You want a tough therapeutic area to work in? Try antifungals. There are plenty of problems that conspire to make it a real headache.
For one, fungal infections have a way of binning themselves into two categories, marked "pretty trivial" and "pretty life-threatening." Athlete's foot is a good example of the first one, and coccidioidomycosis is a good example of the second. Actually, that disease shows another form of the trivial/deadly dichotomy. Many people with coccidioidomycosis never realize that they had it, or that they had anything at all. It shows up as a mild cough or cold, and then disappears. But in some people, most especially HIV sufferers or other immune-comprimised patients, it's extremely bad news indeed.
So there are large markets where people aren't willing to pay much to be treated, and a number of much smaller, very desperate markets scattered all over the place. That's a tough situation, and the best thing would be to find a real blunderbuss antifungal that would pitch in for all of them.
And there actually is one, but it's a pretty nasty drug. For the worst systemic fungal infections, though, amphotericin B is basically all there is. It's given intravenously, and you have to keep a close watch on the side effects, which run to things like high fever, vomiting, and kidney damage. A less vicious, orally available drug that works as effectively would be a real advance.
It's not like people haven't tried. Fluconazole and Itraconazole are worthy attempts, but they suffer from their own side effect problems. Check out the general information here, and note, for example, the number of drug interactions. The "conazoles" are notorious for interacting with some key drug-metabolizing enzymes, particularly CYP 3A4, and thus sending the blood levels of other medicines all over the place.
And to top it all off, there aren't that many good drug targets in this area, or at least, not any more. There are companies that have bailed out of the whole field for lack of anything reasonable to do. There's some hope that the sequencing of fungal genomes might lead to some new targets, but that hasn't worked out too well with other organisms, and I include humans in that list. We can always hope.