AC Immune Presents First In vivo Images of Brain TDP-43 Pathology from Phase 1 Trial of PET tracer ACI-19626, at AD/PDTM 2026
Rhea-AI Summary
AC Immune (NASDAQ: ACIU) presented Phase 1 data March 19, 2026 showing the first in vivo PET images of TDP-43 brain pathology using tracer ACI-19626. Initial scans showed significantly higher tracer uptake in key cortical and subcortical regions of C9orf72 genetic FTD patients versus healthy subjects.
ACI-19626 demonstrated good safety, acceptable dosimetry, and a PK profile with rapid brain uptake and washout. Part 1 final data expected H1 2026; Part 2 expansion is underway to study additional patient populations including ALS and LATE.
Positive
- First in vivo TDP-43 images detected in human brain
- Significantly higher ACI-19626 uptake in C9orf72 FTD patients versus healthy subjects
- Good safety and tolerability reported in Phase 1 initial data
- PK profile suitable for human brain imaging and pharmacodynamic analysis
- Part 2 expansion started to evaluate additional populations including ALS and LATE
Negative
- Early-stage data: findings are initial Phase 1 results and not yet definitive
- Final Part 1 data pending H1 2026, limiting current clinical certainty
News Market Reaction – ACIU
In the Mar 19 session, ACIU declined 4.53%, reflecting a moderate negative market reaction. Argus tracked a trough of -4.5% from its starting point during tracking.
Data tracked by StockTitan Argus on the day of publication.
Key Figures
Previous Clinical trial Reports
| Date | Event | Sentiment | 24h Move | Catalyst |
|---|---|---|---|---|
| Feb 24 | Phase 1 initiation | Positive | +7.5% | First-in-human Phase 1 trial of NLRP3 inhibitor ACI-19764 began. |
| Dec 11 | Phase 2 interim data | Positive | +15.4% | Positive interim Phase 2 VacSYn data for ACI-7104.056 in Parkinson’s. |
| Apr 02 | Phase 2 interim data | Positive | +4.7% | Further positive interim Phase 2 results for ACI-7104.056 in Parkinson’s. |
| Dec 10 | Phase 1b/2 safety data | Positive | +0.0% | Interim safety data from ABATE trial of ACI-24.060 in Down syndrome. |
| Nov 14 | Phase 2 interim data | Positive | +13.4% | Positive interim Phase 2 results for ACI-7104.056 in early Parkinson’s. |
24h Move is the share-price change in the day after each event; other market factors may also have contributed.
Clinical trial updates have typically been well-received, with an average +8.22% move across recent clinical news and no negative reactions reported.
Over the past year, AC Immune has repeatedly reported encouraging clinical data across its neurodegenerative pipeline. Positive interim Phase 2 results for ACI‑7104.056 in Parkinson’s disease and interim safety data for ACI‑24.060 in Down syndrome showed favorable efficacy and safety signals. The company also advanced ACI‑19764 into Phase 1, reinforcing a diversified clinical portfolio. Today’s Phase 1 TDP‑43 PET‑tracer data for ACI‑19626 adds another biomarker-driven asset, consistent with prior strategy emphasizing precision diagnostics and immunotherapies across multiple neurodegenerative indications.
Key Terms
tdp-43 medical
positron emission tomography (pet) medical
frontotemporal dementia medical
amyotrophic lateral sclerosis medical
pharmacokinetic (pk) medical
dosimetry medical
clinicaltrials.gov regulatory
AI-generated analysis. How Rhea-AI works. Not financial advice.
AC Immune Presents First In vivo Images of Brain TDP-43 Pathology from Phase 1 Trial of PET tracer ACI-19626, at AD/PDTM 2026
- Initial data indicates significantly higher tracer uptake in patients with genetically defined FTD
- Good safety and tolerability and suitable PK profile for human brain imaging
- Potentially enables precision medicine across multiple neurodegenerative diseases
Lausanne, Switzerland, March 19, 2026 -- AC Immune SA (NASDAQ: ACIU), a clinical-stage biopharmaceutical company pioneering precision therapeutics for neurodegenerative diseases, today 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 (AD/PD™ 2026).
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, enabling a precision medicine approach to multiple neurodegenerative diseases.
Specifically, PET scans with ACI-19626 showed that tracer uptake was significantly higher in key regions of the brain in patients with frontotemporal dementia (FTD) due to mutated C9orf72 than in the brains of healthy subjects. As presented, 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 showed 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.
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. 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.”
TDP-43 is the main component in inclusions found in the brains of people with FTD, amyotrophic lateral sclerosis (ALS) and limbic-predominant age-related TDP-43 encephalopathy (LATE), as well as a co-pathology in Alzheimer’s disease (AD) and Parkinson’s disease (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.
The Phase 1, first-in-human trial (Clinicaltrials.gov: NCT06891716) is 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.
About AC Immune SA
AC Immune SA is a clinical-stage biopharmaceutical company and a global leader in precision prevention for neurodegenerative diseases, including Alzheimer’s disease, Parkinson’s disease, and NeuroOrphan indications driven by misfolded proteins. The Company’s two clinically validated technology platforms, SupraAntigen® and Morphomer®, fuel its pipeline of first- and best-in-class assets, which currently features a range of therapeutic and diagnostic programs, including candidates in Phase 2 and Phase 3 development. AC Immune has a strong track record of securing strategic partnerships with leading global pharmaceutical companies, resulting in substantial non-dilutive funding to advance its proprietary programs and >
SupraAntigen® is a registered trademark of AC Immune SA in the following territories: AU, EU, CH, GB, JP, RU, SG and USA. Morphomer® is a registered trademark of AC Immune SA in CA, CN, CH, EU, GB, JP, KR, NO, RU and SG.
The information on our website and any other websites referenced herein is expressly not incorporated by reference into, and does not constitute a part of, this press release.
For further information, please contact:
| SVP, Investor Relations & Corporate Communications Gary Waanders, Ph.D., MBA AC Immune Phone: +41 21 345 91 91 Email: gary.waanders@acimmune.com | |
| International Media Chris Maggos Cohesion Bureau Phone: +41 79 367 6254 Email: chris.maggos@cohesionbureau.com |
Forward looking statements
This press release contains statements that constitute “forward-looking statements” within the meaning of Section 27A of the Securities Act of 1933 and Section 21E of the Securities Exchange Act of 1934. Forward-looking statements are statements other than historical fact and may include statements that address future operating, financial or business performance or AC Immune’s strategies or expectations. In some cases, you can identify these statements by forward-looking words such as “may,” “might,” “will,” “should,” “expects,” “plans,” “anticipates,” “believes,” “estimates,” “predicts,” “projects,” “potential,” “outlook” or “continue,” and other comparable terminology. Forward-looking statements are based on management’s current expectations and beliefs and involve significant risks and uncertainties that could cause actual results, developments and business decisions to differ materially from those contemplated by these statements. These risks and uncertainties include those described under the captions “Item 3. Key Information – Risk Factors” and “Item 5. Operating and Financial Review and Prospects” in AC Immune’s Annual Report on Form 20-F and other filings with the Securities and Exchange Commission. Forward-looking statements speak only as of the date they are made, and AC Immune does not undertake any obligation to update them in light of new information, future developments or otherwise, except as may be required under applicable law. All forward-looking statements are qualified in their entirety by this cautionary statement.
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