TAP-GRIN: L‑serine for GRIN-related neurodevelopmental disorders

Is this trial a fit for you?

A plain-English reading of the study's rules. Only the study team can confirm whether you qualify.

What this trial studies

This is a randomized, double-blind, placebo-controlled series of aggregated n-of-1 trials testing oral L‑serine versus placebo in participants aged 2–30 with pathogenic or likely pathogenic loss-of-function variants in GRIN1, GRIN2A, GRIN2B, or GRIN2D. The primary clinical outcome is change in overall status measured by the Clinical Global Impression‑Severity (CGI‑S) score, with secondary outcomes including behavior, cognition, adaptive and motor function, sleep, seizure frequency and EEG findings. The trial also monitors safety and tolerability and will explore neurophysiological biomarkers such as TMS‑EMG and TMS‑EEG for treatment response. Each participant serves as their own control through alternating treatment and placebo periods, allowing within-person comparisons despite the rarity and heterogeneity of the condition.

Why it matters

Who can join: the full rules

Inclusion Criteria:

* Clinical diagnosis of a GRIN-related neurodevelopmental disorder (GRIN-NDD)
* Presence of a pathogenic or likely pathogenic loss-of-function (LoF) variant in GRIN1, GRIN2A, GRIN2B, or GRIN2D
* Parent(s), caregiver(s), or legally authorised representative(s) have been informed of the nature of the study and have provided written informed consent.
* Participants who are able to do so have provided written informed consent or assent, according to local regulations and cognitive capacity.
* Parent(s)/caregiver(s) are willing and able to comply with study procedures and visits, in the opinion of the investigator.
* Participants who have previously received L-serine supplementation are willing to discontinue L-serine for at least one week prior to the baseline observation period.

Exclusion Criteria:

* Age younger than 2 years at screening.
* Known hypersensitivity or intolerance to L-serine, placebo, or any excipients used in the study formulations.
* Presence of a clinically significant unstable medical condition (other than epilepsy) that, in the investigator's judgement, may place the participant at increased risk or interfere with study participation.
* Any other significant disease or disorder that may compromise participant safety, affect study outcomes, or impair the participant's ability to complete the study procedures.
* Inadequate supervision by parent(s) or caregiver(s), as judged by the investigator.
* Participation in another clinical trial involving an investigational medicinal product within the previous 6 months.
* Female participants who are pregnant or breastfeeding.
* Presence of a GRIN1, GRIN2A, GRIN2B, or GRIN2D variant for which a clear loss-of-function effect cannot be demonstrated.

Where it's running

• Meyer Children's Hospital
  Florence, Italy Recruiting
• Children's Memorial Health Institute
  Warsaw, Poland Recruiting
• Hospices Civils de Lyon
  Lyon, France Not yet recruiting

Study contacts

• Study coordinator: Simona Balestrini, Md, PhD
• Email: simona.balestrini@meyer.it
• Phone: 00390555662719

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How to take part

1. Review the eligibility criteria above with your treating physician.
2. Check the official listing on ClinicalTrials.gov for the latest contact details and recruitment status.
3. Contact the study coordinator or principal investigator to ask for pre-screening. Pre-screening is free and never obligates you to enroll.