There were two people diagnosed with ALS in my family. The ALS clinic (in France) provided only minimal services or information.
After two years studying ALS research papers, I am not even sure that familial ALS means something related to some of the 126 “ALS genes” [0].
In my opinion “inheritable ALS” does not means that there is an “ALS gene”, even in the case of C9orf72 (which is anyway an ORF [1], not a gene).
My opinion is that clinical trials have too stringent rules for diseases like ALS, as past phase III clinical trials have been declared failed for drugs that brought some improvement, unfortunately at the cost of side effects.
It would have been better to try to mitigate those side effects, than to stop the research entirely (usually if a phase III failed it is very difficult for a biotech to fund further research).
Caveat lector: I am not a doctor nor a scientist.
[0] https://alsod.ac.uk/
[1] https://en.wikipedia.org/wiki/Open_reading_frame