Newsletter · · Ashutosh Agarwal

For the First Time, Cutting Tau Moved Alzheimer's - Biotech Pipeline: Gene/Cell, Neuro & Tools - Week of September 13, 2026

Biotech Pipeline: Gene/Cell, Neuro & Tools for the week of September 13, 2026. Podcast synthesis on Biogen's claim that reducing tau, not just amyloid, improved cognition in an Alzheimer's trial for the first time, the p-tau217 blood test going mainstream with a '30% rule' for judging anti-amyloid drugs, and new pediatric CRISPR (Casgevy) data that freed children from sickle cell and thalassemia but included a death from conditioning chemotherapy.

Biotech Pipeline: Gene/Cell, Neuro & Tools

Week of September 13, 2026: For the First Time, Cutting Tau Moved Alzheimer's

For thirty years, the whole fight against Alzheimer's has been about one sticky protein: amyloid. Clear the plaque, the thinking went, and you slow the disease. This week the head of one of the field's biggest companies said something that quietly moves the goalposts: that going after a second protein, tau, changed how patients actually think, for the first time in a trial. That came in the middle of a week where Alzheimer's was suddenly everywhere on the podcasts: not the shouting-match version, but a genuinely rich conversation about a blood test that's going mainstream, a "30% rule" that now separates the drugs that work from the ones that don't, and the awkward question of whether we should start screening perfectly healthy people. Gene editing got its own real news too, hard data on the first CRISPR medicine now working in young children, shadowed by a child's death. And the life-science tools world stayed silent for yet another week. Here's what was actually said.

TL;DR

  • Biogen's CEO says hitting tau, not just amyloid, improved cognition in a trial, a first. Chris Viehbacher told a healthcare conference that recent phase 2 results "demonstrated for the very first time that actually if you reduce tau, you can actually affect cognition." It still needs a phase 3, but it's the clearest sign yet that the next wave of Alzheimer's drugs will aim at a different target. (Squawk on the Street, Sep 9)
  • The Alzheimer's blood test has quietly arrived, and there's now a rule for reading the drug data. A leading biomarker scientist explained that the p-tau217 blood test now runs in ordinary hospital labs worldwide, and that anti-amyloid drugs only help patients when they shift the key brain markers by about 30%: the early drugs moved them just 10% and flopped. (Dementia Matters, Sep 8)
  • The first CRISPR medicine now works in kids, but a child died from the harsh prep, not the edit. New data show Casgevy freeing children aged 5–11 from sickle-cell crises and transfusions, yet every child had a serious side effect and one died from the chemotherapy used to prepare them. The takeaway experts drew: this is exactly why the field is racing toward editing inside the body instead. (NEJM This Week, Sep 9)

What's new

The story of the week: Alzheimer's treatment may be about to change targets. The most important thing anyone said in our universe this week came from Biogen CEO Chris Viehbacher, interviewed at the Wells Fargo healthcare conference in Boston. Biogen already sells two Alzheimer's drugs that attack amyloid, the plaque protein. But Viehbacher pointed to a second protein, tau, that builds up as the disease worsens, and dropped what is, if it holds up, a real milestone: "To have Alzheimer's, you need to have presence of both amyloid and tau. And the neurology community has always felt that you really have to go after tau. We recently had phase two results that demonstrated for the very first time that actually if you reduce tau, you can actually affect cognition." He was careful to add the caveat every honest executive adds ("we'll still have to study that in a phase three study"), but the claim itself is new. For decades tau has been the protein everyone agreed mattered and no one could show moved the needle when you targeted it. Biogen now says it did. (Squawk on the Street, Sep 9)

"We recently had phase two results that demonstrated for the very first time that actually if you reduce tau, you can actually affect cognition." (Chris Viehbacher, CEO, Biogen)

He also put a number on the value of treating early. Looking at patients with low levels of tau (meaning the disease hadn't advanced far), "after six months, we had 70% of patients stable on disease and 60% actually showed some improvement." His logic for why earlier is better: amyloid appears to trigger the overproduction of tau, so if you stop amyloid soon enough, "you may never have the production of tau, and you may never get that disease." Biogen is testing exactly that idea in pre-symptomatic people, a study called AHEAD 345 that reads out in 2028, which he called a potential "real game changer." And he sketched a busy few years: "10 phase three programs that could now start to read out as early as next quarter," and "five new molecules coming to market that could treat up to eight different diseases," spanning rare kidney disease, lupus, a childhood epilepsy called Dravet syndrome, and more. After a $5.6 billion deal, he said Biogen isn't hunting for big acquisitions; it's "already building the growth platform for Biogen for the 2030s." (Squawk on the Street, Sep 9)

The second story: the Alzheimer's blood test has gone mainstream, and there's now a way to tell the good drugs from the duds. On Dementia Matters, Dr. Henrik Zetterberg (one of the world's leading brain-biomarker scientists, based in Gothenburg) laid out how fast the plumbing of Alzheimer's diagnosis has changed. A blood test called p-tau217 (a form of the tau protein) can now be run "on a number of clinical chemistry instruments that are available in general labs, in general hospitals around the world." In plain terms: the test that used to require a spinal tap or a brain scan is becoming a routine blood draw. A refined "brain-derived" version is coming that's even more specific, with fewer false readings from things like kidney trouble. (Dementia Matters, Sep 8)

The most useful thing he said, for anyone trying to judge which Alzheimer's drugs are real, was a simple threshold. The first, weak anti-amyloid antibodies nudged the key brain markers down by about 10%, and produced no benefit patients could feel. What changed is that scientists now know how much movement actually matters: "these markers need to change 30% and then we see across different anti-amyloid antibodies that those who do change these... by 30% or more they are the ones that have produced clinically meaningful slowing." That's a clean yardstick: a 10% biomarker shift is noise; a 30%+ shift is a drug worth having. He also flagged a safety marker, neurofilament light (a sign of nerve-cell injury): if it spikes after a patient starts a drug, "halt the administration." (Dementia Matters, Sep 8)

He was candid about the limits, too. In a person with no symptoms, a positive p-tau217 test only means about a 40% chance of actually having amyloid in the brain, versus 85–90% in someone with memory complaints. So in healthy people the test flags risk, not a diagnosis. And he pointed to the drugs getting easier to take: new antibodies engineered to slip across the blood-brain barrier (lowering the brain-swelling risk), and shot-under-the-skin versions patients can give themselves "like people can give themselves insulin." (Dementia Matters, Sep 8)

The third story: the first CRISPR medicine now works in children, with a sobering asterisk. NEJM This Week walked through fresh data on exa-cel, the CRISPR gene-editing therapy sold as Casgevy (from Vertex and CRISPR Therapeutics). Two new studies tested it in children aged 5–11: 15 kids with a severe inherited anemia (transfusion-dependent beta-thalassemia) and 11 with sickle cell disease. Followed for at least 16 months, the children became free of transfusions or of the brutal pain crises that define sickle cell, a genuinely life-changing result. (NEJM This Week, Sep 9)

But the honest reading includes the harm. "All the participants had grade 3 or 4 adverse events" (that is, serious ones). And "two children with transfusion-dependent beta-thalassemia had severe veno-occlusive liver disease that was assessed as being related to busulfan conditioning, one of whom died." The crucial nuance: the death was tied to the harsh chemotherapy used to prepare the body for the edited cells, not to the gene edit itself. That distinction is the whole plot, because it points directly at where the field wants to go next. NEJM's editorial (by Alexis Thompson of Children's Hospital of Philadelphia) said it plainly: an "in-vivo gene editing strategy" (editing the genes inside the patient's own body, "without an autologous transplantation and myeloablative chemotherapy") "may ultimately address remaining clinical and perhaps financial challenges." In other words, the version of gene editing that skips the transplant and the toxic prep is the prize. (NEJM This Week, Sep 9)

The debate

Alzheimer's: is amyloid enough, or do you have to hit tau? This week, unlike some recent ones, both sides actually showed up. The amyloid-first camp got its strongest evidence in a while: Biogen's own data showing that treating early, in low-tau patients, left 70% stable and 60% improved at six months, proof the plaque approach does something real when used soon enough. But the same CEO conceded the ceiling of that approach and pointed past it, arguing you ultimately "have to go after tau," and claiming the first trial evidence that doing so helps cognition. Meanwhile, the biomarker scientist's "30% rule" is the referee both sides now have to answer to: it explains why the first amyloid drugs failed (they only moved the markers 10%) and sets a bar the tau drugs will have to clear too. The honest synthesis: amyloid is no longer the only game, the field is visibly pivoting toward a two-protein strategy, and we finally have a numeric yardstick to judge whichever drug comes next, but the tau breakthrough is a phase 2 claim from an interested party, not yet a phase 3 fact. (Squawk on the Street, Sep 9; Dementia Matters, Sep 8)

Should we screen healthy people for Alzheimer's at all? Now that a blood test is cheap and easy, this is the live question, and The Lancet Neurology devoted a whole series to it. The case for: the logic of stopping irreversible brain damage before symptoms is, as one writer put it, "undeniable," and treatments for people who feel fine "are inevitable" if prevention trials succeed. The case against: you risk "medicalizing aging itself, creating a large population of patients in waiting who may never become symptomatic," plus real harms: "anxiety, stigma... concerns about insurability." The group's answer was a careful middle path: build the clinical pathway now so health systems aren't caught flat-footed if the prevention trials work, while being honest that a positive test in a healthy person signals risk, not destiny (their analogy: it's like cholesterol, not a diagnosis). A geriatric psychiatrist on The Medical Mind drew the same line more bluntly: the FDA has approved plasma biomarker tests for people 55 and older who already have cognitive symptoms, not for a worried 40-year-old, where a false positive could be "like a death sentence" for insurance and peace of mind. (The Lancet Neurology, Sep 9; The Medical Mind, Sep 10)

Gene editing: the cure that came with a coffin. The Casgevy children's data crystallized the field's central tension. Bull case: a one-time treatment freed kids from a lifetime of transfusions and pain crises, the closest thing to a cure inherited blood diseases have ever had. Bear case: every child had a serious adverse event, and a child died, not from the edit, but from the myeloablative chemo required to make room for the edited cells. Both sides agree on the resolution, which is unusual: get rid of the transplant and the toxic prep by editing inside the body. That's why the "in-vivo" versions being chased by the likes of Intellia and Verve matter so much: they're trying to keep the cure and lose the coffin. (NEJM This Week, Sep 9)

Names in play

  • Biogen (BIIB): the clearest read this week. The market has "treated you now like a growth stock," the interviewer noted, and Viehbacher leaned in: an "inflection point" toward "sustainable revenue growth," 10 phase 3 readouts starting as soon as next quarter, and the first-ever tau-and-cognition signal on top of its two approved amyloid drugs. He also said FDA turnover (a new commissioner, a new drug-review chief, thousands of departures) hasn't slowed approvals: "they've maintained their timelines... our experience has still been positive." The bull case is the pipeline breadth; the thing to watch is whether the tau result survives a phase 3, and whether AHEAD 345 (2028) validates the prevention bet. (Squawk on the Street, Sep 9)
  • Vertex (VRTX) and CRISPR Therapeutics (CRSP): Casgevy grows up, carefully. The new pediatric data extend Casgevy's reach to children as young as five, a real commercial expansion for the first approved CRISPR medicine. But the death from conditioning chemo is a reminder that the current, ex-vivo version is a heavy lift (a hospital odyssey, not a shot), which caps how big it can get and hands the long-term advantage to whoever cracks in-body editing. (NEJM This Week, Sep 9)
  • Vertex again, but as a retail favorite, take with salt. On Strategy Sunday, retail-investing host Armando Pantoja named VRTX his first biotech pick ("already making billions, already has new drugs coming... I think it's going to beat the market") while swearing off "penny stocks." This is a pundit's watchlist pick, not analysis, and we flag it as such; the more interesting point he made was macro (below). (Strategy Sunday, Sep 8)

Read-throughs

  • The diagnostics quietly riding the Alzheimer's wave. The single most underappreciated read-through this week is that the p-tau217 blood test now runs "on clinical chemistry instruments... in general labs, in general hospitals around the world," and the emerging standard is a panel (p-tau217 plus GFAP, an inflammation marker, plus neurofilament light) already available in many clinical labs. Every anti-amyloid or anti-tau drug that launches needs this testing infrastructure to find the right patients and monitor safety, which makes the lab-instrument and assay makers a levered bet on the whole Alzheimer's build-out, even though none of the tools companies themselves said a word on the podcasts this week. (Dementia Matters, Sep 8)
  • The imaging bottleneck is real, and cancer networks are the workaround. The flip side of an Alzheimer's launch is a scanning burden most health systems can't yet handle: about 20% of patients on the current drugs develop brain swelling or small bleeds (called ARIA), caught only by MRI, so patients get "five or six MRI scans" in the first six months, plus amyloid PET scans before treatment and again at 18 months. Neuroradiology expertise "is scarce even in well-resourced health systems." The clever fix experts pointed to: repurpose the imaging networks already built for cancer, since "those networks and resources can have dual utilization." For anyone watching imaging capacity or radiology staffing, that's the pinch point. (The Lancet Neurology, Sep 9)
  • The cost of Alzheimer's, and who gets left out. A geriatric psychiatrist put the money in perspective: the US spends "$210 billion" on Alzheimer's today, on track for "over a trillion dollars," and up to "45% of cases... can be preventable" by managing 14 risk factors like blood pressure, hearing and diabetes. He was blunt that the fancy new drugs create a two-tier system (they need PET scans, MRIs and infusion centers that "the person in rural America actually misses out" on), which is why the shift to a simple blood test and under-the-skin dosing matters beyond convenience. (The Medical Mind, Sep 10)
  • China keeps pulling the industry's center of gravity, and sequencing keeps getting cheaper. On Telltales, the hosts flagged a trend they think is under-covered: "if you look at the first half of 2026, 42% of all pharmaceutical licensing deals came out of China," up from roughly 20% in 2023 and near zero not long before, with Chinese developers moving drugs "three times faster and 30 to 50% lower cost." They also noted, discussing personalized mRNA cancer vaccines, that DNA sequencing "no longer costs a billion dollars, rather it costs hundreds of dollars," the same cost collapse that underpins both cheaper cancer immunotherapy and the whole gene-reading economy. It's a discussion podcast, not primary data, but the China licensing shift is a genuine structural force worth tracking. (Telltales, Sep 9)
  • The macro switch for the whole sector flips Tuesday. The retail-investing take on Strategy Sunday was thin on stocks but right on the calendar: the Federal Reserve's September 16 rate decision is the thing that matters for biotech, because cheaper money "could possibly flow into biotech after years of being starved for capital." Small-cap biotech lives and dies on the cost of capital, so the read-through is simple: a dovish Fed is a tailwind for exactly the gene-editing and early-stage names this newsletter follows. (Strategy Sunday, Sep 8)

What changed

Last week the podcasts were all gene editing and Alzheimer's had only a critic, a skeptic tearing into the amyloid drugs with no one to answer him. This week the pendulum swung hard the other way. Alzheimer's got the deepest, most constructive coverage it's had in a while: a CEO claiming the first tau-and-cognition win, a top scientist explaining why the early drugs failed and how to tell the real ones apart, and a serious debate about screening healthy people, the grown-up conversation, not the food fight. Gene editing, meanwhile, moved from last week's uncomplicated optimism to something more sober: the first CRISPR medicine works in kids, and it also just killed one, a reminder that the current approach is a cure wrapped in a very hard procedure, and that the whole field's next act is getting rid of that procedure.

What didn't show up

Being straight about the gaps, because two are now chronic:

  • Life-science tools and bioprocessing, dark again. Nothing from Thermo Fisher, Danaher, Agilent, Revvity, Illumina, Sartorius, Repligen, Bruker or Waters; no read on single-use book-to-bill, the destock-to-restock cycle, sequencing prices from the tools names themselves, or how China and NIH funding are hitting research demand. This is now a multi-week silence for the tools complex on the podcasts. The only tools-adjacent signal was indirect: the Alzheimer's blood test running on standard lab instruments, and a passing mention that sequencing costs have collapsed.
  • Gene-editing stocks got no dedicated deep-dives. CRISPR Therapeutics, Intellia, Beam and Verve surfaced only through the Casgevy data and its in-vivo read-through: no standalone episode dug into any of them as a stock, and there was no fresh in-vivo editing readout (ATTR, cholesterol) this week.
  • No commercial launch numbers for Leqembi or Kisunla. Plenty on the science and the plumbing of Alzheimer's, but no fresh patient-start figures, Medicare-coverage updates, or head-to-head uptake data for the marketed drugs. And no AbbVie or Roche neuro/tau coverage.