In this issue:
- Welcome from Scott Baker, MD, Program Director
- Survival and Late Effects after Transplant for Aplastic Anemia
- Ground-breaking Study: Lentiviral Vector-based Gene Therapy for Fanconi Anemia
- Editor’s Guide to Correcting Faulty Genes
Transplantation and gene therapy for aplastic anemia
Since the first successful bone marrow transplants of the 1970s, much has been learned about the elements of care required for long-term effectiveness and safety. Today, we have transplant protocols suited for pediatric patients with all types of blood disorders and varying degrees of donor match. We have new treatments to boost survival and quality of life. And, based on three decades of research on some truly inspirational patients, we have a storehouse of evidence to guide the next decade of pediatric transplantation.
In this issue of Pediatric BMT Update, we answer the question of how well transplantation has worked for children with aplastic anemia and we explore new forms of transplantation and gene therapy for children with Fanconi anemia.
Long-term outcomes in aplastic anemia
All of you I am sure are familiar with Dr. Jean Sanders—she is a pioneer in the field of pediatric transplantation and particularly in her research on survivorship issues in our long term survivors after transplantation. She has made tremendous contributions to the field and I am honored to follow her as director of the Pediatric Blood and Marrow Transplant program at Seattle Cancer Care Alliance.
Our first story highlights results from Dr. Sanders’ just-published paper on long-term outcomes in children transplanted for aplastic anemia. This is the largest and longest-term pediatric experience ever published for aplastic anemia. The new publication is our best road map for guiding families of children with this disease.
New treatments, including gene therapy, for Fanconi anemia
A child with Fanconi anemia (FA) requires comprehensive care to handle their complex multispecialty needs. Transplantation calls for special techniques to overcome hypersensitivity to conditioning therapies and a susceptibility to post-transplant cancer.
The other story in this issue describes efforts underway at the FA Center at Seattle Children’s to improve transplant outcomes in these patients. The story also announces our newly opened gene therapy trial—the world’s first-ever clinical trial of lentivirus vector-based gene therapy for patients with FA.
Looking ahead… and looking back to tackle rare diseases
Aplastic anemia is a rare disease. But here at SCCA, we specialize in treating exactly these types of seriously ill patients. In fact, we have done nearly 400 pediatric transplants in children with rare nonmalignant conditions such as aplastic anemia, sickle cell disease, or immunodeficiencies. And we have done more unrelated donor transplants for patients with severe aplastic anemia than any other transplant center in the U.S. [NMDP 2011 data; www.marrow.org]
Here in Seattle, we are always looking ahead to find new treatments—such as gene therapy—for children with rare diseases. Our outstanding research groups drive this search. But our research is also bolstered by our ability to look back—as in the study by Dr. Sanders—and learn from our vast transplant experience in managing rare diseases.
To find out more about our research, and to see which clinical trials might be appropriate for your patients, see our updated listing of open pediatric trials.
Please contact us if you have questions about any of our services for your patients.
K. Scott Baker, MD, MS
Director, Pediatric Blood and Marrow Transplantation
Director, Survivorship Programs, Fred Hutchinson Cancer Research Center and Seattle Children’s Hospital Professor of Pediatrics, University of Washington School of Medicine
What happens to children with severe aplastic anemia (AA) in the decades after bone marrow transplantation? Early survival after transplantation in these young patients is known to be excellent, especially in those with matched sibling donors. But what happens to survivors after the first year? Do they grow up normally? Do they have complications?
Jean Sanders, MD, is determined—and ideally positioned—to answer these questions. The former director of the Pediatric Blood and Marrow Transplant Program at Fred Hutchinson Cancer Research Center, Sanders is a pioneer in developing newer and safer transplantation techniques. She and her colleague Rainer Storb, MD, were instrumental in developing today’s standard conditioning for AA patients: a combination of high-dose cyclophosphamide and antithymocyte globulin (ATG).
While non-transplant therapies for AA such as ATG, cyclosporine, and colony stimulating factors often allow patients to avoid transfusions for a while, many of these patients will never produce a normal marrow and some may go on to develop malignancies.
Thus, transplantation remains the best treatment option for children with severe AA who have matched donors or closely matched unrelated donors. And Sanders remains committed to documenting long-term survivorship patterns in her patients.
As more transplants are performed every year for marrow disorders like AA, and as outcomes continue to improve, answers to questions about long-term survivorship— especially in pediatric patients—become increasingly important.
All of which explains the significance of Sanders’ newly published study (Sanders et al. Blood 2011;118:1421-1428) reporting on long-term outcomes of AA patients who were younger than 18 years of age when transplanted in Seattle.
Study involved life-long surveillance of patients
The study evaluated late effects among 152 pediatric patients with severe AA after marrow transplantation at Fred Hutchinson Cancer Research Center. Sanders was personally involved in all of their transplants, making it truly the study of a lifetime’s work.
Sanders focused on children who survived at least one year after transplantation and she tracked them for one to 38 years (with a median of 21.8 years).
“Most of our patients got high-dose cyclophosphamide with or without ATG,” she says. “The literature tells us about patients with other diagnoses who take low-dose cyclophosphamide for years, but late effects with lower doses are likely different than those after a single exposure to 200mg per kilogram body weight of cyclophosphamide. That’s what I wanted these families and their physicians to know: What can you expect?”
Overall, the data were reassuring, says Sanders. They show that the majority of people transplanted for AA during childhood can grow up to become normal functioning adults and have productive lives.
As reported by Sanders and her colleagues:
- For 137 patients with acquired AA, survival at 30 years was 82%
- For 15 patients with Fanconi anemia, survival at 30 years was 58%
- Survival among 117 patients without chronic graft versus host disease (GVHD) was 83%, versus a survival rate of 62% in 35 patients with chronic GVHD
- Multivariate analysis confirmed that chronic GVHD (P = 0.02) and Fanconi anemia (P = 0.03) negatively impact survival
- 15 of the 16 patients (93%) with acquired AA who received transplant from unrelated donors survived during their 1 to 24 year observation period
- Late causes of death included: chronic GVHD (4), malignancy (4), pulmonary failure (3), hepatitis C related liver disease (3), suicide (2), hemolytic anemia (1), measles/pneumonia (1), and HIV (1).
- There was an increased incidence of thyroid function test abnormalities among those who received total body irradiation (TBI)
- The proportion of patients developing malignancy was greater among the 28 patients who had TBI (37%) compared with those who did not (15%)
- Cyclophosphamide recipients had normal growth, basically normal development, and pregnancies with a minimal number of minor birth defects (3 defects in 132 evaluable births: aortic stenosis, hip dysplasia, cleft lip)
- Quality of life studies in 49 adult patients indicated that patients were comparable with controls except for difficulty with insurance issues (health and life)
Improvement needed to reduce GVHD
These study results confirm that transplantation is effective therapy for children with severe AA.
“Overall, they are doing very well,” says Sanders. “The children grow up and have children of their own. But clearly, improved methods for prevention, early diagnosis, and treatment of chronic GVHD are needed to improve survival. This is particularly important because the acceptable transplant donor pool continues to be expanded and rates of GVHD are higher in unrelated and mismatched settings.”
Currently, methotrexate and cyclosporine are mainstays to reduce the incidence of GVHD, which stands at around 20 or 30 percent in matched sibling transplants. Some pediatric clinical trials at Seattle Cancer Care Alliance are aimed at finding new treatments to reduce GVHD rates in matched, unrelated, and mismatched transplants.
The lower survival rate observed in this study’s Fanconi anemia population was not unexpected. These children have a genetic defect that makes their cells particularly sensitive to cyclophosphamide and therefore require a lower dose conditioning regimen. After the transplant, because they still harbor the faulty gene in somatic cells, they also remain highly susceptible to secondary head and neck cancers. Because of these special risks, SCCA and other FA treatment centers have developed special transplant and post-transplant regimens as well as alternatives such as gene therapy.
Guidance for AA patients considering transplantation
“Survival is important,” says Sanders, “but the quality of survival is also very important and it is gratifying that these patients are not different from control patients in the overall quality of life.”
The unique long-term perspective of this study makes it extremely instructive in guiding the counseling of future pediatric patients undergoing transplantation for severe AA.
“Dr. Sanders was one of the first people to do research on long-term complications of pediatric transplantation,” says Scott Baker, MD, director of Pediatric Blood and Marrow Transplant Program at Seattle Cancer Care Alliance.
“She has been involved in the care and treatment of these patients going all the way back to the 1970s, which is the beginning of the whole field of transplantation. So this study—the most comprehensive long-term study of AA ever done—really ties together her more than three decades of patient care and research.”
“ Sanders and colleagues have to be congratulated for this lifelong surveillance of patients with this rare disease. Mainly because of the efforts of Drs. Sanders and Storb to improve outcomes, the conditioning regimen they developed many years ago… has become the gold standard worldwide, leading to sustained engraftment in most patients with few late effects, notably often preserving fertility.” From editorial accompanying the study described in this story (Socie G. Blood 2011;118:1194-1195.)
In late 2011, Seattle Children’s Hospital and Seattle Cancer Care Alliance opened enrollment in the first-ever clinical trial of lentiviral vector gene therapy for patients with Fanconi anemia (FA), a very rare inherited disease that affects the bone marrow as well as other organs and tissues.
While hematopoietic cell transplantation (HCT, also referred to as bone marrow transplantation or BMT) is now a standard treatment for FA, many patients lack an HLA-matched donor or are too ill for transplant. Researchers hope that this new form of gene correction will be a safe and effective alternative for this group of FA patients.
Initial efforts to insert a normal gene into a patient’s blood stem cells have been unsuccessful. These previous attempts—in FA as well as other monogenetic diseases— used a gammaretroviral vector, which in some patients produced undesired side effects when the virus vehicle triggered oncogene activation and leukemia.
But now, based on preclinical studies done at Fred Hutchinson Cancer Research Center, as well as preliminary successes in patients, the safety-optimized lentivirus vector has emerged as the vector best suited for FA gene transfer. The chief advantage of this self-inactivating lentiviral vector is its apparent nonmutagenic gene insertion. Another advantage is the shorter period needed to insert the gene into the patient’s cultured cells. Faster transduction is essential because FA cells are intolerant of prolonged periods outside the body.
Fanconi anemia: A complex, multi-organ disease
Fanconi anemia is caused by an abnormal gene that prevents DNA repair. There are at least 15 known genes (called ‘complementation groups’) associated with FA. Every year in the Unites States, about 30 babies are born with this recessive disorder.
One of the most common effects of FA is bone marrow failure, which results in fatigue, infection, and excess bleeding. Severe aplastic anemia is the end-stage of marrow failure. Leukemia is another risk. Because the FA gene defect is found in all cells, not just blood cells, patients with FA are also prone to physical birth defects, growth problems, solid tumors, abnormal hearts and gastrointestinal tracts, and an array of other serious health problems. Many FA patients do not reach adulthood.
“Patients with Fanconi anemia are complex,” says Akiko Shimamura, MD, PhD, a hematologist and director of the Fanconi Anemia Center at Seattle Children’s. “They often have multi-organ problems and their treatment requires a coordinated multidisciplinary approach.”
The Fanconi Anemia Center at Seattle Children’s is one of the few comprehensive care centers for this disease. Shimamura says that patients with FA require a full evaluation, close monitoring, and ongoing specialty care from pediatric subspecialists. They also require access to an experienced bone marrow transplant program.
Improving the transplant option
Allogeneic hematopoietic cell transplantation is a lifesaving option for many people with FA.
“When kids with FA start to need a transfusion—when their blood counts go down—that is part of the trigger for transplant,” says K. Scott Baker, MD, director of Pediatric Blood and Marrow Transplantation at SCCA. Over a 10-year period while at the University of Minnesota—one of the nation’s largest FA centers—Baker helped to improve transplant success and track long-term outcomes after transplantation in children with FA.
“We know historically that patients with FA require very individualized protocols,” he says. “All the cells in their body are hypersensitive to the damaging effects of chemotherapy and radiation. Typically, they can tolerate just about a tenth of the standard conditioning doses given in leukemia or nonmalignant diseases.”
Hutchinson Center researchers helped develop the low-dose cyclophosphamide regimen that is now a standard of care in conditioning many FA patients. Using ultra low-dose preparative treatments, the transplant outcomes in FA patients are now excellent—especially in those with a matched sibling donor.
However, all FA patients remain at elevated risk for later head and neck cancers—a risk that may be exacerbated by the graft versus host disease (GVHD) that often follows transplantation in patients with alternate donors. In an attempt to reduce that risk, researchers at Hutchinson Center have partnered with other leading FA centers to study the use of busulfan instead of radiation in conditioning for FA patients (NCT00987480).
Another SCCA study underway for FA patients involves low-dose fludarabine-based conditioning followed by post-transplant cyclophosphamide (FHCRC-2064) www.seattlecca.org/clinical-trials/transplant-2064.cfm.
“We know that patients with FA don’t tolerate standard transplant regimens,” says Baker. “So we have developed reduced-intensity or even radiation-free protocols as well as transplants for those who lack a matched donor. But sometimes a transplant is still just too risky—and that’s why our researchers here at Hutchinson Center are now offering the first lentiviral vector gene therapy trial for FA patients.”
New FA gene transfer trial details
The primary purpose of the new Phase I gene therapy study at SCCA is to measure safety (NCT01331018) visit, http://www.seattlecca.org/clinical-trials/transplant-NCT01331018.cfm. As an extra precaution, the FDA has recommended that only adults (>18 years of age) be enrolled initially. The study is also limited to patients in FA complementation group A (the most common mutation, seen in about twothirds of cases) and without an HLA-matched sibling donor.
“Hematopoietic cell transplantation has improved immensely for FA patients with a matched sibling,” explains Hans-Peter Kiem, MD, an FA researcher and gene therapy expert at Hutchinson Center and the University of Washington. “Especially when we can treat patients early before they have transfusions or infections, they do extremely well. That’s why our new FA gene therapy trial is only for patients without a matched sibling donor. We hope to expand enrollment soon from adult to pediatric patients.”
The procedure itself is a straightforward autologous transplantation with gene-corrected cells. Kiem describes the lentiviral vector as simple, containing only the correct FA gene and a weak promoter. He says a key region of the viral backbone is designed to be self-inactivating, which makes it nonfunctional upon integration into the genome (or DNA) and therefore possibly safer.
“After enrolling in the study,” says Kiem, “the patient will come to SCCA and we stimulate their stem cells in the blood before collecting them with a leukapheresis. If needed, we do a bone marrow harvest to collect sufficient numbers of stem cells. We culture their cells with the lentiviral vector and then re-infuse the treated cells. Patients do not receive any conditioning regimen such as those used in allogeneic transplantation.”
Families, patients, or physicians wanting more details about the study should contact Seattle Cancer Care Alliance at 1-800-804-8824. Hans-Peter Kiem, MD may be reached at (206) 667-4425.
Looking ahead: genome engineering for FA
Even as the gene therapy trial just gets underway, FA researchers at the Hutchinson Center, Seattle Children’s, and UW are already looking ahead to the next generation of therapies for FA and other rare inherited diseases.
• O ne line of research involves the use of homing endonucleases and other DNA-targeted agents to pinpoint gene correction of FA defects within the patient’s own cells. To pursue this type of precision-targeted gene repair, Andrew Scharenberg, MD, of Seattle Children’s recently received a multi-million dollar grant from the NIH to support a seven-laboratory team in the Northwest Genome Engineering Consortium. See “An Editor’s Guide to Correcting Faulty Genes” for a basic description of gene therapy strategies.
- Another major research effort with implications for FA patients is led by Toshi Taniguchi, MD, PhD, who made landmark discoveries about DNA repair mechanisms while researching Fanconi anemia at Dana-Farber Cancer Research Institute in Boston. Now at Hutchinson Center, Taniguchi remains focused on investigations into FA, DNA repair, and cancer susceptibility.
- Drs. Shimamura and K iem are also working on generating efficient strategies to derive blood stem cells from reprogrammed skin cells or so called induced pluripotent stem cells. This approach would allow the generation of large numbers of blood stem cells from skin fibroblasts or other cells.
- Other FA-related research at SCCA includes screening for drugs that alter specific FA pathways such as ubiquitization and developing a rapid high-throughput screening test to speed diagnosis and assist in family genetic counseling.
According to Shimamura, patients and families dealing with FA benefit greatly by seeking out an FA center that offers not only multi-specialty care and transplants but also access to emerging treatments such as gene therapy.
She says the FA Center in Seattle provides exactly this type of research-driven approach: “Families looking for a lifetime of care and hope should know that all of our Fanconi anemia and bone marrow disorder treatment involves partnerships with our researchers. Our center is poised to translate leading-edge biomedical research advances to improve the care of our patients.”
Patients, families, or physicians who want more information about the Fanconi Anemia Center in Seattle can call 1-800-804-8824 to get a brochure or request specific information about FA multispecialty care at Seattle Children’s.
An inherited mutation is like a typo on one page of a thick book. Every cell in the body has a full copy of the book. If the mistake happens to fall on a page of essential reading for normal cell function, disease ensues. Increasingly, gene researchers are acting like book editors to correct these gene typos.
Here is a quick guide to understanding two of the main gene therapy strategies currently being pursued in Fanconi anemia and other single-gene disorders.
Option 1: Pasting in a whole new page (gene therapy or gene transfer)
In many gene therapy techniques, a whole new corrected gene and its accompanying promoter, which helps turn on the gene, is placed inside a virus that specializes in slipping its genetic information into the human genome. This is like printing up a new addendum or errata page and sticking it inside the book. The hope is that the cell will find and read the information on the corrected slip sheet.
The problem so far with this method has been where the viral vector pastes in the new page. Gammaretroviral vectors, for example, tend to put the new page in a spot that triggers activation of the cell’s own cancerous genes. This explains why some initial gene therapy trials with gammaretroviral vectors triggered cancer.
The lentiviral vector, however, tends to insert the new page in a safer location. Preliminary tests show that cells don’t react against the new DNA—and they seem to find, read, and act on the corrected gene. The lentiviral vector also works faster, needing only about a day to correct a batch of patient stem cells versus three to five days for the gamma retrovirus. This speed is important because FA cells can’t survive long in culture.
Option 2: Editing the original text, reprinting the book (genome engineering)
Appropriate in this age of digital publishing, one of the newest options for correcting a book’s genetic error involves:
- Recalling some of the faulty books (i.e., isolation of patient stem cells in the lab),
- Opening up the book’s actual “Word file” and helping the cell’s own internal DNA repair mechanisms make exact corrections (i.e., targeted DNA repair), and then
- Quick-printing some new books and re-issuing (i.e., culturing the corrected cells and then re-infusing them into the patient).
Note that not all faulty cells throughout the body can be recalled and corrected. However, re-issuing corrected copies of the stem cell line alone is often sufficient to set the record straight and prevent disease—especially when treating marrow disorders or immunodeficiencies. This method of high-precision gene repair is sometimes referred to as genome engineering.
Many types of genome engineering are currently being explored at Hutchinson Center and the Northwest Genome Engineering Consortium. Most employ endonucleases, which are enzymes that can be engineered to locate and cut a very specific sequence of DNA. After snipping the DNA, the cell’s own DNA repair mechanism (sort of the cell’s “in-house editors”) can be prompted with a master template of the gene to auto-correct the patient’s gene. Researchers hope that targeted gene repair, because it maintains “the full original context” around the corrected gene, will promote normal gene reading and function.
The SCCA Adult Bone Marrow Transplant News is a publication presenting the latest information on bone marrow transplant research at SCCA, providing up-to-date information for all health care professionals caring for transplant patients.
Read about important outcomes research at the Hutchinson Center that may benefit your patients.
Each issue of Clinical Trials Monthly highlights several of the more than 200 clinical trials that are currently recruiting patients at SCCA.
Each quarterly Leading Edge newsletter will highlight a new topic to give you the latest news on leading-edge therapies that SCCA physicians are offering.