LAUSANNE, Switzerland, May 22, 2026
AC Immune announced new preliminary Phase 1 data showing that its investigational TDP-43 PET tracer ACI-19626 demonstrated higher brain uptake in patients with amyotrophic lateral sclerosis (ALS) compared with healthy controls. The findings were presented at the 2026 TDP43 Summit in Madison, Wisconsin, and further support the tracer’s potential to detect pathological TDP-43 protein accumulation in neurodegenerative diseases associated with TDP-43 proteinopathies.
ACI-19626 Detects TDP-43 Pathology in ALS Patients
According to the company, PET imaging with ACI-19626 showed significantly higher tracer uptake in key brain regions associated with ALS pathology, including the brain stem and precentral gyrus. These regions are known to accumulate abnormal TDP-43 protein deposits based on post-mortem neuropathology studies and clinical disease patterns. Previously reported Phase 1 findings also demonstrated elevated tracer uptake in disease-relevant cortical and subcortical regions in patients with genetically defined frontotemporal dementia (FTD), supporting the tracer’s broader potential across multiple neurodegenerative disorders.
Safety and Imaging Profile Support Further Development
AC Immune reported that ACI-19626 continues to demonstrate a favorable safety and tolerability profile in the ongoing first-in-human Phase 1 study. The tracer also showed rapid brain uptake and washout with dosimetry levels within accepted limits, indicating pharmacokinetic characteristics suitable for human brain imaging and potential pharmacodynamic analysis in future therapeutic studies targeting TDP-43 pathology. The company believes these findings strengthen the case for using ACI-19626 as a precision medicine biomarker capable of enabling earlier diagnosis and intervention.
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Expansion Study Ongoing Across Neurodegenerative Diseases
The ongoing Phase 1 study includes an expansion phase that may enroll up to 30 patients with frontotemporal dementia, ALS, or limbic-predominant age-related TDP-43 encephalopathy (LATE). AC Immune stated that the data generated so far underline the importance of reliable biomarkers for diseases involving TDP-43 pathology, including ALS, FTD, Alzheimer’s disease, and Parkinson’s disease, where overlapping symptoms often complicate diagnosis. The company believes ACI-19626 could become a critical tool for advancing precision diagnostics and therapeutic development in neurodegenerative medicine.
Source: AC Immune, press release
