Spinogenix’s Fragile X Syndrome (FXS) drug is the first to show rescued well-established resting EEG abnormalities, suggesting a normalisation of brain function.
The Phase IIa trial (NCT06413537), conducted at Cincinnati Children’s Hospital, enrolled 10 adult male patients with genetically confirmed FXS. The patients received a single 800mg dose of SPG601 and a placebo separated by a one-week washout period.
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Data from the trial, published in Nature Scientific Reports, showed significant treatment effects in gamma1 power, alpha2 power, and theta power. This suggests that restoring synaptic function may offer a new approach to addressing the cognitive and neurophysiological deficits associated with FXS.
In the study, SPG601 was well-tolerated with a favourable safety profile.
Dr Stella Sarraf, CEO and founder at Spinogenix, said: “This latest milestone, together with continued support from the industry-leading FRAXA Research Foundation on this mechanism of action, provides a strong foundation as we advance this drug into a Phase IIb/III trial. With no therapies currently FDA approved for people living with this condition, we are committed to leading the path by furthering the development of SPG601 to help people and their families who have been searching for new treatments.”
SPG601 is a first-in-class, small-molecule oral tablet designed to modulate the activity of large-conductance, calcium-activated potassium channels to correct specific synaptic dysfunctions that underlie many core symptoms of FXS.
Spinogenix said this is the first time an FXS treatment demonstrated improvement across the EEG power spectrum, including a reduction in excessive high-frequency gamma band activity and an increase in alpha band power that is reduced at baseline.
These corrected EEG deficits show a normalisation of brain function in the direction of normal activity levels required for learning and memory.
FXS market remains barren
SPG601 has received Fast Track Designation and Orphan Drug Designation by the US Food and Drug Administration (FDA), as well as Orphan Disease Designation by the European Medicines Agency (EMA). In September 2025, the company received positive feedback from the FDA to advance the drug to registrational trials.
According to the US Centers for Disease Control and Prevention (CDC), it is estimated that one in every 7,000 males have FXS compared to one in every 11,000 females. There are no FDA-approved treatments for the inherited genetic disorder that causes physical abnormalities, behavioural issues and a wide range of other health problems.
According to GlobalData, the FXS market in the US and Germany combined for 2025 was valued at $28.7m, but is projected to grow at a compound annual growth rate (CAGR) of 14.7% between 2020 and 2030, reaching $111.9m by 2030.
There are, however, several barriers to the market’s growth. This includes the high anticipated annual cost of therapy, clinical heterogeneity in Fragile X and caution of public markets and investors to therapies including cannabidiols, on which some FXS therapies are based.
GlobalData had predicted Harmony Biosciences’ Zygel, a cannabis-based therapy, to be a key driver of growth at the time of the report in February 2025. However, in September 2025, Harmony announced the drug failed to meet its primary endpoint in a Phase III trial. Shionogi’s zatolmilast is also anticipated to be a key driver in the FXS market.
GlobalData is the parent company of Clinical Trials Arena.
