A New Alzheimer's Drug Targets Tau and Sully Sullenberger Has the Disease

A Different Kind of Attack on Alzheimer's

At the Alzheimer's Association International Conference on Tuesday, July 15, Biogen presented the complete clinical, biomarker, and safety dataset from its Phase 2 CELIA study of diranersen — and for the first time in randomized human research, a tau-targeting therapy simultaneously produced both robust reductions in brain tangles and measurable slowing of cognitive decline. It is a milestone that researchers have been chasing for years, and it arrives at a moment when the disease is claiming some of the most recognizable names in public life.

The trial is the first to show that lowering tau — a protein closely linked with brain cell death and cognitive decline — can slow progression of Alzheimer's. That distinction matters enormously. Alzheimer's disease is defined by two protein accumulations: amyloid-beta plaques forming between neurons, and tau tangles forming inside them. The approved treatments — lecanemab and donanemab — target amyloid by clearing plaques from the extracellular space. Diranersen goes after the other half of the equation entirely.

How Diranersen Works — and What the Numbers Show

Instead of removing toxic forms of tau with an antibody, an approach used by prior failed drugs, diranersen silences a gene responsible for producing all forms of tau. Diranersen takes a fundamentally different approach: rather than chasing tau protein after it has already been produced and begun to misfold, it targets the messenger RNA that encodes tau in the first place. The drug is injected into the fluid surrounding the spinal cord, giving it direct access to the central nervous system.

The 18-month Phase 2 CELIA trial enrolled 416 patients with early Alzheimer's and tested three doses of diranersen injected into the spine: either a 60 mg or 115 mg dose given every six months, or a 115 mg dose given every three months. At 60 mg, diranersen slowed cognitive and functional decline by 26% versus placebo on the CDR-SB, an 18-point scale — roughly on par with the 25–30% slowing seen in the Phase 3 trials of Leqembi and Kisunla, drugs that target amyloid. On two other cognitive measures, ADAS-Cog13 and MMSE, the 60 mg group showed 42% and 50% slower decline, respectively.

Patients on higher doses fared less well across those same measures, though the drug did reduce tau in cerebrospinal fluid by 50% to 65% across all dose groups. Diranersen is the first tau-targeting therapy to demonstrate reductions in both spinal fluid tau and brain tau pathology as measured by imaging in a Phase 2 study. The disconnect between tau reduction and clinical benefit at higher doses is a central puzzle. Researchers plan to investigate that paradox in a larger, confirmatory study. David Knopman, a neurologist and Alzheimer's expert at the Mayo Clinic, said the results were nonetheless sufficient to proceed to a late-stage trial, provided the company develops a clearer understanding of dosing.

Captain Sully Puts a Famous Face on the Disease

Capt. Chesley "Sully" Sullenberger III, best known for landing safely on the Hudson River after birds disabled both of the plane's engines in 2009, announced on July 14 that he has Alzheimer's disease. Sullenberger, 75, posted an update to his personal website saying he recently found out about the diagnosis, which is in an early stage. He received his official diagnosis in August 2025.

In his own words, Sullenberger described the early experience of the disease plainly. "For now, this means a name may not come easily to me, I forget a story I have recently told, or I don't sleep as well, but I am in the beginning of this long journey," he wrote. The former U.S. Air Force fighter pilot plans to continue serving the public by focusing on raising Alzheimer's awareness. Sullenberger is one of several public figures who have shared their Alzheimer's diagnoses in recent months, including veteran New York City news anchor Bill Ritter and longtime actor Danny Glover.

What Comes Next

Biogen has said it plans to advance diranersen into Phase 3 development. Diranersen is not yet approved, but a Phase 3 program now has scientific momentum behind it. For the tens of millions of people worldwide living with Alzheimer's — and the families navigating it alongside them — that momentum is exactly what the moment calls for. The science is moving. The conversation, thanks in part to voices like Sullenberger's, is growing louder. Both things are needed.