This is a randomized, subject and investigator-blinded, placebo controlled, crossover, multi-center Proof of Concept (PoC) study with in-house simulated laboratory night shifts in patients with SWD. This non-confirmatory study will include two treatment arms: LML134 and placebo. After a screening period, the treatment phase of the study will consist of two overnight stays in a sleep lab in each of two treatment periods, with a minimum one week wash-out in between.