iECURE, a private clinical-stage genome editing company, reported preliminary safety observations from all nine participants dosed with ECUR-506 across the low-, intermediate- and high-dose cohorts, saying the therapy was generally well tolerated as of the July 28, 2026 data cutoff, with no unexpected treatment-related safety events, no cases of thrombotic microangiopathy and no infusion reactions. Asymptomatic, non-dose-dependent, transient Grade 2-3 transaminitis resolved with reactive immunosuppression in seven of eight participants, while one participant received prophylactic corticosteroids per protocol. One participant died following hypoxemic respiratory failure, which the company said was determined to be unrelated to ECUR-506 and attributable to underlying OTC deficiency disease progression and resulting complications. ECUR-506 uses an ARCUS nuclease licensed from Precision BioSciences (NASDAQ:DTIL), which iECURE has licensed for four gene insertion programs including OTC, CTLN1 and PKU.