Early Signals of Anti-Tumor Efficacy and Safety with Autologous CD5.CAR T-Cells in Patients with Refractory/Relapsed T-Cell Lymphoma

Introduction

We present results of a Phase I clinical trial (NCT03081910) of autologous T-cells expressing a CD5-specific chimeric antigen receptor (CD5.CAR) as therapy for refractory or relapsed (r/r) mature T-cell lymphoma (TCL). T-cells expressing an optimized second-generation, CD28-costimulated CD5.CAR resist fratricide by rapidly degrading CD5 protein and expand normally ex vivo. We evaluated the feasibility of manufacturing autologous CD5.CAR T-cells from patients with r/r peripheral or cutaneous TCL and the safety of these CD5.CAR T-cells as a bridging therapy to allogeneic hematopoietic stem cell transplant (alloHSCT). We also assessed anti-tumor activity and kinetics of in vivo expansion and persistence of CD5 CAR T-cells as well as their off-tumor activity against normal circulating T-cells.

Methods and patient characteristics

CD5.CAR T-cells were manufactured from PBMC using gammaretroviral transduction of T-cells following anti-CD3/anti-CD28 stimulation. Fourteen patients were enrolled, and we have treated nine patients (age 27-71, median 63) with mature TCL including cutaneous TCL (n=2), angioimmunoblastic TCL (AITL, n=2), peripheral TCL (n=4), and adult T-cell leukemia/lymphoma (n=1). All patients were eligible for alloHSCT and had an available donor. Median number of prior lines of therapy was 5 (2-18), and 5 patients had relapsed after autologous (n=3) or allogeneic HSCT (n=2).

Results

All patients received autologous CD5.CAR T-cells on one of three dose levels: two on dose level 1 (1x10 ⁷ CAR T cells/m ²), four on dose level 2 (5x10 ⁷ CAR T cells/m ²), and three on dose level 3 (1x10 ⁸ CAR T cells/m ²). Seven patients received a single dose of CD5.CAR T-cells following lymphodepleting chemotherapy (LDC) with cyclophosphamide and fludarabine, and two patients received an additional dose following initial disease evaluation. One patient received a 2 ^nd course of LDC prior to re-infusion. CD5.CAR T-cells expanded and persisted in all patients for up to 9 months , peaking in peripheral blood at 1-4 weeks post-infusion (Fig. 1). CD5.CAR T-cell infusions were associated with a transient reduction in peripheral T-cell counts but depletion was incomplete as circulating normal T-cells were detected in most patients over the follow-up period. No severe infections were observed. Max grade CRS and ICANS was grade 2, which occurred concurrently in one patient and promptly resolved following treatment. Three patients experienced grade 1 CRS and no other neurotoxicity events were observed. The most frequent treatment related adverse events were cytopenias which recovered to baseline within 28 days in all but 3 patients, in one of whom cytopenias extended beyond day 56. The remaining grade 3 events were primarily non-hematologic laboratory abnormalities which returned to baseline or improved during the monitoring period.

Reponses were evaluated 4-6 weeks post-infusion. Four out of nine patients (44%) achieved responses, enabling three to proceed to alloHSCT. Complete responses were obtained in two patients, one with AITL and one with peripheral TCL. Another patient with AITL achieved a mixed response followed by a second infusion of CD5.CAR T-cells and subsequently proceeded to alloHSCT. A very good partial response was achieved in a patient with HTLV-1 driven ATLL (Fig. 2). Two patients remain alive and in CR for 29 months and 24 months respectively. The remaining patients experienced stable disease (n=1) or progressive disease (n=4). Clinical responses were observed on all dose levels.

Objective responses did not correlate with cell dose or magnitude of T-cell expansion. All responses were obtained with CD5.CAR T-cell products produced with a shortened manufacturing method in which CAR T-cells were cryopreserved 3-5 days post-transduction instead of undergoing a standard 7-day expansion. Shortened manufacturing resulted in an enrichment of minimally differentiated CCR7+ CD62L+ T-cells (27-fold mean increase in CD4+, 13-fold increase in CD8+; p=0.01) and a 3.5-fold increase in CD27+ CD8+ T-cells (p=0.04) suggesting minimizing duration of ex vivo expansion increases anti-tumor function of CD5.CAR T-cells.

Overall, these results show that even in patients with multiply relapsed/resistant TCL, CD5.CAR T-cells can produce anti-tumor responses that are sufficiently durable to enable them to proceed with alloHSCT without inducing clinically significant T-cell aplasia.

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