Powered for What, Revisited
Arrowhead's own guidance suggests the SHASTA-3/4 trials are more powered for pancreatitis than my first note allowed, which raises the stakes on the coming readout. A follow-up to Powered for What.
Robert Toczycki, JD, MBA
bioboyscout.com
bioboyscout@gmail.com
847.227.7909
X: @BioBoyScout
Going back through Arrowhead’s recent public comments changed my read on one important point from my last note, enough that it deserves its own write-up. The company spoke directly about the pancreatitis question, the one everyone is watching in the coming SHASTA results, and what management said shifts how that result should be understood. Everything here comes from those public comments.
What management has said
In two public investor appearances, the RBC Capital Markets and Jefferies fireside chats, Arrowhead’s Chief Medical Officer, James Hamilton, addressed the acute pancreatitis endpoint directly, and the transcripts are on the record. He said the company is cautiously optimistic that SHASTA-3 and SHASTA-4 will actually prove a reduction in pancreatitis to the standard scientists treat as proof, and that the trials are large enough to do it based on the number of pancreatitis cases showing up so far. A quick word on what that means. To prove an effect on something, a trial needs enough of those events to occur during the study, otherwise there is too little to measure. Hamilton gave the number on those calls, the RBC Global Healthcare and Jefferies fireside chats in mid-2026: if roughly nine or more pancreatitis events occur, at rates like those seen in the company’s earlier CORE studies, that is enough to give a reliable answer. He noted, too, that the events seen so far have not fallen far outside what they expected. A word on how a company knows anything while blinded: treatment assignments stay hidden, but the company can still see the total number of adjudicated pancreatitis events piling up across the whole trial. That aggregate count, without revealing which arm the events landed in, is enough to gauge whether the trial is likely to have the statistical power it needs.
How that reframes the endpoint
This puts pancreatitis in a more precise light than the market conversation, mine included, has generally allowed. Here is the cleanest way to hold it. Triglyceride lowering is the main thing these trials were built and sized to prove, and it is widely expected to come through. Pancreatitis is a second thing they track, and whether they can prove it depends on one variable: how many pancreatitis events actually occur during the study. If enough occur, the trials can prove it. If too few occur, they cannot, no matter how well the drug works. Management is saying it believes enough will occur, and that proof on pancreatitis is genuinely within reach, not out of the question the way my first note implied.
Squaring this with the sell side
This is worth squaring with the sell side, because there is a real tension in how the pancreatitis endpoint is being described. Pancreatitis is not a vague hope hanging off these trials. It is a formally named secondary endpoint in both SHASTA-3 and SHASTA-4, an adjudicated count of pancreatitis events and related hospitalizations, assessed by an independent committee against pre-set criteria. It was built into the trials on purpose.
Against that, JPMorgan’s July 17 note, the same one that raised its price target to $95 while valuing the entire brain platform at a single dollar, carries a one-line caveat that the trials are not powered to show a pancreatitis reduction. Both things can be true, and the reconciliation is the whole point. The trials are powered first for triglyceride reduction, which is the primary endpoint. Pancreatitis is a secondary endpoint, and whether it reaches statistical significance depends on one thing: whether enough pancreatitis events happen during the study to measure a difference. The honest statement is not that the trials cannot show pancreatitis, it is that they will show it only if the event count cooperates. Management, watching the blinded event rate, is guiding that it expects it will.
There is a strong reason to take that guidance seriously, and it is the piece the sell-side framing tends to skip. Plozasiran has already hit statistical significance on pancreatitis once, in the Phase 3 FCS trial, where the reduction in adjudicated events came in at an odds ratio of 0.17 with a p-value of 0.03. The drug has demonstrably moved this endpoint in a pivotal setting before. The open question in SHASTA-3/4 is therefore not whether the drug can reduce pancreatitis, which is already on the record, it is whether the larger and somewhat less severe sHTG population will generate enough events for the effect to clear significance again. That is a question about event counts, not about whether the biology works.
Which is what makes JPMorgan’s own scenarios worth reading closely. Its best case, worth 15 to 30 percent upside, is built on proving a statistically significant pancreatitis reduction, and its middle case treats a result that falls short of significance as, in the bank’s words, perceived negatively at first, with buyers stepping in depending on the magnitude. The point is not to guess at what the analysts privately believe. It is simpler and entirely on the page: JPMorgan’s own valuation framework assigns real additional upside to a significant pancreatitis result. Whatever the caveat about powering, the endpoint plainly remains an important determinant of value in the model itself. That is consistent with what management is guiding.
Worth adding on that dollar: valuing the brain platform at a single dollar, up from the zero it carried before, concedes the platform is worth more than nothing while still pricing it at a rounding error, a tacit admission of the point I made in Zero.
Why it raises the stakes
There is a cost to management raising expectations this way, and it should not be glossed over. Guidance sets the bar, and by guiding to proof on pancreatitis, management has raised the standard the readout will be judged against. The comfortable reading from my first note, that a pancreatitis miss would just mean the trials were too small to prove it and could be shrugged off, does not survive the company itself saying it expects to prove it. The result now carries real weight in both directions: proof would be a genuine win the market is primed for, and falling short would sting more than an underpowered endpoint otherwise would, because it would miss a bar the company set for itself. Higher expectation, higher stakes.
What it clarifies about SHASTA-5
It also corrects a piece of the surrounding debate that has the logic backwards, and this part cuts in Arrowhead’s favor. SHASTA-5 is not a fallback that exists because SHASTA-3/4 cannot demonstrate pancreatitis. Per Hamilton, it is a separate, dedicated outcomes trial in high-risk patients, those with prior pancreatitis events, designed to provide even stronger, confirmatory evidence, particularly for payers. The framing that treats SHASTA-5 as the consolation study for an endpoint the main trials cannot reach is mistaken. The main trials may reach it, and SHASTA-5 is built to reinforce the case rather than to rescue it.
The real question into the readout
Strip it down and the question was never whether SHASTA-3/4 can show pancreatitis. Management has publicly guided that it believes they can. The question is whether enough pancreatitis events actually occurred during the study, which no one will know for certain until the final data is unblinded and analyzed. That is the single thing the result turns on, and it is the one to watch. Everything else, the triglyceride result almost certainly coming through, the underlying biology, the real-world case, sits on firmer ground. This is what makes the coming readout more than another triglyceride study. It is a direct test of whether Arrowhead’s confidence in the pancreatitis endpoint was warranted, a test the company chose to invite by telling the market it expects to pass.
The discipline of this work is separating what a trial can prove from what the market assumes. This update tightens exactly that line on the pancreatitis question, and it is on the record straight, ahead of the results rather than after them.
A Note on Supporting Independent Research
If this note has been valuable to you, whether it shaped your thinking, validated your conviction, or simply saved you the time of doing this work yourself, a voluntary contribution is genuinely appreciated and directly funds the next paper.
For individual investors and readers
Any amount you feel reflects the value you received is welcome and meaningful. A contribution in the range of what you might pay for a single premium research report is a thoughtful gesture that makes a real difference.
For family offices, investment funds, hedge funds, and research platforms
This paper is the caliber of work that institutional research desks bill significant retainers to produce. If your team referenced it, distributed it internally, or used it to inform a position, a suggested contribution of $1,000 reflects the professional value of the analysis, though any amount is meaningful. Your support makes it possible to continue publishing at this level without a paywall that limits the reach of the ideas. If your organization requires an invoice to process a payment, please reach out directly at bioboyscout@gmail.com and one will be provided promptly.
There is no obligation and no expectation. This is purely a thank you for work that meant something to you.
Zelle: (847) 227-7909
Thank you for reading, and for being part of a community that takes this thesis seriously.
— Robert Toczycki | BioBoyScout
Important Risks, Disclosures, & Disclaimers
The author, Robert Toczycki (aka BioBoyScout), certifies that:
all views expressed in this note accurately reflect his personal opinions about the topic discussed;
he was not compensated in any form for producing this note; and
he has not received and does not receive compensation from Arrowhead Pharmaceuticals.
This note reflects the author’s personal opinions, is for informational purposes only. It does not constitute investment advice, a solicitation to buy or sell securities, or a guarantee of future results. The author holds a long position in Arrowhead common stock. Arrowhead Pharmaceuticals (ARWR) is a publicly traded company; investments in its shares involve material risks, including the risk of total loss.
About the Author
Robert Toczycki is an independent analyst and registered US Patent Attorney with a JD, an Executive MBA completed at the top of his class, and a BS in Mathematics and Computer Science from the University of Illinois at Urbana-Champaign. He has a deep passion for financial analysis, particularly identifying valuation discrepancies and demonstrating them through rigorous, data-driven research and solid analytics.
Comments or questions: bioboyscout@gmail.com.
Copyright © 2026, BioBoyScout. All Rights Reserved.
