$ARWR trades at over $10B today. If ARO-MAPT's Phase 1 reads positive in 2H 2026, the math says it's worth $55-$90B to a strategic acquirer. Not a guess. Four independent methodologies. Same range. Full paper: drive.google.com/file/d/1D5e…

$ARWR reported the first gene silencing in a human brain from a shot under the skin. The stock closed up 24 cents. Wave got +74% on two patients. Intellia +55% on six. Sarepta +35% in March on two programs licensed from Arrowhead. Same category of data. Same market. The hardest organ got four tenths of one percent. UBS says it plainly: ARO-MAPT is "not included in our valuation." A blank field is not an estimate of zero. It is a decision not to estimate. bioboyscout.com/p/the-liver-…

$ARWR silenced a gene in the human brain with a shot under the skin. Mean 73% tau reduction, 85% in one person. My reaction note is up. The headline is 73%. The number that matters is 105, the study day. Last dose was Day 15, so that was measured ninety days after the drug stopped. A primate comparison Arrowhead published in May that nobody has connected to today: spinal canal delivery varied 22x across brain regions. Under the skin, under 4x. The Bishop Moved bioboyscout.com/p/the-bishop…

WOW! 73%!!! $ARWR just silenced a gene in the human brain with a shot under the skin. Nobody has ever done that. Not once. Not anywhere. Here's the number nobody's reading: Day 105 is ninety days after the last dose. That's not a peak. That's a floor that held for three months with no drug on board. Biogen gets 50-65% through a needle in the spine. Arrowhead got 73% through a needle in the arm. Two doses. Not three. PSP and FTD regulatory talks already underway. The brain had no book. Arrowhead just wrote the first page.

$ARWR nobody takes intrathecal injections for twenty years before symptoms start. Presymptomatic tau lowering requires a subcutaneous drug. That is what gets tested tomorrow.

Roche licensed an ALK7 RNAi obesity drug from Rona today. Up to $100M near-term, $1.06B in milestones behind it. That makes five companies on ALK7: $ARWR, $ALNY, GSK, Novo, Roche. Nobody spends that way on a target they think is wrong. Arrowhead is the only one to have reported human data, silencing the gene in human fat cells in January. Not mice. Not monkeys. People. Here's what I'd actually watch. The target isn't the hard part. ALK7 is published. The human genetics are published. Anyone can look up which gene to silence. The hard part is getting an siRNA into a fat cell and keeping it there. That's chemistry, delivery, and a decade of failures nobody writes papers about. It's where these programs die. A hundred million near-term against $1.16B total isn't conviction. It's an option. Roche bought a call option on a program that still has to clear every step Arrowhead already cleared. Roche never disclosed the stage, but Rona's pipeline shows preclinical. That's two to three years to first human data, if nothing breaks. Roche just paid a hundred million dollars to start where Arrowhead already finished. That's the going rate for a seat at a table somebody else set.

Wednesday, $ARWR reports its tau number. A 60 gets called a triumph, a 45 a disaster, inside an hour. Two tau drugs already proved that reading wrong. One removed 98% of its target and changed nothing. The other cleared tangles from living brains and still missed its endpoint, with the best result at the lowest dose. The number answers one question: can a shot under the skin reach the brain. Not whether lowering tau helps anyone. What to watch instead. New paper: Ninety-Eight Percent of Nothing bioboyscout.com/p/ninety-eig…

The FDA built a fast lane for drug reviews four years ago. First three years: six requests, zero accepted. This week $ARWR walked in. Why was the lane empty? To use it you hand the FDA your whole application minus the final study reports, months early. Most filings are a scramble that ends the night before. You cannot buy an increment. You pay for it in advance, with work nobody watches. New note: The Increment bioboyscout.com/p/the-increm…

On October 14, $ARWR tests whether a shot under the skin can reach the human brain. The key: an antibody fragment that rides the transferrin receptor across the blood-brain barrier. The lock: two patents granted this year. Most investors have never looked at either. The Fab Choice bioboyscout.com/p/the-fab-ch…

$ARWR has written the first pages in fat cells and the lung. On October 14, it shows whether a shot under the skin can reach the brain. Big pharma is paying billions for new siRNA companies. Read the fine print: small checks upfront, big numbers only if the drugs work. That's an option, not conviction. Anyone can buy the liver playbook now. It's published, patented and aging. Nobody can buy the brain playbook. It hasn't been written yet. The opening is for sale. The middlegame still has to be earned. New paper: Out of Book bioboyscout.com/p/out-of-boo…

$ARWR set the date: October 14, first human data for ARO-MAPT. Everyone will watch how far tau falls. I'm watching the guest speaker. Adam Boxer of UCSF is one of the leading names in PSP and FTD, rare tau diseases nobody's talking about. His talk: "Silencing MAPT in Alzheimer's Disease and other Tauopathies." In PSP, tau damage sits deep in the brain, exactly where Arrowhead says its shot under the skin reaches, and the cleanest, smallest tau diseases may be the fastest road to proving the drug for the biggest one. New note: The Long Diagonal bioboyscout.com/p/the-long-d…

$ARWR just put a date on it. October 14: first human data for ARO-MAPT, a subcutaneous shot designed to reach the brain. The guest speaker is UCSF's Adam Boxer, one of the leading names in Alzheimer's, FTD and PSP trials. His talk: "Silencing MAPT in Alzheimer's Disease and other Tauopathies." Say bye-bye to all intrathecal gene silencing drugs. ir.arrowheadpharma.com/news-…

$ARWR slipped NfL into the ARO-MAPT endpoints at RNA Leaders. It's not in the trial registry. It's on the slide. That's a big deal. NfL is the nerve-damage biomarker that got tofersen an accelerated approval in ALS in 2023, even after its Phase 3 missed. FDA advisors voted unanimously that lowering NfL was reasonably likely to predict clinical benefit. In Alzheimer's, tau PET and p-tau will likely carry more weight. In PSP, a rare, fast-moving tauopathy with no approved treatment, NfL could be the fast lane. The slides already say "AD and related tauopathies" and "Phase 1/2a and Beyond." No regulator has accepted NfL for a tauopathy yet. If a PSP study with NfL as an endpoint shows up, that's the tofersen playbook. I laid out the early-approval case in The Number Nobody Is Watching bioboyscout.com/p/the-number…

Goldman resumed $ARWR this morning at Neutral, $74. The target blends a $72 standalone value with a $77 "theoretical acquisition value." Only 7% apart, and the acquisition number sits below the stock's own 50-day average. Nobody sells for seven percent. New note bioboyscout.com/p/nobody-sel…

$ARWR has put a drug into human trials roughly every four months for years. Not because RNAi is easy. Every one of them runs the same stations any drug runs. What changes is how many of those stations you have to build yourself. New piece on the machine bioboyscout.com/p/opening-pr…

New paper out: The Seconds. Really enjoyed putting this one together. $ARWR is now in six tissues. Liver, muscle, fat, brain, and eye from a simple shot under the skin. Lung by inhaler. The sixth isn't announced yet, but it's on the trial registry. Closest competitor is in only three. The gap isn't chemistry or patents. It's a few dozen people who have been failing at the same problem together for over twenty years. That's the part nobody can buy. bioboyscout.com/p/the-second…

$ARWR DIMER topline is out and it's good. One molecule, two genes, both silenced in a person. PCSK9 -72%, APOC3 -88% off a single dose. LDL-C -54%, TGs -73%, ApoB -50%. ApoB is the one I'd watch. The lipid drug is the headline. The architecture is the real story. New note. bioboyscout.com/p/dimer-topl…

New paper: The Outpost. Biotech clusters around Boston, SF and San Diego. $ARWR built its scientific core in Wisconsin. That looked like a disadvantage. It may have become a moat. How geography, talent stickiness and 15 years of continuity helped compound an RNAi platform. bioboyscout.com/p/the-outpos…