The Creation Of Lung Surface Tissue In A Dish Could Lead To Treatment For Cystic Fibrosis

Harvard stem cell researchers at Massachusetts General Hospital (MGH) have taken a critical step in making possible the discovery in the relatively near future of a drug to control cystic fibrosis (CF), a fatal lung disease that claims about 500 lives each year, with 1,000 new cases diagnosed annually.

Beginning with the skin cells of patients with CF, Jayaraj Rajagopal, MD, and colleagues first created induced pluripotent stem (iPS) cells, and then used those cells to create human disease-specific functioning lung epithelium, the tissue that lines the airways and is the site of the most lethal aspect of CF, where the genes cause irreversible lung disease and inexorable respiratory failure.

That tissue, which researchers now can grow in unlimited quantities in the laboratory, contains the delta-508 mutation, the gene responsible for about 70 percent of all CF cases and 90 percent of the ones in the United States. The tissue also contains the G551D mutation, a gene that is involved in about 2 percent of CF cases and the one cause of the disease for which there is now a drug.

The work is featured on the cover of this month's Cell Stem Cell journal, which appears online. Postdoctoral fellow Hongmei Mou, PhD, is first author on the paper, and Rajagopal is the senior author.

Mou credits learning the underlying developmental biology in mice as the key to making tremendous progress in only two years. "I was able to apply these lessons to the iPS cell systems," she said. "I was pleasantly surprised the research went so fast, and it makes me excited to think important things are within reach. It opens up the door to identifying new small molecules [drugs] to treat lung disease."

Doug Melton, PhD, co-director of the Harvard Stem Cell Institute, said, "This work makes it possible to produce millions of cells for drug screening, and for the first time human patients' cells can be used as the target." Melton, who is also co-chair of Harvard's inter-School Department of Stem Cell and Regenerative Biology and is the Xander University Professor, added, "I would expect to see rapid progress in this area now that human cells, the very cells that are defective in the disease, can be used for screening."

Rajagopal said, "The key to our success was the ecosystem of the Harvard Stem Cell Institute and MGH. HSCI investigators pioneered the strategies we used, helped us at the bench, and gave us advice on how to combine our knowledge of lung development with their exciting new platforms. Indeed, we also enjoyed a wonderful collaboration with Darrell Kotton's lab at Boston University that was able to convert mouse cells into lung tissue. These interactions really helped fuel us ahead."

The epithelial tissue created by Rajagopal and his colleagues at the MGH Center for Regenerative Medicine also provides researchers with the same cells that are involved in a number of common lung conditions, including asthma, lung cancer, and chronic bronchitis, and may hasten the development of new insights and treatments into those conditions as well.


"We're not talking about a cure for CF; we're talking about a drug that hits the major problem in the disease. This is the enabling technology that will allow that to happen in a matter of years," said Rajagopal, a Harvard Medical School assistant professor of Medicine.

Also a physician trained as a pulmonologist, the specialty that treats CF patients, Rajagopal said, "When we talk about research and advances, donors and patients ask: 'When? How soon?' And we usually hesitate to answer. But we now have every single piece we need for the final push. So I have every hope that we'll have a therapy in a matter of years."

Cystic fibrosis, which used to claim its victims in infancy or early childhood, has evolved into a killer of those in their 30s because treatments of the infections that characterize the disease have improved. But despite those advances, there has been little progress in treating the underlying condition that affects the vast majority of patients: a defect in a single gene that interferes with the fluid balance in the surface layers of the airways and leads to a thickening of mucus, difficulty breathing and repeated infections and hospitalizations.

The discovery and recent FDA approval of the drug Ivacaftor, which corrects the G551D defect seen in about 2 percent of CF patients, has served as a proof of concept to demonstrate that the disease can be attacked with a conventional molecular treatment. In fact, Ivacaftor was found by screening thousands of drugs on a far less than ideal cell line. In the end, many drugs that functioned well on this cell line proved ineffective when used on genuine human airway tissue.

Genuine human airway tissue is the gold standard prior to drugs being tested clinically, but it has been extremely difficult to obtain the tissue from patients, and when it could be obtained, the tissue rarely survived long in the lab - all of which created a major bottleneck in screening for a therapy. But by creating iPS cells that contain the entire genome of a CF patient and directing those cells to develop into lung progenitor cells, which then develop into epithelium, the group appears to have solved this key problem.

Rajagopal, who did his own postdoctoral fellowship in Melton's laboratory during the first half of the past decade after completing his training in pulmonary medicine, said that having both the G551D and 508 genes in the epithelial tissue provides a way to prove that the tissue will be effective in testing drugs against CF.

"We've created the perfect cell line to show that the drug out there that works against G551D mutation works in this system, and then we're in business to screen for a drug against delta 508," he said. "We'll know soon that the cell line works. We know it makes bonafide airway epithelium, and we'll have the proof of principle that the tissue responds properly to the only known drug. We think this is the near-ideal tissue platform to find a drug for the majority of CF."

Rajagopal's lab has created numerous other cell lines to further show that a CF drug that works in one patient should work in others and to see whether this will be an area that allows a more personalized approach to medicine.

"I'm most looking forward to working with the community of pulmonologists that concentrate in CF to generate therapies. This is occurring more than two decades after the remarkable work that identified the CF gene. Looking forward, I'm very excited that CF may lead the way in lung disease once more, by demonstrating that our iPS platform can be used to probe the diseases that are much less well understood. CF has more than two decades of great biology behind it. The reason we chose to attack this disease first was because of that pioneering work that lets us use our system with a very firm foundation.

Molecules Designed By Computer Point To New Therapy For Cystic Fibrosis

By developing software that uses 3-D models of proteins involved in cystic fibrosis, a team of scientists at Duke University has identified several new molecules that may ease the symptoms of the disease.

Computer algorithms created by the team predict how well a given molecular structure will block a basic protein-protein interaction known to occur in cystic fibrosis. To test the predictions, the scientists synthesized the molecules and measured how well they attached to one of the proteins in that interaction. The team then placed the best molecule into human cells with the cystic fibrosis mutation in a laboratory dish and found that their new drug blocked the protein-protein interaction and increased the cells' ability to balance salt and water levels.

The results, which appear in Public Library of Science Computational Biology, suggest that computers could make drug design for cystic fibrosis faster.

"We have known the genetic cause of cystic fibrosis since 1985. Now, by understanding its biology and chemistry, we can design and create targeted drugs to correct for the genetic flaw," said Bruce Donald, a Duke computer scientist and biochemist who led the study.

Cystic fibrosis, or CF, is a childhood disease causing the lungs and pancreas to fill with mucus, making it hard to breathe and absorb nutrients from food. The mucus builds in the organs as the levels of salt and water in the cells become unbalanced because of a defective protein.

That protein, called CFTR, the cystic fibrosis transmembrane conductance regulator, regulates salt and water in the cell. In CF, it is defective because the genes that generate it are mutated. CFTRs are routinely rounded up for recycling in the cell by a protein called CAL that binds to CFTR and hauls it away. But defective CFTR proteins in cystic fibrosis patients send a signal that they are faulty, making their recycling rate much higher.

Currently, no treatments exist to target the genetic mutations that cause cystic fibrosis. Scientists have discovered molecules that target CFTRs' defects, such as incorrect folding and fast recycling, and there are a few molecules that help correct how CFTR folds or slow down the CAL recycling truck. These molecules help keep copies of CFTR functioning in the cell membrane to maintain some balance between salt and water levels.

Donald and his graduate student Kyle Roberts thought that computer algorithms based on the structure of CAL and similar proteins could quickly generate several dozen more molecules for slowing recycling by CAL and increase the pool of potential cystic fibrosis treatments.

"Research shows that you only need a fraction of normal CFTR activity to alleviate cystic fibrosis symptoms, so keeping CFTR in the membrane by using our inhibitors could have a significant therapeutic effect," said Roberts, first author of the new study.

Donald and Roberts' algorithms searched several thousand potential inhibitors and ranked them based on how strongly it predicted each would bind with CAL. In collaboration with researchers at Dartmouth and in Germany, the scientists synthesized 11 of the highest-ranked sequences and used fluorescent light to measure each molecule's attachment to CAL.

The results show that many of the algorithm-generated molecules attach more strongly to CAL than the connection between CAL and CFTR in nature. The best computer-generated molecules also bind more efficiently to CAL than any previously reported inhibitor.

In a culture of human cells with the cystic fibrosis mutation, the best algorithm-generated inhibitor increased CFTR activity by 12 percent. Donald said the new molecule could be used in combination with another molecule, which corrects how CFTR proteins fold and raises CFTR's activity by 15 percent. The two molecules should work together and could increase CFTR's activity by about 27 percent, he said.

He cautioned that it could be several years before patients with the disease could use the new molecular combination as treatment because the molecules have not yet been tested in patients with the disease. The team has made its software freely available, Donald said, so the computer-design approach could quicken the pace at which molecules and resulting cystic fibrosis therapies are developed.

Why 1 Bacterial Infection Is So Deadly In Cystic Fibrosis

Scientists have found why a certain type of bacteria, harmless in healthy people, is so deadly to patients with cystic fibrosis.

The bacterium, Burkholderia cenocepacia, causes a severe and persistent lung infection in patients with CF and is resistant to nearly all known antibiotics. Cystic fibrosis is a chronic disorder characterized by a buildup of mucus in the lungs and other parts of the body, and various types of lung infection are responsible for about 85 percent of deaths in these patients.

The Ohio State University researchers have determined that B. cenocepacia bacteria interfere with an important survival process in cells whose job is to fight infection. This phenomenon is even stronger in CF patients, so the infection exacerbates the cell malfunction.

The research group also showed that rapamycin, an existing drug known to stimulate this cell-survival process, called autophagy, helped control B. cenocepacia infection in mice that serve as a model for cystic fibrosis.

The scientists also dissected the role of a molecule called p62, which plays a role in the autophagy process. They found that p62 inside macrophages, the cells that fight infection, is influential in controlling B. cenocepacia infection.

"This suggests that manipulating p62 levels might help patients with CF fight off the lethal infection," said Amal Amer, assistant professor of microbial infection and immunity and internal medicine at Ohio State and senior author of the study.

The research was presented at the American Society for Biochemistry and Molecular Biology annual meeting, which is held in conjunction with the Experimental Biology 2012 conference in San Diego. The rapamycin findings also were published in a recent issue of the journal Autophagy.

The B. cenocepacia infection remains relatively rare but highly transmissible in patients with cystic fibrosis. "It's really a death sentence for the patient. The disease either progresses with propagation of inflammation and chronic destruction of lung tissue, or acute infection with severe sepsis that occurs very quickly. We don't know which patient will take which course," said Amer, also an investigator in Ohio State's Center for Microbial Interface Biology.

Amer and her colleagues had been studying autophagy in other organisms before experimenting with these bacterial cells. Autophagy allows a cell to digest parts of itself to produce energy when it is experiencing starvation.

"We were among the first to show that autophagy can actually clear infection," Amer said. "So not only is it a physiological pathway in the background all the time, but some bacteria, when they infect cells, will be engulfed by autophagy. And that helps in clearing the infection."

These cells that can use autophagy to clear infection are the macrophages, which are first-responders in the immune system that essentially eat offending pathogens.

Amer and Ohio State doctoral student Basant Abdulrahman showed that macrophages isolated from both mice and humans that carried the most common CF mutation could not clear the B. cenocepacia infection. The bacterium invades the macrophage and just sits there, Amer explained, instead of being digested and cleared away.

Because autophagy was not working in these cells, the researchers tested the effects of the drug rapamycin, an immune-system suppressant that is known to stimulate autophagy, in normal animals and those with the most common CF genetic mutation.

The drug had no real effect on normal mice because they could clear a B. cenocepacia infection on their own, said Abdulrahman, the study's lead author and presenter of the research at Experimental Biology 2012. But in mice with CF, she said, the drug's stimulation of the autophagy process helped these mice clear the bacterial infection from their lungs.

With this strong suggestion that autophagy is a potential target for new CF treatments, the researchers set out to better understand this process in CF macrophages that are unable to fight the B. cenocepacia infection. And that is when they found that p62 shows promise as an even more specific drug target. Additional studies of p62's effects on this bacterial infection are in progress.

Cystic Fibrosis Drug Bronchitol Approved, EU

According to Pharmaxis, Bronchitol, a new cystic fibrosis treatment, has been granted EU approval for patients aged 18 years and older as an add-on therapy to the best standard of care in 29 European countries.

Dr. Alan Robertson, CEO of Pharmaxis announced:

"This is a very significant event, which means that patients living with cystic fibrosis in Europe will now be able to receive the proven clinical benefits of Bronchitol."

The first to benefit from Bronchitol will be CF patients in Germany and the UK, where there is a lower requirement approving prices and reimbursement prior to the drug's launch. Both countries make up 40% of the European market by value. According to Pharmaxis, stock should be available for sale in Europe by June 1st ahead of the product's official launch at the European Cystic Fibrosis Conference in Dublin (6th to 9th June 2012).

Bronchitol has been designed to help clear people's airways who suffer from the world's most common, life-limiting genetic disease - cystic fibrosis. Bronchitol demonstrated in two large Phase III clinical trials that it improved mucus clearance, improved lung function and decreased the number of infectious episodes in comparison to controls after 6 months of therapy. Dr Robertson declared:

"We have built considerable momentum around Bronchitol in recent months with the German and UK sales teams fully recruited and trained. Pharmaxis has now secured three drug approvals in the world's largest pharmaceutical markets: the lung function test Aridol in Europe and the US and now approval for Bronchitol in Europe and Australia. This is a credit not only to the company but also the investigators and patients throughout the world who have taken part in our clinical programs."

Apramycin Shows Promise Against Drug-Resistant TB And Other 'Superbugs,' Without Hearing Loss

The world needs new antibiotics to overcome the ever increasing resistance of disease-causing bacteria - but it doesn't need the side effect that comes with some of the most powerful ones now available: hearing loss. Researchers report that they have developed a new approach to designing antibiotics that kill even "superbugs" but spare the delicate sensory cells of the inner ear.

Surprisingly, they have found that apramycin, an antibiotic already used in veterinary medicine, fits this bill - setting the stage for testing in humans.

In a paper published online in the Proceedings of the National Academy of Sciences, a team from Switzerland, England and the University of Michigan show apramycin's high efficacy against bacteria, and low potential for causing hearing loss, through a broad range of tests in animals. That testing platform is now being used to evaluate other potential antibiotics that could tackle infections such as multidrug-resistant tuberculosis.

The research aims to overcome a serious limitation of aminoglycoside antibiotics, a class of drugs which includes the widely used kanamycin, gentamicin and amikacin.

While great at stopping bacterial infections, these drugs also cause permanent partial hearing loss in 20 percent of people who take them for a short course, and up to 100 percent of people who take them over months or years, for example to treat tuberculosis or lung infections in cystic fibrosis.

U-M researcher Jochen Schacht, Ph.D., a professor of biological chemistry and otolaryngology and director of the Kresge Hearing Research Institute at the U-M Medical School, has spent decades studying why these drugs cause this "ototoxicity" - a side effect that makes doctors hesitant to prescribe them. Hearing damage has also caused patients to discontinue treatment before their antibiotic prescription is over, potentially allowing drug-resistant strains of bacteria to flourish.

Schacht has found that the drugs produce damaging free radicals inside the hair cells of the inner ear. Hair cells, named for the tiny sound-sensing hairs on their surface, are the linchpin of hearing - and once destroyed, cannot be regrown.

In the new paper, Schacht and his research group joined teams led by University of Zurich microbiologist Erik Böttger, and structural biologist and Nobel Prize winner Venkatraman Ramakrishnan of England's Medical Research Council Laboratory of Molecular Biology, as well as scientists from ETH Zurich. Each team brought its particular expertise to the issue, and after four years of work they developed and tested this new approach to designing antibiotics.

"Aminoglycosides are some of the most valuable broad-spectrum antibiotics and indispensable drugs today, but we need new options to combat drug-resistant bacteria. Importantly, we must find ways to overcome their ototoxicity," Schacht says. "Instead of the trial-and-error approach of the past, this new hypothesis-driven tactic allows us to design drugs with simultaneous attention toward both antibacterial action and impact on hair cells."

According to the World Health Organization, about 440,000 new cases of multidrug-resistant tuberculosis emerge annually, causing at least 150,000 deaths worldwide. Aminoglycoside antibiotics, while carefully controlled in the U.S., Europe, and other developed countries are available over the counter in many developing nations, leading to overuse that makes it even easier for drug-resistant strains of many kinds of bacteria to emerge and spread.

The new paper outlines a rational approach to designing drugs to combat this threat without ototoxicity, based on a theoretical framework that emerged from the work of the three laboratories and centers around the role of ribosomes, the structures inside the cell that "read" DNA and translate the genetic message into proteins. Böttger's lab, at the Institut für Medizinische Mikrobiologie which he directs, studies aminoglycoside effects on mitochondrial ribosomes and antibacterial activity with an eye toward designing new ones. Ramakrishnan's lab studies ribosomes, and partners from ETH Zurich also collaborated.

Aminoglycosides bind to the ribosomes inside bacterial cells, preventing the ability to produce proteins. But while the drugs spare most human ribosomes, they can attach to ribosomes in the mitochondria of cells, which are similar to bacterial ribosomes.

Consistent with U-M-generated theories about ototoxicity, the drugs then cause the production of free radicals in such quantities that they overwhelm the hair cells' defense mechanisms - destroying the cells and causing hearing loss.

The team's approach is to design drugs that more specifically target bacterial ribosomes over mitochondrial ribosomes, simultaneously testing the impact on hair cells as well as the ability to kill bacteria. In this way, the researchers try to avoid creating antibiotics that harm hearing.

They are already using the platform employed for this study - which involves cells from mouse ears, and tests of hearing and hair cell damage in guinea pigs - to test other promising novel drugs synthesized based on the theoretical framework that was driving the current research.

Meanwhile, the team hopes to launch a clinical trial of apramycin, an antibiotic that could prove immediately useful because multidrug-resistant TB and lung-infecting bacteria have not shown resistance to the drug yet.

The research also lends more evidence to support the use of antioxidants to protect the hearing of patients taking current aminoglycoside antibiotics. Schacht has already led a clinical trial in China that showed a major reduction in hearing loss if aspirin was given at the same time as aminoglycoside antibiotics. "This kind of protection is important, while we search for the long-term answer to drug resistance without ototoxicity.

DNA From Cystic Fibrosis Patients With And Without Chronic Infections Points To Unsuspected Mutation

Comparing the DNA from patients at the best and worst extremes of a health condition can reveal genes for resistance and susceptibly. This approach discovered rare variations in the DCTN4 gene among cystic fibrosis patients most prone to early, chronic airway infections.

The DCTN4 gene codes for dynactin 4. This protein is a component of a molecular motor that moves trouble-making microbes along a cellular conveyer belt into miniscule chemical vats, called lysosomes, for annihilation.

This study, led by the University of Washington, is part of the National Heart Lung and Blood Institute GO Exome Sequencing Project and its Lung GO, both major National Institutes of Health chronic disease research efforts.

Similar "testing the extremes" strategies may have important applications in uncovering genetic factors behind other more common, traits, such as healthy and unhealthy hearts.

The results of the cystic fibrosis infection susceptibility study appear in Nature Genetics.

The infection in question was Pseudomonas aeruginosa, an opportunistic soil bacterium that commonly infects the lungs of people with cystic fibrosis and other airway-clogging disorders. The bacteria can unite into a slithery, hard-to-treat biofilm that hampers breathing and harms lung tissue. Chronic infections are linked to poor lung function and shorter lives among cystic fibrosis patients. These bacteria rarely attack people with normal lungs and well-functioning immune systems.

In the study, these rare variations in DCTN4 did not appear in any of the cystic fibrosis patients who were the most resistant to Pseudomonas infection. The study subjects most susceptible to early, chronic infection had at least one DCTN4 missense variant. A missense variant produces a protein that likely can't function properly.

The lead author of the report published July 8 in Nature Genetics is Mary J. Emond, research associate professor of biostatistics at the University of Washington School of Public Health in Seattle. The senior author is medical geneticist Michael Bamshad, UW professor of pediatrics in the Division of Genetic Medicine.

To the extent of their knowledge, the researchers think that this might be the first time that genetic variants underlying complex trait were discovered by sequencing all the protein-coding portions of the genomes of people at each extreme of a disease spectrum.

"We did not have a candidate gene in mind when we did this study," said Emond. Statistical analysis of the DNA of 91 patients led the research team to this particular gene. Of the initial study group, 43 children had their first onset of chronic lung infection with Pseudomonas as when they were very young, and the 48 oldest individuals had not yet reached a state of chronic infection. The patients selected for sequencing were from the Early Pseudomonas Control (EPIC) Observational Study, a project at the Seattle Children's Research Institute, and the North American Cystic Fibrosis Genetic Modifiers Study. Exome sequencing was done by UW researchers in the laboratory of Deborah Nickerson, UW professor of genome sciences.

Comparisons of the protein coding portions of the study subjects' DNA called the researchers attention to missense variations of the DCTN4 gene. The researchers went on to screen a selected group of 1,322 other EPIC participants to check their findings.

Exome Sequencing Project scientists are using an approach similar to the one in this study to examine the genetics behind resistance and susceptibility to other chronic conditions like obesity, heart attacks and hypertension. They plumb for gene variations linked to heart disease, for example by putting DNA maps from people with ideal cholesterol levels up against those from people with exceptionally poor levels.

Adapting a similar strategy to determine the genetics underlying other complex human traits may require exome sequencing of a much larger sample sizes, the researchers noted.

"As the costs of exome sequencing are dropping rapidly and more efficient statistical analysis is becoming available, we think medical researchers' enthusiasm for this approach will continue," Bamshad predicted.

Airways More Acidic In Cystic Fibrosis Patients, Less Effective At Killing Bacteria

The human airway is a pretty inhospitable place for microbes. There are numerous immune defense mechanisms poised to kill or remove inhaled bacteria before they can cause problems. But cystic fibrosis (CF) disrupts these defenses, leaving patients particularly susceptible to airway infection, which is the major cause of disease and death in CF.

Using a unique animal model of CF, a team of scientists from the University of Iowa has discovered a surprising difference between healthy airways and airways affected by CF that leads to reduced bacterial killing in CF airways. The finding directly links the genetic cause of CF - mutations in a channel protein called cystic fibrosis transmembrane conductance regulator (CFTR) - to the disruption of a biological mechanism that protects lungs from bacterial infection.

The study, published in Nature, shows that the thin layer of liquid coating the airways is more acidic in newborn pigs with CF than in healthy newborn pigs, and that the increased acidity (lower pH) reduces the ability of the liquid to kill bacteria. Moreover, making the airway liquid less acidic with a simple solution of baking soda restores bacterial killing in CF airways to almost normal levels.

Although the findings suggest that therapies that raise the pH of the airway surface liquid (ASL) may help prevent infection in CF, the researchers strongly caution that this discovery is at an early stage.

"Some have asked us if people with CF should inhale an aerosol that would raise the pH of the ASL," says Joseph Zabner, M.D., UI professor of internal medicine and senior study author. "At this point, we have no idea if that would help. And more importantly, it could be harmful."

"This was a very surprising finding," adds Alejandro Pezzulo, M.D., UI postdoctoral fellow and co-lead author of the study. "There have been many ideas as to what goes wrong in CF, but lack of a good experimental model has made it difficult to gain insight into how the disease gets started."

Unlike mouse models of the disease, the CF pigs develop lung disease that closely mimics what is seen in humans. Previous studies from the UI lab showed that although the airways of CF pigs are infection-free at birth, they are less able to get rid of bacteria than healthy airways and quickly become infected.

Testing bacterial killing in airways

The UI team, including Pezzulo and co-lead author Xiao Xiao Tang, Ph.D., a Howard Hughes Medical Institute postdoctoral research associate at the UI, developed a simple experiment to study bacterial killing by the ASL. They immobilized bacteria on a tiny gold grid and exposed these bacteria to ASL from CF-affected and healthy pigs.

The ASL from normal airways killed most of the bacteria very rapidly, whereas the ASL from CF-affected airways only killed about half of the bacteria, suggesting that in CF airways some bacteria would survive and go on to cause infection.

Further investigation showed that although many characteristics of the ASL in CF and non-CF pigs are similar, the ASL from CF airways is more acidic than the liquid from healthy airways.

When the scientists raised the pH of the ASL in CF pigs through inhalation of a solution of sodium bicarbonate (baking soda), the treated ASL was capable of killing most of the bacteria on the grid (just like ASL from normal airways). Conversely, lowering the pH of ASL from normal airways reduced bacterial killing. The finding confirms that pH is a critical factor for bacterial killing,

"This study explains why a defect in the CFTR channel protein leads to reduced bacterial killing and an airway host defense defect," Tang says. "Impaired bicarbonate transport because of the defective CFTR could cause increased acidity in the ASL, which the study shows reduces the ASL bacterial killing capability."

Potential clinical applications

Although the approach is not ready for clinical application, the study indicates that pH is a contributing factor in airway infection, suggesting that therapies that modify airway pH may potentially be helpful in preventing infection in CF patients.

In addition, the researchers believe that using the bacteria-coated grids to measure bacterial killing in airways might provide a simple way to test the effectiveness of other new CF therapies that currently are being developed.

Kalydeco Recommended For Treatment Of Cystic Fibrosis

About 60,000 Europeans suffer from cystic fibrosis, a rare and life-threatening genetic disorder that is caused by a mutation of the CFTR gene, which regulates salt and water transport in the body. The CFTR mutation in cystic fibrosis patients allows too much salt and water into cells, which results in a build-up of thick, sticky mucus in the body's tubes and passageways that damage the lungs, digestive system and other organs. Symptoms generally occur during early childhood and appear as persistent cough, recurring chest and lung infections and poor weight gain.

The European Medicines Agency (EMA) has recommended an orphan-designated medicine called Kalydeco (ivacaftor) to treat cystic fibrosis in children above the age of 6 years who have a G551D mutation in the cystic fibrosis transmembrane regulator (CFTR) gene. Kalydeco was reviewed in only 150 days by the Committee for Medicinal Products for Human Use (CHMP), under EMAs accelerated assessment procedure, which speeds up the reviewing process to supply patients with new drugs that are of major public health interest.

Unlike currently available therapies, which only address the disease's consequences, Kalydeco is the first treatment that targets the underlying mechanism of cystic fibrosis by restoring the function of the mutated CFTR protein, therefore providing patients with an innovative therapeutic approach.

Kalydeco demonstrated improved pulmonary function in cystic fibrosis patients with the specific G551D-CFTR mutation in clinical studies. The drug's most frequently encountered side effects included abdominal pain, diarrhea, dizziness, rash, upper respiratory tract reactions, including upper respiratory tract infection, nasal congestion, pharyngeal erythema, oropharyngeal pain, rhinitis, sinus congestion and nasopharyngitis, as well as headache and bacteria in sputum. Long-term safety data for Kalydeco is so far unavailable and will therefore, like all newly approved medicines be closely monitored.

So far, three of the eight medicines that have been approved under The Agency's accelerated assessment have been orphan-designated medicines. The Agency is currently waiting for the E.C. to adopt the decision of their recommendations.

New Model Shows How Human Lungs Brush Out Intruders

A runny nose and a wet cough caused by a cold or an allergy may not feel very good. But human airways rely on sticky mucus to expel foreign matter, including toxic and infectious agents, from the body.

Now, a study by Brian Button and colleagues from the University of North Carolina at Chapel Hill, NC, helps to explain how human airways clear such mucus out of the lungs. The findings may give researchers a better understanding of what goes wrong in many human lung diseases, such as cystic fibrosis (CF), chronic obstructive pulmonary disease (COPD) and asthma.

The researchers' report appears in the journal Science, which is published by AAAS, the nonprofit science society.

"The air we breathe isn't exactly clean, and we take in many dangerous elements with every breath," explains Michael Rubinstein, a co-author of the Science report. "We need a mechanism to remove all the junk we breathe in, and the way it's done is with a very sticky gel called mucus that catches these particles and removes them with the help of tiny cilia."

"The cilia are constantly beating, even while we sleep," he says. "In a coordinated fashion, they push mucus containing foreign objects out of the lungs, and we either swallow it or spit it out. These cilia even beat for a few hours after we die. If they stopped, we'd be flooded with mucus that provides a fertile breeding ground for bacteria."

Until now, most researchers have subscribed to a "gel-on-liquid" model of mucus clearance, in which a watery "periciliary" layer acts as a lubricant and separates mucus from epithelial cells that line human airways. But this old explanation fails to explain how mucus remains in its own distinct layer.

"We can't have a watery layer separating sticky mucus from our cells because there is an osmotic pressure in the mucus that causes it to expand in water," Rubinstein says. "So what is really keeping the mucus from sticking to our cells?"

The researchers used a combination of imaging techniques to observe a dense meshwork in the periciliary layer of human bronchial epithelial cell cultures. The brush-like layer consists of protective molecules that keep sticky mucus from reaching the cilia and epithelial cells, thus ensuring the normal flow of mucus.

Based on their findings, Button and the other researchers propose a "gel-on-brush" form of mucus clearance in which mucus moves atop a brush-like periciliary layer instead of a watery one. They suggest that this mechanism captures the physics of human mucus clearance more accurately.

"This layer - this brush - seems to be very important for the healthy functioning of human airways," according to Rubinstein. "It protects cells from sticky mucus, and it creates a second barrier of defense in case viruses or bacteria penetrate through the mucus. They would not penetrate through the brush layer because the brush is denser."

"We found that there is a specific condition, below which the brush is healthy and cells are happy," Rubinstein explains. "But above this ideal condition, in diseases like CF or COPD, the brush becomes compressed and actually prevents the normal cilia beating and healthy flow of mucus."

The researchers explain that, whenever the mucus layer gets too dense, it can crash through the periciliary brush, collapse the cilia and stick to the cell surface.

"The collapse of this brush is what can lead to immobile mucus and result in infection, inflammation and eventually the destruction of lung tissue and the loss of lung function," says Rubinstein. "But our new model should guide researchers to develop novel therapies to treat lung diseases and provide them with biomarkers to track the effectiveness of those therapies."

Ivacaftor Improves Lung Function And Symptoms In Cystic Fibrosis Patients With Specific Genetic Mutation

Ivacaftor, a novel oral agent that potentiates a membrane channel blocked in patients aged six years and older with cystic fibrosis caused by the G551D mutation, significantly improves lung function and reduces pulmonary exacerbations, according to phase 3 data reported at the European Respiratory Society's Annual Congress 2012, Vienna, on Monday (3 September 2012). Open label follow-up showed the improved lung function and good tolerability was maintained with continued treatment.

The STRIVE study randomised 161 patients aged 12 and over with cystic fibrosis and at least one copy of the G551D mutation in the CFTR gene to ivacaftor (150mg every 12 hours) or placebo. Results showed a mean absolute improvement of 10.6% in predicted FEV₁ after 24 weeks' treatment with ivacaftor compared to placebo (p<0.0001), sustained at 10.5% at 48 weeks.

The ENVISION study, which included 52 children aged 6-11 years, showed similar absolute improvement of 12.5% in predicted FEV₁ with ivacaftor at 24 weeks compared to placebo (p<0.0001), with a 10.0% improvement maintained at 48 weeks.

STRIVE showed a significant reduction in pulmonary exacerbations and clinically significant improvement in the respiratory domain of patients' quality of life with ivacaftor. Both studies showed an increase in body weight (mean increases of 2.7kg at 48 weeks in STRIVE and 2.8kg in ENVISION).

"Ivacaftor is the first medicine to treat the underlying cause of cystic fibrosis in people with the G551D mutation, a defect in the cystic fibrosis transmembrane conductance regulator (CFTR) gene," said Stuart Elborn, Professor of Respiratory Medicine at Queen's University, Belfast, Northern Ireland and a principal investigator. "These data showing the consistent and sustained benefit of this medicine confirm that ivacaftor has the potential to make a significant difference to the lives of children, adolescents and adults with this form of CF."

He added: "The data don't capture the full benefit for patients. It's been very noticeable in the patients I look after that they are able to do things they previously couldn't after starting treatment with ivacaftor. They feel better and more able to plan for the future."

Fewer patients in the ivacaftor treatment groups discontinued treatment due to adverse events compared to placebo in both trials. Most adverse events associated with ivacaftor were mild to moderate, with some of the commonest including headache, upper respiratory tract infection, rash, diarrhea and abdominal pain.

Data reported from the follow-up PERSIST study showed that improvements in lung function with ivacaftor were sustained for patients continuing treatment from the STRIVE and ENVISION trials for up to 96 weeks. Those switched from placebo to open-label ivacaftor showed similar improvements in FEV1 to those seen in the patients starting on the drug during the placebo-controlled trials.

Reporting the findings, Dr Edward McKone, Consultant Respiratory Physician at St Vincent's University Hospital, Dublin, Ireland, said:

"We saw three main things: the efficacy with ivacaftor is sustained for up to 96 weeks; reproducible benefits for the placebo groups in the original trials; and, most importantly, the overall safety profile showed no new safety concerns."