Pharma does often have some incentive to develop treatments for rare diseases. I worked at a startup where we spent years trying to advance a candidate with an addressable patient population of only 400 people. Such drugs receive favorable regulatory treatment from the FDA and the small number of patients is not a problem because pharma can still make its money by charging an exorbitant amount for the treatment. (Which is of course its own problem, but I'll resist the urge to digress).

The bigger issue is that those programs are riskier, largely because: a) the small number of patients makes it difficult to develop a clinical trial as it is so difficult to find patients to enroll. They have a range of comorbidities and other confounding factors that are hard to control for in such a small trial. And they are spread out geographically so you have to setup and qualify a lot more trial sites and potentially deal with concomitant manufacturing/delivery issues, multiple legal regimes, etc b) the trial itself is harder to develop because there may be no good clinically validated biomarkers you can use for efficacy endpoints. These means you fallback to universal biomarkers like the patient's subjective experience of pain and the rate of death/disability, which in turn means the trials take longer to run.

I'm optimistic that some of the recent moves in the space such as the FDA's Plausible Mechanism Framework for personalized treatments will help here. I see no reason why we can't have clinical trials with a single participant.

Anyway, I hope that Tranberger's work helps find something that will help your wife.