The ability to edit genes in patients’ blood
stem cells — which produce red blood cells, platelets, immune cells and more — offers
the potential to cure many genetic blood disorders. If all goes well, the
corrected cells engraft in the bone marrow and produce healthy, properly
functioning blood cells… forever.
But scientists have had difficulty introducing
edits into blood stem cells. The efficiency and specificity of the edits and
their stability once the cells engraft in the bone marrow have been variable.
A new approach, described this week in Nature Medicine and in January in the journal Blood, overcomes prior technical challenges, improving the efficiency, targeting and durability of the edits. Researchers at Dana-Farber/Boston Children’s Cancer and Blood Disorders Center and the University of Massachusetts Medical School successfully applied the technique to two common blood diseases — sickle cell disease and beta thalassemia — involving mutations in the gene for beta globin protein.
Manny Johnson of Boston, 21, previously required monthly blood transfusions to keep his severe sickle cell disease under control. After receiving a new gene therapy treatment, he’s been symptom-free for six months.
It’s been known for more than 40 years that in rare individuals, lingering production of the fetal form of hemoglobin — the oxygen-transporting protein found in red blood cells — can reduce the severity of certain inherited blood disorders, most notably sickle cell disease and thalassemia. Typically, however, a protein called BCL11A switches off fetal hemoglobin production past infancy, but exactly how this happens has not been well understood until now.
Another approach to curing sickle cell disease is already being evaluated in a new clinical trial at Dana-Farber/Boston Children’s. The novel gene therapy restores fetal hemoglobin production by genetically suppressing BCL11A, which prevents it from blocking fetal hemoglobin production. Learn more.
“Genetically modifying this TGACCA segment could be another possible strategy to cure sickle cell disease by blocking BCL11A’s ability to bind to this DNA site and switch off fetal hemoglobin production,” says Stuart Orkin, MD, senior author on the study. …
Boston Children’s Hospital is now enrolling patients age 3 to 35 in a clinical trial of gene therapy for sickle cell disease. Based on technology developed in its own labs, it differs from other gene therapy approaches by having a two-pronged action. It represses production of the mutated beta hemoglobin that causes red blood cells to form the stiff “sickle” shapes that block up blood vessels. It also increases production of the fetal form of hemoglobin, which people normally stop making after birth.
Fetal hemoglobin doesn’t sickle and works fine for oxygen transport. The gene therapy being tested now restores fetal hemoglobin production by turning “off” a silencing gene called BCH11A.
“BCL11A represses fetal hemoglobin and also activates beta hemoglobin, which is affected by the sickle-cell mutation,” David Williams, MD, the trial’s principal investigator, told Vector last year. Williams is also president of the Dana-Farber/Boston Children’s Cancer and Blood Disorders Center. “So when you knock BCL11A down, you simultaneously increase fetal hemoglobin and repress sickling hemoglobin, which is why we think this is the best approach to gene therapy in this disease.”
The therapy is the product of multiple discoveries, the first dating back 70 years. Click selected images below to enlarge. …
Research going back to the 1980s has shown that sickle cell disease is milder in people whose red blood cells carry a fetal form of hemoglobin. The healthy fetal hemoglobin compensates for the mutated “adult” hemoglobin that makes red blood cells stiffen and assume the classic “sickle” shape.
Normally, fetal hemoglobin production tails off after birth, shut down by a gene called BCL11A. In 2008, researchers Stuart Orkin, MD, and Vijay Sankaran, MD, PhD, at the Dana-Farber/Boston Children’s Cancer and Blood Disorders Center showed that suppressing BCL11A could restart fetal hemoglobin production; in 2011, using this approach, they corrected sickle cell disease in mice.
Now, the decades-old discovery is finally nearly ready for human testing — in the form of gene therapy. Today in the Journal of Clinical Investigation, Dana-Farber/Boston Children’s researchers report that a precision-engineered gene therapy vector suppressing BCL11A production overcame a key technical hurdle. …
Funding drives biomedical research, and research drives treatment innovation. Access to funds, particularly National Institute of Health (NIH) awards, is critical to move research forward. The 21st Century Cures Act, which passed the U.S. House on July 10, could give the NIH $8.75 billion more in new grants to disperse over the next five years, the largest increase since the Recovery Act of 2009.
How would those funds be used? Can research find a better way to treat patients? Prevent disease? Disseminate advances in medicine?
In 2014, Boston Children’s led the U.S. in NIH awards. Here’s a look at how a few research teams are leveraging NIH funding to improve care for both children and adults.
Painful, tissue-damaging vaso-occlusive crises (a.k.a. pain crises) are one of the key clinical concerns in sickle cell disease (SCD). The characteristic C-shaped red blood cells of SCD become jammed in capillaries, starving tissues of oxygen and triggering searing pain. Over a patient’s life, these repeated rounds of oxygen deprivation (ischemia) can take a heavy toll on multiple organs.
There’s some debate as to why these crises take place—is the sickled cell’s shape and rigidity at fault, or are the blood vessels chronically inflamed and more prone to blockage? Either way, doctors can currently do little to treat vaso-occlusive crises, and nothing to prevent them.
Ask many doctors about their image of a child with sickle cell disease (SCD), and they’ll describe a short, skinny child, perhaps almost malnourished. For decades, that image was accurate.
That perception needs to change, though. A group of sickle cell specialists from hospitals in New England—members of the 11 institutions in the New England Pediatric Sickle Cell Consortium (NEPSCC)—recently made a surprising observation: Nearly a quarter of children with SCD are overweight or obese. The question is, why?
The answer may start with their red blood cells (RBCs). …
As a hematologist, I see all too many children battling blood disorders that are essentially untreatable. Babies with immune deficiencies living life in a virtual bubble, hospitalized again and again for infections their bodies can’t fight. Children disabled by strokes caused by sickle cell disease, or suffering through sickle cell crises that drug treatments can’t completely prevent. Children whose only recourse is to risk a bone marrow transplant—if a suitably matched donor can even be found.
Over the past 20 years, my lab and that of George Daley, MD, PhD, at Boston Children’s Hospital have worked hard to give these children a one-time, potentially curative option—a treatment that begins with patients’ own cells and doesn’t require finding a match. …
I had to admit that I didn’t. I’ve always thought of sickle cell—a painful and debilitating disease caused by an inherited mutation that makes red blood cells stiffen into a characteristic sickled shape—as a chronic disease to be managed, not one that could be cured.
I’m not alone in that belief. Lehmann often asks this question when she give talks for medical students, residents and other physicians. Their reaction is puzzlement, then a shaking of heads.