The European Medicines Agency has granted Orchard Therapeutics’ experimental gene therapy OTL-300 PRIME designation as a potential treatment for the most severe form of beta-thalassemia.

The move allows the firm closer engagement with the regulator to both optimise development and accelerate evaluations of applications.

To be accepted for PRIME, an investigational therapy must show potential therapeutic advantage over available treatment options or benefit patients with no current treatments, the firm noted.

OTL-300, which was acquired by Orchard from GlaxoSmithKline in April 2018, is an investigational autologous ex vivo lentiviral gene therapy for the treatment of transfusion-dependent beta-thalassemia (TDBT).

TDBT is a rare inherited blood disorder caused by one of over 200 mutations in the beta-globin gene.

The condition is characterised by failure to grow and gain weight, infection, and life-threatening anemia, which occur within the first two years of life.

The only curative approach is allogeneic haematopoietic stem cell transplantation, which is linked with significant transplant-related morbidity and mortality.

Most patients with TDBT undergo chronic blood transfusions due to the severity of their symptoms and, as a result, often develop side effects such as iron overload, which requires additional iron chelation therapy, Orchard said.

PRIME designation for OTL-300 is based on data from preclinical and early clinical programmes, including that collected from nine patients in an ongoing proof-of-concept clinical trial.

Significant reductions in blood transfusion frequency and volume requirements were observed in five of seven patients with at least one year’s follow up.

Also, three of the four paediatric patients were transfusion-free around one month after treatment, and reductions in transfusion volume requirements were recorded in two out of three adult patients, with one transfusion-free over a period of nine months.

All patients are alive, and safety data from the nine patients treated in the trial indicate OTL-300 was generally well-tolerated.

“We are encouraged by the early clinical trial data in TDBT patients, which was started in 2015 in hopes of extending the hematopoietic stem cell gene therapy approach that has been so successful in such conditions as adenosine deaminase severe combined immunodeficiency (ADA-SCID), Wiskott–Aldrich syndrome (WAS) and Metachromatic Leukodystrophy (MLD) to other diseases with unmet medical needs such as TDBT,” said Giuliana Ferrari, the research scientist who leads the thalassemia gene therapy project at the San Raffaele- Telethon Institute for Gene Therapy.

“Hematopoietic stem cell gene therapy could offer a promising alternative to the current standards of care for adults and children living with TDBT.”