It's not on these kind of diseases, this kind of work is usually done with public money, grants.
Money in big pharma is usually spent in researching weight loss and alternative drugs for common diseases. After all, the return of investment on these types of drugs is much higher.
For a big company to make a drug that costs 1 million dollars but only 1000 people in the world have it, and from those only perhaps 100 live in countries that can afford the drug might be a business opportunity but it's honestly not a huge profit which is why they will turn to public funding to research these.
Imo, if you use public money then the products should be free of intellectual property. Public money, public goods.