Huntington?s disease suffer Jack, has discovered a power in which can prevent the death of his closest friend Gracie, he must defeat the odds and find a way to communicate or have to witness her deteriorate in front of him.

I feel perhaps it is a little bit too long. remember strong loglines often start with when, after, as. Also alot of people will not know what Huntington’s disease is and therefore will not be able to understand why jack is unable to communicate with gracie.

perhaps something like this?
“After jack discovers a power which will prevent the death of his closest friend, but first he must overcome his own illness in order to save her.”

good luck