Effect of plasmapheresis on ATG (Thymoglobulin) clearance prior to adoptive T cell transfer.

The effect of anti-thymocyte globulin (ATG) on the outcome of hematopoietic stem cell transplantation (SCT) is dependent on formulation, dose and exposure. However, ATG levels are not routinely measured and therapeutic levels are not well defined. In ex vivo T cell-deplete SCT, the potential effect of residual ATG has important implications on the timing of adoptive T cell transfer. Here we measured active rabbit ATG concentration using a flow cytometry-based method that can be implemented in any laboratory. Three adult patients received 6 mg/kg Thymoglobulin over 4 days, leading to peak plasma active ATG concentration of 20.8 ± 1.4 µg/mL, suggesting volume of distribution of 16-19 L. The half-life of active ATG was 6.1 ± 0.7 days and plasmapheresis at Day 25 ± 1 post-transplant reduced mean plasma concentration from 1.25 to 0.61 µg/mL. Total ATG and active ATG do not have a constant relationship because of differences in volumes of distribution and half-lives. Thymoglobulin can mediate antibody-dependent cell-mediated cytotoxicity (ADCC) in vitro at concentrations as low as 0.03 µg/mL, with a log-linear relationship between ATG concentration and ADCC. Plasmapheresis can remove ATG but likely has modest biological impact when performed 4 weeks after 6 mg/kg ATG.

Phase I Trial of Inducible Caspase 9 T Cells in Adult Stem Cell Transplant Demonstrates Massive Clonotypic Proliferative Potential and Long-term Persistence of Transgenic T Cells.

PURPOSE: Inducible caspase 9 (iCasp9) is a cellular safety switch that can make T-cell therapy safer. The purpose of this phase I trial was to investigate the use of iCasp9-transduced T-cell addback in adult patients undergoing haploidentical stem cell transplantation for high-risk hematologic malignancies. PATIENTS AND METHODS: Patients undergoing myeloablative, CD34-selected haploidentical stem cell transplantation were treated with 0.5-1.0 × 106/kg donor-derived iCasp9-transduced T cells on day +25 or 26 post-transplant, with additional doses allowed for disease relapse, infection, or mixed chimerism. RESULTS: Three patients were enrolled. iCasp9-transduced T cells were readily detectable by 4 weeks post-infusion in all patients and remained at high level (114 cells/µL, 11% of T cells) in 1 patient alive at 3.6 years. One patient developed donor-derived Epstein-Barr virus-associated post-transplant lymphoproliferative disease (EBV-PTLD), which was followed by a marked expansion of iCasp9 T cells and cytokine release syndrome (CRS). These iCasp9-transduced T cells infiltrated the affected lymph nodes and secreted IFNγ and IL-10. They peaked at 1,848 cells/µL and were found to be monoclonal by T-cell receptor (TCR) clonotype and oligoclonal by viral integrant analysis, representing a 6-log in vivo expansion of the dominant T-cell clone. These T cells were not autonomous and contracted with the resolution of EBV-PTLD, which did not recur. CONCLUSIONS: iCasp9-transduced T cells could persist long-term. They retained very high in vivo clonotypic proliferative capacity and function, and could cause CRS in response to de novo lymphoma development.

Addition of interleukin-6 inhibition with tocilizumab to standard graft-versus-host disease prophylaxis after allogeneic stem-cell transplantation: a phase 1/2 trial.

BACKGROUND: Interleukin 6 mediates graft-versus-host disease (GVHD) in experimental allogeneic stem-cell transplantation (allogeneic SCT) and represents an attractive therapeutic target. We aimed to assess whether the humanised anti-interleukin-6 receptor monoclonal antibody, tocilizumab, could attenuate the incidence of acute GVHD. METHODS: We undertook a single-group, single-institution phase 1/2 study at the Royal Brisbane and Women's Hospital Bone Marrow Transplantation unit, QLD, Australia. Eligible patients were 18-65 years old and underwent T-replete HLA-matched allogeneic SCT with either total body irradiation-based myeloablative or reduced-intensity conditioning from unrelated or sibling donors. One intravenous dose of tocilizumab (8 mg/kg, capped at 800 mg, over 60 mins' infusion) was given the day before allogeneic SCT along with standard GVHD prophylaxis (cyclosporin [5 mg/kg per day on days -1 to +1, then 3 mg/kg per day to maintain therapeutic levels (trough levels of 140-300 ng/mL) for 100 days plus methotrexate [15 mg/m(2) on day 1, then 10 mg/m(2) on days 3, 6, and 11]). The primary endpoint was incidence of grade 2-4 acute GVHD at day 100, assessed and graded as per the Seattle criteria. Immunological profiles were compared with a non-randomised group of patients receiving allogeneic SCT, but not treated with tocilizumab. This trial is registered with the Australian and New Zealand Clinical Trials Registry, number ACTRN12612000726853. FINDINGS: Between Jan 19, 2012, and Aug 27, 2013, 48 eligible patients receiving cyclosporin and methotrexate as GVHD prophylaxis were enrolled into the study. The incidence of grade 2-4 acute GVHD in patients treated with tocilizumab at day 100 was 12% (95% CI 5-24), and the incidence of grade 3-4 acute GVHD was 4% (1-13). Grade 2-4 acute GVHD involving the skin developed in five (10%) patients of 48 treated with tocilizumab, involving the gastrointestinal tract in four (8%) patients; there were no reported cases involving the liver. Low incidences of grade 2-4 acute GVHD were noted in patients receiving both myeloablative total body irradiation-based conditioning (12% [95% CI 2-34) and fludarabine and melphalan reduced-intensity conditioning (12% [4-27]). Immune reconstitution was preserved in recipients of interleukin-6 receptor inhibition, but qualitatively modified with suppression of known pathogenic STAT3-dependent pathways. INTERPRETATION: Interleukin 6 is the main detectable and dysregulated cytokine secreted after allogeneic SCT and its inhibition is a potential new and simple strategy to protect from acute GVHD despite robust immune reconstitution; a randomised, controlled trial assessing tocilizumab in addition to standard GVHD prophylaxis in these patients is warranted. FUNDING: National Health and Medical Research Council and Queensland Health.