XIAP and amyotrophic lateral sclerosis: Therefore, by the use of X-linked apoptotic inhibitor (XIAP), a new relevant role of caspase-9 was elucidated in ALS [135]; or, by using the pan caspase inhibitor Z-VAD-FMK, a new role for caspase activation as a potential route rather than an obligatory initiation step of tubulin associated unit (TAU) aggregation was defined in AD [136].