Adoptive Transfer of Ex Vivo Costimulated Autologous T-Cells in Conjunction with Pneumococcal Conjugate Vaccine Immunizations Accelerates Post-Transplant T-Cell Recovery after Autotransplantation for Myeloma: Results of a Randomized Study.

Ex-vivo co-stimulation of autologous T-cells with anti-CD3/anti-CD28-conjugated magnetic beads followed by adoptive transfer may augment T-cell responses toward tumor antigens or infectious agents. 54 patients (pts) were treated with ex-vivo co-stimulated autologous T-cells after autotransplantation for myeloma. The median age was 56 (range 38–71), 67% were male, 20% were African-American, 22% had IgA paraproteins, 11% had del 13 or complex karyotypes and the median β₂m level at diagnosis was 3.31 mg/L (range 1.09–73.7). After lymphocyte collections, pts received cyclophosphamide (4.5 g/m²) + G-CSF for stem cell mobilization, and high dose melphalan (200 mg/m² or 140 mg/m² for pts ≥ 70) for conditioning. T-cells were cultured for ~12 days with anti-CD3/anti-CD28-immobilized immunomagnetic beads + IL-2 supplementation (100 units/ml). During a run-in phase, 12 pts received co-stimulated T-cells post-transplant ( day +12) alone. In a second phase, 42 pts who participated in a 2 x 2 randomization, received T-cells either early (day +12) or late (day + 100) after transplant. These pts also received either 2 immunizations with the pneumococcal conjugate vaccine (PCV, Prevnar) at days +30, +90 or 3 immunizations (prior to T-cell collection, at days + 30, + 90) to test immune responses to a well-defined antigen. 42 pts received PCV immunizations with no grade 3/4 adverse events. Anti-pneumococcal antibody responses developed in 51% of 31 pts tested thus far. Details of these studies will be presented separately. 52 pts received a mean dose of 8.04 x 10⁹ costimulated T-cells (range 1.6–11). Infusion-related adverse effects included grade I–II rigors/chills (40%), grade I–II facial/upper body rashes (12%) at a median of 13 days after T-cells, grade I cardiovascular events (10%), grade I–III hypoxia (5%), grade II fever (5%), and 1 episode of DVT. At T-cell harvesting, the mean % of CD3 + cells in culture was 94.8%, the mean T-cell doubling level was 4.81 (28-fold expansion). Among the 42 randomized pts, at day + 42 post-transplant ( 30 days after T-cell infusion for the early groups), the median CD4/CD3 count was 462/mcl (range 202–1439) for the early T-cell recipients vs 230/mcl (range 50–915) for the late T-cell recipients (T-cells not yet infused) [P=0.004]. The median CD8/CD3 counts were 1399/mcl (range 465–2810) vs 1084/mcl (range 103–3422) for the early and late T-cell recipients respectively at day +42 [P=0.04]. For clinical responses there were 11 CRs, 22 VGPRs ( 90% reduction in paraprotein levels), 18 PRs (50–90% reductions), 2 pts had no response and 1 pt was unevaluable. 2 pts had delayed reductions in M-protein levels of ~ 50% between day 42 and day 180 or 270. For the entire cohort, the probability of overall survival at 1.5 years was 78% [95%CI 64%–92%]. Infusions of ex-vivo expanded autologous T-cells are well-tolerated and associated with accelerated T-cell recovery early after autotransplantation. This study may provide a platform for combining costimulated T-cells and tumor vaccines in the autograft setting.