Winfried S. Wels

Human Epidermal Growth Factor Receptor 2 (HER2) –Specific Chimeric Antigen Receptor–Modified T Cells for the Immunotherapy of HER2-Positive Sarcoma

PURPOSE The outcome for patients with metastatic or recurrent sarcoma remains poor. Adoptive therapy with tumor-directed T cells is an attractive therapeutic option but has never been evaluated in sarcoma. PATIENTS AND METHODS We conducted a phase I/II clinical study in which patients with recurrent/refractory human epidermal growth factor receptor 2 (HER2) -positive sarcoma received escalating doses (1 × 10(4)/m(2) to 1 × 10(8)/m(2)) of T cells expressing an HER2-specific chimeric antigen receptor with a CD28.ζ signaling domain (HER2-CAR T cells). RESULTS We enrolled 19 patients with HER2-positive tumors (16 osteosarcomas, one Ewing sarcoma, one primitive neuroectodermal tumor, and one desmoplastic small round cell tumor). HER2-CAR T-cell infusions were well tolerated with no dose-limiting toxicity. At dose level 3 (1 × 10(5)/m(2)) and above, we detected HER2-CAR T cells 3 hours after infusion by quantitative polymerase chain reaction in 14 of 16 patients. HER2-CAR T cells persisted for at least 6 weeks in seven of the nine evaluable patients who received greater than 1 × 10(6)/m(2) HER2-CAR T cells (P = .005). HER2-CAR T cells were detected at tumor sites of two of two patients examined. Of 17 evaluable patients, four had stable disease for 12 weeks to 14 months. Three of these patients had their tumor removed, with one showing ≥ 90% necrosis. The median overall survival of all 19 infused patients was 10.3 months (range, 5.1 to 29.1 months). CONCLUSION This first evaluation of the safety and efficacy of HER2-CAR T cells in patients with cancer shows the cells can persist for 6 weeks without evident toxicities, setting the stage for studies that combine HER2-CAR T cells with other immunomodulatory approaches to enhance their expansion and persistence.

TanCAR: A Novel Bispecific Chimeric Antigen Receptor for Cancer Immunotherapy

Targeted T cells are emerging as effective non-toxic therapies for cancer. Multiple elements, however, contribute to the overall pathogenesis of cancer through both distinct and redundant mechanisms. Hence, targeting multiple cancer-specific markers simultaneously could result in better therapeutic efficacy. We created a functional chimeric antigen receptor—the TanCAR, a novel artificial molecule that mediates bispecific activation and targeting of T cells. We demonstrate the feasibility of cumulative integration of structure and docking simulation data using computational tools to interrogate the design and predict the functionality of such a complex bispecific molecule. Our prototype TanCAR induced distinct T cell reactivity against each of two tumor restricted antigens, and produced synergistic enhancement of effector functions when both antigens were simultaneously encountered. Furthermore, the TanCAR preserved the cytolytic ability of T cells upon loss of one of the target molecules and better controlled established experimental tumors by recognition of both targets in an animal disease model. This proof-of-concept approach can be used to increase the specificity of effector cells for malignant versus normal target cells, to offset antigen escape or to allow for targeting the tumor and its microenvironment.

Expression of a CD20-specific chimeric antigen receptor enhances cytotoxic activity of NK cells and overcomes NK-resistance of lymphoma and leukemia cells

Despite the clinical success of CD20-specific antibody rituximab, malignancies of B-cell origin continue to present a major clinical challenge, in part due to an inability of the antibody to activate antibody-dependent cell-mediated cytotoxicity (ADCC) in some patients, and development of resistance in others. Expression of chimeric antigen receptors in effector cells operative in ADCC might allow to bypass insufficient activation via FcγRIII and other resistance mechanisms that limit natural killer (NK)-cell activity. Here we have generated genetically modified NK cells carrying a chimeric antigen receptor that consists of a CD20-specific scFv antibody fragment, via a flexible hinge region connected to the CD3ζ chain as a signaling moiety. As effector cells we employed continuously growing, clinically applicable human NK-92 cells. While activity of the retargeted NK-92 against CD20-negative targets remained unchanged, the gene modified NK cells displayed markedly enhanced cytotoxicity toward NK-sensitive CD20 expressing cells. Importantly, in contrast to parental NK-92, CD20-specific NK cells efficiently lysed CD20 expressing but otherwise NK-resistant established and primary lymphoma and leukemia cells, demonstrating that this strategy can overcome NK-cell resistance and might be suitable for the development of effective cell-based therapeutics for the treatment of B-cell malignancies.

Regression of Experimental Medulloblastoma following Transfer of HER2-Specific T Cells

Medulloblastoma is a common malignant brain tumor of childhood. Human epidermal growth factor receptor 2 (HER2) is expressed by 40% of medulloblastomas and is a risk factor for poor outcome with current aggressive multimodal therapy. In contrast to breast cancer, HER2 is expressed only at low levels in medulloblastomas, rendering monoclonal antibodies ineffective. We determined if T cells grafted with a HER2-specific chimeric antigen receptor (CAR; HER2-specific T cells) recognized and killed HER2-positive medulloblastomas. Ex vivo, stimulation of HER2-specific T cells with HER2-positive medulloblastomas resulted in T-cell proliferation and secretion of IFN-gamma and interleukin 2 (IL-2) in a HER2-dependent manner. HER2-specific T cells killed autologous HER2-positive primary medulloblastoma cells and medulloblastoma cell lines in cytotoxicity assays, whereas HER2-negative tumor cells were not killed. No functional difference was observed between HER2-specific T cells generated from medulloblastoma patients and healthy donors. In vivo, the adoptive transfer of HER2-specific T cells resulted in sustained regression of established medulloblastomas in an orthotopic, xenogenic severe combined immunodeficiency model. In contrast, delivery of nontransduced T cells did not change the tumor growth pattern. Adoptive transfer of HER2-specific T cells may represent a promising immunotherapeutic approach for medulloblastoma.

Tandem CAR T cells targeting HER2 and IL13Rα2 mitigate tumor antigen escape

In preclinical models of glioblastoma, antigen escape variants can lead to tumor recurrence after treatment with CAR T cells that are redirected to single tumor antigens. Given the heterogeneous expression of antigens on glioblastomas, we hypothesized that a bispecific CAR molecule would mitigate antigen escape and improve the antitumor activity of T cells. Here, we created a CAR that joins a HER2-binding scFv and an IL13Rα2-binding IL-13 mutein to make a tandem CAR exodomain (TanCAR) and a CD28.ζ endodomain. We determined that patient TanCAR T cells showed distinct binding to HER2 or IL13Rα2 and had the capability to lyse autologous glioblastoma. TanCAR T cells exhibited activation dynamics that were comparable to those of single CAR T cells upon encounter of HER2 or IL13Rα2. We observed that TanCARs engaged HER2 and IL13Rα2 simultaneously by inducing HER2-IL13Rα2 heterodimers, which promoted superadditive T cell activation when both antigens were encountered concurrently. TanCAR T cell activity was more sustained but not more exhaustible than that of T cells that coexpressed a HER2 CAR and an IL13Rα2 CAR, T cells with a unispecific CAR, or a pooled product. In a murine glioblastoma model, TanCAR T cells mitigated antigen escape, displayed enhanced antitumor efficacy, and improved animal survival. Thus, TanCAR T cells show therapeutic potential to improve glioblastoma control by coengaging HER2 and IL13Rα2 in an augmented, bivalent immune synapse that enhances T cell functionality and reduces antigen escape.

Recombinant antibody toxins specific for ErbB2 and EGF receptor inhibit the in vitro growth of human head and neck cancer cells and cause rapid tumor regression in vivo

Overexpression of the ErbB2 and epidermal growth factor receptor (EGFR) tyrosine kinases is frequently observed in squamous cell carcinomas of the head and neck, and has been correlated with shorter overall survival. By immunoblot analysis, we have found EGFR and ErbB2 expression in 6 out of 6 established head and neck cancer cell lines. Elevated EGFR protein levels were noted in 3 and elevated ErbB2 levels in 5 of them. Significant expression of EGFR and ErbB2 was also detected in 17 of 47 and 26 of 45 primary tumor samples. Due to their enhanced expression on the tumor cell surface, these receptors can be regarded as suitable targets for directed cancer therapy. We have analyzed the antitumoral activity of recombinant single‐chain antibody toxins specific for ErbB2 and EGFR against head and neck cancer cells in vitro and in vivo. The recombinant toxins consist of the variable domains of the heavy and light chains of monoclonal antibodies (MAbs) genetically fused to a truncated Pseudomonas exotoxin A (ETA). At low concentrations, the ErbB2‐specific single‐chain antibody (scFv) toxin scFv(FRP5)‐ETA and the EGFR‐specific toxins scFv(225)‐ETA and scFv(14E1)‐ETA inhibited the in vitro growth of established head and neck cancer cell lines and primary tumor cells. In a nude mouse tumor model, intratumoral injection of the antibody toxins resulted in the rapid regression of subcutaneously growing CAL 27 tumor xenografts, with scFv(FRP5)‐ETA and scFv(14E1)‐ETA treatment being most effective and leading to the cure of up to 50% of the animals. Our results suggest that EGFR and ErbB2‐specific antibody toxins may become valuable therapeutic reagents for the treatment of squamous cell carcinomas of the head and neck. Int. J. Cancer 86:269–275, 2000.

Immunotherapy for Osteosarcoma: Genetic Modification of T cells Overcomes Low Levels of Tumor Antigen Expression

Human epidermal growth factor receptor 2 (HER2) is expressed by the majority of human osteosarcomas and is a risk factor for poor outcome. Unlike breast cancer, osteosarcoma cells express HER2 at too low, a level for patients to benefit from HER2 monoclonal antibodies. We reasoned that this limitation might be overcome by genetically modifying T cells with HER2-specific chimeric antigen receptors (CARs), because even a low frequency of receptor engagement could be sufficient to induce effector cell killing of the tumor. HER2-specific T cells were generated by retroviral transduction with a HER2-specific CAR containing a CD28.zeta signaling domain. HER2-specific T cells recognized HER2-positive osteosarcoma cells as judged by their ability to proliferate, produce immunostimulatory T helper 1 cytokines, and kill HER2-positive osteosarcoma cell lines in vitro. The adoptive transfer of HER2-specific T cells caused regression of established osteosarcoma xenografts in locoregional as well as metastatic mouse models. In contrast, delivery of nontransduced (NT) T cells did not change the tumor growth pattern. Genetic modification of T cells with CARs specific for target antigens, expressed at too low a level to be effectively recognized by monoclonal antibodies, may allow immunotherapy to be more broadly applicable for human cancer therapy.

NK cells engineered to express a GD2 -specific antigen receptor display built-in ADCC-like activity against tumour cells of neuroectodermal origin.

Treatment of high‐risk neuroblastoma (NB) represents a major challenge in paediatric oncology. Alternative therapeutic strategies include antibodies targeting the disialoganglioside GD2, which is expressed at high levels on NB cells, and infusion of donor‐derived natural killer (NK) cells. To combine specific antibody‐mediated recognition of NB cells with the potent cytotoxic activity of NK cells, here we generated clonal derivatives of the clinically applicable human NK cell line NK‐92 that stably express a GD2‐specific chimeric antigen receptor (CAR) comprising an anti‐GD2 ch14.18 single chain Fv antibody fusion protein with CD3‐ζ chain as a signalling moiety. CAR expression by gene‐modified NK cells facilitated effective recognition and elimination of established GD2 expressing NB cells, which were resistant to parental NK‐92. In the case of intrinsically NK‐sensitive NB cell lines, we observed markedly increased cell killing activity of retargeted NK‐92 cells. Enhanced cell killing was strictly dependent on specific recognition of the target antigen and could be blocked by GD2‐specific antibody or anti‐idiotypic antibody occupying the CAR’s cell recognition domain. Importantly, strongly enhanced cytotoxicity of the GD2‐specific NK cells was also found against primary NB cells and GD2 expressing tumour cells of other origins, demonstrating the potential clinical utility of the retargeted effector cells.

Selective inhibition of tumor growth by clonal NK cells expressing an ErbB2/HER2-specific chimeric antigen receptor.

Natural killer (NK) cells are an important effector cell type for adoptive cancer immunotherapy. Similar to T cells, NK cells can be modified to express chimeric antigen receptors (CARs) to enhance antitumor activity, but experience with CAR-engineered NK cells and their clinical development is still limited. Here, we redirected continuously expanding and clinically usable established human NK-92 cells to the tumor-associated ErbB2 (HER2) antigen. Following GMP-compliant procedures, we generated a stable clonal cell line expressing a humanized CAR based on ErbB2-specific antibody FRP5 harboring CD28 and CD3ζ signaling domains (CAR 5.28.z). These NK-92/5.28.z cells efficiently lysed ErbB2-expressing tumor cells in vitro and exhibited serial target cell killing. Specific recognition of tumor cells and antitumor activity were retained in vivo, resulting in selective enrichment of NK-92/5.28.z cells in orthotopic breast carcinoma xenografts, and reduction of pulmonary metastasis in a renal cell carcinoma model, respectively. γ-irradiation as a potential safety measure for clinical application prevented NK cell replication, while antitumor activity was preserved. Our data demonstrate that it is feasible to engineer CAR-expressing NK cells as a clonal, molecularly and functionally well-defined and continuously expandable cell therapeutic agent, and suggest NK-92/5.28.z cells as a promising candidate for use in adoptive cancer immunotherapy.

Advantages and applications of CAR-expressing natural killer cells

In contrast to donor T cells, natural killer (NK) cells are known to mediate anti-cancer effects without the risk of inducing graft-versus-host disease (GvHD). In order to improve cytotoxicity against resistant cancer cells, auspicious efforts have been made with chimeric antigen receptor (CAR) expressing T- and NK cells. These CAR-modified cells express antigen receptors against tumor-associated surface antigens, thus redirecting the effector cells and enhancing tumor-specific immunosurveillance. However, many cancer antigens are also expressed on healthy tissues, potentially leading to off tumor/on target toxicity by CAR-engineered cells. In order to control such potentially severe side effects, the insertion of suicide genes into CAR-modified effectors can provide a means for efficient depletion of these cells. While CAR-expressing T cells have entered successfully clinical trials, experience with CAR-engineered NK cells is mainly restricted to pre-clinical investigations and predominantly to NK cell lines. In this review we summarize the data on CAR expressing NK cells focusing on the possible advantage using these short-lived effector cells and discuss the necessity of suicide switches. Furthermore, we address the compliance of such modified NK cells with regulatory requirements as a new field in cellular immunotherapy.