Tag Archives: #genetherapy

Researchers Develop “Dimmer Switch” to Help Control Gene Therapy (Biology)

Delivery system fine tunes gene therapy expression levels and may pave the way for a new wave of gene therapies to treat rare and complex diseases

In a major advancement in the field of gene therapy for rare and devastating diseases, researchers at Children’s Hospital of Philadelphia (CHOP) have developed a “dimmer switch” system that can control levels of proteins expressed from gene therapy vectors. The system is based on alternative RNA splicing using an orally available small molecule and works effectively in tissues throughout the body, including the brain. The first research regarding this innovation was published today in the journal Nature.

Beverly Davidson, PhD
Beverly L. Davidson, PhD © CHOP

“We’re taking the field of gene therapy to an entirely new level where fine-tuned dosing is required for safety, utility and success,” said senior study author Beverly L. Davidson, PhD, Director of the Raymond G. Perelman Center for Cellular and Molecular Therapeutics and Chief Scientific Strategy Officer at Children’s Hospital of Philadelphia. “This study shows that by using a splicing modulator in combination with gene therapy tools, the dose of protein expressed from gene therapy vectors can be controlled for maximum therapeutic benefit.”

Many advancements in gene therapy have involved its delivery system, in the form of engineered viral vectors or lipid nanoparticles, but while improvements in these vehicles have delivered treatments to tissues more effectively, the cargo being delivered and elements controlling the resulting gene expression have not received the same amount of attention. Once gene therapy has been successfully delivered into the tissue, it is difficult to regulate the levels of expression. Too much expression may have toxic effects on the patient, and too little expression may mean that the patient does not receive the intended benefits of the therapy.

To address this problem, CHOP researchers developed a delivery system called the Xon system, which can finely control protein translation by using a “dimmer switch” to adjust the levels of expression up or down as needed. This method employs alternative RNA splicing, a process that allows a single gene to code for multiple proteins, depending on how the RNA is spliced. Using the Xon system, a gene therapy vector’s cargo is inactive until the oral drug is used, which then drives the splicing of the desired corrective gene into its active form.

“The newly developed switch not only controls protein levels, but if needed, those proteins can be induced again and again by the simple ingestion of an orally bioavailable drug,” said Alex Mas Monteys, PhD, a research assistant professor in Davidson’s lab at CHOP and co-lead author of the study.

In one example reported in this paper, the researchers used the Xon system in mice to adjust levels of erythropoietin (Epo), which is used to treat anemia associated with kidney disease. The researchers found that their delivery system induced hematocrit levels to 60 to 70% above baseline levels depending on the dose, and once levels slowly dropped to base levels, the system could be used again to safely re-induce the levels as would be needed for patients with chronic kidney disease. The research was conducted as part of a multi-year collaboration with scientists at the Novartis Institutes for BioMedical Research (NIBR). CHOP and NIBR are collaborating to develop next-generation small molecule splicing modulators and the Xon system to achieve fine-tuned gene regulation across multiple clinical applications. The team has also shown that the Xon system can be used to control expression of gene products that are toxic to the brain when expressed at high levels.

“The dose of a drug can determine how high you want expression to be, and then the system can automatically ‘dim down’ at a rate related to the half-life of the protein,” Davidson said. “We can envision scenarios where a drug would be given only once, such as for controlling the expression of foreign proteins needed for gene editing, or with limited frequency. Since the splicing modulators we have tested are given orally, compliance to control protein expression from viral vectors employing Xon-based cassettes should be high.”

Although the paper focuses on using Xon with gene therapy delivered via viral vectors, the researchers note it could also be engineered for use in cell engineering for CAR-T cell therapy. Here, the Xon system could be used to pause therapy if needed to give T-cells a rest.

The work was supported by NIBR, the Hereditary Disease Foundation and National Institutes of Health grant 5T32HG009495-04, the Children’s Hospital of Philadelphia Research Institute.

Dr. Davidson is an inventor of the Xon system. CHOP has licensed this technology to Novartis. CHOP, and by extension Dr. Davidson, have received compensation from Novartis in exchange for the licensing of the Xon technology. CHOP’s and Dr. Davidson’s participation in this research was reviewed and approved by CHOP’s Conflict of Interest Committee.

Reference: Monteys et al, “Regulated control of gene therapies by drug induced splicing.” Nature, online July 28, 2021. DOI: 10.1038/s41586-021-03770-2

Provided by CHOP

Scientists Discover Gene Therapy Which Provides Neuroprotection To Prevent Glaucoma Vision Loss (Medicine)

An NIH-funded research project found that calcium modulator CaMKII protects the optic nerve in mice, opening the door to new sight-saving therapy

A form of gene therapy protects optic nerve cells and preserves vision in mouse models of glaucoma, according to research supported by NIH’s National Eye Institute. The findings suggest a way forward for developing neuroprotective therapies for glaucoma, a leading cause of visual impairment and blindness. The report was published in Cell.

Glaucoma results from irreversible neurodegeneration of the optic nerve, the bundle of axons from retinal ganglion cells that transmits signals from the eye to the brain to produce vision. Available therapies slow vision loss by lowering elevated eye pressure, however some glaucoma progresses to blindness despite normal eye pressure. Neuroprotective therapies would be a leap forward, meeting the needs of patients who lack treatment options.

“Our study is the first to show that activating the CaMKII pathway helps protect retinal ganglion cells from a variety of injuries and in multiple glaucoma models,” said the study’s lead investigator, Bo Chen, Ph.D., associate professor of ophthalmology and neuroscience at the Icahn School of Medicine at Mount Sinai in New York City.

The CaMKII (calcium/calmodulin-dependent protein kinase II) pathway regulates key cellular processes and functions throughout the body, including retinal ganglion cells in the eye. Yet the precise role of CaMKII in retinal ganglion cell health is not well understood. Inhibition of CaMKII activity, for example, has been shown to be either protective or detrimental to retinal ganglion cells, depending on the conditions.

Using an antibody marker of CaMKII activity, Chen’s team discovered that CaMKII pathway signaling was compromised whenever retinal ganglion cells were exposed to toxins or trauma from a crush injury to the optic nerve, suggesting a correlation between CaMKII activity and retinal ganglion cell survival.

Searching for ways to intervene, they found that activating the CaMKII pathway with gene therapy proved protective to the retinal ganglion cells. Administering the gene therapy to mice just prior to the toxic insult (which initiates rapid damage to the cells), and just after optic nerve crush (which causes slower damage), increased CaMKII activity and robustly protected retinal ganglion cells.

Among gene therapy-treated mice, 77% of retinal ganglion cells survived 12 months after the toxic insult compared with 8% in control mice. Six months following optic nerve crush, 77% of retinal ganglion cells had survived versus 7% in controls.

Similarly, boosting CaMKII activity via gene therapy proved protective of retinal ganglion cells in glaucoma models based on elevated eye pressure or genetic deficiencies.

Increasing retinal ganglion cell survival rates translated into greater likelihood of preserved visual function, according to cell activity measured by electroretinogram and patterns of activity in the visual cortex.

Three vision-based behavioral tests also confirmed sustained visual function among the treated mice. In a visual water task, the mice were trained to swim toward a submerged platform on the basis of visual stimuli on a computer monitor. Depth perception was confirmed by a visual cliff test based on the mouse’s innate tendency to step to the shallow side of a cliff. Lastly, a looming test determined that treated mice were more apt to respond defensively (by hiding, freezing or tail rattling) when shown an overhead stimulus designed to simulate a threat, compared with untreated mice.

“If we make retinal ganglion cells more resistant and tolerant to the insults that cause cell death in glaucoma, they might be able to survive longer and maintain their function,” Chen concluded.

This study was supported by NEI grants R01EY028921, R01EY024986. NEI is part of the National Institutes of Health.

Featured image: Graphical abstract by authors


Guo X, Zhou J, Starr C, Mohns EJ, Li Y, Chen E, Yoon Y, Kellner CP, Tanaka K, Wang H, Liu W, LR, Demb JB, Crair MC, and Chen B. “Preservation of vision after CaMKII-mediated protection of retinal ganglion cells.” Published online July 22, 2021 in Cell. DOI: https://doi.org/10.1016/j.cell.2021.06.031

Provided by NIH/NEI

NIH-funded Study Finds Gene Therapy May Restore Missing Enzyme in Rare Disease (Medicine)

Results provide hope for children with aromatic L-amino acid decarboxylase deficiency

A new study published in Nature Communications suggests that gene therapy delivered into the brain may be safe and effective in treating aromatic L-amino acid decarboxylase (AADC) deficiency. AADC deficiency is a rare neurological disorder that develops in infancy and leads to near absent levels of certain brain chemicals, serotonin and dopamine, that are critical for movement, behavior, and sleep. Children with the disorder have severe developmental, mood dysfunction including irritability, and motor disabilities including problems with talking and walking as well as sleep disturbances. Worldwide there have been approximately 135 cases of this disease reported.

In the study, led by Krystof Bankiewicz, M.D., Ph.D., professor of neurological surgery at Ohio State College of Medicine in Columbus, and his colleagues, seven children received infusions of the DDC gene that was packaged in an adenovirus for delivery into brain cells. The DDC gene is incorporated into the cells’ DNA and provides instructions for the cell to make AADC, the enzyme that is necessary to produce serotonin and dopamine. The research team used magnetic resonance imaging to guide the accurate placement of the gene therapy into two specific areas of the midbrain.

Positron emission tomography (PET) scans performed three and 24 months after the surgery revealed that the gene therapy led to the production of dopamine in the deep brain structures involved in motor control. In addition, levels of a dopamine metabolite significantly increased in the spinal fluid.

The therapy resulted in clinical improvement of symptoms. Oculogyric crises, abnormal upward movements of the eyeballs, often with involuntary movements of the head, neck and body, that can last for hours and are a hallmark of the disease, completely went away in 6 of 7 participants. In some of the children, improvement was seen as early as nine days after treatment. One participant continued to experience oculogyric crises, but they were less frequent and severe.

All of the children exhibited improvements in movement and motor function. Following the surgery, parents of a majority of participants reported their children were sleeping better and mood disturbances, including irritability, had improved. Progress was also observed in feeding behavior, the ability to sit independently, and in speaking. Two of the children were able to walk with support within 18 months after receiving the gene therapy.

The gene therapy was well tolerated by all participants and no adverse side effects were reported. At three to four weeks following surgery, all participants exhibited irritability, sleep problems, and involuntary movements, but those effects were temporary. One of the children died unexpectedly seven months after the surgery. The cause of death was unknown but assessed to be due to the underlying primary disease.

This study was supported by NINDS (R01NS094292, NS073514-01).

Featured image: MR-guided delivery of AAV2-hAADC into the midbrain, baseline DaTscan and changes in FDOPA PET biomarker after gene delivery. © Authors

Article: Pearson, T.S., Gupta, N., San Sebastian, W. et al. Gene therapy for aromatic L-amino acid decarboxylase deficiency by MR-guided direct delivery of AAV2-AADC to midbrain dopaminergic neurons. Nat Commun 12, 4251 (2021). https://doi.org/10.1038/s41467-021-24524-8

Provided by NINDS

Gene Therapy Shows Promise in Initial Trial for Patients with Childhood Blindness (Medicine)

Penn Medicine researchers delivered working copies of the gene GUCY2D to the eyes of patients with severe vision impairments

 A new gene therapy for one of the most common forms of congenital blindness was safe and improved patients’ vision, according to initial data from a clinical trial led by researchers at the Scheie Eye Institute in the Perelman School of Medicine at the University of Pennsylvania.

The therapy delivers working copies of GUCY2D to the eyes of patients who have severe vision impairments caused by mutations in the gene. Each of the first three treated patients experienced improvement in some aspects of vision, without serious side effects, according to the new study, published in the journal iScience.

“We found sustained improvements in both day and night vision, even with a relatively low dose of the gene therapy,” said study lead author Samuel G. Jacobson, MD, PhD, a professor of Ophthalmology in the Perelman School of Medicine.

Artur V. Cideciyan, PhD, and Samuel G. Jacobson, MD, PhD © Penn Medicine

The GUCY2D gene is one of about 25 different human genes whose mutations cause problems in the retina, leading to severe vision impairment from birth or early childhood. This family of inherited retinal disorders, collectively known as Leber congenital amaurosis (LCA), accounts for a considerable portion of blindness in children worldwide.

Normal copies of GUCY2D encode an enzyme in the key pathway that light-sensitive rod and cone cells in the retina use to convert light into electrochemical signals. A lack of this enzyme blocks the recovery of this pathway, preventing the reset needed for further signaling. As a result, the signal from rod and cone cells becomes very weak — which equates to severe vision loss.

Even in adults who have lived for decades with this condition, it is often the case that many light-sensing retinal cells remain alive and intact despite their dysfunction. Thus, adding functional copies of GUCY2D via a gene therapy could get those cells working again and restore some vision.

Childhood visual loss in Leber congenital amaurosis due to GUCY2D mutations affects both night vision and clarity, but the eyes’ photoreceptors remain relatively intact. An injection of gene therapy led to improved night (rod) and day (cone) vision. Credit: Alexander Sumaroka and Alexandra V. Garafalo

In 2019, Jacobson and co-investigator Artur V. Cideciyan, PhD, a research professor of Ophthalmology in the Perelman School of Medicine, began the first clinical trial of a GUCY2D gene therapy, a solution of a harmless virus that carries the gene and is injected beneath the retina — initially in just one eye per patient. They are following each patient for two years after treatment. In the new report, they described their findings after nine months in the first three patients treated.

The first patient experienced a substantial increase in light-sensitivity in rod cells, which are more light-sensitive than cone cells and are chiefly responsible for low-light or “night vision.” This patient also showed improved pupil responses to light.

The second patient showed a smaller but sustained increase in light-sensitivity in rod cells, starting about two months after the gene therapy.

The third patient showed no improvement in rod cell sensitivity, but did show significantly improved visual acuity over the nine-month follow-up period, an improvement that the researchers tied to better function in the patient’s cone cells, the predominant cells for daylight and color vision.

“These initial results from the first-ever trial of a GUCY2D gene therapy are very encouraging and will inform our ongoing and future trials of this therapy,” said Cideciyan.

There were no serious adverse side effects, and any side effects that occurred in the patients’ retinas resolved.

The gene therapy dose used in these first three patients was the lowest of the doses the researchers plan to use in the study, so they are hoping to see continued safety and greater efficacy in later-enrolled patients who will receive higher doses.

The ongoing clinical trial is registered at clinicaltrials.gov as trial NCT03920007.

Jacobson and Cideciyan in earlier studies have reported success for gene-based therapies against two other forms of Leber congenital amaurosis involving other genes.

Additional Penn authors included: Alexandra V. Garafalo, Alejandro J. Roman, Alexander Sumaroka, Vivian Wu, Arun K. Krishnan, and Rebecca Sheplock.

Support for the research was provided by Atsena Therapeutics Inc.

Reference: Samuel G. Jacobson, Artur V. Cideciyan et al., “Safety and Improved Efficacy Signals following Gene Therapy in Childhood Blindness Caused by GUCY2D Mutations”, iscience, 2021. DOI: https://doi.org/10.1016/j.isci.2021.102409

Provided by Penn Medicine

Gene Therapy Shows Promise in Treating Rare Eye Disease in Mice (Medicine)

Findings suggest combination gene therapies that target multiple causes of eye cell death in mice could be an effective approach for treating people with retinitis pigmentosa and similar conditions.

A gene therapy protects eye cells in mice with a rare disorder that causes vision loss, especially when used in combination with other gene therapies, shows a study published today in eLife.

The findings suggest that this therapy, whether used alone or in combination with other gene therapies that boost eye health, may offer a new approach to preserving vision in people with retinitis pigmentosa or other conditions that cause vision loss.

Retinitis pigmentosa is a slowly progressive disease, which begins with the loss of night vision due to genetic lesions that affect rod photoreceptors – cells in the eyes that sense light when it is low. These photoreceptors die because of their intrinsic genetic defects. This then impacts cone photoreceptors, the eye cells that detect light during the day, which leads to the eventual loss of daylight vision. One theory about why cones die concerns the loss of nutrient supply, especially glucose.

Scientists have developed a few targeted gene therapies to help individuals with certain mutations that affect the photoreceptors, but no treatments are currently available that would be effective for a broad set of families with the disease. “A gene therapy that would preserve photoreceptors in people with retinitis pigmentosa regardless of their specific genetic mutation would help many more patients,” says lead author Yunlu Xue, Postdoctoral Fellow at senior author Constance Cepko’s lab, Harvard Medical School, Boston, US.

To find a widely effective gene therapy for the disease, Xue and colleagues screened 20 potential therapies in mouse models with the same genetic deficits as humans with retinitis pigmentosa. The team chose the therapies based on the effects they have on sugar metabolism.

Their experiments showed that using a virus carrier to deliver a gene called Txnip was the most effective approach in treating the condition across three different mouse models. A version of Txnip called C247S worked especially well, as it helped the cone photoreceptors switch to using alternative energy sources and improved mitochondria health in the cells.

The team then showed that giving the mice gene therapies that reduced oxidative stress and inflammation, along with Txnip gene therapy, provided additional protection for the cells. Further studies are now needed to confirm whether this approach would help preserve vision in people with retinitis pigmentosa.

“The immediate next step is to test Txnip for safety in animals beyond mice, before moving on to a clinical trial in humans,” explains senior author and Howard Hughes Institute Investigator Constance Cepko, the Bullard Professor of Genetics and Neuroscience at Harvard Medical School. “If it ultimately proves safe in people, then we would hope to see it become an effective approach for treating those with retinitis pigmentosa and other forms of progressive vision loss, such as age-related macular degeneration.”

Featured image: High magnification images taken with an electron microscope, focusing on mitochondria (shown in magenta) in a degenerating retinal cone photoreceptor. The image on the right shows a single mitochondrion following treatment with Txnip, which has a healthier appearance compared to mitochondria before treatment, on the left. Image credit: Yunlu Xue (CC BY 4.0)

Reference: Yunlu Xue et al., “AAV-Txnip prolongs cone survival and vision in mouse models of retinitis pigmentosa”, elife, 2021. DOI: 10.7554/eLife.66240

Provided by Elife

Mayo Researchers Reveal Gene Therapy Path For Treating Children with Rare, Fatal Genetic Disease (Medicine)

A gene therapy strategy developed by Mayo Clinic researchers could offer a potential treatment for a rare and fatal genetic disease that often sickens babies in their first days of life. The disease, propionic acidemia, occurs in 1 in 100,000 live births in the U.S. There is no cure.

“As soon as the babies start eating, they quickly get sick,” says Michael Barry, Ph.D., a gene therapy expert within Mayo Clinic’s Division of Infectious Diseases. “They can start vomiting, become lethargic and have seizures. They have metabolic acidosis (electrolyte disorder) and particularly hyperammonemia (excess of ammonia in the blood), which is very dangerous. And if they are not treated, they can die.”

Dr. Barry and his team with Mayo Clinic’s Center for Individualized Medicine have developed a technique to replace the defective genes that cause the disease. Dr. Barry will present his gene therapy strategy at the upcoming Undiagnosed Disease Network International and Mayo Clinic Science Session April 9–11. 

Propionic acidemia is caused by an inherited mutation in the PCCA or PCCB genes, which provide instructions for making the enzyme propionyl-CoA carboxylase. This critical enzyme, which is used by many cells in the body, plays a role in breaking down amino acids, as well as certain lipids, or fats, and cholesterol. A deficiency in this enzyme leads to a buildup of toxic chemicals.

In most cases, patients are given a special protein-restricted diet that can limit life-threatening episodes, but this is difficult and does not cure the disease. Current treatment options are limited and do not provide the quality of life or long-lasting benefits that patients and their families are seeking. In some cases, a liver transplant is a potential treatment, but this has its own risks.

“Our approach is to give these patients a good copy of the gene to counteract the disease as best we can,” explains Dr. Barry, who has devoted 15 years to studying propionic acidemia. “This restores the ability of cells in the body to process these food components and reduce the production of toxic chemicals.”

Special delivery packaged in an unusual source

Adeno-associated virus © Mayo Clinic

Following years of genetic research, the Mayo team is studying gene therapy as a technique to treat diseases caused by defective genes. Genes contain DNA — the code that controls the body’s form and function. Gene therapy replaces the faulty genes or adds a new gene in an attempt to treat a disease, thereby avoiding surgery or long-term medication use for treatment.

The key to Dr. Barry’s gene therapy approach is an adeno-associated virus (AAV), which is known for infecting people without causing disease. These viruses are experts at penetrating cell walls and shuttling the PCCArepair gene to the cell’s nucleus, where it is expressed to provide the missing functions.

“AAV is very good at taking its own DNA and putting it into a cell, so we’re basically removing almost all of the viral genes and then replacing them with the repair gene to try to treat the disease,” explains Dr. Barry.

Overall, the virus plays the essential role of targeting the correct cells and safely delivering the therapeutic genetic material into them.

The expectation is that the corrected genes will be expressed within the patient’s cells, and the affected cells will begin producing the correct protein to fight off the disease. This kind of gene therapy can be given to a patient once, and it is hoped to give years of long-lasting benefit.

Combating disease through gene therapy

The researchers demonstrated that this type of gene therapy can protect animals with propionic acidemia and allow them to eat a protein-rich food and develop normally. Based on this, the team hopes to begin a human clinical trial at Mayo Clinic within the next year or two.

“Our approach is to give these patients a good copy of the gene to counteract the disease as best we can. This restores the ability of cells in the body to process these food components and reduce the production of toxic chemicals.”

– Dr. Barry

Helping to facilitate the approach and move the gene therapy project forward to the clinic is David Deyle, M.D., a Mayo Clinic clinical genomicist. 

“There is still work to be done in order to do all of the testing needed to bring this promising treatment to patients, but we are encouraged by results and have begun the process toward a clinical trial,” Dr. Deyle says.

Dr. Deyle says the gene therapy technique holds the potential for treating a wide range of genetic disorders, such as cancer, vision loss, inborn errors of metabolism, blood disorders, immune disorders and neuromuscular disorders. 

Mayo Clinic’s gene therapy for propionic acidemia has been granted Food and Drug Administration (FDA) Orphan Drug and Rare Pediatric Disease designations. These designations are intended to stimulate development of treatments for rare diseases that affect children by giving drug makers accelerated FDA review.

Testing for propionic acidemia is already a part of standard newborn screening. If the gene therapy strategy is proven to be safe and effective in humans, it would provide the ability to treat patients early, enabling an improved quality of life.

Provided by Mayo Clinic

Gene Therapy Using “Zinc Fingers” May Help Treat Alzheimer’s Disease, Animal Study Shows (Neuroscience)

Key Takeaways

  • A single injection of a gene therapy involving what are called zinc fingers dramatically reduced levels of tau, a protein implicated in Alzheimer’s disease, in mice with the condition.
  • The treatment was long lasting, caused no side effects, and reduced Alzheimer’s-related damage in the brain.

“The technology worked just the way we had hoped—reducing tau substantially for as long as we looked.”

— Bradley Hyman, MD, PhD, Director of Alzheimer’s Research Unit, Institute for Neurodegenerative Disease, Mass General Hospital

Researchers have used a genetic engineering strategy to dramatically reduce levels of tau—a key protein that accumulates and becomes tangled in the brain during the development of Alzheimer’s disease—in an animal model of the condition. The results, which come from investigators at Massachusetts General Hospital (MGH) and Sangamo Therapeutics Inc., could lead to a potentially promising treatment for patients with this devastating illness.

As described in Science Advances, the strategy involves a gene regulation technology called zinc finger protein transcription factors (ZFP-TFs), which are DNA-binding proteins that can be harnessed to target and affect the expression of specified genes. In this case, the therapy was designed to target and silence the expression of the gene that codes for tau. Mice with Alzheimer’s disease received a single injection of the treatment—which employed a harmless virus to deliver the ZFP-TFs to cells—directly into the hippocampus region of the brain or intravenously into a blood vessel. Treatment with ZFP-TFs reduced tau protein levels in the brain by 50% to 80% out to 11 months, the longest time point studied. Importantly, the therapy reversed some of the Alzheimer’s-related damage that was present in the animals’ brain cells.

“The technology worked just the way we had hoped—reducing tau substantially for as long as we looked, causing no side effects that we could see even over many, many months, and improving the pathological changes in the brains of the animals,” says senior author Bradley Hyman, MD, PhD, who directs the Alzheimer’s disease research unit at the MassGeneral Institute for Neurodegenerative Disease. “This suggests a plan forward to try to help patients.”

The simplicity of the therapy makes it an especially attractive approach. “This was the result of a single treatment of gene regulation therapy, which could be given by an injection into the bloodstream,” says Hyman. “While this therapy is far from patients—as much more development and safety testing would need to be done—it is a promising and exciting first step.”

The study was primarily supported by Sangamo, pursuant to a sponsored research agreement with MGH. Funding was also provided by MGH and the German Center for Neurodegenerative Diseases (DZNE) of the Helmholtz Foundation, the JPB Foundation, the National Institute on Aging, and the BrightFocus Foundation.

Featured image: Tau-targeted ZFP-TFs reduce mouse tau mRNA and protein expression in vitro. (A) Principle of ZFP-TF target DNA sequence recognition. Engineered arrays of ZFPs recognizing specific DNA triplets bind a specific genomic DNA sequence. Fusion to a TF enables repression of target gene transcription. © Wegmann et al.

Reference: Susanne Wegmann, Sarah L. DeVos, Bryan Zeitler, “Persistent repression of tau in the brain using engineered zinc finger protein transcription factors”, Science Advances  19 Mar 2021: Vol. 7, no. 12, eabe1611 DOI: 10.1126/sciadv.abe1611

Provided by Massachusetts General Hospital

About the Massachusetts General Hospital

Massachusetts General Hospital, founded in 1811, is the original and largest teaching hospital of Harvard Medical School. The Mass General Research Institute conducts the largest hospital-based research program in the nation, with annual research operations of more than $1 billion and comprises more than 9,500 researchers working across more than 30 institutes, centers and departments. In August 2020, Mass General was named #6 in the U.S. News & World Report list of “America’s Best Hospitals.”

A Canadian Success Story: World-first to Treat Fabry Disease With Gene Therapy (Medicine)

Results of a world-first Canadian pilot study on patients treated with gene therapy for Fabry disease show that the treatment is working and safe.

The Canadian research team was the first to use gene therapy in 2017 to treat patients with Fabry disease, a rare, chronic illness that can damage major organs and shorten lives. They report their findings on February 25 in the journal Nature Communications.

“Being one of the first people in the world to receive this treatment, and seeing how much better I felt afterward, it definitely gives me hope that this can help many other Fabry patients and potentially those with other single gene mutation disorders,” says Ryan Deveau, one of the participating patients in Dartmouth, Nova Scotia.

“Now that I don’t have to get the replacement therapy every two weeks, I have more time to spend with my family.”

Fabry patients currently must undergo enzyme therapy infusions every two weeks. Gene therapy would enable them to receive a single treatment that could prove to be more effective clinically since the modified blood stem cells continuously produce corrected versions of the defective enzyme.

“To date, we can say that the gene therapy has either partially or fully restored enzyme levels to a point where they are no longer considered deficient,” says Dr. Aneal Khan, the Alberta Health Services medical geneticist and member of the Alberta Children’s Hospital Research Institute, Cumming School of Medicine, University of Calgary, who is leading the experimental trial in Calgary.

“These results show that just one treatment of gene therapy was enough to benefit patients. Now we need to see whether this single dose can last for the long term.”

Dr. Aneal Khan, the Alberta Health Services medical geneticist, is leading the gene therapy study in Calgary. (Photo: Alberta Health Services)

Five men participated in the study and were treated at Alberta Health Services’ Foothills Medical Centre in Calgary, the Princess Margaret Cancer Centre in Toronto and Nova Scotia Health’s Queen Elizabeth II Health Sciences Centre in Halifax.

As a result of the gene therapy, all patients began producing the corrected version of the enzyme to near normal levels within one week. With these initial results, all five patients are approved by Health Canada to stop their intravenous enzyme therapy. So far, three patients have chosen to do so, and are stable.

“This really was a ground-breaking study, given current therapies are not cures,” says Dr. Michael West, nephrologist and Nova Scotia Health co-investigator, with Dr. Stephen Couban, a hematologist. “This is the next step in moving toward a better therapy and hopefully a cure for this disease, which can really cause patients a lot of pain and suffering.

“It’s promising that the participating patients are still seeing benefit from the treatment several years after the procedure was completed.”

Patients were followed from January 2017 to February 2020 for this study, and ongoing follow-up will extend until February 2024.

Clinicians emphasize it will take many years of further testing before this experimental treatment becomes a clinically available standard of care.

“To actually see that this therapy was working in patients was humbling,” says Dr. Jeffrey Medin, who pioneered the treatment while he was a Senior Scientist at the Princess Margaret. Dr. Medin is now the MACC Fund Professor at the Medical College of Wisconsin and Affiliate Scientist, UHN.

“After 20 years of working on this treatment, to see that patients could end up making their own enzyme, and that the treatment effect was sustained is satisfying. We are elated!”

Dr. Michael West, Nova Scotia Health co-investigator of the gene therapy study in Halifax. (Photo: Nova Scotia Health)

Darren Bidulka, 52, was the first patient treated in the study on January 11, 2017, at Alberta Health Services’ Foothills Medical Centre. He was diagnosed with Fabry disease in 2005, and was on enzyme therapy for years.

“I’m really happy that this worked,” he says. “What an amazing result in an utterly fascinating experience. I consider this a great success.

“I can lead a more normal life now without scheduling enzyme therapy every two weeks. This research is also incredibly important for many patients all over the world, who will benefit from these findings.”

In the study, researchers collected a quantity of a Fabry patient’s own blood stem cells, then used a specially engineered virus to inject those cells with copies of the fully functional gene that is responsible for the enzyme. The modified stem cells were then transplanted back into each patient.

People with Fabry disease have a gene called GLA that does not function correctly. As a result, their bodies are unable to make the correct version of an enzyme that breaks down a fat. A buildup of that can lead to problems in the kidneys, heart and brain.

The treatment, which was approved by Health Canada for experimental purposes, was the first trial in Canada to use a lentivirus in gene therapy. In this case, the specially modified virus was created at the Princess Margaret, stripped of its disease-causing capability and augmented with a working copy of the gene that’s responsible for the missing enzyme.

Darren Bidulka, 52, was the first patient treated by gene therapy in the study on January 11, 2017. He remains off enzyme therapy. (Photo: Courtesy Darren Bidulka)

Lentiviruses are a family of viruses that can cause diseases like acquired immunodeficiency syndrome (AIDS), and are used world-wide in many clinical trials because of the ease with which they can enter and insert genetic material into cells. They are well understood by the research community, and easy to manufacture in large quantities, which was required for this study.

The trial focused on men because the gene for Fabry disease is on the X-chromosome, so it is inherited as an X-linked disorder. Men are therefore more severely affected than women, because each man carries only one X chromosome.

Men therefore present with more severe symptoms, such as burning in hands and feet, kidney failure, or gastrointestinal symptoms such as abdominal cramping, frequent bowel movements, diarrhea, nausea or vomiting.  Untreated, men have an average lifespan of 58 years and women, 75 years.

An estimated one person in 40,000 to 60,000 has Fabry disease. There are more than 500 people in Canada known to have this illness, although exact numbers are not known due to the difficulty in identifying all those with the disease.

“Studies such as this can pave the way for additional clinical trials in Fabry disease and for many other metabolic disorders. It also shows that it is possible to coordinate such a complex study at multiple sites, even across international borders, as some analyses were done at the Medical College of Wisconsin,” says Dr. Medin, who has been working on the project since he was at the National Institutes of Health in Bethesda, MD.

Darren and team: Darren Bidulka rests after his modified blood stem cells were transplanted into him at the Foothills Medical Centre in Calgary in 2017, allowing him to stop his enzyme therapy. (L to R) Dr. Jeffrey Medin, Medical College of Wisconsin, Dr. Aneal Khan, the experimental trial lead in Calgary, and Darren Bidulka. (Photo: Courtesy Darren Bidulka)

Competing Interests

UHN has a financial interest in a licensing agreement with AVROBIO, Inc., granting AVROBIO exclusive rights to manufacture and commercialize the gene therapy studied in this Phase 1 clinical trial.

Aneal Khan: AVROBIO: consulting fees, grants, revenue distribution agreement, speaker fees and travel support; University Health Network: revenue distribution agreement.

Anthony Rupar: AVROBIO: service contract.

Christiane Auray-Blais: AVROBIO: honoraria and service contract.

Armand Keating: AVROBIO: consulting fees unrelated to this study.

Michael L. West: Amicus Therapeutics: consulting fees, grants, speaker fees and travel support;

Protalix: consulting fees, grants, speaker fees and travel support; Sanofi-Genzyme: consulting fees, grants, speaker fees and travel support; Takeda Pharmaceuticals: consulting fees, grants, speaker fees and travel support; and University Health Network: revenue distribution agreement.

Jeffrey A. Medin: AVROBIO: scientific co-founder and shareholder; Rapa Therapeutics: scientific advisory board; Sanofi-Genzyme: honorarium, Shire: honorarium.

Support for this study provided by: Canadian Institutes of Health Research (CIHR), the Kidney Foundation of Canada and the MACC Fund, and AVROBIO, Inc. Juravinski Hospital, London Health Sciences Centre and Université de Sherbrooke provided critical laboratory support in stem and progenitor cell isolation, assay of enzymatic activity and metabolite levels, respectively.

Featured image: Dr. Jeffrey Medin, Affiliate Scientist at UHN, and MACC Fund Professor at the Medical College of Wisconsin, pioneered the Fabry gene therapy treatment while a Senior Scientist at Princess Margaret Cancer Centre. (Photo: Medical College of Wisconsin)

Reference: Khan, A., Barber, D.L., Huang, J. et al. Lentivirus-mediated gene therapy for Fabry disease. Nat Commun 12, 1178 (2021). https://www.nature.com/articles/s41467-021-21371-5 https://doi.org/10.1038/s41467-021-21371-5

Provided by UHN

Improved Vectors for Ocular Gene Therapy (Medicine)

Gene therapies to mitigate the effects of mutations that cause blindness are undergoing rapid development. Novel gene vectors reduce the risks associated with these procedures.

The incidence of genetic mutations that result in rapid deterioration of the ability to see is larger than is generally supposed. For example, on the order of five million people around the world suffer from congenital retinal dystrophies, which often lead to blindness at an early age. These diseases are caused by defects in specific genes, which direct the production of proteins that play an essential role in the visual process. Many of these errors alter only a single element of the blueprint, but they can nevertheless lead to loss of function of the photoreceptors or the cells that form the retinal pigmented epithelium. Approximately 150 such defects have been identified. Up until quite recently, there was no way to treat these conditions. However, thanks to the development of dedicated gene-delivery vehicles based on harmless viruses, this picture has begun to change. These ‘vectors’ can be used to transport functional copies of the relevant gene into the retinal cells. Since these intact copies can direct the synthesis of a functional version of the defective protein, they should be able to supplement the missing function, at least in part. In the case of one specific form of retinal dystrophy, this approach is already in clinical use.

Stylianos Michalakis (Professor of the Gene Therapy of Ocular Diseases at the Department of Ophthalmology at LMU Medical Center) has been working on the design of gene vectors for this purpose over the past several years. These efforts have focused on vectors that are based on the genomes of adeno-associated viruses (AAVs). In collaboration with Hildegard Büning (Professor of the Infection Biology of Gene Transfer at Hannover Medical School (MHH)) and an international team of researchers, Michalakis has now succeeded in constructing vectors that can be more easily and effectively introduced into retinal cells. Up to now, it was necessary to inject the viral vectors directly under the retina. This is a technique that requires highly skilled experts and facilities that are available only at specialized hospitals, and there is always a risk of damage to the fragile retinal tissue itself. Another drawback of this method is that each injection reaches only a relatively small fraction of the target cells.

Using animal models, as well as human retinal cells cultured in the laboratory, Michalakis and colleagues injected their AAV constructs directly into the jelly-like material that fills the eyeball. Known as the ‘vitreous humor’, this substance directly overlies the retina at the back of the eye. These experiments confirmed that the novel vectors could be transported into the light-sensitive photoreceptors in the retinal tissue. This delivery method entails less risk than those employed hitherto. Indeed, the technique is already used in clinical practice for the treatment of macular degeneration. – “And it can be performed by any ophthalmologist,” Michalakis adds.

Some degrees of daylight vision

Further studies on three animal models confirmed the efficacy of the procedure, and experiments on human retinal tissue grown in culture confirmed that the vectors can infect photoreceptors and other retinal cells. Finally, initial results of experiments on a mouse model of achromatopsia (complete lack of color vision) suggested that the procedure is capable of restoring some degree of daylight vision.

The study was designed in cooperation with Hildegard Büning at the MHH, with substantial contributions from colleagues based at Michigan State University (Professor Simon Petersen-Jones), the Ophthalmology Clinic at the LMU Medical Center (Professor Siegfried Priglinger) and the Department of Pharmacy at LMU (Professor Martin Biel).

Featured image: Patients with achromatopsia are completely color blind. The cause of the disease is a gene defect.sion is blurred | © S. Michalakis

Reference: Marina Pavlou et al., “Novel AAV capsids for intravitreal gene therapy of photoreceptor disorders”, EMBO Mol Med (2021) e13392. https://doi.org/10.15252/emmm.202013392 EMBO Molecular Medicine, 2021

Provided by LMU Munich