For decades, one of the most common serious liver diseases on Earth had a strange distinction: no approved drug. MASH — metabolic dysfunction-associated steatohepatitis, the aggressive form of fatty liver — affected millions and could only be managed with diet and exercise. Then, in 2024, that changed.
From the Knitify Pharma Demand Radar — our running read on where pharmaceutical demand is heading. We publish the observations; the method behind them stays in-house.
The signal: a market that didn't exist
A small but distinct fibrosis-and-liver cluster is now appearing in the radar, and at the center of it is resmetirom — the first drug the FDA ever approved for MASH. [1] It's an oral, liver-directed agent that works through the thyroid hormone receptor-β, cutting liver fat and fibrosis. Around it, the radar shows chemistry aimed at the other levers of fibrosis — TGF-β signaling, Wnt, inflammation resolution.
This is the cleanest kind of science-to-demand event there is. A "first-in-disease" approval doesn't just create demand for one molecule — it validates the whole disease as a commercial market. Every program that was waiting to see if MASH was druggable now has its answer, and the fast-followers, combinations, and next-generation mechanisms move at once.
What makes this cluster worth pausing on is the starting point. Most demand shifts describe an established market getting a little bigger or smaller; this one describes a market coming into existence. A few years ago the commercial answer to "how much active pharmaceutical ingredient does the MASH category need?" was, in practical terms, none — and that number is now moving off zero, against a patient population that is anything but small.
Why fatty liver was so hard to drug
To understand why a single approval matters this much, it helps to see why the field went empty for so long. MASH is the dangerous end of a spectrum that begins quietly. Excess fat accumulates inside liver cells — a state many people carry for years without harm. In a subset of patients, that fat load tips into cellular stress and inflammation, and the liver stops merely storing fat and starts injuring itself. Sustained injury activates the liver's scar-forming machinery, which lays down fibrous tissue that, left unchecked, can advance toward cirrhosis, liver failure, and cancer. The arc is fat, then inflammation, then fibrosis, then scarring that does not easily reverse.
Each step of that arc is a different biological problem, which is part of why the disease resisted so many attempts. A drug that quiets inflammation may do nothing about fat; one that clears fat may arrive too late to undo scarring. The disease is heterogeneous too — two patients with the same label can carry very different mixes of metabolic, inflammatory, and fibrotic drivers — so a single-target molecule that helps one group can miss another.
Then there is the problem that quietly defeated the most programs: measuring success. MASH progresses over years, not weeks, so a trial has to run long enough to see the liver actually change. And for a long time the gold-standard readout was a liver biopsy — invasive, subject to sampling variability, and unpleasant enough that it deterred enrollment and slowed every study that depended on it. When the endpoint is slow, invasive, and noisy, even a working drug is hard to prove, and a long list of candidates reached late-stage trials and could not clear that bar.
What the first drug actually does
The mechanism behind resmetirom illustrates how the field finally found a foothold. Thyroid hormone is a powerful regulator of metabolism, including how the liver handles fat — but turning up thyroid signaling everywhere in the body is dangerous, particularly for the heart. The receptor for thyroid hormone comes in more than one form, and the subtypes are distributed unevenly across tissues: one predominates in the heart, while the beta form does much of the work in the liver.
A drug that selectively engages the beta receptor and concentrates its activity in the liver can push the metabolic levers that clear fat from liver cells while largely sparing the tissues where broad thyroid stimulation causes trouble. Qualitatively, that is the idea: a liver-directed nudge to the organ's own fat-handling program, rather than a systemic thyroid effect. The important point for a demand read is not the elegance of one molecule but the proof it delivers — that the disease can be moved with an oral small molecule, on a regulatory path agencies were willing to accept. That is exactly the uncertainty that had kept the rest of the field on the sidelines.
Why a first approval de-risks a whole field
When a disease has never had an approved therapy, the risk facing every developer is not only "will my drug work?" but "is this disease drugable and approvable at all?" That second question hangs over everyone equally and suppresses the whole category — programs stay small, capital stays cautious, manufacturing stays theoretical. A first approval answers it for the entire field at once.
The de-risking is concrete. It signals that regulators will accept a defined endpoint and a workable trial design, so the next developer knows what a registration study needs to look like. It tells investors the commercial destination is real, which loosens funding for fast-followers and differentiated mechanisms. And it gives clinicians a reason to start diagnosing patients in earnest. None of this depends on the first drug being the best drug — its most valuable contribution may simply be existing. That is why a single molecule can light up an entire cluster rather than a single point: the chemistry now visible around resmetirom reflects a field that has been given permission to move.
The metabolic overlap and the combination era
MASH does not exist in isolation. It sits at the crossroads of the metabolic epidemic: most patients also carry obesity or type 2 diabetes, and the liver disease is in many ways a downstream expression of the same underlying metabolic dysfunction. That overlap is what makes the treatable population so large — it tracks the global rise in obesity and diabetes — and it also shapes where the next wave of therapy is heading.
The GLP-1 medicines now reshaping obesity and diabetes care attack the problem upstream, driving weight loss and improving the metabolic drivers that feed the liver in the first place. Liver-directed drugs act downstream, on the organ itself. The logical next step is to combine them — pairing upstream metabolic control with direct action on liver fat and fibrosis — while chasing the other engines of scarring in parallel. A first approval, in other words, does not just open one market. It opens a combination landscape, where the question shifts from "does anything work?" to "what works best together?" — and where a validated liver-directed anchor plus a metabolic backbone implies programs and supply arrangements that span two categories at once.
From zero to a supply chain: who has to build
MASH is enormous — the treatable population is measured in the tens of millions — and a category that had no manufacturing base, no established supply chain, and no meaningful API demand a few years ago now has to build all three. That construction problem lands differently on different stakeholders.
For small-molecule API makers and contract manufacturers, this is a rare thing: a brand-new market with a validated first entrant, where demand starts near zero and has almost nowhere to go but up. Building for it means forecasting from a standing start and completing tech transfer and scale-up for chemistry that had no commercial pull until recently — decisions easiest to get right when the shift is caught early rather than confirmed late. For metabolic and hepatology developers, the opening is a green field of fast-followers, next-generation mechanisms, and the combination trials the GLP-1 overlap invites. And for diagnostics, the opportunity is upstream of all of it: a treatment only helps if the right patients can be found, which puts a premium on non-invasive ways to identify and stage the disease without a biopsy. Each group builds against the same event, from a different side of it.
The radar catches these situations early because a first-in-disease molecule leaves an unmistakable trail — a compound moving from a standing start, tied to a disease that just became real. For a supplier, the question is never whether the demand will eventually be obvious; it is how much lead time separates the people who saw it forming from the people who waited for it to arrive.
The caveats: an approval is a beginning, not an endpoint
A first approval is a genuine inflection, but not a guarantee, and the honest read includes the friction. Much of the early progress in MASH rests on surrogate endpoints — improvements in the liver measured over a trial's horizon — rather than long-term outcomes such as progression to cirrhosis or liver-related events. Those confirmatory outcomes take years to mature, and the category's durability will ultimately be judged on them. Demand built on a surrogate can be real and still be provisional.
The larger near-term brake is diagnosis. A treatable population in the tens of millions is a theoretical market until those patients are actually identified, and most are not — the disease is quiet, awareness in primary care is uneven, and staging still leans on procedures patients avoid. The gap between how many people have MASH and how many are diagnosed and treated is where much of the projected demand will either materialize slowly or arrive in a rush, depending on how fast non-invasive screening spreads. That bottleneck is a variable, not a footnote.
And the competition is not waiting. The same approval that validated the category invited everyone into it, so the field is filling quickly with fast-followers, alternative mechanisms, and combination approaches. First-mover advantage in a newly opened disease tends to be real but temporary. For a demand read, that is not a reason for caution so much as a reason for timing: the window in which a signal is still ahead of the crowd is exactly the window worth acting in — which is the whole point of watching a market switch on rather than reading about it after the fact.
Editorial commentary from the Knitify Pharma Demand Radar. Not investment, legal, regulatory, or medical advice.