Can gene therapy help cure sickle cell disease?

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By Dennis Thompson
HealthDay Reporter

MONDAY, Dec. 13, 2021 (HealthDay News) – Gene therapy that could provide a lasting cure for sickle cell disease continues to show success through the third wave of patients, the researchers report.

LentiGlobin therapy restored normal blood function in 35 sickle cell patients who had a single procedure, according to Clinical trial findings published Dec. 12 in New England Journal of Medicine.

All patients now produce stable amounts of normal red blood cells containing healthy hemoglobin, said lead researcher Dr. Julie Kanter, director of the University of Alabama at the Sickle Cell Adult Clinic in Birmingham.

In addition, they have not suffered the severe episodes of pain that come with sickle cell disease, she said.

“It’s the beginning of a new life” for these patients, Kanter said.

About 49 patients have been treated with LentiGlobin so far, according to the gene therapy manufacturer, a pharmaceutical company. Bluebird Bio.

Sickle cell disease affects a person’s red blood cell shape. Usually, these cells are disc-shaped and flexible enough to move easily through blood vessels.

The red blood cells of a person with sickle cell disease are crescent-shaped, sickle-shaped. The cells are stiff and sticky, and cause pain episodes and other health problems when they accumulate in different parts of the body.

These problems are caused by a substance called hemoglobin, which is part of the red blood cells that carry oxygen to tissues throughout the body, Kanter explained. A faulty gene causes the body to produce defective hemoglobin which distorts the shape of blood cells.

“They still carry oxygen, but they don’t retain oxygen, and when cells release oxygen, hemoglobin intertwines with its hemoglobin counterparts, causing cell and sickle deformity,” Kanter said.

In this therapy, Stem cells they are removed from the bone marrow of the person who produces the blood. Laboratory technicians expose them to a virus that inserts a healthy copy of the defective hemoglobin gene into them.

As this happens, the patient’s remaining bone marrow is killed chemotherapy. Laboratory-repaired stem cells are then implanted and begin to produce healthy hemoglobin.

“This is like working a bone marrow transplantation into yourself, ”said Dr. Lewis Hsu, chief medical officer of the American Sickle Cell Disease Association.

Clinical trial update published in NEJM – and presented at the same time at the meeting of the American Society of Hematology in Atlanta – said that even three years after their treatment, the third wave of patients LentiGlobin showed a number of promising signs that indicate a permanent cure:

  • Almost all of their red blood cells contain healthy hemoglobin, instead of defective hemoglobin caused by defective genes.
  • Their red blood cells break down at a normal rate; sickle cell disease usually causes cells to break down much faster.
  • No one experienced episodes of severe pain that brought them to the emergency room; before treatment, they usually suffered more than three a year.

“This is a huge improvement, because many of these people had multiple events before this transplant, where they were in the hospital or in the emergency room because of these horrible painful events,” Kanter said.

Researchers continue to monitor patients for the ultimate indicator of true healing – the long-term health of their organs. The sickle cell puts stress on the kidneys, lungs, heart and brain, and we hope that LentiGlobin treatment will prevent organ damage caused by the disease.

“We just don’t know it yet because it takes a lot of time to gather that information, but it’s really exciting,” Kanter said.

The sickle cell disease community is striving for the success of LentiGlobin, Hsu said.

“This is the gene therapy that is now the longest for sickle cells,” he said.

However, Hsu pointed out that there are security issues that still need to be ironed out by the procedure.

One of the first patients treated with LentiGlobin developed leukemia about five years later and died, Hsu said.

Another paper published in new NEJM shed some light on her death, explaining that LentiGlobin did not directly cause her leukemia. Instead, it appears to be in some way caused by her sickle cell disease combined with the transplant procedure.

Leukemia was a concern over this therapy, Kanter said.

“We worry that when a virus enters a new gene, it puts it somewhere it shouldn’t,” she said. “It didn’t do it. It didn’t happen. It wasn’t related to LentiGlobin itself at all, but we think it was related to the stem cell transplant process.”

Since that first wave of patients, Kanter said, researchers have changed the way stem cells are collected and the way the virus is introduced to them.

Researchers hope the changes will prevent the process that caused the leukemia. “We hope we’ve prevented additional stress on the bone marrow,” Kanter said.

Combined, these two papers “show really good results.” Hsu said it is now a matter of understanding what risks gene therapy can pose.

“The fact that this has not yet been explained still makes us look at the success of this and realize that there are still risks in gene therapy, there are still risks in clinical trials,” he added.

Kanter expects LentiGlobin to move to approval from the U.S. Food and Drug Administration in the next few years. The drug is likely to be expensive, given the cost of therapy, chemotherapy, and weeks spent in the hospital.

“Unfortunately, I think it will be very expensive for a long time to come. The next steps are how to make it easier and cheaper and more affordable,” Kanter said.

More information

The American National Institutes of Health has more about sickle cell disease.

SOURCES: Julie Kanter, MD, Director of the Sickle Cell Adult Clinic and Associate Professor, Department of Hematology and Oncology, University of Alabama at Birmingham; Lewis Hsu, MD, PhD, Chief Medical Officer, Sickle Cell Disease Association of America, Hannover, Md .; New England Journal of Medicine, 12 December 2021, online; presentation, meeting of the American Society of Hematology, Atlanta, December 12, 2021.

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