May 08, 2026 —
Spur Therapeutics presented new data from the GALILEO-1 and GALILEO-2 trials of avigbagene parvec, also known as FLT201, its investigational AAV gene therapy for Gaucher disease type 1 (GD1). The findings, presented at the International Working Group on Gaucher Disease 2026 Symposium, suggest that a one-time gene therapy approach may help address skeletal disease, a major and persistent source of morbidity in patients with GD1.
Gaucher disease is caused by mutations in the GBA1 gene, resulting in deficient activity of glucocerebrosidase (GCase). This enzyme is needed to break down certain fatty molecules, and when GCase activity is insufficient, toxic substrate accumulation can affect multiple tissues, including the bone marrow, liver, and spleen. Although enzyme replacement therapy and substrate reduction therapy can help control many systemic manifestations of Gaucher disease, bone complications may persist even after years of standard treatment.
Bone disease is one of the most important unmet needs in GD1. Patients may experience bone marrow infiltration, reduced bone mineral density, chronic pain, skeletal abnormalities, and increased fracture risk. These complications can develop silently and may not be fully reflected by conventional measures such as hematologic parameters or liver and spleen volume.
In the reported analysis, Spur focused on four adult GD1 patients who had been on stable enzyme replacement therapy or substrate reduction therapy for at least two years before enrollment and were later taken off standard therapy after receiving FLT201. All patients had moderate to severe bone marrow burden at baseline. Following treatment, one patient showed a clinically meaningful improvement in bone marrow infiltration, with the bone marrow burden score reduced from 11 to 7 at month 24 and improvement observed as early as month 3. Other participants generally maintained stable bone marrow disease over the two-year period.
The data also showed improvements in bone mineral density in some patients, including individuals whose systemic disease had otherwise been considered well controlled on standard therapy. This finding is important because it suggests that skeletal pathology may continue even when other disease markers appear controlled, and that FLT201 may have the potential to reach harder-to-treat tissue compartments such as bone.
FLT201 is designed to deliver a modified version of the GBA1 gene, enabling the body to produce a more stable form of GCase. Spur has suggested that the extended stability of GCase in the bloodstream and tissues may support deeper penetration into difficult-to-access tissues, including bone. In earlier analyses, treatment was associated with sustained increases in GCase activity and durable reductions in lyso-Gb1, a key biomarker of Gaucher disease burden.
The analysis also addressed the impact of corticosteroid-based immune management, which is commonly used after AAV gene therapy to manage potential immune responses. Initial declines in markers of bone turnover were observed, as expected with corticosteroid use, but these effects were reversible after steroid discontinuation. This may help inform immune management strategies in Gaucher patients, who already have an elevated risk of bone pathology.
Avigbagene parvec is now being evaluated in GALILEO-3, a confirmatory Phase 3 trial that is expected to enroll approximately 45 patients and may support both accelerated and full approval. While the current bone health findings come from a small dataset and require confirmation in larger studies, they add to the growing evidence that one-time AAV gene therapy could potentially address aspects of Gaucher disease that remain insufficiently treated with current lifelong therapies.
