Bluebird Bio said on Tuesday that it has suspended clinical trials regarding its gene therapy for sickle cell disease after receiving reports that two patients treated with the one-time treatment had been diagnosed with cancer.
The trials have been placed on ‘temporary suspension’ so that Bluebird can investigate the cancer cases to determine if it was caused by the recreated HIV virus used to deliver the gene therapy. The company has not yet established such a link.
In December 2018, Bluebird announced the diagnosis of myelodysplastic syndrome (MDS), a cancerous bone marrow disease, in a sickle cell patient who underwent its Lentiglobin gene therapy three years in advance. At that time, Bluebird concluded that the chemotherapy given to the patient to prepare for the gene therapy was probably the cause of the cancer, based on tests he had performed. The patient then passed away in July last year.
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However, the new cancer cases will once again address a potential cancer risk associated with Bluebird’s gene therapy – and also raise concerns for any gene therapy company using redesigned lentiviruses as part of the treatments.
Shares of Bluebird fell 32% to $ 31 on Tuesday – the lowest price in seven years.
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Bluebird said he received a report last week of acute myeloid leukemia in a patient with sickle cell disease who had been treated for more than five years with his Lentiglobin gene therapy.
Last week, Bluebird also said he had been diagnosed with myelodysplastic syndrome in a second patient with sickle cell, also treated with Lentiglobin.
“The safety of every patient who has participated in our studies or is treated with our gene therapies is a top priority for us,” Bluebird CEO Nick Leschly said in a statement. ‘We are committed to fully assessing these cases in partnership with healthcare providers who support our clinical studies and appropriate regulatory agencies. We think of these patients and their families during this time. ”
The Food and Drug Administration and the European Medicines Agency have both been briefed on the cancer cases and the suspension of the clinical trials, Bluebird said. The investigation into the cancer cases will try to determine if the Lentiglobin gene therapy could have caused the patient’s cancer by possibly placing the modified stem cells in the wrong place. This is a theoretical risk for any gene therapy that uses viruses as a delivery agent but has not yet been realized in clinical trials before Bluebird reported.
Before patients can be treated with gene therapy for sickle cell disease or other blood-related diseases, they must first administer a chemotherapy called busulfan, which clears the bone marrow – or “conditions” so that it can accept the healthy cells. delivered by gene therapy.
Cases of MDS have been previously reported in patients undergoing busulfan pedigree transplantation. Clinical trials are currently underway to develop more effective and safer ways to prepare patients for gene therapy. The research is important because even if gene therapies for sickle cell disease or related genetic diseases are approved, patients may be reluctant to try them for fear that the cure may also put them at increased risk of developing cancer later.
No cases of AML or MDS have been reported in patients with beta-thalassemia treated with Zynteglo, the European-approved Bluebird Gene Therapy, similar to Lentiglobin. However, the company has temporarily suspended the marketing of Zynteglo while the investigation into cancer cases is ongoing.