Janssen, the drug research arm of Johnson & Johnson, has posted results on ClinicalTrials.gov, the US government’s public trial registry, for its stopped mid-stage trial of posdinemab in early Alzheimer’s disease12. Posdinemab, also known by the code JNJ-63733657, is a lab-made antibody aimed at tau, a protein that forms tangles inside the brains of people with Alzheimer’s3. The registry now lists the trial as terminated, with results first posted on November 5, 20261.
The posting follows a July 2026 report by the patient news site Being Patient, which said J&J stopped developing the drug because it failed to slow cognitive decline or halt the spread of tau in this trial4.
What the trial tested
The study, called AuTonomy, was a Phase 2 trial, a mid-stage test that checks whether a drug shows enough benefit to justify a larger study3. It was randomized and double-blind: people were assigned by chance to the drug or a placebo (a dummy drip), and neither they nor the study staff knew who got which1. It began on January 6, 2021, and enrolled 523 people1.
Participants received a low dose, a high dose or placebo through a drip into a vein every four weeks over a 104-week period, roughly two years3. The trial ran at 156 locations and could continue into a longer extension period in which people could choose to keep getting the drug3.
The main measure was the change in a score called the iADRS-MCI after 104 weeks1. This scale combines tests of memory and thinking with questions about how well a person handles daily life1. The registry lists the date the main data collection finished as October 17, 20251.
The idea behind the drug
According to J&J, posdinemab targets the middle section of a form of tau that carries extra chemical tags (phosphorylated tau) and is specific to Alzheimer’s2. The company said it was designed to bind this tau when it is released from nerve cells and neutralize it before it can “seed” or spread to another nerve cell2.
In a January 2025 press release, J&J said the antibody had shown promise in reducing tau seeding in lab and animal studies, and potential in targeting disease-linked tau in the spinal fluid of treated Alzheimer’s patients2. In that release the company also announced that the US Food and Drug Administration had given posdinemab Fast Track designation, a process meant to speed review of treatments for serious conditions with few options2. At the time, AuTonomy was fully enrolled and ongoing2.
“Posdinemab has the potential to slow the spread of tau pathology in the brain - which may slow cognitive decline.”
That was Bill Martin, head of neuroscience at Johnson & Johnson Innovative Medicine, speaking in the January 2025 release2.
What is known about the result, and what is not
The registry record confirms the basics: the trial was stopped, 523 people took part, and results have now been posted1. The material reviewed for this article does not include the result tables themselves. So Biohack cannot report here how the drug and placebo groups compared on the main score, how big any difference was, or what side effects were recorded.
The outcome described so far comes from Being Patient, which reported that the drug did not slow cognitive decline or stop tau from spreading4. That report does not give figures in the text available to Biohack4. It also does not explain, in the available text, why the approach fell short. Possible reasons, such as the dose, the stage of disease, or whether blocking tau outside nerve cells matters at all, remain open questions that the full posted data and any later journal paper may help answer.
Earlier, a trial-information site for patients said previous studies had found the drug generally safe and well tolerated in healthy people and in people with Alzheimer’s3. That statement predates the full AuTonomy safety data.
How patients were chosen
AuTonomy drew attention for how it found its patients. It was the first trial to use a blood test for a form of tau called p217tau as a first screening step, before a confirming tau PET scan, a type of brain scan that shows where tau has built up5. Findings presented at the 2024 CTAD Alzheimer’s conference showed that this two-step process cut the need for PET scans by nearly 49%, according to NeurologyLive5.
“One thing that’s really exciting about this study is that we’ve used this really new biomarker based approach.”
That was Fiona Elwood, who leads neurodegeneration research at Johnson & Johnson, speaking to Psychiatric Times in January 20256.
Screening was strict. Of 2,563 people screened, 2,040 (79.6%) did not qualify5. An analysis presented at the 2025 Alzheimer’s Association International Conference by Meyer, Henley, Bogert and colleagues found that screen failure was highest among Black or African American people, at 86.4% (51 of 59), compared with 80.5% among White people and 73.3% among Asian people5. The most common reason across all groups was not having a high enough level of p217tau in the blood5. The researchers noted that the small number of Black participants screened limits how far the finding can be generalized5.
Who is behind it
The trial was sponsored by Janssen Research & Development, LLC, a Johnson & Johnson company12. J&J describes posdinemab as discovered in-house2. Much of what is publicly known about the drug’s design and early promise comes from the company’s own statements, while the outcome report comes from Being Patient, an independent outlet24.
How it fits the field
Alzheimer’s is the most common form of dementia; J&J’s release put the number of people living with dementia worldwide at 55 million, with Alzheimer’s behind 60 to 80% of cases2. Drug development has been hard. A 2021 report from an international Alzheimer’s trials task force opened by noting that disappointing trial results “continue to mount” despite growing knowledge of the disease7. The task force listed anti-tau therapies among the approaches under study and concluded that shared “platform” trials, which test several treatments at once, are essential, including for combination treatments7.
Setbacks continue on other fronts too. On October 30, 2026, Psychiatric Times reported that a drug called sabirnetug missed its main memory goal in a mid-stage trial despite lowering amyloid, another protein that builds up in Alzheimer’s, and that its maker Acumen halted development6.
What to watch next
J&J has a second tau program. JNJ-2056, also called JNJ-64042056, is a vaccine-style treatment meant to prompt the body’s own immune system to make antibodies against disease-linked tau, developed with the company AC Immune2. Its Phase 2 trial, ReTain, is testing it in people who have tau in their brains but no memory or thinking problems yet2. The registry lists 55 people enrolled, no longer recruiting, with the main measure being change in brain tau seen on PET scans up to week 1028. Its main data collection is due to finish on December 22, 20268.
For posdinemab, the next things to look for are a close reading of the posted result tables, any presentation at a scientific meeting, and a peer-reviewed paper that explains what the drug did and did not change in the brain.
