Rational Drug Design Finds 9% of Drugs. The Industry Calls It a Revolution.

In my last post on drug development, I traced how unreliable preclinical science flows downstream into failed clinical trials. But there's a deeper fiction at the heart of the pharmaceutical industry — one about how drugs are discovered in the first place.

The story goes like this: scientists identify a molecular target, design a molecule to hit it, and create a drug through rational, mechanistic understanding. It's the story the industry tells investors, regulators, and the public. It's also the story a systematic review of 32,000 articles suggests is mostly wrong.

The Poster Child's Real Story

Imatinib — sold as Gleevec — is the drug the industry points to when it wants to prove rational design works. The narrative is clean: scientists identified the Philadelphia chromosome translocation in chronic myeloid leukemia, designed a molecule to block the BCR-ABL fusion protein, and created a miracle drug that turned a fatal cancer into a manageable condition.

Except the actual history is messier. The compound was originally optimized against PDGFR, not BCR-ABL. Its ABL inhibitory activity was carried along secondarily — a fortunate accident, not a designed feature. The final compound was selected through phenotypic cell-based assays — watching which molecules killed cancer cells — not purely through biochemical target binding. Its expansion to gastrointestinal stromal tumors was driven by empirical clinical observation, not rational prediction.

Even the scientists involved questioned the narrative. Brian Druker asked: "Imatinib: paradigm or anomaly?" William Kaelin asked: "Gleevec: prototype or outlier?" The people closest to the discovery weren't sure it proved what everyone said it proved.

The story was true enough to tell. But the telling made it truer than it was.

The Number

In 2023, Arash Sadri published a systematic review in the Journal of Medicinal Chemistry that should have upended the industry's self-image. He manually analyzed roughly 32,000 articles and patents spanning 150 years of drug discovery. His finding: only 9.4% of small-molecule drugs were actually discovered through target-based approaches.

Worse: even that 9.4% couldn't be cleanly attributed to target-based methods. The therapeutic effects of those drugs "cannot be solely attributed and reduced to their purported targets, as they depend on numerous off-target mechanisms unconsciously incorporated by phenotypic observations." The drugs that supposedly proved rational design works were partly working for reasons their designers didn't understand.

Sadri's conclusion was blunt: "reductionist target-based drug discovery may be a cause of the productivity crisis in drug discovery."

The Drugs That Worked Without an Explanation

The New York Times called aspirin "the wonder drug that nobody understands" in 1966. It had been in use for nearly seven decades by then. John Vane wouldn't discover its mechanism — COX inhibition blocking prostaglandin synthesis — until 1971. He won the Nobel Prize for it in 1982.

Metformin is the world's most prescribed diabetes drug. Its precise mechanism of action is still a matter of active scientific debate. Lithium has been used for bipolar disorder since 1949. Which of its molecular targets actually matter remains uncertain. General anesthetics have been putting people to sleep for 180 years and the mechanism is still contested.

Then there's tianeptine — an antidepressant that enhances serotonin reuptake instead of inhibiting it. The exact opposite of SSRIs. Yet it has comparable antidepressant effects. If the serotonin hypothesis were correct, tianeptine should make depression worse. It doesn't.

More than 50% of FDA-approved drugs have mechanisms "not fully elucidated" according to their official labeling. Roughly 7% have no known primary target at all. Up to 21% lack a well-defined mechanism. These aren't historical curiosities. This is the current state of pharmacology.

The Data That Should Have Changed the Story

In 2011, Swinney and Anthony published a study in Nature Reviews Drug Discovery analyzing how first-in-class drugs — the genuinely novel ones, not me-too variations — were actually discovered between 1999 and 2008. Phenotypic screening, the old-fashioned approach of testing compounds against cells and seeing what happens, produced 28 first-in-class drugs. Target-based rational design produced 17.

The method the industry claims to prioritize was outperformed by the method it claims to have surpassed.

Fifty Years of Constructed Narrative

If the data are this clear, why does the rational design narrative persist? Because it was built deliberately.

Jonathan Liebenau, a historian of science, documented the construction explicitly in a 2005 paper in Studies in History and Philosophy of Science:

"Drug companies have been working for over fifty years to convince their various publics that their drugs have their origins in complete scientific understanding and precise modelling rather than in empirical processes of trial and error. Rational drug design is only the latest avatar of this general trend."

This isn't a conspiracy theory. It's a peer-reviewed academic observation about institutional narrative construction. The industry didn't stumble into the rational design story — it spent decades building it.

Derek Lowe, a veteran medicinal chemist writing at Science, identified the rhetorical mechanism: adopting the word "rational" was "the best advertising that the field's ever achieved, because it makes everything else seem irrational (or at least arational) by default." Once you call your method "rational," the alternative isn't "empirical" or "phenotypic" — it's "irrational." The naming won the argument before the evidence could weigh in.

And by 2025, Sadri was calling out the persistence as a kind of intellectual seduction: the field remains captive to "our enchantment with the alluring reductionist promise of target-based drug discovery: the promise that disorders and therapeutic effects can be reduced to single proteins; a simplistic and naïve promise indeed."

Why the Fiction Persists

The rational design narrative survives not because it's accurate, but because it's useful. It serves institutional purposes that empirical discovery — messy, uncertain, hard to predict — cannot:

The result is what you might call Eroom's Law made legible. Since 1950, the number of new drugs approved per billion dollars of R&D spending has halved roughly every nine years. The industry has gotten exponentially less productive even as its narrative about precision and rationality has gotten louder. The story and the outcomes have been moving in opposite directions for decades.

The Contradiction

This is a different kind of knowledge failure than the ones I've written about before. The pipeline post was about bad science flowing downstream. The replication amplifier was about incentive structures amplifying falsehood. This is about narrative maintenance — when the story about how something works persists because the story serves institutional purposes, not because the evidence supports it.

The pharmaceutical industry simultaneously:

1. Claims to use rational, target-based drug design as its primary methodology
2. Succeeds most often through empirical approaches it characterizes as outdated
3. Has spent 50 years constructing a narrative that obscures this gap
4. Has grown less productive as the rational design narrative has grown more dominant

The field itself is starting to say the quiet part out loud. A 2024 review in Expert Opinion on Drug Discovery acknowledged "remarkable attrition due to lack of efficacy" from "flawed target hypotheses or incomplete understanding of compensatory mechanisms." A 2025 editorial in Future Medicinal Chemistry argued that target-based approaches are "hypothesis-based, and this is one of the fundamental reasons for its limitations." The literature is admitting what the data already showed.

But the industry's marketing, investor presentations, and funding structures still overwhelmingly favor target-based language. The gap between what the literature admits and what the industry practices is the contradiction. And unlike the other contradictions I've covered — where the evidence shifted but the consensus lagged — this one was constructed from the start. The story was always cleaner than the science.

The drugs that actually save lives don't care whether we understand how they work. Aspirin didn't wait 74 years for Vane to explain it. The question is whether an industry that insists on a false narrative about its own methods can afford the productivity crisis that narrative helps sustain.