This study is a Phase 3, non-randomized, multicenter, efficacy and safety study in adult patients with Gaucher disease Type 1, on stable treatment with enzyme replacement therapy (ERT) or substrate reduction therapy (SRT) for at least 2 years. The study aims to confirm the efficacy and safety of FLT201 in this population after discontinuation of ERT/SRT.

Key Inclusion Criteria:

• Aged ≥18 years at time of screening.
• Clinical diagnosis of Gaucher disease type 1
• Stable hemoglobin concentration at baseline
• Stable platelet count at baseline
• Receiving ERT or SRT without interruption for at least 2 years

Key Exclusion Criteria:

• Diagnosed or suspected Gaucher disease type 2 or type 3
• Positive for AAVS3 neutralizing antibodies.
• Abnormal lab values, conditions or diseases that would make the participant unsuitable for the study
• Positive pregnancy test or lactating
• History of hematopoietic stem cell transplant (HSCT)/bone marrow transplant or any solid organ transplant.
• History of receiving any gene therapy or cell therapy.
• History of total splenectomy. Note: Additional protocol defined Inclusion and Exclusion criteria apply