bluebird bio’s beta thalassaemia gene therapy Zynteglo scores promising long-term data

bluebird bio has revealed some long-term data for its gene therapy betibeglogene autotemcel, which is marketed as Zynteglo in the European Union.

bluebird bio announced the new long-term data at the annual American Society of Haematology (ASH) meeting, reflecting up to six years of safety and efficacy data for the gene therapy in patients with transfusion-dependent beta thalassaemia (TDT).

Zynteglo, or beti-cel, is a one-time gene therapy designed to add functional copies of a modified form of the β-globin gene to a patient’s blood stem cells.

This gives patients the potential to produce haemoglobin (Hb) A, which is a gene therapy derived adult Hb.

This is particularly important as TDT patients have mutations in the β-globin gene that cause reduced or significantly reduced Hb levels. This means that people living with TDT need chronic blood transfusions to maintain adequate Hb levels in order to survive.

Among 32 patients enrolled in the 13-year, long-term LTF-303 study, 64% of patients treated in the phase 1/2 portion and 90% in the phase 2 portion achieved transfusion independence (TI).

In bluebird bio's studies of Zynteglo, TI is defined as no longer needing red blood cell transfusions for at least 12 months, while maintain a weighted average Hb of at least 9 g/dL.

In the LTF-303 study, all patients who achieved TI remained free from transfusions , with the median duration of ongoing TI coming in at 39.4 months.

bluebird bio also revealed data from 24 paediatric patients who were treated with the gene therapy in the phase 3 Northstar-2 and Northstar-2 studies, reflecting a median follow-up of 15.5 months.

Across these studies, following treatment with Zynteglo, 87% of evaluable patients under the age of 16 years achieved TI. bluebird bio added that as of 3 March 2020 these patients continued to be free of transfusion for a median duration of 14.9 months.

“All of the patients in our phase 3 studies who achieved transfusion independence have maintained it, with the durability of the treatment effect underscored by patients from our earlier studies reaching their five-year anniversaries of freedom from transfusions,” said David Davidson, chief medical officer, bluebird bio.

“Moreover, transfusion independence has been observed in paediatric, adolescent and adult patients and across genotypes – suggesting outcomes with this gene therapy may be consistent regardless of age or genotype,” he added.