FDA guidance explaining why Insmed can now apply for Breakthrough Therapy designation -
[ What are the differences between the breakthrough therapy designation and the fast track designation?
Although breakthrough therapy and fast track designation programs have similarities, as they both are intended to expedite the development and review of drugs for serious or life-threatening conditions, there are differences in what needs to be demonstrated to qualify for the programs.
A breakthrough therapy program is for a drug that treats a serious or life-threatening condition and preliminary clinical evidence indicates that the drug may demonstrate substantial improvement on a clinically significant endpoint(s) over available therapies.
In contrast, a fast track program is for a drug that treats a serious or life-threatening condition, and nonclinical or clinical data demonstrate the potential to address unmet medical need ]
So ....... the primary endpoint we were all hoping would be met was a greater number of trial participants in the Arikace arm recording a significant decrease in bacterial concentration - as evidenced by the culture analysis.
That result may have been sufficient to support a fast track approval - on the basis that evidence that Arikace decreases bacterial concentration (not of itself clinically significant) is reasonably predictive of eventual conversion to culture-negative (clinically significant).
There was no realistic expectation of early culture conversion in this patient population - therefore that outcome was included only as a secondary endpoint.
However 25% of the trial participants on Arikace did in fact convert to culture-negative with just twelve weeks of therapy.
Unexpectedly hitting an endpoint which IS clinically significant promoted Arikace from a potential fast track approval to a potential Breakthrough Therapy approval.