Poster Presentation MIN Spring Retreat 2023

Novel pre-conditioning regimens prior to adoptive immunotherapy in mice (#103)

Joanne E Davis 1 2 3 , Mandy Ludford-Menting 1 2 , Rachel Koldej 1 2 , David S Ritchie 1 2 4
  1. ACRF Translational Research Laboratory, The Royal Melbourne Hospital, Parkville, VIC, Australia
  2. Department of Medicine, The University of Melbourne, Melbourne, VIC, Australia
  3. Melbourne Health, Parkville, VIC, Australia
  4. Clinical Haematology and Bone Marrow Transplantation Service, Department of Clinical Oncology and Haematology, The Royal Melbourne Hospital, Melbourne, VIC, Australia

Background:

Prior to receiving adoptive immunotherapy of CAR T cells, patients are pre-conditioned to “create space” for the expansion of infused T cells.  Treatment typically consists of low dose radiation or fludarabine and cyclophosphamide preconditioning chemotherapy, but this is associated with infection and haematological toxicity.  We investigated if using the novel preconditioning regimen of the Bcl-2 inhibitor venetoclax, or the JAK1/2 inhibitor ruxolitinib in combination with reduced intensity conditioning (RIC) irradiation in a congenic mouse model could improve donor T cell homeostatic proliferation.

Methods:

Murine adoptive therapy models were established in C57BL/6 (CD45.2+) mice, which were pre-treated by oral gavage with venetoclax (100 mg/ml) once daily or ruxolitinib (180 mg/ml) twice daily, for two days.  Mice were then irradiated with 2 x 400 cGy RIC on day 0.  Splenic T cells purified from congenic B6.SJL-Ptprc<a>Pepc<b>Boy (CD45.1+) mice were labelled with cell trace violet, and 5e6 T cells injected i.v.  Mice were killed 7-14 days later, and the spleen and inguinal lymph nodes (LN) harvested to isolate T cells, which were analysed by spectral cytometry for proliferation and memory phenotype.

Results:

Pre-conditioning with ruxolitinib or venetoclax transiently depleted CD4+ and CD8+ naïve and central memory T cells and NK cells in adoptive immunotherapy recipients. RIC treatment allowed congenic donor T cells to expand significantly in both the spleen and LN, as assessed using cell trace violet proliferation.  Combining either ruxolitinib or venetoclax pre-conditioning with RIC improved homeostatic donor T cell migration to the LN, with an increased central memory phenotype.

Summary:

Novel pre-conditioning regimens using Bcl-2 or JAK1/2 inhibitors in combination with RIC may increase the expansion and persistence of CAR T cells and enhance their homeostatic migration to peripheral LN, for improved secondary recall responses.