This study is a post approval commitment to evaluate the accuracy and precision of retroviral insertion site (RIS) analysis and its utility for investigating and predicting the potential for insertional oncogenesis in subjects treated with Strimvelis.

This non-interventional, retrospective, methodology study will use peripheral blood and bone marrow samples previously taken from subjects treated with Strimvelis. The study does not require subjects to undergo any further treatment, intervention or blood withdrawal.

The objective of this methodology study is to evaluate the accuracy and precision of shearing extension primer tag selection ligation-mediated polymerase chain reaction (S-EPTS/LM-PCR) for RIS analysis and its utility for investigating and predicting the potential for insertional oncogenesis in subjects previously treated with Strimvelis for severe combined immunodeficiency (SCID) due to adenosine deaminase (ADA) deficiency.

Inclusion Criteria

Subjects must have previously received treatment with gRV-GT, either during clinical development (clinical trials and early access programs) or in the post-marketing setting as the approved product (Strimvelis) or under hospital exemption, and for whom at least one biological sample is available that meets the following eligibility criteria::

1. Peripheral blood, bone marrow, or DNA extracted from either source.
2. Taken at least 6 months after gRV-GT.
3. Stored at -20oC or below since the time of sampling.
4. Likely to provide at least 1.5 μg of DNA (following extraction by the central laboratory).

Exclusion Criteria N/A

This study will use biological samples previously taken from subjects treated with Strimvelis gRV-GT.