Low-dose total skin electron beam therapy combined with mogamulizumab for refractory mycosis fungoides and Sézary syndrome

Abstract Purpose Management of patients with refractory mycosis fungoides (MF) and Sezary syndrome (SS) is often challenging as available therapies lack durable response and consistent activity across disease compartments. Combining low-dose total skin electron beam therapy (LD-TSEBT) upfront with mogamulizumab could optimize the clinical outcome of these patients. LD-TSEBT is effective in clearing skin disease, and mogamulizumab is an anti-tumor immunotherapy with long-term tolerability suggesting its potential as a maintenance therapy after maximal response. We examine the combination regimen in previously treated SS patients. Methods Two patients with SS were treated with combination LD-TSEBT and mogamulizumab. Both patients received mogamulizumab 1mg/kg weekly x 4 and then bi-weekly; LD-TSEBT (12 Gy) was initiated within 2 days of starting mogamulizumab and given over 2-3 weeks. Safety and clinical response were evaluated. Results Total skin electron beam therapy plus mogamulizumab (TSE-Moga) was well-tolerated without any unanticipated adverse events. Patient 1 (T4N2bM0B2) is a 63 yo female with 4 prior systemic therapies; time to global response (TTR) with TSE-Moga was 9 weeks. Patient 2 (T4NxM0B2) is a 75 yo male with 5 prior systemic therapies; TTR was 4 weeks. Both patients lacked global response to their prior therapies but achieved global complete response (CR, blood and skin) with TSE-Moga. After a follow-up of 72 weeks and 43 weeks respectively, global CR continues. Conclusions TSE-Moga demonstrated excellent tolerability and promising clinical activity with ongoing global complete responses in two patients with refractory SS. This encouraging experience supports our ongoing clinical trial evaluating the efficacy and safety of TSE-Moga in MF and SS.