Targeted Therapy and the Resistance That Follows It
A drug aimed at a driver works for as long as the driver is required and the target is unchanged. This stop works through the routes back: mutation of the target, bypass signalling, and selection of a clone that was already present.
What a learner can do afterwards
- Explain oncogene dependence and where the therapeutic window comes from
- Classify a stated resistance mechanism as on-target or bypass, and say what evidence separates them
- Argue from clonal structure why resistance can appear faster than mutation rates alone suggest
1 · Read
You start from dependence. Some tumours lean entirely on one hyperactive driver pathway while healthy cells spread signaling across many inputs. Blocking that crutch harms the cancer far more than normal tissue, and the gap between the stalling dose and the poisoning dose is your therapeutic window.
You sort relapse into two routes. On target resistance changes the drug binding pocket so the inhibitor no longer grips, while the pathway stays essential. Bypass resistance leaves the target blocked but switches growth to a parallel route the drug never aimed at.
You sequence a relapsed tumour. Fresh mutations in the drug target argue on target, and you favor a next generation inhibitor. A newly active parallel receptor with the original target still suppressed argues bypass, and you favor adding a second blockade.
You expect resistance faster than fresh mutation rates predict. A billion cell tumour already harbors rare variants, so treatment selects the resistant ones instead of waiting for them. Lasting control needs combinations that close escape routes before selection opens them.
You explain the window by dependence, you classify relapse as on target or bypass from fresh sequencing, and you plan for pre existing clones.
2 · Watch
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Where it sits
Learn first
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Nothing builds on it yet.
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.