# A machine-readable taxonomy of why cancer drugs fail

Source: https://onco.cc/ideas/idea-tr2-failure-taxonomy/  
OnCo record `idea-tr2-failure-taxonomy` (Idea). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Drugs fail for distinct reasons: wrong target, drug never reached it, unacceptable toxicity, unselected population or poor trial design. A shared machine-readable taxonomy applied to every discontinued oncology programme in public pipeline databases would show where the system breaks, as AstraZeneca and Pfizer's own attrition analyses did.

## Summary

Analyses of attrition (for example those published by AstraZeneca and Pfizer on their own pipelines) show that failure reasons are learnable but rarely recorded consistently. A shared taxonomy (target biology, exposure, safety, efficacy in unselected population, biomarker failure, design, commercial) applied to every discontinued oncology programme in public pipeline databases would enable system-level diagnosis and comparison across sponsors and decades.

## Fields

- Kind: Idea
- Last checked: 2026-09-08
- Hypothesis: Applying the taxonomy to a decade of discontinuations will show that at least a third of efficacy failures were preceded by inadequate target-validation or exposure evidence, quantifying an avoidable loss.
- Rationale: Aviation and surgery improved by classifying failure. Pharma's 'five Rs' framework (right target, tissue, safety, patient, commercial) is a start that has not been applied openly.
- Proposed test: Curate 500 discontinued oncology programmes with two independent coders; publish inter-rater reliability and the distribution of causes.
- Maturity: speculative
- Actor: data

## Sources

- Bottleneck evidence (Failures are hidden): Anderson et al., Compliance with results reporting at ClinicalTrials.gov (NEJM 2015): https://doi.org/10.1056/NEJMsa1409364

## Connected records

- ideas: [A public registry of cancer treatments that were later shown not to work](https://onco.cc/ideas/idea-tr2-reversal-registry/), [A target de-risking index that counts failures as well as successes](https://onco.cc/ideas/idea-tr2-target-failure-index/), [Public post-mortem reports when a cancer drug programme is stopped](https://onco.cc/ideas/idea-tr2-termination-reports/), [Score every preclinical model by how often it predicted the clinical result](https://onco.cc/ideas/idea-tr2-model-report-cards/)
- bottlenecks: [Failures are hidden](https://onco.cc/bottlenecks/b-negative-results/), [The valley of death between lab and product](https://onco.cc/bottlenecks/b-translational-valley/)
- key papers: [Compliance with results reporting at ClinicalTrials.gov](https://onco.cc/key-papers/paper-anderson-n-engl-j-med/)

---
JSON: https://onco.cc/api/v1/entities/idea-tr2-failure-taxonomy.json