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

NeurologyLive previews expected FDA decisions in neurology for 2026, highlighting late-stage clinical programs and regulatory milestones that could impact treatment practices. This coverage aims to align regulatory updates with expert insights on clinical trial data.