Pre-Emptive Donor Lymphocyte Infusion with CD19-Directed, CAR-Modified T Cells Infused after Allogeneic Hematopoietic Cell Transplantation for Patients with Advanced CD19⁺ Malignancies

Background: Allogeneic hematopoietic cell transplantation (HCT) can be curative in a subset of patients with advanced lymphoid malignancies but relapse remains a major reason for treatment failure. Donor-derived, non-specific lymphocyte infusions (DLI) can confer an immune anti-malignancy effect but can be complicated by graft-versus-host-disease (GVHD). Chimeric antigen receptor (CAR)-modified T cells directed toward CD19 have demonstrated dramatic efficacy in patients with refractory ALL and NHL. However, responses are often associated with life-threatening cytokine release syndrome.

Aim: We hypothesized that infusing CAR-modified, CD19-specific T-cells after HCT as a directed DLI would be associated with a low rate of GVHD, better disease control, and a less severe cytokine release syndrome since administered in a minimal disease state.

Methods: We employed a non-viral gene transfer using the Sleeping Beauty (SB) transposon/transposase system to stably express a CD19-specific CAR (designated CD19RCD28 that activates via CD3z & CD28) in donor-derived T cells for patients with advanced CD19⁺ lymphoid malignancies. T-cells were electroporated using a Nucleofector device to synchronously introduce two DNA plasmids coding for SB transposon (CD19RCD28) and hyperactive SB transposase (SB11). T-cells stably expressing the CAR were retrieved over 28 days of co-culture by recursive additions of g-irradiated activating and propagating cells (AaPC) in presence of soluble recombinant interleukin (IL)-2 and IL-21. The AaPC were derived from K562 cells and genetically modified to co-express CD19 as well as the co-stimulatory molecules CD86, CD137L, and a membrane-bound version of IL-15.

Results: To date, we have successfully treated 21 patients with median age 36 years (range 21-62) with advanced CD19⁺ ALL (n=18) or NHL (n=3); 10 patients had active disease at time of HCT. Donor-derived CAR⁺ T cells (HLA-matched sibling n=10; 1 Ag mismatched sibling n=1; haplo family n=8; cord blood n=2) were infused at a median 64 days (range 42-91 days) following HCT to prevent disease progression. Transplant preparative regimens were myeloablative, busulfan-based (n=10) or reduced intensity, fludarabine-based (n=11). All patients were maintained on GVHD prophylaxis at time of CAR T-cell infusion with tacrolimus, plus mycophenolate mofeteil for cord, plus post-HCT cyclophosphamide for haplo donors. The starting CAR⁺ T-cell dose was 10⁶ (n=7), escalated to 10⁷ (n=6), 5x10⁷ (n=5), and currently at 10⁸ (n=3) modified T cells/m² (based on recipient body surface area). Patients have not demonstrated any acute or late toxicity to CAR⁺ T cell infusions. Three patients developed acute grades 2-4 GVHD (liver n=1, upper GI n=1, skin=1) which was within the expected range after allogeneic HCT alone. Of note, the rate of CMV reactivation after CAR T cell infusion was 24% vs. 41 % previously reported for our patients without CAR T cell infusion (Wilhelm et al. J Oncol Parm Practice, 2014, 20:257). Nineteen patients have had at least 30 days follow-up post CAR T-cell infusion and are evaluable for disease progression. Forty-eight percent of patients (n=10) remain alive and in complete remission (CR) at median 5.2 months (range 0-21.3 months) following CAR T cell infusion. Importantly, among 8 patients who received haplo-HCT and CAR, 7 remain in remission at median 4.2 months.

Conclusion: We demonstrate that infusing donor-derived CD19-specific CAR⁺ T cells, using the SB and AaPC platform, in the adjuvant HCT setting as pre-emptive DLI may provide an effective and safe approach for maintaining remission in patients at high risk for relapse. Graft-vs-host disease did not appear increased by administration of the donor derived CAR-T cells. Furthermore, the add-back of allogeneic T cells appears to have contributed to immune reconstitution and control of opportunistic viral infection.