The Final Charge , Phase I/II MND Results & FDA ODD Approval Catalyst, page-664

That would potentially alter the bioavailability of the drug- so a no go for early trialling.
@Boffin99 one would think that PAA will only test existing tablet this time around. As above, the liquid will need to be trialled for different bioavailability, which may muddy the upcoming trial.
Secondly, any success with liquid will deserve its own patents and will serve to further extend market exclusivity, hence strateigically it is best to do this a bit later (balance between nearterm revenue and patent life)
Thirdly, liquid would be for those with late stage MND. Ie. Very "far gone" people likely in bad shape. Itvis usually best to have relatively healthy patients in a trial where they have a better chance of their own body responding to treatment. This is what brought the doggy trial unstuck, I doubt management will make same mistake twice So at this early stage, I assume they will avoid the far gone folk and for now just get the tablet formulation past FDA.