It would have taken a few years at least to conduct the research and develop it into a treatment that could have been administered to people.
An expert on 23rd century medicine, you are?
No, but I find it very hard to believe that they had a disease that was incurable and then in the space of three months they had a medicine that they were distributing to patients across the Federation.
They still need to run tests, y'know. Then analyze the data they get from the trials.