iECURE, Inc., a clinical-stage genome editing company developing variant-agnostic, in vivo targeted gene insertion therapies for severe inherited neurometabolic disorders, today announced that data from the ongoing OTC-HOPE clinical trial evaluating ECUR-506 for neonatal-onset ornithine transcarbamylase (OTC) deficiency will be featured in an oral presentation at the Annual Symposium of the Society for the Study of Inborn Errors of Metabolism (SSIEM), taking place August 25-28, 2026, in Helsinki, Finland.

The presentation will include updated safety observations from the ongoing OTC-HOPE study, and genome editing data on measures of metabolic control from the low-dose cohort. Additional analyses will explore the relationship between baseline disease severity and clinical response.

Annual Symposium of the Society for the Study of Inborn Errors of Metabolism

Oral Presentation: Decreased rate of hyperammonemic crises in infants with neonatal-onset OTC deficiency post ECUR-506 administration (O-124)

• Session: Parallel abstract sessions E; E2: Urea cycle disorders
• Date/Time: Thursday, August 27, 3:30 – 5:00 p.m. EEST
• Location: Hall 5B
• Presenter: Julien Baruteau, M.D., Ph.D., University College London Great Ormond Street Institute of Child Health

iECURE will also be exhibiting at SSIEM at Booth B16, August 25-28, at the Messukeskus Helsinki Expo and Convention Centre, where members of the medical team will be available to discuss the OTC-HOPE study and the company's genome editing platform.

About OTC Deficiency

Ornithine transcarbamylase (OTC) deficiency is a rare, serious genetic disorder caused by a defect in a liver enzyme responsible for removing ammonia from the bloodstream. As a result, ammonia, a waste product generated when the body breaks down protein, accumulates in the blood (hyperammonemia) to levels that are toxic to the brain.

The disease is characterized by recurrent and often unpredictable hyperammonemic crises (HACs), which can lead to hospitalization, irreversible neurological injury, and death. Newborns with neonatal-onset OTC deficiency typically present shortly after birth with symptoms such as lethargy, poor feeding, and vomiting, which can rapidly progress to seizures, coma, and life-threatening complications if not promptly treated.

Current management includes a strict protein-restricted diet and ammonia scavenger medications, which must be taken multiple times daily and often throughout a patient’s life. While these approaches may help manage ammonia levels, they do not eliminate the risk of metabolic crises or ongoing disease burden, and patients remain vulnerable to acute decompensation and long-term complications.

About the OTC-HOPE Study

The OTC-HOPE study is a first-in-human clinical trial evaluating ECUR-506 in male infants with genetically confirmed neonatal-onset OTC deficiency. The trial is enrolling eligible male infants up to seven months of age at screening who are diagnosed with severe neonatal-onset OTC deficiency and meet study entry criteria. The primary objective is to assess the safety, tolerability and efficacy of intravenous administration of a single dose of ECUR-506. The study will also assess the pharmacokinetics of ECUR-506 administration and the potential effects of ECUR-506 on clinical outcome measures, disease-specific biologic markers, developmental milestones and quality of life. The main study includes screening, stabilization, dosing eligibility, study drug administration, and six-month follow-up, after which participants transition to a 14.5 year long term follow-up study (ECUR-LTFU). For more information, visit https://OTC-HOPE.com.

About ECUR-506

ECUR-506 is an investigational in vivo targeted gene insertion therapy designed to restore OTC enzyme activity by inserting a functional copy of the OTC gene into the well-characterized PCSK9 gene locus in liver cells. The therapy utilizes two adeno-associated virus (AAV) vectors using the same capsid, each carrying a distinct payload. One vector contains an ARCUS® nuclease designed to create an insertion site within the PCSK9 locus, while the second vector delivers a functional OTC gene for targeted insertion. iECURE has licensed the ARCUS® nuclease for ECUR-506 from Precision BioSciences (Nasdaq: DTIL).¹

About iECURE

iECURE is a clinical-stage genome editing company focused on developing therapies that utilize variant-agnostic in vivo targeted gene insertion to address severe genetic diseases with significant unmet need. The company’s approach is designed to restore the function of a missing or dysfunctional gene by inserting a functional copy into a patient’s genome, enabling durable gene expression and the potential for long-term therapeutic benefit. iECURE is advancing a pipeline of investigational therapies targeting inherited neurometabolic disorders, a group of rare genetic diseases that can lead to severe metabolic and neurological complications, including ornithine transcarbamylase (OTC) deficiency, citrullinemia type 1 (CTLN1), and phenylketonuria (PKU). For more information, visit https://iecure.com and follow on LinkedIn.

About Precision BioSciences & ARCUS®

Precision BioSciences, Inc. is a clinical stage gene editing company dedicated to improving life (Nasdaq: DTIL) with its novel and proprietary ARCUS® genome editing platform that is designed to differ from other technologies in the way it cuts, its smaller size, and its simpler structure. Key capabilities and differentiating characteristics may enable ARCUS nucleases to drive more intended, defined therapeutic outcomes. Using ARCUS, Precision’s pipeline is comprised of in vivo gene editing candidates designed to deliver lasting cures for the broadest range of genetic and infectious diseases, such as chronic hepatitis B where no adequate treatments exist. For more information about Precision BioSciences, visit www.precisionbiosciences.com.

[1] iECURE has licensed the ARCUS® nuclease from Precision BioSciences for four gene insertion programs including OTC, CTLN1 and PKU.

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