discovery using target-based approaches… [but] this has been spectacularly unsuccessful,” said Cole. So instead, he and his colleagues looked back over decades of academic literature searching for reports of natural compounds with M. tuberculosis-killing activity.

They found pyridomycin (see above structure). First described in the 1950s, the drug was reportedly produced by the bacteria Streptomyces pyridomyceticus and Dactylosporangium fulvum. Surprisingly, little was known about pyridomycin—perhaps, Cole suggested, because isoniazid was discovered around the same time and simply stole the limelight.

Cole’s team grew cultures of D. fulvum bacteria, figured out how to isolate and purify pyridomycin, and then showed that the drug was indeed capable of killing M. tuberculosis, as well as many otherMycobacterium species, in culture.

This indiscriminate Mycobacterium-killing ability is a bonus, said Cole. “One of the problems with isoniazid is that it only works against TB,” he said. “If pyridomycin makes it into the clinic, it could have applications in leprosy or Buruli ulcer or atypical mycobacterial infections that can occur in cystic fibrosis patients.”

The team went on to identify the bactericidal target of pyridomycin—a protein called inhA, which is involved in synthesis of bacterial cell wall components. As it happens, inhA is the same protein targeted by isoniazid, but there is a difference in the two drugs’ mechanisms. While isoniazid is a pro-drug that requires activation by an intracellular enzyme called KatG before it can bind to inhA, pyridomycin binds inhA directly.

This is an important distinction, explained Valerie Mizrahi, director of the Institute of Infectious Disease and Molecular Medicine at Cape Town University, South Africa, who was not involved in the study. The overwhelming majority of drug resistance mutations in M. tuberculosis occur in the KatGgene, she explained, and such mutant strains should not be resistant to pyridomycin. Indeed, the team showed that clinical isolates of isoniazid-resistant M. tuberculosis carrying KatG mutations were killed effectively by pyridomycin. “The efficacy against drug resistant forms of M. tuberculosis is particularly encouraging,” Mizrahi said.

There is, however, much to be done before pyridomycin can be used in the clinic. “We would [need to] test that it works in animal models and that it is safe and doesn’t have any side effects,” said Cole. “That will take a couple of years.”

“It’s a long journey,” agreed Mizrahi, “but the big plus is that they don’t really need to validate inhA as a drug target because inhA is already the most well validated drug target out there… [so] it has got a good head start.”

Ref : http://onlinelibrary.wiley.com/doi/10.1002/emmm.201201689/abstract

Methionine Aminopeptidases from Mycobacterium tuberculosis as Novel Antimycobacterial Targets ..

Suspecting that a particular protein in tuberculosis was likely to be vital to the bacteria's survival, Johns Hopkins scientists screened 175,000 small chemical compounds and identified a potent class of compounds that selectively slows down this protein's activity and, in a test tube, blocks TB growth, demonstrating that the protein is indeed a vulnerable target.

 

This class of chemical compounds attacks TB by inhibiting methionine aminopeptidase (MetAP), an essential enzyme found in organisms ranging from bacteria to humans, and that clearly has been conserved throughout evolution because of its important task of ensuring the proper manufacture of proteins.

Methionine aminopeptidase (MetAP) is a metalloprotease that removes the N-terminal methionine during protein synthesis. To assess the importance of the two MetAPs in Mycobacterium tuberculosis, researchers overexpressed and purified each of the MetAPs to near homogeneity and showed that both were active as MetAP enzymes in vitro. 

 

Researchers screened a library of 175,000 compounds against MtMetAP1c and identified 2,3-dichloro-1,4-naphthoquinone class of compounds as inhibitors of both MtMetAPs. It was found that the MtMetAP inhibitors were active against replicating and aged nongrowing M. tuberculosis. Overexpression of either MtMetAP1a or MtMetAP1c in M. tuberculosis conferred resistance of bacterial cells to the inhibitors. As per the claim by the researchers, knockdown of MtMetAP1a, but not MtMetAP1c, resulted in decreased viability of M. tuberculosis and they conclude  that MtMetAP1a is a promising target for developing antituberculosis agents.

 

The scientists cautioned that although the MetAP inhibitors prevent TB growth in test tubes, they have a long way to go before being declared safe and effective to treat TB patients...

 

"Judging from potency, a MetAP inhibibitor alone probably won't wipe out TB," Liu says. "TB is so hard to treat that the standard therapy involves a cocktail of multiple drugs; no single compound is powerful enough. Our hope is that someday an inhibitor of MetAP will become a new component to enhance the existing therapy."

Ref : Jun O. Liu et.al., Chemistry & Biology, Volume 17, Issue 1, 29 January 2010, Pages 86-97

TB disease mechanism and the molecule to block It - discovered ......

We know about the drug resistant tuberculosis and the havoc its causing, so there is an urgent need to  develop new drugs that can be useful. (have covered some articles on  drug development  for drug resistant TB in my earlier blogs). Many groups have tried to explain the resistance,  but now  researchers from Indiana University School of Medicine have identified a mechanism used by the tuberculosis bacterium to evade the body's immune system and have identified a compound that blocks the bacterium's ability to survive in the host, which could lead to new drugs to treat tuberculosis. 

The focus of the research was TB actions inside macrophages (infection fighting cells in the body's immune system). Macrophage cells' tools include the production of special proteins called cytokines to attack foreign invaders. Infected macrophages can also initiate a self-destruction mechanism called apoptosis, which signals other immune system cells to mount a defense against the infection. 

TB bacteria are able to disable the macrophage defenses by secreting virulent factors into the host. The IU team found that the actions of a particular virulent factor a protein phosphatase enzyme called mPTPB  blocked both the production of the infection-fighting cytokines, and the macrophage's self-destruct system. 

As for as my knowledge goes,  phosphatases  (VE-PTP, Cdc25A, PTP1b, VHR, Shp-2, MptpA und MptpB) the  key regulators of various life processes are being studied for the diverse activities. The following is the brief summary ;

a). VE-TPT inhibition is very promising in the development of antiangiogenesis inhibitors in cancer therapy.
b). Cdc25A influences cell cycle regulation and may also be a target of interest in cancer therapy.
c). The phosphatase MptpB, from Mycobacterium tuberculosis, influences the host's immune 
     reaction in a tuberculosis infection.
d) VHR dephosphorylates MAP kinases in the activation loop THX, which plays an important role in signal
    transduction processes.
e) Inhibiting MptpB and Shp-2 opens up new directions in the search for antibiotics and
f) The Ptp1B enzyme plays an important role in developing a medicine against type 2 diabetes and the
   metabolic syndrome.

Though many researchers  tried to study the mechanism of action by which the  tuberculosis bacterium is getting resistance,  this group has come up with a drug and this is of great significance in my opinion.

Using combinatorial chemical synthesis and high-throughput screening, (HTS) the researchers developed the I-A09 compound, which successfully blocked the action of mPTPB. Tests involving live TB bacteria were conducted at the Institute of Tuberculosis Research, University of Illinois at Chicago. 

As per the claim by the lead researcher, Dr. Zhong-Yin Zhang, compound I-A09 is being evaluated in a TB animal model at the Johns Hopkins University School of Public Health. More potent forms of the I-A09 compound are being pursued by the IU team for possible future clinical testing. Hope the team  will come up with a solution to this problem in the days to come...

Ref : http://www.medicine.indiana.edu/news_releases/viewRelease.php4?art=1232

New Vaccine for TB...!

We are aware that TB has become one of the most dangerous disease (more than two billion people are infected with tuberculosis – approximately one out of every three people on the planet – and 1.8 million die annually from the disease). And also the strain is getting resistance to the single drug and a combination of Rifampicin, Ethumbutol, Isoniazid and Streptomycin a combo of 4 drugs is being used as treatment. And as per the saying "Prevention is better than Cure", a new vaccine is urgently needed, as BCG is currently the only available vaccine against TB, and provides only variable protection against pulmonary tuberculosis, which accounts for most of the worldwide disease burden. Now thanx to Dr Helen McShane, a Wellcome Trust Senior Clinical Research Fellow, working with Dr Sarah Gilbert, a Reader in Vaccinology, and Professor Adrian Hill, a Wellcome Trust Principal Research Fellow- who together achieved a milestone in developing the vaccine and it has entered Phase IIb proof-of-concept clinical trials, making it the first TB candidate vaccine for more than 80 years to get to this advanced stage of clinical trials in infants. There is still a long road ahead, but this marks an important milestone toward the goal of a more effective TB vaccine. First I congratulate for this milestone and wish them all the success in their attempt.

Ref : http://www.ox.ac.uk/media/news_stories/2009/090423.html

Tuberculosis can evade immune response !

As I have mentioned in my earlier blog, more than two million people worldwide die from tuberculosis infection every year. Due in part to inappropriate antibiotic usage, there are a rising number (0.5 million in 2007) of cases of multidrug-resistant (MDR-TB) and extensively drug-resistant (XDR-TB) tuberculosis. New therapies are needed to treat these dangerous infections. We are aware that immune responses to tuberculosis rarely result in complete eradication of the infection. Instead, TB-infected immune cells promote the generation of chronic inflammation and the formation of granulomas, which are areas where the bacteria are contained but not destroyed. These are the facts that encoucouraged Dr. Susanna Grundstrom Brighenti at the Karolinska Institutet in Stockholm, Sweden, to examine the immune response in patients infected with tuberculosis. And this research is of great significance, since it is the first of its kind. The findings are really interesting and justify why the bacterium is getting resistance to the drugs. Following are the important conclusions by the researchers:

The immune cells responsible for killing the tuberculosis bacteria surrounded the granuloma, these cells had low levels of the molecules necessary to kill the TB. Instead, granulomas had high numbers of regulatory immune cells. These regulatory cells suppress the immune response, resulting in the survival of the tuberculosis bacteria and perhaps contributing to persistent long-term infection. Compartmentalization of the immune response in human TB could be part of the reason why infection is never completely eradicated but instead develops into a chronic disease. Congrats for the interesting findings and wish them further success in their future research...

Combination of bedaquiline and verapamil reduces side effects, improves outcomes for TB patients

In continuation of my update on Bedaquiline

While an effective treatment is available for combating multidrug-resistant tuberculosis, it carries serious side effects for patients. New research conducted at the Center for Tuberculosis Research at the Johns Hopkins University School of Medicine shows that lower doses of the toxic drug bedaquiline — given together with verapamil, a medication that's used to treat various heart conditions — can lead to the same antibacterial effects as higher toxic doses of bedaquiline. The combination of the two drugs could potentially shorten treatment time, reduce the side effects of bedaquiline and improve patient outcomes for those suffering from TB.

The study will be published in the January 2014 issue of Antimicrobial Agents and Chemotherapy. The lead author is William Bishai, M.D., Ph.D., co-director of the Center for Tuberculosis Research.

"Using a mouse model of tuberculosis, we have shown lower doses of bedaquiline together with verapamil have the same antibacterial effect as the higher toxic doses," says Shashank Gupta, Ph.D., a research fellow at Johns Hopkins. "A lower dose of bedaquiline will cause no or less severe side effects."

Two years ago, bedaquiline became the first drug in the last four decades to be approved by the U.S. Food and Drug Administration for the treatment of multidrug-resistant TB. The drug works by inhibiting an enzyme used by Mycobacterium tuberculosis to replicate and spread throughout the body. While it can be a lifesaving therapy against one of the world's deadliest diseases, bedaquiline can also cause serious side effects in the heart and liver. Therefore, strategies to reduce the dose of bedaquiline while retaining its antibacterial activity would provide significant benefits to patients.

"Shortening treatment regimens and reducing the required doses may be a promising strategy to reduce the incidence of bedaquiline-related adverse effects and thereby improve multidrug-resistant TB treatment outcomes," says Gupta.

Combination of bedaquiline and verapamil reduces side effects, improves outcomes for TB patients