AC Immune Achieves First In Vivo Imaging of TDP-43 Brain Pathology with Novel PET Tracer ACI-19626
Key Insights
AC Immune presented groundbreaking Phase 1 data showing the first in vivo images of TDP-43 pathology in human brains using their novel PET tracer ACI-19626 at the AD/PD 2026 conference.
The tracer demonstrated significantly higher uptake in key brain regions of patients with genetically defined frontotemporal dementia (search) compared to healthy subjects, with good safety and tolerability profiles.
ACI-19626 has potential to enable precision medicine approaches across multiple neurodegenerative diseases including FTD, ALS, and LATE by providing reliable biomarkers for differential diagnosis.
AC Immune SA announced the presentation of Phase 1 data including the first in vivo images of TDP-43 pathology in the human brain, detected using its first-in-class positron emission tomography (PET) tracer ACI-19626, at the International Conference on Alzheimer's and Parkinson's Disease (search) (AD/PD™ 2026). The clinical-stage biopharmaceutical company's breakthrough represents a significant advancement in neurodegenerative disease diagnosis and precision medicine.
Significant Tracer Uptake in FTD Patients
Initial data from the Phase 1 trial support ACI-19626's potential to detect pathological TDP-43 in the brains of patients with TDP-43 proteinopathies. PET scans with ACI-19626 showed that tracer uptake was significantly higher in key regions of the brain in patients with frontotemporal dementia (search) (FTD) due to mutated C9orf72 than in the brains of healthy subjects.
The regions with higher tracer uptake included subcortical and cortical regions of the brain where TDP-43 pathology is expected based on post-mortem neuropathology studies. ACI-19626 demonstrated good safety and tolerability, a dosimetry profile within accepted limits, and rapid brain uptake and washout, indicating a pharmacokinetic (PK) profile suitable for human brain imaging and potentially pharmacodynamic analysis of therapeutics targeting TDP-43 pathology.
Precision Medicine Implications
Dr. Andrea Pfeifer, CEO of AC Immune SA, commented: "These first-in-human data presented at AD/PD™ are very encouraging and indicate that ACI-19626 could have an important role in early diagnosis of multiple neurogenerative diseases, with a clear path to precision medicine. This underlines the potential of the AC Immune pipeline, based on our SupraAntigen® and Morphomer® technology platforms, for precision prevention of multiple conditions, encompassing diagnostics, active immunotherapies and small molecules for intracellular targeting."
Addressing Diagnostic Challenges
TDP-43 is the main component in inclusions found in the brains of people with FTD, amyotrophic lateral sclerosis (search) (ALS) and limbic-predominant age-related TDP-43 encephalopathy (search) (LATE), as well as a co-pathology in Alzheimer's disease (search) (AD) and Parkinson's disease (search) (PD). These conditions share many of the same clinical signs and symptoms, making differential diagnosis a difficult and lengthy process in the absence of reliable biomarkers.
Trial Design and Future Plans
The Phase 1, first-in-human trial (Clinicaltrials.gov: NCT06891716) is conducted in two parts. Part 1 is investigating ACI-19626 in healthy volunteers and patients with genetic FTD and is expected to be completed in H1 2026. The Part 2 expansion may include up to 30 patients with FTD, ALS or LATE. Exploration of ACI-19626 binding in additional patient populations including ALS is ongoing.
Pfeifer added: "We are looking forward to final data from Part 1 of this study, expected in H1 2026, and have started Part 2 in other patient populations to further define its potential role in this new treatment paradigm."