Impact of blood involvement on efficacy and time to response with mogamulizumab in mycosis fungoides and Sézary syndrome

BACKGROUND: Cutaneous T‐cell lymphomas (CTCL) are rare types of non‐Hodgkin lymphoma, which present in skin. Mycosis fungoides (MF) and Sézary syndrome (SS) are subtypes which make up two‐thirds of all CTCL cases. The phase 3 MAVORIC study (NCT01728805) compared mogamulizumab to vorinostat in MF and SS patients, with post hoc data showing a trend for higher efficacy in mogamulizumab‐treated patients as baseline blood tumour burden increases. OBJECTIVES: The aim of this study was to use updated post hoc analyses in order to examine the efficacy of mogamulizumab and vorinostat in MF patients when stratified by baseline blood involvement and to determine what factors affect time‐to‐global and time‐to‐skin response to inform clinical follow‐up. METHODS: Post hoc analyses were carried out using data from MAVORIC. Overall response rate (ORR), progression‐free survival (PFS) and time‐to‐next‐treatment (TTNT) data were used to assess efficacy in patients with MF. Time‐to‐global response (TTR) was examined by disease subtype, by blood involvement in MF patients, and time‐to‐skin response was examined by blood involvement in MF patients. RESULTS: Numerically superior results were seen for ORR, PFS and TTNT in mogamulizumab‐treated patients with MF compared with vorinostat, with a trend for outcomes improving with increasing baseline blood class. Statistically significant results for mogamulizumab compared with vorinostat were seen for MF B1 pts for PFS (8.43 vs. 2.83 months, p = 0.003) and TTNT (11.9 vs. 3.13 months, p = 0.002), and for MF B2 pts for ORR (46.2 vs. 9.1 months, p = 0.033). CONCLUSIONS: In mogamulizumab‐treated MF patients, ORR and PFS were seen to improve with increasing blood involvement, which led to improved TTNT. TTR was more predictable for mogamulizumab‐treated MF patients with blood involvement, and skin response may take longer than previously reported in some patients.