Most drugs ever made work by blocking or occupying a protein — sitting in its active site so it can't do its job (agonists, which switch a receptor on, are the main exception). A newer kind of molecule does something stranger and, in some ways, more powerful: it doesn't block the disease protein at all. It tags it for destruction and lets the cell's own machinery delete it.
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 science: a two-headed molecule
These are protein degraders, and the best-known kind — PROTACs — are bifunctional: one end grabs the disease protein, the other recruits the cell's disposal system (an E3 ubiquitin ligase), and a linker bridges the two. The molecule brings target and garbage-truck together, the protein gets marked, and it's degraded. Because the drug is a matchmaker rather than a blocker, it can work at low doses and hit targets that were considered impossible to inhibit. After years of promise, the modality just crossed its threshold: the first PROTAC was FDA-approved. [1]
The disposal system it hijacks already exists in every one of your cells. The ubiquitin-proteasome system is how a cell recycles proteins it no longer needs: an E3 ligase recognizes a doomed protein, an enzymatic relay stamps it with a small tag called ubiquitin, and once enough tags accumulate the protein is fed into the proteasome — a molecular shredder — and broken back into parts. Cells do this constantly, as ordinary housekeeping. A degrader builds none of that machinery; it simply tricks it into pointing at a protein it would otherwise have ignored.
The trick is geometry. When a PROTAC binds the target on one end and the ligase on the other, it holds the three together in what chemists call a ternary complex — target, drug, and ligase clamped into a single assembly. Held that close, the ligase does what it always does and tags whatever is in reach, which now includes the disease protein. That is the entire mechanism, and its elegance is that almost everything doing the work was already in the cell.
That first approval matters the way the first MASH drug or the first KRAS drug matters — it validates the whole approach and pulls the follow-on programs forward. Once a regulator has said yes once, the risk conversation shifts from "can this class work in humans" to "which target next."
Why "destroy" beats "block": event-driven pharmacology
A conventional inhibitor works by occupancy. As long as enough drug is sitting in the active site, the protein is silenced; the moment the drug washes out, the protein goes back to work. The effect tracks the drug's concentration minute by minute, which is why so much of medicinal chemistry is a fight to keep levels high enough for long enough without poisoning the patient.
A degrader works by event. It doesn't need to stay bound — it triggers one destruction, then drifts off to trigger another. This is what people mean by catalytic or event-driven pharmacology: a single degrader molecule can take down many copies of its target in succession, so the effect can be achieved at strikingly low doses. And because the protein is gone rather than merely muffled, the effect persists until the cell makes fresh copies — the biology, not the pharmacokinetics, sets the clock.
Reaching targets an inhibitor never could
The occupancy model has a hidden requirement: there has to be a pocket worth occupying. Classic drugs work because enzymes have deep, well-shaped active sites you can plug. A large fraction of the proteins that drive disease — transcription factors, scaffolding proteins, regulators that work by shape and contact rather than catalysis — have no such pocket. For decades these were written off as "undruggable."
A degrader relaxes that requirement dramatically. It doesn't need to jam an active site; it only needs a foothold — any spot on the surface it can grip long enough to bring the ligase near — which opens the door to targets that were never candidates before. It also changes what "hitting" a target means. Many proteins do harm not by their enzymatic activity but by their mere presence — holding a complex together, parking on DNA. An inhibitor can switch off the activity and still leave that scaffolding job intact. Deleting the protein removes both — the function you were aiming at and the ones you weren't.
PROTACs, molecular glues, and a short-handled toolkit
PROTACs are the most visible members of the family, but not the only ones. "Molecular glues" do a similar job with far less molecule: rather than a two-headed dumbbell joined by a linker, a glue is a small compound that subtly reshapes the surface of the target or the ligase so the two stick to each other on their own. No linker, no second binder — a cleaner, more drug-like molecule. The catch is that glues are much harder to design on purpose; many were found by luck before anyone understood why they worked, and turning that serendipity into a repeatable discipline is very much a live problem.
Both approaches lean on the same short-handled toolkit. The human genome encodes hundreds of E3 ligases, yet only a small handful have been successfully recruited so far, and the field leans heavily on a couple of favorites. That's a bottleneck and an opportunity at once. Different ligases are switched on in different tissues, so recruiting a new one could mean a degrader that acts in a tumor but spares healthy tissue, or one that still works after a cancer has learned to shut the old ligase down. Every validated recruiter is a new set of chemistry to invent, and the race to expand that roster is one of the defining contests of the field.
The hard part: linkers, ternary complexes, and drug-likeness
The word "linker" makes it sound like plumbing — a piece of tubing between two more important parts. It's closer to the opposite. Its length, flexibility, and chemistry decide whether target and ligase come together in a productive geometry or an awkward one, and a productive ternary complex is often more than the sum of its two grips: the pieces can reinforce each other's binding, or fight it. Small changes can flip a molecule from potent degrader to inert. Getting it right is still largely empirical — make a series, test them, learn — and that make-and-test loop is a body of work in itself.
Then there is the plain physical problem of size. Stitching two binders and a linker into one molecule produces something big — well outside the comfortable range where drugs cross membranes and survive a trip through the gut. That makes cell permeability and oral bioavailability genuine hurdles; a molecule that degrades its target beautifully in a dish is worth little if it can't get inside a cell. Much of the practical craft of the field is spent clawing back drug-like behavior from molecules that are, by the old rules, too large to be drugs at all.
The demand: twice the chemistry
And here's the part specific to degraders. An ordinary drug is one molecule that binds one thing. A degrader is effectively two binders stitched together with a linker — which means roughly twice the medicinal chemistry, plus the linker design that makes or breaks the whole molecule. Every degrader program needs target-binder chemistry, E3-recruiter chemistry, and linker chemistry. As the modality moves from promise to product, that's a distinctive and growing demand shape — more chemistry per drug, in a field that's about to multiply.
Stack the pieces and the shape gets sharper. Each program carries not one lead-optimization campaign but closer to three, joined by a make-and-test loop for the linker with no counterpart in a conventional small-molecule effort. Multiply that intensity by a modality drawing in target after target, and the demand isn't merely larger — it's larger in a particular direction, concentrated in exactly the building blocks and synthetic steps a two-headed molecule requires.
Who feels it first — and the caveats
The load lands unevenly. Contract manufacturers and CDMOs that can actually make these large, awkward molecules at quality are pulled toward specialization — degrader synthesis is not just more of the same chemistry. Suppliers of building blocks feel a compounded demand, because every program shopping for target binders is also shopping for E3-ligase recruiters and linker chemistry, three appetites where a conventional program had one. And the degrader-focused developers organizing around the modality set the pace, because their programs convert directly into orders for the pieces upstream. It's the kind of structural signal that only shows up if you're reading what the molecules are made of.
None of which means the path is clear. This is still an early modality, and early modalities disappoint as often as they deliver. The size problem is real and not fully solved; permeability and oral dosing remain live constraints. Resistance is a specific worry — because a degrader depends on borrowing a particular E3 ligase, a tumor can in principle escape by losing or silencing that ligase, blunting the drug without ever touching the target. And the narrow toolkit concentrates risk on a few well-worn recruiters. The direction of travel is unmistakable; the timeline and the winners are not. What we're watching is a field whose chemistry-per-drug is going up at the same moment the number of drugs is set to climb — a combination worth reading closely.
Editorial commentary from the Knitify Pharma Demand Radar. Not investment, legal, regulatory, or medical advice.