Robert Toczycki, JD, MBA
bioboyscout.com
bioboyscout@gmail.com
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The setup
Both Arrowhead Pharmaceuticals (ARWR) and Wave Life Sciences (WVE) are developing drugs that silence a liver gene called INHBE. Silencing INHBE lowers a hormone called Activin E, which in turn helps the body shed visceral fat, the harmful fat around organs that drives diabetes, fatty liver disease, and cardiovascular risk. Both companies are pursuing this as a new approach to obesity and metabolic disease, with twice-yearly subcutaneous dosing as the goal.
Until recently, the market viewed Wave as the clear leader in this race. That view formed on December 8, 2025, when Wave printed the first human data showing visceral fat reduction and lean muscle preservation from a single dose of its INHBE drug, WVE-007. The stock moved 147% that day. “Fat loss without muscle loss” became the headline thesis, and Wave became the consensus INHBE leader.
That consensus lasted just over three months.
On March 26, 2026, Wave released six-month follow-up data from the same patient cohort. The visceral fat number held: a 14% placebo-adjusted reduction (meaning 14% better than placebo). Lean mass was preserved. Activin E suppression was durable through seven months. But total body weight loss was just 1%. Waist circumference fell 3%. And the trial population had an average BMI of roughly 32, meaningfully leaner than the patients typically enrolled in obesity drug studies.
Wave’s stock fell nearly 50% that day, closing at $6.20. Bank of America cut its price target to $21. Wells Fargo cut to $13. The note language singled out “reduced conviction in the liver Activin E knockdown mechanism.”
Read that last sentence carefully. The market did not just punish Wave, it punished the INHBE monotherapy thesis itself.
That is the backdrop against which Arrowhead’s ARO-INHBE data, released at the EASL 2026 liver disease conference this morning, should be evaluated. The right question is no longer “who has the cleaner monotherapy headline?” The right question is the one Wave’s March miss raised: can INHBE silencing meaningfully move metabolic outcomes on its own, or does it need a partner drug (specifically, a GLP-1 like Mounjaro or Zepbound) to deliver?
ARO-INHBE’s EASL data is the cleanest answer yet to that question.
What the March repricing actually meant
The 50% drop in WVE was not just disappointment over a single weight loss number. It was a re-evaluation of the entire pharmacology.
INHBE silencing produces deep, durable suppression of Activin E. Wave proved that, but the downstream effect on the metrics the obesity market cares about (pounds lost, waist inches reduced, BMI change) came in well below the bar the December readout had set. A 1% placebo-adjusted weight loss does not compete with GLP-1s like Ozempic and Mounjaro, which routinely deliver 15-22% in late-stage trials.
This left two interpretations. Either the INHBE mechanism is intrinsically a “body composition” drug (reshaping where fat sits) rather than a “weight loss” drug (reducing total mass), and the December market reaction was overpriced, or INHBE silencing only delivers meaningful outcomes when layered on top of a GLP-1, not used alone.
Both interpretations lead to the same operational conclusion: INHBE-as-monotherapy is unlikely to support obesity peak sales models on its own. Either the asset needs to shift toward MASH (metabolic-dysfunction-associated steatohepatitis, a serious form of fatty liver disease) and broader metabolic dysfunction, where body composition matters more than scale weight, or the development path needs to run through combination with the GLP-1 class.
Wave is pursuing neither yet. Its planned Phase 2a multidose study, due to begin in Q2 2026, is still monotherapy in higher-BMI patients. The GLP-1 add-on trial is announced but unstarted. The MASH endpoint is exploratory in a protocol that has not yet begun enrolling. The bet Wave is making is that monotherapy will simply work better in heavier patients than it did in the leaner Phase 1 cohort.
That may turn out to be right, but it is a single-asset, single-strategy bet, dependent on a thesis the market already partially rejected.
The Zwischenzug
In chess, a Zwischenzug (literally “in-between move”) is an unexpected interjection in what appears to be a forced sequence. The opponent has played their move expecting a specific reply. Instead of responding directly, you play something else entirely, something that forces a reassessment of the whole position.
The ARO-INHBE data released this morning is that move.
The market was waiting for Wave to resolve the open question its March readout raised: whether monotherapy could work in higher-BMI patients. Arrowhead answered the question first, and from a completely different angle. Five data points stand out.
First, deeper target engagement. ARO-INHBE achieved an 85.3% mean maximum reduction in Activin E at the 400mg dose, with effect persisting beyond three months. Wave’s 240mg cohort hit roughly 78%. Deeper Activin E suppression directly addresses the sell-side concern about whether the liver INHBE knockdown mechanism reliably works.
Second, real GLP-1 combination data, in humans, today. ARO-INHBE has now produced clinical data in combination with tirzepatide 5mg (the active ingredient in Mounjaro and Zepbound) in two separate cohorts. The first included obese patients without diabetes. The second included obese patients with Type 2 Diabetes Mellitus (T2DM, the most common form of diabetes). Both were followed through week 24. The combination produced enhanced reductions in both visceral fat and liver fat compared to tirzepatide alone. This is the combination path Wave has yet to begin clinical work on.
Third, fatty liver disease data. ARO-INHBE produced a 44% placebo-adjusted reduction in liver fat content in the subgroup of patients with baseline liver fat above 8% receiving 200mg or higher of monotherapy (n=10, p<0.01). In the T2DM combination cohort, where baseline liver fat content was 16.9% (squarely in MASH territory), the combination produced substantially greater liver fat reduction than tirzepatide alone. In the cleaner week 24 readout from the non-T2DM combination cohort, ARO-INHBE 200mg plus tirzepatide reduced liver fat by approximately 45%, versus approximately 16% for placebo plus tirzepatide. That is a roughly 29 percentage point additive effect on top of what a GLP-1 alone delivers.
Fourth, durability. The longest-exposure data from ARO-INHBE shows visceral fat and liver fat reductions deepening from week 12 to week 24 within a single dose interval. Not waning, but deepening. This is the strongest possible support for a twice-yearly subcutaneous dosing schedule. Effects compound through the back half of the dose window, not the opposite.
Fifth, regulatory engagement. Arrowhead is now in active discussions with the FDA on Phase 2 study designs for both obesity and MASH, in parallel.
Every one of these data points addresses an open question raised by Wave’s March miss. The GLP-1 combination works. The mechanism engages the liver fat target deeply. The dosing interval holds. MASH is a credible second indication. T2DM patients respond.
The combination bet, reconsidered
The most consequential decision either company made in INHBE was structural: whether to run the combination program in parallel with monotherapy, or to sequence them: proving the standalone drug first, then layering on combinations later.
Wave sequenced. This produced the cleaner first headline in December. It also produced the harder second headline in March, because monotherapy on its own had to clear an obesity drug bar that increasingly favors percentage body weight loss, the metric Wave fell short on.
Arrowhead ran in parallel. Monotherapy and tirzepatide combination arms enrolled simultaneously, with T2DM patients included from the start. This produced a messier first data presentation (there is no single hero number in the EASL release), but a much more complete picture of where the asset actually works.
In retrospect, the parallel strategy was the right one. Not because monotherapy will necessarily fail; it may still succeed in Wave’s higher-BMI Phase 2a study, but the strategic value of an INHBE asset is dominated by its ability to layer onto the dominant GLP-1 class. The combination path is where the economics get decided. The company that shows combination data first will get the partnership first.
Wave’s GLP-1 add-on trial is scheduled for initiation sometime in 2026. The earliest that produces meaningful data is late 2027. By that time, ARWR will have Phase 2 combination data in hand, possibly Phase 2 MASH data, and could plausibly be in registrational discussions for the obesity-plus-MASH program.
The gap between the two programs is twelve to eighteen months wide. It is widening, and it is not yet reflected in either stock.
What this means for the acquirer thesis
If Eli Lilly (the obvious GLP-1-side buyer or licensor for an INHBE asset, given its tirzepatide franchise) were running a diligence process today, the operational read is unambiguous.
Wave offers a clean monotherapy lean-mass story, an unstarted combination program, and an exploratory MASH endpoint in a protocol that has not yet started enrolling. The development optionality is there but unproven.
Arrowhead offers deeper target engagement, demonstrated additivity with tirzepatide, in-hand liver fat data at MASH-relevant baseline values, a T2DM patient cohort with real combination data, week 24 durability, and active FDA Phase 2 engagement on both obesity and MASH. The development optionality is largely de-risked.
For an acquirer, de-risked optionality is worth more than narrative optionality. Always.
This does not mean Wave is uninvestable. The monotherapy thesis may yet work in higher-BMI patients. The company has real assets beyond WVE-007, particularly in RNA editing. The current valuation already reflects a damaged INHBE story, but the relative premium the market has historically assigned to Wave as the INHBE leader is not supported by the underlying clinical state of the two programs. If anything, that premium should have been migrating to Arrowhead for months.
What I expect from here
Three things to watch over the next two quarters.
First, ARO-INHBE 400mg plus tirzepatide week 24 data in the T2DM cohort, the single highest-impact pending data point from the current Phase 1/2a study (the 400mg combination week 24 data was not yet available for the EASL presentation). If that arm shows continued liver fat and visceral fat deepening at the high dose, the combination case is essentially closed for ARWR.
Second, Wave’s Phase 2a higher-BMI monotherapy data, with the first assessment expected three months after first dose. If placebo-adjusted body weight loss again comes in below 3-4%, the monotherapy thesis collapses entirely, and Wave’s path forward depends entirely on a GLP-1 combination trial it has not yet started.
Third, sell-side recalibration. Most analysts modeling the INHBE class still anchor on Wave’s December readout as the relative reference point, even after the March price target cuts. Expect models to start splitting INHBE valuation into “monotherapy obesity” and “MASH + GLP-1 combination” buckets, with ARWR taking the larger share of the second bucket. That repricing has not started in earnest. It will.
The narrative will catch up. Headlines win the day. Programs win the decade.
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— 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 is published by BioBoyScout and is intended for informational and educational 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. All financial projections, acquisition price estimates, and valuation analyses herein are hypothetical frameworks for analytical purposes and do not represent predictions of actual outcomes. Readers should conduct their own due diligence and consult a registered investment advisor before making investment decisions. All data cited herein were sourced from publicly available company disclosures, SEC filings, press releases, and peer-reviewed literature as of May 2026.
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.
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