> For a disease like [Huntingtons], it's never going to make sense for major pharmaceutical companies to invest the effort to develop entirely new drugs

This is ... not correct.

Roche, Regeneron, and Novartis all have novel HD drugs under development in tandem with smaller labs (Ionis, Alnylam, and PTC respectively), and then smaller labs like uniQure and Wave Life Sciences do too. Novartis have already dropped $1bn on the partnership with a committed $2b more. In addition, there are a bunch of incentive schemes for diseases like HD: both the FDA and EMA have offered orphan-drug designation to therapies for HD, the FDA does expedited programmes and can offer RMAT designation for drugs like AMT-130.

With some luck (which is always in short supply for HD treatments, sadly), people with the disease might be able to get a single-injection treatment in the next 12 months[0].

0: https://en.hdbuzz.net/the-other-shoe-drops-uniqure-shares-pl...