Cancer Diagnosis in Patient Given LentiGlobin Revised to Severe Anemia

Patricia Inácio, PhD avatar

by Patricia Inácio, PhD |

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Note: This story was updated June 16, 2021, to clarify that the HGB-207 and HGB-212 clinical trials were testing betibeglogene autotemcel, a gene therapy that uses the same viral vector as LentiGlobin. 

A patient diagnosed initially with the blood cancer myelodysplastic syndrome (MDS) after receiving LentiGlobin, Bluebird Bio’s investigational gene therapy for sickle cell disease (SCD), now has a revised diagnosis of transfusion-dependent anemia, the company announced.

A second patient who participated in the same study — the Phase 1/2 HGB-206 clinical trial (NCT02140554) — also was diagnosed with acute myeloid leukemia (AML), another type of a blood cancer. However, new analyses announced by the company last month indicated LentiGlobin was unlikely to be the cause of AML.

Bluebird Bio said it is working closely with trial investigators to identify the cause in the patient with transfusion-dependent anemia.

As a result of those two cases, Bluebird paused its two clinical trials, HGB-206 and the Phase 3 HGB-210 (NCT04293185), testing LentiGlobin in SCD patients. It also paused two other Phase 3 trials, HGB-207 (NCT02906202) and HGB-212 (NCT03207009), which were testing betibeglogene autotemcel (marketed as Zyntegelo in Europe) — a gene therapy that uses the the same viral vector as LentiGlobin — in patients with beta-thalassemia.

Bluebird already reported data from the new analyses to regulatory agencies, including the U.S. Food and Drug Administration (FDA) and the European Medicines Agency (EMA), and to study investigators. The company now hopes the new findings will allow all clinical holds the be lifted, with trials resuming by mid-year.

“We remain committed to our pioneering mission to deliver one-time gene therapies with life-long benefits to our patients. We are grateful for the clinical investigators and healthcare providers helping us better understand the recent safety events in our sickle cell disease studies,” Andrew Obenshain, president of severe genetic diseases at Bluebird Bio, said in a press release.

“We are confident that working with the FDA and EMA, we will be able to determine a positive path forward as we seek to re-open our clinical studies,” he added.

LentiGlobin is an investigational gene therapy that uses a harmless lentivirus to deliver a lab-made version of the HBB gene, containing instructions to make a modified, anti-sickling form of hemoglobin. Hemoglobin, the protein that carries oxygen in red blood cells, is defective in SCD patients.

By promoting the production of this anti-sickling version of the protein, LentiGlobin is expected to prevent the sickling and destruction of red blood cells, as well as other SCD complications.

The gene therapy is delivered to hematopoietic stem cells, which are found in the bone marrow and are able to give rise to all types of blood cells.

The procedure first requires stem cells to be collected from the patient and engineered to produce modified anti-sickling hemoglobin, before being placed back into the patient in the form of a stem cell transplant.

In the HGB-206 study, the first two groups of patients (group A and group B) who received LentiGlobin had their their hematopoietic stem cells harvested from the bone marrow. In the third group (group C), stem cells were collected from the blood following treatment with a mobilizing agent. Moreover, in this group, additional tweaks were made to increase the number of copies of the modified HBB gene and to boost transplant success (engraftment).

The patient now diagnosed with transfusion-dependent anemia was from group C.

Previous data from the study showed that LentiGlobin led to a sustainable increase in production of anti-sickling hemoglobin in red blood cells of patients from group A and B. It also lowered the frequency of several SCD complications, including vaso-occlusive crises (VOCs) and acute chest syndrome.

More recent data from the third group of patients also confirmed these findings and showed the investigational therapy was able to lower the levels of several markers of red blood cell destruction.