This is a phase 3, multicenter, randomized, double-blind, placebo-controlled study of patients with advanced, recurrent and/or metastatic DDLS.~Patients will be randomized 1:1 between abemaciclib and placebo and followed for disease progression. For those patients with progression of disease (by RECIST) on placebo, crossover to active drug will be offered to patients if they remain eligible for the clinical trial in all other respects. Unblinding and crossover is only allowed for radiographic progression (not clinical progression). Real-time radiology review by the treating physician will allow for rapid crossover for patients with progression on placebo. If patients are deemed to have disease that is too rapidly progressive to be considered for a randomized, double-blind, placebo-controlled clinical trial, they should be excluded from consideration.
This is a Phase 3 randomized double-blind study of abemaciclib versus placebo. Patients with progression of disease will cross over to open label abemaciclib.