Follow-up from ADA-SCID Trial Shows Impressive Results Compared to Historical Data


ADA-SCID is a form of Severe Combined Immunodeficiency (SCID) which is caused by Adenosine Deaminase Deficiency. A lack of the ADA gene in the body results in impaired development of the immune system. This means the body faces extreme difficulty fighting off fungal, viral, and bacterial infections. ADA-SCID can be fatal and while there are some therapies for the condition, patient response isn’t as universal as we’d hope.

This condition affects approximately one in every 500,000 people in the United States.

Thankfully, positive results from an ongoing clinical trial conducted by Orchard Therapeutics has brought increasing promise for a new type of therapy for this condition.


The results Orchard recently presented were two-year follow-up data from a trial investigating OTL-101 as a treatment option for ADA-SCID. This type of stem cell therapy has already received Orphan Drug Designation and Breakthrough Therapy Designation by the FDA for the treatment of this disease. It has also received Orphan Drug Designation by the EMA.

OTL-101 is a form of stem cell therapy which is autologous and ex vivo. Instead of administering healthy cells from a related donor, OTL-101 uses modified cells from the patient, and then re-administers them to the body.

This trial of OTL-101 has been ongoing for quite some time. Some patients are almost at the five-year mark post treatment. However, the most recent results come from a 24 month data set from 20 pediatric patients.

This subgroup of participants all lacked an eligible bone marrow donor. The median age that these patients were treated with OTL-101 was 9 months.

This subgroup was compared to a historical group of 26 patients who had been treated with a hematopoietic stem cell transplant (HSCT). Of these individuals, 12 had received the transplant from a related donor and 14 had not. The median age that these patients were treated with HSCT was 7.3 months.

Results and Future Plans

Results from the group of 20 pediatric patients were extremely positive. After 24 months, 100% of the participants had survived without events. In the historical group, 88% of patients survived, and 56% survived event free.

Other results for the OTL-101 group include:

  • 90% were able to stop immunoglobulin replacement therapy
  • 0% had to restart enzyme replacement therapy
  • OTL-101 was well-tolerated
  • 0% developed graft versus host disease

Results from the historical HSCT group include-

  • 55% were able to stop immunoglobulin replacement therapy
  • 3 had to receive long-term enzyme replacement therapy
  • 7 required rescue HSCT
  • 5 experienced acute graft versus host disease
  • 3 experienced chronic graft versus host disease
  • 1 individual died due to graft versus host disease

These results support the continued development of OTL-101 as a therapeutic option for ADA-SCID. The company hopes to file for FDA approval of OTL-101 in 2020. Orchard Therapeutics anticipates that the development of this treatment will not only help boost the immune system of ADA-SCID patients, but improve quality of life for this rare condition.

You can read more about this new potential therapy for ADA-SCID here.

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