Transplantation Research

Autologous hematopoietic stem cell transplantation (ASCT) is a standard-of-care treatment for many hematologic malignancies. Progression of disease after ASCT is the primary cause of treatment failure. In this Phase Ib trial, we studied the safety and clinical effect of combined checkpoint inhibition therapy (CPIT) with ipilimumab and nivolumab as a consolidation strategy after ASCT for patients with high-risk diffuse large B cell lymphoma (DLBCL), mature T cell lymphoma (TCL), and multiple myeloma (MM). Starting at 14 to 28 days after ASCT, patients received ipilimumab (1 mg/kg i.v. on day 1 of weeks 1, 4, 7, 10, 16, and 22) and nivolumab (3 mg/kg i.v. on day 1 of weeks 1, 4, 7, 10, 12, 14, 16, 18, 20, 22, 24, and 26). Patients received a median of 5 doses of ipilimumab and 8 doses of nivolumab. Thirty-five patients were included in the intent-to-treat population. Ninety-four percent of the patients experienced immune-related adverse events (irAEs) of any grade. Ninety-seven percent of irAEs resolved spontaneously or after holding study drugs and instituting high-dose corticosteroid therapy. Progression-free and overall survival at 18 months post-ASCT for each disease cohort were 85.7% and 100% for primary refractory DLBCL, 28.6% and 57.1% for relapsed DLBCL, not evaluable and 80% for frontline TCL, 25% and 75% for relapsed TCL, 57.1% and 87% for high-risk transplant-naïve MM, and 40% and 100% for MM relapsed within 3 years of first ASCT. We conclude that combined CPIT appears to be tolerable as a consolidation strategy after ASCT and in addition to the potential clinical efficacy observed in some subsets of disease, T cell receptor repertoire, T regulatory cell phenotype, and gut microbiota profiles provide a biologic rationale warranting further study of this approach.

Viral infections, such as with cytomegalovirus (CMV), remain a major risk factor for mortality and morbidity of transplant recipients because of their requirement for lifelong immunosuppression (IS). Antiviral drugs often cause toxicity and sometimes fail to control disease. Thus, regeneration of the antiviral immune response by adoptive antiviral T cell therapy is an attractive alternative. Our recent data, however, show only short-term efficacy in some solid organ recipients, possibly because of malfunction in transferred T cells caused by ongoing IS. We developed a vector-free clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9-based good manufacturing practice (GMP)-compliant protocol that efficiently targets and knocks out the gene for the adaptor protein FK506-binding protein 12 (FKBP12), required for the immunosuppressive function of tacrolimus. This was achieved by transient delivery of ribonucleoprotein complexes into CMV-specific T cells by electroporation. We confirmed the tacrolimus resistance of our gene-edited T cell products in vitro and demonstrated performance comparable with non-tacrolimus-treated unmodified T cells. The alternative calcineurin inhibitor cyclosporine A can be administered as a safety switch to shut down tacrolimus-resistant T cell activity in case of adverse effects. Furthermore, we performed safety assessments as a prerequisite for translation to first-in-human applications.

The majority of patients with refractory, advanced-stage mycosis fungoides (MF) or Sézary syndrome (SS) have a life expectancy of <5 years. Here, we report a phase 2 study of a novel nonmyeloablative allogeneic transplantation strategy tailored for this patient population. This study has completed the enrollment, and 35 patients (13 MF, 22 SS) have undergone transplant as planned. The majority (80%) of the patients had stage IV disease and received multiple previous systemic therapies. All patients had active disease at the time of conditioning using total skin electron beam therapy, total lymphoid irradiation, and antithymocyte globulin, and received allograft infusion as outpatients. Cyclosporine or tacrolimus and mycophenolate mofetil were used for graft-versus-host disease (GVHD) prophylaxis. Patients tolerated the transplant well, with 1- and 2-year nonrelapse mortality of 3% and 14%, respectively. The day +180 cumulative incidence of grade 2 to 4 acute GVHD was 16%, and the 2-year incidence of moderate/severe chronic GVHD was 32%. With a median posttransplant follow-up of 5.4 years, the 2-, 3-, and 5-year overall survival rates were 68%, 62%, and 56%. Using high-throughput sequencing of the T-cell receptor for minimal residual disease monitoring, we observed that 43% achieved molecular remission, which was associated with a lower incidence of disease progression or relapse (9% vs 87%; P = .02). Our study also showed that patients who were aged ≥65 years at the time of allotransplant had similar clinical outcomes compared with younger patients. Thus, we have developed an alternative and potentially curative nonmyeloablative allogeneic transplant regimen for patients with advanced stage MF/SS. This trial was registered at www.clinicaltrials.gov as #NCT00896493.

Restoration of T cell repertoire diversity after allogeneic bone marrow transplantation (allo-BMT) is crucial for immune recovery. T cell diversity is produced by rearrangements of germline gene segments (V (D) and J) of the T cell receptor (TCR) α and β chains, and selection induced by binding of TCRs to MHC-peptide complexes. Multiple measures were proposed for this diversity. We here focus on the V-gene usage and the CDR3 sequences of the beta chain. We compared multiple T cell repertoires to follow T cell repertoire changes post-allo-BMT in HLA-matched related donor and recipient pairs. Our analyses of the differences between donor and recipient complementarity determining region 3 (CDR3) beta composition and V-gene profile show that the CDR3 sequence composition does not change during restoration, implying its dependence on the HLA typing. In contrast, V-gene usage followed a time-dependent pattern, initially following the donor profile and then shifting back to the recipients' profile. The final long-term repertoire was more similar to that of the recipient's original one than the donor's; some recipients converged within months, while others took multiple years. Based on the results of our analyses, we propose that donor-recipient V-gene distribution differences may serve as clinical biomarkers for monitoring immune recovery.