dynamics of immune cell reconstitution in allogeneic hematopoietic cell transplant patients receiving post transplant cyclophosphamide ptcy

In the setting of haploidentical hematopoietic cell transplantation (haplo-HCT), post-transplant cyclophosphamide (PTCy) selectively eliminates alloreactive T cells in-vivo, resulting in favorable graft versus host disease (GVHD), non-relapse mortality (NRM) and relapse outcomes. However, few studies have examined the impact of PTCy on immune reconstitution (IR). We quantified IR in 63 patients after haplo-HCT with PTCy, mofetil mycophenolate and tacrolimus (TAC) and compared results to 93 patients with 8/8 HLA matched related or unrelated donors (MD) receiving TAC, methotrexate and sirolimus for GVHD prophylaxis. Both groups received reduced intensity conditioning for hematologic malignancies. The median age of the Haplo-PTCy and MD cohorts was 55 and 57 years. Patient samples were analyzed using multi-color flow cytometry panels to characterize distinct lymphocyte populations. All IR values are expressed as median absolute cell count per μL. One month after HCT, recovery of all T cell subsets (CD3, CD4Tcon, Treg, CD8) was significantly reduced in the PTCy cohort compared to MD (Figure A, B, C). Recovery of CD4Tcon was also reduced at 2 and 3 months after PTCy (p NK cells were lower 1 month after PTCy (52.7 vs 91.1, p=0.08), but were significantly higher at 2, 3 and 6 months (153.4 vs 94.8, p=0.001, 153.7 vs 87.5, p=0.008, 180 vs 102, p=0.01, respectively, Figure D) compared to the MD cohort. Delayed NK cell recovery at 1 month after PTCy was due entirely to reduced numbers of CD56dim NK cells (Figure E). Subsequently recovery of CD56dim NK cells was similar in both cohorts. Recovery of CD56bright NK cells was significantly increased in the PTCy cohort (p Consistent with prior reports, 1 year cumulative incidence of extensive cGvHD was lower in the PTCy cohort compared to the MD cohort, 13% (5-26%, 95% CI) and 40% (30-50%, 95% CI) respectively, p=0.003, without increased NRM (p=0.28) or relapse (p=0.17). In summary, the effect of PTCy on IR was most pronounced 1 month after transplant with significantly delayed recovery of CD3, CD4Tcon, Treg, CD8 and CD56dim NK cells. Slow recovery of CD4Tcon persisted for 3 months and delayed recovery of Treg persisted for 1 year. Beginning 2 months after HCT, recovery of both CD56dim and CD56bright NK cells was more rapid in the PTCy cohort. Further studies will examine the effects of these differences in IR on clinical outcomes such as relapse, infections and GVHD

Comprehensive immunophenotyping of solid tumor-infiltrating immune cells reveals the expression characteristics of LAG-3 and its ligands

BackgroundImmune cell expression profiling from patient samples is critical for the successful development of immuno-oncology agents and is useful to understand mechanism-of-action, to identify exploratory biomarkers predictive of response, and to guide treatment selection and combination therapy strategies. LAG-3 is an inhibitory immune checkpoint that can suppress antitumor T-cell responses and targeting LAG-3, in combination with PD-1, is a rational approach to enhance antitumor immunity that has recently demonstrated clinical success. Here, we sought to identify human immune cell subsets that express LAG-3 and its ligands, to characterize the marker expression profile of these subsets, and to investigate the potential relationship between LAG-3 expressing subsets and clinical outcomes to immuno-oncology therapies.MethodsComprehensive high-parameter immunophenotyping was performed using mass and flow cytometry of tumor-infiltrating lymphocytes (TILs) and peripheral blood mononuclear cells (PBMCs) from two independent cohorts of samples from patients with various solid tumor types. Profiling of circulating immune cells by single cell RNA-seq was conducted on samples from a clinical trial cohort of melanoma patients treated with immunotherapy.ResultsLAG-3 was most highly expressed by subsets of tumor-infiltrating CD8 T central memory (TCM) and effector memory (TEM) cells and was frequently co-expressed with PD-1. We determined that these PD-1+ LAG-3+ CD8 memory T cells exhibited a unique marker profile, with greater expression of activation (CD69, HLA-DR), inhibitory (TIM-3, TIGIT, CTLA-4) and stimulatory (4-1BB, ICOS) markers compared to cells that expressed only PD-1 or LAG-3, or that were negative for both checkpoints. In contrast to tumors, LAG-3 expression was more limited in circulating immune cells from healthy donors and solid tumor patients. Additionally, we found abundant expression of the LAG-3 ligands MHC-II and galectin-3 in diverse immune cell types, whereas FGL1 and LSECtin were minimally expressed by immune cells in the tumor microenvironment (TME). Lastly, we found an inverse relationship between baseline and on-treatment levels of circulating LAG3 transcript-expressing CD8 memory T cells and response to combination PD-1 and CTLA-4 blockade in a clinical trial cohort of melanoma patients profiled by scRNAseq.ConclusionsThese results provide insights into the nature of LAG-3- and ligand-expressing immune cells within the TME, and suggest a biological basis for informing mechanistic hypotheses, treatment selection strategies, and combination immunotherapy approaches to support continued development of dual PD-1 and LAG-3 blockade

Bortezomib-based immunosuppression after reduced-intensity conditioning hematopoietic stem cell transplantation: randomized phase II results

Aprior phase I/II trial of bortezomib/tacrolimus/methotrexate prophylaxis after human leukocyte antigen (HLA)-mismatched reduced intensity conditioning allogeneic hematopoietic stem cell transplantation documented low acute graft-versus-host disease incidence, with promising overall and progression-free survival. We performed an open-label three-arm 1:1:1 phase II randomized controlled trial comparing grade II–IV acute graft-versus-host disease between conventional tacrolimus/methotrexate (A) versus bortezomib/tacrolimus/methotrexate (B), and versus bortezomib/sirolimus/tacrolimus (C), in reduced intensity conditioning allogeneic transplantation recipients lacking HLA-matched related donors. The primary endpoint was grade II–IV acute graft-versus-host disease incidence rate by day +180. One hundred and thirty-eight patients (A 46, B 45, C 47) with a median age of 64 years (range: 24–75), varying malignant diagnoses and disease risk (low 14, intermediate 96, high/very high 28) received 7–8/8 HLA-mismatched (40) or matched unrelated donor (98) grafts. Median follow up in survivors was 30 months (range: 14–46). Despite early immune reconstitution differences, day +180 grade II-IV acute graft-versus-host disease rates were similar (A 32.6%, B 31.1%, C 21%; P=0.53 for A vs. B, P=0.16 for A vs. C). The 2-year non-relapse mortality incidence was similar (A 14%, B 16%, C 6.4%; P=0.62), as were relapse (A 32%, B 32%, C 38%; P=0.74), chronic graft-versus-host disease (A 59%, B 60% C 55%; P=0.66), progression-free survival (A 54%, B 52%, C 55%; P=0.95), and overall survival (A 61%, B 62%, C 62%; P=0.98). Overall, the bortezomib-based regimens evaluated did not improve outcomes compared with tacrolimus/methotrexate therapy. clinicaltrials.gov Identifier: 0175438