There's an AIDs drug that no longer exists because of an isomorph of the drug compound that formed and spread making it so the original compound couldn't be made anymore.
Source?
This is where I learned about it. Veritasium video
https://youtu.be/ksn5yrsC3Wg?is=GIaOMC0Jqg7qptlC
https://en.wikipedia.org/wiki/Ritonavir?useskin=vector#Polym...
When in solid form even the smallest amount can convert the whole batch to the much less effective version.
https://en.wikipedia.org/wiki/Ice-nine#Real-life_analogues