Spinogenix announced positive feedback from a Type C meeting with the FDA on SPG601, its first-in-class oral therapy for Fragile X syndrome (FXS), following Phase IIa trial (NCT06413537) results showing improvements in neurophysiological activity and cognitive function.

According to the company, the meeting provided clear guidance on the design of future registrational trials and reinforced the path forward for advancing SPG601 toward potential approval for this underserved patient population.¹

How Will Spinogenix Advance SPG601 in Fragile X Syndrome Following FDA Guidance?

"We are pleased with the positive feedback we received from the FDA regarding SPG601 in FXS patients,” said Stella Sarraf, CEO, founder, Spinogenix, in a press release. “There are currently no FDA approved treatments for this condition and SPG601 represents a first-in-class oral drug targeting BK channels, indicating promise for a new mechanism to address this significant unmet need. We are excited to continue our journey to develop a treatment for this rare and debilitating genetic disorder, which not only impacts individuals but entire families, economically and emotionally"

Phase IIa Trial Design and Endpoints

• The randomized, double-blind, placebo-controlled crossover study evaluated the safety, efficacy, tolerability, pharmacokinetics, and pharmacodynamics of SPG601 in 10 adult men with FXS over two in-person clinic visits, during which participants received either SPG601 or placebo before crossing over to the alternate treatment.
• The primary endpoint of the trial was the reduction of high-frequency gamma band activity as assessed by electroencephalography.
• Key secondary endpoints included change in attention and inhibition symptoms, change in cognitive outcomes measured by National Institutes of Health (NIH) Toolbox, change in eye tracking for social gaze, safety, and tolerability.
• Results showed that the trial met its primary endpoint.
• SPG601 treatment led to notable improvements compared with placebo on the Flanker task, part of the NIH Toolbox used in Fragile X syndrome trials to assess selective attention and inhibitory control—areas in which individuals with FXS typically experience substantial deficits.^1,2

FDA Type C Meeting Guidance and Next Steps

Spinogenix stated that the Type C meeting with the FDA offered clear guidance for designing a registrational trial to evaluate the safety and efficacy of SPG601 in FXS patients. Key elements such as trial duration, patient population, and primary and secondary endpoints were agreed upon, and the planned Phase IIb adaptive design will enable a smooth progression into Phase III.¹

• According to the Centers for Disease Control and Prevention, it is estimated that one in every 7,000 males have FXS compared to one in every 11,000 females.
• Symptoms usually begin to manifest at one year of age for males and 16 months of age for females.
• However, the average age of diagnosis is between 35 and 37 months for males and 42 months for females.³

"The results of our Phase IIa trial of SPG601 in FXS participants are particularly encouraging in light of the safety and tolerability data indicating no sedation or clinical impairment and the unprecedented effects observed on neurophysiology measures of gamma band activity and clinical outcome measures of attention and inhibitory control" shared Dr. Craig Erickson, Spinogenix chief medical advisor and director of the Cincinnati Fragile X Research and Treatment Center. "The FDA's feedback advances our preparation for upcoming clinical trials and allows us to continue accelerating development of a much-needed therapy in the hope of addressing an underserved community"

References

1. Spinogenix Announces Positive Type C Meeting with the FDA for SPG601 in Patients with Fragile X Syndrome (FXS). PR Newswire. September 2, 2025. Accessed September 5, 2025. https://www.prnewswire.com/news-releases/spinogenix-announces-positive-type-c-meeting-with-the-fda-for-spg601-in-patients-with-fragile-x-syndrome-fxs-302543653.html
2. Study of SPG601 in Adult Men With Fragile X Syndrome. Clinicaltrials.gov. Accessed September 5, 2025. https://clinicaltrials.gov/study/NCT06413537?term=NCT06413537&rank=1
3. Data and Statistics on Fragile X Syndrome. CDC. Accessed September 5, 2025. https://www.cdc.gov/fragile-x-syndrome/data/index.html