A New Promising Third Generation CAR-CD30 T-Cell Therapy for CD30+ Lymphoma

Prognosis of a significant proportion of patients with chemotherapy-refractory or multiply-relapsed CD30+ Non-Hodgkin's Lymphoma (NHL) or Hodgkin lymphoma (HL) still remain poor. Targeting CD30 with monoclonal antibodies in HL and anaplastic large cell lymphoma was shown to induce remarkable clinical activity; however, occurrence of adverse events (mainly neuropathy) may result into treatment discontinuation in many patients. Immunotherapeutic approaches targeting CD30 by chimeric antigen receptor (CAR) has been demonstrated to be of value in two independent clinical trials, although clinical benefit was sub-optimal. We designed a new CAR construct characterized by an anti-CD30 single-chain variable-fragment cassette (AC10), linked to CD3ζ by the signaling domains of two costimulatory molecules, namely either CD28.4-1BB or CD28.OX40. The inducible Caspase-9 (iCasp9) safety switch was included in both constructs with the goal of promptly controlling undue toxicity. As a selectable marker, we added in frame the CD34 antigen. The in vitro anti-tumor efficacy was evaluated by using either the NHL cell line: Karpas299, or the HL cell lines: L428, in both short-term cytotoxic assay (51Cr release assays) and long-term co-cultures for 6 days. Supernatant from co-culture experiments was analyzed by Elisa. We assessed the antitumor effect of CAR.CD30 T cells in a in vivo NSG mouse model engrafted i.v. with lymphoma FF-luciferase cell lines Karpas299 or L428, and monitored tumor growth by IVIS Imaging system. For tumor re-challenging, mice of the NHL model surviving until day +140, were i.v. infused with 0.2x106 Karpas299 cells, and subsequently followed for additional 110 days. Persistence of CAR.CD30 T cells was evaluated, together with a deep characterization of memory profile of T cells.

Independently from the costimulatory domains CD28.OX40 or CD28.4-1BB, the generated retroviral vectors showed similar transduction efficiency of T cells (86.5±5.1% and 79.3±5.3%, respectively). Nevertheless, CD28.OX40 costimulatory domains was associated with more stable expression of the CAR over time, during extensive in vitro culture (84.72±5.30% vs 63.98±11.51% CD28.4-1BB CAR T cells at 30 days after transduction; p=0.002). For both CAR constructs, we did not observe any significant difference in the suicide gene iCasp9 activity, both in vitro and in vivo. In short-term cytotoxic assay, both CAR.CD30 T cells significantly and specifically lysed CD30+ NHL and HL tumor cell lines. In long-term co-culture, CD28.OX40 showed a superior anti-lymphoma in vitro activity as compared to CD28.41BB T cells, when challenged at very high tumor/effector ratio (8:1) (for Karpas 299; p=0.03). Moreover, the antigen stimulation was associated to higher levels of Th1 cytokine production, with CD28.OX40 T cells secreting a significantly higher amount of IFNγ, IL2 and TNFα as compared to CD28.41BB T cells (p= 0.040; p=0.008; p=0.02; respectively).

Bioluminescence in HL (L428) tumor-bearing mice, treated with NT T cells, rapidly increased up to 5 log in less than 50 days and mice either died or were sacrificed due to morbidity. The best outcome was observed in mice treated with CD28.OX40, as three out of five mice were still alive at the experimental end-point of day+165, as compared with mice treated with CD28.4-1BB (60% vs 0%, p=0.0021).

In NHL (Karpas 299) mouse models, CD28.OX40 had an extensive anti-tumor control superior to that of CD28.41BB T cells, leading to a significant reduction of tumor bioluminescence at day 45 (3.32x10 vs 2.29x10, p=0.04). The median survival of mice treated with NT and CD28.4-1BB CAR T cells was 45.5 and 58 days respectively, but undetermined for mice treated with CD28.OX40 CAR T cells (p=0.0002). After 140 days, cured mice were re-challenged with Karpas 299; mice were followed for other 100 days. Bioluminescence analysis showed rapid progression of the tumor in the control mice cohort, as well as in CD28.4-1BB treated mice. In contrast, in CD28.OX40 treated mice, at day+240 days, 4 out of 6 mice were tumor-free, resulting into a statistically significant survival benefit (p=0.0014). Only in mice treated with 28.OX40 T cells, we observed a long-lasting persistence of circulating CAR-T cells up to day +221. In summary, we have developed a novel CAR.CD30 construct displaying features that make it a particularly suitable candidate for a clinical trial in patients suffering from CD30+ tumors.