RT Journal Article SR Electronic T1 Regulatory T-cell depletion in the setting of autologous stem cell transplantation for multiple myeloma: pilot study JF Journal for ImmunoTherapy of Cancer JO J Immunother Cancer FD BMJ Publishing Group Ltd SP e000286 DO 10.1136/jitc-2019-000286 VO 8 IS 1 A1 Benjamin A Derman A1 Yuanyuan Zha A1 Todd M Zimmerman A1 Rebecca Malloy A1 Andrzej Jakubowiak A1 Michael R Bishop MD A1 Justin Kline YR 2020 UL http://jitc.bmj.com/content/8/1/e000286.abstract AB Background Progression after high-dose melphalan with autologous stem cell transplantation (ASCT) in multiple myeloma (MM) may be due in part to immune dysfunction. Regulatory T (Treg) cells reconstitute rapidly after ASCT and inhibit immune responses against myeloma cells.Methods We performed a randomized study to evaluate two methods of Treg depletion in patients with MM undergoing ASCT. No Treg depletion was performed in the control ASCT arm. An anti-CD25 monoclonal antibody (basiliximab 20 mg IV) was administered on day +1 post-ASCT in the in vivo Treg depletion (IVTRD) arm. Tregs were depleted from autologous stem cell (ASC) grafts with anti-CD25 microbeads and the CliniMACS device in the ex vivo Treg depletion (EVTRD) arm.Results Fifteen patients were enrolled, five in each arm. The conditioning regimen was melphalan 200 mg/m2. Primary objectives included assessments of efficiency of IVTRD/EVTRD, kinetics of Treg depletion and recovery following ASCT, and safety. EVTRD removed 90% of CD4+CD25+ cells from ASC grafts. IVTRD and EVTRD led to reductions in Treg frequency between days +7 and +90 post-transplant compared with the control (p=0.007 and p<0.001, respectively).Conclusions IVTRD and EVTRD are feasible and significantly reduce and delay Treg recovery post-ASCT for MM, and serve as a platform for using post-transplant immunotherapies to improve post-ASCT outcomes.Trial registration number NCT01526096.