Immune Reconstitution Following Infusion of Autologous Blinatumomab Expanded T-Cells (BET) in CD20+ Indolent Non-Hodgkin Lymphomas and Chronic Lymphocytic Leukemia Receiving Front-Line Treatment with Fludarabine-Cyclophosphamide-Rituximab or Bendamustine-Rituximab

Introduction. Fludarabine or Bendamustine-based chemo-immunotherapy regimens are associated with severe immunosuppression and prolonged lymphopenia that worsens the immune dysfunctions already present at diagnosis in several B-cell indolent non-Hodgkin lymphomas (iNHL) and chronic lymphocytic leukemia (CLL) patients (pts). Blinatumomab-expanded T cells (BET) are autologous polyclonal activated T cells expanded in vitro from the peripheral blood (PB) of CLL/iNHL patients under GMP-compliant conditions (Golay et al., J. Immunol. 2014). With the use of blinatumomab and rhIL-2, the massive in vitro polyclonal T-cell expansion and activation is coupled with B-cell depletion. In the present study we conducted a single-center phase I trial to evaluate the feasibility, toxicity and immunological effects of BET infusion after first-line treatment of iNHL/CLL with either fludarabine-cyclophosphamide-rituximab (FCR) or bendamustine-rituximab (BR). The study is registered with access number NCT03823365.

Methods. Adult patients with untreated CLL/iNHL in need of first-line treatment with FCR or BR and absolute lymphocyte count >800/mmc were eligible for the study. BET cells were produced from up to 48 mL of PB obtained before chemotherapy and infused after last chemotherapy cycle. Immune reconstitution parameters, including T cell subpopulation (CD4/CD8, T regs, Th1/2/17, naïve, central and effector memory), NK and B cell counts, were assessed at baseline (before chemotherapy), before BET infusion and after 1, 3, 6, 9 and 12 months from infusion (Figure 1A). A dose escalation was conducted to assess toxicity and efficiency of BET production. In the expansion cohort pts were infused with the whole cell product.

Results. Fifteen patients were enrolled in the study, 4 pts with iNHL and 11 with CLL. Median age was 64 years (range 52-79) and 80% were male. Ten pts received BR (67%) and 5 FCR (33%). All patients responded to chemotherapy and received a median of 9.5x10⁹ BET cells. Six pts were treated in the dose escalation phase with a dose of 3 to 12x10⁹ cells. Nine pts received BET in the expansion phase and received 4.4 to 15.9x10⁹ cells. BET infusion was well tolerated, and no untoward toxicity was reported. One patient died due to COVID19 infection before month 3 assessment. After infusion, a rapid increase of polyclonal T-cells was observed at month 1 and persisted until month 6 (Figure 1B). From month 9 a further increase of T-cell count was observed. A more prominent expansion of CD8+ cells was observed at all time points. At month 1 after infusion, a median of 399 x10⁶/L CD3+ cells (range 159-1026), 116 x10⁶/L CD4+ cells (range 30-333) and 236 x10⁶/L CD8+ cells (range 92-843) were observed. At month 3 after infusion, median CD3+ cells were 414 x10⁶/L (range 131-1148), while CD4+ and CD8+ cells were 115 x10⁶/L (range 34-269) and 226 x10⁶/L (range 48- 986) respectively. Analysis of the T-cell subpopulation showed an expansion of central memory T-cells that tended to persist over time even with increasing expansion of naïve T-cells. Percentage of T-regulatory cells was stable across the study assessments. A negative flow-cytometry minimal residual disease in PB was achieved by all pts after treatment and maintained through the study. A polyclonal B-cell reconstitution was observed in 4/14 (29%) pts at month 6, 10/12 (83%) pts at month 9 and in 12/12 (100%) pts at month 12.

Conclusions. BET cells can be efficiently expanded from PB of leukemic B-cell iNHL/CLL pts and safely administered after BR or FCR chemotherapy. After infusion, a polyclonal T-cell recovery is rapidly achieved after one month and maintained over time. Polyclonal B-cell reconstitution is achieved after 6 months without emergence of clonal B-cells.

Gritti:Roche: Other: Advisory Board (2021) Training activity (2020), Support for attending meetings (2021); Sandoz: Other: Support for attending meetings (2021); Takeda: Other: Advisory Board (2020, 2021, 2022), Training activity (2020, 2022), Individual scientific consultancy (2021-ongoing); Kite-Gilead: Other: Advisory Board (2020); Italfarmaco: Other: Advisory Board (2021); Clinigen: Other: Training activity (2021); Ideogen: Other: Advisory Board (2022), Training activity (2022); Genmab: Other: Advisory Board (2022); Beigene: Other: Training activity (2022); IQVIA: Other: Advisory Board (2020); Incyte: Other: Training activity (2022). Lussana:Amgen: Honoraria; Astellas Pharma: Honoraria; Incyte: Honoraria; AbbVie: Consultancy; Janssen Oncology: Honoraria; Pfizer: Honoraria. Barbui:Incyte: Honoraria; Takeda: Honoraria; EUSA Pharma: Honoraria. Rambaldi:Janssen: Honoraria; Celgene-BMS: Honoraria; Kite-Gilead: Honoraria; Jazz: Honoraria; Roche: Honoraria; Incyte: Honoraria; Omeros: Honoraria; Novartis: Honoraria; ABBVIE: Honoraria; Astellas: Honoraria; Pfizer: Honoraria; Amgen: Honoraria.