Public release date: 11-Sep-2012 [ | E-mail | Share ]

Contact: Claire Gwayi-Chore cgwayi-chore@hematology.org 202-776-0544 American Society of Hematology

By including chemotherapy as a conditioning regimen prior to treatment, researchers have developed a refined gene therapy approach that safely and effectively restores the immune system of children with a form of severe combined immunodeficiency (SCID), according to a study published online today in Blood, the Journal of the American Society of Hematology (ASH).

SCID is a group of rare and debilitating genetic disorders that affect the normal development of the immune system in newborns. Infants with SCID are prone to serious, life-threatening infections within the first few months of life and require extensive treatment for survival beyond infancy.

Adenosine deaminase (ADA) deficiency, which accounts for approximately 15 percent of all SCID cases, develops when a gene mutation prohibits the production of ADA, an enzyme that breaks down toxic molecules that can accumulate to harmful levels and kill lymphocytes, the specialized white blood cells that help make up the immune system. In its absence, infants with ADA-deficient SCID lack almost all immune defenses and their condition is almost always fatal within two years if left untreated. Standard treatment for ADA-deficient SCID is a hematopoietic stem cell transplant (HSCT) from a sibling or related donor; however, finding a matched donor can be difficult and transplants can carry significant risks. An alternate treatment method, enzyme replacement therapy (ERT), involves regular injections of the ADA enzyme to maintain the immune system and can help restore immune function; however, the treatments are extremely expensive and painful for the young patients and the effects are often only temporary.

Given the limitations of HSCT and ERT, in the 1990s researchers began investigating the efficacy of gene therapy for ADA-deficient SCID. They discovered that they could "correct" the function of a mutated gene by adding a healthy copy into the cells of the body that help fight infectious diseases. Since then, there have been significant advances in gene therapy for SCID, yet successful gene therapy in patients with ADA-deficient SCID has been seen in only a small series of children due to the difficulty of introducing a healthy ADA gene into bone marrow stem cells and to engraft these cells back into the patients.

"Although the basic steps of gene therapy for patients with SCID have been known for a while, technical and clinical challenges still exist and we wanted to find an optimized gene therapy protocol to restore immunity for young children with ADA-deficient SCID," said Fabio Candotti, MD, one of the study's senior authors, senior investigator in the Genetics and Molecular Biology Branch of the National Human Genome Research Institute at the National Institutes of Health, and chair of the ASH Scientific Committee on Immunology and Host Defense.

To determine whether an enhanced gene therapy approach would improve immunity in children with ADA-deficient SCID, the teams of Dr. Candotti and Donald B. Kohn, MD, director of the Human Gene Medicine Program at the University of California, Los Angeles (UCLA), Professor of Pediatrics and of Microbiology, Immunology, and Molecular Genetics, and a member of the Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research at UCLA, conducted a clinical trial in 10 patients with the disorder. For the first time, Drs. Candotti and Kohn and their team of investigators compared two different retroviral vectors, MND-ADA and GCsapM-ADA, to transport normal ADA genes into the young patients' bone marrow stem cells as well as two different treatment plans in preparation for receiving gene therapy. Following therapy, investigators found that more bone marrow stem cells were marked with the MND-ADA vector, demonstrating its superiority over the GCsapM-ADA vector.

The investigators also sought to determine whether providing a low dose of chemotherapy prior to gene therapy, known as a pre-transplant conditioning regimen, would successfully deplete the young patients' bone marrow stem cells and make room for gene-corrected stem cells. In four patients, gene therapy was performed without chemotherapy, and the patients remained on ERT throughout the entire procedure to evaluate the efficiency of ERT combined with gene therapy. While these patients did not experience any adverse effects, they also did not experience a significant increase in their levels of the ADA enzyme. They also maintained low absolute lymphocyte counts (ALC) and minimal immune system function, leading the researchers to believe that ERT may weaken the therapy's effect by diluting the number of gene-corrected lymphocytes.

The remaining six patients were treated with the chemotherapy drug busulfan prior to gene therapy and ERT was discontinued prior to the gene therapy procedure. A significant increase in ADA was observed in all six patients; half of them remain off of ERT with partial immune reconstitution findings that support results from prior trials in Italy and the United Kingdom using chemotherapy prior to gene therapy and discontinuting ERT. While the ALC of all six patients declined sharply in the first few months due to combined effects of busulfan administration and ERT withdrawal, their counts increased from six to 24 months, even in the three patients that remained off of ERT. After adjusting the chemotherapy dosage, investigators were able to determine an optimal level for enhancing the efficacy of the gene-therapy-corrected cells with minimal toxicity.

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Researchers improve gene therapy technique for children with immune disorder

ScienceDaily (Sep. 11, 2012) By including chemotherapy as a conditioning regimen prior to treatment, researchers have developed a refined gene therapy approach that safely and effectively restores the immune system of children with a form of severe combined immunodeficiency (SCID), according to a study published online September 11 in Blood, the Journal of the American Society of Hematology (ASH).

SCID is a group of rare and debilitating genetic disorders that affect the normal development of the immune system in newborns. Infants with SCID are prone to serious, life-threatening infections within the first few months of life and require extensive treatment for survival beyond infancy.

Adenosine deaminase (ADA) deficiency, which accounts for approximately 15 percent of all SCID cases, develops when a gene mutation prohibits the production of ADA, an enzyme that breaks down toxic molecules that can accumulate to harmful levels and kill lymphocytes, the specialized white blood cells that help make up the immune system. In its absence, infants with ADA-deficient SCID lack almost all immune defenses and their condition is almost always fatal within two years if left untreated. Standard treatment for ADA-deficient SCID is a hematopoietic stem cell transplant (HSCT) from a sibling or related donor; however, finding a matched donor can be difficult and transplants can carry significant risks. An alternate treatment method, enzyme replacement therapy (ERT), involves regular injections of the ADA enzyme to maintain the immune system and can help restore immune function; however, the treatments are extremely expensive and painful for the young patients and the effects are often only temporary.

Given the limitations of HSCT and ERT, in the 1990s researchers began investigating the efficacy of gene therapy for ADA-deficient SCID. They discovered that they could "correct" the function of a mutated gene by adding a healthy copy into the cells of the body that help fight infectious diseases. Since then, there have been significant advances in gene therapy for SCID, yet successful gene therapy in patients with ADA-deficient SCID has been seen in only a small series of children due to the difficulty of introducing a healthy ADA gene into bone marrow stem cells and to engraft these cells back into the patients.

"Although the basic steps of gene therapy for patients with SCID have been known for a while, technical and clinical challenges still exist and we wanted to find an optimized gene therapy protocol to restore immunity for young children with ADA-deficient SCID," said Fabio Candotti, MD, one of the study's senior authors, senior investigator in the Genetics and Molecular Biology Branch of the National Human Genome Research Institute at the National Institutes of Health, and chair of the ASH Scientific Committee on Immunology and Host Defense.

To determine whether an enhanced gene therapy approach would improve immunity in children with ADA-deficient SCID, the teams of Dr. Candotti and Donald B. Kohn, MD, director of the Human Gene Medicine Program at the University of California, Los Angeles (UCLA), Professor of Pediatrics and of Microbiology, Immunology, and Molecular Genetics, and a member of the Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research at UCLA, conducted a clinical trial in 10 patients with the disorder. For the first time, Drs. Candotti and Kohn and their team of investigators compared two different retroviral vectors, MND-ADA and GCsapM-ADA, to transport normal ADA genes into the young patients' bone marrow stem cells as well as two different treatment plans in preparation for receiving gene therapy. Following therapy, investigators found that more bone marrow stem cells were marked with the MND-ADA vector, demonstrating its superiority over the GCsapM-ADA vector.

The investigators also sought to determine whether providing a low dose of chemotherapy prior to gene therapy, known as a pre-transplant conditioning regimen, would successfully deplete the young patients' bone marrow stem cells and make room for gene-corrected stem cells. In four patients, gene therapy was performed without chemotherapy, and the patients remained on ERT throughout the entire procedure to evaluate the efficiency of ERT combined with gene therapy. While these patients did not experience any adverse effects, they also did not experience a significant increase in their levels of the ADA enzyme. They also maintained low absolute lymphocyte counts (ALC) and minimal immune system function, leading the researchers to believe that ERT may weaken the therapy's effect by diluting the number of gene-corrected lymphocytes.

The remaining six patients were treated with the chemotherapy drug busulfan prior to gene therapy and ERT was discontinued prior to the gene therapy procedure. A significant increase in ADA was observed in all six patients; half of them remain off of ERT with partial immune reconstitution -- findings that support results from prior trials in Italy and the United Kingdom using chemotherapy prior to gene therapy and discontinuting ERT. While the ALC of all six patients declined sharply in the first few months due to combined effects of busulfan administration and ERT withdrawal, their counts increased from six to 24 months, even in the three patients that remained off of ERT. After adjusting the chemotherapy dosage, investigators were able to determine an optimal level for enhancing the efficacy of the gene-therapy-corrected cells with minimal toxicity.

This study is the first to detail comparisons of ADA-deficient SCID patient outcomes between those treated with gene therapy who have not received pre-transplant conditioning while continuing to receive ERT with those receiving pre-transplant conditioning without the administration of ERT. This study is also the first to compare two different viral vectors to transport normal ADA genes into patient bone marrow.

"We were very happy that in this trial we were able to see a benefit in the patients after we modified the protocol," said Dr. Kohn. "Doctors treating ADA-deficient SCID have had too few options for too long, and we hope this will provide them with an efficient and effective treatment for this devastating disease."

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Gene therapy technique for children with immune disorder improved

ScienceDaily (Sep. 11, 2012) UCLA stem cell researchers have found that a gene therapy regimen can safely restore immune systems to children with so-called "Bubble Boy" disease, a life threatening condition that if left untreated can be fatal within one to two years.

In the 11-year study, researchers were able to test two therapy regimens for 10 children with ADA-deficient severe combined immunodeficiency (SCID). During the study, they refined their approach to include a light dose of chemotherapy to help remove many of the blood stem cells in the bone marrow that are not creating an enzyme called adenosine deaminase (ADA), which is critical for the production and survival of healthy white blood cells, said study senior Dr. Donald Kohn, a professor of pediatrics and of microbiology, immunology, and molecular genetics in Life Sciences and a member of the Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research at UCLA.

The refined gene therapy and chemotherapy regimen proved superior to the other method tested in the study, restoring immune function to three of the six children who received it, Kohn said. Going forward, an even further refined regimen using a different type of virus delivery system will be studied in the next phase of the study, which already has enrolled eight of the 10 patients needed.

The study appears Aug. 30 in the advance online issue of the peer-reviewed journal Blood.

"We were very happy that in the human trials we were able to see a benefit in the patients after we modified the protocol," Kohn said. "Doctors treating ADA-deficient SCID have had too few options for too long, and we hope this will provide them with an efficient and effective treatment for this devastating disease."

Children born with SCID, an inherited immunodeficiency, are generally diagnosed at about six months. They are extremely vulnerable to infectious diseases and don't grow well. Chronic diarrhea, ear infections, recurrent pneumonia and profuse oral candidiasis commonly occur in these children. SCID cases occur in about 1 of 100,000 births

Currently, the only treatment for ADA-deficient SCID calls for injecting the patients twice a week with the necessary enzyme, Kohn said, a life-long process that is very expensive and often doesn't return the immune system to optimal levels. These patients also can undergo bone marrow transplants from matched siblings, but matches can be very rare.

About 15 percent of all SCID patients are ADA-deficient. Kohn and his team used a virus delivery system that he had developed in his lab in the 1990s to restore the gene that produces the missing enzyme necessary for a healthy immune system. To date, about 40 children with SCID have received gene therapy in clinical trials around the world, Kohn said.

Two slightly different viral vectors were tested in the study, each modified to deliver healthy ADA genes into the bone marrow cells of the patients so the needed enzyme could be produced and make up for the cells that don't have the gene. Four of the 10 patients in the study remained on their enzyme replacement therapy during the gene therapy study. There were no side effects, but their immune systems were not sufficiently restored, Kohn said.

In the next six patients, the enzyme therapy was stopped and a small dose of chemotherapy was given before starting the gene therapy to deplete the ADA-deficient stem cells in their bone marrow. Of those patients, half had their immune systems restored. The human findings confirmed another study, also published recently in Blood by Kohn and UCLA colleague Dr. Denise Carbonaro-Sarracino, which tested the techniques in parallel, using a mouse model of ADA-deficient SCID.

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Stem cell researchers use gene therapy to restore immune systems in 'Bubble Boy' disease

Public release date: 11-Sep-2012 [ | E-mail | Share ]

Contact: Claire Gwayi-Chore cgwayi-chore@hematology.org 202-776-0544 American Society of Hematology

By including chemotherapy as a conditioning regimen prior to treatment, researchers have developed a refined gene therapy approach that safely and effectively restores the immune system of children with a form of severe combined immunodeficiency (SCID), according to a study published online today in Blood, the Journal of the American Society of Hematology (ASH).

SCID is a group of rare and debilitating genetic disorders that affect the normal development of the immune system in newborns. Infants with SCID are prone to serious, life-threatening infections within the first few months of life and require extensive treatment for survival beyond infancy.

Adenosine deaminase (ADA) deficiency, which accounts for approximately 15 percent of all SCID cases, develops when a gene mutation prohibits the production of ADA, an enzyme that breaks down toxic molecules that can accumulate to harmful levels and kill lymphocytes, the specialized white blood cells that help make up the immune system. In its absence, infants with ADA-deficient SCID lack almost all immune defenses and their condition is almost always fatal within two years if left untreated. Standard treatment for ADA-deficient SCID is a hematopoietic stem cell transplant (HSCT) from a sibling or related donor; however, finding a matched donor can be difficult and transplants can carry significant risks. An alternate treatment method, enzyme replacement therapy (ERT), involves regular injections of the ADA enzyme to maintain the immune system and can help restore immune function; however, the treatments are extremely expensive and painful for the young patients and the effects are often only temporary.

Given the limitations of HSCT and ERT, in the 1990s researchers began investigating the efficacy of gene therapy for ADA-deficient SCID. They discovered that they could "correct" the function of a mutated gene by adding a healthy copy into the cells of the body that help fight infectious diseases. Since then, there have been significant advances in gene therapy for SCID, yet successful gene therapy in patients with ADA-deficient SCID has been seen in only a small series of children due to the difficulty of introducing a healthy ADA gene into bone marrow stem cells and to engraft these cells back into the patients.

"Although the basic steps of gene therapy for patients with SCID have been known for a while, technical and clinical challenges still exist and we wanted to find an optimized gene therapy protocol to restore immunity for young children with ADA-deficient SCID," said Fabio Candotti, MD, one of the study's senior authors, senior investigator in the Genetics and Molecular Biology Branch of the National Human Genome Research Institute at the National Institutes of Health, and chair of the ASH Scientific Committee on Immunology and Host Defense.

To determine whether an enhanced gene therapy approach would improve immunity in children with ADA-deficient SCID, the teams of Dr. Candotti and Donald B. Kohn, MD, director of the Human Gene Medicine Program at the University of California, Los Angeles (UCLA), Professor of Pediatrics and of Microbiology, Immunology, and Molecular Genetics, and a member of the Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research at UCLA, conducted a clinical trial in 10 patients with the disorder. For the first time, Drs. Candotti and Kohn and their team of investigators compared two different retroviral vectors, MND-ADA and GCsapM-ADA, to transport normal ADA genes into the young patients' bone marrow stem cells as well as two different treatment plans in preparation for receiving gene therapy. Following therapy, investigators found that more bone marrow stem cells were marked with the MND-ADA vector, demonstrating its superiority over the GCsapM-ADA vector.

The investigators also sought to determine whether providing a low dose of chemotherapy prior to gene therapy, known as a pre-transplant conditioning regimen, would successfully deplete the young patients' bone marrow stem cells and make room for gene-corrected stem cells. In four patients, gene therapy was performed without chemotherapy, and the patients remained on ERT throughout the entire procedure to evaluate the efficiency of ERT combined with gene therapy. While these patients did not experience any adverse effects, they also did not experience a significant increase in their levels of the ADA enzyme. They also maintained low absolute lymphocyte counts (ALC) and minimal immune system function, leading the researchers to believe that ERT may weaken the therapy's effect by diluting the number of gene-corrected lymphocytes.

The remaining six patients were treated with the chemotherapy drug busulfan prior to gene therapy and ERT was discontinued prior to the gene therapy procedure. A significant increase in ADA was observed in all six patients; half of them remain off of ERT with partial immune reconstitution findings that support results from prior trials in Italy and the United Kingdom using chemotherapy prior to gene therapy and discontinuting ERT. While the ALC of all six patients declined sharply in the first few months due to combined effects of busulfan administration and ERT withdrawal, their counts increased from six to 24 months, even in the three patients that remained off of ERT. After adjusting the chemotherapy dosage, investigators were able to determine an optimal level for enhancing the efficacy of the gene-therapy-corrected cells with minimal toxicity.

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Researchers improve gene therapy technique for children with immune disorder