In general you are correct about how patents work. This patent isn't for Eltroprazine, it is for a method that will be used to administer Eltroprazine. I didn't research the names listed on the patent but maybe that is how it ties back to AMBS and Eltroprazine.
"The patent covers methods for the administration of eltoprazine, in combination with the anti-Parkinson's drug, levodopa (L-DOPA), for the treatment of Parkinson's disease."