OBJECTIVES: To assess meaningful change on patient reported outcomes (PRO) for mogamulizumab versus vorinostat in a Phase 3 trial.

METHODS: Meaningful change for PRO endpoints were analyzed by group over time using a distribution-based method and standard effect size to establish meaningful change threshold (MCT). Calculated standard deviation (SD) of score change from baseline: standard error of mean = SD × [1 – reliability], where reliability was measured by Cronbach’s alpha. Subjects who improved, remained stable, or declined were compared by treatment group using the test of proportions or Fisher’s exact test.

RESULTS: For the Skindex-29, the difference in proportions of MCT categorical change from Baseline was significant (P < 0.05) at Cycle 3 (61.1% mogamulizumab subjects vs 45.3% vorinostat subjects categorized as improved), Cycle 5 (64.5% vs 42.4%), Cycle 7 (67.1% vs 47.5%), and Cycle 11 (84.1% vs 50.0%). For the FACT-G Physical Well-being domain, significant (P < 0.05) MCT differences were observed at Cycle 1 (19.3% vs 34.7% categorized as declined), Cycle 3 (17.4% vs 42.9%), Cycle 5 (13.1% vs 43.3%), and Cycle 7 (15.9% vs 37.5%); Total Score domain at Cycle 1 (9.1% vs 17.4% categorized as declined), Cycle 3 (8.3% vs 30.9%) and Cycle 5 (10.1% vs 30.5%); and Emotional Well-being domain at Cycle 3 (11.6% vs 24.5%) and Cycle 5 (14.1% vs 28.3%). For the EQ-5D-3L index score, the treatment groups had significant (P < 0.05) differences in proportions of MCT change category at Cycle 5 (42.6% vs 22.4% categorized as improved) and Cycle 11 (40.0% vs 30.0%). For the Pruritus Itchy Quality of Life (QoL) Emotions domain, significant (P < 0.05) differences of proportions were observed at Cycle 3 (57.9% vs 40.8% categorized as improved) and Cycle 5 (64.6% vs 44.1%).

CONCLUSIONS: Meaningful improvement was higher in subjects treated with mogamulizumab compared to vorinostat.