Phase I Studies of Cellular Immunotherapy Using Central Memory Derived-CD19-Specific T Cells Following Autologous Stem Cell Transplantation for Patients with High-Risk Intermediate Grade B-Lineage Non-Hodgkin Lymphoma

Introduction

Efforts to improve the survival of non-Hodgkin lymphoma (NHL) patients with recurrent disease have focused primarily on the use of consolidative myeloablative autologous hematopoietic stem cell transplantation (HSCT). However, the major limitation of HSCT for NHL is the high incidence of relapse, even at maximally tolerated preparative regimen intensities. In a series of phase I studies designed to improve HSCT longterm remission rates, we have assessed the safety and feasibility of cellular immunotherapy utilizing ex vivo expanded autologous central memory (Tcm)-enrichedT cells that are genetically modified to express CD19-specific chimeric antigen receptors (CD19CAR), given in conjunction with standard of care myeloablative HSCT.

Methods

Here we present results from the first two studies investigating different starting cell populations and CAR constructs. The NHL1 trial utilized a starting population of CD8+ Tcm and transduced with a lentiviral vector encoding the 1st-generation CD19CAR (CD19R:zeta), consisting of a CD19-specific scFv linked to a CD3-zeta (CD19R:zeta) signaling domain. The NHL2 trial used a bulk Tcm population including both CD4+ and CD8+cells, which were transduced with lentiviral vectors encoding a 2nd-generation CD19CAR that added a CD28 costimulatory domain (CD19R:CD28:zeta) and a selectable marker for cell tracking (EGFRt). Engineered Tcm-derived CD19CAR T cells were infused 2 days after HSCT at dose levels of 25-200 x10^6 CAR T cells (dose levels in table), and all participants were followed for dose limiting toxicity (DLT) for 28 days. Both phase I studies utilized the target equivalence range design, which defines the dose escalation and de-escalation rules for determining maximum tolerated dose based on a target range of acceptable toxicity.

Results

NHL1 protocol (NCT01318317): Eight participants were consented and received CD8+ Tcm -derived CD19R:zeta T cell therapy. Seven patients had a diagnosis of diffuse large B cell lymphoma (DLBCL) and 1 had mantle cell lymphoma (MCL). Four of the 8 were female, and 3/8 were ≥ age 65 years. The mean age was 62 years (50-75). The median number of prior chemo/immunotherapy regimens was 3 (2-4). Two of the 8 (25%) participants had prior radiation. Five of 8 (63%) participants on NHL1 achieved a best response of CR or continuing CR. Four of 8 (50% 95% CI [16%, 84%]) participants have progressed. The progression free survival (PFS) at both 1 and 2 years is 50%, 95% CI[16%,84%] with a median follow-up of 24.7 (min=24.0, max=26.7) months. There were 2 deaths, both from disease progression.

NHL2 protocol (NCT 01815749): Eight participants were consented and received Tcm-derived CD19R:CD28:zeta/EGFRt T cell therapy. Four patients had MCL, 4 had DLBCL, 3/8 were female, 2/8 were ≥ age 65 years. The mean age was 58 years (23-71). The median number of prior chemo/immunotherapy regimens was 2 (1-3). All eight NHL2 participants achieved a best response of CR or continuing CR. The PFS at 6 months is 100%, 95% CI[63%, 100%] with a median follow-up of 12.2 (min=10.0, max=14.1) months. To date 2 participants of the 8 (25%, 95% CI [3%, 65%]) have progressed (one at 6.4 months and one at 12.6 months). There was 1 death from disease progression.

Both NHL1 and NHL2 trials demonstrated safety and feasibility. There were no DLTs, delayed hematopoietic reconstitution, or non-relapse mortality on either study. In NHL2, we employed bulk Tcm including both CD4+ and CD8+ cells in the CAR transduction and also added a CD28 co-stimulatory domain in the CAR design, to enhance persistence and antitumor activity. NHL2 exhibited better CAR T cell persistence compared to NHL1 T cell therapy based on area under the curve of log₁₀copies/µg of genomic DNA from day 1 to 25 post infusion (mean difference = 14.8, 95% CI [7.4, 22.3], P<0.001) based on analysis of WPRE PCR data.

Conclusions

We conclude that Tcm-derived CD19CAR T cell therapy is very safe for treatment of poor-risk NHL patients undergoing autologous HSCT. We continue follow-up of these patients long-term to assess efficacy, and preliminary data are promising. Meanwhile we are exploring CAR vector design and T cell population modifications to improve the duration of anti-tumor immunity in the setting of immune reconstitution following engineered autograft.