If I had to take a guess it’s because drug A + B != AB The drugs in question could, combined have deleterious effects (say if their extortion mechanisms are th

If I had to take a guess it’s because drug A + B != AB The drugs in question could, combined have deleterious effects (say if their extortion mechanisms are the same). This shouldn’t be a problem because Tylenol + Advil has been done for decades. However, a beauricracy doesn’t see it as a solved problem to fast track unless there is a specific fast track for this exact scenario.