Patients Treated With Spur Therapeutics’ Gaucher Disease Gene Therapy FLT201 Maintain Clinical Benefit for Up to 2 Years

Newly updated data from Spur Therapeutics’ phase 1/2 GALILEO-1 clinical trial (NCT05324943), which is evaluating the adeno-associated virus (AAV) vector-based gene therapy avigbagene parvec (also known as FLT201) for the treatment of Gaucher disease, has shown that patients who received the gene therapy have maintained clinical benefit for up to 2 years post treatment.^1,2 The data were presented at the European Society of Gene & Cell Therapy (ESGCT) 32nd Annual Congress, held October 7 to 10, in Seville, Spain.

The efficacy data presented included 4 patients who had discontinued their standard-of-care (SOC) therapy, which was either enzyme replacement therapy or substrate reduction therapy, in a time frame of 4 to 11 weeks after being treated with FLT201. The follow-up time for these patients ranged from 19 to 23 months, and as of the latest follow-up, all patients remained off their prior SOC therapy and showed improvement or maintenance of outcomes. Levels of dried blood spot (DBS) glucosylsphingosine (lyso-Gb1), which is in Gaucher disease a validated marker of treatment response according to Spur, were maintained or reduced from baseline measurements ranging from 10.3 to 486.4 ng/mL (mean, 167.9 ng/mL) to month 21 measurements ranging from 12.5 to 46.8 ng/mL (mean, 26.0 ng/mL). It was noted that this constituted an 84.5% reduction and that similar findings were seen with regard to plasma lyso-Gb1.

It was also reported that hemoglobin or platelet levels either remained in the normal range or improved in the 4 patients. Although 1 patient showed a transient drop in hemoglobin deemed related to a newly diagnosed iron deficiency, this patient’s hemoglobin levels were brought back to normal after starting use of iron supplements. Furthermore, the patients were noted to have maintained stability of liver and spleen volumes.

“People with Gaucher disease endure a heavy treatment burden, including lifelong biweekly infusions,” GALILEO-1 investigator Pilar Giraldo, MD, PhD, a hematologist at Hospital Universitario Quironsalud de Zaragoza, said in a statement.¹ “The data being presented at ESGCT show that a single infusion of avigbagene parvec enabled patients to remain off chronic therapy and maintain stable or improved clinical outcomes. These results highlight the potential of gene therapy to transform the care of Gaucher disease.”

The safety set presented at ESGCT included the 4 aforementioned patients and an additional 2 patients who were not advised to cease SOC therapy after receiving FLT201.² It was noted that all 6 patients had at least 1 adverse drug reaction (ADR) and that the most common FLT201-associated ADRs were increases in alanine transaminase (ALT) and fatigue. However, it was noted that even ALT increases within the normal range were considered ADRs because the trial protocol considered such increases an adverse event of special interest. Two patients had ALT increases above the normal range that were considered related to the gene therapy product, but both cases resolved. Furthermore, transient anti-glucocerebrosidase (GCase) antibodies appeared in 2 patients. In one of these patients, it was stated that the antibodies did not have an effect on efficacy. In the other patient, who remains on SOC, early GCase expression and lyso-Gb1 reduction were lost, which was deemed potentially related to anti-GCase antibodies and a COVID-19 infection that occurred in the month before gene therapy treatment. It was also reported that another patient had a detectable anti-AAVS3 titer at baseline and has remained on SOC.

“Avigbagene parvec was specifically designed to address the shortcomings of the existing SOC, with the aim of reducing both the disease and treatment burden for people with Gaucher,” Pamela Foulds, MD, the chief medical officer of Spur, added to the statement.² “These latest results build on the durability data we have previously reported, now showing favorable safety and efficacy for more than 2 years following a single low dose. As we prepare to move into the phase 3 trial, we see tremendous potential for avigbagene parvec to set a new standard of care with a onetime gene therapy.”

CGTLive® has previously spoken to GALILEO-1 investigator Reena Sharma, MD, an adult metabolic consultant at Salford Royal Hospital, about areas of interest for future study for FLT201.³ In the February 2025 interview, Sharma spoke about the need for clinicians to reconsider how they think about the unmet needs for patient communities in general and stated that she is looking forward to the phase 3 trial for FLT201.

“When you think about patients with disease like Pompe or even Fabry, their unmet needs with the current therapy are huge,” Sharma told CGTLive. “So we may think that, ‘Oh, [patients with diseases like Gaucher disease] are OK,’ but I think what we misunderstand and probably do not realize is that although their issues may not be as big as some of the other conditions we look after, they still mean a lot to this cohort of patients. They still have burden of therapy, which is a lifelong therapy. They still have unmet needs, their bone complications are ongoing, so I don't think as clinicians we should underestimate how it's impacting the patients, and we should always look at better therapies and explore better options.”

REFERENCES
1. Spur Therapeutics presents updated phase 1/2 data on its gene therapy candidate in Gaucher disease at ESGCT 32nd Annual Congress. News release. Spur Therapeutics. October 7, 2025. Accessed October 16, 2025. https://www.globenewswire.com/news-release/2025/10/07/3162226/0/en/Spur-Therapeutics-Presents-Updated-Phase-1-2-Data-on-Its-Gene-Therapy-Candidate-in-Gaucher-Disease-at-ESGCT-32nd-Annual-Congress.html
2. Foulds P, Yin P, Khinder J, et al. Long-term durability of FLT201: an investigational gene therapy for Gaucher disease type 1 encoding an engineered variant of the GCase enzyme. Presented at: European Society of Gene & Cell Therapy 32nd Annual Congress; October 7-10, 2025; Seville, Spain. P0979.
3. Sharma R, Goker-Alpan O, Schwartz I, Giraldo P, Ferrante F, Foulds P. Results from GALILEO-1, a first-in-human clinical trial of FLT201 AAV gene therapy in adult patients with Gaucher disease type 1. Poster presented at: WORLDSymposium; February 3-7, 2025; San Diego, CA. Poster 318.