Question: so you make a drug and you have rights f

Question: so you make a drug and you have rights for x years say 12 before they can make a generic, is that for the drug as a whole or per indication? So in this made up example combo gets approved tomorrow and say we have 12 year exclusive rights and clock starts. 10 years from now they figure out it’s treats Alzheimer. Are there only 2 protected years for Alzheimer or a new 12?