Authors :
Presenting Author: Hila Ben-Moshe, PhD – Rafa's Moonshot
Ella Gordon, MD – Rafa's Moonshot
Sagi Gidali, BSc – Rafa's Moonshot
Noa Bielopolski, PhD – QR Genetics
Shane Wald‑Altman, PhD – QR Genetics
Trisha Brock, PhD – InVivo Biosystems
Bruria Ben‑Zeev⁴, MD – Sheba Tel-HaShomer Medical Center
Rationale:
STXBP1-related disorders (STXBP1-RD) are severe neurodevelopmental conditions characterised by early-onset epilepsy, motor impairment, and cognitive delay. Pathogenic variants in the STXBP1 gene disrupt the syntaxin-binding protein essential for synaptic vesicle fusion, compromising neuronal communication (Verhage et al., 2000). A recent review emphasised the utmost need for therapy focusing on this population (Goss et al., 2024). QR Genetics performed an in-silico docking and molecular-dynamics screen and prioritised compounds predicted to stabilise STXBP1. β-nicotinamide mononucleotide (NMN) was the top hit. NMN is a precursor of nicotinamide adenine dinucleotide (NAD⁺), which produces mitochondrial and synaptic benefits in neurodegeneration models (Hou et al., 2021) and is safe in an early human study (Yoshino et al., 2018). On this basis, we evaluated NMN as a potential therapy for STXBP1-RD.
Methods:
iPSC Neurons
STXBP1-R292C patient-derived iPSC neurons were treated with 3 mM NMN for 5 h. STXBP1 protein levels were quantified by Western blot vs. untreated controls.
C. elegans
Motor function in STXBP1-R292C homozygous C. elegans (InVivo Biosystems) was quantified by behavioral profiling and summarized using PCA.
N-of-1 Study
A 2-year-old with STXBP1-R292C began NMN (400 mg/kg/day) in August 2023. Vineland-3 was performed at baseline (age 2.0 y) and after 10 months (age 2.10 y). Follow-up is ongoing.
Results:
Western-blot analysis of R292C iPSC-patient derived neurons showed that 5h exposure to 3 mM NMN increased levels of STXBP1 compared with untreated cells. In the C. elegans STXBP1-R292C locomotion screen, worms were exposed to 4 mM NMN. Principal-component analysis of locomotion features showed that the NMN centroid lay closest to the untreated wild-type cluster, indicating the most complete phenotypic rescue among the ten compounds tested (Figure 1). The prospective N-of-1 study was conducted on a 2-year-old child with genetically confirmed STXBP1-RD (R292C). Vineland-3 reassessment 10 months of treatment demonstrated a clinically meaningful rise in the Motor domain from a standard score of 20 to 36, and a modest improvement in Communication from 51 to 55 (Figure 2). Taken together, these cellular, organismal and clinical results align to support an NMN–mediated restoration of STXBP1 function and associated motor performance.
Conclusions:
Consistent preliminary evidence from patient cell-based assays, C. elegans pharmacology, and a prospective N-of-1 clinical observation suggests that NMN upregulates STXBP1 protein expression and improves motor performance. These results provide initial proof-of-concept that NMN may be a promising therapeutic approach. Thorough pre-clinical studies and clinical trials are now required to confirm therapeutic efficacy, define optimal dosing and treatment windows, and elucidate the mechanism of action by which NMN might affect functional outcomes.Funding:
Supported by Rafa’s Moonshot, a non‑profit organization