Drug research and development isn't something that happens overnight. Nobody in pharmaceutical research shows up on Monday and says, "What do you say we cure Alzheimer's disease this week. Naw, let's do cancer instead." Most drugs take years—five, ten, even more—before they are even ready for clinical trials. Instant gratification does not exist in the world of pharmaceutical science. It can get stressful and disheartening when you've successfully labeled a million vials, but have yet to find a compound that relieves inflammation, or cures cancer, or gets rid of Alzheimer's.
And on top of all your own stress and frustrations, pharmaceutical scientists will sometimes get heat from their superiors to get results. If those feel-good patient letters are cherries on the work sundae, that added pressure is like a rotten banana peel on top of your compost heap.