Abstract GRIN-related disorders are rare developmental encephalopathies with variable manifestations and limited therapeutic options. Here, we present the first non-randomized, open-label, single-arm trial (NCT04646447) designed to evaluate the tolerability and efficacy of L-serine in children with GRIN genetic variants leading to loss-of-function. In this phase 2A trial, patients aged 2–18 years with GRIN loss-of-function pathogenic variants received L-serine for 52 weeks. Primary end points included safety and efficacy by measuring changes in the Vineland Adaptive Behavior Scales, Bayley Scales, age-appropriate Wechsler Scales, Gross Motor Function-88, Sleep Disturbance Scale for Children, Pediatric Quality of Life Inventory, Child Behavior Checklist and the Caregiver-Teacher Report Form following 12 months of treatment. Secondary outcomes included seizure frequency and intensity reduction and EEG improvement. Assessments were performed 3 months and 1 day before starting treatment and 1, 3, 6 and 12 months after beginning the supplement. Twenty-four participants were enrolled (13 males/11 females, mean age 9.8 years, SD 4.8), 23 of whom completed the study. Patients had GRIN2B, GRIN1 and GRIN2A variants (12, 6 and 5 cases, respectively). Their clinical phenotypes showed 91% had intellectual disability (61% severe), 83% had behavioural problems, 78% had movement disorders and 58% had epilepsy. Based on the Vineland Adaptive Behavior Composite standard scores, nine children were classified as mildly impaired (cut-off score > 55), whereas 14 were assigned to the clinically severe group. An improvement was detected in the Daily Living Skills domain (P = 0035) from the Vineland Scales within the mild group. Expressive (P = 0.005), Personal (P = 0.003), Community (P = 0.009), Interpersonal (P = 0.005) and Fine Motor (P = 0.031) subdomains improved for the whole cohort, although improvement was mostly found in the mild group. The Growth Scale Values in the Cognitive subdomain of the Bayley-III Scale showed a significant improvement in the severe group (P = 0.016), with a mean increase of 21.6 points. L-serine treatment was associated with significant improvement in the median Gross Motor Function-88 total score (P = 0.002) and the mean Pediatric Quality of Life total score (P = 0.00068), regardless of severity. L-serine normalized the EEG pattern in five children and the frequency of seizures in one clinically affected child. One patient discontinued treatment due to irritability and insomnia. The trial provides evidence that L-serine is a safe treatment for children with GRIN loss-of-function variants, having the potential to improve adaptive behaviour, motor function and quality of life, with a better response to the treatment in mild phenotypes.
ZusammenfassungBlutdruckvariabilität ist Scit langem Gegenstand intensiver Studien (9, 13), obwohl ihre klinische Bedeutung bislang noch nicht vollständig definiert werden konnte (8, 11). Es wurde gezeigt, daß physische Aktivität eine der wichtigsten Determinanten für Blutdruckschwankungen ist (6). Die von isotonischen und isometrischen Übungen verursachten Blutdruckschwankungen wurden in Labortests umfangreichen Untersuchungen unterworfen. Die alltäglichen physischen und sportlichen Aktivitäten unterscheiden sich in vielerlei Hinsicht von den Belastungstests, so daß ein direkter Vergleich nicht vorgenommen werden kann (12). Im Unterschied zu den Labortests sind bei den erstgenannten Aktivitäten die dynamischen und statischen Komponenten nicht klar zu trennen. Trotz dieser Einschränkungen basieren die derzeitigen Kenntnisse über die Blutdruckvariabilität bei sportlichen Aktivitäten ausschließlich auf den Resultaten von Belastungstests, was auf die Unmöglichkeit zurückzuführen ist, den Blutdruck während der sportlichen Aktivitäten zu messen.
Blood pressure variability has long been a subject of intense interest [1, 2] even though its clinical significance has not been completely established [3, 4]. Physical activity has been shown to represent one of the predominant determinants of blood pressure variability [5] and the blood pressure changes determined by both isotonic and isometric exercise have been studied extensively by means of laboratory tests. Everyday physical activities, as well as sports activities, differ in many respects from stress testing, however, so that a direct comparison cannot be made [6]. In fact, during such activities the dynamic and the static components of the exercise are not as clearly separated as in laboratory tests, but there is a parallel, though different, contribution of each one of them.