Jack's Tomorrow, in Partnership with The Jackson Laboratory, Pioneers Safety Roadmap for PURA Syndrome Gene Therapy
New research framework brings families closer to a treatment for a rare genetic condition affecting children worldwide
[Boston, Massachusetts, May 12, 2026] – Jack's Tomorrow, a patient advocacy organization dedicated to finding a treatment for PURA Syndrome, has taken a leading role in advancing gene therapy for the rare genetic condition — funding and directing research that tackles a critical question: how much of the PURA protein can be safely expressed? To find out, Jack's Tomorrow worked with scientists at The Jackson Laboratory’s (JAX) Rare Disease Translational Center to establish a practical safety framework for gene therapy dosing in PURA Syndrome. The findings are being presented today at the 2026 American Society of Gene & Cell Therapy (ASGCT) Annual Meeting in Boston.
“Gene overexpression studies like these are vital for advancing gene therapies from the laboratory to clinical trials,” said Matthew Simon, Ph.D., Senior Study Director, JAX Rare Disease Translational Center. “This work validates genes as safe and appropriate targets for biological therapies and can help guide dosing.”
PURA Syndrome
PURA Syndrome is a neurogenetic disorder caused by mutations in the PURA gene. The condition, which was first identified in 2014, can lead to moderate-to-severe developmental delays, low muscle tone (known as hypotonia), seizures (epilepsy), and other health challenges. Approximately 840 people across 67 countries have been diagnosed with PURA syndrome with case numbers expected to grow as access to genetic testing increases. There is currently no approved treatment or cure.
The syndrome is characterized as a haploinsufficiency disorder where one copy of a gene is deleted or inactivated, and the single remaining, functional gene copy does not produce enough protein to maintain normal body function. Gene therapy to amplify PURA protein levels in individuals with the syndrome has emerged as a plausible, promising therapeutic approach, but until now, the safety of PURA gene overexpression had not been well-understood.
To address that question, Jack’s Tomorrow funded a controlled gene overexpression research program designed to evaluate how much PURA genetic protein can be safely increased in living systems. To test the program, JAX scientists employed an advanced gene delivery platform based on a viral delivery of a human PURA gene to adult wild-type mice. The capsid was specifically designed to deliver to the central nervous system—a critical target for addressing the neurological symptoms of PURA Syndrome
Research Findings
The study was conducted in two phases. In the first, scientists tested higher dose ranges and conducted interim analyses to detect early signs of dose-related sensitivity, refining their approach along the way. In the second phase, the team expanded to lower dose levels and extended observation periods to assess long-term tolerability and whether any effects persisted over time. Mice were closely monitored for clinical symptoms throughout, and detailed analyses were performed on key organs — including the brain, spinal cord, and liver — to evaluate both safety and neurological relevance.
The research defined preliminary tolerated dose ranges in healthy mice. More broadly, the work established a practical, reproducible framework for studying the effects of increasing PURA expression in the body.
“This research represents a crucial step forward in helping people living with PURA Syndrome and their families,” said Andrew Steinsapir, M.B.A., Director and Gene Therapy Program Lead at Deerfield Discovery and Development and a member of Jack’s Tomorrow’s Scientific Advisory Board. “By proactively addressing dose sensitivity, we can reduce uncertainty as we move forward with developing treatments for PURA Syndrome.”
The poster (#1489), “Patient Advocacy Group-Led Preclinical Strategy to Assess PURA Dosage Sensitivity in Support of Gene Therapy Development,” will be presented today at the ASGCT Annual Meeting from 5:00-6:30 p.m. ET.
“This study highlights the growing impact of patient-directed research models in accelerating progress for rare diseases,” said Kyle Czepiel, Co-founder, Jack’s Tomorrow. “By funding and guiding early translational studies, advocacy organizations like Jack’s Tomorrow are helping to bridge the gaps between basic science and clinical development.”
The new findings build upon earlier research in which JAX scientists, in collaboration with Jack’s Tomorrow, developed mouse models resembling how PURA Syndrome presents in people and another model that can be used to study PURA gene knockouts in specific organs and tissues. Both mouse models are available to researchers through on “Tools for Researchers portal” on or through the JAX Website.
PURA Syndrome research is gaining momentum, as evidenced by several posters at ASGCT’s Annual Meeting:
Molecular mechanisms of PURA-associated neurodevelopmental disorder in a Pura mouse model – Dr. Yong-Hui Jiang's lab, Yale School of Medicine (#3450)
Targeted therapies for neurodevelopmental disorders with combined haploinsufficiency and dominant-negative mechanism – Dr. Benjamin Cocanougher, Cincinnati Children's (#3381)
Characterization of human iPSC-derived neuronal models of PURA Syndrome to elucidate mechanisms and enable therapeutic screening – Celena Lozano, PURA Syndrome Foundation Board Member and PhD candidate, Dr. Kyle Fink's lab, UC Davis Health (#1515)
About Jack’s Tomorrow
Jack's Tomorrow is a patient advocacy organization whose mission is to fund research toward a treatment—and ultimately a cure — for PURA Syndrome.
About JAX
JAX is an independent, nonprofit biomedical research institution with nearly 3,000 employees in locations across the United States, Japan and China. Its mission is to discover precise genomic solutions for disease and empower the global biomedical community in the shared quest to improve human health. The Rare Disease Translational Center serves that mission by empowering rare disease solutions through partnership, innovation, and scaled pre-clinical pipelines to deliver targeted therapies from lab to clinic swiftly and effectively. The Center aims to provide patients with an efficient path from diagnosis to therapy, allowing them to live longer, healthier lives. For more information, please visit www.jax.org/rare.
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