IDefine and UT Southwestern will assess a preclinical EHMT1 gene replacement strategy for Kleefstra syndrome. If the approach advances, future development would likely require a more detailed natural history framework, validated or fit-for-purpose clinical outcome measures, and careful selection of age groups most likely to benefit. In neurodevelopmental disorders, the timing of therapeutic intervention may be especially important because some neurologic features arise during early brain development. The collaboration also illustrates the growing role of patient advocacy organizations in de-risking early rare disease research. However, the clinical implications should be viewed cautiously until preclinical results are disclosed and reviewed. At present, the program establishes a research pathway for EHMT1 replacement rather than evidence of therapeutic benefit. IDefine and UT Southwestern announce research collaboration to advance gene therapy for rare disease Kleefstra syndrome. IDefine–The Kleefstra Syndrome Foundation and UT Southwestern Medical Center have entered a 2-year research collaboration to evaluate a preclinical EHMT1 gene replacement strategy for Kleefstra syndrome, a rare neurodevelopmental disorder with no appoved disease-modifying therapy.1 The program is expected to run through April 2028 and will be led by Steven Gray, PhD, professor at UT Southwestern and director of the UTSW Gene Therapy Program. “This landmark research collaboration represents a meaningful step forward in our mission to accelerate research that can lead to a first treatment fo FDA guidance for rare disease gene therapy development emphasizes that small populations, limited natural history data, and uncertainty about clinically meaningful end points can complicate preclinical-to-clinical translation.4

There are currently no approved treatments for the disease. "Advances in gene therapy and CNS-targeted delivery technologies are creating new opportunities to develop potential treatments for complex neurodevelopmental disorders like Kleefstra syndrome," said Dr. ATLANTA, June 3, 2026 /PRNewswire/ -- IDefine – The Kleefstra Syndrome Foundation, a leading patient advocacy organization, today announced a collaboration with UT Southwestern Medical Center to advance development of a potential gene therapy to treat Kleefstra syndrome (KS), a rare neurodevelopmental disorder caused by changes or loss of the EHMT1 gene, which plays a critical role in brain development and function. - Dr. Steven Gray will lead research effort focused on potential therapy to replace the EHMT1 gene in patients with rare neurodevelopmental disorder View original content:https://www.prnewswire.com/news-releases/idefine-and-ut-southwestern-announce-research-collaboration-to-advance-gene-therapy-for-rare-disease-kleefstra-syndrome-302789121.html The two-year research program, led by Steven Gray, PhD, professor at UT Southwestern and director of the UTSW Gene Therapy Program, will evaluate the feasibility and safety of EHMT1 gene replacement therapy using next-generation gene delivery technology designed to target the central nervous system (CNS). "This landmark research collaboration represents a meaningful step forward in our mission to accelerate research that can lead to a first treatment for Kleefstra syndrome," said Eric Scheeff, PhD, chief scientific officer of IDefine. "We are especially honored to support and partner with Dr. Steven Gray and the UT Southwestern Gene Therapy Program in this effort.

/PRNewswire/ -- IDefine – The Kleefstra Syndrome Foundation, a leading patient advocacy organization, today announced a collaboration with UT Southwestern... ATLANTA, June 3, 2026 /PRNewswire/ -- IDefine – The Kleefstra Syndrome Foundation, a leading patient advocacy organization, today announced a collaboration with UT Southwestern Medical Center to advance development of a potential gene therapy to treat Kleefstra syndrome (KS), a rare neurodevelopmental disorder caused by changes or loss of the EHMT1 gene, which plays a critical role in brain development and function. There are currently no approved treatments for the disease. "Advances in gene therapy and CNS-targeted delivery technologies are creating new opportunities to develop potential treatments for complex neurodevelopmental disorders like Kleefstra syndrome," said Dr. - Dr. Steven Gray will lead research effort focused on potential therapy to replace the EHMT1 gene in patients with rare neurodevelopmental disorder The two-year research program, led by Steven Gray, PhD, professor at UT Southwestern and director of the UTSW Gene Therapy Program, will evaluate the feasibility and safety of EHMT1 gene replacement therapy using next-generation gene delivery technology designed to target the central nervous system (CNS). "This landmark research collaboration represents a meaningful step forward in our mission to accelerate research that can lead to a first treatment for Kleefstra syndrome," said Eric Scheeff, PhD, chief scientific officer of IDefine. "We are especially honored to support and partner with Dr. Steven Gray and the UT Southwestern Gene Therapy Program in this effort.